Fracture resistance of fixed partial dentures supported by different abutment combinations: an ex vivo study

This study sought to compare the fracture resistance of and categorize failure modes exhibited by fixed partial dentures (FPDs) supported by natural teeth, implants, or mixed tooth-implant abutments. Three groups utilized three different abutment combinations: all natural teeth, all implants, and a mixture of teeth and implants. The teeth were prepared and zero-angled titanium abutments were installed over the implants. Standardized conventional three-unit porcelain-fused-to-metal FPDs were fabricated, following the conventional ceramic build-up technique. The inner surfaces of the bridges were air-abraded (50 μm Aluminum Oxide at 80 psi), cleaned in an ultrasonic bath for 10 minutes, and cemented over abutments using glass ionomer cement. The FPDs were fixed in a universal testing machine and compressed to fracture using a three-unit metal block at a 5 mm/minute crosshead speed. Fracture loads ranged from 460 to 5,700 N. Bridges supported by either implant abutments only or mixed implant-tooth abutments showed higher fracture loads (2,940 and 3,390 N, respectively) than those supported entirely by natural teeth (1,386 N) (p < 0.05). However, fracture of the veneering porcelain was common among all types of abutments.