Biomechanical Behavior of Maxillary Premolars with Non-carious Cervical Lesions: Influence of Minimally Invasive Endodontic Access and Restoration Protocols.

Introduction: Non-carious cervical lesions (NCCLs) compromise tooth structure and may cause inflammation requiring endodontic treatment. This study evaluated the influence of endodontic access design on fracture resistance, failure patterns, and stress distribution in maxillary premolars with wedge-shaped NCCLs restored using different restorative strategies.

Methods: One hundred maxillary premolars were divided into ten groups based on access type (sound and NCCL with traditional, minimally invasive, and no access) and restorative material (provisional, conventional composite, high-viscosity bulk-fill resin, or low-viscosity bulk-fill resin combined with conventional resin composite). NCCLs were standardized, endodontic treatments performed, and restorations applied. After thermocycling, specimens underwent fracture resistance testing and failure mode analysis. One tooth was scanned for finite element analysis (FEA).

Results: The sound group and the minimally invasive access group restored with high-viscosity bulk-fill resin had numerically higher fracture resistance. No significant difference was found between traditional and minimally invasive access. Adhesive protocols performed significantly better than temporary restorations (P < .05). Type III (nonrestorable) fractures predominated (50%-90%). FEA revealed stress concentrations in the buccal cusp, central groove, marginal ridges, and cervical region, with similar patterns across groups and slightly lower stress in minimally invasive access.

Conclusions: Endodontic access preparation reduced the fracture resistance of maxillary premolars with noncarious cervical lesions; however, the access design itself did not significantly influence this outcome. FEA revealed similar stress distribution patterns across all groups, regardless of access type. Adhesive restorative protocols, especially those employing bulk-fill composites, enhanced biomechanical performance compared to provisional restorations. These findings underscore the importance of minimally invasive access in preserving structural integrity and highlight the critical role of adhesive strategies in restoring biomechanical function.