The effect of microetching on the bond strength of metal brackets when bonded to previously bonded teeth: an in vitro study.

The purpose of this in vitro study was to answer the following questions for three different metal brackets: (1) when rebonding a previously bonded tooth, how do shear bond strengths compare for new brackets, new microetched brackets, and debonded microetcher cleaned brackets? and (2) how do the different bracket types compare with respect to the time required to remove composite resin from their bonding pads with a microetcher? Ninety human premolars and canines previously debonded of metal brackets were randomly assigned to 9 groups of 10 teeth each. New, new etched, and debonded etched cleaned brackets of each type were bonded with composite resin onto teeth, and the bonds tested to failure for shear bond strength. An analysis of variance and Duncan's multiple range test were used to compare bracket/enamel bond strength. Within each bracket type no significant differences were found between mean bond strengths for new, new etched, and debonded etched conditions, a finding that supports the use of microetching to clean accidentally debonded brackets. Mean times for removal of resin from bonding pads with a microetcher varied from 9.3 seconds to 11.9 seconds, with bracket (M) requiring significantly less time for removal of resin.