Bond strength of three orthodontic adhesives.

A method was devised to study the bond strength of direct-bonding orthodontic adhesives. A shear load was applied parallel to the tooth-adhesive-bracket interface by means of an Instron Universal Testing Machine. The bond strength was found to increase for some products after 27 days. However, no significant differences could be detected 1 day after placement. The interface was studied to determine the mode of failure. In all cases bond failure occurred as mixed adhesive-cohesive phenomena.