Finite element analysis of load distribution among dental implants

A 3D finite element (FE) model was developed to calculate the vertical forces on dental implants supporting prosthetic bridgework. Results of PE models were compared to results of an analytical model developed by Skalak (1), and to experimental results from laboratory models of semicircular metal and acrylic bridges supported by screw-shaped titanium dental implants specially-designed to sense axial load. The dental implants in these lab models were inserted into (a) an aluminum baseplate (Ng's experiment (2) or (b) a dried human mandible (Edwards' experiment (3)) in order to vary the stiffness of the 'bone'-implant interface. FE models were constructed with beam elements for the implants and brick elements for the bridge. To simulate the effects of different stiffnesses at the bone-implant interface, some FE models used foundation elements of prescribed stiffness beneath the implant beam elements. Models were run with purely vertical forces applied at various locations along the bridge, e.g., at distal locations, midline locations and at an intermediate point. Two key results were: (a) For implants in a stiff interface, supporting either metal or acrylic bridges, the FE results were in closer agreement with experimental data than the Skalak analytical model. (b) For implants in a less stiff interface, the FE model and Skalak model predicted the implant loads accurately for the case of the metal bridge but only the FE model was accurate in the case of the acrylic bridge. For future work it will be important to obtain better data on actual interfacial stiffnesses as input data for FE models.