Effect of bracket bevel design and oral environmental factors on frictional resistance

Objective: To investigate the effects of bracket bevel design and oral environmental factors (saliva, temperature) on frictional resistance. Materials and Methods: Five types of brackets, namely a conventional bracket (Omni-arch), an active self-ligating bracket (Clippy), and three passive self-ligating brackets (Carriere, Damon, and Tenbrook T1) coupled with a 0.014-inch austenitic nickel-titanium archwire were tested. In the experimental model, which used a group of five identical brackets, the center bracket was displaced 3 mm to mimic the binding effects. The friction experiments were performed at three temperatures (20 C, 37 C, 55 C) in a dry or a wet (artificial saliva) state. Finally, the surfaces of the bracket slots were observed using scanning electron microscopy (SEM) before and after the friction tests. Results: The sliding frictional force was significantly influenced by the bracket slot bevel and saliva whether in the active or passive configuration (P < .05). The frictional force significantly increased as the temperature increased in the active configuration (P < .01). Based on the SEM observations, a correlation was found among the level of frictional force, the bevel angle, and the depth of scratches on bracket bevels. Conclusion: Frictional force can be reduced by increasing the bevel angle and by lowering the oral temperature, whereas the presence of saliva increases frictional resistance.