Thermo-debonding mechanisms in dentin bonding systems using finite elementanalysis

The finite element method (FEM) has been extensively used in evaluating the interfacial status of biomaterials. We used FEM to explore the microscopic debonding mechanism of the dentin/hybrid layer/resin adhesive interface. T he stress status of the local material was used as an index to judge whethe r the adhesive interface would develop a debonding mechanism. To generate t he local stress concentration, the thermal boundary condition was applied t o the model which has the phenomenon of the coefficient of thermal expansio n (CTE) mismatch. The thermal boundary condition was used to emulate a prev ious study conducted with a laser thermoacoustic technique (LTAT). The mate rials, Scotchbond MP, Optibond, and Tenure bonding systems, used in the pre vious experiment were also tested in this study. The results show that inte rfacial debonding in the finite element model occurred through the hybrid l ayer for both the Scotchbond MP and Tenure systems, as well as within the a dhesive layer itself for the Optibond system. These findings are compatible with observations by SEM obtained by LTAT. Another transformed model was c reated to test the "elastic cavity wall" concept. The result also confirms the importance of the elastic cavity wall concept. These compatible results between FEM and LTAT indicate that FEM can be a very useful supplement to thermoacoustic testing. (C) 2000 Elsevier Science Ltd. All rights reserved.