Research Topics

Polymeric materials containing amorphous calcium phosphate (ACP) arrest tooth demineralization and even regenerate defective tooth structures via 1) mineral ion release and 2) the subsequent deposition of these ions as apatite, a natural inorganic constituent of enamel and dentin. Dr. Anthony Volpe Research Center researchers have systematically investigated structure-composition-property relationships in ACP/methacrylate composites for almost two decades. The ultimate goal of these studies is to design bioactive remineralizing materials that adhere well to both enamel and dentin. Besides practical applications (formulation of the remineralizing ACP sealant, orthodontic adhesive and endodontic composite), our studies also contribute to a better understanding of the physico-chemical and mechanical properties of these polymeric ACP composites, ACP composite/tooth interfacial phenomena and cellular responses to these materials. Generally excellent biocompatibility, possible osteoinductivity, and affinity for proteins and cells make ACP potentially attractive for tissue engineering applications. Exploratory studies of ACP-loaded bioresorbable polymers intended for general bone regeneration are currently in progress. In addition, a feasibility of incorporating new quaternary ammonium methacrylates with adhesive and coupling functions into the polymer phase of ACP composites to design restoratives with both antimicrobial and remineralizing ability is being explored.

For further information, please contact Dr. Drago Skrtic at drago.skrtic@nist.gov.

Nano forms of hydroxyapatite and other bioactive materials are prepared by a novel method developed under NIH grants, employing a spray drying technique in such a way that 1) target particle sizes over a wide range can be obtained, 2) compounds with either low or high solubility can be prepared, and 3) the prepared particles would not be exposed to any solution environment after their formation and therefore would retain their original, highly reactive surfaces. Due to their small sizes and high reactivity, the prepared nano-materials are expected to have a range of clinical applications. Nano-sized calcium phosphates with a molar calcium/phosphate ratio of 1.0 to 1.67 have been prepared.  Nano-sized calcium fluoride, when used as the source of fluoride in mouth rinses, was found to produce a greater fluoride retention in the mouth than currently available products of the same fluoride content. Nano-sized calcium phosphates and calcium fluoride were also effective in reducing dentin permeability.

For further information, please contact Dr. Larry Chow at larry.chow@nist.gov.

Calcium phosphate bone cement based on ADAF patents was first introduced to the market in November 1997 under the trade name BoneSource®. The product has thus far received FDA approval for craniofacial, maxillofacial, orthopedic and trauma applications. This plaster-like material can be placed surgically, molded and sculpted to the correct anatomical shape, and will set to form a hard implant composed entirely of hydroxyapatite. The implant material is slowly dissolved and replaced entirely by new bone, thus repairing the original defect. Additional studies have led to significant improvements in the handling properties of the cement and development of cement formulations that would be suited for different clinical applications. The most advanced variety of the cement has the form of two premixed pastes packed in a dual-barrel syringe. The dispensed cement is used without further mixing.

For further information, please contact Dr. Larry Chow at larry.chow@nist.gov.

The goal of the project “Novel Dental Composite Restorative Systems with Improved Service Life”, supported by the National Institute of Dental and Craniofacial Research through 2018, is to develop a new dental resin-based composite restorative system superior in properties and endurance to currently used Bis-GMA/TEGDMA resin systems. The new dental composite will contain: a) novel monomers that, when polymerized, will not be susceptible to enzymatic and/or hydrolytic degradation, b) self-healing components, and c) smart antibacterial components that will be activated only when needed. New monomers will be formulated to include hydrolytically stable ether groups and other functionalities non-susceptible to attacks by esterases. The increased longevity of the new self-healing composites will be attained by added ability to intrinsically repair micro cracks and thus prevent a catastrophic failure of the restorations. Incorporation of a novel quaternary ammonium coupling agent will provide an antimicrobial defense system. Performance of these new materials will be evaluated using a sequence of clinically-relevant laboratory tests.

For more information contact Dr. Jirun Sun at jirun.sun@nist.gov.

Translational science in the dental and biomedical field is being conducted to advance point-of-care technologies for preventing and treating post-operative complications.  One study is developing novel biomimetic nanofiber scaffolds for in vivo construction of dressings for accelerated wound healing.  Another effort is being undertaken to advance in vitro methods used to evaluate biological biocompatibility of restorative dental materials.

For further information, please contact Dr. Diane Beinek at diane.beinek@nist.gov.

A biomimetic organotypic culture system, composed of human gingival, periodontal ligament and dental pulp progenitor/immortalized cells and tissues, is developed in a 3D extracellular matrix environment for: (a) the establishment of adaptable and scaffold-free microtissues functioning as building blocks in tissue regeneration applications, (b) screening platforms for the identification and detection of molecular and cellular biomarkers triggered by oral pathogenic microbes or toxic residues of polymeric dental materials, (c) testing multi-channeled drug delivery and release systems through the extracellular milieu. These studies will provide the knowledge and tools required to: facilitate tissue repair and regeneration mechanisms in non-threatening and threatening environments in vivo and control cellular response mechanisms under genetic and epigenetic regulatory pathways.

For further information, please contact Dr. Gili Kaufman at gili.kaufman@nist.gov.

Dr. Kim’s clinical background and experience in stem cell biology and cancer epigenetics has allowed him the opportunity to explore projects in the following areas:  1) electronic cigarette aerosol and its effect on oral health, 2) occupational hazards and safety in dental offices, and 3) the effect of medication-induced dry mouth (xerostomia) on salivary glands.

For further information, please contact Dr. Jeffrey Kim at jeffrey.kim@nist.gov

The formation and conversion of calcium phosphates are being studied for prevention and repair of dental caries and tooth sensitivity. The ADAF’s ACP patents have been licensed and marketed as toothpaste (ENAMEL CARE and MENTADENT by Church & Dwight Co.), chewing gums, confections, prophylaxis paste and fluoride varnish (ENAMEL PRO series by Premier Dental), tooth whitening (Nitewhite ACP, Discus Dental), and topical desensitizers (Quell Desensitizer by Pentron Clinical Technologies and Relief ACP by Discus Dental). Other products are currently under development. The field of remineralizing temporary cement is still available for licensing. Ongoing research is concentrating on second generation ACPs and multi-pronged approaches to prevent and/or combat caries.

For further information, please contact Dr. Ming Tung at ming.tung@nist.gov.

Volpe Research Center scientists are working to develop other calcium phosphate-based technologies that can remineralize hard tooth tissues or, at a minimum, retard caries-producing demineralization. Studies have shown that an experimental chewing gum containing α-Ca₃(PO₄)₂ can eliminate the ability of sucrose challenged plaque to demineralize tooth enamel, thus preventing a cavity from forming or progressing. Additional studies showed that separate calcium and phosphate compounds, incorporated into candies, are even more effective in producing remineralizing conditions in the mouth.

For further information, please contact Dr. Larry Chow at larry.chow@nist.gov.

The ADA Foundation Volpe Research Center utilizes an automated chemical reactor which simulates oral conditions/challenges in the human mouth. This artificial 'mouth' allows for the control of simulated acid attacks, studying fluoride addition to baseline saliva, and regulation of 'as-dosed' treatments, creating conditions similar to those during tooth brushing. We use this reactor to answer some of the lingering questions about fluoride anti-caries efficacy in the mouth.

For further information, please email vrc@ada.org.

Micro-analytical techniques and instrumentation has been developed at the ADA Foundation's research center to study the mechanisms of dental decay by examining the composition of microscopic samples of plaque, plaque fluid, and oral tissue recovered from the oral environment. These techniques have been extensively used to develop and evaluate new anti-cavity and cavity repairing technologies. As a result of these studies, fluoride rinses and dentifrices have been 'engineered' that produce a much greater cavity fighting effect while using a very low amount of applied fluoride.

For further information, please contact Dr. Jerry Vogel at jerry.vogel@nist.gov.

Nanotechnology-enabled products have been rapidly entering the U.S. healthcare sector. Nanomaterials in dentistry have proven to be beneficial in a number of areas including the development of new nanocomposites (a.k.a. white fillings) with advanced strength, esthetics, and service life. However, proof of safety of the nanomaterials to patients, short- and long-term nanomaterial-oral tissue interactions, Standard Operating Procedures (SOPs) for safe handling, use and disposal, and risk assessment for occupational nanomaterial exposure, have not been thoroughly investigated.

ADA Foundation Volpe Research Center researchers are focusing on the following key areas:
1.    Assessment of occupational nanomaterial exposure in the dental setting,
2.    Advancing in vitro test methods and standards to assess cytotoxic potential of nanomaterials by developing a microfluidic device, and
3.    Investigation of dental pulp micro-tissue and nanomaterial interaction, and genetic and epigenetic implications.

These projects will advance our current understanding of assessing nanotoxicity, measurement and standards of nano-exposures, and biological significance and therapeutic implication of current and future nano-enabled dental materials.

VRC researchers in collaboration with a NIST scientist discovered that carbonated hydroxyapatite (CHA) materials prepared in a specific way produced spectrally pure electron paramagnetic resonance (EPR) signals and that the signal strength is in proportion to the dose of ionizing radiation the material was previously exposed to. Thus CHA may be used as bio-dosimeters in place of film-based dosimeters currently in use. Current film badge dosimeters can only be used once because the film needs to be developed to determine the radiation exposure. In contrast, CHA based dosimeters are simple and inexpensive devices that can be used for an indefinite period. Current work is focused on controlling the sensitivity of the CHA dosimeters so that they can be used in a wide range of biomedical and industrial applications.

For further information, please contact Dr. Larry Chow at larry.chow@nist.gov.

One of the many ways the ADA Foundation Volpe Research Center contributes to the safety and efficacy of dental products is through active involvement in both the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO). A VRC representative regularly attends the ADA Standard Committee for dental products SCDP/ANSI meeting held in conjunction with the annual American Association for Dental Research (AADR) and/or International Association for Dental Research (IADR) meetings.

Closer to home, VRC researchers have played a major role in developing a standard reference material for carbonated hydroxyapatite powder and a bulk carbonated hydroxyapatite test substrate.  Both of these projects are supported by the current NIH-NIST interagency agreement.

For further information, please email vrc@ada.org.

Through collaborations with government and industry, and by fostering mentorship within the dental education community, the ADA Foundation Volpe Research Center provides the science and technology basis needed to improve the field of dentistry and oral health of the public. Current research/educational collaborations include the Naval Post-Graduate Dental School, National Naval Medical Center, Bethesda, Maryland; National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR), Bethesda, Maryland ; College of Dentistry, Howard University, Washington DC; School of Dental Medicine, University of Colorado; School of Dental Medicine, Dartmouth College, New Hampshire; Dental School, Department of Bioengineering and Department of Engineering, University of Maryland; and Department of Engineering, Old Dominion University, Virginia. Forthcoming collaborations include College of Dental Medicine, Nova Southeastern University, Florida, and College of Dentistry, University of Tennessee.
For further information, please contact the VRC at: vrc@ada.org.

The ADA Foundation Volpe Research Center traditionally hosts Dental Student’s Conference on Research at the end of April each year. On average, fifty students from the US and Canada attend the meeting. The students spend one day on the NIST campus visiting the research center, and a second day visiting the NIH/NIDCR. Plenary lectures are given by the invited speakers addressing dental school, AADR, dental industry, ADA and NIST perspectives of dental research/science. Students have multiple opportunities to interact with mentors regarding careers in dental and biomaterial research. They also present their own research to their peers and on-site researchers. Selected ongoing Volpe Research Center and/or NIST projects are presented to and discussed with the attending students.

For further information, please contact Ms. Gretchen Duppins at: gretchen.duppins@nist.gov.