Class I and Class II restorations of resin composite: an FE analysis of the influence of modulus of elasticity on stresses generated by occlusal loading.
OBJECTIVE
It was the aim of the study to analyze by the FE method stresses generated in tooth and restoration by occlusal loading of Class I and Class II restorations of resin composite. On the basis of available information on the influence of the modulus of elasticity, the research hypothesis was that the marginal stresses would decrease with increasing modulus of elasticity of the restoration.


METHODS
A cylindrical tooth was modelled in enamel and dentin and fitted with a Class I or a Class II restoration of resin composite. In one scenario the restoration was bonded to the tooth, in another the restoration was left nonbonded. The resin composite was modelled with a modulus of elasticity of 5, 10, 15 or 20 GPa and loaded occlusally with 100 N. By means of the soft-ware program ABAQUS the von Mises stresses in enamel and dentin were calculated.


RESULTS
In the bonded scenario, the maximum stresses in the enamel were located at the occlusal margins (range 7-11 MPa), and in the dentin centrally at the pulpal floor (range 3.4-5.5MPa). The stresses decreased with increasing modulus of elasticity of the resin composite. In the nonbonded scenario, the stresses were higher in the dentin and lower in the enamel than in the bonded cases, and the influence of the modulus of elasticity was less pronounced. The marginal stresses in the restoration were below 6 MPa in the bonded scenario and below 3 MPa in the nonbonded scenario.


CONCLUSIONS
Occlusal restorations of resin composite should have a high modulus of elasticity in order to reduce the risk of marginal deterioration.
Asmussen
Erik
E
Department of Dental Materials, School of Dentistry, University of Copenhagen, 20 Nørre Alle, 2200 Copenhagen N, Denmark. ea@odont.ku.dk
Peutzfeldt
Anne
A
D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry*; D003198:Computer Simulation; D001840:Dental Bonding; D003743:Dental Enamel / Q000502:physiology / Q000648:ultrastructure; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000145:classification*; D003804:Dentin / Q000502:physiology / Q000648:ultrastructure; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D008954:Models, Biological; D013314:Stress, Mechanical; D013499:Surface Properties
D003188:Composite Resins; D003764:Dental Materials