Comparison of stress distribution in upper jaw "all on 4" and "all on 6" concept implant-supported prostheses produced with different materials by finite element stress analysis method

Comparison of Stress Distribution in Upper Jaw "All On 4" and "All On 6" Concept Implant-Supported Prostheses Produced with Different Materials by Finite Element Stress Analysis Method Aim: The aim of this study is to analyse the stresses on the implant, peri-implant bone and prosthetic substructure of implant-supported prostheses prepared with different implant concepts and different substructure materials by using the finite element stress analysis (FESA) method. Materials and Methods: Two different implant concepts and prosthetic superstructures with the same structure were designed based on the image obtained from the maxillary tomography. According to this, for 'All on 4' (Model 1), the implants (3.5 mm thickness and 10 mm length) in the anterior region were positioned symmetrically and axially (without angle) to the lateral tooth region, and two implants (10 mm length and 4.1 mm thickness) were positioned symmetrically and at a 30° angle to the 1st molar regions in the posterior region and for 'All on 6' (Model 2), the first implant was positioned in the anterior region between the central and lateral teeth and the second implants (3.5 mm thickness and 10 mm length) were positioned axially (without angle) in the canine tooth region. The implant in the posterior region was positioned with the same characteristics and shape as Model 1. Eight different study models were obtained by designing fixed prostheses consisting of Chrome-Cobalt, Zirconia, Titanium and Polyetheretherketone (PEEK) substructure materials on two different models. The force was applied on the prostheses in the anterior region vertically at 100 Newton (N) and unidirectionally. In the posterior region, the stress values of the bone, implant and substructure material were obtained by FEA method by applying forces of 150 N in the palatino-buccal direction at an angle of 30 degrees to the buccal tubercles of teeth 3-4-5, and 200 N in the palatino-buccal direction at an angle of 30 degrees to the buccal tubercules of teeth 6-7. Results: According to the FESA results it was observed that the stress intensity on Model 1 was higher than Model 2, regardless of the substructure material. In both models, it was observed that the stress intensity of PEEK substructure material on bone and implants was higher than other substructure materials (Cr-Co, Ti, Zirconium). Conclusion: The increase in the number of implants in implant-supported fixed prostheses reduces the amount of stress that will occur in the bone, substructure and implant. It was observed that the use of Cr-Co, Zr and Ti materials with a higher modulus of elasticity was more suitable than the use of PEEK material with a lower modulus of elasticity, especially in the 'All on 4' and 'All on 6' designs which were designed in over-resorbed maxilla. Keywords: Finite element stress analysis, Implant-supported prosthesis, PEEK, Titanium, Zirconium