Quantification of bone quality using different cone beam computed tomography devices: Accuracy assessment for edentulous human mandibles.

Purpose: To determine the accuracy of the latest cone beam computed tomography (CBCT) machines in comparison to multi-slice computer tomography (MSCT) and micro computed tomography (micro CT) for objectively assessing trabecular and cortical bone quality prior to implant placement. Materials and methods: Eight edentulous human mandibular bone samples were scanned with seven CBCT scanners (3D Accuitomo 170, i-CAT Next Generation, ProMax 3D Max, Scanora 3D, Cranex 3D, Newtom GiANO and Carestream 9300) and one MSCT system (Somatom Definition Flash) using the clinical exposure protocol with the highest resolution. Micro-CT (SkyScan 1174) images served as a gold standard. A volume of interest (VOI) comprising trabecular and cortical bone only was delineated on the micro-CT. After spatial alignment of all scan types, micro-CT VOIs were overlaid on the CBCT and MSCT images. Segmentation was applied and morphometric parameters were calculated for each scanner. CBCT and MSCT morphometric parameters were compared with micro-CT using mixed-effect models. Intraclass correlation analysis was used to grade the accuracy of each scanner in assessing trabecular and cortical quality in comparison with the gold standard. Bone structure patterns of each scanner were compared with micro-CT in 2D and 3D to facilitate the interpretation of the morphometric analysis. Results: Morphometric analysis showed an overestimation of the cortical and trabecular bone quantity during CBCT and MSCT evaluation compared to the gold standard micro-CT. The trabecular thickness (Tb.Th) was found to be significantly (P < 0.05) different and the smallest overestimation was found for the ProMax 3D Max (180 mu m), followed by the 3D Accuitomo 170 (200 mu m), Carestream 9300 (220 mu m), Newtom GiANO (240 mu m), Cranex 3D (280 mu m), Scanora 3D (300 mu m), high resolution MSCT (310 mu m), i-CAT Next Generation (430 mu m) and standard resolution MSCT (510 mu m). The underestimation of the cortical thickness (Ct.Th) in ProMax 3D Max (-10 mu m), the overestimation in Newtom GiANO (10 mu m) and the high resolution MSCT (10 mu m) were neglible. However, a significant overestimation (P < 0.05) was found for 3D Accuitomo 170 (110 mu m), Scanora 3D (140 mu m), standard resolution MSCT (150 mu m), Carestream 9300 (190 mu m), Cranex 3D (190 mu m) and i-CAT Next Generation (230 mu m). Comparison of the 2D network and 3D surface distance confirmed the overestimation in bone quantity, but only demonstrated a deviant trabecular network for the i-CAT Next Generation and the standard resolution MSCT. Intraclass correlation coefficients (ICCs) showed a significant (P < 0.05) high intra-observer reliability (ICC > 0.70) in morphometric evaluation between micro-CT and commercially available CBCT scanners (3D Accuitomo 170, Newtom GiANO and ProMax 3D Max). The ICC for Tb.Th and Ct.Th were 0.72 and 0.98 (3D Accuitomo 170), 0.71 and 0.96 (Newtom GiANO), and 0.87 and 0.92 (ProMax 3D Max), respectively. Conclusions: High resolution CBCT offers a clinical alternative to MSCT to objectively determine the bone quality prior to implant placement. However, not all tested CBCT machines have sufficient resolution to accurately depict the trabecular network or cortical bone.