EFFECT OF IRRIGATION PROTOCOLS ON THE DENTIN AND ON THE FILLING MATERIAL BOND-STRENGTH

Abstract

The aim of this study was to compare the effect of different final irrigation protocols on the dentinal structure and filling material bond-strength (BS) to dentin. One hundred and eight teeth were instrumented and distributed into four groups, according to the final irrigation protocol: CG (control) – EDTA + passive ultrasonic irrigation (PUI); G1 – 3 PUI cycles (20s each): NaOCl + EDTA + NaOCl; G2 – EDTA (PUI 30s) + NaOCl (PUI 30s); G3 – EDTA + NaOCl + H2O + CHX (PUI 30s each). After protocols, each group were submitted to three tests: three-point flexural strength (n=48), microhardness (Knoop) (n=12) and filling material BS dentin (push-out) (n =48). Dentinal erosion was assessed using scores assigned to Scanning Electron Microscopy images. Data normality was verified by Shapiro-Wilk. Data were statistically analyzed (ANOVA and Tukey – flexural strength and push-out resistance; Student's t test – microhardness; Kruskal-Wallis and Friedman – erosion, with ?=5%). For flexural strength, there was no statistical difference among groups. For microhardness, a difference was detected, except in the GC group. In the push-out, the middle and apical thirds of G2 presented higher values (p<0.05). CG showed significantly lower erosion scores than G1, G2 and G3, and G1 was higher than G3 (p<0.05). There were no differences between root thirds. It was concluded that different protocols caused dentinal erosion and changed its microhardness, but did not affect its flexural strength. The combined protocol of EDTA + NaOCl, for 30s each, presented the best results regarding the filling material bond-strength to dentin.