Soft Tissue Analysis and Cast Measurement in Orthodontics Using Digital Photogrammetry

In orthodontics the lateral X-ray and its analysis is an important part of the diagnostic procedures since the discovery of X-ray and the introduction of cephalic measuring with almost parallel X-rays. Making lateral and frontal photographs of the patient represents another common diagnostic method in this particular medical subject area. But both methods only allow a two dimensional inspection of cephalic or facial structures. While making a lateral X-ray the patient is exposed to radiation. Furthermore, the bony structures of the cephalic skeleton are pictured as a summation, which increases the probability of misinterpretation of the measured values. With the three dimensional photogrammetric measurement of the facial skull using 5 standard views a new diagnostic resource is available to the orthodontist, which allows the non-tactile, radiation free acquisition of the measure points of the viscerocranium with an accuracy in the range of 0.1 mm. Particularly the spatial acquisition of soft tissue points is possible for the first time without considerable instrumental expenditure and radiation for the patient. Also digitizing of teeth and jaws from a plaster cast may be performed and the data transformed to the skull data using a special transformation bar which is photographed while the patient holds it with his teeth and also while attached to the plaster casts. Off the shelf digital cameras are used (Fuji DS-300 (1280x1000 pixels) and a Kodak DC260 (1536x1024 pixels)). The obtained results are very well in the range of the point definition accuracy of soft tissue points.