## 4 Discussion
In a study comparing the FD of pre- and post-implants, an increased fractal dimension of the post-implant was reported, and a decrease in the FD was observed in a failed implant [34]. In this study, the mean value of the FD in all experimental groups and the negative control group showed a higher value than that of the positive control group. The decreased FD of the positive control group suggested decreased bone density and a trabecular pattern surrounding the disc. The mean value of the FD in the negative control group and the decontaminated discs with air-polishing treatment, chlorhexidine rinse, and additional Er:Yag laser treatment showed a statistically significant difference compared to the positive control group, but the difference among the groups was insignificant. This result implies an increase in the bone structure and trabeculae around the discs in the groups AC, ACE, and N compared to the contaminated discs. Bone density evaluation using computed tomography (CT) is based on radiological density and depends on the attenuation of X-ray beams by the type of tissue [39]. The BMD of a region of interest can be quantified as an average of the grayscale value, and a low grayscale value indicates a low bone density [40]. The density estimations using both two-dimensional and three-dimensional methods showed statistically insignificant differences [41]. In the current study, the mean GV was measured based on three-dimensionally reconstructed segmentation. The segmentation consisted of an additional 20 pixels surrounding the disc to include the trabecular pattern. The mean GV values of all experimental groups and the negative control group were higher than those of the positive control group, implying decreased bone density of the segmentation surrounding the discs. The mean values of the GV of the negative control group and the decontaminated discs with air-polishing treatment, chlorhexidine rinse, and Er:Yag laser treatment showed statistically significant differences compared to the positive control group, but there was an insignificant difference between the two groups. The result indicates an increase in bone density in the negative control group and the decontaminated discs with air polishing treatment, chlorhexidine rinse, and Er:Yag laser treatment compared to the contaminated discs. There are some limitations in the present study. Threshold settings for bone and objects, such as implants and discs, are major procedures in micro-CT analysis. In this study, thresholds were set for titanium and bone, within the possibilities of variance due to experimental conditions and characteristic differences among individual specimens [42]. In addition, the ROI for evaluation was determined according to the titanium disc threshold, and there was a possibility that the value of ROI might differ due to the threshold set for bone. Due to the small sample size, there is still a limitation in terms of the statistical verification of individual specimen differences. Also, the analysis of the images corresponding to the histologic images obtained from micro-CT was performed manually, which could lead to inaccuracy. There are different methods used for the calculation of FD, and the box-counting method, which was employed in this research, is one of the most commonly used, although there is no consensus on the gold standards [43]. Despite the limitations, only a few studies have reported the osseointegration of decontaminated titanium discs including dental implants, and there are various methods used for decontamination, leading to a lack of evidence for a universal decontamination method. The present study examined decontaminated titanium discs to investigate the surface decontamination and osseointegration of these discs. The SEM images could confirm the status of covered S. aures in the experimental groups, and the histologic specimens showed favorable bone formation.