Effect of Thermal Cycling on Shear Bond Strength with Different Types of Self-etching Primer for Bonding Orthodontic Brackets using a MMA-based Resin

The purpose of this study was to determine the bonding durability when orthodontic bracket was bonded to human enamel using a MMA-based resin (Multibond) with two types of commercially available self-etching primer—Multibond and Megabond. Multibond primer contained a polymerization initiator, but Megabond primer did not. No significant differences in shear bond strength were observed between Multibond and Megabond primers after immersion in water at 37°C for 24 hours (before thermal cycling). Multibond primer produced no significant decrease in shear bond strength after 2000 and 5000 thermo-cycles between 5°C and 55°C. On the contrary, Megabond primer showed significant decrease in shear bond strength after thermal cycling. The present study suggested that if Multibond resin were to be used for bonding orthodontic brackets, difference in self-etching primer's components would influence shear bond strength after thermal cycling.