Early versus delayed rebonding of orthodontic brackets.

There are controversial reports regarding the effect of repeated bonding on shear bond strength (SBS) of orthodontic attachments. The aim of this study was to evaluate the SBS of brackets following early and delayed rebonding, and after employing different methods of composite removal. Sixty eight premolars were randomly assigned into 4 groups. After initial debonding and recording the SBS, the adhesive remnants in the first group were removed by a round bur, in the second group by a green rubber wheel, and in the third and fourth groups by 12-fluted tungsten carbide burs, all of them connecting to a low speed handpiece. In the fourth group following adhesive removal, the teeth were kept in a simulated oral environment for one month. Then, rebonding was performed and the second SBS was measured. Two representative samples from each group were examined under a scanning electron microscope following adhesive removal. The data were analyzed by ANOVA, Paired sample t-test and Chi-Square test. In the first group, the rebonding strength was decreased significantly (p<0.05), while composite removal with a tungsten carbide bur or a green rubber wheel did not affect SBS significantly (p>0.05). Late rebonding of brackets had no effect on the SBS (p>0.05). Postponing rebonding to the next visit does not improve the SBS significantly. It is recommended to use a tungsten carbide bur or a green rubber wheel, and not a round bur for removing adhesive remnants following debonding of orthodontic brackets.