Objectives: FEA conducted to determine stress within supporting bone when angle of force, implant offset and height of implant supported prosthesis was changed Materials and Methods: A three dimensional finite element analysis model of the mandible was created using PATRAN software. Three titanium endosseous implants were placed within the model at a distance of 7 mm center to center. Prostheses were made to simulate two heights of 6 and 12 mm. The center implant was placed on the line from the centers of the terminal implants (0 offset), 1.5 mm lateral to this line (1.5 offset) or 3.0 mm lateral to this line (3.0 offset). 200 N forces were applied in a straight vertical direction or in 15o increments to the vertical (15, 30, 45 and 60 degrees). Stress in supporting bone was evaluated. Data was analyzed using ABAQUS finite element software. Results: The lowest stress in the supporting bone was found with vertical loading, no offset and 6 mm prosthesis (3.12 MPa). Stress increased with the 12 mm prosthesis height (3.86 MPa). Changing the angle of force application by 15o resulted in increased stress to the underlying bone (10.46 and 16.91 MPa for 6 and 12 mm prostheses). Creation of an offset did not compensate for this increased stress (5.93 Mpa 6 mm and 9.24 Mpa 12 mm height, both with 3 mm offset). Conclusions: Vertical loading of an implant prosthesis produces the lowest stress to the supporting bone. A 15o change in angle of force application from vertical causes an increase in stress. Increasing the angle further results in greater stress to supporting bone. Reduction in prosthesis height from 12 to 6 mm or establishment of an offset implant location will reduce stress but this reduction does not compensate for the increase found with the off axis loading.

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