Effect of treatment of dental-substrate associated with the self-etching adhesive

Objectives:To evaluate the microtensile bond strength of indirect restoratives fixed with self-etching system under influence of different previous treatments of enamel and dentin. Methods:Thirty bovine incisors were extracted and the roots were removed from the crown in the cementum-enamel junction. The labial teeth surfaces were grounded even exposition of superficial dentin and the standardizing the smear layer. The specimens were divided into three groups (n=10): G1: One Up Bond F (Tokuyama Corp., Tokyo, Japan) (OB) following the instructions of manufacturer; G2: OB with previous acid conditioning with phosphoric acid 37% in enamel and dentin; G3: OB with previous sandblasting with 50µm aluminum oxide in enamel and dentin. Composite restoratives were fixed using dual cement (RelyX, 3M-ESPE, St Paul, USA) under load of 500g for 5min. The samples were serial cutted with adhesive area of ± 1,0 mm² in 3 regions: enamel (E), peripheral dentine (DP) and central dentine (DC). Then, they were tested at 0.5mm/min in a microtensile testing machine (EMIC DL 2000, São José dos Pinhais, Brazil). After fracture, the specimens were examined under SEM to determine the mode of failure for test specimens. Mean tensile strength values were expressed in MPa and data were analyzed by one-way ANOVA, followed by Tukey test (p<0.05). Results:The results were: E/G2: 30,4±11,9a; E/G3: 16,0±8,9b; E/G1: 15,8±5,8b; DP/G1: 24,2±12,1a; DP/G3: 15,2±7,1b; DP/G2: 15,0±9,8b; DC/G1: 17,3±10,4a; DC/G3: 11,6±3,5b; DC/G2: 11,4±5,2b. Conclusions:The previous acid conditioning in enamel increased the bond strength values. The association of air abrasion and acid conditioning in dentin decreased the values of bond strength test.