Clinical oral investigations · 2025
Evaluation of stresses in the mandible caused by loading of all-on-four and trefoil concepts under different occlusion conditions using finite element analysis.
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Derinpınar Berna, Tsakir Emin Esra, Özarslan Merve, Özalp Öznur, Sindel Alper, Özarslan Mehmet Mustafa, Altay Mehmet Ali, Türker Nurullah
Аннотация
OBJECTIVES: This study aimed to evaluate the maximum stresses on the bone, implant, and screw under four loading conditions in two implant-supported prosthesis concepts: Trefoil and All-on-Four.
MATERIALS AND METHODS: Three-dimensional mandibular models were created based on the All-on-Four and Trefoil concepts. Maximum bite forces were applied under four conditions: maximum intercuspal position, canine-protected occlusion, group-function occlusion, and cantilever loading. The stresses on cortical bone, implants, and screws were calculated using finite element analysis.
RESULTS: The highest stresses under maximum bite forces occurred at the distal implants in the Trefoil model (393,9 MPa). The anterior implant (219,9 MPa), screw (171,1 MPa), and bone (29,7 MPa) in the Trefoil system experienced four times more stress than in the All-on-Four system (anterior implant 48,5 MPa, screw 50 MPa, bone 8,3 MPa). Canine-protected occlusion led to higher stresses on the working side. Stress concentrations were similar at the implant (trefoil right implant 23,7 MPa; middle 38 MPa; left 82,5 MPa; all on four right posterior implant 22,3 MPa; right anterior 12,7 MPa; left anterior 39,8 MPa; left posterior 86,8 MPa) and bone levels (trefoil right cortical bone 9,6 MPa; middle 2,07 MPa; left 11,1 MPa; all on four right posterior 7,5 MPa; right anterior 2,27 MPa; left anterior 1,8 MPa; left posterior 11,9 MPa) in both models, but higher stress was found around the screw of the central implant in the Trefoil system (53,8 MPa). Group-function occlusion resulted in higher stress at the implant (right 112,3 MPa; middle 124,6 MPa; left 776,2 MPa), screw (right 129,1 MPa; middle 239,9 MPa; left 474,3 MPa) and bone levels (right 66,1 MPa; middle 9,3 MPa; left 71,32 MPa) in the Trefoil model, with increased stress on the working side. Cantilever loading caused significant stress on abutment screws in the Trefoil model (right 42,2 MPa; middle 198,1 MPa; left 340,3 MPa), while the All-on-Four model (408,4 MPa) showed higher stress around the distal implants.
CONCLUSIONS: Canine-protected occlusion is recommended to minimize stress in both systems. Further clinical trials are needed to determine the optimal occlusion for implant prostheses.
MATERIALS AND METHODS: Three-dimensional mandibular models were created based on the All-on-Four and Trefoil concepts. Maximum bite forces were applied under four conditions: maximum intercuspal position, canine-protected occlusion, group-function occlusion, and cantilever loading. The stresses on cortical bone, implants, and screws were calculated using finite element analysis.
RESULTS: The highest stresses under maximum bite forces occurred at the distal implants in the Trefoil model (393,9 MPa). The anterior implant (219,9 MPa), screw (171,1 MPa), and bone (29,7 MPa) in the Trefoil system experienced four times more stress than in the All-on-Four system (anterior implant 48,5 MPa, screw 50 MPa, bone 8,3 MPa). Canine-protected occlusion led to higher stresses on the working side. Stress concentrations were similar at the implant (trefoil right implant 23,7 MPa; middle 38 MPa; left 82,5 MPa; all on four right posterior implant 22,3 MPa; right anterior 12,7 MPa; left anterior 39,8 MPa; left posterior 86,8 MPa) and bone levels (trefoil right cortical bone 9,6 MPa; middle 2,07 MPa; left 11,1 MPa; all on four right posterior 7,5 MPa; right anterior 2,27 MPa; left anterior 1,8 MPa; left posterior 11,9 MPa) in both models, but higher stress was found around the screw of the central implant in the Trefoil system (53,8 MPa). Group-function occlusion resulted in higher stress at the implant (right 112,3 MPa; middle 124,6 MPa; left 776,2 MPa), screw (right 129,1 MPa; middle 239,9 MPa; left 474,3 MPa) and bone levels (right 66,1 MPa; middle 9,3 MPa; left 71,32 MPa) in the Trefoil model, with increased stress on the working side. Cantilever loading caused significant stress on abutment screws in the Trefoil model (right 42,2 MPa; middle 198,1 MPa; left 340,3 MPa), while the All-on-Four model (408,4 MPa) showed higher stress around the distal implants.
CONCLUSIONS: Canine-protected occlusion is recommended to minimize stress in both systems. Further clinical trials are needed to determine the optimal occlusion for implant prostheses.