Ralph Kent, PhD

Just as individuals vary in height, weight, eye color, and other obvious physical characteristics, they also vary in susceptibility to diseases, exposure to risk factors, and response to treatments. Biostatistics plays an essential role in biomedical research, providing quantitative methods to evaluate and control the effects of chance and variation that occur in every study. Dr. Kent collaborates with investigators at Forsyth and several academic institutions to provide a solid biostatistical foundation for a wide range of clinical and laboratory studies.

Biostatistical Approaches in Research

Concurrent with major advances in biomedical research, there have been rapid innovations in statistical theory and methods, and increasingly widespread and sophisticated applications of biostatistics across diverse fields. Much of this progress has been aided by the advent of powerful computing and software resources. Although the principles, theory, and methods are transferable from one area of application to another, biostatistics has tended toward increasing specialization. Advances in molecular biology have stimulated a new field of bioinformatics and new approaches in molecular epidemiology and statistical genetics. Dental and oral health research has utilized many of these methodological developments.

The role of the biostatistician begins in the earliest design stages of a study or research proposal. This includes decisions about the types and numbers of subjects to be studied, the identification of outcome-distorting factors and plans for controlling them, and the definition of appropriate procedures for data collection, management, and analysis. Just as poor blueprints can result in flawed construction, poor research designs may yield data from which it is difficult, or even impossible, to draw scientifically defensible conclusions.

Periodontal and Caries Research

As Head of the Department of Biostatistics/ Epidemiology, Dr. Kent has a long history of collaboration with Forsyth's clinical and laboratory investigators. He served for over 15 years as Biostatistician for the Center for Clinical Research in Periodontal Diseases and also for the Center for Specialized Caries Research. He has participated with numerous investigators in a wide variety of clinical and laboratory research.

Research activities with the Department of Periodontology have included evaluating innovative diagnostic modalities; identifying clinical, microbial, and immunological correlates of disease progression; and identifying factors associated with refractory periodontitis. In addition, a randomized controlled trial of adjunct periodontal therapies has been conducted. Proposed new research will include clinical trials to evaluate the effects of recently developed preventive and therapeutic modalities on the microbial composition of subgingival plaque, utilizing DNA probes and checkerboard DNA-DNA hybridization for microbiological analyses.

A study of severe early childhood caries is currently being conducted in collaboration with Boston University. Microbial and dietary profiles will be evaluated in children with caries and caries-free children with particular emphasis on identifying a subset of acid tolerant species with marked pH lowering capabilities. Children with caries will also be followed for 18 months after treatment to evaluate microbial and dietary factors associated with recurrence of carious lesions. Microbiota will be evaluated by several cultural and molecular techniques. There is particular interest in relationships between dietary and microbial components.

Some Other Current Collaborations

Dr. Kent is the Biostatistician for a randomized intervention study being conducted at Boston University to evaluate systemic consequences of periodontal disease on endothelium of blood vessels. Patients with severe periodontal disease will receive comprehensive periodontal therapy and will be followed for 24 weeks to evaluate by ultrasound the effects on brachial artery flow-mediated dilation, on systemic markers of inflammation (C-reactive protein, IL-6, ICAM-1, etc.) and on oral markers of periodontitis (PGE2, myeloperoxidase, and pathogen levels) relative to controls. A collaboration with the University of Kentucky and several other institutions involves use of non-human primates (baboons) to investigate the association between periodontitis in the mother and preterm birth/low birth-weight (PTB/LBW) newborns. This study will evaluate associations between severity of periodontitis and incidence of PTB/LBW neonates and examine the role of pathogenic subgingival microbial species as well as local and systemic inflammatory markers in this process. This investigation aims to describe mechanisms of the linkage between maternal periodontitis and PTB/LBW neonates. Dr. Kent also serves as Biostatistician for the Forsyth General Clinical Research Center (GCRC) Satellite at the Beth Israel Deaconess Medical Center, providing statistical consultation and support to Forsyth investigators and also serving as occasional protocol reviewer for the GCRC's Scientific Advisory Committee.

Dr. Kent has taught Principles of Biostatistics and Epidemiology to Harvard dental and medical students and also organized a graduate course, Clinical Research Design in Oral Health Research, initially sponsored by the Boston Oral Health Clinical Resource Center at Forsyth.

Selected Publications

Fimple JL, Fontana CR, Foschi F, Ruggiero K, Song X, Pagonis TC, Tanner AC, Kent R, Doukas AG, Stashenko PP, Soukos NS. (2008) Photodynamic treatment of endodontic polymicrobial infection in vitro. J. Endod. 34(6):728-34.

Sasaki H, Suzuki N, Kent R jr, Kawashima N, Takeda J, Stashenko P.  2008. T Cell response mediated by myeloid cell-derived IL-12 is responsible for Porphyromonas gingivalis-induced periodontitis in IL-10-deficient mice. J. Immunol.
180(9):6193-8.

Keles A, Grunes B, DiFuria C, Gagari E, Srinivasan V, Darendeliler MA, Muller R, Kent R Jr, Stashenko P. 2006. Osteoclast persistence and tooth movement in a constant force model. Angle Orthod. In press.

Tanner ACR, Paster BJ, Lu SC, Kanasi E, Kent R, Van Dyke T, Sonis ST. 2006. Subgingival and tongue microbiota of adults with early periodontitis. J. Dent. Res. 85(4) :318–323.

Goodson JM, Tavares M, Sweeney M, Stultz J, Newman M, Smith V, Regan EO, Kent R. 2005. Tooth whitening: Tooth color changes following treatment by peroxide and light. J. Clin. Dent. 16(3)78–82.

Tanner ACR, Kent RL Jr, Van Dyke T, Sonis ST, Murray LA. 2005. Clinical and other risk indicators for early periodontitis in adults. J. Periodontol. 76(4):573–581.

Haffajee AD, Japlit M, Bogren A, Kent RL Jr, Goodson JM, Socransky SS. 2005. Differences in the sub-gingival microbiota of Swedish and USA subjects who were periodontally healthy or exhibited minimal periodontal disease. J. Clin. Periodontol. 32(1):33–39.

Sasaki H, Okamatsu Y, Kawai T, Kent R, Taubman M, Stashenko P. 2004. The interleukin-10 knockout mouse is highly susceptible to Porphyromonas gingivalis-induced alveolar bone loss. J. Periodontal Res. 39(6) :432–441.

Tavares M, Stultz J, Newman M, Smith V, Kent R, Carpino E, Goodson JM. 2003. Light augments tooth whitening with peroxide. J. Am. Dent. Assoc. 134 (2):167– 173

Niederman R, Kelderman H, Socransky S, Ostroff G, Genco C, Kent R Jr, Stashenko P. 2002. Enhanced neutrophil emigration and Porphyromonas gingivalis reduction following PGG-glucan treatment of mice. Arch. Oral Biol. 47(8):613–618.

Optiz OG, Harada H, Suliman Y, Rhoades B, Sharpless NE, Kent R, Kopelovich L, Nakagawa H, Rustgi AK. 2002. A mouse model of human oral-esophageal cancer. J. Clin. Invest. 110(6):761–769.

Kohno Y, Patel V, Kim Y, Tsuji TK, Chin BR, Sun M, Donnoff B, Kent R, Wong D, Todd R. 2002. Apoptosis, proliferation and p12doc-1 profiles in normal, dysplastic and malignant squamous epithelium of the Syrian hamster cheek pouch model. Oral Oncol. 38(3):274–280.

Tanner AC, Milgrom PM, Kent R, Mokeem SA, Page RC, Liao SI, Riedy CA, Bruss JB. 2002. Similarity of the oral microbiota of pre-school children with that of their caregivers in a population-based study. Oral Microbiol. Immunol. 17(6):379–387.

Tanner AC, Milgrom PM, Kent R Jr, Mokeem SA, Page RC, Riedy CA, Weistein P, Bruss J. 2002. The microbiota of young children from tooth and tongue samples. J. Dent. Res. 81 (1):53–57.

Gao XJ, Fan Y, Kent RL Jr, van Houte J, Margolis HC. 2001. Association of caries activity with the composition of dental plaque fluid. J. Dent. Res. 80(9):1834– 1839.

Alevizos I, Mahaderappa M, Zhang X, Ohyama H, Kohno Y, Posner M, Gallagher GT, Varvares M, Cohen D, Kim D, Kent R, Donoff RB, Todd R, Yung CM, Warrington JA, Wong DT. 2001. Oral cancer in vivo gene expression profiling assisted by laser capture microdissection and microarray analysis. Oncogene 20 (43):61 96–6204.