DISEASE TRANSMISSION IN HEALTHCARE SETTINGS

Modes of transmission for healthcare workers and patients in healthcare settings include direct contact, indirect contact with contaminated surfaces or objects (fomites), droplets, and bloodborne and airborne routes.^7,8 Disease may occur when a sufficient level of a given pathogen is present to result in an infectious dose.⁷ In hospitals, 1 in 25 patients are impacted by at least one hospital-acquired infection (HAI).⁹ Many HAIs are caused by antibiotic-resistant micro-organisms, often referred to as “superbugs,” and may lead to sepsis or death.¹⁰ In the dental setting, confirmed diagnoses of acquired infections among patients and/or dental healthcare personnel have resulted from water in contaminated dental unit waterlines, failure to adhere to the requirements of the Bloodborne Pathogens Standard, and incorrect/inadequate reprocessing of contaminated instruments.^7,8,11 Other risks include contaminated clinical contact surfaces, direct contact, and airborne transmission. 

AIRBORNE TRANSMISSION

Examples of micro-organisms with airborne transmission include the measles virus and Mycobacterium tuberculosis, which are both highly infectious, and Candida auris.^12-15 Airborne spread of SARS was confirmed more than a decade ago.¹⁶ In air sampling studies of hospital air where infected patients were staying, PCR was used to detect micro-organisms.¹⁷ Collectively in these studies, sampled air had contained the varicella-zoster virus, measles virus, M tuberculosis, influenza viruses, respiratory synctial virus, rhinovirus, adenovirus, Mycoplasma pneumoniae, and other micro-organisms. For many, the particles were <5 μm in size. There was also evidence of airborne transmission during the SARS-CoV outbreak.¹⁸ For some micro-organisms, while one mode of transmission may dominate, other modes of transmission also occur: for example, MRSA (which can be transmitted by direct contact and indirect contact with fomites), varicella-zoster, and Pseudomonas aeruginosa.^19-21 The latest was SARS-CoV-2, which is now generally accepted to mainly involve airborne transmission, with far fewer cases associated with close-contact droplet transmission or contaminated surfaces. 

Particle Size and Behavior

Different understandings exist with respect to airborne transmission. Aerosols contain particles ≤50 μm in a gas—in the current context, in air. Infectious aerosols contain pathogens within particles in the air. Larger particles are generally believed to behave ballistically and to settle out rapidly in close proximity. This includes spatter, which contains particles >50 μm and droplets >20 μm in aerosols.^16,22 However, in a study on respiratory exhalation, it was found that droplets between 60 and 100 μm were carried farther than 6 m away.²³ In addition, when droplets rapidly dehydrate in the air, this creates airborne droplet nuclei, which are largely ≤5 μm but may be as large as 10 μm.¹⁶ Small particles can move with airflow, remain airborne longer, and travel farther than larger particles.²⁴ The time it takes for particles to settle varies based on particle size, airflow, and the height of the area in which settling occurs. Studies use the diameter of unit density spheres to assess settling time that involves the same velocity as for the actual particle being investigated (Figure 1).

Furthermore, while particles passing in turbulent air close to a horizontal surface can settle, other particles will continue to be disturbed and remain airborne for long periods of time.²⁴ In addition, it is possible for particles settled on surfaces to become airborne. Whether or not this occurs depends on particle size, adhesion to a surface, and the energy and airflow reaching the space.²⁴ A recent report noted that micro-organisms on floors in hospital settings could become resuspended into the air, such as when walked on, with a potential for transmission and contamination of surfaces.²⁵ The report also cited earlier studies showing the contamination of floors with Clostridioides difficile, vancomycin-resistant enterococci, and MRSA. Particle size also determines how deep a pathogen can reach in the respiratory tract, with smaller aerosol particles reaching deeper into the lungs. In studies analyzing cough and breath aerosols, M tuberculosis, P aeruginosa, and numerous viruses were found in particles <5 μm in size.¹⁷ Particles <10 μm readily reach below the glottis in the larynx; those <5 μm are readily inhaled into the lower respiratory tract^16,17,26 (Figure 2).

INFECTION CONTROL PROTOCOLS AND GUIDANCE IN THE DENTAL SETTING

The CDC provides recommendations with standard precautions and additional protocols for infection control. CDC guidance for healthcare settings during COVID-19 includes (but is not limited to) triaging patients, social distancing, source control, changes to PPE for protection, and the recommendation to select an EPA-registered hospital-level disinfectant on EPA List N.²⁷ In the dental setting, key guidance includes the use of high-volume evacuation, rubber dams (when possible), and specific recommendations for PPE during aerosol-generating procedures. Other devices, such as extraoral suction, can also mitigate aerosolization through capture while varying in power level, dimensions, configuration, noise level, and how the captured aerosol is then handled.²⁸ A layered approach has been recommended. This approach includes using ventilation and considering the use of adjunctive devices, specifically high-efficiency particulate air (HEPA) filtration and ultraviolet germicidal irradiation (UVGI).²⁹ HEPA filtration and upper-room UVGI¹³ work continuously while rooms are occupied, providing ongoing adjunctive infection control. Newer Food and Drug Administration (FDA)-cleared medical devices are also available in the dental setting, which we will discuss later in this article. 

Of note, ozone generator air purifiers are not recommended. While ozone is a germicide at high levels, it is also toxic. OSHA’s permissible level of ozone is an airborne exposure limit of 0.10 ppm (0.2 mg/m³) for an 8-hour work shift (a day of exposure). The National Institute of Occupational Safety and Health recommends an upper limit of 0.10 ppm, not to be exceeded at any time.^30,31 The California Air Resource Board (CARB), which oversees air pollution control efforts in California to reach and maintain health-based air quality standards, and other governmental organizations advise against the use of such ozone generators in spaces occupied by people or animals.^32,33 Based on the evidence, ozone concentrations within the permissible levels are ineffective in removing micro-organisms, as well as many odor-causing chemicals, and would need to be substantially higher to kill airborne micro-organisms.³¹ 

Air Exchanges and Ventilation

“Air changes per hour” (ACH) denotes how many times the air within a defined space is replaced, provided the air is well-mixed. The CDC defined a minimum of 6 ACH as criteria for an efficient ventilation system in 2003, while for transmission-based precautions, it states that at least 12 ACH should be ensured.³⁴ The minimum of 6 ACH is being reviewed. As reported by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the assumption in the past was that air was ideally mixed and no obstacles to airflow were present, such as a dental chair. It was also noted that it was based on an absence of “re-contamination of the room by the exhaust air.”³⁵ The objective of increasing room ventilation is to supply more clean air, thereby reducing the concentration of contaminants with the goal of keeping this below the threshold that could cause injury/disease. It has also been shown that a relative humidity below 40% can increase the survival rate of some airborne micro-organisms and increase their transmission.³⁵ 

One method to assess ventilation is through the use of carbon dioxide monitors. These determine the concentration of carbon dioxide in an area, with readings below 800 ppm recognized as a target benchmark for good ventilation. Periodic assessment of the level of carbon dioxide in a defined space provides information on the need (or not) to adjust ventilation. It can provide an early warning system when used appropriately.³⁶

In accordance with the CDC guidance, options that include opening windows—even just slightly, when possible—aid ventilation. Fans can be used to increase the flow of outside air into the area. Another option is to consult an HVAC specialist about further opening the HVAC’s outdoor air dampers and to help ensure that the HVAC is working properly and is adjusted for optimal airflow.²⁷ Additional methods of adjusting ventilation can be found on the CDC website. 

Minimum Efficiency Reporting Value (MERV) ratings are provided for filters.³⁷ The higher the MERV rating, the more efficient the filter. For example, the particle size efficiency of a MERV 14 filter is 76% to 84% for 0.3-μm to 1.0-μm particles and 90% or greater for 1.0-μm to 3.0-μm particles. A MERV 12 filter, on the other hand, has a particle size efficiency of 80% to 89.9% for 1-μm to 3-μm particles and 90% or greater for 3-μm to 10-μm particles. Currently, ASHRAE recommends a filter with a MERV 13 rating (at least 85% efficient at capturing particles in the 1- to 3-µm size range) for HVAC systems, while noting that a MERV 14 or better is preferred.³⁸ It also notes that the given HVAC system must be taken into account and that it may not be possible to accommodate a MERV 13 filter. Higher efficiency typically increases the pressure drop, paradoxically, in turn, potentially reducing the airflow through the system and/or increasing energy use.³⁷   

HEPA Filtration (Adjunctive)

The CDC recommends that consideration be given to using portable HEPA filters to decontaminate air, preferably those with powered fans.²⁷ HEPA filters can theoretically capture at least 99.97% of 0.3-μm particles, the most penetrating particle size and, therefore, the most difficult to capture compared to both larger and smaller particles.^39,40 When selecting a HEPA filter, one with a high clean air delivery rate (CADR) is recommended. This defines the cubic feet of air per minute that can be handled by the filter. The device should be positioned so that air is sucked into it directionally away from patients and the clinical team, avoiding sucking contaminated air over room occupants. The room dimensions and capacity must be considered in determining the required capacity of a HEPA filter or whether more than one HEPA filter will be required. 

While some devices on the market may be advertised as “HEPA-Rx,” “true HEPA” or “medical-grade HEPA” filters, these are not recognized HEPA categories.

NEWER ADJUNCTIVE TECHNOLOGIES

Many newer technologies and devices are now being marketed as adjunct devices for air decontamination. These variously offer the capture of micro-organisms and their destruction in the device and/or in the air. There are several considerations to be made before deciding whether to purchase these. First and foremost, do you need one, does it work, and is it safe? Is the device FDA-cleared or being marketed during COVID-19 under the FDA Enforcement Policy for Sterilizers, Disinfectant Devices, and Air Purifiers during the COVID-19 public health emergency or neither? Is it CARB-certified (which is needed in California)? Other factors include whether there are independent studies demonstrating efficacy against micro-organisms. Another consideration is the availability of information from studies in healthcare settings supporting efficacy. Does the device operate episodically or continuously, including safely when the room/area is occupied? Other considerations beyond the scope of this article include specifications, size, capacity, performance, ease-of-use, cost, maintenance, and ongoing support.  

ActivePure Medical Guardian: The ActivePure Medical Guardian is cleared by the FDA as a Class II Medical Device and is CARB-certified. This device is portable, and the system is designed to be used in rooms of up to 3,000 ft³. The technology is an advanced form of the one developed and used in the NASA Space Program and included in the Space Foundation Technology Hall of Fame. It offers continuous air and surface decontamination and works in 2 phases using 3 technologies. The first phase utilizes a patented process that includes a UV light source in the device and titanium dioxide as a photocatalyst that is used to produce gaseous hydrogen peroxide and other oxidizers. These then exit the device and enter the air. The oxidizers interact with and disrupt bacterial and fungal cell membranes, as well as the outer shell of viruses. This leads to microbial kill. During phase 2, air is sucked into the device, along with contaminants and oxidizers present in that air. The contaminants are then ionized to become negatively charged, trapped by a positively charged filter media, and filtered by HEPA filters. In addition, the oxidizers present kill the trapped and filtered micro-organisms. 

Testing Results: Studies on the technology have been conducted in laboratory and healthcare settings. Tests resulting in FDA Class II Medical Device Clearance showed a log reduction of 5 (99.999%) for airborne RNA MS2 bacteriophages in 30 minutes. 

At the University of Texas Medical Branch, an independent laboratory study on the first phase of ActivePure, using only the ActivePure technology (no filters or ionizers), was conducted using SARS-CoV-2.⁴¹ The test protocol was designed to deliver 29 ft³ per minute of air movement (the lowest setting). Within 3 minutes, a ≥2.87 to ≥3.38 log reduction was found, which equates to a ≥99.87% to ≥99.96% reduction in the concentration of SARS-CoV-2. It was noted that the actual reduction may have been 99.99% or greater since the level of detection was reached. 

In a second independent study, the efficacy of the ActivePure Medical Guardian against aerosolized vegetative bacteria, viruses, and spores was evaluated using a sealed bioaerosol chamber in a laboratory at approximately 70.6°F and with 36% relative humidity, and inside the chamber at 75°F and 50%, respectively.⁴¹ The bioaerosol was created using a nebulizer filled with approximately 50 mL of biological stock and operated at 50 psi for 20 or 25 minutes (organism dependent). Aerosol samples were collected using 2 impingers and collected at baseline and 15-minute intervals for 90 minutes. The test micro-organisms were Staphylococcus epidermidis, Erwinia herbicola, RNA MS2 and DNA Phi X174 bacteriophages, Aspergillus niger, and Bacillus subtilis. These are proxy/surrogate micro-organisms for known pathogens, among them, respectively, Staphylococcus aureus; Yersinia pestis (black plague); influenza virus and norovirus; HCV, HCB, and HIV; Stachybotrys chartarumand (a toxic black mold); and Bacillus anthracis (anthrax) (Table 1).  

Three test trials were conducted as well as a control trial. The results showed an overall average net log reduction of 4.8 ±0.74, representing a greater than 99.99% reduction. For S epidermidis, less than 1.2% of the aerosolized bacteria were viable at 15 minutes. At 60 minutes, the average net log reduction was 5.95 ±0.34, equivalent to an almost 99.9999% reduction. For E herbicola, the average reduction at 15 minutes was >99.99%, and by 75 minutes, an average net log reduction of 5.36 ±0.37 was obtained. For the MS2 bacteriophage, in 15 minutes, on average, 99.999% was removed, and by 60 minutes, an average log reduction of 5.58 ±0.43 was observed. Testing with the Phi X174 bacteriophage produced an average net log reduction of 4.05 ±0.27 at 60 minutes. For both bacteriophages, reductions reached the limit of detection. For Bacillus subtilis, a 98.91% reduction in spores was found at 15 minutes, and by 90 minutes, a net log reduction of 4.23 ±0.31. was observed. Lastly, the 15-minute reduction for A niger was 99.71%, and by 60 minutes, an average net log reduction of 4.12 ±0.10 was found (Figure 3). At the 60-minute sampling point, the log reductions compared to the samples obtained ranged from a log 4 reduction (99.99% reduction) to a log 6 reduction (99.9999% reduction)⁴¹ (Figure 3).

Brondell Pro Sanitizing Air Purifier with AG+ Technology: This device was FDA-cleared as a medical device in January 2021 and is CARB-certified. It contains a pre-filter, proprietary HEPA filter, and nanocrystalline filter. The HEPA filter is described as antiviral; the nanocrystalline filter removes gases and odors; and a UV light is used inside the device to help sanitize the filter surfaces, the unit, and the air within it. A plasma generator generates negative ions that leave the device together with clean air and are designed to destroy micro-organisms in the room’s air. In one independent laboratory test using a test chamber, a 99.9% reduction in the H1N1 and H3N2 influenza viruses was found at 1 hour. In a second independent laboratory test, a 99.9% reduction in SARS-CoV-2 at 15 minutes was found. At the time of writing, no studies in healthcare settings were found. 

Molekule Air Pro RX air purifier: This is an FDA-cleared medical device and CARB-certified. It contains a pre-filter and a photoelectrochemical oxidation (PECO) filter. The fibers of the PECO filter are coated with a nanocatalyst that is activated by UV light and produces hydroxyl radicals in the closed chamber to destroy micro-organisms trapped in the PECO-filter fibers. In an independent laboratory test using 4 filter samples per time point, the company’s PECO filters were evaluated for reductions in RNA virus MS2, a proxy virus for SARS-CoV-2.⁴² At 1 hour, a 99.95% reduction was observed, and at 24 hours, a 99.9994% reduction was observed.  

Radic8: Radic8 devices were first developed in South Korea during the SARS outbreak and are used extensively there. This air purifier has 2 main phases.⁴³ After the air is sucked in, it passes through a pre-filter, a HEPA filter, and an activated carbon filter. UV-C light and titanium dioxide are used to produce hydroxyl radicals—these remain in the closed chamber and kill micro-organisms there. Treated air is then released into the room. The device has a “single-pass” 99.9999% kill rate against viruses similar to SARS-CoV-2, meaning that this kill rate is achieved based on air going through the device once. This technology is proven in lab testing to kill SARS-CoV-2, bacteria, and fungi in aerosols. While not an FDA-cleared medical device, the Radic8 is currently marketed under the FDA’s Enforcement Policy for Sterilizers, Disinfectant Devices, and Air Purifiers During the Coronavirus Disease 2019 (COVID-19) Public Health Emergency.  

CONCLUSION

Collectively, emerging and re-emerging diseases have resulted in a greater focus on infection control and, periodically, in changes to infection control guidance and practices. Of particular concern, we have now entered what is being referred to as the post-antibiotic era in which our ability to combat many infectious diseases is compromised by decreasing the availability of effective antibiotics. Our understanding of airborne transmission has also come into sharper focus, and during COVID-19, a layered approach has been recommended, including ventilation, as well as to consider HEPA filtration and UVGI. Numerous new types of adjunctive devices are on the market. When looking at newer devices, if considering one, a careful review and due diligence are needed to determine their efficacy, safety, and applicability.

REFERENCES

1. Gaynes R. The discovery of penicillin—new insights after more than 75 years of clinical use. Emerg Infect Dis. 2017;23(5):849–53. doi:10.3201/eid2305.161556

2. Centers for Disease Control and Prevention. Vaccine recommendations and guidelines of the ACIP. Updated July 16, 2013. Available at: https://www.cdc.gov/vaccines/hcp/acip-recs/index.html

3. Andre FE, Booy R, Bock HL, et al. Vaccination greatly reduces disease, disability, death and inequity worldwide. Bull World Health Organ. 2008;86(2):140–6. doi:10.2471/blt.07.040089

4. Centers for Disease Control and Prevention. Fact sheet: Multidrug-resistant tuberculosis (MDR TB). Updated May 4, 2016. Available
at: https://www.cdc.gov/tb/publications/
factsheets/drtb/mdrtb.htm 

5. Phadke VK, Bednarczyk RA, Salmon DA, et al. Association between vaccine refusal and vaccine-preventable diseases in the United States: a review of measles and pertussis. doi:10.1001/jama.2016.1353

6. World Health Organization. Zoonoses. Updated July 29, 2020. Available at: https://www.who.int/news-room/fact-sheets/detail/zoonoses 

7. Kohn WG, Collins AS, Cleveland JL, et al; Centers for Disease Control and Prevention (CDC). Guidelines for infection control in dental health-care settings–2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.

8. Laheij AM, Kistler JO, Belibasakis GN, et al; European Oral Microbiology Workshop (EOMW) 2011. Healthcare-associated viral and bacterial infections in dentistry. J Oral Microbiol. 2012;4. doi:10.3402/jom.v4i0.17659 

9. Centers for Disease Control and Prevention. Healthcare-associated infections (HAIs). Updated December 14, 2017. Available at: https://www.cdc.gov/winnablebattles/report/HAIs.html

10. Centers for Disease Control and Prevention. Winnable battles: healthcare-associated infections (HAIs). Updated December 14, 2017. Available at: https://www.cdc.gov/
winnablebattles/report/HAIs.html 

11. United States Department of Labor: Occupational Safety and Health Administration. OSHA standards: 1910.1030-Bloodborne Pathogens. Section (d)(4)(iv). Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1030

12. Hotez P. America and Europe’s new normal: the return of vaccine-preventable diseases. Pediatr Res. 2019;85(7):912-4. doi:10.1038/s41390-019-0354-3

13. Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Environmental control for tuberculosis: basic upper-room ultraviolet germicidal irradiation guidelines for healthcare settings. March 2009. Available at: https://www.cdc.gov/niosh/docs/2009-105/default.html 

14. Centers for Disease Control and Prevention. Candida auris. Updated July 22, 2021. Available at: https://www.cdc.gov/fungal/candida-auris/

15. Centers for Disease Control and Prevention. Legionella (Legionnaires’ disease and pontiac fever). Updated March 25, 2021. Available at: https://www.cdc.gov/legionella/about/causes-transmission.html

16. Tellier R, Li Y, Cowling BJ, et al. Recognition of aerosol transmission of infectious agents: a commentary. BMC Infect Dis. 2019;19:101. doi:10.1186/s12879-019-3707-y

17. Fennelly KP. Particle sizes of infectious aerosols: implications for infection control. Lancet Respir Med. 2020;8(9):914-924. doi:10.1016/S2213-2600(20)30323-4 

18. Yu IT, Li Y, Wong TW, et al. Evidence of airborne transmission of the severe acute respiratory syndrome virus. N Engl J Med. 2004;350(17):1731-9. doi:10.1056/NEJMoa032867

19. Centers for Disease Control and Prevention. Methicillin-resistant Staphylococcus aureus (MRSA). Updated June 26, 2019. Available at: https://www.cdc.gov/mrsa/community/index.html 

20. New York State Department of Health. Chickenpox. Varicella-zoster virus. Updated January 2014. Available at: https://www.health.ny.gov/diseases/communicable/chickenpox/fact_sheet.htm

21. Centers for Disease Control and Prevention. Pseudomonas aeruginosa in Healthcare Settings. Updated November 13, 2019. Available at: https://www.cdc.gov/hai/organisms/
pseudomonas.html 

22. Harrel SK, Molinari J. Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc. 2004;135(4):429-37. doi:10.14219/jada.archive.2004.0207

23. Xie X, Li Y, Chwang AT, et al. How far droplets can move in indoor environments—revisiting the Wells evaporation-falling curve. Indoor Air. 2007;17(3):211-25. doi:10.1111/j.1600-0668.2007.00469.x

24. Barron P. Centers for Disease Control and Prevention. Generation and behavior of airborne particles (aerosols). Available at: https://www.cdc.gov/niosh/topics/aerosols/pdfs/
Aerosol_101.pdf 

25. Teska P. Pathogens underfoot can floor patients, health care workers. Infection Control Today. March 28, 2021. Available at: https://www.infectioncontroltoday.com/view/pathogens-underfoot-can-floor-patients-health-care-workers 

26. Siegel JD, Rhinehart E, Jackson M, et al; Health Care Infection Control Practices Advisory Committee. 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Health Care Settings. Am J Infect Control. 2007;35(10 Suppl 2):S65-164. doi:10.1016/j.ajic.2007.10.007

27. Centers for Disease Control and Prevention. COVID-19: Guidance for dental settings. Updated December 4, 2020. Available at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/dental-settings.html 

28. American Academy of Oral and Maxillofacial Surgeons. Intraoral vs. extraoral suction devices. A review of the effectiveness of equipment on capturing aerosols. June 2, 2020. Available at: https://www.aaoms.org/docs/COVID-19/
Intraoral_vs_Extraoral_Suction_Devices.pdf 

29. Centers for Disease Control and Prevention. Ventilation in buildings. Updated June 2, 2021. Available at: https://www.cdc.gov/coronavirus/2019-ncov/community/
ventilation.html

30. United States Department of Labor: Occupational Safety and Health Administration. Standard 1910.1000 – Air Contaminants. Updated March 26, 2015. Available at: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000

31. Environmental Protection Agency. Indoor Air Quality (IAQ): Ozone generators that are sold as air cleaners. Available at: https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners 

32. The California Air Resources Board. About the California Air Resources Board. Available at: https://ww2.arb.ca.gov/about 

33. California Air Resources Board. Hazardous ozone-generating air purifiers. Available at: https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-products/hazardous-ozone-generating-air-purifiers 

34. Centers for Disease Control and Prevention. Infection control: Isolation precautions. Updated July 22, 2019. Available at: https://www.cdc.gov/infectioncontrol/guidelines/isolation/

35. The American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASHRAE Epidemic Task Force: Dental Facilities. Updated April 21, 2021. Available at: https://www.ashrae.org/file%20library/technical%20resources/covid-19/ashrae-dental-c19-
guidance.pdf  

36. National Collaborating Centre for Environmental Health. Indoor CO2 sensors for COVID-19 risk mitigation: current guidance and limitations. Published May 2021. Available at:
https://ncceh.ca/sites/default/files/FINAL%20-%20Using%20Indoor%20CO2%20Sensors%20for%20COVID%20MAY%2017%202021.pdf

37. Environmental Protection Agency. Indoor Air Quality (IAQ). What is a HEPA filter? Available at: https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter-1

38. The American Society of Heating, Refrigerating and Air-Conditioning Engineers. Filtration and disinfection FAQ. Available at: https://www.ashrae.org/technical-resources/filtration-and-disinfection-faq 

39. ASHE. Air filtration. Updated 2014. Available at: https://www.ashe.org/compliance/ec_02_05_01/01/airfiltration

40. Environmental Protection Agency. Indoor Air Quality (IAQ). What is a HEPA filter? Available at: https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter-1

41. ActivePure Medical Dossier. Data on file.

42. Balarashti J, Conley Z. Kill kinetics of catalytic filters used in Molekule® Air Pro RX device against MS2 bacteriophage. Aerosol Research and Engineering Laboratories. 

43. Radic8. VK 401. radic8.com/products/vk401.

ABOUT THE AUTHOR

Dr. Collins graduated as a general dentist from the University of Glasgow in Scotland and holds an MBA and an MA from Boston University. She is a published author and international speaker on topics including infection control and OSHA. She is a consultant; an editor for Dental World; a trainer; and a CE contributor, editor, and peer reviewer. She is the ADA representative to the Association for the Advancement of Medical Instrumentation (AAMI), Chicago Dental Society, the Organization for Safety, Asepsis and Prevention (OSAP), a participant in Standards working groups and a Fellow of the Pierre Fauchard Academy. She can be reached via email at drfionacollins@gmail.com.

Disclosure: Dr. Collins reports no disclosures.  

INTRODUCTION
In this time of uncertainty and fear due to the COVID-19 pandemic, the need for practice preservation and practice modification in the aftermath of this pandemic is critical to everyone’s future.¹ After discussions with Dr. Damon Adams, editor-in-chief of Dentistry Today, we were invited to share our efforts and experiences to date as we navigate our way through these uncharted times. Our profession has respected the state and federal requests for closure of our offices to mitigate the spread of the virus. We closed our offices on March 16 and are still only caring for emergency patients at the time of this writing on April 13. Our thoughts expressed in this article reflect this time frame, and we know that the situation is still fluid with an ever-growing body of knowledge related to the SARS-CoV-2 virus being reported almost daily. What we know for certain at this time is that the abrupt stop to patient care created a twofold challenge going forward: How do we keep everyone safe as we re-enter patient care, and how do we restore financial stability to our practices?

Our Initial Actions
Like many of you, our efforts during the first 2 weeks of office closure were focused on establishing lines of credit with our banking institutions and applying for U.S. Small Business Administration (SBA) loans (the Paycheck Protection Program and Economic Injury Disaster Loan). Our entire office staff was placed on “leave of absence” so that our employees could receive short-term unemployment benefits from our office unemployment account rather than utilizing their personal unemployment insurance (UI) accounts. It was going to be a race between receiving SBA benefits or unemployment benefits. Anxiety levels were high. Each employee was assured that his or her position within the team was secure. Letters from our labor attorney verified their statuses for their applications to the UI state office.

We kept in touch with our patients and staff through text messages, phone calls, and “weekly update emails,” which outlined protocols for emergency treatment and provided preventive strategies against the COVID-19 virus. Additionally, the patients were given preventive oral health recommendations during their interrupted oral care. The weekly updates proved to be reassuring for all and assured our patients and staff that we were there for them.

Once we were comforted that our team and financial needs were managed, we shifted our focus to the practice. A skeleton crew was established to assist in patient communication and emergency care management. Key members from each department were identified for their leadership within the practice and their ability to maintain social distancing when not in the practice. The ADA algorithm provided a good framework for the emergency triage of patients requesting care² (Figure 1). We reconfigured job descriptions to allow appropriate tasks to be done from home with new online access. Entire weeks turned into months of patient care that were either canceled, postponed, or rescheduled for the future. Seeing the entire office schedule go blank was utterly shocking.

As time passed, the reality of this “new normal” became clearer. We needed to determine immediate appropriate levels of infection control to keep everyone safe and establish guidelines for the future. The calls for emergency needs were increasing, further augmented with emergencies from interrupted care. Everyone needed to be treated as if they were a COVID-19 carrier because we knew that asymptomatic patients could still carry the virus and be infectious. Therefore, we needed to place additional barriers of protection between all patients and health providers to protect against transmission in both directions. The ADA issued interim recommendations for dental offices, which provided some direction and illustrated the high-risk position that all dental professionals occupied.³

Figure 2. Before: dental supplies storage area prior to space reallocation.	Figure 3. After: new personal protective equipment (PPE) changing area after space and supply reallocation.
Figure 4. A clinical setting with additional protective barriers.	Figure 5. An operator with PPE, including an N95 mask, overlaid with a surgical mask and facial shield.

Figure 6. Aerosol diagram of coughing and sneezing.10

Our Protocols for Emergency and Urgent Care
It became clear that, as healthcare workers, dentistry is a high-risk profession, primarily due to our proximity to the patients and the aerosols that are routinely created with our work.⁴ Until there is a sure way to protect everyone from this highly transmittable virus, we needed to upgrade the “Universal Precautions” to “Transmittable Disease Standards” as described by the CDC.⁵ The following are the protocols that have been established for our office for emergency and urgent patient care. We utilized information from numerous sources^3,5 as well as our own opinions.

Figure 7. Utilizing the clinical microscope allows sitting 10 in farther from the patient, decreasing the aerosol volume by a factor of 8. The extra plastic drape extending behind the patient provides additional aerosol and splatter protection. (Plastic drape recommendation courtesy of Wayne Remington, DDS.)

1. Patients are screened for medical history, current symptoms, travel history, and compliance to social distancing recommendations for a minimum of 14 days.²
2. An entrance to the building that minimizes exposure to other patients was identified.
3. Patient appointments are coordinated to eliminate patient overlap.
4. Upon arrival, patient temperatures are taken, and health and travel histories are reconfirmed. Patients are provided with a face mask to be worn during their time in the office and when exiting after treatment.²
5. All patient magazines and books have been removed from all operatories.
6. Patients are provided with a long, disposable drape in the operatory, rather than the smaller, traditional bib.
7. Patients pre-rinse for 60 seconds with 1.5% hydrogen peroxide, as advised by the ADA, to decrease viral and bacterial loads.³
8. A patient mask/eye shield is used, whenever possible, during treatment.
9. All surfaces are routinely disinfected before and after patient contact (door handles, counter tops, pens, etc).⁶
10. Hallways and open spaces are regularly sprayed with a disinfectant aerosol or fogged with disinfectants such as hypochlorous acid (ie, Dentaqua).⁷
11. Air purifiers are placed in all rooms and open spaces.^6,8
12. Newly established personal protective equipment guidelines are used for all team members^3,6:
a. The staff has a designated entry point leading directly to a changing station to remove street clothes and replace them with the new clinical attire (Figures 2 and 3).
b. Scrubs are worn by all clinical and laboratory staff, along with a clinical jacket covered by an additional disposable gown to be discarded between patients (Figure 4).
c. Facial protection includes an N95 mask overlaid with a customary surgical mask and covered by a plastic facial shield (Figure 5). The coverage of the N95 mask allows for repeated use by the clinician if N95 masks are in short supply. Head protection is augmented with a surgical cap.
13. Oral isolation and suction devices are utilized for all aerosol-producing procedures (eg, rubber dams, Isolite 3 [Zyris], and Nu-Bird).⁹ Currently, hand instrumentation is recommended over ultrasonic instrumentation for hygiene procedures (Figure 6).
14. Clinical microscopes are protected with a plastic barrier, along with an additional plastic drape extending from the oculars to protect the operator from aerosols. The use of the clinical microscope minimizes the spherical volume of aerosol spray (Figure 7).
15. Additional methods to control cross contamination include:
a. All paper documents are left out of the operatory as viruses can remain viable on surfaces for 3 to 72 hours.¹¹
b. All exposed ancillary clinical equipment (eg, loupes/headlamps, intraoral scanners, keyboards, etc) are disinfected after contact.^6,11
c. All efforts are made to pre-dispense materials to minimize cross contamination (eg, cement, composite, and impression materials). Additionally, a secondary assistant may be utilized to maintain sterility.
16. All post-treatment activities and transactions are done in the patient’s operatory.
17. Laboratory dental technicians follow the same protocols as the clinical staff when entering and leaving an operatory while also maintaining strict infection protocols within the laboratory.

CLOSING COMMENTS
One thing is for certain: As the future continues to evolve and our profession identifies new issues to be addressed, the impact of COVID-19 will have long-lasting effects on the dental practice. The positive outcome is that these new protocols for sterilization and aerosol control will better protect us, our dental office and treatment teams, and our patients into the next decades. A sense of responsibility needs to be established within each patient as to his or her need for excellent biofilm control; proper use of fluorides; and optimal lifestyle choices in food, exercise, and habits.

When faced with adversity, it is critical that we take ownership of the issues facing us. Our profession and community are experiencing new challenges as a direct result of the COVID-19 pandemic, forcing us to critically examine our best practices and evolve them into a superior standard of care.

References

1. World Health Organization (WHO). Coronavirus Disease 2019 (COVID-19) Situation Report 32. February 21, 2020.
2. American Dental Association. ADA Interim Guidance for Management of Emergency and Urgent Dental Care. Updated April 1, 2020.
3. American Dental Association. ADA Interim Guidance for Minimizing Risk of COVID-19 Transmission. Updated April 1, 2020.
4. Sabino-Silva R, Jardim ACG, Siqueira WL. Coronavirus COVID-19 impacts to dentistry and potential salivary diagnosis. Clin Oral Investig. 2020;24:1619-1621.
5. Centers for Disease Control and Prevention. Coronavirus disease 2019 (COVID-19). Dental settings. Revised April 7, 2020. Accessed April 16, 2020. https://www.cdc.gov/coronavirus/2019-ncov/hcp/dental-settings.html.
6. US Department of Labor, Occupational Safety and Health Administration. Guidance on Preparing Workplaces for COVID-19. OSHA 3990-03 2020. Accessed April 16, 2020. https://www.osha.gov/Publications/OSHA3990.pdf.
7. US Environmental Protection Agency. List N: Disinfectants for use against SARS-CoV-2. Accessed April 16, 2020. https://www.epa.gov/pesticide-registration/list-n-disinfectants-use-against-sars-cov-2.
8. Peng X, Xu X, Li Y, et al. Transmission routes of 2019-nCoV and controls in dental practice. Int J Oral Sci. 2020;12:9.
9. Dahlke WO, Cottam MR, Herring MC, et al. Evaluation of the spatter-reduction effectiveness of two dry-field isolation techniques. J Am Dent Assoc. 2012;143:1199-1204.
10. Froum S, Strange M. COVID-19 and the problem with dental aerosols. Perio-Implant Advisory. April 7, 2020.
11. van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. 2020;382:1564-1567.

Dr. Paquette is a past president of the American Academy of Esthetic Dentistry and the Pacific Coast Society of Prosthodontics (PCSP). She is recognized nationally and internationally as a leader in aesthetic dentistry, prosthodontics, and implant dentistry. She is a Diplomate of the American Board of Prosthodontics and a Fellow of the American College of Prosthodontists. She holds fellowships in the International College of Dentists (ICD), the American College of Dentists (ACD), and the Pierre Fauchard Academy (PFA). She is also a member of the Academy of Osseointegration. Dr. Paquette has authored numerous research and clinical articles on her areas of expertise and co-authored several textbook chapters. She is co-executive director of the Newport Coast Oral Facial Institute (NCOFI). Dr. Paquette can be reached at jmpaquette@ncofi.org.

Dr. Sheets maintains a full-time private practice in Newport Beach, Calif, for aesthetic rehabilitative dentistry. She is an international educator, a clinician, an author, and a researcher. She is a Fellow of the AGD, ACD, ICD, PFA, and the Academy of Dentistry International. Dr. Sheets is founder and co-executive director of the NCOFI, a non-profit international teaching and research center for dentists and dental technicians, in Newport Beach, Calif. She and James C. Earthman, PhD, professor of material science & engineering and biomedical engineering at the University of California, Irvine, are leading research on quantitative percussion diagnostics for teeth and implants. They hold numerous US and international patents on this groundbreaking technology. Dr. Sheets can be reached at cgsheets@ncofi.org.

Dr. Wu is on the executive council for the PCSP and a past president of the Academy of Microscope Enhanced Dentistry. She is also a member of the ADA, the California Dental Association, and the Orange County Dental Society (OCDS). She was a board member of the OCDS in 2011 and a senior delegate in 2012. Currently, Dr. Wu is a partner in the Sheets, Paquette and Wu Dental Practice and co-executive director with NCOFI, a non-profit international teaching and research center. She is also actively involved with several research projects on dental implants and materials and has published articles in several dental journals. Dr. Wu can be reached at jcwu@ncofi.org.

Disclosure: The authors report no disclosures.

Related Articles

Tennessee Reopens Practices While Massachusetts Waits

COVID-19 Is Changing Dentistry, and Our Office Is Changing With It

AGD Releases Guidance for Returning to Work

John A. Molinari, PhD

Dr. Molinari, it seems that many people are confused about requirements for sterilization monitoring. What are the requirements?
The US Centers for Disease Control and Prevention (CDC) recommends that correct functioning of sterilization cycles should be verified for each sterilizer using a biological indicator (BI) and control at least once a week.¹ Virtually every state has taken this quality control recommendation from the CDC and turned it into a requirement for most healthcare settings, including dental practices. In addition, loads containing implantable devices should be biologically monitored, and the items quarantined until BI results are known. The importance of routine biological monitoring cannot be overemphasized, as BIs can ascertain the effectiveness of many of the steps involved in instrument reprocessing. Sterilization procedures are routinely monitored using a combination of mechanical, chemical, and biological indicators. Taken together, these indicators evaluate the sterilizing conditions and effectiveness of the process. Because BIs directly monitor sterilization by assessing the processes’ ability to kill known highly resistant bacterial spores (eg, Geobacillus or Bacillus species), rather than only testing the physical and chemical conditions necessary for sterilization, the use of calibrated BIs remains the accepted “gold standard” for monitoring.
Although multiple studies have shown that the most common cause of sterilization failures is human error, other problems can compromise sterilizer efficiency. A few common errors are listed in Table 1.

We have seen advertisements that tout the use of “faster” sterilizers; how are they different from the standard autoclave and what are the advantages of “faster and better”?
If you are using an autoclave like the overwhelming majority of dental practices, you probably have been using a gravity displacement autoclave. This type of unit has been available for more than a century and sterilizes with self-generated steam that is created within the chamber or by a component steam generator. Because air entering the chamber mixes with air, cool air pockets can form within the chamber, which may result in extended times for sterilization of certain items. In addition, overloading this type of autoclave can lead to incomplete drying of sterilized instrument packs, resulting in the user commonly finding wet packages at the end of the cycle. Modification of later generations of autoclaves has resulted in some sterilizers using pressure-pulsing techniques along with gravity displacement techniques to assist in removing air from the chamber before the sterilization cycle.
Development of a new generation of autoclaves within the last 2 decades has added a new dimension to this heat sterilization modality. These autoclaves are classified as “Class B” sterilizers or “pre- and post-vacuum” steam sterilizers. The equipment is fitted with a pump that creates an initial vacuum in the chamber to ensure air is removed from the sterilizing chamber before steam enters. In contrast to a gravity displacement autoclave, this procedure allows faster and more thorough steam penetration throughout the entire load. The poststerilization vacuum cycle also is highly efficient because it facilitates drying. Practices that utilize this type of sterilizer frequently report the instrument packs are “bone dry” at the end of the sterilization process.

If you could present people with fundamental rules of thumb for practicing proper infection control in a dental office, what would they be?
One aspect of infection control that is sometimes forgotten in the ongoing evolution of technologies, methodologies, and products is that long-standing, basic infection control principles have not really changed over the years. While there is certainly no single “best list,” I can offer the following to summarize major areas:

• Perform effective hand hygiene
• Immunize against vaccine-preventable diseases
• Use personal protective equipment appropriately
• Heat sterilize all reusable patient care instruments/items used intraorally
• Use respiratory hygiene/cough etiquette
• Prevent cross-contamination with aseptic technique and environmental asepsis
• Prevent sharp injuries by using safe work practices and engineering controls.

You may find that as you review and consider each of these, many of the procedures and protocols that you perform as routine components of your practice day provide effective applications of these principles. You may be pleasantly surprised as to just how well your infection control program is working.

Demonstration of fit and feel for right- and left-fitted versus ambidextrous gloves.

There are new products on the market that talk about being “eco-friendly,” yet many infection control products are labeled as disposable, and I hear some may even be toxic to the environment. What is the status of environmentally friendly infection control products?
A new era of developing strategies and marketing products designed to address environmental issues is rapidly expanding into multiple areas of infection control. Many hospitals and other healthcare facilities took the initiative to lower waste accumulation by using approaches that include adopting programs that use more recyclables and reusable items and looking for products that reduce the amount of disposable waste.
“Green dentistry” has also become more than merely a slogan in the profession. A number of manufacturers are focusing on the use of disposable items. Widespread use of disposable covers, tips, traps, instrument wraps, pouches, and other items has helped to streamline infection control with regard to time and reprocessing efforts. Advances in research into the cost effective manufacture of recyclable and biodegradable plastic and paper items appear to be accelerating, with the hope that what was once destined for deposit in landfills may now be recycled and used again, in a similar way that aluminum cans are reprocessed. You may also be surprised to find that more “plastic” wraps and covers that we frequently use are manufactured to be biodegradable. This technology has also made its appearance into the areas of instrument reprocessing and environmental surface disinfection. Cleaning solutions used on contaminated instruments before heat sterilization can now contain multiple enzymes to enhance removal of bioburden. These components are biodegradable, thereby preventing introduction of potentially harmful chemicals into ground water. Even the relatively recent application of environmental surface disinfectant solutions and wipes is seeing continued progress towards reducing chemical waste. Tuberculocidal disinfectant preparations that are less harmful to the environment, even biodegradable, are already available, in addition to reusable plastic containers.

Dr. Molinari, with all of the recent stories in the media about the spread of infectious disease in healthcare settings, it is almost unbelievable that people are not following even the most basic guidelines. Why are these incidents occurring, and are they limited to healthcare facilities?
We continue to see reports about possible infectious disease transmission in hospitals and other healthcare facilities being traced back to glaring breaches in infection control. In just reviewing the past few years of possible incidents, multiple facilities have been investigated for failures associated with accepted infection control standards and instrument reprocessing protocols. Investigations also include 2 Veteran Affairs hospital dental clinics where the possible failure of clinic staff to comply with mandated infection control standards and protocols is under scrutiny. Allegations include improper use of gloves, burs, and procedures involved in instrument cleaning and sterilization of instruments.
From where do these and many other possible patient exposures result? Accumulated evidence gathered over many years has shown human error and failure to comply with required and/or recommended procedures to be the major culprits. Despite documentation of multiple instances, we still find some people, including healthcare professionals, who feel that taking shortcuts in certain infection control procedures is not particularly dangerous. However, please keep in mind that even the most rigorous infection control practices do not guarantee against accidental breaches or some undetected, undetermined, transmission incident. We simply must do the best we can to minimize the potential for cross-infection.
While the potential for infections may not be eliminated even when proper infection control practices are followed, lack of compliance can unknowingly increase the potential for microbial cross-contamination and cross-infection. What I think needs to be remembered is that proper application of individual infection control practices, procedures, and protocols help to strengthen other seemingly unrelated program components. Overlapping preventive measures are used routinely and they work. Sometimes we just do not think of them as being reinforcements for each other.

Hands coated with fluorescent powder representing contamination.	Residual powder remaining after brief wash procedure.

As far as cleaning and disinfecting the operatory, what tips and suggestions do you have to make it efficient yet effective?
First and foremost, apply a basic premise of aseptic technique: clean it first. The importance of initial cleaning cannot be overemphasized and is included in all infection-control recommendations. Initial cleaning and subsequent disinfection are important, because together they minimize the potential for cross-infection from environmental surfaces. It also must be mentioned that manufacturers are required to state on the product label that the disinfectant should be applied onto precleaned surfaces. Although separate cleaners and disinfectants may be applied, chemical agents that accomplish both functions offer a more efficient approach. Recently published studies with THE DENTAL ADVISOR have reported the primary cleaning efficacy of commercial disinfectant sprays and wipes.
A few other suggestions on surface disinfection are offered in Table 2.²
Unfortunately, misuse or overuse of chemical disinfectants can create problems for both a person’s health and equipment integrity.³ In addition to discoloring or compromising the integrity of treated operatory surfaces, practice personnel can exhibit a variety of clinical manifestations from long-term unwanted exposure to chemicals. Respiratory problems, such as wheezing or sneezing, development of allergies, ocular irritation, and headaches can occur as a result of excessive spraying of a disinfectant. You may want to review and reevaluate written protocols for environmental asepsis if personnel in the practice develop these types of symptoms. The review should include consideration for implementing routine use of disinfectant wipes as a replacement for spray formulations.

What resources are available to dental healthcare professionals to stay up-to-date?
There are a number of Web sites and organizations available to provide you with additional information and current developments in this area. Two informative groups to consult initially can be found at osap.org and ecodentistry.org. Of course, dentaladvisor.com offers a “Q and A” area in the Infection Control Corner, where I respond to questions after my lectures and those posed by our readers.

Dr. Molinari, you recently accepted a new position as director of infection control with THE DENTAL ADVISOR in Ann Arbor, Michigan; can you comment on the work you are now doing?
I am honored to be part of such a great team of dental professionals. THE DENTAL ADVISOR has been providing scientific and evidenced-based research for almost 30 years. Our team meets weekly to discuss our publication, evaluations, long-term clinical studies, and to report on issues relevant to real world clinical dentistry. We work closely with manufacturers on product development and enhancement. Although I miss working with my students at the dental school, my role as director of infection control allows me to do what I love most: research, continuing to teach at different forums, and reporting to the dental profession. Our recently introduced sterilization monitoring program allows me to keep in contact with many offices regarding proper infection control practices, provide webinars, as well as provide subscribers access to our website 24/7, which has valuable information on all areas of clinical dentistry, as well as our research. Your readers may visit our infection control corner at dentaladvisor.com/clinical-evaluations/infection-control-corner.shtml to submit any questions related to infection control.

CLOSING COMMENTS
While dental care providers have much to be proud of in their infection control protocols and practices, new challenges continue to emerge that can potentially threaten our safety and that of patients. The past 30 years have seen a veritable explosion of science-, clinical-, and epidemiological-based knowledge in this area, with resultant development of new technologies and available product choices. As expected questions continue to be asked concerning the efficacy and potential problems of available infection control products, I deeply appreciate the opportunity to offer my thoughts in answering a few of these questions.

References

1. Kohn WG, Collins AS, Cleveland JL, et al; Centers for Disease Control and Prevention (CDC). Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.
2. Molinari JA, Harte JA, eds. Cottone’s Practical Infection Control in Dentistry. 3rd ed. Baltimore, MD: Lippincott Williams & Wilkins; 2009.
3. Rutala WA, Weber DJ; Healthcare Infection Control Practices Advisory Committee (HICPAC). Guideline for disinfection and sterilization in healthcare facilities. cdc.gov/hicpac/pdf/guidelines/Disinfection_Nov_2008.pdf. Accessed January 3, 2011.

Dr. Molinari is currently director of infection control for THE DENTAL ADVISOR in Ann Arbor, Mich. His position involves research on various products, publication of abstracts, and overseeing a Sterilization Monitoring Program, as well as lecturing and answering questions from readers of THE DENTAL ADVISOR. Previously, he served for 32 years at the University of Detroit Mercy School of Dentistry as professor and chairman of the department of biomedical sciences and director of infection control. He continues serving as a consultant for the CDC, ADA Council on Scientific Affairs, and the Council on Dental Practice. He is currently a member of the Michigan Board of Dentistry. In recognition of his efforts, Dr. Molinari was inducted as an honorary member of the Michigan Dental Association, the International College of Dentists, and the American College of Dentists, and he is a 2009 recipient of the ADA Golden Apple Award. He has published more than 350 scientific articles, text chapters, and abstracts, and he lectures internationally on infectious diseases and infection control. He has held many editorial positions for various publications and continues to serve the profession as an opinion leader on many topics related to infection control. He can be reached at (734) 665-2020 ext 110 or at jmolinari@dentaladvisor.com.

Disclosure: Dr. Molinari is a paid consultant for Hu Friedy Manufacturing as well as SciCan.

Question 1. How has widespread vaccination of the general population impacted the incidence of many infectious diseases?
The rationale for increasing the role for public health immunizations in the last century was based on the usefulness of vaccines compared to other protective approaches. The latter include: (1) development of natural active immunity after recovering from symptomatic or asymptomatic infection, and (2) therapeutic or prophylactic administration of antimicrobial drugs. The following table published by the CDC in 1999 illustrates the dramatic reversal observed for a number of historical disease scourges as a result of widespread vaccination (Table).
     The global eradication of smallpox, near elimination of poliomyelitis, and > 95% reduction in the incidence of previously common diseases such as measles, mumps, rubella, diphtheria, and tetanus in developed countries has helped to save many lives and contributed to an increase in the well being and life expectancy of their populations. The Advisory Committee on Immunization Practices of the CDC annually reviews recommended vaccination schedules using the most recent scientific and clinical information when considering changes in schedules, vaccine formulations, proposed inclusion of additional approved vaccines, and safety alerts where necessary.

Question 2. The observed public health success of many vaccines is well documented. However, even with this achievement we still have not been able to eliminate any additional vaccine-preventable diseases other than smallpox. Why?
Please remember, routine childhood immunization programs are a primary reason for the demonstrable decline in the incidence of many vaccine-preventable infections. Using a relatively recent example to illustrate, think about how virtually everyone contracted an active case of chickenpox at a young age before 1995. Then the varicella-zoster vaccine (Varivax) became available. Since that year, the annual incidence of this viral infection in the United States has dropped from more than 4 million cases in 1994 to a little more than 30,000 cases in 2008. Unfortunately, certain vaccine-preventable diseases like chickenpox have not been eliminated, in part because a substantial percentage of the recorded disease morbidity and mortality now occurs in adults and adolescents. Thus, healthcare providers and others who have neither experienced natural infection nor been immunized for diseases such as chickenpox, measles, rubella, and mumps are at increased risk for these droplet-mediated infections. In addition, we still see too many people contract other preventable diseases such as Streptococcus pneumoniae pneumonia and influenza despite the availability of safe and effective vaccines. Multiple reasons are given to explain the fact that adults do not have a high vaccination rate, including: (1) common belief that most immunizations are only for childhood diseases; (2) missed opportunities to receive vaccines; (3) lack of perceived risk by individuals for vaccine-preventable infections; (4) misperception that vaccine-preventable diseases have been virtually eliminated; and (5) concerns and fears about postvaccination adverse effects.

Question 3. How safe are vaccines when they become available and are recommended for widespread use?
The answer to this inquiry must begin by stating that vaccination is one of the most effective, widely used, and cost efficient public health strategies for combating infectious diseases. Having said that, it must also be noted that no vaccine is 100% effective or perfectly safe. Even with a > 95% response rate shown for many vaccines, there still are a small percentage of recipients who do not develop protective immune responses postvaccination. Unless they are tested for the presence of induced antibodies and found to be nonresponders, these individuals unknowingly remain susceptible to microbial infection during an outbreak. Thus, when a local epidemic occurs it is not unexpected to find “vaccinated” individuals included in the total disease count.
      With regard to safety, there are a number of features which are consistent for all vaccine programs. A few representative considerations are:
      All vaccines are thoroughly studied and tested before they are licensed for public use. Extensive laboratory investigations are required before any clinical trials are initiated to further evaluate their efficacy and safety. If results are favorable, the US Food and Drug Administration evaluates the data and can approve public release of the vaccine.
     There is a strong multi-check system in place to provide ongoing monitoring of vaccines. This involves a concerted effort by a variety of agencies including federal, state, and local health departments to collect and investigate ongoing information on vaccine safety. Two important monitoring systems here are the Vaccine Adverse Event Reporting System and the Vaccine Safety Datalink project, and members of the public can also submit reports of possible side effects for further investigation.
     As with any other medication, adverse effects can occur following immunizations. The overwhelming majority of these (> 90%) are minor, usually involving a sore arm and/or mild fever. These resolve relatively quickly. Unfortunately, rare serious reactions also can occur. These may be seen in one individual out of hundreds of thousands to millions of vaccine recipients. In some instances, the event may be so rare so that it cannot be appropriately investigated. Thus, the risk from disease versus risk from vaccination must always be evaluated and compared where possible.
The question can also be asked here—what if vaccines were not available? There isn’t any doubt that not only would there would be many more disease cases, but also more serious disease sequelae, including more deaths. Consider the following disease and vaccine adverse sequelae comparison:

Measles:

• Six cases in 100 develop pneumonia.
• One in 1,000 develops encephalitis.
• Two in 1,000 die from measles complications.

Mumps:

• One in 300 develop encephalitis.

Rubella:

• One in 4 pregnant women can give birth to a baby manifesting congenital rubella syndrome, if the woman becomes infected early in the pregnancy.

Measles Mumps and Rubella (MMR) vaccine:

• One recipient in 1,000,000 develops encephalitis or allergic reaction.

Any instance of a serious event caused by immunization is one too many, but the fact remains that a nonvaccinated child or adult has a far greater life-threatening risk from contracting the disease than from receiving a vaccine. In addition, remember that collected data including adverse reactions are continually analyzed and evaluated for possible vaccine-associated complications.

Question 4. A major argument voiced by many who do not want to receive vaccinations is that some vaccines can cause autism. Are there scientific, clinical, and/or epidemiological data to indicate such a relationship exists?
It is impossible to go into much depth for this topic here with the limited space available. A few selected references are provided at the end of this discussion. Suffice it to say the possible association of autism and vaccination has been a hot button issue since 1998. It was then that a widely publicized article published in The Lancet initially speculated about a possible relationship between autism and receipt of MMR vaccine. This “conclusion” was based on research involving only a few children, the temporal association of MMR childhood vaccination, and recognition of autism in children. The article has subsequently been discredited for a number of reasons, and in 2010 the journal took the dramatic step of officially retracting the article. Fortunately, in the last 10 years, at least 7 to 8 large, controlled studies have investigated this important issue and been published in reputable, refereed journals. Taken collectively, the findings provide strong evidence against the hypothesis that vaccination causes autism. Even though a substantial amount of research has been undertaken investigating this and other possible untoward neurological effects of vaccinations, controversy and heated discussion continue. Numerous sources of information are available. Please avail yourself of the opportunity to study reports and opinions alike, so that you as a health professional can be armed with the best possible documented, credible findings as you are faced with vaccine questions in both your professional and personal life.

CONCLUSION
In conclusion, none of the currently available vaccines provide absolute protection, nor are they perfect. However, as research continues to discover and study infectious disease risk factors, there is little doubt that effective, safe, next generation vaccines will offer additional opportunities to protect those at risk.

SUGGESTED READING 

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. 11th ed. Washington, DC: Public Health Foundation; 2009.

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. 11th ed. Washington, DC: Public Health Foundation; 2009.

Centers for Disease Control and Prevention, Immunization Safety Office. cdc.gov/vaccinesafety/ Activities/ About_ISO.html. Accessed September 29, 2010.

Centers for Disease Control and Prevention. Ten great public health achievements—United States, 1900-1999. MMWR Morb Mortal Wkly Rep. 1999;48:241-243.

Clarkson TW, Magos L, Myers GJ. The toxicology of mercury—current exposures and clinical manifestations. N Engl J Med. 2003;349:1731-1737. 

Harte JA, Molinari JA. Cottone’s Practical Infection Control in Dentistry. 3rd ed. Baltimore, MD: Lippincott Williams & Wilkins (Wolters Kluwer Health); 2009. 

US Food and Drug Administration. Thimerosal in vaccines. fda.gov/cber/vaccine/thimerosal.htm. Accessed September 29, 2010.

Dr. Molinari is currently director of infection control for THE DENTAL ADVISOR in Ann Arbor, Mich. Previously, he served for 32 years at the University of Detroit Mercy School of Dentistry as professor and chairman of the department of biomedical sciences and director of infection control. He continues serving as a consultant for the CDC, ADA Council on Scientific Affairs, and the Council on Dental Practice. He is currently a member of the Michigan Board of Dentistry. In recognition of his efforts, Dr. Molinari was inducted as an honorary member of the Michigan Dental Association, the International College of Dentists, and the American College of Dentists, and he is a 2009 recipient of the ADA Golden Apple Award. He has published more than 350 scientific articles, text chapters, and abstracts, and he lectures internationally on infectious diseases and infection control. He was the infection control section editor for the Compendium of Continuing Education in Dentistry, a member of the editorial board for the Journal of the American Dental Association, and writes a monthly column for Dental Economics. He can be reached at johnmolinariphd@gmail.com.

Disclosure: Dr. Molinari is a consultant for Hu-Friedy and SciCan.

Photo: iStock

INTRODUCTION
The last 2 decades have seen the development and implementation of a number of comprehensive “state-of-the-art” infection control recommendations and regulations. These have been aimed at ensuring high levels of health professional and patient safety in healthcare settings. Although compliance among dental and medical treatment providers continues to increase, when someone does not understand the complete rationale for what is being recommended or required, questions and doubts become increasingly common.
     This article will use the same format as the one that appeared in March 2010 issue of Dentistry Today to focus on representative issues that can present occasional misunderstanding and compliance problems in the areas of hand hygiene and instrument reprocessing. The discussion is designed to use common questions that are asked as a basis for reinforcing both the “what” and the “why” of published infection control recommendations.

Question 1. There have been a number of waterless, alcohol-based hand antiseptics marketed in recent years. I hear from colleagues they are recommended over hand washing for routine use in clinical settings. Does this mean that hand washing is no longer considered effective or acceptable?
You have several acceptable choices for accomplishing effective hand hygiene in your practice. These alternatives are included in the comprehensive 2003 Centers for Disease Control and Prevention (CDC) infection control recommendations for dentistry. Either plain soap or an antimicrobial soap and water can be used for nonsurgical dental procedures, such as examinations, preventive procedures, restorative dentistry, orthodontics, and endodontic procedures. If hands are not visibly soiled or contaminated with blood or other potentially infectious material (ie, saliva, bloody saliva), use of a waterless, alcohol-based hand rub is also acceptable. It is important to note the specific wording of the recommendation: “If hands are not visibly soiled, an alcohol-based hand rub can also be used.”
While the use of an antiseptic agent provides effective antimicrobial activity against overgrowth of normal, commensal, and transient microflora; the basic tenet of hand washing is to clean hands. Several factors must be considered when deciding what approach will be used. These factors include the type of procedures performed in the clinical facility, degree of anticipated contamination during patient treatment, and whether or not residual or persistent antimicrobial activity is needed after hand hygiene procedures. Thus, you can choose to routinely use a liquid soap or antimicrobial antiseptic and water. Use of plain soap is appropriate for removing skin debris and microbial contamination. Since intact skin is a primary barrier, any non-antimicrobial soap considered should contain ingredients to prevent skin irritation and dryness to help preserve epithelial integrity. Optimal properties for use of an antimicrobial antiseptic with water should include broad antimicrobial spectrum of activity, ability to act fast, and a residual, persistent effectiveness.
The key for use of whatever hand hygiene agent that you decide upon is compliance. Several clinical reports published in the medical literature have indicated that the incidence of healthcare-associated infections decreased as healthcare workers (HCW) demonstrated improved hand hygiene practices. Other studies have also shown that compliance increased with use of alcohol-based hand rubs. As such, the 2002 CDC guidelines for hand hygiene in healthcare settings that served as the basis for the 2003 dental recommendations, advocated a combined protocol of hand washing and alcohol-based agents for routine hand antisepsis.

Question 2. Are there any recommendations for the use of hand lotion in clinical settings?
Lotions are recommended to reduce drying of hands and possible dermatitis from glove use. Use of lotions is especially important in healthcare where HCW frequently wash their hands 20 or more times a day, thereby leading to an increased potential for chronic irritation dermatitis. Previously, the overwhelming majority of commercial lotions were petroleum-based. While they can lubricate and replenish keratinized epithelial tissues, these formulations also unfortunately react with gloves being worn (primarily latex gloves) and increase their permeability. Basically, the gloves can become tacky, and thus do not provide the appropriate dexterity needed during treatment. Water-based lotions are far more compatible with gloves, can be absorbed into the skin more rapidly, and have become increasingly available in both the healthcare and public marketplaces. When deciding which lotion to use, consider the possible interaction of the glove type, dental materials, and antimicrobial hand hygiene products with the lotion.

Question 3. What are some of the common errors that can lead to sterilization failure?
There are multiple factors that can adversely affect sterilization cycles in an autoclave, dry heat, or unsaturated chemical vapor sterilizer. Problems that apply to each of these heat sterilizers include the following 6 issues:
1. Improper cleaning of instruments. Cleaning is the basic, critical step in instrument processing because it involves removal of contaminating debris and organic material from an instrument before sterilization. If blood, saliva, and other contamination remain, they can shield adherent microorganisms and potentially compromise the sterilization process.
2. Improper packaging. This factor includes using the wrong type of packaging material for method of sterilization, placing too many instruments in a package, and wrapping items in excessive amounts of packing wrap. If the material used to package instruments is not compatible, or excessive wrap is used, the sterilizing agent (ie, moist heat under pressure, dry heat, unsaturated chemical vapor under pressure) may not be able to appropriately contact instrument surfaces, thereby resulting in a sterilization failure. Also, if the packaging material cannot withstand the high temperatures required for dry heat sterilizers, it may melt and create additional problems with the unit.
3. Overloading the sterilizer. Overloading the chamber can result in prolonged warm-up times needed to reach sterilization conditions, and may also prevent thorough contact of the sterilizing agent with all items in the unit. Not spacing wrapped instrument packages adequately is a common problem observed with sterilization failures. Most sterilizers sold in recent years are provided with racks or trays, which allow a maximal capacity of instrument packages and effective sterilization with prescribed cycles. A number of older units can also be fitted with available racks or trays.
4. Inappropriate sterilization time, temperature, and/or pressure. Issues to consider here include use of inadequate temperature or time during the sterilization cycle and interrupting the total cycle. Human error plays a role here if the sterilizer door is opened during the cycle or timers are incorrectly set, thereby resulting in incomplete sterilization.
5. Inadequate maintenance of sterilization equipment. Routine maintenance as recommended by the manufacturer is critical to the whole instrument processing protocol. Examples of problem areas here are defective control gauges, which may give erroneous readings of conditions inside the chamber and worn door gaskets and seals.
6. Use of improper equipment for sterilization. This potential problem is clearly addressed in the CDC Guidelines for Infection Control in Dental Health-Care Settings—2003, with the recommendation: “Use only FDA-cleared medical devices for sterilization and follow the manufacturer’s instructions for correct use.” Neither household ovens nor smaller toaster ovens meet the stringent criteria required in testing and evaluation as heat sterilizers.

Question 4. What are the basic differences among the variety of chemical indicators available for use in heat sterilization?
Chemical indicators use sensitive chemicals to assess physical conditions (eg, time and temperature) during a sterilization process. Common forms are available as paper strips, labels, and steam pattern cards, which change color when certain temperature, time, and/or pressure conditions are reached during the heat cycle. Since they do not contain bacterial spores as the active agent, chemical indicators are not able to prove that sterilization has been achieved. They are valuable, however, by being able to detect certain malfunctions and can also help to identify procedural errors. Autoclave tape is the historical example of a chemical indicator. It was used for many years as visible proof that items in the chamber had been exposed to a heat sterilization process. Unfortunately, the temperature-sensitive stripes on this tape appear long before sterilizing conditions are reached in the chamber; therefore, this external marker is the least sensitive indicator for heat sterilization.
Recommendations addressing sterilization monitoring continue to include chemical monitoring of cycles. In the comprehensive 2003 CDC guidelines, the following recommendation is made: “Use mechanical, chemical, and biological monitors according to the manufacturer’s instructions to ensure the effectiveness of the sterilization process.” Each load to be sterilized should be monitored with both mechanical and chemical indicators. In a possible event where heat and pressure conditions may not be the same inside and outside the pouch, the guidelines also call for using a chemical indicator on the inside of each package in order to verify that sterilizing vapor has penetrated to reach instruments. A relatively recent innovation has made it easier to accomplish this step. Instrument pouches which contain built-in external and internal multiparameter indicators are now available. Those can provide valuable information to personnel regarding time, temperature, and sufficient exposure of processed instruments to steam.

Question 5. How applicable is “cold sterilization” in today’s world of dental infection control?
Cold sterilization as related to dentistry refers to the practice of immersion (ie, liquid chemical) disinfection used to reprocess reusable semi-critical instruments or items for patient care. Chemical germicides used in this manner have been either glutaraldehydes, hydrogen peroxide-based, or peracetic acid solutions. There are multiple reasons why chemical immersion sterilization is no longer considered appropriate for reprocessing heat-stable medical instruments. First and foremost, virtually every available reusable dental instrument is heat-stable and should be appropriately cleaned, packaged, and sterilized between uses with a heat-based, biologically monitored process, such as a steam autoclave, dry heat sterilizer, or unsaturated chemical vapor sterilizer. The CDC refers to heat sterilization as the method of choice when sterilizing instruments and devices. If an item is heat sensitive, it is preferable to use a heat-stable alternative or disposable item. While chemical sterilants can sterilize items that would be damaged by heat, the process to accomplish this may require 6 to 10 hours of immersion. Other factors have also precluded the routine use of cold sterilization in current infection control protocols, including: (1) sterilized items must be rinsed with sterile water after removal from the solution in order to remove toxic or irritating chemical residues, and (2) a sterilization process using liquid chemicals cannot be verified by biological, spore test monitors.

Question 6. We are thinking about switching our practice to using cassettes as containers for our instruments. What factors should we consider as we discuss this major step?
The procedural shift away from ungloved healthcare personnel using small scrub brushes to routinely clean contaminated instruments at sinks has been dramatic. As more data have accumulated concerning the potential for personnel to be accidentally stuck with sharp, contaminated instruments, the use of cassettes in hospitals; dental, hygiene, and assisting schools; practices; and other healthcare facilities has increased significantly over the years. A central, precautionary reason for this is the long-standing infection control recommendation that contaminated instruments should be handled carefully, and as little as possible, in order to minimize the occurrence of accidental sharp exposures. Depending on how instruments and packages are handled and subsequently loaded into a sterilizer, there is a potential for personnel to be accidentally stuck with a sharp instrument. Using this concept as a starting point for discussion, the following should be included when discussing incorporation of cassettes into a practice setting:
1. A cassette system can substantially reduce direct handling of contaminated instruments before sterilization.
2. Different cassette sizes are available, whereby they can hold complete sets of instruments for single procedures; this eliminates the need to prepare and process multiple packages.
3. When loaded properly, it is very difficult to overload the cassette; instrument rails or racks inside the cassette are designed to hold a certain number of instruments.
4. Damage to instruments during processing in a cassette can be reduced from that noted with use of bags or pouches, because the items are held more securely in place.
5. Perforated cassettes are preferable over completely solid containers, as the latter may not allow steam or chemical vapor to reach the contents for sterilization to occur.

CLOSING COMMENTS
You have heard many times that there are multiple approaches and strategies available to assist in accomplishing recognized infection control goals. As public, health professional, and governmental attention continues to focus on providing a high level of safety for HCW and patients alike, it is quite natural for concerned, committed people to have subsequent questions. Hopefully, this brief discussion has offered useful information addressing some areas that you may be thinking about.F

SUGGESTED READING
American Dental Association (ADA). Statement on Infection Control in Dentistry. ada.org/1857.aspx. Accessed on June 30, 2010.
Harte JA, Molinari JA. Cottone’s Practical Infection Control in Dentistry. 3rd ed. Baltimore, MD: Lippincott Williams & Wilkins (Wolters Kluwer Health); 2009.
Kohn WG, Collins AS, Cleveland JL, et al; Centers for Disease Control and Prevention (CDC). Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. December 19, 2003;52(RR-17):1-61. cdc.gov/mmwr/preview/mmwrhtml/rr5217a1.htm. Accessed on July 27, 2010.

Dr. Molinari is currently Director of Infection Control for THE DENTAL ADVISOR in Ann Arbor, Mich. Previously, he served for 32 years at the University of Detroit Mercy School of Dentistry as professor and chairman of the Department of Biomedical Sciences and Director of Infection Control. He continues serving as a consultant for the CDC, ADA Council on Scientific Affairs, Council on Dental Practice. He is currently a member of the Michigan Board of Dentistry. In recognition of his efforts, Dr. Molinari was inducted as an honorary member of the Michigan Dental Association, the International College of Dentists, and the American College of Dentists, and he is a 2009 recipient of the ADA Golden Apple Award. He has published more than 350 scientific articles, text chapters, and abstracts, and he lectures internationally on infectious diseases and infection control. He was the Infection Control section editor for the Compendium of Continuing Education in Dentistry, a member of the editorial board for the Journal of the American Dental Association, and writes a monthly column for Dental Economics. He can be reached via e-mail at johnmolinariphd@gmail.com.

Disclosure: Dr. Molinari is a consultant for Hu-Friedy Manufacturing and for SciCan.

Photo: Getty Images

Occupational Safety and Health Association requires provider and patient to wear proper eyewear to protect against airborne infections

The most recent comprehensive infection control guidelines and recommendations for dentistry were published in 2003.¹ An “evidence-based” format was utilized in the development of this document, including inclusion of initial sections which reviewed published epidemiological, clinical, and scientific information related to the specific recommendations presented later in the publication. Even though the 2003 US Center for Disease Control (CDC) Guidelines represent continued application of updated practices, procedures, and products; the essential component for success of an infection control program remains compliance. Published surveys have suggested that, although adherence to documented evidence-based recommendations is effective in limiting the potential for accidental occupational exposures, compliance with published guidelines and regulations can be an issue.^2-4 Questions by conscientious healthcare providers continue to be asked concerning how to accomplish practical applications of published recommendations, sometimes with the mistaken perception that there is only one single approach to achieving infection prevention goals. In addition, use of practices that are unsupported by accumulated scientific evidence, or inferential application of those data, can also reduce compliance and lead to later problems. Instead, what we need to remember is that while effective infection control requires application of basic principles, healthcare professionals should realize that there are reasonable choices in a number of areas when they develop practice protocols and when choosing available products.

Question 1. I was taught in school to use a “cold sterilization” solution for reprocessing certain instruments. I see that this practice is not recommended in recent infection control guidelines. What is different today from years ago?
In healthcare settings, cold sterilization refers to the practice of immersion (liquid chemical) disinfection used to reprocess reusable instruments or items for patient care. This practice was not a true sterilization procedure which could be biologically monitored and is no longer appropriate for reprocessing heat-stable medical instruments. In addition, “chemical immersion sterilants” such as glutaraldehydes can be toxic and allergenic to those healthcare workers who use them. Dentistry has very little (if any) use for these types of chemical agents. As a result of improved technology and manufacturing, virtually every reusable dental instrument in current use is heat-stable, and thus, should be appropriately cleaned, wrapped, and sterilized between uses with a heat-based, biologically monitored sterilizer, such as an autoclave, unsaturated chemical vapor sterilizer, or dry heat sterilizer.

Question 2. After I use the alcohol-based hand antiseptic in my office, I notice that my hands feel slippery and do not feel clean. Why does that happen and what can I do to take remedy this?
Repeated use of high concentrations of alcohol found in available water-free hand sanitizers/antiseptics can have a drying effect on the skin. People with sensitive skin can be especially affected. For this reason, products tested and approved for routine use in health professional facilities contain emollients, such as glycerin or aloe vera. These important additives reduce the drying potential of the antimicrobial alcohol over time with repeated use. Some personnel may feel a “buildup” of these emollients after a few uses of the hand sanitizer since water is not involved in this hand hygiene process. If the presence of the film bothers them, they merely need to wash their hands with soap and water to remove it. There isn’t any hard and fast regulation about how often to wash the emollients off. It is up to the individual to determine the frequency, but keep in mind that they do help to keep the keratinized epithelium on hands intact.

Question 3. I received the hepatitis B vaccine in the late 1980s. I was tested to be sure that I had developed antibodies soon thereafter, and was found to be positive. I go for a blood check every few years and recently the results came back negative for antibodies. Do I need a booster?
As of this writing there is no recommendation for a hepatitis B vaccine booster dose. The important thing is that you were tested after receiving the 3-dose regimen, and demonstrated a positive protective serologic titer for anti-hepatitis B surface antibodies (anti-HBs). This titer can decline over a period of years when the person is not accidently exposed to the hepatitis B virus. Ongoing studies of persons who responded to the vaccine indicate that immunologic memory remains intact for at least 23 years conferring protection against clinical illness and chronic hepatitis B virus infection, even though anti-HBs levels might become low or decline below detectable levels. What is important here is that you did get tested for antibodies after receiving the vaccine series. That way you knew your immune system had responded. The fact that immunological memory is lasting more than 20 years (and still going) reinforces the long-term value of this important vaccine.

Question 4. I have a dental assistant who has been working in the profession for many years. She tells me that she really dislikes receiving injections. She does not want to receive the hepatitis B vaccine, even though I would pay for it. In her mind she assumes that she was exposed to “everything” years ago and does not need the vaccine. Can she refuse vaccination even though I am required to offer and provide it to her?
She does have the right to refuse the vaccination, but she should know that without the vaccination series or serologic evidence of prior infection, she remains at risk for occupational viral infection. Federal and State Occupational Safety and Health Association (OSHA) regulations consider hepatitis B vaccination one of the most important protective measures a health professional can have, and she is required to sign an informed refusal waiver if she does not want to receive it. However, please remember that if she changes her mind in the future, and is still working as your employee, you are required to pay for the vaccine.

Question 5. Do prescription glasses provide sufficient eye protection when treating patients?
The trend in personal eyewear has rapidly shifted in recent years to the use of smaller, designer-oriented frames. Many of these do not adequately cover the eyes to protect against the routine macroscopic and microscopic exposures that occur during dental patient treatment. Thus, while they may be fashionable, these glasses are not sufficient for protection of the healthcare worker. Health professionals were very compliant with using appropriate eyewear shortly after the initial federal OSHA regulations were published in December 1991. Over the years, however, as less and less ocular injuries and infections have been reported from occupational exposures, personnel have gradually forgotten about the serious ramifications that can occur after airborne exposure to tooth particles, restorative materials, and salivary droplets. Everyone should be reminded that the eyes are very susceptible to injury and that they need to be covered completely with eyewear that is designed to be large enough and includes side shields. If one still wants to wear personal glasses or contacts, disposable eyewear is available which is both easy to use and provides protection during patient care. The important message to take away from this is the necessity to protect the least protected part of the body during dental care—your eyes.

Question 6. Does the vaccine against 2009 to 2010 seasonal influenza also provide cross-protection against the A/H1N1 “swine” pandemic flu virus?
No, cross-protection is not provided between the 2009 and 2010 seasonal influenza and A/H1N1 pandemic vaccine preparations. The pandemic “swine flu” virus is very different genetically from seasonal types. The latter constantly change by a process called “antigenic drift.” This alteration results from minor point mutations in the viral genetic material during replication in host cells. As a consequence, these viruses can routinely change from one season to the next, or in some instances, even within a single flu season. In contrast, pandemic influenza strains arise from a different mechanism involving genetic recombination between multiple influenza A virus subtypes. This process, termed “antigenic shift,” occurs from influenza viruses from different species co-infecting the same animal host (ie, the pig), whose cells have receptors for human, bird, and swine flu viruses. Whole segments of viral nucleic acid can be exchanged in creating progeny viruses. The resultant viruses contain segments of RNA from each of the original viruses, are typically are completely different in their antigenic makeup from any previously known strain, and often are more virulent than seasonal flu viruses. When new influenza A viruses are introduced into the human population, infected persons have little or no protective immunity from previous exposure to other influenza viruses. In the worst case scenario, when these strains adapt to efficient human-to-human transmission, the potential for a widespread pandemic arises with a high mortality rate.

Question 7. Can injected seasonal influenza vaccines give you the flu?
No, the vaccine does not cause all people to develop influenza after immunization. Unfortunately, this is a common misconception concerning the efficacy and safety of flu vaccines. The influenza viruses used in vaccine preparations are grown in chick embryo tissue cultures and then harvested. These viruses are inactivated with formalin. These “killed” viruses are then split into components to yield the final preparation. Batches of vaccine are tested to ensure safety before they are approved for human immunization. According to the CDC, in randomized, blind investigations, where some participants received flu shots while others were injected with saline, the only difference in symptoms noted was an increase in soreness in the arm and injection site soreness among those who received the flu shot. No differences were noted between the 2 groups with regard to body aches, fever, cough, or sore throat.

Question 8. I have been receiving information about a new autoclave technology called Class B sterilizers. How do they work? Are they more efficient than the autoclaves currently in use?
This European-developed innovation in sterilizer technology arrived in the United States about 10 years ago and is suitable for all dental practices. While Class B sterilizers (also called prevacuum and postvacuum steam sterilizers) are similar to gravity displacement autoclaves (they use steam under pressure to sterilize contaminated items), they are also fitted with a pump that creates a vacuum in the chamber to ensure air is removed from the sterilizing chamber before steam enters. The advantage here is that very rapid steam penetration occurs throughout the chamber because the steam does not mix with air before reaching packaged instruments. As a result, there is faster and more thorough steam penetration throughout the entire load, with the result being a shortening of the required time for instrument sterilization. Class B sterilization cycles also can minimize a common problem seen in many practices: this is the issue of finding wet instrument packs at the end of a sterilization cycle which occurs when dental personnel overload the chamber prior to beginning the cycle. The pre and postvacuum autoclaves address this by having a poststerilization vacuum cycle that facilitates drying by removing steam at the end of the sterilization portion of the cycle. This important feature provides dry instrument packs at the end of the process. Although larger versions of these pre and postvacuum sterilizers have been available for a number of years in hospitals, dental schools, and large clinics, smaller tabletop units have become available in the United States in recent years and can be very useful as components of an efficient instrument reprocessing protocol.

Question 9. There are numerous barriers, sprays, and wipes available for accomplishing effective environmental surface infection control. What are some of the mistakes that can occur in this area, thereby compromising the effectiveness of the procedures used to accomplish surface asepsis?

Representative problems can include:
a. Not cleaning contaminated surfaces prior to disinfection. The importance of initial cleaning cannot be overemphasized, as it is included routinely in all published infection control recommendations. Cleaning is the physical removal of debris which also results in reduction of the number of microorganisms present on the inanimate surface.
b. Reuse of barriers sold as single-use items.
c. Use of inappropriate products as surface disinfectants. Some individuals previously proposed the use of glutaraldehydes (ie, high-level disinfectants) on contaminated environmental surfaces. This would constitute a potentially harmful misuse of this immersion type of chemical. These solutions are not manufactured to be used as surface disinfectants and can pose significant health risks for healthcare personnel who spray them onto surfaces.
d. Mistakenly substituting products that have not been tested and approved for use in healthcare facilities. Household cleaners and sanitizers do not undergo the same rigorous testing, quality control, and Environmental Protection Agency (EPA) approval process as those that are approved for use in dental and medical settings. Manufacturers of surface disinfectant sprays and disposable wipes must conduct a number of required independent laboratory, toxicity, and compatibility studies as part of the EPA evaluation process.
e. Over spraying of disinfectants. Misuse/overuse of disinfectants can occur in several ways. Operatory surfaces that are repeatedly overexposed to chemicals can discolor, or equipment can be damaged. An even more serious problem can arise in addition to equipment damage, whereby personnel can develop respiratory symptoms, such as sneezing or wheezing when the chemical disinfectant is sprayed. Ocular irritation, headaches, and even allergies to the chemical can also occur from excessive spraying.
The bottom line here is to be certain to read and follow the manufacturer’s product label. The content of the label also needs to be approved by the EPA before the product receives an EPA number.

CLOSING COMMENTS
In summary, I am reminded of a question that was posed to me recently. The question was: What advice can dental professionals use concerning the implementation and maintenance of a practical infection control program? The bottom line for many aspects of an effective program is to use common sense. You can readily get confused with some of the rhetoric, available products, and “improved” technologies. It is important to focus on what you are trying to accomplish.

References

1. Kohn WG, Collins AS, Cleveland JL, et al, and the Centers for Disease Control and Prevention (CDC). Guidelines for infection control in dental health-care settings—2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.
2. Siew C, Gruninger SE, Miaw CL, et al. Percutaneous injuries in practicing dentists. A prospective study using a 20-day diary. J Am Dent Assoc. 1995;126:1227-1234.
3. McCarthy GM, Koval JJ, MacDonald JK, et al. Compliance with recommended infection control procedures among Canadian dentists: results of a national survey. Am J Infect Control. 1999;27:377-384.
4. Bischoff WE, Reynolds TM, Sessler CN, et al. Handwashing compliance by health care workers: The impact of introducing an accessible, alcohol-based hand antiseptic. Arch Intern Med. 2000;160:1017-1021.

Dr. Molinari is currently Director of Infection Control for THE DENTAL ADVISOR in Ann Arbor, Mich. Previously, he was a full-time faculty member at the University of Detroit Mercy School of Dentistry for 32 years, where he served as Professor and Chair of the Department of Biomedical Sciences. He has published more than 350 scientific articles, text chapters, and abstracts in the areas of microbiology and immunology, and lectures nationally and internationally on topics dealing with infectious diseases and infection control. Dr. Molinari is also co-author of the text Cottone’s Practical Infection Control in Dentistry, with the third edition published in 2009. His activities also include serving as a consultant for the CDC, ADA Council on Scientific Affairs, Council on Dental Practice, and hospitals in the Detroit area in the areas of infectious disease and infection control Dental Association. He can be reached at johnmolinariphd@gmail.com. 

Disclosure: Dr. Molinari is a consultant for Hu-Friedy Manufacturing and SciCan.

This article reviews environmental surface asepsis, including the materials and methods used for surface disinfection.

ENVIRONMENTAL SURFACES

There are 2 types of dental environmental surfaces: clinical contact surfaces and housekeeping surfaces. Clinical contact surfaces are touched frequently with gloved hands during patient care, or may become contaminated with blood, saliva, or other potentially infectious material and then come in contact with instruments, devices, hands, or gloves. Housekeeping surfaces (eg, floors, walls, and sinks) do not come in contact with hands or devices used in dental procedures. Proper treatment of clinical contact surfaces is required before they become involved in the care of the next patient. Treatment of housekeeping surfaces can occur at the end of the day.^1-3

There are 2 general approaches to environmental surface asepsis (Table 1). One way to prevent contamination is with the use of surface covers. The other approach is to preclean and disinfect surfaces after contamination and before reuse. Each approach has advantages and disadvantages. Dental practices usually employ a combination of both.^1-3

Surface covers take little time to place, cover surfaces difficult or impossible to disinfect, and reduce the exposure of workers to chemicals. Covers can be demanding, as a variety of sizes and shapes may be required, and may be aesthetically unattractive.^1-3

Disinfection may be less expensive than covering, involves processes familiar to practitioners, and produces less waste material. Disinfection increases practitioner exposure to chemicals and requires that personal protective equipment (PPE) such as masks and protective eyewear be worn. Some chemicals need to be mixed in a specific manner and prepared daily. All chemicals have to be stored correctly with proper labeling, and material safety data sheets should be easily accessible for reference.^1-4

MICROORGANISMS

Because Mycobacterium tuberculosis is more difficult to kill than most other microorganisms, disinfectants with tuberculocidal activity are acceptable for use in most situations in dentistry. Tuberculocidal agents are usually effective against nonenveloped (hydrophilic, such as poliovirus) and enveloped (lipophilic, such as herpes virus, influenza, and HIV) viruses.^1-4

Different microorganisms survive on environmental surfaces for widely varying amounts of time. Factors influencing survival include temperature, humidity, inoculating dose, and the presence of blood and saliva. Thus, predicting the number and types of microorganisms present on a contaminated surface is impossible. The safest approach is to assume that any contamination contains viable microorganisms. Removal and/or killing of microorganisms before treatment of the next patient are thus required.

PRECLEANING

Precleaning and disinfection best occur on smooth, easily accessible, nonporous surfaces. These types of surfaces best afford good contact with decontaminating chemicals. Proper precleaning (predisinfection) is essential to reduce the bioburden present initially, so that disinfection will have a better chance to kill a reduced number of residual microorganisms.

The practitioner should always check the surface-cleaning ability of an agent. Water-based agents solubilize organic materials such as blood and saliva. Precleaning agents are often the same chemical used for disinfection.

Not all contaminated surfaces in dental practices can be precleaned and/or disinfected well or easily. Buttons, control switches, and drawer pulls are examples of difficult-to-clean items and are best covered with a barrier.

The practitioner should always wear PPE when disinfecting surfaces and equipment. This includes utility gloves (not clinical-use gloves), masks, protective eyewear, and protective clothing. Proper use will minimize worker contact with both contaminants and chemicals.

SURFACE DISINFECTION

After properly precleaning, surfaces are ready for disinfection. The most frequently used method of disinfection is the spray-wipe-spray technique, but wiping surfaces with disinfectant wipes or towelettes is equally effective. Spray-wipe is the precleaning step, while the second spray is disinfection. Complete coverage of surfaces is required. Sur-faces need to remain moist for the longest contact time (usually 5 to 10 minutes) indicated by the manufacturer. Removal of residual moisture is accomplished with a paper towel. Alternatively, premoistened disinfectant wipes can be used.

Intermediate-level disinfection is required to treat clinical contact surfaces in dentistry. Such agents can destroy vegetative bacteria, which include most fungi and viruses. They can also inactivate Mycobacterium bovis (tuberculocidal) in 10 minutes of exposure or less. Disinfectant containers must have an EPA registration number. Examples of these agents include chlorine-based products, phenolics, iodophors, quaternary ammonium compounds with alcohol, and bromides.

Antimicrobial chemicals come in 4 general types: (1) antibiotics (for killing microorganisms in or on the body); (2) antiseptics (for killing microorganisms on the skin or other body surfaces); (3) disinfectants (for killing microorganisms on environmental/inanimate surfaces or objects), and (4) sterilants (for killing all microorganisms on inanimate objects).¹

The Centers for Disease Control and Prevention have categorized disinfectants based on their microbial spectrum of activity (Table 2). The categories include the following: sterilant/high-level disinfectant (for killing all microorganisms on submerged inanimate objects that are heat sensitive); intermediate-level disinfectant (for killing vegetative bacteria, most fungi, and M. tuberculosis); and low-level disinfectant (for killing most vegetative bacteria, some fungi, and some viruses).^1,2

SUMMARY

Environmental surface disinfection is easily accomplished with precleaning and disinfection techniques, and prepared surfaces or difficult-to-clean items can be covered with impermeable barriers. When carried out effectively, both practitioners and patients are protected from exposure to microorganisms that transmit disease and cause illness.

References

1. Miller CH, Palenik CJ. Infection Control & Management of Hazardous Materials for the Dental Team. 3rd ed. St Louis, Mo: Mosby-Year Book; 2004:260-275.

2. Kohn WG, Collins AS, Cleveland JL, et al. Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings – 2003. MMWR Recomm Rep. 2003;52(RR-17):1-61.

3. Organization for Safety & Asepsis Procedures. From Policy to Practice: OSAP’s Guide to the Guidelines. Annapolis, Md: OSAP; 2004:45-62.

4. Organization for Safety & Asepsis Procedures. Surface disinfectants for dentistry: tools for selecting and using surface disinfectants in dental settings. Infection Control In Practice. May 2005; Vol 4:1-4.

Dr. Palenik has held over the last 25 years a number of academic and administrative positions at Indiana University School of Dentistry. These include professor of oral microbiology, director of human health and safety, director of central sterilization services, and chairman of infection control and hazardous materials management committees. Currently he is director of infection control research and services. Dr. Palenik has published 175 articles, more than 305 monographs, 3 books, and 7 book chapters, the majority of which involve infection control and human safety and health. Also, he has provided more than 100 continuing education courses throughout the United States and 8 foreign countries. All questions should be directed to OSAP at office@osap.org.

BACKGROUND
In humans, TSE may present as Creutzfeldt-Jakob disease (CJD). Three known transmission methods exist for this disease: sporadic, familial, and acquired. In sporadic CJD, the disease appears even though the person has no known risk factors for the disease. This is by far the most common type of CJD and accounts for at least 85% of cases.
In hereditary CJD, the person has a family history of the disease and/or tests positive for a genetic mutation associated with CJD. About 5% to 10% of cases of CJD in the United States are hereditary.
Transmission of acquired CJD is by exposure to brain or nervous system tissue, usually during certain medical procedures (iatrogenic). There is no evidence that CJD is contagious through casual contact with a CJD patient. Since 1920, less than 1% of cases have been acquired CJD.

Mad Cow Disease and CJD
In 1986, prions were introduced to the public when an outbreak of bovine spongiform encephalopathy (BSE), commonly called “mad cow disease,” occurred in Great Britain. Cows became mysteriously ill with a disease that caused them to wobble, stagger, and appear fearful. Ultimately the cows died, and it was determined that they were suffering from BSE.
Alarmingly, approximately a decade later, 10 people in Great Britain developed Creutzfeldt-Jakob disease that did not present in the classical manner previously observed in humans. Sporadic cases of CJD had been observed for many years, with a worldwide death rate of approximately one case per million people per year. It is mostly observed in people age 55 to 75 years old. The cases in Great Britain were in young adults, all of whom had consumed beef from cows infected with BSE. These cases were termed variant CJD (vCJD) because they were not the sporadic, familial, or iatrogenic cases that had been believed to be the only forms of the disease. It is believed the infection spread to the cattle from feed derived from sheep infected with scrapie. During the slaughtering of cows and processing of beef, it is possible to contaminate the beef with brain material or other central nervous system (CNS) material that harbors prions. To date, public health authorities have identified 143 people in Great Britain and 10 elsewhere as suffering from vCJD related to BSE-infected meat (Table 2).²

INFECTION CONTROL CONSIDERATIONS

Iatrogenic transmission of CJD has been reported in more than 250 patients worldwide. These cases have been linked to the use of contaminated human growth hormone, dura mater, corneal grafts, or neurosurgical equipment. Of the 6 cases linked to the use of contaminated equipment, 4 were associated with neurosurgical instruments and 2 with stereotactic EEG depth electrodes.³ All of these equipment-related cases occurred before the routine implementation of sterilization procedures currently used in healthcare facilities. Such cases have not been reported since 1976, and no iatrogenic CJD cases associated with exposure to the CJD agent from surfaces such as floors, walls, or countertops have been identified.
In determining the need for special infection control measures, it is important to understand that the likelihood of transmission is related to the type of medical treatment being rendered and what human tissues or body fluids contaminate the instruments (Table 3). There is no evidence to suggest that dental instruments and procedures carry a risk for iatrogenic transmission of CJD. The strongest evidence for a low or negligible risk comes from an Australian case-control study reported in Lancet.⁴ This study found no association between the development of sporadic CJD among 241 cases with having major dental work, defined as treatment beyond fillings and dental hygiene such as root canals and tooth extractions.
The Centers for Disease Control and Prevention (CDC) issued new infection control guidelines for dentistry in December 2003. In the guidelines, the issue of infectivity of oral tissues for CJD remains an unresolved issue. The guidelines state: “…CJD was not associated with dental procedures (eg, root canals or extractions), with convincing evidence of prion detection in blood, saliva, or oral tissues, or with DHCP becoming occupationally infected with CJD.”⁵ The guidelines offer no recommendations due to the lack of evidence for precautions beyond standard precautions.
The transmissions of CJD that have occurred in healthcare settings are associated with exposure to infected central nervous tissue (eg, brain and dura mater), pituitary tissue, or eye tissue. Although the CDC makes no recommendations for special precautions in dentistry, it offers for consideration the following list of precautions in the guidelines:

• “Use single-use disposable items and equipment whenever possible.
• Consider items difficult to clean (eg, endodontic files, broaches, and carbide and diamond burs) as single-use disposables and discard after one use.
• To minimize drying of tissues and body fluids on a device, keep the instrument moist until cleaned and decontaminated.
• Clean instruments thoroughly and steam-autoclave at 134°C for 18 minutes. This is the least stringent of sterilization methods offered by the World Health Organization. The complete list is available at who.int/emc-documents/tse/
  whocdscraph2003c.html.
• Do not use flash sterilization for processing instruments or devices.”
  The relative rarity of CJD and absence of vCJD in the United States indicates this fatal disease does not present a high risk of patient-to-patient or patient-to-healthcare worker transmission in the dental setting. (One person in the United States was identified postmortem of having suffered from vCJD. However, that individual had lived in Britain during the time infected beef was consumed.) As the science progresses and new infection control guidelines emerge, it will be important for dental workers to ensure they understand the transmission of all emerging diseases.

References

1. Belay ED. Prions and prion diseases: current perspectives [book review]. Emerg Infect Dis. [serial online] Dec 2004. Available at: http://www.cdc.gov/ncidod/EID/vol10no12/04-0847.htm. Accessed February 18, 2005.
2. Brown P, Will RG, Bradley R, et al. Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: background, evolution, and current concerns. Emerg Infect Dis. 2001;7:6-16.Available at: http://www.cdc.gov/ncidod/EID/vol7no1/brownG.htm. Accesed on Feb 28, 2005.
3. World Health Organization. WHO Infection Control Guidelines for Transmissible Spongiform Enceph-alopathies. Report of a WHO Consultation; Geneva, Switzerland; 23-26 March 1999. Communicable Disease Surveillance & Response Web site. Available at: http://www.who.int/emc-documents/tse/whocdscsraph2003c.html. Accessed February 24, 2005.
4. Collins S, Law MG, Fletcher A, et al. Surgical treatment and risk of sporadic Creutzfeldt-Jakob disease: a case-control study. Lancet. 1999;353:693-697.
5. Kohn WG, Collins AS, Cleveland JL, et al. Guidelines for infection control in dental health-care settings – 2003. MMWR Recomm Rep. 2003;52(No. RR-17):1-61.

Acknowledgement
The author would like to thank Dr. Jennifer Cleveland of the CDC division of oral health for her expertise and assistance with this article.

Ms. Cuny is the director of environmental health and safety and assistant professor in the department of pathology and medicine at the University of the Pacific School of Dentistry. She is past chairman of the Organization for Safety and Asepsis Procedures (OSAP). She can be reached at ecuny@pacific.edu.

PRACTICE/LABORATORY RELATIONSHIPS
Effective communication and coordination between dental laboratories and practices will help ensure the performance of appropriate cleaning and disinfection procedures, that damage to materials does not occur, and unnecessary duplication of effective methods does not happen. If contaminated items were to enter the laboratory environment, this could lead to the spread of contaminants to the prostheses and appliances of other patients. This could also place unsuspecting laboratory personnel at increased risk for cross-infection.^1-3
When sending a laboratory case off site, DHCP should provide written information regarding the methods used (eg, type of disinfectant used and exposure time) to clean and disinfect an item (eg, impression, stone model, or appliance). In addition, clinical materials not properly decontaminated are subject to OSHA and US Department of Transportation regulations concerning transport and shipping of infectious materials.¹
All items coming from the oral cavity must be sterilized or disinfected properly before work starts in the laboratory and then again prior to their return to patients. Communication between the laboratory and the dental practice must identify which party will be responsible for the final disinfection process. Asepsis procedures vary for each type of dental material. However, general recommendations as to procedures and materials are possible.^1-3
If the dental laboratory provides disinfection, the use of an EPA-registered, intermediate-level disinfectant is required, written documentation of the disinfection method must be provided, and the item should be placed in a tamper-evident container before returning it to the dental office. If provision of such documentation is not present, then the dental office is responsible for the final disinfection procedures.^1-3

Whether in a dental practice or an off-site dental laboratory, wearing of personal protective equipment (PPE) is necessary when handling laboratory cases not yet disinfected. PPE generally includes chemical resistant utility gloves, eye/face protection, surgical masks, and lab coats or clinical jackets.3

RECEIVING AREAS
Dental practices should create separate receiving and cleaning/disinfecting areas to handle all items sent to an off-site laboratory or when dealing with the items in a laboratory within the practice. The area needs running water and handwashing facilities. Impervious paper should cover work areas. Also needed are regular cleaning and disinfection. The amount of cleaning and disinfection depends on the overall usage of the work areas.²
No item (impression or prostheses) should enter the practice’s receiving area unless properly disinfected. Contamination of such items with oral and bloodborne pathogens occurs. Dental prostheses, impressions, orthodontic appliances, and other prosthodontic materials (eg, occlusal rims, temporary prostheses, and bite registrations) need thorough cleaning (removal of blood and bioburden removal), disinfection with an EPA-registered, intermediate-level disinfectant (with a tuberculocidal claim), followed by a thorough rinsing prior to handling in the practice laboratory or being sent to an off-site laboratory.^1-3
The ideal time to clean and disinfect impressions, appliances, and prostheses is as soon as possible after removal from the oral cavity before drying of blood and bioburden can occur. If cleaning and disinfection does not completely remove all visible blood and bioburden, then repeat asepsis procedures.^1-3

DISINFECTING IMPRESSIONS
There is ample documentation of the transfer of microorganisms onto and into impressions. Organisms can also move into dental casts. Some of these organisms can remain viable for up to 7 days. Again, wearing of proper PPE is required. Incorrect handling of contaminated impressions and casts offers the opportunity for transmission of microorganisms.^1-3
There are several steps for properly disinfecting dental impressions:^1-3

• after removal from the oral cavity, rinse impressions under running tap water and shake gently to remove adherent water; sometimes soft, camel-hair brushes can help remove debris;
• disinfect impressions using an intermediate-level, EPA-registered disinfectant for the contact time recommended by the manufacturer (usually about 15 minutes);
• after the proper exposure time, the impressions are rinsed under running tap water and gently shaken to remove adherent water; and
• properly disinfected and dried impressions are ready for pouring.

Rinsing helps in the removal of adherent microorganisms. Immersion helps ensure complete contact between all impression surfaces and disinfectant. Immersion can occur in glass beakers, plastic containers, and even zipper-seal bags. Unless specifically approved for reuse, germicides are single-use solutions.^1-3
Some types of impression materials are sensitive to im-mersion. Careful selection of disinfectants is required (Table). Spraying has several advantages. Spraying is the treatment of choice for some impression types; it uses less disinfectant and often is the same disinfectant that a practice uses for environmental surface disinfection. Spraying is technique sensitive. Disinfectant must contact all impression surfaces. Spraying also releases disinfectant into the air, thus increasing the chance of personal exposure. Most disinfectants (except glutaraldehydes) are appropriate for spraying.²
Disinfection of impression materials is an area of continuing research. Disinfection in certain types of chemical solutions harms some impression materials. Other types of disinfectants are safe to use on the same impression materials. Research indicates that variations in response within a given type of impression material (eg, alginate) can occur de-pending on the manufacturer.²

DISINFECTING PROSTHESES
Any prosthesis from the oral cavity is a potential source of infection. Most prostheses and appliances cannot withstand standard heat sterilization procedures. An alternative technique would be disinfection by immersion following a thorough cleaning. An intermediate-level disinfectant (tuberculocidal claim) should be used before an appliance is handled or worked upon in the practice laboratory or in an off-site commercial laboratory.²
Some heavily soiled (eg, calculus or adhesive) prostheses require cleaning or scrubbing before disinfection. The most efficient (and safest) pro-cedure is to place the prosthesis into a zippered plastic bag that contains ultrasonic detergent or another type of specialized cleaning solution. The bag is then placed in the chamber of an ultrasonic cleaner. The best cleaning action occurs in the middle of the cleaning chamber. Poorer cleaning occurs near the top and bottom of the solution pool. Bags can also be held in place by allowing the lip to pinch a corner.²
Sometimes further cleaning by hand is required. Air-powdered blasters, such as shell blasters, should only be used on cleaned and disinfected appliances.²

GRINDING, POLISHING,AND BLASTING
Bringing untreated appliances into a laboratory establishes the potential for cross-infection. Operation of a dental lathe provides an opportunity for the spread of infection and for injury. The rotary action of wheels, stones, burs, and bands generates aerosols, spatter, and projectiles. Whenever using a lathe, the Plexiglas front shield should be in place and the ventilation system operating. The use of masks would be helpful. The air-suction motor should be capable of producing an air velocity of at least 200 ft/min.²
All laboratory items such as burs, polishing points, brushes, rag wheels, stones, and laboratory knives used on contaminated or potentially contaminated materials should be heat sterilized, if possible. If items are heat sensitive and/or do not frequently contact the patient, prosthetic device, or appliance, yet frequently become contaminated (eg, articulators, case pans, and lathes), cleaning and proper disinfection are required. Pressure pots and water baths are especially susceptible to contamination and should al-ways be cleaned and disinfected between patient uses. Many laboratory items now come as single-use, disposable items.^1-3
Polishing appliances and prostheses is a necessary activity. To avoid potential cross-infection, several steps are required:²

• using fresh pumice and pan liners for each new case;
• always having the lathe’s protective front shield in place and ventilation system operating;
• obtaining only small amounts (unit doses) of polishing agents (eg, rouge) from larger reservoirs;
• trying to employ single-use, disposable items as much as possible;
• heat sterilizing as many items (including rag wheels, which can be rinsed out and steam autoclaved) as possible;
• properly disinfecting other items; and
• following manufacturer recommendations.

Environmental surfaces are best covered. If not, then they need to be cleaned and disinfected regularly with an EPA-registered, intermediate-level disinfectant. Most laboratory waste can be disposed with the regular practice trash. Sharp items (eg, burs, disposable blades, and orthodontic wires) must be placed into “sharps” containers.²
The Organization for Safety and Asepsis Procedures (OSAP) is dentistry’s source for evidence-based information on infection control and prevention and human safety and health. Further information concerning dental laboratory asepsis is available on the OSAP Web site at osap.org.

References

1. Kohn WG, Collins AS, Cleveland JL, et al; Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings – 2003. MMWR Recomm Rep. 2003;52(RR-17):1-66. Also available at: http://www.cdc.gov/mmwr/pdf/rr/rr5217.pdf. Accessed December 2004.
2. Miller CH, Palenik CJ. Infection Control and Management of Hazardous Materials for the Dental Team. 3rd ed. St Louis, Mo: Mosby Year-Book; 2004.
3. Organization for Safety & Asepsis Procedures. From Policy to Practice: OSAP’s Guide to the Guidelines. Annapolis, Md: OSAP; 2004.

Dr. Palenik has held over the last 25 years a number of academic and administrative positions at Indiana University School of Dentistry. These include professor of oral microbiology, director of human health and safety, director of central sterilization services, and chairman of infection control and hazardous materials management committees. Currently he is director of infection control research and services. Dr. Palenik has published 125 articles, more than 290 monographs, 3 books, and 7 book chapters, the majority of which involve infection control and human safety and health. Also, he has provided more than 100 continuing education courses throughout the United States and 8 foreign countries. All questions should be directed to OSAP at office@osap.org.

CATEGORIES OF PATIENT CARE ITEMS

The Centers for Disease Control and Prevention (CDC) has categorized patient care items as critical, semicritical, or noncritical based on the potential risk of infection to the patient during use. The system is based on the classification first proposed by Spaulding in 1968 (Table 1). The CDC recommends that critical and semicritical items be first cleaned and then sterilized by heat.^1,4
Semicritical items that are heat sensitive must, at a minimum, be cleaned and treated with a high-level disinfectant. Noncritical items are cleaned and treated with a low-level disinfectant when no blood is visible. Intermediate-level disinfectants are to be used when blood can be seen.^1,2

CHAIRSIDE AND TRANSPORT

Operatory preparation for the next patient cannot begin until all contaminated items are safely removed, discarded, or processed. The removal of contaminated patient care items from the operatory should be performed in a careful manner to prevent exposure to microorganisms. Contact with nonintact skin on the hands, mucous membranes of the eyes, nose, or mouth, and percutaneous injuries from sharp instruments provide the risk of disease transmission. Instruments being transported to the instrument-processing area must be contained to prevent injury. Containment can be defined as instrument cassettes or cages in which dental care items are cleaned, sterilized, and stored until point of use. Sharp instruments should not be carried openly to the instrument-processing area. Percutaneous injuries may occur to other dental healthcare personnel (DHCP) or patients in hallways leading to the instrument-processing area.

HOLDING/PRESOAKING

If the DHCP are unable to begin the instrument-processing procedure immediately after transporting the dental care items to the instrument-processing area, the items should be placed into a holding solution in a puncture-resistant container for a precleaning process. This facilitates the cleaning process by preventing patient material from drying on the instruments. Cleaning becomes easier and less time consuming. The holding solution can be a disinfectant/detergent or an enzymatic cleaner. The use of a sterilant/high-level disinfectant (eg, glutaraldehyde) is not considered appropriate and therefore not recommended. Some plastic/resin cassettes should not be placed into a holding solution. Always consult and follow the recommendations made by the cassette manufacturer. Also, be aware that some instruments may corrode if left in the holding solution for more than a few hours. Precleaning is not required when using an instrument washer. Contaminated instruments may be placed directly into the instrument washer and held there until the washer cycle is started.

CLEANING

Cleaning soiled dental instruments is essential for any sterilization procedures. Cleaning reduces the bioburden (microorganisms, blood, saliva, oral hard tissues, and dental materials). Bioburden could isolate or protect microorganisms from sterilizing agents. There are 2 ways to clean dental instruments: mechanically (ultrasonic cleaning, instrument wash-ers/washer-disinfectors) and manually.^1-3

Ultrasonic Cleaning

Ultrasonic cleaning, when com-pared to manual scrubbing, reduces direct contact with contaminated instruments and thus decreases the chances of cuts and puncture wounds. Ultrasound, because of its cavitation action (billions of imploding bubbles are generated, which produce a cleaning turbulence that removes and disrupts debris), is usually more effective and efficient than manual scrubbing. For example, office staff can properly clean more instruments within a given period of time. Almost all instruments can be ultrasonically cleaned. One major exception is the majority of dental handpieces, which usually must be hand-cleaned. Both loose instruments and those held in cassettes can be cleaned with ultrasound. Always check the manufacturer’s clean-ing instructions.^2,3,5

Ultrasonic cleaners come in a variety of sizes, from pint-sized round units to multiple-gallon, rectangular-shaped types that can be used on a countertop or built into the counter cabinet (Table 2).

Loose instruments and those held within cassettes must be suspended within the solution but off the bottom of the unit’s chamber (Table 3). Placement of instruments directly on the floor of the unit will result in poor cleaning, and excessive bouncing could damage the unit and the instruments. The use of a suspending basket or rack will position the instruments or cassettes for optimal cleaning. A cover should be in place whenever the unit is being operated.
The unit’s chamber should be filled (usually within 0.5 to 1 inch of the top) with a detergent solution designed for use in an ultrasonic cleaner. Although these detergents are more expensive than those used in household situations, they are more economical in the long run. Ultrasonic detergents have operational pH levels that will not harm instrument metals and are capable of producing cavitation for extended periods.
One can readily test the function of an ultrasonic cleaner using a process called the aluminum foil test. First, cut a piece of lightweight foil about an inch shorter than the length of the chamber. The foil should be about an inch longer than the depth of the chamber. Place the foil sheet as vertically as possible into a filled chamber without touching any sides. The bottom of the foil should be at least an inch above the floor of the unit. Operate the unit for 30 seconds. Remove the foil and observe for small indentations (pebbling) or even holes in or on the foil. The pebbling should be distributed fairly evenly over the surface of the foil. If there are areas greater than a half-inch without pebbling, the unit may need repair. The manufacturer of specific units may have aluminum foil tests similar to the one just described. In such cases, users should follow those directions.^2,5,6

Instrument Washers

Another method of mechanical instrument cleaning is an in-strument washer (sometimes called “a washer-disinfector”). These units have been used in hospitals and larger clinics, and have become available to dental offices.
Washers clean instruments with hot water-detergent sprays followed by high-pressure spray rinses. Washers should be manufactured specifically for use on medical/dental instruments. Those designed for household applications should not be used.
Washers tend to be large and usually can accommodate many instrument cassettes (and loose instruments). A normal cleaning cycle contains multiple episodes of washing and rinsing, often taking as much as an hour to complete. Operation of washers, including selection of cleaning
solutions, is usually well-described by the manufacturers.

Manual Scrubbing

Scrubbing instruments by hand is a traditional method of cleaning and is a relatively effective method for removing debris (Table 4). However, scrubbing is dangerous and is not as effective as mechanical methods of cleaning.
In cases of very adherent materials, handscrubbing may be required to clean some instruments properly. Routine manual scrubbing of all instruments prior to sterilization, however, cannot be recommended. Handscrubbing requires direct contact with contaminated instruments, thus increasing the chances of occupational exposures, even while wearing utility gloves. Today, mechanical cleaners are very effective, thus there is no need to scrub instruments manually prior to placement in an ultrasonic cleaner or instrument washer.^2,3,5 Also, staff can perform other instrument recycling tasks while ultrasonic or machine cleaning is being performed.
After cleaning, instruments should look clean (free of debris). However, they must be considered as still being microbially contaminated (nonsterile). This means that personal protective equipment must be worn when handling these items. Exposure to nonsterile (albeit clean) instruments either through mucous membrane or percutaneous accident is a serious matter. Dental offices must prepare a formal, written policy concerning postexposure procedures. All office staff members must be knowledgeable as to what constitutes an exposure and what specific steps must be followed in case of an accident.²

CORROSION CONTROL/ DRYING/LUBRICATION

After cleaning, instruments and instrument cassettes should be rinsed well. Some cleaning units (eg, instrument washing machines) have automatic rinsing cycles. After rinsing, instruments and cassettes should be allowed to drain and ideally to dry completely. Shaking the instruments and cassettes can accelerate this process. However, care must be taken so the instruments are not damaged. Drying instruments by hand using some type of toweling materials must be done carefully. Some instruments (eg, hinged types) require lubrication in order to function properly.
Even though the instruments have been cleaned, they are not sterile. They must be handled using appropriate personal protective equipment. This would include utility gloves, protective eyewear, and gowns.
The physical integrity of the instruments can now be determined. Damaged items can be removed and replaced. Carbon steel is susceptible to rusting and dulling when processed in a steam autoclave. Carbon steel is common in dental burs, on the cutting/scraping edges of some instruments (eg, orthodontic pliers, scalers, and hatchets), and the grasping surfaces of forceps.
Rust-inhibiting solutions (eg, those containing sodium nitrite) can be sprayed on instruments prior to processing in a steam autoclave. Such solutions can also be used as instrument dips (“milks”). The usual result is a reduction in instrument rusting. An alternative to using a rust inhibitor would be to dry the cleaned instruments carefully and process them either in a dry-heat oven or an unsaturated chemical vapor sterilizer.^1-5

PACKAGING

The goal of sterilization is more than just sterilizing instruments between patients; it is delivering sterile instruments chairside every time they are to be used. Proper cleaning is important, but so is maintaining sterility of instruments after they have been processed through the sterilizer. Packaging instruments before processing will help keep them from being contaminated while being stored or when they are transported chairside for use. Unpackaged instruments have no practical shelf-life. Instruments processed without protective packaging can be readily contaminated after processing.²
Packaging is not only protective, but also serves as an organizational tool. Packaging places instruments into functional sets or groupings. Chemical monitors can also be incorporated into packaging materials. Also, biological monitors are easily placed and held within pouches, bags, trays, or cassettes.²

Only packaging materials that have been designed for use in sterilizers should be used. Packaging is considered to be a medical device and thus is regulated by the Food and Drug Administration for effectiveness and efficiency. Also, packaging must be appropriate for the type of sterilizer used (Table 5). Improper packaging may retard sterilization, be destroyed during processing, or even release toxic chemicals with the application of heat.
One form of packaging that is becoming increasingly popular is the instrument cassette. Cassettes reduce the direct handling of contaminated instruments and keep instruments together during the entire sterilization process (cleaning, rinsing, drying, and wrapping). Cassettes easily fit into instrument washers, which often are large and can accommodate 5 to 10 in a single cycle. Also, after sterilization, cassettes are easy to store by stacking. Cassettes can also be run through ultrasonic cleaners. However, the proper sized units must be used. Cassettes are made of a variety of materials (stainless steel, aluminum, and plastic/resin) and can withstand steam, chemical vapor, and dry heat sterilization.²

CONCLUSION

The Organization for Safety and Asepsis Procedures (OSAP) is dentistry’s resource for infection control and safety. OSAP has recently published a book on the CDC guidelines—From Policy to Practice: OSAP’s Guide to the Guide-lines. The book is designed to support the efforts of dental practices to understand better the recommendations and to identify effective and efficient methods for compliance, including preparation of instruments for sterilization. Order information is available at osap.org or by calling (410) 571-0003.

References

1. Kohn WG, Collins AS, Cleveland JL, et al; Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings, 2003. MMWR. 2003;52(RR-17):1-61.
2. Miller CH, Palenik CJ. Infection Control and Management of Hazardous Materials for the Dental Team. 3rd ed. St Louis, Mo: Elsevier Mosby; 2005:191-250.
3. Organization for Safety and Aseptic Procedures. From Policy to Practice: OSAP’s Guide to the Guidelines. Annapolis, Md: OSAP; 2004:45-62.
4. Spaulding EH. Chemical disinfection of medical and surgical materials. In: Lawrence CA, Block SS. Disinfection, Sterilization and Preservation. Philadelphia, Pa: Lea & Febiger; 1968:517-531.
5. Palenik CJ. Dental instrument sterilization: a six-step process. J Contemp Dent Pract. 2001;2:84-96.
6. Jorgensen G, Palenik CJ. Instrument sterilization. Dent Equip & Materials. 2004;9:69-71.

Ms. Jorgensen has been employed as an orthodontic assistant, a general chairside assistant, and a trainer for a large group practice. Currently, she is a full-time, clinical procedures, dental assisting instructor at Portland Community College in Portland, Ore. She is an approved speaker on bloodborne pathogens for the National Association of Dental Laboratories (NADL) and is a member of The Dental Assisting National Board, Infection Control Exam (ICE) test construction committee. She can be reached at (503) 977-4036 or gjorgens@pcc.edu.

Dr. Palenik has held over the last 25 years a number of academic and administrative positions at Indiana University School of Dentistry. These include professor of oral microbiology, director of human health and safety, director of central sterilization services, and chairman of infection control and hazardous materials management committees. Currently he is director of infection control research and services. Dr. Palenik has published 125 articles, more than 290 monographs, 3 books, and 7 book chapters, the majority of which involve infection control and human safety and health. Also, he has provided more than 100 continuing education courses throughout the United States and 8 foreign countries. All questions should be directed to OSAP at office@osap.org.