The effect of dentin roughness on the shear strength of resin-bonded bridges

Abstract

Debonding is the main problem of resin bonded prostheses in the case of dentin exposure. The aim of this study was to evaluate the effect of different surface roughness of dentin on the shear bond strength of resin bonded prosthesis Material and methods:Sixty intact incisor extracted due to periodontal disease were selected. The buccal , incisal and proximal surface enamel of the teeth were removed by a low speed diamond disk .The buccal surfaces of the dentin were wet-ground with silicon carbide paper. The specimens were then divided randomly into 4 groups. The groups were divided according to the final grit size of the diamond rotary cutting instruments used. Super coarse (150-180 ?m), coarse (125-150 ?m),medium (106-125 ?m) and fine (45 ?m). Final impressions of the prepared teeth were made with silicone impression material. 60 metal plates (4mm 4mm) were made individually with the lost wax technique and cast with a commercial nickel-chromium metal alloy. Internal surface of castings were abraded with aluminum oxide particle, then were cemented to the teeth with Panavia-EX cement. Specimens were placed in the shear testing machine to evaluate the shear strength. Axial force was applied by the blade of the machine to the tooth-casting interface. Load which led to dislodgement were recorded in megapascal .Data were analyzed by SPSS software and ANOVA and Pos hoc Tukey test. Results: Mean ( SD) of shear strength in the super coarse group, coarse group ,medium group and fine group were (17/751/41) ;(13/821/13); (10/491/45) ;(7/131/18) respectively. This difference was statistically significant (P=0/001). Conclusions: Increasing surface roughness of dentin is an effective method of improving the shear strength of resin bonded bridges