Effect of Anterior Implant Position on Biomechanical Performance in the Maxillary All-on-Four Treatment: A 3-D Finite Element Analysis
In the all-on-four concept, the positions of both posterior and anterior implants can affect stress distribution. The aim of this study was to examine the effect of the position of anterior implants on stress distribution in the implant, the bone around the implant, and prosthetic components in the resorbed maxilla using the all-on-four concept. All-on-four designs were prepared with 3 different anterior implant positions in a fully edentulous maxilla. Anterior implants were placed axially in the central incisor area in model 1, in the lateral incisors area in model 2, and in the canine area in model 3, forming 3 groups. The von Mises and principal stresses in the bone tissue and the von Mises stresses in the implant and prosthetic components were evaluated by 3-dimensional finite element analysis. There were more stresses on the cortical bone than trabecular bone. The stresses on the bone tissue and implant components were generally concentrated around the posterior implant, whereas the stresses on the prosthetic components were generally concentrated in the anterior region. Changing the anterior implant positions from the central tooth to the canine tooth reduced the stress on the bone around the implant. The highest von Mises stresses occurred in the prosthetic superstructure in all models, whereas the lowest stresses occurred in the trabecular bone. Changing the position of the anterior implants from the central tooth to the canine area in the maxillary all-on-four concept created a favorable stress distribution.
Models with 3 different anterior implants positions: (a) Model 1; (b) Model 2; (c) Model 3.
The bone and soft tissue modeling process: (a) cortical bone model; (b) trabecular bone model; (c) gingival soft tissue model; (d) completed maxilla model.
Modeling implant components: (a) titanium implant; (b) abutment; (c) screw.
Modeling of prosthetic elements and complete model of all structures: (a) framework; (b) crowns; (c) prosthetic appearance with implants in bone; (d) palatinal view of the prosthesis; (e) completed model of all structures.
Bite forces applied: the red arrows shows the direction of the force, the red areas in the occlusal of the teeth where the force were applied.
Stress values and stress distribution in the trabecular bone: (a) Von Mises stress distribution in Model 1; (b) Von Mises stress distribution in Model 2; (c) Von Mises stress distribution in Model 3; (d) Pmin stress distribution in Model 1; (e) Pmin stress distribution in Model 2; (f) Pmin stress distribution in Model 3; (g) Pmax stress distribution in Model 1; (h) Pmax stress distribution in Model 2; (i) Pmax stress distribution in Model 3.
Stress values and stress distribution in the cortical bone: (a) Von Mises stress distribution in Model 1; (b) Von Mises stress distribution in Model 2; (c) Von Mises stress distribution in Model 3; (d) Pmin stress distribution in Model 1; (e) Pmin stress distribution in Model 2; (f) Pmin stress distribution in Model 3; (g) Pmax stress distribution in Model 1; (h) Pmax stress distribution in Model 2; (i) Pmax stress distribution in Model 3.
The von Mises stress values and stress distributions on implants, abutments and abutment screws: (a) Von Mises stress distribution on implants, in Model 1; (b) Von Mises stress distribution on implants, in Model 2; (c) Von Mises stress distribution on implants, in Model 3; (d) Von Mises stress distribution on abutments, in Model 1; (e) Von Mises stress distribution on abutments, in Model 2; (f) Von Mises stress distribution on abutments, in Model 3; (g) Von Mises stress distribution on screws, in Model 1; (h) Von Mises stress distribution on screws, in Model 2; (i) Von Mises stress distribution on screws, in Model 3.
The von Mises stress values in the frameworks and crowns. (a) Von Mises stress distribution on frameworks, in Model 1; (b) Von Mises stress distribution on frameworks, in Model 2; (c) Von Mises stress distribution on frameworks, in Model 3; (d) Von Mises stress distribution on crowns, in Model 1; (e) Von Mises stress distribution on crowns, in Model 2; (f) Von Mises stress distribution on crowns, in Model 3.
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