The fracture performance of adhesively bonded orthodontic brackets: an experimental-FE modelling study

As people pay more attention to the aesthetics of teeth, the adhesion of brackets in the orthodontic process received a wider application in recent years. In this paper, experiments and finite element method (FEM) were combined to study the mechanical behaviour of adhesively bonded orthodontic brackets, as well as fracture performance in the adhesive layer. The tensile, shear and mode I/II fracture testing were carried out first to determine reliable parameters of the adhesive for numerical simulation. Quasi-static tensile-shear loading was applied to determine the failure strength of bracket bonded with enamel. Bi-linear cohesive element was inserted to simulate the failure process of the adhesive layer. The failure strength obtained by experiments and FEM were 8.25 MPa and 9.15 MPa, respectively, with deviation of 9.8%. The load-displacement curves obtained by simulation and experiment were in acceptable agreement. The damage propagation and stress distribution in the adhesive layer and enamel during tensile-shear loading were then analysed. The proposed FE method can be used to predict the bonding strength of brackets, and thus provide reliable reference for the force applied during clinical treatment and possible fracture mechanism during daily use of orthodontic brackets.