Comparison of Two Methods of Predicting Maxillofacial Volumetric Bony Defects: CBCT Used As A Valuable Preoperative Tool
Purpose:
Pre-prosthetic surgery is routinely conducted in patients with bony defects or deficiencies to help ensure functional and favorable outcomes after the restorative phase of treatment is completed. CBCT is an emerging technology that aids in the planning of implant surgery. The Cavalieri Principle and 3D reconstruction are two techniques that can be used to quantitatively estimate the volume of bony defects using CBCT technology. Studies have independently utilized both modalities to approximate volumes; however, no study has compared these two methods to determine if one is most accurate. The objective of this study was to compare the accuracy of each method in quantitatively predicting the volume of a bony defect.
Methods:
Defects of the same approximate size were created on nine plastic mandibular models. The actual volume of the defect on each mandible was measured clinically and served as the control. Each mandible was then scanned using a CBCT, and volumetric measurements were made for each defect using two techniques: the Cavalieri principle and 3D reconstruction. The Cavalieri principle is a mathematical principle that states that the volume of an object or defect can be measured by adding the surface area of each slice of the object of interest on a CBCT cross sectional view, and multiplying by the thickness of each slice. 3D reconstruction relied upon the data reconstruction tool in the Anatomage Software to reconstruct a volume defect. For each defect, the volume obtained by each technique was compared to the control volume using Student’s T-test with significance at p<0.05. Additionally, raters independently measured the volume of bony defects in CBCT images obtained for pre-prosthetic surgery for twelve patients using the 3D reconstruction method, and the measured volumes between the raters were compared to determine inter-rater reliability.
Results:
The Cavalieri Principle consistently underestimated the actual volume of defect by 21% (p<0.05). Hence, the Cavalieri Principle was not seen as an accurate method to estimate the volume of a bony defect. Conversely, 3D reconstruction only underestimated the actual volume by only 8 %, which was not seen to be a significant difference (p>0.05). There was no statistical difference between the inter-rater reliability for measuring the volume of bony defects in the 3D reconstruction method for actual patients.
Conclusion:
These results demonstrate that the 3D reconstruction method is both an accurate and reliable method of approximating volume on CBCT; a statement which cannot be made in regards to the Cavalieri Principle. It is hoped that based on this research clinicians will be able to utilize CBCT imaging to more accurately predict the volume of bony defects in the maxillofacial area, which will aid in more predictable planning of implant surgery.
References:
1.Shiratori LN, Marotti J, Yamanouchi J, Chilvarquer I, Contin I, Tortamano-Neto P. Measurement of buccal bone volume of dental implants by means of cone-beam computed tomography. Clin Oral Implants Res doi:10.1111/j.1600-0501.2011.02207.x.
2.Spin-Neto R, Stavropoulos A, Pereira LA, Marcantonio E Jr, Wenzel A. Fate of autologous and fresh-frozen allogenic block bone grafts used for ridge augmentation. A CBCT-based analysis. Clin Oral Implants Res. doi:10.1111/j.1600-0501.2011.02324.x.