Effect of preparation height on stress distribution in premolars restored with pressed ceramic crowns

Little information regarding variation of basic preparation guidelines in stress distribution of teeth covered with ceramic crows has been available. The incomplete fit of full crown restorations remains a critical problem for dentists, leading many researchers to study this problem. Finite element analyses have been used for many investigations, because they can reproduce structures of various shapes of teeth with many elements defined with specific Young’s modulus and Poisson’s ratio values. In this manner, the distribution and magnitude of stress at any point can be precisely analyzed. 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. The objective of this study was to evaluate, by finite element analysis, the influence of preparation height on the stress distribution in teeth prepared for full ceramic crowns and in the restorations. A 3D model of a premolar was created: intact teeth, unrestored teeth; the same teeth restored with 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 heights. In all cases the values were higher in the crowns. In all cases the maximal equivalent stress values were higher in the crowns. The stresses are distributed around the contact areas with the antagonists. The preparation height is not significant for stress distribution. Key-Words: premolar, complete ceramic crown, preparation height, finite element analysis, stresses.