3D-finite element analyses of cusp movements in a human upper premolar, restored with adhesive resin-based composites

The combination of diverse materials and complex geometry makes stress dist ribution analysis in teeth very complicated. Simulation in a computerized m odel might enable a study of the simultaneous interaction of the many varia bles. A 3D solid model of a human maxillary premolar was prepared and expor ted into a 3D-finite element model (FEM). Additionally, a generic class II MOD cavity preparation and restoration was simulated in the FEM model by a proper choice of the mesh volumes. A validation procedure of the FEM model was executed based on a comparison of theoretical calculations and experime ntal data. Different rigidities were assigned to the adhesive system and re storative materials. Two different stress conditions were simulated: (a) st resses arising from the polymerization shrinkage and (b) stresses resulting from shrinkage stress in combination with vertical occlusal loading. Three different cases were analyzed: a sound tooth, a tooth with a class II MOD cavity, adhesively restored with a high (25 GPa) and one with a low (12.5 G Pa) elastic modulus composite. The cusp movements induced by polymerization stress and (over)functional occlusal loading were evaluated. While cusp di splacement was higher for the more rigid composites due to the prestressing from polymerization shrinkage, cusp movements turned out to be lower for t he more flexible composites in case the restored tooth which was stressed b y the occlusal loading. This preliminary study by 3D FEA on adhesively restored teeth with a class II MOD cavity indicated that Young's modulus values of the restorative mate rials play an essential role in the success of the restoration. Premature f ailure due to stresses arising from polymerization shrinkage and occlusal l oading can be prevented by proper selection and combination of materials. ( C) 2001 Published by Elsevier Science Ltd.