Faculty Bibliography

Short-chain carboxylic acids (SCCA; C < or = 5; e.g., lactic acid, propionic acid, butyric acid) are metabolic by-products of bacterial metabolism which accumulate in the gingival crevice, and exhibit significant biological activity, including the ability to alter gene expression. It has been hypothesized that among the activities of SCCAs are their ability to contribute to gingival inflammation. This concept complements the notion that specific periodontal pathogens are the causative agents of gingival inflammation. To begin testing these 2 hypotheses, we examined the relationship between SCCA concentrations, specific putative periodontal pathogens, and gingival inflammation in medically healthy periodontally diseased subjects. We reasoned that if SCCAs and/or specific periodontal pathogens were causative gingival inflammatory agents, gingival inflammation should increase with increasing concentration of the inflammatory mediator. We also recognized that other clinical variables needed to be controlled for, and an objective quantitative assessment of gingival inflammation used. To accomplish these tasks, sites within subjects were stratified by location and pocket depth, and the following quantified: bacterial presence; SCCA concentration; and gingival inflammation. The results indicated that gingival inflammation directly and significantly correlated with SCCA concentrations in the maxillary and mandibular molars, incisors and canines (all r > or = 0.47; all p < or = 0.015; too few bicuspids were available for complete analysis). The relationship between gingival inflammation and SCCA concentration was best described by a natural log relationship. Gingival inflammation did not, however, correlate positively with either the total number of specific putative periodontal pathogens, or the sum of subsets of these pathogens (-0.31 < or = r < or = 0.39; 0.08 < or = p < or = 0.75) for any of the locations. Finally, the SCCA concentration did not correlate with the level of individual or groups of pathogens. These data, together with historical work and other preliminary data, support the hypothesis that SCCA, rather than specific putative periodontal pathogens, may be a causative agent in gingival inflammation. This work may, in part, begin to explain the apparent lack of a direct relationship between current gingival inflammation and the prediction of bacterially mediated periodontal attachment loss.

The cadherins are a family of cell membrane proteins that mediate calcium-dependent cell-cell adhesion. E-cadherin is required for the formation, differentiation, polarization and stratification of epithelia; P-cadherin is also expressed on many epithelia. We report here the first study of cadherin expression in immortalized human gingival epithelial cells (IHGK) and examine the role of cadherins in growth regulation of these cells. We found that the IHGK cells are similar to normal gingival epithelial cells in their cadherin expression and density-dependent inhibition of growth. The IHGK cells proliferate more rapidly at low calcium concentration (0.15 mM) than at physiological concentrations of calcium (1.8 mM) and magnesium (0.65 mM; Ca/Mg medium) suggesting that calcium is required for density-dependent regulation of proliferation. To evaluate the possibility that cadherin function is required for contact inhibition in these cells, we grew them in Ca/Mg medium in the presence of adhesion-blocking anti-cadherin monoclonal antibodies. At anti-E-cadherin concentrations sufficient to disrupt cell-cell adhesion, the proliferation of the IHGK cells was similar to that observed in medium containing 0.2 mM EDTA. Anti-P-cadherin had a much weaker effect on cell proliferation than anti-E-cadherin, and cells grown in medium containing both antibodies grew at intermediate rates. The increased proliferation of the IHGK cells in either low calcium medium or Ca/Mg medium containing adhesion-blocking anti-cadherin antibodies suggests that cadherin-mediated adhesion is required for density-dependent regulation of growth of these cells.

Elevated temperature is one of 4 cardinal inflammatory signs. Previous work indicates that subgingival temperature assessments are accurate and re- liable, and provide objective, quantitative information over a broad 10 degrees C range, in small 0.1 degrees C increments with a direct, immediate report on the inflammatory status at the pocket base. However, complicating the use and interpretation of subgingival temperature assessments are its 3 forms: actual subgingival temperature, sublingual temperature minus subgingival temperature (temperature differential), and a temperature indicator light. We reasoned that if one could determine which of the temperature assessments reflected the periodontal condition, and which were independent variables, they would provide new and unique information about the inflammatory status of the periodontium. We also reasoned that by providing objective, quantitative data over a broad range, subgingival temperature should reduce the sample size required to obtain significance in clinical trials. Therefore, the purpose of this study was 2-fold: (1) to determine whether the 3 subgingival temperature assessments could differentiate between clinically defined periodontal health and disease; (2) to determine whether the 3 assessments were dependent or independent clinical variables. The data indicated that all 3 subgingival temperature assessment methods differentiated between clinically-defined periodontal health and disease (all p<0.02). All 3 assessments also correlated significantly (all p<0.03), but modestly (all r>0.49), with bleeding on probing. Based on scatter-plot matrices and common factor analysis, the data indicated that only actual subgingival temperature and temperature differential were independent variables. Taken together, this data indicates that subgingival temperature and temperature differential provide unique information about the periodontal inflammatory state. Power calculations indicated that the temperature differential may significantly reduce the subject number required to achieve significance in clinical trials examining gingival inflammation. Because of the body's rapid temperature response, these assessments may also significantly reduce the time required for gingival inflammation trials.