Prevention of Dental Biofilms Through Innovative Approaches
The main focus of my research team is the development of a novel antimicrobial-containing denture base material. We have engaged in this topic because denture-induced stomatitis is a very common finding among the edentulous and partially edentulous population. Since fungal colonization is a significant contributor to this disease, we are working on a technology to reduce microbial colonization and biofilm formation on these common oral prosthetic surfaces. With recent reports suggesting that denture cleanliness significantly reduces pneumonia in the elderly, this technology may have implications in reducing morbidity beyond the oral cavity.
To date, we have successfully demonstrated that this novel acrylic has the ability to bind small, naturally occurring salivary antimicrobial peptides. In addition, we have shown proportional reductions in pathogen colonization1 as well as clinically acceptable flexure and impact strength, stain resistance and color stability.2,3
Cytotoxicity studies have suggested that the materials might be suitable for clinical use, but more research is needed, especially in vivo studies, to ascertain initial findings. Ongoing work is aimed also at assessing the inhibitory effects of these materials on monospecies as well as multispecies biofilm development in vitro, and the possibility that these materials may serve as antimicrobial delivery devices for mucosal surfaces. Future clinical work will include proteomics identification of pellicle components on these materials as well as environmental microbiological assessments of potential colonizers. Funding for this work has been provided by the American College of Prosthodontists as well as the NIH-NIDCR. A patent has been issued to Marquette University on this technology.
Mar 14, 2003. Issued Oct 30, 2007.
Denture Base Resin. J Prosthodont 2007;16:465-472.
Phosphate Group Addition on the Properties of Denture Base Resins. J Prosth Dent
Optimization of Mechanical Force to Enhance Orthodontic Tooth Movement
Orthodontic treatment has improved many patients’ esthetics and chewing ability. Despite the obvious success, two challenges continue to puzzle orthodontists: long treatment time and iatrogenic root resorption. How to move teeth faster and at the same time reduce the risk of root resorption are therefore highly significant questions asked by orthodontic practitioners and scientists alike. Thus, my team’s research is focusing on how to optimize orthodontic force to move teeth fast and at minimal root resorption risk.
The objective of our research is to use animal and cell culture models to investigate the effect of mechanical vibration on clinical and molecular parameters of orthodontic tooth movement and root resorption. Our proposition is that mechanical vibration enhances orthodontic tooth movement and reduces root resorption. To test this hypothesis, we are currently pursuing the following projects:
In a first project, C57BL/6 mice are subjected to mechanical
In a subsequent project, insight into the molecular basis of the experimental findings of the first project is gained. In the presence and absence of mechanical vibration, cultures of periodontal cells are exposed to the forces of fluid shear stress (FSS). The resulting cellular response, expressed at the level of important bone markers (ALP, BSP, OPN, OPG and RANKL) is then detected by RT-PCR and Western Blot analysis.
The outcome of this clinical translational project will permit us to be one step closer to implementing mechanical vibration as a tool in the armamentarium of practicing orthodontists and, hopefully, improving the quality of patient care. Research funded by AAO.
The Role of Bacterial Virulence Factors in Periodontal Health and Disease
Our laboratory has focused on elucidating mechanisms by which bacterial pathogens mediate host-parasite interactions that will ultimately lead to the breakdown of periodontal tissues. A better understanding of these interactions will permit the development of more effective diagnostic, therapeutic and preventive measures in the management of periodontal disease.
Current projects include the study of virulence factors of major etiological agents of periodontal disease, i.e., Tannerella forsythia and Porphyromonas gingivalis. Our research utilizes molecular techniques to identify and characterize bacterial components and/or products that are important in disease initiation and progression. Novel genetic and proteomic approaches are used to identify genes and proteins that are expressed during in vivo, not in vitro, growth, and therefore are important in the actual infectious process. We also study the structure and function of a unique surface (S-) layer of T. forsythia as a virulence factor. Molecular genotypic and phenotypic characterizations of the S-layer are being investigated.
In addition, a study is being done to characterize antibiotic resistance determinants from oral biofilms. Adopting a metagenomic approach, novel resistance mechanisms will be identified and characterized from numerous oral bacteria including those that cannot be cultivated in vitro. Research funding was provided by NIH-NIDCR and NSF.
My research focus is on oral health disparities and the impact of oral health policies on dental services utilization. This includes secondary data analysis of state and national databases related to dental disease burden, oral health related quality of life and oral health services utilization with special attention on racial and ethnic minority groups.
My overarching goal is to help develop community-grounded interventions that would lead to a reduction or elimination of oral health disparities and improve oral health and overall well-being among racial and ethnic minority groups. Such interventions would include developing oral health policies and unique dental programs that utilize appropriate dental workforce models.
Recently, my research team identified factors associated with non-traumatic dental conditions (NTDC) visits to emergency departments (ED) and physician offices (PO) by Wisconsin Medicaid enrollees. The study identified a new finding in oral health disparities research: Racial/ethnic minorities are more likely to present to ED and PO for NTDC after adjustment for relevant covariates. Compared with whites, Native Americans had double the rate of NTDC visits to EDs and to POs, African-Americans had about double the rate of NTDC visits to EDs, and enrollees of other race/ethnicity (including multiracial persons) had about double the rate of PO visits for NTDCs. This new finding is significant given the substantial literature documenting that racial and ethnic minorities have the highest risk for early childhood caries, dental caries, edentulousness and oral cancer.
Furthermore, through my collaboration with local, state and national health agencies, I intend to continue my current research efforts with respect to analyzing Medicaid and other publicly available data to monitor oral health services and dental service utilization. In summary, my research focus involves studies and interventions that could lead to the elimination of oral health disparities through policy and program development and the implementation of community– grounded healthcare strategies. These strategies would be evaluated and could include stand-alone oral health policies or a combination of oral health programs and academic-community partnership.
Because of its versatility in studying dental biomaterials, differential scanning calorimetry (DSC) is a thermal analysis technique that has played a central role in my research and that of mentored graduate students. It may be used in a variety of ways to obtain different information. For example, DSC may be utilized to study chemical reactions and is thus ideal for investigating the setting of various dental materials.
Current thermal analysis research in my laboratory explores the influence the acid-base and polymerization reactions have on each other in resin-modified glassionomer (RMGI) restorative materials. Surmising that each setting mechanism is dependent upon diffusion of reactants prior to gelation, we have shown that the acid-base and light polymerization reactions compete and inhibit one another. DSC has also been used to monitor the setting of mineral trioxide aggregate (MTA) endodontic cement over time. It also provides material property determinations, such as glass transition temperature, melting point and specific heat.
As an example of this application, we have compared the thermal characteristics of gutta percha to Resilon, an alternative obturation material. Additionally, the depth of cure of RMGIs has been examined using specific heat values. Lastly, the phase transformations in nickel-titanium (NiTi) alloys that give NiTi its unique superelastic and shape memory properties are also able to be studied with DSC. Recent research has explored the effect clinical usage, temperature cycling and fluoride exposure have upon these transformations.
Dental Forensic Research—The Search for the Evidence
Our investigations have involved the application of dental science to questions of law concerning patterned injuries caused by human teeth, i.e., bite marks. In response to the substantial challenges such investigations may produce, a multidisciplinary team was formed that includes dentists, lawyers, a statistician and an IT specialist. Supported by governmental funding, the team’s initial focus was on the two-dimensional quantification of individual characteristics of the human dentition. The significance of this project is that it could, one day, provide statistical support for opinion testimony, answering Daubert factors (validity of expert testimony).
During the past three years, in collaboration with the Wisconsin Department of Justice, we have developed a data set on the frequency that six dental characteristics occur in a convenience sample of males, ages 18–44 years. Many students participated in sample collection at various sites in Wisconsin. Because of their diligent assistance and the support of countless volunteers, it was possible to build our database of several hundred exemplars.
An exciting by-product of this project was the development of Tom’s Toolbox®. This automated software application allows users to conveniently measure tooth width, tooth displacement and angles of tooth rotation—all important features in forensic dentistry and many other related research applications. Because of its potential usefulness in legal disputes, our research achieved considerable media recognition. Our team has received funding through the U.S. Department of Justice and from the U.S. Department of Energy.
characteristics of the human dentition: Methodology. J For Ident 2008;58(4):409-417.
Biomaterials and Tissue Engineering
Years ago, the best interaction we could hope for in response to a material implanted in the body was that it would be inert, meaning that there would be no adverse response in peri-implant tissues. In reality, that rarely happens as biomaterials easily undergo corrosion and mechanical degradation when implanted. These degradation roducts incite an inflammatory response, which has the potential to make sophisticated engineered medical and dental devices less effective or less safe. The clinical significance is that this exposes the patient to revision procedures or additional surgeries as well as added cost.
In response to this, my research has focused on bioactive biomaterials and tissue engineering—combining structural biomaterials with biologically active agents and/or living cells to make bioactive biomaterials. In an article on tissue engineering, a dental coauthor and I described our vision for the field of tissue engineering more than a decade ago.1 Since that time, I have published more than 50 refereed articles and book chapters and coauthored more than 130 presentations at international and national meetings. Many of the recent publications are joint publications with Marquette University School of Dentistry faculty and more than 30 Master’s and doctoral students with whom I have worked.2,3
My research has garnered significant industrial funding, especially in collaboration with Medtronic and other medical device companies. I have also served as an invited expert discussant before FDA panels on evaluation of safety and efficacy of biomaterials for medical and dental devices, including a bone graft substitute device approved by the Medical Devices Advisory Committee of the FDA Dental Products Panel.
Osteogenesis. J Biomed Mat Res: Appl Biomat 1998;43(4): 380-398
Biomaterial for Endodontic Treatment. Dent Mat 2008;24:149-164.
Failure Analysis of Prosthetic Retaining Screws after Long-Term Use In-vivo. Parts I
through IV. J Prosth Dent 2008;17:149-210.