Evaluation of the shear bond strength of rebonded brackets with a high ARI index

Abstract

A common clinical problem in the orthodontic treatment is the accidental dislodgment of brackets. Rebonding these loose brackets require clinical chair time and is a nuisance as well as a costly process in the course of orthodontic treatment. The authorEs hypothesis was that the rebond strength of high ARI index brackets was different from new ones and that of low ARI index brackets. Objectives The aim of the current study was to compare the rebond strength of the high ARI index brackets with that of the low ARI index and also with the new brackets. Material and methods Initially 150 new brackets were gathered and underwent a bonding/rebonding procedure on human premolar teeth to achieve various ARI indices. The brackets were then rebonded (on 3 sets of 20 new human premolar teeth) as Group A : brackets with ARI score above IV (i.e IV+) ; group B: brackets with ARI score below II( i.e II-); group C: brackets with ARI score III. Group D (control group) included another twenty premolar teeth which were bonded with new brackets. The bond strengths were registered and evaluated using ANova analysis and Tukey follow up test to determine any significant difference. SPSS 17 software was utilized to analyze the data. Statistical significance was set at P<0.05. Results The ANova analysis indicated significant difference (P<0.05) between groups; Tukey follow up test indicated that ARI score IV+ brackets (group A) and also new brackets (group D) had significantly a higher rebond strength (13.98 Mpa and 15.67 Mpa respectively) than those of ARI score II- (8.05 Mpa) and score III(9 Mpa) brackets (P<0.05). However, no statistically significant difference existed between control and ARI score IV+ group. (P>0.05) Conclusion The findings suggest that dislodged brackets with high ARI score i.e score IV and V , are better candidates for rebonding purposes than those with low ARI index (i.e score I,II and III). New brackets had a comparable (but slightly more) shear rebond strength value than that of score IV+ brackets. As with any laboratory study, caution should be taken in extrapolating these findings to oral environment