A finite element study of short dental implants in the posterior maxilla.

PURPOSE: Elevated bite forces and reduced bone densities and dimensions associated with posterior regions of the maxilla cause relatively high failure rates when short dental implants are placed to substitute missing teeth. This study uses the finite element method to evaluate four distinctly different short implant designs (Bicon, Neodent, Nobel Biocare, and Straumann) for their influences on the von Mises stress characteristics within the posterior maxilla. MATERIALS AND METHODS: Finite element models of the supporting bone and tooth crowns are developed based on computed tomography data, and implant geometries are obtained from manufacturers' catalogs. The finite element models are meshed using three-dimensional hexahedral and wedge-shaped brick elements. Assumptions made in the analyses are: linear elastic material properties for bone, 50% osseointegration between bone and implant, and crown height-implant length ratio of 2:1. RESULTS: Bicon's neck indentation produced reduced stress in the cortical bone when compared with the Nobel Biocare and Straumann systems. The increased taper of the Neodent design decreased the stress level in cancellous bone. Nobel Biocare's rounded thread crest and reduced thread pitch produced a smoother stress profile. Straumann's increased thread pitch produced elevated stress in the cancellous bone. Generally, stresses were concentrated in the crestal bone region around the implant neck, attributable to the inclined nature of the masticatory force. CONCLUSION: Nobel Biocare and Bicon systems are recommended for use in type 4 cancellous and cortical bone, respectively.

Step-wise analysis of the dental implant insertion process using the finite element technique.

OBJECTIVES: Using the finite element method (FEM), the insertion process of a dental implant into a section of the human mandible is analysed. The ultimate aim of this article is to advance the use of an innovative engineering approach in dental practices, especially in the process of dental implantation. MATERIAL AND METHODS: The FEM and analysis techniques are used to replicate and evaluate the stress profile created within the mandible during the implantation process. RESULTS: The von Mises stress profiles in both cancellous and cortical bone are examined during implant insertion. The applied torque and the insertion stage are found to strongly influence the resulting stress profile within the surrounding jawbone. CONCLUSIONS: Through the combination of both dental and engineering expertise, a simplified and efficient modelling technique is developed. This improves the understanding of the biomechanical reaction that the jawbone exhibits due to the insertion of implant. The current research is a pilot study using the FEM to model and simulate the dental implantation process. The assumptions made in the modelling and simulation process are: (1) the implantation process is simulated as a step-wise process instead of a continuous process; (2) the implant is parallel threaded and the implant does not rotate during insertion into the jawbone. Although the modelling and simulation techniques had to be simplified, a significant amount of information is gained that helps lay a good foundation for future research. Recommendations for future studies include the variation of the torque applied during the implantation process and upgrading the software capabilities to simulate the full dynamical process of implantation.