Efficacy of different strategies to treat root dentin eroded by liquid or gaseous hydrochloric acid associated with brushing abrasion.

OBJECTIVE: This study aims to evaluate how casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) associated with Nd:YAG or Diode laser affects dentin exposed to hydrochloric acid (HCl) with or without tooth brushing. DESIGN: One hundred and sixty human root dentin blocks were selected after they were initially eroded with liquid HCl (pH 1.2) 3x for one day. The blocks were divided into the following groups: G1- liquid HCl (HCl-l), G2- HCl-l + brushing, G3- gaseous HCl (HCl-g), and G4- HCl-g + brushing. Each group was randomly assigned to the following treatments (n = 10): A) Control (no treatment), B) CPP-ACP, C) CPP-ACP associated with Nd:YAG laser (lambda = 1064 nm) (40 mJ, 10 Hz, 0.4 W, 15 s), and D) CPP-ACP associated with Diode laser (lambda = 980 nm) (0.5 W, 200 mus, 15 s). The treatment with CPP-ACP (G2, G3 and G4) was applied on the dentine surface for 5 min. Erosion (6x/day/20 s) and erosion (6x/day/20 s) with abrasion (2x/10 s) were performed for five days. Dentin volume loss was determined by 3D confocal laser microscopy. Data were analyzed with two-way ANOVA and Tukey's tests. RESULTS: G1 - CPP-ACP (10.77 +/- 1.66) and CPP-ACP associated with Diode laser (9.98 +/- 0.89) showed lower volume loss in relation Control group (12.86 +/- 0.63) (p < 0.05). G2 - CPP-ACP associated with Diode laser (12.41 +/- 1.08) elicited lower volume loss as compared to the Control (14.42 +/- 1.24) (p < 0.05). As for G3 and G4, all treatments showed similar volume loss. CONCLUSION: CPP-ACP and CPP-ACP associated with Diode laser could control dental tissue loss in dentin eroded by liquid HCl. Moreover, CPP-ACP associated with Diode laser could effectively decrease dental tissue loss in dentin exposed to liquid HCl and brushing.