Centric relation definitions taught in 7 dental schools: results of faculty and student surveys.

PURPOSE: The purpose of this investigation was to assess the level of consensus regarding the definition of centric relation and its clinical use in 7 US dental schools. MATERIALS AND METHODS: The preclinical and clinical faculty in the departments of prosthodontics, operative, and general dentistry (n = 137) at 7 dental schools and a convenience sample of fourth year students (n = 150) at the same schools were invited to complete 2-page surveys regarding the definitions and use of centric relation at their institutions. The faculty and student survey included 6 commonly used centric relation definitions from the 1994 Glossary of Prosthodontic Terms, and provided space for writing in definitions not listed on the form. The participants were asked to identify which definition was used at their school. RESULTS: Return rate was 85% for faculty and 75% for students. Both faculty and students identified a low level of consensus regarding the definition and clinical use of centric relation at their dental school. Numerous definitions are in use at each institution. Extramural practice participation and the number of years since dental school graduation were variables associated with the faculty's choice of definition. The faculty who did not participate in an extramural practice chose older definitions. Dental educators graduating before 1975 selected either the oldest or the most recent centric relation definition, whereas the more recent graduates frequently selected the newer definitions. There were no statistical differences between prosthodontic specialists and nonspecialists in choice of definitions. Three courses identified by the students as having the most influence on their understanding of centric relation were preclinical removable prosthodontics, preclinical occlusion, and clinical removable prosthodontics. CONCLUSION: The results of this survey suggest that the controversy will continue, because to date there is no consensus regarding the definition of centric relation within the 7 dental schools surveyed.

Salivary mucin as related to oral Streptococcus mutans in elderly people.

MG1 (MUC5b and MUC4) and MG2 (MUC7), predominant mucins in human whole saliva, provide lubrication and antimicrobial protection for oral tissues. This study examines potential relationships between Streptococcus mutans titers in the oral cavity and the following: mucin concentrations; unstimulated and stimulated whole saliva flow rates; decayed, missing, and filled tooth surfaces; and age of 24 elderly patients. S. mutans titers were determined using Denticult SM. Mucin concentrations were determined using Stains-all, sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Logistic regression was used to identify potential relationships between the above variables. S. mutans classification served as the dependent variable. The remaining variables were possible predictor variables. The best model for predicting S. mutans category contained log MG2 as a predictor variable for all of its parameter estimates. No other set of parameter estimates were statistically significant. These results suggest that elevated S. mutans titers are significantly associated with diminished concentrations of MG2 in unstimulated whole saliva, as quantified in mucin-dye binding units.

Effect of peroxide bleaches on fluoride release of dental materials.

PURPOSE: To investigate the effect of two bleaching agents, 35% hydrogen peroxide (Superoxal) and 10% carbamide peroxide (Opalescence), on the release of fluoride from Ketac-Fil, a glass ionomer cement, Photac-Fil, a glass ionomer/resin hybrid; and Tetric, a resin composite with fluoride. MATERIALS AND METHODS: Seven disks (9 x 3 mm) of each material were immersed in Superoxal for 1 hour to simulate an in-office application; seven other disks of each material were immersed in Opalescence 1 hour daily for 7 days to simulate a week of home bleaching regimen; and seven additional disks of each material without bleach served as a control. The disks were kept in deionized water and the water was tested for fluoride released every 24 hours for 14, 21, 28, and 35 days, respectively. RESULTS: Repeated measures ANOVA showed that the mean daily release of fluoride did not differ significantly (P > 0.05) between the bleaching agents or the control: Superoxal 6.17 ppm, Opalescence 6.45 ppm, and control 6.50 ppm. Statistically significant differences (P < 0.05) occurred for mean daily fluoride (+/- standard error) released from the three materials over the 35-day period: Photac-Fil 12.31 +/- 0.48 ppm > Ketac-Fil 7.07 +/- 0.66 ppm > Tetric 0.12 +/- 0.01 ppm, respectively.

The effects of peroxide bleaching on composite to enamel bond strength.

OBJECTIVES: The objective of this in vitro study was to evaluate the effects of an in-office type of bleaching regimen on the composite to enamel bond. METHODS: The enamel on forty extracted human teeth was subjected to a 25% hydrogen peroxide bleaching treatment. Ten additional unbleached specimens served as controls (Group A). The 40 bleached specimens were divided into four equal groups (Groups B-E). Composite cylinders were bonded to the prepared surfaces at various time intervals following bleaching. Group B was bonded immediately, Group C at 1 d, Group D at 1 wk, and Group E at 1 mon post-bleaching. RESULTS: Mean shear bond strength values showed a significant decrease in bond strength for Group B. However, the bond strength returned to normal values after 1 d and remained normal for at least 1 mon. Scanning electron microscope examination showed an apparent decrease in the number of resin tags present in the enamel/composite interface for Group B compared with the other groups including controls. SIGNIFICANCE: Polymerization inhibition of the resin bonding agent is the likely mechanism for the effects of the bleaching on bond strength.