492 Factors Affecting Alveolar Bone Height Measurements from CBCT Images

Thursday, March 22, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Session
R. WOOD1, G. ENGLAND2, B.C. TEE1, J. CHAUDHRY3, and Z. SUN1, 1Orthodontics, Ohio State University, Columbus, OH, 2Ohio State University, Columbus, OH, 3Radiology, Ohio State University, Columbus, OH
Objectives: Cone beam computed tomography (CBCT) is routinely used to measure alveolar bone dimensions. This study investigated factors likely affecting the accuracy of such measurements. Methods: Marker holes, apical to maxillary and mandibular molar roots, and mesio-distal molar occlusal reference grooves were created in fresh pig heads (n=26 quadrants), followed by CBCT scans at 0.4 and 0.25 mm voxel sizes before and after soft tissue removal. Subsequently, bucco-lingual sections bisecting the marker holes were cut, from which physical alveolar bone height and thickness were measured.  Two blinded, calibrated raters, using Dolphin 3-D and OsiriX software, independently collected alveolar bone height measurements from CBCT images. Differences between CBCT and physical measurements (DCBCT-Phy) were calculated. The mean DCBCT-Phy and limit of agreement (LOA, ±1.96SD) for each factor were depicted by Bland-Altman methods. The influence of each factor was examined by repeated measures ANOVAs.  Result s:  The rater factor affected CBCT measurements in both jaws, with mean DCBCT-Phy from a more-experienced rater significantly (p<0.05) closer to "0" than from a less-experienced rater.  Their LOA ranges were similar (Maxilla, 0.16±2.21mm vs.-0.48±2.53mm; Mandible, 0.01±1.38mm vs. -0.70±1.48mm).. The software factor affected CBCT measurements in both jaws, with mean DCBCT-Phy from Osirix significantly (p<0.05) closer to "0" than from Dolphin-3D despite similar LOA ranges (Maxilla, -0.09±2.38mmvs. -0.22±2.42mm; Mandible, -0.30±1.47mm vs. -0.39±1.38mm). The soft-tissue factor only affected the mandible significantly (p<0.05), with mean DCBCT-Phy from soft-tissue-absent specimens closer to "0" than those from soft-tissue-present specimens (Maxilla, -0.13±2.82mm vs. -0.19±1.99mm; Mandible, -0.25±1.70mm vs. -0.43±1.22mm). The voxel-size factor had an insignificant effect.  Generally, mandibular CBCT measurements exhibited smaller LOA ranges than maxillary, possibly because mandibular alveolar bone was thicker. Conclusions:   Individual alveolar bone height measurements from CBCT images can deviate from physical truth by a clinically relevant amount (1.2-2.5mm). Factors such as rater, software, tissue presence/absence, and bone thickness can introduce systematic sub-millimeter errors.
This abstract is based on research that was funded entirely or partially by an outside source: Delta Dental

Keywords: Bone, Orthodontics, Periodontics, Periodontium-gingiva and Radiology
See more of: Diagnostic Sciences II
See more of: Diagnostic Sciences