OBJECTIVE:
The aim of this study was to evaluate in vitro the shear bond strength of metallic orthodontic brackets to enamel using different bonding materials followed by thermal cycling.
METHODS:
A fluid composite resin (Transbond XT / 3M Unitek) and a resin-modified glass ionomer (Fuji Ortho LC / GC America Inc.) were evaluated. Eighty sound human premolars were randomly divided into eight experimental groups (n = 10), according to the material used and the number of thermal cycles: zero, 1000, 2000 and 3000 cycles. Bracket bonding was performed on the buccal surface of the teeth. After 24 hours, they were subjected to thermal cycling at temperatures ranging between 5° C and 55° C for 15 seconds each immersion. Shear bond strength was performed using a universal testing machine with a chisel-type tip at a speed of 0.5 mm / min. The bond strength data was analyzed using two-way ANOVA.
RESULTS:
No difference on shear bond strength was observed regarding the number of thermal cycles for each specimen (p = 0.873). A significant difference was found in shear bond strength between the bonding materials (p = 0.022), with significantly higher values for Transbond XT regardless of the number of thermal cycles.
CONCLUSION:
The number of thermal cycles did not significantly affect the bond strength of the adhesive materials investigated. The bonding agent Transbond XT showed higher bond strength than Fuji Ortho LC regardless of the number of thermal cycles.
Glass ionomer cements; Resin cements; Shear bond strength
