Bond strength of rebonded orthodontic brackets

A study was undertaken to determine the bond strength of brackets rebonded with a no-mix resin system or a paste-paste resin system. The efficacy of plastic conditioner and Enhance adhesion booster (Reliance Orthodontic Products, Inc., Itasca, Ill.) as an aid in rebonding was also evaluated. Sixty extracted human premolars were divided into two groups based on the two adhesive systems used. Both groups of 30 were subdivided and (1) initial bond, (2) rebond, and (3) rebond using plastic conditioner and adhesion booster. Samples were stressed to bond failure using an Instron machine. Bond separation occurred in the majority of samples at the enamel/resin interface. Mean bond strengths ranged from 78.8 kg cm-2 for rebonding with a no-mix adhesive and no other conditioners, to 182.7 kg cm-2 for initial bonding using a paste-paste adhesive. Rebonding using a paste-paste adhesive with no other conditioners produced a bond strength statistically indistinguishable from initial bonding with either system. Plastic conditioner and adhesion booster failed to improve rebond strength. The data suggest that, given certain circumstances, rebonding is a viable option when a bracket has been debonded.