EFFECT OF TOOTH WHITENINNG AND REMINERALIZING AGENTS ON SURFACE AND COLOR CHANGES OF DENTAL HARD TISSUE.

Abstract

Objectives: To evaluate the effect of different tooth whitening agents on the erosion depth of enamel and dentin, and to evaluate the effect of application protocols involving two remineralizing agents on the surface roughness, microhardness and color change of bleached enamel. Methods: Specimens were prepared from sound extracted human molars. To evaluate the erosion depth, enamel and dentin blocks were randomly assigned to different bleaching agents treatment groups. Erosion depth was evaluated following treatment using polarized light microscope. To evaluate the effect of the application protocol of remineralizing agents (sodium fluoride and casein phosphopeptide-amorphous calcium phosphate) on surface roughness, microhardness and color change, specimens were randomly assigned to different treatment groups where each of two remineralizing agents were applied before, after or before-and-after bleaching. Measurements were compared between baseline and post-treatment. Surface roughness was assessed using a 3D profilometer. Microhardness was assessed using a Knoop microhardness device. Color measurements were evaluated instrumentally using a spectrophotometer based on the CIE LAB system. Visual color assessment was evaluated using a shade guide. Nonparametric statistical procedures were used to compare treatment groups with appropriate adjustment for multiple comparisons, specifying an overall significance level of 5%. Results: Different tooth whitening agents produced various degrees of dental erosion of enamel and dentin. The depth of the erosion caused by tooth whitening agents varied depending on the agent used. Surface roughness evaluation showed that all treatment groups had significantly lower surface roughness change (ΔRa) when compared with the bleaching alone, and higher ΔRa v when compared with the negative control group. Knoop Microhardness evaluation showed that all treatment groups had significantly lower change in microhardness when compared with the bleaching alone, and higher change in microhardness when compared with the negative control group except in one instance; there was no difference in the microhardness change between the group treated with sodium fluoride before bleaching when compared to the group treated with bleaching only. In terms of color assessment, all treatment groups showed significantly higher values of L* and lower values of b* and a* when compared to the negative control group. Based on the visual assessment of color change, all treated groups showed significantly more improvement in shade guide units than the negative control group. Conclusion: Within the limitations of this study, results show that some tooth whitening agents can produce various degrees of erosion of enamel and dentin. The application of sodium fluoride or casein phosphopeptide-amorphous calcium phosphate before, after or before-and-after bleaching produced various degrees of protection against the increase of surface roughness, decrease of microhardness of enamel without affecting the efficacy of the tooth-whitening treatment.