Purpose: Although endodontically treated molars restored with endocrowns have been reported to be clinically successful, clinical and in vitro studies indicated more frequent problems with endodontically treated premolars restored with endocrowns. The aim of this finite element study was to evaluate the influence of the pulpal extension on the stress distribution in endodontically treated maxillary premolars restored with endocrowns.
Materials and methods: An intact maxillary first premolar tooth without any obvious abnormalities or decay was scanned using Planmeca ProMax 3D Mid cone-beam CT machine, the 3D models of enamel and dentin were then segmented using MIMICS software. Three design models were created as follow: Model (A) represented the classical ceramic crown with glass fiber reinforced post and a composite resin core , model (B) represented the endocrown preparation of a circular butt-margin with the depth of the central retention cavity extending 5 mm in depth from the occlusal floor, and model (C) represented the endocrown preparation of a circular butt-margin with the depth of the central retention cavity extending 3 mm in depth from the occlusal floor. Bone geometry was simplified and simulated as a cylinder that consisted of an outer shell of compact bone and an inner core of trabecular bone. All the design models where remeshed and exported to Ansys Workbench as volume meshes for the finite element analysis. The base of the bony cylinder was selected as a fixed support, and an axial oblique load of 100 N was applied to each model. Material properties were assigned for every model, and static structural analysis was performed.
Conclusions: Within the limitations of this finite element study, it was concluded that endocrowns offered a viable alternative for restoration of endodontically treated maxillary premolars, and increasing the pulpal extension to 5 mm significantly increased the stress distribution in the endocrown under axial forces.