Finite Element Analysis of Molars Restored with Ceramic Crowns

With improvement in material properties of ceramic restorative materials, these materials have been used as the definitive restoration material instead of the dental alloy, even in the posterior region. The incomplete fit of full crown restorations remains a critical problem for dentists, leading many researchers to study this problem. The distribution and magnitude of stress at any point can be precisely analyzed using finite element analysis. The geometry of tooth preparation has been the subject of many debates without clear evidence that one type of tooth preparation or method of fabrication provides consistently superior marginal fit. Two margin designs may be used for complete ceramic crowns: chamfer, and shoulder. The objective of this study was to evaluate, by finite element analysis, the influence of different marginal geometries (chamfer, shoulder) and preparation taper on the stress distribution in teeth prepared for ceramic crowns and in the restorations. A 3D model of a molar was created: intact teeth, unrestored teeth different marginal geometries: with chamfer, with shoulder preparations; the same tooth restored full ceramic crowns. These were exported in Ansys finite element analysis software for structural simulations. Maximal equivalent stresses were recorded in the tooth structures and in the restoration for all preparation types. In all cases the values were higher in the crowns. Shoulder preparation is the recommended preparation tooth design for ceramic crowns, from biomechanical point of view. Key-Words: molar, complete ceramic crown, marginal geometries, preparation taper, finite element analysis, stresses.