Avaliação da influência do modo de fixação dos corpos de prova no ensaio de microtração na resistência de união à dentina

Abstract

Aims: 1) To evaluate the microtensile bond strength (&#956;MTBS) of the square rod shaped (SRS) specimens when fixed on its ends or in the lateral position; 2) to evaluate the &#956;MTBS of the SRS fixed by dentin or composite resin on the moving attachment (MA) from the universal testing machine (UTM).Materials and methods: Twenty third molars sound and extracted had the occlusal surface removed exposing the dentin. Right after, the teeth were restored with the PQ1 adhesive system and Amelogen Plus doing a 6.0mm height composite resin layer according to the microtensile methods. Then, the specimens were cut in square rods with a bond area of 0.64 mm2. From each tooth were selected four samples of the central area and randomly divided in four groups as follows: TB composite resin positioned on the mobile attachment (MA) from the UTM; BT dentin positioned on MA from the UTM; NTB specimens attached to the notched jig (NJ) with the composite resin fixed on the MA; and NBT- specimens attached to the NJ with dentin fixed on the MA. After, the &#956;MTBS testing was performed with a crosshead speed of 0.5mm/min.Results: The mean values of microtensile bond strength in MPa were (means followed by the same letter did not differ significantly at p<0.05) (Tukey`s test): TB- 26.67 (B); BT- 31.90 (AB); NTB- 37.85 (A); and NBT 34.26 (A).Conclusions: The sample position (TB or BT) on the MA did not influence the &#956;MTBS; the SRS lateral immobilization (NTB and NBT) applying the NJ increased the &#956;MTBS