engleski

3D FEA Stress Distribution Analysis of Metal-free Crowns

Objectives: Understanding the stress distribution within the crown-tooth complex under occlusal loading, regarding design and material properties, is of outmost importance. The objective was to investigate biomechanics of metal-free crowns (all-ceramic and FRC crowns) under different loading conditions using the 3DFEA model of an upper first premolar, and to compare the results to those of the intact tooth under the same loading conditions. Methods: Definitions of geometry and volume for all particular segments of tooth morphology were derived from digitalized upper right first premolar cross-sections. The crowns were designed on circular shoulder type margin. The FEA was performed with NASTRAN software. Mechanical properites were acquired from average values in the literature. The final model consisted of 1684512 four-noded tetrahedral elements, 246510 nodes with a total of 739530 degrees of freedom. Boundary conditions were fixed on the outermost layer of alveolar bone. Single to tripodal contact accumulative static load values of 200N were applied occlusally. Results: Significant compressive stress values were concentrated at vestibular cervical margin of all-ceramics crown (-7, 39MPa), while both compressive and tensile stresses were present in core-layering ceramics interface, relative to point of loading. The all-ceramic crown transferred significantly higher stress to the alveolar bone compared to the ceromer-FRC crown (p<0, 05). The ceromer-FRC crown demonstrated high correlation to the intact tooth stress distribution values (R=0, 69). Conclusions: Greatest stresses induced during occlusal loading involve cervical crown margin, regardless of the crown material. The all-ceramics crown under functional loading causes high stress concentrations in the tooth supportive tissues. The 3D FEA obtained stress distribution explains mechnanical phenomena involved in typical clinical fractures of metal-free crowns.

3D FEA; metal-free crowns; stress distribution

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