Certain glass polyalkenoate (ionomer) systems have proven to be excellent dentin replacement liners and bases for decades in biomimetic stratification tooth repair.¹ The resin-modified glass-ionomer cements, particularly, are well suited to that purpose. Now there is a worthy alternative. Since its introduction in January 2021, TheraBase (BISCO) has been proving itself as an excellent radiopaque, bonded dentin replacement base/liner.² The company refers to the material as a “dual-cured, calcium- and fluoride-releasing base, self-adhesive base/liner.” TheraBase is packaged in a double-barrel syringe with a self-mixing delivery tip that is used to inject material directly into a cavity preparation. Another method of delivery comes from mixing pad spatulation and using the AccuDose syringe system (CENTRIX). Simulated delivery of the material and photo-polymerization in an extracted molar is shown in Figures 1 to 3.  

Figure 1. Beginning injection with the double-barreled delivery/mixing system in an extracted tooth simulation.

Figure 2. Injection of TheraBase (BISCO) to overfill to serve as a dentin/enamel interim restoration.

Figure 3. Photo-polymerization followed by chemical curing of the material. Trimming with appropriate burs followed.

The manufacturer’s material safety data sheets fully describe the makeup of TheraBase, which consists of tricalcium silicate (Ca₃SiO₅), dicalcium silicate (Ca₂SiO₄), tricalcium aluminate (Ca₃Al₂O₅), and calcium aluminoferrite (Ca₄Al_nFe_2-nO₇) and a photopolymerizing resin component.^3,4 MDP (10-methacryloyloxydecyl dihydrogen phosphate) is also included as a bonding agent for chemical adhesion to tooth substrates.^5,6

Currently, calcium silicate/calcium aluminate cement materials offer an alternative to the glass-ionomer systems for dentin replacement liners/bases.⁷ BISCO’s “Thera” products are examples of such liner and base materials. In more than 2 years of clinical use in both primary and permanent teeth, we have discovered that, in addition, TheraBase can also be used as an interim restorative material, replacing both dentin and enamel. Traditionally, zinc oxide/eugenol (ZOE), reinforced ZOE, and many of the glass-ionomer cement systems are used in that manner. TheraBase is now proving itself to be a worthy alternative. Following the repair of dozens of primary molars meeting certain criteria, permanent teeth needing “temporization” observations in clinical practice show that the material does not exhibit early wear, fractures, or erosion. This article presents typical examples of such uses of this material.

TECHNIQUE FOR PLACEMENT

• Cut a cavity preparation in the same design for resin-based composite or glass-ionomer cement, including mechanical undercutting.  
• Clean the preparation of all debris with water spray.
• Remove excess moisture with air spray, there is no need to completely dry surfaces to the point of desiccation.
• In the mouth, disinfect the cavity preparation with a solution such as Gluma (Kulzer) or MicroPrime (Zest Dental Solutions).^8,9
• Mix and inject material to overfill from the bottom up in the preparation and with care to avoid air entrapment.
• Apply the light beam for 20 seconds (no need to inject and cure in segments due to the chemical cure).
• Trim to the desired contour and adjust the bite to ensure against impacting occlusal forces.

DISCUSSION

With 2 years of use of TheraBase as an interim restorative material for replacing dentin and enamel, we cannot predict long-term resistance to fracture, wear, or erosion of the material when used as described here. However, in our early observations, we have seen no such material damage. In vitro laboratory experimentation and in vivo clinical studies would be useful to determine the capabilities of TheraBase interim restorations over time. However, in cases of primary teeth that have limited time before exfoliation (1 to 3 years), TheraBase could be a reliable, durable, and extremely easy-to-use temporization material (Figures 4 to 8). In addition, it features excellent radiopacity (Figure 9). This material also shows promise as a rapid stop-gap solution in permanent teeth requiring a quick and easy repair in office emergency scenarios or in any clinical circumstance when a delay is needed until more long-term treatment can be pursued (Figure 10). Examples are a temporary fill of an endodontic access opening or interim repair of a tooth with a sensitive caries lesion, with or without enamel hypoplasia/hypocalcification. Partially erupting permanent teeth exhibiting caries lesions can also be temporarily treated with TheraBase, such as the molar shown in Figure 11. When TheraBase was placed in that tooth one year prior, one-half of the crown was covered by the soft-tissue operculum, and short of an operulectomy, access was limited. Figures 12 and 13 show 8- and 10-month postoperative images of emergency repairs in patients. Figure 14 is a montage of 6 primary and permanent molars, all of which had been repaired with TheraBase 12 to 24 months post-op.

Figure 4. Four months after mesial-occlusal repair of a second primary molar in an 11-year-old.

Figure 5. Seven-month-old mesial-occlusal-distal TheraBase repair in a 12-year-old.

Figure 6. Eight months after Class II repair of 2 primary molars in an 11-year-old.

Figure 7. Eight-month-old “MOD” interim repair of a primary second molar in a 12-year-old.

Figure 8. Ten months after silver diammine fluoride caries attenuation and TheraBase repair in a 9-year-old.

Figure 9. Radiographic view showing material radiopacity of 3 primary molars (2 shown in Figure 6), plus the mandib- ular primary first molar, near exfoliation, 10 months postoperatively.

Figure 10. Six months after an “emergency visit,” TheraBase repair of a sensitive carious tooth was done in a 19-year-old.

Figure 11. A permanent second molar in a 13-year-old was partially erupted when interim repair was needed one year prior.

Figure 12. Interim emergency premolar repair, 8 months post-op, after a 16-year-old patient fractured a disto-occlusal resin-based composite (RBC) restoration.

Figure 13. Emergency TheraBase restoration 10 months post-op after a 19-year-old patient fractured a mesial-occlusal-distal RBC. Residual RBC is seen at the margin.

Figure 14. A montage of 6 permanent and primary molars that had been repaired with TheraBase 12 to 24 months post-op.

REFERENCES

1. Croll TP, Cavanaugh RR. Posterior resin-based composite restorations: a second opinion. J Esthet Restor Dent. 2002;14(5):303–12. doi:10.1111/j.1708-8240.2002.tb00526.x 

2. Cannon ML. A 21st-century material for all deep restorations. Inside Dentistry. 2022; 18(8):44–5. 

3. BISCO. TheraBase Base Safety Data Sheet. https://www.bisco.com/assets/1/22/TheraBase_Base_SDS_US_English.pdf

4. BISCO. TheraBase Catalyst Safety Data Sheet. https://www.bisco.com/assets/1/22/
TheraBase_Catalyst_SDS_US_English.pdf

5. Kuraray Dental. MDP Monomer. May 13, 2018. Accessed January 26, 2022. https://
kuraraydental.com/clearfil/key-technologies/mdp-monomer/

6. Lively T. What is MDP and why is it an MVP for bonding? Dental Products Report. 2021;55(11).  

7. Primus C, Gutmann JL, Tay FR, et al. Calcium silicate and calcium aluminate cements for dentistry reviewed. J Am Ceram Soc. 2021;105(3):1841–63. doi:10.1111/jace.18051

8. Christensen R. TRAC Research: Disinfection of tooth preparations—why and how? Clinicians Report. 2009;2(11):1-2.

9. Christensen R. Focus On: Tooth preparation disinfection. Dent Today. 2014;33(3):16. 

ABOUT THE AUTHORS

Dr. Croll is the clinic director of Cavity Busters Doylestown in Doylestown, Pa; an adjunct professor of pediatric dentistry at the Dental School at the University of Texas Health Science Center at San Antonio; and a clinical professor of pediatric dentistry at the Case Western Reserve School of Dental Medicine in Cleveland. He can be reached at willipus@comcast.net.

Dr. Gutmann is professor emeritus at the Texas A&M University College of Dentistry in Dallas and a distinguished adjunct professor in the Department of Cariology at Saveetha Dental College and Hospital in Chennai, India. He can be reached at jlg4570@aol.com.

Dr. Lawson is the director of the division of biomaterials and program director of the biomaterials residency program at the University of Alabama at Birmingham School of Dentistry. He can be reached at nlawson@uab.edu.

Disclosure: Dr. Lawson receives research and honoraria from BISCO, Kulzer, and other companies not mentioned in this article. Drs. Croll and Gutmann report no disclosures.

Drinking a cold beverage can be agony for people with tooth decay, but that may soon change thanks to research by an international team of scientists.

“It’s a unique kind of pain,” said David Clapham, vice president and chief scientific officer at the Howard Hughes Medical Institute (HHMI). “It’s just excruciating.”

Clapham and his colleagues have figured out how teeth sense the cold and pinpointed the molecular and cellular players involved. In both mice and human beings, tooth cells called odontoblasts include cold-sensitive proteins that detect temperature drops. Signals from these cells can ultimately trigger a jolt of pain to the brain.

The research offers and explanation for how one age-old home remedy eases toothaches. The main ingredient in clove oil, which has been used for centuries in dentistry, includes a chemical that blocks the “cold sensor” protein, said electrophysicist Katharina Zimmermann, who led the work at Friedrich-Alexander University Erlangen-Nürnberg in German.

Developing drugs that target this sensor even more specifically could potentially eliminate tooth sensitivity to cold, Zimmerman said.

“Once you have a molecule to target, there is a possibility of treatment,” Zimmerman said.

Teeth decay when films of bacteria and acid eat away at the enamel. As the enamel erodes, cavities form. Approximately 2.4 billion people around the world have untreated cavities in their permanent teeth, the researchers said, which can cause intense pain including extreme cold sensitivity.

No one really knew how teeth sensed the cold, though scientists had proposed one main theory. Tiny canals inside the teeth include fluid that moves when the temperature changes. Somehow, nerves can sense the direction of this movement, which signals whether a tooth is hot or cold, as some researchers have suggested.

“We can’t rule this theory out,” but there wasn’t any direct evidence for it, said Clapham, a neurobiologist at HHMI’s Henelia Research Campus.

Fluid movement in teeth, and tooth biology in general, is difficult to study, the researchers said. Scientists have to cut through the enamel, which is the hardest substance in the body, and the layer of dentin all without pulverizing the tooth’s soft pulp and the blood vessels and nerves within it. Sometimes, the whole tooth “will just fall to pieces,” Zimmerman said.

The researchers did not set out to study teeth. Their work focused primarily on ion channels, or the pores in cells’ membranes that act like molecular gates. After detecting a signal such as a chemical message or temperature change, the channels either clamp shut or open wide and let ions flood into the cell. This creates an electrical pulse that zips from cell to cell. It’s a rapid way to send information and crucial in the brain, heart, and other tissues, the researchers said.

About 15 years ago when Zimmerman was a postdoc in Clapham’s lab, the researchers discovered that an ion channel called TRPC5 was highly sensitive to cold. But the researchers didn’t know where in the body that its cold-sensing ability came into play. It wasn’t the skin, they found, as mice that lacked the ion channel could still sense the cold.

After that, the researchers “hit a dead end,” Zimmerman said. They were sitting at lunch one day discussing the problem when the idea finally hit them.

David said, ‘Well, what other tissues in the body sense the cold?’” Zimmerman said, noting that the answer was teeth.

TRPC5 does reside in teeth, and more so in teeth with cavities, said coauthor Jochen Lennerz, MD, PhD, a pathologist from Massachusetts General Hospital (MGH), which the researchers discovered after examining specimens from human adults.

A novel experimental setup in mice convinced the researchers that TRPC5 indeed functions as a cold sensor. Instead of cracking a tooth open and solely examining its cells in a dish, the researchers looked at the whole system, including the jawbone, teeth, and tooth nerves.

The researchers drilled the mice’s molars under anesthesia. Mice with dental injuries manifest pain with their behavior. For example, they drink up to 300% more sugar water than their litter mates without dental injuries.

The researchers recorded neural activity as an ice-cold solution touched the tooth. In normal mice, this frigid dip sparked nerve activity, indicating the tooth was sensing the cold. Not so in mice lacking TRPC5 or in teeth treated with a chemical that blocked the ion channel.

The genetically altered mice that did not have the TRPC5 gene but did have injured teeth did not manifest the increased drinking behavior and behaved like mice without dental injuries. That was a key clue that the ion channel could detect cold, Zimmerman said. One other ion channel the researchers studied, TRPA1, also seemed to play a role.

The researchers traced TRPC5’s location to a specific cell type, the odontoblast, that resides between the pulp and the dentin and ultimately forms dentin. When someone with a dentin-exposed tooth bites down on a popsicle, for example, those TRPC5-packed cells pick up on the cold sensation and an “ow!” signal speeds to the brain.

“We found that odontoblasts, which support the shape of the tooth, are also responsible for sensing cold,” said Lennerz, who is director of the Center for Integrated Diagnostics at MGH.

“We now have definitive proof that the temperature sensor TRPC5 transmits cold via the odontoblast and triggers nerves to fire, creating pain and cold hypersensitivity. This cold sensitivity may be the body’s way to protect a damaged tooth from additional injury,” said Lennerz.

“This research contributes a new function to this cell, which is exciting from a basic-science standpoint. But we now also know how to interfere with this cold-sensing function to inhibit dental pain,” Lennerz said. “A breeze on the face registers as extreme pain in the teeth, which may even cause some patients to stop therapy.”

Specifically, in response to cold, the TRPC5 protein opens channels in the membrane of odontoblasts, enabling other molecules such as calcium to enter and interact with the cell. If the tooth’s pulp is inflamed from a deep cavity, for example, TRPC5 is overabundant, causing increased electrical signaling via the nerves emerging from the root of the tooth and running to the brain, where pain is perceived. When gums recede from aging, teeth can become hypersensitive because the odontoblasts are sensing cold in a newly exposed region of the tooth.

“Most cells and tissues slow their metabolism in the presence of cold, which is why donor organs are put on ice,” said Lennerz. “But TRPC5 makes cells more active in cold, and the odontoblasts’ ability to sense cold via TRPC5 makes this discovery so exciting.”

Lennerz confirmed the presence of the TRPC5 protein in extracted human teeth, which the researchers called a technical tour de force.

“Our teeth aren’t meant to be cut into ultra-thin layers so they can be studied under the microscope,” said Lennerz, who first had to decalcify the teeth and put them in epoxy resin before slicing them and identifying the TRPC5 channels in the odontoblasts.

The researchers also identified a pharmacological target for minimizing tooth sensitivity to cold. For centuries, they said, oil of cloves has been used as a remedy for tooth pain. The active agent in oil of cloves is eugenol, which happens to block TRPC5. Toothpastes with eugenol already are on the market, but this study may lead to more potent applications to treat teeth that are hypersensitive to cold, the researchers said. And there may be novel applications for eugenol, such as treating patients systemically for extreme cold sensitivity from chemotherapy.

“I’m excited to see how other researchers will apply our findings,” said Lennerz.

And while the sharp sensation hasn’t been as extensively studied as other areas of science, Clapham said, tooth pain “is important and it affects a lot of people.”

The researchers’ journey toward this discovery has spanned more than a decade, Zimmerman said, adding that while figuring out the function of particular molecules and cells is difficult, “Any good research can take a lot of time.”

The study, “Odontoblast TRPC5 Channels Signal Cold Pain in Teeth,” was published by Science Advances.

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As the constraints of COVID-19 have limited dental schools’ ability to train their students in practical, hands-on care, Innovate UK has awarded funding to Manchester Imaging to adapt and repurpose its AssistDent machine learning algorithms so dental students can improve their dental radiography analysis abilities remotely.

AssistDent helps clinicians diagnose early dental disease. Dentists and dental schools across the United Kingdom and Europe use it as a prompting system when they are analyzing bitewing radiographs, looking for early signs of enamel proximal caries.

The funding from Innovate UK, which is the United Kingdom’s governmental innovation agency, enabled Manchester Imaging to adapt and repurpose its technology to analyze dental radiographs and deliver a remotely accessible intelligent learning platform for dental students that can record their clinical assessment of a radiograph, automatically interpreting and evaluating it against a gold standard assessment.

At an early phase of the research process and to evaluate a novel application of computer-aided diagnosis based on artificial intelligence (AI) in dentistry training, the company launched a study with 24 third-year dental student volunteers randomly divided into control and experimental arms. Both groups examined the same images using the same graphical user interface, with the AssistDent caries detection function disabled for the control arm.

The study showed an increased ability in the detection of enamel-only proximal caries by the students using AssistDent, showing a mean sensitivity level of 0.80, increased from 0.50 shown by students not using AssistDent. This improvement was achieved without an increase in false positives. Mean false positives per bitewing radiograph recorded by students when using AssistDent was 2.64, compared to 2.46 by students who didn’t use AssistDent.

A set of example radiographs with expert annotations is available through the platform as a gold standard for student use. Or, tutors can provide their own images and annotations.

Within the study, gold standard annotation of caries was obtained from a panel of five dentomaxillofacial radiologists and one professor of restorative dentistry, each of whom performed a clinical evaluation on a set of images and provided annotation on the location and grade of caries, resulting in a gold standard set of 1,972 examples of enamel-only proximal caries for algorithm training and evaluation.

The graphical user interface enables students to add their clinical assessment, marking up identified pathologies. A machine learning algorithm automatically analyses the image and intelligently compares the tutor’s gold standard analysis with that of the student, accounting for the underlying mouth anatomy and giving a detailed breakdown of all the pathology identified (true positives) as well as missed (false negatives) and incorrectly classified (false positives), providing the tutor with a score for each image.

Students now can get a detailed breakdown of their performance and learning process, Manchester Imaging said, in conjunction with their tutors without needing to physically attend the dental school.

The project to adapt Manchester Imaging’s existing technology was funded through Innovate UK’s Business-Led Innovation in Response to Global Disruption competition, a rapid response funding program that received more applications than all of its competitions for the previous year combined.

“The COVID-19 situation is not just a health emergency, but also one that affects the economy and society,” said Neil Morgan, head of Fast Start at Innovate UK. “With that in mind, Innovate UK launched this Fast Start funding, seeking smart ideas from UK innovators. Like other primary care providers, the dental sector has been particularly impacted, so AssistDent’s technology is particularly timely and useful as we seek to get through and recover from the pandemic.”

The award for AssistDent is clear evidence of governmental recognition of the need to financially support the development of new technologies across the dental profession and to help companies innovate for public health, Manchester Imaging said.

“We are delighted to have received this support from Innovate UK, which has helped facilitate the early and rapid adaptation of our technology to help address current pressing dental educational needs during this pandemic,” said Tony Travers, CEO of Manchester Imaging.

“The sector has been particularly hard hit by COVID-19, both functionally and economically, and we hope the technology now available will continue to assist both institutions and students, harnessing intelligent automation and increasing opportunities for online, remote clinical learning,” Travers said.

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Researchers at the University of Washington (UW) are preparing to launch clinical trials of a lozenge that may rebuild tooth enamel.

The lozenge includes a genetically engineered peptide, or chain of amino acids, along with phosphorous and calcium ions, which are the building blocks of tooth enamel. The peptide is derived from amelogenin, the key protein in tooth enamel formation. It also is vital to the formation of cementum, which makes up the surface of the tooth root.

Each lozenge deposits several micrometers of new enamel on the teeth via the peptide, which is engineered to bind to the damaged enamel to repair it while not affecting the mouth’s soft tissue. The new layer also integrates with dentin, the living tissue underneath the tooth’s surface.

Two lozenges a day could rebuild enamel, while one a day could maintain a healthy layer, the researchers said. The lozenge, which could be used like a mint, is expected to be safe for use by adults and children alike. The researchers have been discussing commercial applications with potential corporate partners.

The lozenge also produces new enamel that is whiter than what tooth-whitening strips or gels produce, the researchers said. Plus, conventional whitening treatments rely on hydrogen peroxide, a bleaching agent that can weaken tooth enamel after prolonged use.

Since tooth enamel doesn’t regrow spontaneously, the underlying dentin can be exposed, with results ranging from hypersensitivity to cavities or even gum disease, the researchers said. But the lozenge, on the other hand, is designed to strengthen, rebuild, and protect teeth.

While fluoride also can fortify tooth enamel, the researchers added, it does not actively rebuild it. Fluoride also dilutes relatively quickly, and its overall effectiveness depend largely on diligent oral hygiene. Meanwhile, the lozenge can be used in conjunction with very low concentrations of fluoride, or about 20% of what is found in most toothpastes, the researchers said.

“We have three objectives in the clinical trial,” said team leader Mehmet Sarikaya, professor in the Department of Materials Research Science and Engineering and adjunct professor in the Department of Oral Health Sciences.

“First, demonstrate efficacy. Second, documentation. Third, benchmarking, seeing how the whitening effect compares to existing commercial treatments,” said Sarikaya.

The researchers already have tested the lozenge on extracted teeth from human beings, pigs, and rats, as well as on live rats. Also, the researchers plan to develop related products for use in dental office, with this phase of trials beginning in March or April.

“Each study will take two weeks, and we expect these trials to take no more than three months,” said Sami Dogan of the School of Dentistry’s Department of Restorative Dentistry.

The researchers additionally are developing a toothpaste for over-the-counter use, but they have not fixed a timetable for its introduction.

Plus, the researchers are investigating a gel or solution with the engineered peptide to treat hypersensitive teeth, which results from weakness in the enamel that makes the underlying dentin and nerves more vulnerable to heat or cold.

Most common products currently on the market can put a layer of organic material on the tooth and numb nerve endings with potassium nitrate, but the relief is only temporary. The peptide, however, addresses the problem permanently at the source by strengthening the enamel, the researchers said.

The idea for the lozenge design began with Deniz Yucesoy, a graduate student in the university’s Genetically Engineered Materials Science and Engineering Center who received a $100,000 Amazon Catalyst grant through CoMotion, UW’s commercialization center, to support the initial project. Key contributions also came from Hanson Fong, a research scientist in the Department of Materials Science and Engineering.

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Researchers at the University of Illinois at Chicago (UIC) have determined, for the first time, how materials come together at the molecular level to form bones and other hard tissues like teeth and enamel.

The researchers captured high-resolution, real-time images of the mineralization process in an artificial saliva model and discovered distinct pathways that support bone and teeth formation, or biomineralization.

Until now, these pathways, particularly at the early stages when molecules are first starting to organize into a structure, have not been understood clearly,” said Reza Shahbazian-Yasser, PhD, professor of mechanical and industrial engineering at the UIC College of Engineering and corresponding author of the paper.

The researchers observed that both direct and indirect formations of hydroxyapatite crystals, the foundation of hard tissues, can be achieved by local variation in energetic pathways for nucleation and growth.

“The control over the dissolution of amorphous calcium phosphate affects the assembly of hydroxyapatite crystals into larger aggregates,” said Shahbazian-Yasser.

“Using technology developed at UIC, we found evidence that these pathways coexist simultaneously, explaining why different groups had reported seemingly different or opposite results,” he said.

“In addition, we now understood how hydroxyapatite materials nucleate and grow on amorphous calcium phosphate templates. The control over the nucleation and growth of hydroxyapatite will aid in developing new drugs and medical treatments to heal lost or broken bone faster or cure tooth cavities,” he said.

To capture the images, the researchers said they used a unique microdevice that made it possible to use electron microscopy with a liquid model. Using this method, the researchers were able to monitor chemical reactions in the model on the smallest scale.

“Our study provides clear, new evidence of how minerals organize and grow into bone materials, and this finding has many important implications for further research on bone or teeth healing,” said Shahbazian-Yasser.

“By better understanding these pathways, scientists are one step closer to engineering ways to better treat dental diseases and bone injuries, like those from traumatic injuries, or prevent medical conditions that can develop when normal mineralization processes in the body go awry,” he said.

Medical conditions caused by dysfunctional mineralization in the body can include everything from a tendency to develop cavities to osteoporosis.

“In the next step, we would like to learn how molecular modifiers can affect the process of biomineralization, which is important to develop effective drugs,” Shahbazian-Yasser said.

The study, “Revealing Nanoscale Mineralization Pathways of Hydroxyapatite Using in Situ Liquid Cell Transmission Electron Microscopy,” was published by Science Advances.

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The dark pigmentations that appear around the gums on dental enamel have a bacterial origin, and currently, there is no definitive therapy to remove it entirely. Researchers with the Oral Microbiology Group of the CEU Cardenal Herrera University (UCH) of Valencia, Spain, however, have conducted the first study of the metagenomics of dental black plaque in adults who have it, in collaboration with Microomics Systems SL.

The researchers assessed the efficiency of phototherapy in treating these stains on enamel in previous studies, they said, but knowing the metagenomics of this type of dark plaque of bacterial origin will enable them to progress in their search for definitive treatments for its removal.

In their study, the researchers described and compared the microbial diversity of dental white plaque and the black stains that appeared on 27 adults who were receiving treatment at the CEU UCH University Dental Clinic. The characterization of the taxonomic profile of the samples and comparison of the microbiomes of white and black dental plaque had only been done on children before, the researchers said, who most often suffer from these types of stains.

With this data, the researchers have created the first map of the microbiome of dental black plaque in adults, finding that there is less variety in bacterial species in dental black plaque than in dental white plaque. The five most common bacterial species found in the dental black plaque of adults were from the Capnocytophaga, Leptorichia, Fusobacterium, Corynebacterium, and Streptococcus genuses. The study also made it possible to detect the existence of functional routes among the microbiomes of white and black dental plaque.

The routes of biosynthetic compounds of the heme group are key to the formation of dental black plaque, the researchers said, explaining the black color. The sequestration of iron by the bacteria of the black plaque and its subsequent metabolism toward biosynthetic routes of the heme group are essential for the formation of this type of plaque, the researchers said. Along with new research for its complete description, this finding will make it possible to design treatments that effectively prevent the appearance of dental black plaque, the researchers said.

In 2018, the Oral Microbiology Group at CEU UCH published a study on the use of antimicrobial phototherapy to fight, with light and oxygen, the proliferation of the bacteria that cause the black stains on enamel or dental black plaque. Using a household tooth whitening device, the decreased the size, color, and bacterial colonization of the dental black plaque closest to the gums in the patients who participated.

In previous studies, the researchers also analyzed the risk factors for the appearance of these black stains, such as water with high iron contents of high pH, which is why they recommend consuming mineral water instead of tap water or osmosis water for people who are prone to having these black pigmentations appear on their enamel.

The study, “Dental Black Plaque: Metagenomic Characterization and Comparative Analysis with White-Plaque,” was published by Scientific Reports.

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New discoveries about the cellular makeup and growth of teeth can expedite developments in regenerative dentistry as well as the treatment of tooth sensitivity, according to researchers from the Karolinska Institutet, the Medical University of Vienna, and Harvard University.

Teeth develop through a complex process in which soft tissue, with connective tissue, nerves, and blood vessels, are bonded with three different types of hard tissue into a functional body part. As an explanatory model for this process, scientists often use the mouse incisor, which grows continuously and is renewed throughout the animal’s life.

Even though the mouse incisor has often been studied in a developmental context, the researchers said, many fundamental questions about the various tooth cells, stem cells, and their differentiation and cellular dynamics remain to be answered.

Using a single-cell RNA sequencing method and genetic tracing, the researchers have now identified and characterized all cell populations in mouse teeth and in young growing and adult human teeth.

From stem cells to the completely differentiated adult cells, the researchers said, they deciphered the differentiation pathways of odontoblasts, which give rise to dentin, and ameloblasts, which give rise to enamel. They also discovered new cell types and layers in teeth that could play a role in tooth sensitivity.

Some of the findings also can explain certain complicated aspects of the immune system in teeth, while others shed new light on the formation of tooth enamel, the researchers said.

The researchers further said that they believe their work can form the basis of new approaches to tomorrow’s dentistry. Specifically, they added, it can expedite the fast expanding field of regenerative dentistry, which is a biological therapy for replacing damaged or lost tissue. 

The researchers have made their results publicly accessible as searchable interactive user-friendly atlases of mouse and human teeth, which should be a useful resource for dental biologists as well as for researchers interested in development and regenerative biology in general.

The study, “Dental Cell Type Atlas Reveals Stem and Differentiated Cell Types in Mouse and Human Teeth,” was published by Nature Communications.

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Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed a new method for using atomic force microscopy (AFM) to quantitatively evaluate how acidic and sugary drinks affect human tooth enamel at the nanoscale level. According to the researchers, this novel approach is useful for measuring mechanical and morphological changes that occur over time during enamel erosion induced by beverages.

Enamel is the hardest substance in the human body. Its resilient surface is 96% mineral, which is the highest percentage of any body tissue, making it durable and resistant to damage. It acts as a barrier to protect the soft inner layers of the tooth, but it can become susceptible to degradation by acids and sugars.

Erosion occurs when enamel is overexposed to excessive consumption of acidic and sugary food and drinks. If left untreated, enamel loss can lead to conditions including stains, fractures, sensitivity, and translucence. Once enamel is damaged, it can’t be brought back. Therefore, the researchers said, thorough studies on how enamel erosion starts and develops, especially at the initial stages, are of high scientific and clinical relevance for dental health maintenance.

AFM is a very high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer that is equal to one billionth of a meter. It generates images by scanning a small cantilever over the surface of a sample, precisely measuring the structure and mechanical properties of the sample such as surface roughness and elastic modulus.

Five healthy human molars were obtained from volunteers between the ages of 20 and 35 who visited the KAIST Clinic. After extraction, the teeth were preserved in distilled water before the experiment. The researchers then immersed the teeth in Coca-Cola, Sprite, and Minute Maid orange juice. The drinks were purchased and opened right before immersion, and the team later used AFM to measure the surface topography and elastic modulus map of the molars.

The surface roughness of the tooth enamel increased significantly as the immersion time increased, while the elastic modulus of the enamel surface decreased drastically. The enamel surface roughened five times more when it was immersed in beverages for 10 minutes, and the elastic modulus of tooth enamel was five times lower after five minutes in the beverages.

Also, the researchers found preferential etching in scratched tooth enamel. Brushing your teeth too hard and toothpastes with polishing particles that are advertised to remove dental biofilms can cause scratches on the enamel surface, which can be preferential sites for etching, the study revealed.

“Our study shows that AFM is a suitable technique to characterize variations in the morphology and mechanical properties of dental erosion quantitatively at the nanoscale level,” said professor Seungbum Hong of the KAIST Department of Materials Science and Engineering.

The study, “Nanoscale Effects of Beverages on Enamel Surface of Human Teeth: An Atomic Force Microscopy Study,” was published by the Journal of the Mechanical Behavior of Biomedical Materials.

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Proteins embedded in 800,000-year-old dental enamel have revealed the position of Homo antecessor in the human family tree, according to the University of Copenhagen in Denmark and the National Research Center on Human Evolution in Burgos, Spain.

The researchers note that this is the first time than genetic information has been retrieved from such an old fossil, shedding light on one of the branching points in human evolution and reaching further back in time than previously possible.

“Ancient protein analysis provides evidence for a close relationship between Homo antecessor, us (Homo sapiens), Neanderthals, and Denisovans,” said Frido Walker, postdoctoral research fellow at the Globe Institute, University of Copenhagen, and first author.

“Our results support the idea that Homo antecessor was a sister group to the group containing Homo sapiens, Neanderthals, and Densovans,” said Walker.

The researchers used mass spectrometry to sequence the proteins and determine where Homo antecessor was in the human family tree.

Researchers at the university’s Faculty of Health and Medical Sciences developed the new molecular method, palaeoproteomics, to retrieve molecular evidence to accurately reconstruct human evolution from further back in time than ever before.

The chimpanzee is the closest living relative to modern humans. The chimpanzee and human lineages split between 7 million and 9 million years ago. Scientists have aimed to better understand the evolutionary relations between our species and the others, all now extinct, in the human lineage.

“Much of what we know so far is based either on the results of ancient DNA analysis or on observations of the shape and the physical structure of fossils,” said Enrico Cappellini, associate professor at the Globe Institute and leading author of the study.

“Because of the chemical degradation of DNA over time, the oldest human DNA retrieved so far is dated at no more than approximately 400,000 years,” said Cappellini. “Now, the analysis of ancient proteins with mass spectrometry, an approach commonly known as palaeoproteomics allows us to overcome these limits.”

The fossils analyzed by the researchers were found by paleoanthropologist José María Bermúdez de Castro and his team in 1994 in stratigraphic level TD6 from the Gran Dolina cave site in the Sierra de Atapuerca, Spain.

Initial observations led researchers to conclude that Homo antecessor was the last common ancestor to modern humans and Neanderthals based on the physical shape and appearance of the fossils. In the following years, anthropologists have intensely discussed the exact relation between Homo antecessor and other human groups like Homo sapiens and Neanderthals.

Though the hypothesis that Homo antecessor could be the common ancestor of Neanderthals and modern humans is very difficult to fit into the evolutionary scenario of the genus Homo, new findings in TD6 and subsequent studies revealed several characters shared among the human species found in Atapuerca and the Neanderthals.

New studied have confirmed that the facial features of Homo antecessor are very similar to those of Homo sapiens but very different from those of the Neanderthals and their more recent ancestors.

“I am happy that the protein study provides evidence that the Homo antecessor species may be closely related to the last common ancestor of Homo sapiens, Neanderthals, and Denisovans,” said Bermúdez de Castro, who also is co-corresponding author of the study.

“The features shared by Homo antecessor with these hominins clearly appeared much earlier than previously thought. Homo antecessor would therefore be a basal species of the emerging humanity formed by Neanderthals, Densovans, and modern humans,” said Bermúdez de Castro.

“This study is an exciting milestone in palaeoproteomics. Using state of the art mass spectrometry, we can determine the sequence of amino acids within protein remains from Homo antecessor dental enamel,” said Jesper Velgaard Olsen, professor at the Novo Nordisk Foundation Center for Protein Research at the university and co-author of the study.

“We can then compare the ancient protein sequences we read to those of other hominins—for example, Neanderthals and Homo sapiens—to determine how they are genetically related,” said Velgaard Olsen.

The study, “The Dental Proteome of Homo Antecessor,” was published by Nature.

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Restorations can be costly, and they don’t last forever, according to the University of Oklahoma College of Dentistry. But researchers there are developing new materials designed to bond more tightly with the enamel structures they’re designed to repair and repel the bacteria that attack fillings and implants, improving durability and reducing costs. 

“In fact, the replacement of failed restorations accounts for 70% of dentists’ chairtime at a yearly cost of $298 billion worldwide,” said Fernando Luis Esteban Florez, DDS, MSc, PhD, an assistant professor who is conducting research at the High Flux Isotope Reactor (HFIR) at the Department of Energy Oak Ridge National Laboratory (ORNL).

“Our focus is to create smart restorative dental biomaterials that are less expensive and do not need to be replaced every five to seven years,” said Esteban Florez, adding that neutron scattering research provides insights that may lead to the development of novel materials for implant dentistry.

“A dental implant can cost as much as $4,500 per tooth. And that doesn’t include the cost of repairs should the procedure fail. Therefore, developing biocompatible polymer- or ceramic-based materials to replace those metals could greatly benefit patients,” said Esteban Florez.

“Creating novel materials that are more biocompatible with the human body would be a great asset to dentistry, and neutrons may be the perfect tool for assessing potential materials for this purpose,” he said. 

Esteban Florez already has performed neutron scattering experiments at ORNL to explore the surface-modification and functionalization of metal oxide nanoparticles in experimental dental adhesive resins. The nanoparticles have long-term antibacterial and bioactive properties.

Now, he wants to see if neutron scattering can help him better understand exactly how different restorative materials interact with enamel, dentin, and collagen within teeth. 

Specifically, he used the IMAGING instrument at HFIR to study a small collection of human teeth that had been restored either with a dental amalgam or with a resin composite. These materials were bound to the sample tooth structures using his experimental dental adhesive resins, which include varying concentrations of metal oxide nanoparticles.

Esteban Florez is now working with Hassina Bilheux, PhD, senior neutron imaging scientist at HFIR, to reconstruct his data into three-dimensional renderings he can use to observe the interactions between restorative dental biomaterials and tooth structures. 

“Neutron tomography is a powerful technique for exploring the internal aspects of organic materials such as biological tissues. These samples contain a great deal of hydrogen. And since neutrons are particularly sensitive to hydrogen, we can generate very detailed images of their microstructures,” said Bilheux.

“Neutrons can be used to probe structures within organic tissues in a nondestructive way and allow me to understand how restorative dental biomaterials interact with the entire tooth system,” said Esteban Florez. 

Esteban Florez said his research is focused on the development of polymer-based restorative materials with non-leaching and long-term antibacterial and bioactive properties that can be enhanced using visible light irradiation.

Once fully developed, these materials hold the promise to kill penetrating bacterial, naturally bond to organic and inorganic components of teeth, and guide the growth of hydroxyapatite to seal the tooth/biomaterial interface, the researchers said. 

If successful, these materials will increase the durability of current polymer-based restorative materials and decrease oral healthcare costs, the researchers said.  

“There’s still a great deal of research to be done on this topic, but we’re hopeful that our work will have a significant and positive impact on the field of restorative dentistry,” Esteban Florez said.

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