Master thesis and internship[BR]- Master's thesis : Geometric Adjustment of Complete Dental Prostheses[BR]- Internship

Abstract

This thesis provides an analysis on the impact of misfit in implant-supported fixed dental prosthesis, specifically focusing on the challenges and advancements in managing edentulous patients through these prosthetic solutions. The context highlights the historical issues with traditional removable dentures, which often fail to provide satisfactory outcomes due to discomfort, poor retention, instability, and difficulty in mastication. Implant-supported prostheses have emerged over the past two decades as a reliable solution, offering numerous advantages such as decreased bone resorption, enhanced aesthetics, improved tooth position, and increased occlusion function. The study emphasizes the criticality of achieving a passive fit between the prosthesis and the implant components to prevent mechanical complications such as screw loosening, framework fractures, and bone damage. Various impression techniques, including plaster impressions, intraoral cameras, and photogrammetry, are evaluated for their accuracy and suitability. Finite Element Analysis (FEA) is employed to predict the biomechanical behaviour of dental implants under different conditions. This thesis details the process of creating geometric models from 3D scans of prostheses, including post-treatment of the scans and construction of computer-aided models. Mesh accuracy is assessed to ensure reliable simulation results, with discussions on the types of elements used and the convergence of the mesh. The analysis includes different configurations of prostheses (All-on-8, All-on-6 and All-on-4) and materials (titanium and zirconia). The study identifies the most detrimental directions of misfit and their effects on the stress distribution within the prostheses. It is found that the tangent direction is generally the most detrimental, followed by the normal and binormal directions. Stress concentrations are primarily located in the region between access holes. Recommendations are made to minimize errors and improve the fit and performance of implant- supported prostheses. This includes optimizing the design and placement of the implants, utilizing advanced impression techniques, and ensuring proper tightening of screws. This thesis concludes with a discussion on the importance of balancing the stiffness of the prosthesis with that of the bone and the implants to prevent adverse effects on bone health and the overall outcomes of the restoration.