The aim of this study is to compare the shear bond strength of two self ligating brackets with a conventional bracket which have different base designs. Ninety extracted premolar teeth for orthodontic reasons without cracks or caries were used in the study. Teeth were randomly divided into three groups. In group 1 conventional brackets (Synergy, Rocky Mountain Orthodontics, Denver, Colorado, USA), were used whereas in group 2 and 3 self ligating brackets [(Smart Clip, 3M Unitek Monrovia, California, USA) and (Time 2, American Orthodontics, Sheboygan, Wisconsin, USA)] were used respectively. The determined mean shear bond strengths for Synergy, Smart Clip and Time 2 brackets were 18.2±4.4, 18.7±4.6 and 17.7±5.1 MPa, respectively. Generally more adhesive was left on the tooth surface as demonstrated by ARI scores of three. All of the three groups with different base designs, one conventional bracket and two self-ligating brackets, demonstrated clinically acceptable mean shear bond strengths in vitro. Most of the fractures were within resin-bracket interface.

Keywords: Bond strength, Self ligating brackets, Conventional brackets