Digital workflow in implant-supported prostheses: deformation analysis of milled frameworks

Abstract

The use of digital technology is increasing rapidly in modern dentistry. However, there is still not enough data in the literature regarding the manufacture of milled frameworks on implant-supported prosthesis. Purpose: To assess the stress caused on dental implants by milled frameworks of different sizes made through digital workflow and to compare two types of scanners. Methods: An edentulous model of a maxilla was created through 3D printing, where six equidistant implants were installed with a 50Ncm torque. Over each implant was installed a 5.5mm mini conical abutment with a 32Ncm torque. Over these abutments, two types of scanning were performed: intraoral scanners (IOS) and laboratory scanners (LS), from which each framework was designed and milled from titanium discs. These frameworks were made over two, four and six implants, simulating different clinical situations. To analyze the deformation, two strain gages were attached to the abutment surfaces, on the buccal and mesial surfaces. Results were analyzed using a paired Student’s t-test, with significance level of 0.005. The passivity was evaluated by an experienced operator. Results: LS scanners had the lowest deformation, when compared to the IOS. The greater the distance between the implants, the higher the deformation. In frameworks on 4 implants, the deformation was greater, as it was the distance between the implants. The groups on 2 implants showed the least strain (p < 0.005). All frameworks were considered passive, as they all fit the passivity criteria. Conclusions: All scanning techniques reported are reliable. The milled frameworks are passive and accurate, with very little deformation, and they can be safely supported by implants, without bone resorption.