Computer-aided design evaluation of harvestable mandibular bone volume: a clinical and tomographic human study.

Purpose: To evaluate and compare the volume of bone graft material that can be safely harvested from the mandibular symphysis and rami using a computer-aided design (CAD) software program.

Materials And Methods: Preoperative computerized tomography scans from 40 patients undergoing bone augmentation procedures were analyzed. Symphysis and rami cross sections were mapped using a CAD software program (AutoCAD(®), Autodesk, Inc., San Rafael, CA, USA) to evaluate the bone volume that can be safely harvested. CAD calculations were contrasted to intrasurgical measurements in a subgroup of 20 individuals.

Results: CAD calculations yielded a safe harvestable osseous volume of 1.44 cm(3) ± 0.49 for the symphysis and 0.82 cm(3) ± 0.21 for each ramus (p < .0001, confidence interval [CI] 95%: 0.47-0.78). These measurements were significantly lower (p < .0001) than the bone volumes harvested intrasurgically for both symphysis and ramus, respectively (2.40 cm(3) ± 0.50 vs. 2.65 cm(3) ± 0.45). CAD calculations of harvestable symphysis and ramus bone translated into an average of 2.40 cm(3) ± 0.50 (range: 1.80-3.10 cm(3)) and 2.65 cm(3) ± 0.45 (range: 1.90-3.50) of particulate bone graft intrasurgically, respectively. Ramus cortical was significantly thicker than the symphysis cortical, 2.9 ± 0.4 mm versus 2.19 mm ± 0.4 mm (p < .0001, CI 95%: 0.45-1.03).

Conclusion: The symphysis and rami are good harvesting sources to obtain dense corticocancellous bone. The significant volumetric CAD differences between the symphysis and ramus seem to balance out intrasurgically and may be due to the greater cortical bone volume at the ramus area. It is plausible to harvest an average of 7.70 cm(3) from the symphysis and rami alone. The use of a CAD software program can enhance surgical treatment planning prior to bone transplantation.