Photogrammetric measurements of implant positions. Description of a technique to determine the fit between implants and superstructures.

A photogrammetric technique was designed to measure the position of dental implants in 3 dimensions to enable assessment of the fit of superstructures placed on the implants. A relatively simple camera set-up was developed and tested. Calibration of the camera was performed in a high-precision analytical plotter and revealed a film measurement accuracy of 0.005 mm. The achieved measuring accuracy for clear and well defined points on clinical components was found to be around 0.02 mm. To find the center points of the implants, points on the circumference were measured. These points are not well defined, which resulted in an estimation of the center point of the implant with a precision of 0.05 mm. Independent measurements of a prosthesis with 5 implants were also within the precision of 0.05 mm. The angular orientation of the top surface of the implant cylinder (abutment, brass replica of gold alloy cylinder of the framework) was measured with a precision of 0.01 radians, which corresponded to an error with a peripheral gap of about 0.03 mm. This value was about 5-10 times lower than the clinical fit between frameworks and abutments, measured in 3 randomly selected clinical cases.