Effect of application of an additional hydrophobic resin layer on the repair shear bond strength of silorane-based composite

Abstract

Composite repair is considered a minimally invasive and conservative approach following failures of composite restorations. The aim of this study was to evaluate the effect of application of an additional hydrophobic layer on the repair shear bond strength of silorane - based composites with silorane - based and methacrylate - based composites. Materials and Methods: Twenty cylindrical composite blocks (Diameter: 2.5 mm, height: 6mm) were prepared for measuring the cohesive strength of silorane-based composite (Positive Control Group). Sixty disc shaped composite blocks were prepared by packing composites into cavities made in Acrylic Blocks (5.5 5.5 3.5 mm) . The samples were categorized into three groups according to intermediate agents and the type of repairing composite: Group 1) Silorane composite - Silorane Bond - Silorane composite, Group 2) Silorane composite E Silorane Bond E Hydrophobic Resin E Silorane composite, Group 3) Silorane Composite E Silorane Bond E Hydrophobic Resin E Methacrylate-based Composite . The samples were stored in normal saline for 72 hours. Then the surface of the samples were roughened by diamond burs and then etched by phosphoric acid .After that the composites were repaired. The dimensions of the repairing composite were 2.5 2.5 5 mm. After the Composites were repaired , they were stored in normal saline for 24 hours .Then they were Thermocycled (1500 rounds, 5-55 c, each poolEs time: 20 s, dwell time: 10 sec). In the end the repair bond strength of the samples were measured with the loading rate of 1mm/min. The data were statistically analyzed by One-way ANOVA and the Post hoc Tukey test (P<0.05). Results: The One-way ANOVA test showed that there is a significant difference between repair shear bond strength of groups. None of the groups reached the cohesive bond strength of silorane - based composite.The one by one comparison of the groups by Tukey test showed that cohesive bond strength of silorane composite is significantly higher than all the other groups (P<0.001). It also showed that repair bond strength of group 3 was significantly higher than group 2(P=0.001) but there wasnEt a significant difference between group 2 and 3 (P=0.20) and between groups 1 and 2(P=0.18) .Reviewing failure modes showed that cohesive failure mode was highest in group 4 and adhesive failure mode was highest in group 3. Conclusions: Application of an additional hydrophobic layer in repairing silorane - based composite with methacrylate - based composite enhanced the repair shear bond strength of the silorane - based composite