Purpose: The purpose of the study was to evaluate the fracture resistance of CAD/CAM fabricated monolithic zirconia FDPs with differently designed split pontics under simulating ageing conditions.
Methods: A total of 21 FDPs with split pontics were constructed over 21 dental epoxy resin casts representing missing mandibular first molar with a second premolar abutment of 0° angulation and a tilted second molar abutment of 25° angulation. The FDPs were divided into three groups (n=7) according to the split pontic design; Group (K): Keyhole, Group (B): Bone, Group (R): Relief cut. The cemented FDPs were subjected to thermocycling and mechanical loading in a chewing simulator equivalent to one-year clinical service. Fracture resistance of aged specimens was measured by a universal testing machine and followed by fracture mode detection by scanning electron microscope. One-way ANOVA and Bonferroni post-hoc tests were utilized to compare among groups. The significance level was set at P ≤ 0.05.
Results: There was a statistically significant difference among groups (P-value <0.001, Effect size =0.852). Pair-wise comparisons among the groups revealed that group (K) showed the statistically significantly highest mean fracture resistance (2148.6 ± 193 N), and followed by group (R) (1605.4 ± 286.2 N). While group (B) showed statistically significantly lowest mean fracture resistance (1027.6 ± 91.8 N).

Conclusions: The tested different split pontic designs of monolithic zirconia FDPs for tilted molar abutments demonstrated clinically acceptable fracture load values.