Effectiveness of Current at-home Bleaching and Over-the-counter Bleaching Products and Changes on Dental Enamel Surface Hardness After Whitening

Objectives: The aim of this study was to evaluate the effectiveness of at-home bleaching and over-the-counter bleaching systems and changes on microhardness of dental enamel after whitening.
Methods: One hundred bovine enamel blocks (5mm x 5mm) were divided into groups (n=10) according to the bleaching treatment: Whiteness Perfect 22% (WP); 3D White Whitestrips (WS); Whitening toothpaste Rembrandt Deeply White (RD) and Mouthwash Plax Whitening (PW). Artificial saliva (AS) was the control group.Three color measurements were performed with a spectrophotometer: untreated samples (baseline), after performing staining, and after application of bleaching agents. Microhardness was measured at same end points. Data were subjected to one-factor analysis of variance (ANOVA), and Tukey’s test (P<0.05).
Results: Baseline and after staining colour measurements revealed homogeneity on △E values of all groups (p>005). WP, WS, and PW showed similar bleaching effectiveness with a significant difference to the control group (p>0.05). From all experimental groups, WP has shown the best whitening effect. The lowest △E values have been seen in RD and AS groups (p>0,05). Before bleaching the microhardness of all samples were similar (p=0,851). After bleaching WP and WS showed a significant reduction on enamel hardness (p<0,05). There was a negative correlation between whitening effectiveness and superficial enamel hardness values (r = –0,8762).
Conclusions: It was concluded that PW has no bleaching action whereas WP, WS and PW were effective as bleaching agents. PW and WS reduced the surface enamel microhardness after whitening.