Method: Dicom data of CBCT images were visualized on Simplant Pro 13.0 software. Head positions were reoriented to be standardized in different time intervals and panoramic curve was drawn to derive ideal panoramic view. "Draw nerve" tool was chosen, plottings were performed on ideal panoramic view, corrected on every axial and sagittal slice and 3D nerve object was obtained. The real MC length was measured as the sum of the distances smaller than 5mm tangent to the 3D nerve object. The least MC length by ruling out the curve of the MC, was measured as the distance between the mandibular foramen and the mental foramen.
MC location was determined by choosing the slices perpendicular to the panoramic curve; from mandibular foramen level, distal to the second molar and first molar as crossectional slices, from mandibular foramen level as an axial slice. The distance measurements were mandibular bone length and width, superior, inferior, medial and lateral lengths, medial and lateral medullar bone thicknesses, MC length and width on these slices. By the help of these measurements proportional and millimetric location of MC was obtained.
In order to determine the reliability of the method, 3D image generation and measurement procedure was repeated on CTs obtained from 13 randomly selected orthognathic surgery patients. Intraclass correlation coefficients(ICC) were calculated at a significance level of p<0,05.
Result: ICC for all measurements was nearly 1,00 indicating that the measurements were reproducible with nonsignificant method error.
Conclusion: Preoperative 3D imaging and evaluation of MC location may aid in prevention of complications during surgery. Postoperative evaluation helps reveal the changes in MC. This method is a practical, reproducible technique to determine MC location and mandibular canal length.