## 4 Discussion
It was observed that there was a difference in bone width between the edentulous region and the symmetrical toothed region in patients in whom orthodontic treatment was planned, and it was determined that the bone width in all edentulous regions evaluated was less than the symmetrical toothed regions. For this reason, it was revealed that an existing insufficient bone width is a risk factor for orthodontic tooth movement in edentulous areas when being evaluated for orthodontic treatment. [PERSON] et al. showed that the ridge widens in edentulous areas closed by orthodontic tooth movement. However, they did not evaluate the edentulous bone in the relevant region before and after orthodontic movement with any 3D evaluation methods, such as CBCT. Additionally, the authors stated that this enlargement after treatment was due to the width of the moving tooth and not due to new bone formation [23]. In this study, the height and width of the bone in areas with a single missing tooth were evaluated with CBCT. It is not possible to evaluate the width of the bone with two-dimensional radiographs, such as panoramic and periapical radiographs. For this reason, we evaluated the bone width of the toothed and edentulous sides using CBCT in patients with planned orthodontic tooth movement. The results obtained revealed insufficient bone width in the edentulous areas and the importance of evaluating the edentulous areas through CBCT in patients planning to undergo orthodontic tooth movement, especially in terms of possible deficiencies. The present study compared the bone width of the spaces 18.01 \(\pm\) 3.17 months after tooth extraction with their symmetrical sides and determined the reduction in the ridge width for the incisor, premolar, and molar regions to be 48.02%, 48.05%, and 55.32%, respectively. It was determined that in cases of a single missing tooth in incisors, premolars, and molars, bone loss in the crest caused a difference between regions, and compared to the toothed side, age and gender were not significant with regard to the change in bone width. In terms of the width of dentulous areas, the incisor region was the narrowest at 3.60 \(\pm\) 2.12 mm, and the molar region was the region that underwent the most resorption, with a decrease of 55.32%. These results revealed that when orthodontic tooth movement is planned to correct the molar and/or canine relationship or to close the space(s) in cases where the molar and canine relationship is normal, we will encounter spaces with an insufficient bone width. This study showed that the lower first molars (teeth 36 and 46) are the most common missing teeth, with a rate of 43.2%, and, therefore, we will encounter missing first molars the most in individuals with a single missing tooth. When the spaces where the first molars are missing are planned to be closed with orthodontic tooth movement, if new bone formation does not occur, as emphasized by [PERSON] et al., there will be no or minimal bone support in the buccal/vestibule and/or lingual/palatal regions for the tooth that will be moved into the space [24]. Such a tooth is likely to have a poor long-term prognosis, as well as mobility and gingival recession problems, after orthodontic treatment. In addition, in the current study, when the symmetrical toothed molar region was taken as a reference, there was an average available width of 4.96 mm in the edentulous molar region despite the need for an average bone width of 11.03 mm, which brings to mind the option of bone and/or soft tissue augmentation to increase the ridge width before tooth movement. In such a case, if dental implant placement had been planned, advanced implant surgery and/or augmentation operations would have been inevitable to increase the bone width before implant surgery. Therefore, bone augmentation should be considered among the treatment options for insufficient ridges before orthodontic tooth movement. Animal studies have demonstrated that tooth movement is possible for bone defects augmented using Xeno and alloplastic graft material [29].