Fracture load of cantilevered implant‐supported prostheses of varying heights fabricated from additively and subtractively manufactured resins

PURPOSE: The purpose of this in vitro study was to evaluate the fracture load, both before and after aging, of implant-supported cantilevered prostheses with different prosthesis heights fabricated additively using an experimental resin and a commercially available resin, or subtractively from a high-impact polymer composite. MATERIALS AND METHODS: Three cylindrical master files (20 mm long and 11 mm wide) were designed in three heights (7 mm, 11 mm, and 15 mm), each containing a space for a titanium-base (Ti-base) abutment. Using these files, a total of 108 specimens were fabricated from an additively manufactured resin for definitive fixed partial dentures (TR), an additively manufactured experimental resin (SA), and a subtractively manufactured high-impact polymer composite (BR) (N = 12 per material-height pair). After fabrication, the specimens and corresponding Ti-base abutments were treated according to their manufacturers' instructions and cemented with an autopolymerizing luting composite. Each group was divided into nonaged and aged subgroups (n = 6 per material-height pair). Nonaged specimens were tested to fracture, while aged specimens first underwent cyclic loading (1.2 million cycles, 50 N, 1.7 Hz) followed by the same load-to-fracture test on surviving specimens. Fracture load data were analyzed with generalized linear model analysis and Bonferroni-corrected post hoc tests (α = 0.05). RESULTS: All aged specimens survived cyclic loading and were subjected to the load-to-fracture test. The interaction among material, prosthesis height, and aging condition affected the fracture loads (p < 0.001). Among the 11-mm nonaged specimens, BR led to the highest fracture load, whereas among the 15-mm nonaged specimens, TR resulted in the lowest values (p ≤ 0.001). For nonaged BR, 7-mm height led to the lowest values, whereas for nonaged SA, 15-mm height led to the highest values (p ≤ 0.007). In addition, 15-mm height led to higher values than 7-mm height for aged BR and SA (p ≤ 0.010). Aging reduced the fracture load of 11-mm BR (p = 0.002). CONCLUSIONS: Regardless of the aging condition, 7-mm (BR) or 11-mm (SA and TR) prosthesis heights may be considered as minimal requirements for tested materials to withstand the masticatory forces of the molar region in a cantilevered implant-supported situation. The effed of aging on measured fracture loads was minimal.