To assess stress distribution patterns of an endocrown restoration of a maxillary-central-incisor restored with four different restorative materials by three- dimensional Finite-Element-Analysis (FEA).
Method:
Tree-dimensional maxillary-central-incisor FE model was created by Micro CT (SkyScan 1174- Kontich, Belgium) scanning of an extracted human maxillary-central-incisor and CAD/CAM endocrown-restoration with four different restorative materials;1) Incoris-TZI (monolithic-zirconia, Sirona-dental) 2) IPS e-max-CAD (lithium-disilicate glass-ceramic, Ivoclar-Vivadent), 3) CEREC-Blocs (feldspar-ceramic, Sirona-dental) 4) Lava-Ultimate (resin-nano-ceramic, 3M-ESPE) was designed to perform simulations. Materials used in the study were assumed as homogenous and isotropic. Each mathematical model included 19215 nodes and 13062 tetrahedral solid elements. Incisal force of 300 N was applied from palatal surface of the crown at 1350 angle to tooth long axis. Nodes at outer surface of the root were assumed as fixed in all directions to calculate stress distributions. The FE modeling was accomplished with SolidWorks software program and analyses were run at CosmosWorks integrated with it. Results were presented, as tensile and compressive stresses since the materials investigated were brittle. Calculated numeric data were transformed into color graphics.
Result:
Stress distributions revealed in all groups that with applied functional load, compressive stresses were generated in buccal cervical region while tensile stresses were seen in palatal cervical region. Intensive tensile stress distributions were observed around restoration margins and dentin tissues in Incoris-TZI monolithic-zirconia and e-max-CAD glass-ceramic. Stress values and localizations were decreased in sirona feldspar-ceramic, and the least stress localizations were seen in lava-ultimate nano-resin ceramic.
Conclusion:
1. Material difference caused an effective change in generated stress type and quantity under functional loads.
2. In models of materials with high modulus of elasticity, extensive stress concentrations were observed within materials inner structures, while in models of materials with lower modulus of elasticity stress distributions in dental structures were more localized, however higher.