Effect of arch wire ligation on shear bond strength of metal brackets

Abstract EN

Background: This study evaluated the effect of ligating different arch wires on the amount of force needed to debond a bracket and the effect that has on the bond strength of the adjacent brackets.

Materials and methods: Sets of 5 human maxillary first premolar teeth where attached together by acrylic resin and bonded to .022 slot brackets.

The sets where randomly split into five groups.

Four test groups were characterized by ligating the 5 brackets by an arch wire (SS .019x.025, SS .021x.025, NiTi .019x.025, and NiTi .021x.025).

A fifth group served as control having no ligated arch wire during debonding.

The brackets were debonded by a debonding pliers attached to an Instron Universal testing machine.

After debonding the middle bracket, the arch wire was removed and the adjacent and terminal brackets were debonded.

Then the teeth were examined with enhanced digital images to evaluate the site of failure according to the Adhesive Remnant Index (ARI).

Results: Compared to control, the bond strength of the middle brackets in all the test groups was significantly increased and the adjacent brackets significantly decreased.

Higher bond strengths of the middle brackets were associated with the use of SS and .021x.025 arch wires rather than NiTi and .019x.025 arch wires, respectively.

The most common type of failure was between the bracket and the adhesive.

Enamel cracks were found less frequently in the test groups than in control.

Conclusions: It is advised to start debonding from one side of the arch to the other rather than starting in the middle of the arch to have an adjacent bracket from one side only.

Keywords: Bond strength, arch wire ligation (J Bagh Coll Dentistry 2007; 19(1): 81-87).