Aim: To determine whether normal temperature variations in an orthodontic office have any effect on the shear bond strengths and the types of bond failure of two adhesives, a composite and a resin-reinforced glass ionomer. Material and Methods: Eighty-seven freshly extracted human molars were collected and stored in a solution of 0.1% thymol. The teeth were cleansed and polished and randomly separated into four groups, according to the type
of adhesive and the temperature of the adhesive at the time of bonding: group 1, teeth bonded with a glass-ionomer adhesive refrigerated at 4°C; group 2, teeth bonded with a glass-ionomer adhesive kept at room temperature (22°C); group 3, teeth bonded with a
composite adhesive refrigerated at 4°C; group 4, teeth bonded with a composite adhesive kept at room temperature (22°C). The brackets in all four groups were debonded within 30 minutes from the time of the initial bonding. This was meant to simulate the bond strength at the time of the initial archwire tying during orthodontic treatment. A steel rod with one
flattened end was attached to the crosshead of a Zwick test machine. An occlusogingival load was applied to the bracket, producing a shear force at the bracket-tooth interface. Results: The results of the analysis of variance comparing the four experimental groups (F=15.5) indicated the presence of significant differences between the groups (P = .0001). Specifically, the bond strength of the refrigerated (4°C) resin-reinforced glass-ionomer
adhesive was significantly lower than that of the other three groups. Conclusion: Temperature variation affects the resin-reinforced glass-ionomer adhesive more than the composite adhesive in the first 30 minutes after bonding. As a result, refrigerating the resin-modified glass-ionomer adhesive to increase the number of brackets bonded with one capsule will have a significant short-term effect on bond strength. World J Orthod 2002;3:154–158.