Effect of thermocycling on shear bond strength of a conventional etch and rinse adhesive system

Aim: The objective of this study was to determine the effect of thermocycling on shear bond strengths (SBSs) of a light cured compositeafterdifferent thermal cycles.Materials and methods: ۸۰ Bovine incisors were randomly divided into ۴ groups of ۲۰ teeth. Each teeth were etched with ۳۷% phosphoric acid and brackets were bonded using a light cured composite (Resilience). Thermocycling was done between ۵° C and ۵۵° C for ۵۰۰, ۳۰۰۰ and ۶۰۰۰ cycles in group ۲,۳ and ۴ respectively. Teeth in group۱ (control group) were not being thermocycled. The SBS values were measured by means of Dartec testing machine. Results: The results showed significantly higher SBS values for the control group compared to test groups (۲-۳ and ۴). No significant different was observed between test groups. Conclusion: Thermal changes during thermocycling significantly reduce the mean SBS of conventional etch and rinse adhesive system (Resilience), but SBS in ۵۰۰, ۳۰۰ and ۶۰۰۰ cycles had no significant difference. Clinical significance: Alteration in values of shear bond strengths under thermocycling would be representative of expected behavior of orthodontic brackets in clinical situations.

Keywords:

Shear Bond Strength , thermocycling , Bracket