Effect of Resin Composite Type and Deep Margin Elevation Configuration on Stress Distribution in an Endodontically Treated Maxillary Second Premolar: A Finite Element Analysis

Deep margin elevation (DME) relocates deep subgingival restorative margins, but biomechanical differences among resin composite types and DME configurations remain unclear. This study compared three resin composites in modeled 1 and 2 mm DME configurations in an endodontically treated maxillary second premolar using three-dimensional finite element analysis. Eight models were analyzed: an intact tooth, a restored reference model, and six DME configurations using Tetric EvoFlow, Filtek Supreme XTE, or Filtek Z100 beneath a lithium disilicate restoration. A 34 MPa distributed occlusal pressure and a 50 N static force were applied simultaneously. Principal stresses were assessed for enamel and lithium disilicate, whereas von Mises stress (VMS) was evaluated for dentin, DME composite, and resin cement. Tensile strength-based screening, threshold-exceeding volume fractions, path-based displacement, and ESTRN were also evaluated. Compared with corresponding 1 mm configurations, 2 mm configurations showed lower enamel tensile stress by 16.1–32.6%, enamel compressive stress magnitude by 16.2–32.4%, dentin VMS by 20.1–33.5%, and DME composite VMS by 8.5–8.7%. Lithium disilicate stresses generally decreased, whereas resin cement showed a material-dependent response. Displacement was generally higher in 2 mm configurations, while maximum ESTRN generally decreased in enamel, dentin, DME composite, and lithium disilicate. Threshold-exceeding enamel volumes ranged from 0.14% to 1.87%; only M5-FZ100-1 exceeded 124 MPa in IPS e.max CAD, involving 0.04% of the restoration volume. Under the modeled conditions, biomechanical responses differed between 1 and 2 mm DME configurations and among composite types, without establishing overall superiority of any material or configuration.