Ehsan Ghasemi, Amirhossein Fathi, Sharare Jahangiri, Saeid Farahmand
Abstract
Background and Objective: This study used a finite element analysis to evaluate the effect of different angles and positions of implants in the All-on-four maxillary design on stress distribution in the cortical and trabecular bone and the various components of the prosthetic Model including the superstructure, implants, abutments and abutment screws.
Materials and Methods: A model of edentulous maxilla and six models based on implants were made in this finite element analysis study to reconstruct complete edentulism using a fixed prosthesis method. Model 1: Four implants including two vertical anterior implants in the lateral teeth position and two posterior implants with a 30-degree angle in the position of the second premolars. Model 2: Four implants including two anterior implants with a mesial angle of 15 degrees in the lateral teeth position and two posterior implants with a 30-degree angle in the position of the second premolars. Model 3: Four implants including two anterior implants with a 15-degree distal angle in the lateral teeth position and two posterior implants with a 30-degree angle in the position of the second premolars. Model 4: Four implants including two vertical anterior implants in the lateral teeth position and two posterior implants with a 45-degree angle in the position of the second premolars. Model 5: Four implants including two vertical anterior implants in the central teeth position and two posterior implants with a 30-degreee angle in the position of the first premolars. Model 6: Four implants including two vertical anterior implants in the canine teeth position and two posterior implants with a 30 degrees angle in the position of the first molars. The loading conditions were as follows: 100 N of axial (vertical) force was applied to the end of the superstructure on the left side of the maxilla.
Results: Under the applied force, the maximum stress in bone and prosthetic structures was related to Models 4 and 5. Changing the anterior implant angle from the vertical position and increasing the tilt of posterior implants in the All-on-four design increased the stress level while placing the implants in more distal positions reduced the stress level.
Conclusion: Using vertical anterior implants in the All-on-four design is more appropriate than angled implants. Additionally, the 30-degree angle of the posterior implants displays more appropriate biomechanical behavior than the 45-degree angle. The stress in the bone and related prosthetic structures is reduced due to the reduction in the posterior cantilever length by placing the implants more distally.
DOI : 10.62610/RJOR.2025.1.17.7
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