Tensile bond strength and stress distribution of endocrowns on maxillary central incisors: effect of CAD/CAM material and resin cement

To evaluate the tensile bond strength (TBS) and stress distribution of endocrowns fabricated from three CAD/CAM materials and cemented with four resin cements in maxillary central incisors using 3D finite element analysis (FEA). One hundred and twenty extracted maxillary central incisors were endodontically treated and prepared for endocrowns. Specimens were assigned to 12 subgroups ( n = 10) according to restorative material - feldspathic ceramic (FC), monolithic zirconia (MZ), or resin-nano ceramic (RNC) - and luting cement - Panavia SA (SA), Super-Bond C&B (SB), Clearfil Esthetic Cement (ES), or Variolink II (V). After thermocycling (5,000 cycles), TBS was measured at 0.5 mm/min, and failure modes were classified under stereomicroscopy and SEM. For FEA, a micro-CT-derived model was loaded with 300 N at 135° on the palatal surface. Data were analyzed with two-way ANOVA, Tukey’s, and Fisher’s exact tests (α = 0.05). The luting cement significantly affected TBS ( p = 0.001), whereas the restorative material did not ( p = 0.305); the interaction was significant ( p = 0.015). SB produced the highest TBS in the MZ (5.85 MPa) and RNC (5.35 MPa) groups; SA produced the lowest in the RNC group (2.98 MPa). Cohesive failures dominated in the FC group (69.2%); mixed failures dominated in the MZ (40–80%) and RNC (55.6–90%) groups. Peak stresses were similar across models (7.58–7.91 MPa); stress accumulation in dentine increased in the order RNC < FC < MZ. The luting cement was the primary determinant of bond strength; Super-Bond C&B paired with a resin-nano ceramic substrate offered the most balanced bond strength and stress distribution for endocrowns on endodontically treated maxillary central incisors.