A three-dimensional photographic method for documentation and measurement of dental conditions.

A 3-D photographic technique was developed for the registration of bite conditions. This technique may replace plaster models for archiving purposes. To achieve this, photographic equipment and computer programs should be user friendly, not too expensive, and allow measurements that satisfy scientific demands. This purpose was fulfilled by combining the following elements: a photographic unit with standardized conditions for 3-D photography and a reference object with known coordinates where bite impressions or models are placed during photography. To reconstruct 3-D coordinates from photographs these are placed on a digitizer connected to a computer programmed for reconstructing 3-D coordinates from the digitized 2-D data. The accuracy of the 3-D reconstruction of coordinates, x, y, z, was tested by means of 3-D photographs of a test object with reference points having a precision of +/- 0.5 micron. The mean error for distances of 5 mm and 15 mm varied between -0.17 mm and +0.15 mm. Measurements of 45 degrees and 90 degrees angles had an accuracy that varied from -0.5 degree to +0.9 degree and from -1.2 degrees to +1.5 degrees respectively. An angle between lines and a plane of 54.7 degrees displayed a mean error of +/- 1.6 degrees. The test of the accuracy of the 3-D photographic technique for calculating distances and angles demonstrated that it fulfills demands for scientific applications on clinical material.