CBCT subtraction analysis of 3D changes following alveolar ridge preservation: a case series of 10 patients with 6-months follow-up

Aim: The purpose of this article is to present a novel method for the CBCT subtraction analysis of 3D changes following alveolar ridge preservation (ARP) with the application of a semi-automatic segmentation workflow and spatial registration. The study hypothesis was that by utilizing our novel approach, better 3D visualization and improved volumetric and linear evaluations of alveolar reconstructive procedures could be achieved following ARP compared with existing methodologies.
Materials and methods: Ten surgical sites of 10 partially edentulous patients were treated with a tunneled guided bone regeneration approach for ARP. Spatial registration and a semi-automatic segmentation method were utilized to create 3D digital models of pre- and postoperative CBCT datasets for subtraction analysis. The primary outcome variable of the study was the volumetric difference between pre- and postoperative CBCT scans. Secondary outcome variables were horizontal and vertical linear measurements at the mesial, distal, and middle aspects of the alveolus.
Results: Change of hard tissue volume averaged at 0.34 ± 0.99 cm3. The mean change of vertical hard tissue dimension was 5.97 ± 3.18 mm at the mesial, 6.40 ± 3.03 mm at the distal, and 7.01 ± 3.02 mm at the middle aspect of the extraction sites. Horizontal linear changes averaged at 6.19 ± 0.68 mm at the mesial, 6.32 ± 1.52 mm at the distal, and 6.90 ± 1.48 mm at the middle aspects of the extraction sites.
Conclusion: The digital reconstruction of CBCT datasets with the presented approach may provide a better understanding of the healing mechanisms following ARP. Not only the direct effect on extraction socket healing, but also the indirect positive effect on adjacent teeth can be visualized.