Effect of adhesive layer properties on stress distribution in composite restorations--a 3D finite element analysis.
OBJECTIVE
Teeth, adhesively restored with resin-based materials, were modeled by 3D-finite elements analysis that showed a premature failure during polymerization shrinkage and occlusal loading.


METHODS
Simulation of Class II MOD composite restorations with a resin bonding system revealed a complex biomechanical behavior arising from the simultaneous effects of polymerization shrinkage, composite stiffness and adhesive interface strain. Due to a polymerization contraction, shrinkage stress increases with the rigidity of the composites utilised in the restoration, while the cusp movements under occlusal loading are inversely proportional to the rigidity of the composites. The adhesive layer's strain also plays a relevant role in the attenuation of the polymerization and occlusal loading stresses.


RESULTS
The choice of an appropriately compliant adhesive layer, able to partially absorb the composite deformation, limits the intensity of the stress transmitted to the remaining natural tooth tissues. For adhesives and composites of different rigidities, FEM analysis allows the determination of the optimal adhesive layer thickness leading to maximum stress release while preserving the interface integrity. Application of a thin layer of a more flexible adhesive (lower elastic modulus) leads to the same stress relief as thick layers of less flexible adhesive (higher elastic modulus).
Ausiello
Pietro
P
Department of Cariology, School of Dentistry, University of Naples 'Federico II', Italy.
Apicella
Antonio
A
Davidson
Carel L
CL
D003188:Composite Resins; D019245:Compressive Strength; D003198:Computer Simulation; D018772:Dental Marginal Adaptation; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis / Q000379:methods*; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D008956:Models, Chemical; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*
D003188:Composite Resins; D011108:Polymers; D019279:Resin Cements