Investigating the optimal design of all-on-four technique adopting finite element analysis: the aspect of framework material, kind and position of implants
“…Finally, in the case of edentulism, i.e., when the patient misses all teeth, a recent technique involves the use of an arch, most of the times in resin or CrCo alloys, 39 and just four implants ( Figure 5 ) positioned two vertically in the incisive and two obliquely (18–45° respect to the vertical axis) molar regions, in accordance with the Paulo Malo concept. 40 Figure 5 Four-implants supported by an arch in a human mandible.…”
“…Finally, in the case of edentulism, i.e., when the patient misses all teeth, a recent technique involves the use of an arch, most of the times in resin or CrCo alloys, 39 and just four implants ( Figure 5 ) positioned two vertically in the incisive and two obliquely (18–45° respect to the vertical axis) molar regions, in accordance with the Paulo Malo concept. 40 Figure 5 Four-implants supported by an arch in a human mandible.…”
Background
Few studies have provided a detailed analysis of stress distribution on the components of multi-unit abutment (MUA). Our objective was to investigate the differences in stress patterns among MUA with different angulations under varies loading conditions.
Methods
Using finite element analysis, 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 prosthesis, accompanied by varying horizontal forces (0 N, 30 N, and 100 N).
Results
When subjected to a 200 N vertical load along the long axis of the prosthesis, 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 horizontal force (2389 MPa) compared to that without horizontal force. Most of the stress was located near the first thread of the prosthesis screw, while screws loaded with horizontal force showed a higher stress around the screw head.
Conclusions
Increasing the abutment angulation leads to higher stress on the implant, which may be associated with potential bone loss. Horizontal forces significantly increase the maximum stress on the implant, particularly in the neck region. There is a distinct stress distribution pattern between the prosthesis screw and abutment screw.
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