Fracture Strength of Resin-Bonded Dental Prostheses with a Rigid Versus Nonrigid Joint. An In Vitro Study

This in vitro study investigated whether a resin-bonded dental prosthesis (RBDP) with a hyperstatic, rigid joint was preferable to an isostatic, nonrigid construction in terms of debonding and fracture strength. RBDPs replacing a missing molar with a rigid (design I) or a resilient model (design II) were compared to a commercially available system (Crownless Bridge Work) (design III, control). All groups were subjected to thermocycling (TC) and dynamic mechanical loading (ML) in a dual-axis chewing simulator (TC: 6,000 x 5°C/55°C; ML: 1,200,000 x 49 N x 1.4 Hz). None of the RBDPs of design III showed movement or fracture during the test period. Significant differences between designs I and III (P = .0049) and between designs II and III (P = .0007) were noted. Despite a tendency for lower fracture values of design I, no significant differences could be established between the test designs with a rigid or nonrigid construction. The commercially available dental prosthesis with a nonrigid joint was confirmed to resist a 5-year survival simulation.