The Validity of in Vivo Tooth Volume Determinations from Cone-Beam CT

  • Dr Yi Liu, Peking University School and Hospital of Stomatology, Chinese Orthodontic Society
  • Dr Raphael Olszewski, Department of Oral and maxillofacial surgery Cliniques Universitaires Saint Luc, Belgium
  • Dr Emanuel Alexandroni, School of Dentistry, University of Southern California, United States
  • Dr Reyes Enciso, School of Dentistry, University of Southern California, United States
  • Prof Tianmin Xu, Peking University School and Hospital of Stomatology, Chinese Orthodontic Society
  • Dr James Mah, School of Dentistry, University of Southern California, United States

Objective: To determine the accuracy of volumetric analysis of teeth in vivo using cone beam computed tomography (CBCT).
Materials and Methods: The physical volume (Vw) of 24 bicuspids extracted for orthodontic purposes (16 were imaged with the I-CAT and 8 with the CB MercuRay) were determined using water displacement technique. Corresponding pre-treatment CBCT image data were uploaded into Amira 4.0 for segmentation and radiographic volume (Va). All measurements were performed twice by two observers. The statistical difference between Vw and Va was assessed using a paired t-test. The intra- and inter-observer reliability was determined by calculating Pearson correlation coefficients and intraclass correlation coefficients (ICC).
Results: The overall mean Vw of teeth specimens was 0.553±0.082 cm3, while the overall mean Va was 0.548±0.079cm3 (0.529±0.078 cm3 for Observer 1, and 0.567±0.085 cm3 for Observer 2). There were statistically significant differences between Va and Vw (P<.05). Between Observer 1 and Observer 2, Va measurements were statistically significantly different (P<.05). The inter- and intra-observers correlation coefficient for Vw was high. Lastly, surface smoothing reduced the volume by 3 to 12%.
Conclusion: In vivo determination of tooth volumes from CBCT data is feasible. The measurements slightly deviate from the physical volumes within -4 to 7% percent. Smoothing operations reduce volume measurements. Currently no requirements for accuracy of volumetric determinations of tooth volume have been established.