Reflection intensity of enamel submitted to bleaching and desensitizing therapies

Objectives: To analyze the effect of dental bleaching (DB) and desensitizing toothpastes on surface reflection intensity (SRI) and the SRI association with enamel shade and roughness.
Methods: 42 bovine incisors were divided into 7 groups, n=6 (G1: control; G2: Toothpaste 1+DB; G3: DB+Toothpaste 1; G4: Toothpaste 2+DB; G5: DB+Toothpaste 2; G6: Toothpaste 3+DB; G7: DB+Toothpaste 3). Three bleaching sessions were realized on the 1^st (T1), 7^th (T7) and 14^th days (T14). SRI was measured using optical reflectometer initially (T0), at T1, T7, T14 and on the 21^st day (T21). Dental shade was measured using CIE L*a*b* system at T0 and T21. Roughness (Ra, RMS) was evaluated with atomic force microscopy at T21. Intraclass Correlation Coefficient (ICC) assessed inter-rater agreement on SRI measurements and Bland-Altman plots. Data were compared within groups by Friedman/Dunn-Bonferroni tests. Pearson correlation test evaluated SRI association with shade, Ra, and RMS.
Results: SRI measurements presented excellent inter-rater agreement (ICC=0.873). Bland-Altman plot showed that, on average, the difference between R2 and R1 was 0.68. T1xT21 and T7xT21 for G1; between T0xT14 after desensitizing application for G3; between T0xT7 and T0xT14 both after desensitizing application for G4 and G6; and between T0xT7 after desensitizing application for G7. For all groups, no significant difference between T0xT21 was found. Moderate negative correlation was found for SRI and Ra (r=-0.602), RMS (r=-0.501).
Conclusions: Optipen reflectometer provided excellent inter-rater agreement. Tooth bleaching associated desensitizing toothpastes application and storage in artificial saliva did not affect initial SRI. SRI was negatively associated with enamel roughness.