# Long-Term CBCT Evaluation of Mandibular Third Molar Changes after Distalization in Adolescents
## 4 Discussion
However, they also demonstrated that maxillary third molars show spontaneous eruption over time, despite their position after distalization. With regard to the positional changes of third molars after distalization, significant tipping, of \(8.9^{\circ}\), was observed in the treated group. To reduce this distinct tipping of second molars during molar distalization, a surgical extraction of the third molar bud was recommended due to fulcrum action [12]. Unfortunately, the study had a limited evaluation immediately after distalization with a few patients in the germectomy group and only used two-dimensional images. In our study, stable structures were applied in the mandible to evaluate the positional changes in the three stages (pre- and post-distalization and retention). [PERSON] et al. [30] evaluated mandibular and dentoalveolar changes using functional appliances based on the mandibular reference plane with [PERSON]'s structural method on a two-dimensional cephalometric radiograph, while we used CBCT images to analyze a three-dimensional determination of stable structures in the mandible, as seen in Figure 4. [PERSON] et al. [31] showed that three-dimensional evaluations are more precise and accurate than the two-dimensional approach. [PERSON] et al. [32] demonstrated that the anterior contour of bony chin at pogonion showed no remodeling, while [PERSON] et al. [33] showed that as a stable structure in the mandible, the mental foramen can be used for regional superimposition in the three-dimensional mandibular evaluation of growing patients. In our study with CBCT images, we used a reference line from the pogonion to the superior point of the mental foramen as stable structures to evaluate the anterioposterior movement of the lower posterior teeth. Regarding maxillary third molars, the distalization of posterior teeth can occur in adolescents who have retained third molars [27]. Molar distalization has no significant impact on the normal eruption of maxillary third molars, which suggests that surgical removal may not be required prior to distalizing maxillary molars in adolescents with developing third molars [16; 34]. Additionally, [PERSON] et al. [35] reported that the increased posterior available space in the mandible was mainly due to bony resorption on the anterior border of the ramus in growing patients. They also found that the average available spaces increased by 1.2 mm in females under the age of 16 and by 1.5 mm in males under the age of 17 per side, annually. Our study found that the mandibular third molars showed a downward and buccal position after distalization in the long-term compared with the control group. This means that clinically, there is a possibility that third molars could be impacted after distalizing mandibular dentition in adolescents. In addition, periodontal stability is one of the important factors in patients undergoing orthodontic treatment with skeletal anchorage, such as MCPP. Several clinical indicators of oral hygiene and periodontal status are monitored. For example, the plaque index, bleeding on probing, and other biomarkers can be used to assess the periodontal status of orthodontic patients [36; 37]. To prevent the loosening of skeletal anchorage as in implant failure, it is recommended to use chlorhexidine-based mouthwash [38]. For long-term success, periodontal care is required throughout orthodontic treatment and in the maintenance phase. One limitation of our study was that the control group comprised adult patients whose CBCT data were obtained for purposes other than this research, such as for periodontic treatment or due to pathologic disease; the longitudinal sample was limited for ethical reasons. Therefore, the positional changes of their third molars could not be evaluated at each treatment stage, as was possible with the treated group. Furthermore, since the control group in this study had a small number of subjects, the evaluation of third molar angulation is needed in a larger sample with a broad age range.