Biomechanical behavior of endodontically treated premolars restored with different endocrown designs: Finite element...

Although endocrown is a successful restorative approach for endodontically treated molars, its survival rate in endodontically treated premolars with extensive loss of coronal structure has been debated. The aim of this study was to evaluate the biomechanical behavior of endodontically treated maxillary premolars restored with different lithium disilicate endocrown designs.

Based on cone-beam computed tomography (CBCT) of an intact maxillary premolar, five models were designed. Model A: fiber post, core, and crown; Model B: endocrown, 5 mm pulpal extension and butt margin; Model C: endocrown, 5 mm pulpal extension and axial extension; Model D: Endocrown, 3 mm pulpal extension and butt margin; Model E: Endocrown, 3 mm pulpal extension and axial extension. The bone geometry was simplified as a cylinder of compact and trabecular bone. All models were imported into finite element analysis (FEA) software, where the base of the bone cylinder was chosen as fixed support. Axial and oblique loads of 100 N each were applied separately to each model, and static structural analysis was performed.

Regardless of the design of the endocrown, the resulting von Mises stresses were far below the yield strength of the tooth structure and the flexural strength of the ceramic material. The generated von Mises stresses on the restoration decreased by 15% in the models with 3 mm pulp extension (D and E) compared to the 5-mm pulpal extension models. In addition, the resulting von Mises stresses on the tooth structure decreased also by 15% in models C and E with the axial extension compared to models B and D with the butt margin.

Endocrown is a suitable restoration for endodontically treated maxillary premolars. Furthermore, reducing the depth of the pulpal extension to 3 mm with the addition of an axial extension resulted in a more favorable stress distribution within the tooth-restoration interface.