Bestimmung der Zahnangulation im Dental-CT bei nicht konstanten Untersuchungsparametern

Aim: In order to achieve anatomically correct measurements of the tooth axes in Dental CT, a standard evaluation framework is necessary because there is no possibility to fix the patient's head in CT. Material: A macerated skull and 23 patients with full dentitions. Methods: A macerated skull with a titan plate in the occlusal plane was scanned in four different positions. In this presentation an example is given by the images of the skull tilt 7° to the left. In the first step the angulations of the teeth were measured to the horizontal edge of the panoramic and paraxial CT reformations (original measurements). These values were entered into a self developed angulation correction program based on a defined reference compared with the original measurements and with the values which were obtained by plane (occlusal plane). The corrected values were then measuring the angle between the tooth axes and the titan plate (control measurements). The results were analysed statistically. In addition, the Dental CT images of 23 patients partly with misplaced teeth were analysed analogously. Results: For the macerated skull the difference between the corrected values and the control measurements was up to 1°. However the difference between the original measurements and the corrected values was up to 7°. In the panoramic images the greatest deviation could be seen in the anterior area and in the paraxial images in the posterior area of the dental arch. For the patients about 67% of the tooth axes could be measured easily whereas the determination of the tooth axes was insufficient in 33% of the measured teeth. Conclusion: Overall, the Dental CT is most suitable to find the topographical location of misplaced and impacted teeth. The angulation correction program, especially developed for this application, guarantees an exact metric analysis of tooth angulation independent of the patient's position in the CT. Dental CT and the angulation correction program form an optimal diagnostic instrument for presurgical planning and for orthodontic procedures, especially in cases having misplaced teeth. Parole chiave: dental, CT, tooth angulation, dental-CT, computer correction program