Experimentally Informed FEM Model for Evaluation of Dental Implant Primary Stability

Sammanfattning

Expected growth in the dental implant market is driving a need to improve favorable patient outcomes. Approximately 5\% of patients experience dental implant failures, which can occur in the short or long term. Short-term failures, which occur before successful implant osseointegration, are due to surgical trauma to the alveolar bone, post-operative infections, or predisposing factors such as smoking; long-term failures, after successful osseointegration, are due to peri-implantitis, often as a result of poorly positioned implants or poor prosthesis design. To reduce the incidence of peri-implantitis, new implant designs should be explored. It is not easy to know the impact of the design changes for dental implants. Gathering experimental data is challenging, as there are many ethical concerns around testing on humans. Thus, research often turns to FEM models, which enable faster iterations and predictions before final experimental verification and validation testing. However, no FEM model properly captures the interaction between the dental implant and the surrounding bone, and many models are not validated. Hence, the main objective of this thesis was to develop an experimentally informed FEM model of the bone-implant interface that accounts for damage immediately after implantation and frictional interactions between the implant and the surrounding bone. To achieve this objective, successive tasks were completed: first, experimental testing consisting of \acrshort{uCT} imaging and mechanical testing was completed to gather real-world data; second, a FEM model was developed, focusing on the interactions at the bone-implant interface, which simulates primary stability of a dental implant; finally, the model was validated with the experimental data. A review of the \acrshort{uCT} images and mechanical testing data shows signs of damage within the trabecular microtructure. Additionally, the results fall within a plausible range based on the literature, and they are suitable for validating the simulation results. When comparing the experimental data with the FEM simulation predictions, there is reasonable agreement, considering the simplifications made during the model development. Furthermore, the FEM simulation provided insights that the experimental data cannot, including information on stress concentrations, locations of high strain, and micromotions at the bone-implant interface. It can be concluded that the main objective of developing an experimentally informed FEM model of the bone-implant interface has been fully achieved. This study contributes to the ongoing development of an FEM model that accurately reflects the G\&R that occurs at the bone-implant interface. Future research should utilize improved bone implant samples to produce more realistic experimental data, transition the FEM material data from a linear elastic to nonlinear models, and investigate whether the simplified damage prescription and frictional contacts in the model are sufficient to reflect real-world conditions. By improving the understanding of the mechanics at the bone-implant interface, better dental implants can be designed to reduce the incidence of patient failures.