The effect of delay in practicing oral hygiene procedures on microhardness of enamel during bleaching with 15% carbamide peroxide

Abstract

Some alterations in enamel microhardness after exposure to carbamide peroxide under a variety of in vitro conditions, have been reported. Considering the importance of patientEs oral hygiene method during at-home bleaching periode and itEs probably effect on severing the enamel surface alterations, the aim of the present in-vitro study was considered to compare the effect of practicing oral hygiene procedures in different times (immediately after bleaching, after 1 hour and after 2 hours) on microhardness of enamel surface. Method and marerial: 80 enamel slabes (6 4 2mm) were prepared from human impacted third molar teeth that had been extracted by surgery. Subsequent to putting specimens in acrylic mold, the surface of enamel slabes were ground with diamond burs and aluminum oxide stones with diamond abrasive pastes. Then the samples were randomly devided into 4 groups and were tested with Vickers microhardness measuring machine to determine primary microhardness value. Then the bleaching process was done on samples for 21 days (6 hours per day) and daily brushing with toothpaste was done immediately, 1 hour and 2hours after bleaching in the test groups. In control group the specimens were not brushed. The samples were kept in the artificial saliva. Enamel microhardness was registered at the end of the bleaching period once again. Finally the difference between final and primary microhardness values was calculated and data was analyzed using Kruskal-Wallis non-parametric statistical tests (p<0.05). Results: The mean difference of microhardness alterations in baseline and after 21 days were not statistically significant among the study groups (p=0.59). Conclusion: Daily oral hygien process (brushing with flouridated dentifrice) immediately, 1 or 2 hours after daily bleaching with 15% carbamide peroxide resulted in no changes in enamel microhardness .