Effect of Different Irradiation Patterns on Shear Bond Strength of Composite Resin to Enamel and Dentin

Abstract

Statement of Problem: With more polymerization rate there would be less time for the composite to flow and consequently sudden hardening occurs. This leads into composite detachment from cavity walls resulting in microleakage between the restoration and tooth, and will decreas the bond strength.Purpose: The aim of this study was to investigate the shear bond strengths of the enamel and dentin-resin composite using Suggested Progressive program (SUP) and some other light exposure patterns.Materials and Method: In this experimental in vitro study, the test groups were composed of 40 dentinal and 40 enamel samples prepared on facial surfaces of 80 human canine teeth. 2x2mm polyethylen cylandric molds were filled in bulk with Tetric Ceram composite and were placed on the prepared surfaces. Irradiation patterns for 4 groups of 10 dentinal and 10 enamel samples were as follows: Group1, HIP (High Intensity Program). Group 2, LOP (Low Intensity Program). Group3, PUL (Pulse Program) of Astralis 7 light curing unit exposure patterns, and Group 4, SUP (Suggested Progressive Program). After curing and 24 hours incubation in 37°c, the samples were thermocycled under 500 cycles (5-55°c), and mounted with acrylic resin. Shear bond strengths of all samples were obtained using the Instron testing machine with 0.5 mm/min crosshead speed. For statistical analysis, one way and two way ANOVA and Duncan testes were used by SPSS software.Results: There was no significant difference between the shear bond strengths of four light exposure patterns in dentinal and enamel groups ( p<0.001). It was also revealed that various light exposure patterns had no significant effect on shear bond strength of composite to enamel and dentin ( p=0.388).Conclusion: SUP light exposure pattern has the same capability of producing appropriate bond strength with the tooth structures as other light exposure patterns.Key words: Shear bond strength, Light exposure pattern, Light intensity, Suggestive Progressive Program