Effect of pontic volume on fracture resistance of three-unit metal-ceramic fixed dental prostheses: an in vitro and finite element analysis study

This study evaluated the effect of pontic volume on the fracture resistance of three-unit metal-ceramic fixed dental prostheses (FDPs) using in vitro fracture tests and finite element analysis (FEA). Three pontic volume configurations (Small, Medium, and Large) were designed for mandibular posterior three-unit FDPs with second premolar and second molar abutments. Cobalt-chromium (Co-Cr) alloy frameworks were fabricated by direct metal laser sintering. For each configuration, 10 specimens with only metal and 10 specimens with feldspathic porcelain veneers (1.5 mm) were prepared ( N = 60). FEA was performed on metal frameworks under a vertical load of 500 N. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) post-hoc tests(α = 0.05). Average fracture loads ranged from 5284.1 ± 228.85 N to 6093.5 ± 330.34 N in the metal group and from 1506.0 ± 183.41 N to 1935.8 ± 153.06 N in the porcelain group. All differences between groups were statistically significant ( P <.05). FEA showed that the maximum von Mises stress at the connector decreased from 740 MPa to 325 MPa as the pontic volume increased. In all groups, fractures occurred predominantly at the connector. Increasing the pontic volume significantly improves fracture resistance in both metal and porcelain-veneered restorations. Framework-only FEA showed a reduction in connector stress with increasing pontic volume, which is consistent with the direction of the in vitro findings.