ADHESIVE INTERFACE BETWEEN DENTIN SURFACE AND COMPOSITES OF DIFFERENT VISCOSITIES.

Abstract: Introduction:Direct composite restorations are popular in dentistry, but the main reasons for failure in the posterior sector are recurrent caries and fracture. Although there is no consensus on the best restorative technique in adhesive dentistry, the polymerization contraction stress of a composite can be a challenge, resulting in mismatch of the tooth-restoration interface.Aim: The objective of this study was to evaluate the adaptation of high and low viscosity composite restorations to the dentin substrate. Materials and methods: Healthy third molars (n=10) were used and preserved in distilled water at 37ºC. A calibrated cavity was made with Jota diamond conical stone No. 846KRF.031. with Gacela Evo Lux turbine at a speed of 150,000 rpm. The teeth were randomly grouped into two groups (n= 5). The dentin substrate of both groups were treated with the selective etching technique with Ultraetch phosphoric acid (Ultradent) on enamel and One Coat 7 Universal adhesive system (Coltene) according to the manufacturer's instructions. It was photopolymerized with a SPEC3 LED device (Coltene). Then a 1 mm layer of Brilliant Flow resin (Coltene) was applied and finally it was placed in a monoblock of Everglow resin (Coltene). The samples of the other group were received to the same treatment except for the flowable composite layer. The samples were sectioned with a diamond disc cutter (DHUC Model Micro Disc NH-6P). The 1 mm thick sections were analyzed with a Zeiss microscopic magnifying glass - Model Axio Imager A1m with a SONY cybershot-3X optical zoom digital camera mod DSC w180 with monitor. Four measurements of the frequency of discontinuity between the material and dentinal substrate were recorded for each sample. The results were statistically analyzed using the two-tailed Mann-Whitney test. RESULTS: The mean and standard deviation values of each group were: Group 1: 1.2 (0.80), group 2: 2.4 (0.5). The analysis with the two-tailed Mann-Whitney Test showed a significant difference for the material factor (p<0.05). CONCLUSION: Under the experimental conditions of this work, it can be concluded that the use of flowable composite in direct restorations would improve the adaptation of the restoration-tooth structure interface.