Stress distribution on the components of multi-unit abutment with different angulation under lateral force: a finite element analysis.

Objectives: Few studies have provided a detailed analysis of stress distribution on the components of multi-unit abutment (MUA)-implants complex, particularly the abutment screw and prosthetic screw, which are among the most fragile parts of the restoration. Our objective was to investigate the differences of stress distribution on the components of MUA-implants complex under varies loading conditions using finite element analysis.

Materials and methods: We constructed MUA-implant complexes with different abutment angulations (0°, 17°, and 30°). A static force of 200 N was applied along the axis of the prosthetic abutment, accompanied by varying lateral forces (0 N, 30 N, and 100 N).

Results: When subjected to a 200 N axial load, implants with a 30° angulated abutment experienced nearly 2.5 times the stress (1185 MPa) compared to straight abutments (437 MPa). The maximum stress of the straight MUA-implant was 8 times higher under a 100 N lateral force (2389 MPa) compared to that without lateral force. Prosthetic screws suffered higher stress concentration than the abutment screw and stress was mostly located near the first thread of the prosthetic screw.

Conclusions: There is a distinct stress distribution pattern between the prosthetic screw and abutment screw, with the former experiencing higher stress concentration than the latter.

Clinical relevance: The present study indicates that prosthetic screws are more vulnerable to mechanical complications and cautions should be raised to balance biting force to minimize the risks of mechanical complications in patients with angulated MUA-implants complex.