Stress-strain state of implant-supported restorations in tooth replacement

Background: Dental implant therapy may be associated with breakage and deformation of implant-supported restorations, necessitating an assessment of their stress-strain state when applying a load. Aim: To compare the stress-strain state of implants with their respective fixed restorations in tooth replacement. Materials and Methods: A 3D mathematical model of the posterior mandible with three missing teeth was used to assess the stress-strain state for the following dental restoration options: three implant-supported crowns; a two-implant-supported bridge; or a bridge supported by tooth and implant. A 150 N load was applied to the central part of a restoration in both vertical and oblique directions to compare maximum stress values and their distribution. Results: Oblique load was found to have a negative impact on stress intensity and distribution (471.7 MPa vs 90.7 MPa with vertical load for three implants). The most heavily loaded parts of restorations were identified: the border of the crown and the implant connection zone. A homogeneous stress distribution from a bridge to the two supporting implants was observed, along with a decrease in stress when using a bridge rather than three implant-supported crowns (160.0 MPa vs 16.1 MPa). In contrast, the load on the supporting implant increased when a bridge supported by tooth and implant was used (1,053.5 MPa with oblique load). Conclusion: Compared to three implants replacing three missing teeth, a two-implant-supported bridge decreases stress on the implants and their respective restoration. Replacing one supporting implant with a tooth increases stress on the implant to the ultimate strength of titanium alloy in the abutment.