## 4 Discussion  
Dental clinicians frequently encounter the need for palatal appliances for transverse maxillary correction. The use of RPE or MARPE can promote skeletal and alveolar bone changes, with the most studied aspects being the opening of the midpalatal suture, changes in the position of the basal bone, and tilting of the molars [15; 16; 17]. One of the objectives of miniscrew-assisted maxillary expansion is to secure alveolar bone coverage along with lateral expansion of the maxillary buccal segment for proper transverse maxillary dimensions. According to a previous study, MARPE has demonstrated favorable skeletal and dentoalveolar expansion even in young adults, thus expanding the age limit for nonsurgical maxillary expansion [10]. This study aimed to analyze the effects of miniscrew-assisted rapid palatal expansion using dental cone-beam CT in adolescents who, as they age, are likely to receive orthodontic treatment the most. A comprehensive three-dimensional view of the maxilla is required to analyze the changes during the expansion period, and evaluating the changes using CBCT is important. In this study, the expansion pattern was triangular in both the coronal and axial planes. Extension of the entire craniofacial structure can be depicted in the coronal plane as a triangular pattern based on the maxillary dental arch. In our study, significant expansion was observed at the NW-upper (0.47 \(\pm\) 0.36 mm), NW-lower (3.0 \(\pm\) 1.16 mm), MxBBW (3.58 \(\pm\) 1.18 mm), and Mx6W (5.25 \(\pm\) 1.81 mm), with these expansions increasing progressively in the order listed above. Hence, we observed a decreasing amount of upward and skeletal expansion ranging from 25% to 61%, which is consistent with that reported in previous research [7; 18; 19]. This triangular expansion pattern enlarges the alveolar bone area to a greater extent, thereby allowing greater alveolar bone enlargement relative to the basal bone. Although not reported in the Sections 2 and 3, correlation analysis between the amounts of hard tissue expansion and patients' characteristics (sex and age) was performed. The results of this analysis showed no significant correlation between the amounts of hard tissue expansion and patients' characteristics (sex and age). This can be interpreted as MARPE being able to expand hard tissues to similar extents regardless of age and sex. However, it is important to note that only successfully expanded patients were enrolled in this study, so this interpretation should be accepted with caution. Additionally, the small sample size of the study makes the correlation analysis result less reliable. Buccal tipping of the anchor teeth owing to the maxillary expansion is consistent with the results in previous studies [5; 7; 18]. Inclination of the maxillary first molars increased significantly after expansion (2.97\({}^{\circ}\)\(\pm\) 2.49\({}^{\circ}\)) in this study. Although MARPE was designed to maximize skeletal expansion while keeping the teeth in the original alveolar bone position, the current results indicate some expansions in the anchored posterior teeth. This mean increase in buccal inclination may be clinically insignificant. The largest change identified in our sample was 9.6\({}^{\circ}\), which was clinically significant. Clinicians must be aware of the possibility of significant buccal tipping of the anchored maxillary molar, even when MARPE is used. This buccal tipping may cause loss of the buccal alveolar bone in the corresponding maxillary molar [5]. The whole palatal segment may possibly rotate after expansion, resulting in buccal tipping of the alveolar bone and posterior teeth in a mass without the so-called sole dental expansion. However, this hypothesis should be evaluated using more sophisticated measurements in these areas, which was beyond the scope of this study. Several studies have reported on the parallel expansion of the midpalatal suture with MARPE [9]. The current study identified a greater expansion in the ANS area than in the posterior (first molar and PNS) area.