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Comparison of wire loop and shear blade as the 2 most common methods for testing orthodontic shear bond strength


Authors: Mojtahedzadeh F, Akhoundi MS, Noroozi H
Am J Orthod Dentofacial Orthop., Vol.130, No.3, 2006,Page:385-357

Abstract

INTRODUCTION:

The purpose of this study was to compare 2 common methods of measuring orthodontic shear bond strength.

METHODS:

Brackets were bonded to 40 bovine incisors, and the teeth were mounted in a jig. The teeth were paired for symmetry, and the pairs were divided into 2 groups for debonding. In group 1, the shear force was applied with a rectangular wire under the tie wings. In group 2, a shearing blade applied force to the junction between the bracket base and the adhesive.

RESULTS:

Debonding with the shear blade produced higher (24.86 +/- 7.44 MPa) and more dispersed (coefficient of variation = 29.91%) bond strengths compared with the wire loop (17.12 +/- 3.16 MPa, coefficient of variation = 18.44%). Adhesive remnant index (ARI) scores showed a tendency for cohesive failure in the enamel in the shear-blade group (ARI = 5) compared with adhesive failure (ARI = 3) in the wire group.

CONCLUSIONS:

There is a need to standardize bond strength tests. The results of this study favor the wire-loop method, which might have more similarity to clinical loads. The regression formula might make comparison of previous stu