## 4 Discussion
While limited tooth movement has been attributed to NASO, studies reported the high risk of palatal bone resorption in high-angle Class II patients with normal incisal inclination and small medullary space in the palatal bone [14; 15; 16; 17]. Additionally, articles cautioned against potential esthetic and bone-thickness-related issues on the labial side during extraction orthodontic treatment [14; 18]. These studies highlight the importance of performing extraction orthodontic treatment (NASO) within a range that avoids functional problems with the dentition and maxillary alveolar bone, emphasizing that orthodontic treatment alone should not be pushed beyond limits to achieve a desirable outcome. Table 5 indicates that maxillary incisor retraction, measured by the U1 C to N-perpendicular value, was \(\Delta-6.57\) for the ASO group and \(\Delta-4.11\) for the NASO group. Similarly, the U1 R to N-perpendicular value was \(\Delta-4.58\) for the ASO group and \(\Delta-1.45\) for the NASO group. Thus, these findings suggest that NASO alone can provide sufficient movement with a root movement of \(\Delta-1.45\), achieving satisfactory results through controlled tipping to bodily movements. In contrast, previous studies have often overlooked the importance of considering the inclination of the mandibular incisors in ASO diagnosis and treatment planning. This may be attributed to the varying thickness of the symphysis in the mandibular incisor area; generally, the amount of bone present in this area is lesser than that in the maxillary incisor area, limiting root movement. Consequently, bodily movement of the mandibular incisors is challenging, and efforts generally lead to only tipping movement. Nevertheless, the advantage of mandibular ASO lies in its ability to move the mandibular incisors. However, in Class II patients, where the roots are already positioned posteriorly, there are fewer indications for moving the root backwards through ASO. According to [PERSON] et al. [17], even though the mandible is smaller in the anteroposterior dimension in Class II patients, lower lip protrusion can occur due to lip incompetence or protruding maxillary incisors pushing the lower lip downward and forward. In such cases, reducing maxillary protrusion alone may be sufficient to secure lower lip retraction. However, mandibular extraction orthodontics or posterior movement of point B through ASO in Class II patients may lead to excessive retrusion of the lower lip, resulting in an unesthetic outcome [9]. Mandibular ASO may be indicated in cases where the IMPA is not large, but the mandibular incisors exhibit severe extrusion despite being uprighted, requiring bodily movement and intrusion, or when there are concerns about gingival recession during retraction. However, in mandibular ASO for Class II patients with a large IMPA, counterclockwise rotation of point B is often necessary, which can make the surgical part difficult and potentially yield unsatisfactory outcomes [9]. The findings of the current study suggest that although the ANB was normalized, increased selective retraction of point A than that of point B was not observed in the ASO group, primarily due to technical difficulties in point B-oriented counterclockwise rotation of the mandibular anterior segment. Therefore, in Class II patients with a normal curve of Spee in the mandibular incisors, where sufficient movement of the maxillary incisors through ASO is expected to enhance facial esthetics, it is advisable to consider orthodontic treatment in the mandible to improve IMPA while maximizing the preservation of point B, rather than opting for mandibular ASO (Figure 3A,B).