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.

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