Objectives: To evaluate the influence of angle of convergence(AOC) of abutment on fracture resistance and stress distribution of 3-unit all-ceramic FPD made of IPS-Empress2(E2). Methods: the study was performed in two parts; in first part forty extracted human premolars and molars were used to reproduce twenty 3-unit FPDs. Teeth were prepared similarly in two groups with AOC of 12 and 22 degrees, randomly assigned in 10 per group. FPDs were fabricated with uniform thickness (0.8 mm) of core material of E2, bonded to the corresponding models. Connector dimensions were set to 4 × 4 mm2 . Specimens underwent preload cycles (n=10,000, 40N, f=1.3Hz) loaded to fracture in a universal testing machine (1mm/m) and statically analyzed (Student t-test, P<0.05).In second part of study two 3-D finite element models were developed to simulate 3-unit FPDs with 12 and 22 degrees taper of abutments . Periodontium and cement layer were simulated. A 100 N force was applied vertically on the center of pontic.Results: mean failure loads and SD of 12 degrees and 22 degrees groups were 1009.12±208.05N and 1182.72±144.67N respectively. Student t-test revealed a significant difference (P=0.05) . Maximum compressive stress and maximum tensile stress occurred at the occlusal and gingival embrasure respectively. AOC of abutments had a significant influence on the maximum von misses and principal stresses in connector regions (20 % increase in maximum von misses and 9.5 % in maximum principal stresses in 12 degree model). There was no significant difference in stress pattern in cement layer for both situations. Conclusions: Fracture resistances of the investigated FPDs with AOC of 22 degrees of abutments were significantly higher than those with 12 degrees. Increasing the taper of abutments reduced the peak stresses .This study was funded by vice canceller of research of health administration of IRAN.

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