Strain Development of Implant-Supported Fixed Prostheses Copy Milled from Zirconia Ceramic

The aim of this research was to quantify the strain development of three-unit implant-supported fixed partial dentures (ISFPDs) copy milled from zirconia ceramic. Three ISFPD groups (n = 10) were fabricated by means of casting, copy milling, and computer-aided design/computer-assisted manufacturing (CAD/CAM) to fit an in vitro model with two implants. During cementation of the restorations, the emerging strains were recorded using strain gauges attached to the cast material mesially and distally adjacent to the implants. Absolute mean strain development ranged from 85.39 µm/m to 326.83 µm/m at the different strain gauge locations. Fabrication method had a significant effect on strain development (multivariate analysis of variance, P = .011), with the cast restorations showing the highest strain development and the CAD/CAM-fabricated ISFPDs showing the lowest. Copy milling leads to ISFPs that are more precise than cast restorations but less precise than CAD/CAM-fabricated restorations.