3D-finite element analysis and weibull analysis of maxillary first molar restored with endocrowns with different pulpal extensions compared with conventional crowns with post-and-core.

BACKGROUND

Rehabilitation of endodontically treated teeth with large coronal destruction is still a clinical challenge. No established guidelines specify where a conventional crown with fiber-reinforced composite (FRC) post-and-resin core or an endocrown (EC) is indicated and which material or pulpal extension should be used.

OBJECTIVE

To provide evidence for restoring severely damaged maxillary first molar (MFM) by comparing the fracture and debonding resistance after being restored with the ceramic EC and the conventional zirconia crown and FRC post-and-resin core.

METHOD: Models of a MFM with a mesial-occlusal-distal-palatal defect with different restoration strategies were created: C-FRC -- conventional crown with FRC post, EC-Zr-3/4/5 - zirconia EC with 3-/4-/5-mm pulpal extension, EC-Li-3/4/5 - lithium disilicate EC with 3-/4-/5-mm pulpal extension. Two loading conditions were applied: vertical loading - a 400-N force along the tooth's long axis; lateral loading - a 225-N force at a 45-degree angle buccally to the tooth's long axis. Three-dimensional finite element analysis and Weibull analysis were conducted for the above seven models.

RESULTS

The C-FRC group obtained the lowest maximal Mohr-Coulomb stress ratio (MσMC ratio) in the residual tooth structure under both loadings (0.2646 and 0.2815, respectively). The lowest MσMC ratio in the cement was in the EC-Li-5 group under both loadings (0.07660 and 0.3177, respectively). The lowest maximal shear stress at the adhesive interface was in the EC-Li-3 group under both loadings (5.700 MPa and 20.48 MPa, respectively).

CONCLUSIONS

The conventional crown with FRC post-and-resin core is still suitable for restoring a MFM with a mesial-occlusal-distal-palatal defect. Lithium disilicate EC with 3-mm pulpal extension may be a choice for the MFM where conventional restoration is not applicable.