As accurate CT attenuation was not measured due to the lower spatial resolution of CBCT compared with MSCT, a CBCT was recognized as unsuitable for evaluating bone quality. However, several groups have recently reported the potential use of CBCT systems as an apparatus for estimating bone quality. Isoda et al. described a high correlation between voxel values obtained by CBCT and IT of the implant [41]. Moreover, Nomura et al. reported a high correlation between density values from the CBCT and MSCT systems [42].

According to the measurement of the average voxel values in this study, a significant difference was seen between the high IT group and the low/medium IT group, but no significant difference was found between the low and medium IT groups (Fig. 7). Specimens showing IT ≥ 40 N cm were thought to have a good bone quality, and voxel values at each part of the implant (neck, middle apex) were compared between groups with IT < 40 (combined low and medium IT groups) and ≥ 40 (high IT group) (Fig. 8). The results suggested that the neck and apex parts in the high IT group showed significantly higher voxel values than the middle and apex parts of the low/medium IT group.

Using a MSCT system for preoperative diagnosis of bone quality, classified as five stages according to CT attenuation, and detailed diagnosis was performed for the whole treatment area [43]. In this study, no significant difference was found when bone quality was compared between the three different IT groups, but when comparisons were made between two groups (low/medium vs high), significant differences were observed between groups and also between measurement sites (Figs. 6 and 7). Diagnosis of bone quality using CBCT does not seem as detailed as results from MSCT, but the diagnosis of whether bone quality is sufficient appears feasible.

CBCT systems offer many advantages over MSCT systems, including low exposure doses, high resolution, reduction of metal artifacts, ease of installation, and utility as a diagnostic tool in implant treatment [41, 42]. Due to the expanded utility of CBCT systems for dental implant diagnosis, the establishment of techniques for diagnosing bone quality by CBCT is necessary.