Prototype to measure bracket debonding force in vivo

INTRODUCTION Material biodegradation that occurs in the mouth may interfere in the bonding strength between the bracket and the enamel, causing lower bond strength values in vivo, in comparison with in vitro studies. OBJECTIVE To develop a prototype to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the prototype. METHODS A original plier (3M Unitek) was modified by adding one strain gauge directly connected to its claw. An electronic circuit performed the reading of the strain gauge, and the software installed in a computer recorded the values of the bracket debonding force, in kgf. Orthodontic brackets were bonded to the facial surface of 30 bovine incisors with adhesive materials. In Group 1 (n = 15), debonding was carried out with the prototype, while tensile bond strength testing was performed in Group 2 (n = 15). A universal testing machine was used for the second group. The adhesive remnant index (ARI) was recorded. RESULTS According to Student's t test (α = 0.05), Group 1 (2.96 MPa) and Group 2 (3.08 MPa) were not significantly different. ARI score of 3 was predominant in the two groups. CONCLUSION The prototype proved to be reliable for obtaining in vivo bond strength values for orthodontic brackets.