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Objectives: This in situ trial study was designed to evaluate whether calcium (Ca) pre-rinse would increase the fluoride (F) rinse protection against enamel erosion., Methods: Fifteen volunteers participated in this split-mouth, 3-phase, crossover design study wearing a palatal appliance containing four sterilized bovine enamel slabs, for 10 days. In the 1st phase, five participants followed protocol A: daily rinse with a Ca lactate (CaL, 150mmol/L, 1min), followed by F (NaF 12mmol/L, 1min). Other five participants followed protocol B: daily rinse only with F, while the remainders followed protocol C: no rinse (negative control). Appliances were removed from the mouth and one side of the palatal appliance was exposed to a daily erosive challenge (0.05M citric acid, 90s); the other side served as control (deionized water - no erosion). In the 2nd phase volunteers were crossed over to other protocol and in the 3rd phase volunteers received the remaining protocol not yet assigned. Specimens were evaluated for surface loss using an optical profilometer., Results: Repeated-measures three-way ANOVA (p=0.009) and Tukey's test showed that CaL pre-rinse followed by NaF rinse significantly decreased surface loss of enamel when performed prior to an erosive challenge in comparison with the condition in which NaF only was used., Conclusions: Pre-rinse with CaL may increase the protection exerted by NaF against erosive wear., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: Because the effects of dental bleaching on enamel needs to be clarified in vivo, the authors conducted a study to determine calcium and phosphorus concentrations in enamel after the application of different bleaching treatments., Methods: The authors applied four agents (10 percent and 20 percent carbamide peroxide [both recommended for home use], 38 percent and 35 percent hydrogen peroxide [both applied in the dental office]) to the enamel of 80 participants, who were divided into four groups of 20. The authors collected enamel microbiopsy specimens from incisors before (baseline), during (seven, 14 and 21 days) and after (seven and 14 days) the bleaching treatments. They analyzed calcium and phosphorus concentrations by using a spectrophotometer., Results: The authors analyzed data by using the Friedman test and the Kruskal-Wallis test, followed by the Dunn test (α= .05). There were no statistical differences between the evaluation results, regardless of which bleaching gel was used, for determining the concentration of either calcium or phosphorus., Conclusions: Home-use and in-office bleaching gels did not alter the concentrations of calcium and phosphorus concentrations on the enamel surface in vivo., Clinical Implications: In vivo, different dental bleaching techniques did not alter the inorganic composition of enamel.

Background: The authors conducted an in situ study of the influence of various time intervals after tooth bleaching with 35 percent hydrogen peroxide on the bond strength of resin-based composite restorations., Methods: After selecting 20 participants, the authors randomly fixed enamel and dentin blocks onto the buccal surfaces of posterior maxillary teeth one week before performing tooth bleaching with 35 percent hydrogen peroxide. After the bleaching treatment, they removed one block of dentin or enamel and prepared it for the bond strength tests according to these time intervals: no bleaching treatment (controls), immediately after bleaching, seven days after bleaching, 14 days after bleaching and 21 days after bleaching., Results: The analysis of variance and Tukey test showed significant differences between times (P<.05), and shear bond strength values of resin-based composite to enamel and dentin were lower immediately after the bleaching treatment., Conclusions: The authors found that 35 percent hydrogen peroxide reduces the bond strength to enamel and dentin and that it is necessary to wait seven days before performing adhesive restorative procedures., Clinical Implications: The results of this study suggest that clinicians should allow seven days to elapse after completion of in-office bleaching with 35 percent hydrogen peroxide before placing adhesive restorations.