fracture strength of three-unit implant supported fixed partial dentures with excessive crown height fabricated from different materials

objectives: fracture strength is an important factor influencing the clinical long-term success of implant-supported prostheses especially in high stress situations like excessive crown height space (chs). the purpose of this study was to compare the fracture strength of implant-supported fixed partial dentures (fpds) with excessive crown height, fabricated from three different materials. materials and methods: two implants with corresponding abutments were mounted in a metal model that simulated mandibular second premolar and second molar. thirty 3-unit frameworks with supportive anatomical design were fabricated using zirconia, nickel-chromium alloy (ni-cr), and polyetheretherketone (peek) (n=10). after veneering, the chs was equal to 15mm. then; samples were axially loaded on the center of pontics until fracture in a universal testing machine at a crosshead speed of 0.5 mm/minute. the failure load data were analyzed by one-way anova and games-howell tests at significance level of 0.05. results: the mean failure loads for zirconia, ni-cr and peek restorations were 2086±362n, 5591±1200n and 1430±262n, respectively. there were significant differences in the mean failure loads of the three groups (p<0.001). the fracture modes in zirconia, metal ceramic and peek restorations were cohesive, mixed and adhesive type, respectively. conclusions: according to the findings of this study, all implant supported three-unit fpds fabricated of zirconia, metal ceramic and peek materials are capable to withstand bite force (even para-functions) in the molar region with excessive chs.