Avaliação da resistência de união à microtração de sistemas adesivos à dentina – influência da umidade

Abstract

The aim of this study was to evaluate the microtensile bond strength of adhesive systems in the total etching technique on different substrates. Twenty extracted human third molars were selected and divided into four groups according to the adhesive system to be used and the technique applied: 1. Single Bond Universal – Humid dentin; 2. Adper Single Bond 2 – Humid dentin (control group); 3. Single Bond Universal – Dry dentin; 4. Adper Single Bond 2 – Dry dentin. After realization of occlusal cut of the teeth in order to expose the dentin surface, the specific technique of hybridization was performed to each group followed of the restoration of the dental elements. After 24 hours of immersion in distilled water, restored elements were cut to obtain prism-shaped specimens - of dentin, adhesive interface and restorative material - which were submitted to the microtensile bond strength test. After the test, the fractured samples were examined under optical microscope and classified according to the mode of fracture. Data of the microtensile bond strength were analyzed by the T test (p<0.05) and the analysis of fracture of the specimens was presented by means of descriptive statistics. With respect to the effect of the dentin surface condition, there was no statistically significant difference between Single Bond Universal groups (humid: 51.33 MPa; dry: 51.97 MPa; p>0,05); however, the difference between the two groups of Adper Single Bond 2 was statistically significant (humid: 51.19 MPa, dry: 25.96 MPa; p=0.0001). Comparing the two adhesive systems, in humid dentin there was no statistically significant difference between them (p> 0.05); however, for dry dentin the difference between the two adhesive systems was statistically significant (p = 0.0001). The predominant type of fracture, in both groups, was the mixed fracture - cohesive in the adhesive and in the hybrid layer. It is concluded from this study that the Single Bond Universal can be used in both conditions of the dentin surface, dry and humid, being equivalent to the humid technique of Adper Single Bond 2, without impairing the bond strength of direct restorations.