Faculty Bibliography

This study evaluated the effect of the elastic modulus and margin configuration on the clinical performance of resin-based composite restorations in Class V non-carious defects. One hundred and five cervical non-carious defects on buccal surfaces of canines and premolars were included in this study. Defects were randomly divided into three Groups and restored according to the following techniques: Group 1--no enamel bevel was placed and the defect was restored with a microfilled resin-based composite (Durafill VS); Group 2--the enamel margin was beveled and the defect restored as in Group 1; Group 3-the enamel margin was beveled and the defect was restored with a flowable resin-based composite (Natural Flow). Each group comprised 35 lesions. A total-etch, one-bottle adhesive (One-Step) was used in all groups. Retention rate, pre- and post-operative sensitivity, marginal discoloration and secondary caries were determined over a three-year period and the data were analyzed statistically. At six months post-insertion, the restorations placed with beveled enamel margins resulted in 100% retention regardless of the composite used compared to a 66% retention of the non-beveled margins. At two and three years, no significant difference in retention rate was found among the three groups. Post-operative sensitivity, marginal discoloration and secondary caries were not affected by enamel beveling and restorative material. Beveled enamel margins resulted in significantly better clinical retention in the first six months only. Enamel beveling and composite viscosity appeared to not significantly affect the clinical performance of Class V non-retentive composite restorations after three years.

PURPOSE/OBJECTIVE:This study evaluated the effect of two home bleaching regimens (1 h/day versus 7 h/day for a total of 21 days) on the microhardness of superficial enamel treated with 10% carbamide peroxide gel. MATERIALS AND METHODS/METHODS:Rectangular enamel specimens (2.5 x 2.5 x 1 mm) were obtained from human third molars and mounted on the palatal aspect of removable orthodontic retainers. Nine enamel specimens were mounted in each of 10 retainers, used by 10 volunteers during the active phase of the study. Modified 0.089 cm thick bleaching trays were fabricated for each participant. Each bleaching tray fit a participant's arch and the retainer containing the enamel specimens. Enamel specimens were treated with a 10% carbamide peroxide bleaching gel (Nite White Excel 2Z, Discus Dental, Culver City, CA, USA) for either 1 h/day (n = 30) or 7 h/day (n = 30), both for 21 days. Three enamel specimens in each retainer were never treated and served as controls. The retainers were worn by the participants whether or not they underwent bleaching. This simulated the natural action of the saliva/oral fluids on the enamel specimens. Enamel specimens were subjected to pre- and post-treatment microhardness measurements. Post-treatment Knoop hardness numbers were compared with baseline values and analyzed statistically. RESULTS:Bleaching treatment resulted in a nonsignificant reduction in microhardness values when compared with values of the control nontreated specimens (1.7% and 2.5% reduction in hardness for 1 h/day and 7 h/day, respectively). There was no difference in microhardness between the different treatment regimens. CONCLUSION/CONCLUSIONS:Home bleaching with 10% carbamide peroxide for up to 7 h/day for 21 days does not significantly affect enamel microhardness. CLINICAL SIGNIFICANCE/CONCLUSIONS:Bleaching with 10% carbamide peroxide for 1 h/day or 7 h/day for a total of 21 days is safe for human enamel.

PURPOSE/OBJECTIVE:To evaluate the influence of occlusal load cycling on cervical microleakage of proximal slot restorations located in dentin, using two self-etching and two one-bottle dentin adhesive systems. MATERIALS AND METHODS/METHODS:240 proximal slot cavities were prepared in 120 bovine teeth and divided into two groups, one with load cycling and one without. The groups were then subdivided into four subgroups according to the adhesive system used (Experimental EXL 547 Self-etching 3M, Clearfil SE Bond, Single Bond, and Optibond Solo Plus) and restored following the manufacturers' instructions. The teeth were then submitted to mechanical load cycling with a force of 80 N and a frequency of 5 Hz, simultaneously over both restorations of each tooth, for a total of 50,000 cycles per specimen. All specimens were subsequently immersed in a 2% methylene blue solution (pH 7.0), and sectioned to examine the extent of dye penetration under a stereomicroscope (40X). RESULTS:There was no statistically significant difference (p = 0.00002) between the loaded and unloaded teeth. However, a statistically significant difference was observed between the adhesive systems used. The experimental self-etching EXL 547 presented the lowest mean microleakage, but was only statistically significantly different from the Single Bond loaded and unloaded groups and the Clearfil SE Bond unloaded group. CONCLUSION/CONCLUSIONS:The application of 50,000 loading cycles did not affect the microleakage of the two self-etching and the two one-bottle adhesive systems evaluated. In vitro mechanical load cycling is an important factor to consider when evaluating the performance of adhesive systems under simulated masticatory conditions.