Three-dimensional radiographic assessment of the mandibular retromolar donor site in different vertical facial growth types

Abstract

Purpose: To assess volumetrically, the impact of vertical facial growth types (VGFT) on the retromolar area as a bone donor site MATERIAL AND METHODS: 60 cone beam computed tomography (CBCT) scans of adult individuals were classified in three groups according to their SN-GoGn angle: hypodivergent group (hG) (33.33%), normodivergent group (NG) (30%) and hyperdivergent group (HG) (36.67%). Total harvestable bone volume and surface (TBV and TBS respectively), total cortical and cancellous bone volume (TCBV and TcBV respectively) and the percentage of cortical and cancellous bone volume (CBV and cBV respectively) were evaluated.

Results: The whole sample showed a mean TBV of 1220.99±448.81mm³ and a mean TBS of 940.29±259.93mm². Statistically significant differences were found between the different outcome variables and the vertical growth patterns (p<0.001). TBS differs for the different vertical growth patterns with the highest mean of TBS observed in the hG group. TBV also significantly differs between the different vertical growth patterns (p<0.001) with the highest mean observed for the hG individuals. Significant differences in percentages of cBV and CBV were present between the hyper-divergent groups and the other groups (p<0.001) with the hyper-divergent group having the lowest percentage of CBV and the highest percentage of cBV.

Conclusion: hypodivergent individuals tend to have thicker bone blocks that can be used in onlay technique while thinner bone blocks harvested from hyperdivergent and normodivergent individuals can be used in three-dimensional grafting approach.

Keywords: Bone donor site; Bone grafting; Cone-beam computer tomography; Growth patterns; Ramus; Retromolar area.