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Shear bond strength of brackets bonded with two light-curing orthodontic adhesives.

PURPOSE
To compare the shear bond strength of stainless steel brackets bonded with two orthodontic adhesive systems, Transbond XT (3M Unitek) and Orthobond (Morelli Dental Products).


MATERIALS AND METHODS
Forty bovine teeth were randomly divided in two groups of 20 each: group 1 (control): Transbond XT primer + Transbond XT Adhesive paste (3M Unitek); group 2: Orthoprimer (Morelli Dental Products) + Orthobond. In each group all teeth were etched with 37% phosphoric acid, and all products were used according to manufacturers instructions. After 30 min, a universal testing machine was used to apply an occlusal shear force directly to the enamel/bracket interface at a speed of 0.5 mm/min. The groups were compared using Student's t-test.


RESULTS
Mean results and standard deviations for the groups were: group 1= 11.22 Mpa (1.68), group 2= 4.88 Mpa (1.18). A significant difference was observed in the bond strengths of the two groups evaluated (p < 0.0001).


CONCLUSION
Under the conditions of this study, Orthobond system presented lower shear bond strength when compared to Transbond XT.