EFFECT OF MATRIX COMPATIBILITY AND SURFACE TREATMENT ON THE REPAIR BOND STRENGTH TO AGED COMPOSITE.

Abstract

This study was carried out to evaluate the tensile bond strength of the repair joint between an aged composite material when repaired by the same material and when repaired by a different one using different surface treatment repair protocols. Ten whole hour-glass slabs from each composite material serving as this study’s positive control, 100 half-slabs from an Ormocer composite material were made in an especially designed split copper mold all stored in tab water for six months. After six months the 80 half-slabs of the 100 were divided in to 2 groups according to the repair material used (40 by the Ormocer composite, 40 by the nanohybrid composite), then each group was further sub-divided into 4 sub-groups according to the surface treatment received (cutting bur, finishing bur, cutting stone, finishing stone) after which they were etched, rinsed, received a coat of a universal adhesive and the repair material was applied. The rest of aged half-slabs (n=20) were used as a negative control, where each 10 received one of the repair materials, but with no mechanical nor chemical treatment applied. All slabs were tested for TBS. Tensile bond strength of the repair joint was evaluated using a universal testing machine at crosshead speed 0.5mm/min. Data was collected and analyzed using SPSS version 17.0. Fractured surfaces were examined using stereo-microscope at X16 magnification. The results showed that the type of repair material, the sturface treatment performed, and their interaction all had a statistically significant effect on the tensile bond strength of the repair joint. Repairing using Admira showed higher repair tensile bond strength than Grandio. Using finishing stone as a surface treatment showed the highest repair tensile bond strength while cutting bur showed the least repair tensile bond strength. Failure mode analysis results of Admira groups showed 77.5% mixed, 15% cohesive and 7.5% adhesive while Grandio groups showed 62.5% mixed, 10% cohesive and 27.5% adhesive. Under the limitations of this study, several conclusions can be drawn: 1- Composites used for repair should be of a similar matrix to the repaired composite. 2- Abrasives are preferably used to prepare the composite surface for repair.