Comparison of Strains Produced in a Bone Simulant Between Conventional Cast and Resin-Luted Implant Frameworks

Complete-arch implant prostheses continue to exhibit horizontal and vertical misfit between frameworks and abutments. It has been suggested that these gaps may be eliminated and that restoration-induced stresses may be reduced by luting frameworks to screw-retained abutments intraorally. This study measured and compared the strains generated by clinically acceptable, conventional frameworks and abutment-luted frameworks to a bone simulant model. Three conventional and three resin-luted frameworks were made from a single master cast representing a bone simulant model of an edentulous mandible with five Nobel Biocare implants and 4-mm abutments. Two strain gauges were also embedded in the bone si mulant model to measure strains at two locations. Resin-luted frameworks were made by securing abutments to the clinical model with five gold slot screws tightened to 10 Ncm. Frameworks were then luted to these abutments with TwinLook cement following manufacturer's specifications. Both groups of frameworks were sequentially secured to the cli nical model with screws tightened to 10 Ncm. Strain-indicator readings were recorded at a standardized time following the initial fastening of each prosthesis (n = 3). Mean principal strains were determined and compared using a one-way repeated measures analysis of variance. A statistically significant difference was found in the principal strains between the conventional cast and the resin-luted frameworks. Overall, there was a decrease in the magnitude of strain for the resin-luted frameworks. Intraoral luting of frameworks may decrease the strains produced in the bone around implants.