## 4 Discussion  
Many studies have investigated the effectiveness of maxillary molar distalization using CAs with considerably variable outcomes. Although some studies have demonstrated treatment accuracy rates of \(\leq\)87%, others have reported low accuracy rates of 36-42%, with many cases of intrusion and buccal tipping instead of the desired body movement [19; 20; 21]. Reciprocal forces pose a serious risk of anterior teeth retraction during molar distalization, possibly offsetting some of the achieved distalization [20]. These side effects and limitations of molar distalization with CAs are largely attributed to the lower stiffness of CAs than conventional wire-based orthodontic appliances, with less predictable biomechanics due to variable contact points with different parts of the teeth [12; 13]. However, accurate bodily movement can be achieved if the elastic energy stored in CAs is efficiently transferred to the teeth. Attachments increase the contact area between the CAs and teeth, facilitating the uniform and direct transmission of forces [21]. In this study, we also planned to place vertical attachments on the first and second molars to prevent tipping and achieve posterior bodily movement, following the literature that attachment design has a minimal effect on molar posterior movement [22]. However, excessive attachments can increase the difficulty of CA usage and feelings of foreignness [16]. The efficiency of CA treatment can be improved by varying the thickness. Studies have demonstrated a strong correlation between the CA thickness and the force transferred to the teeth [23]. However, increasing the overall thickness alters the mechanical properties of CAs, thereby affecting localized stress distribution in specific areas. Vacuum thermoforming results in non-uniform thickness across the appliances, leading to inconsistent force application [24]. This study is built upon the work of [PERSON] et al. [16], focusing on two specific strategies: the application of an enhanced structure (localized thickening) to the buccal areas of CAs to increase the local stiffness and the use of attachments on the first molars. We aimed to analyze the effects of these modifications on the bodily distalization of maxillary second molars. Here, maxillary buccal tipping and intrusion trends were similar in all groups, consistent with the finite element method results reported by [PERSON] et al. [25]. However, significant differences in force magnitude were observed between the groups with attachments and those with enhanced structures. In the mesiodistal direction (Fy), group 3 with attachments and enhanced structures exhibited the largest force. Vertical force (Fz) resulted in significant intrusive forces in groups 3 and 4 with enhanced structures, but the differences between groups with and without attachments were relatively small. These findings suggest that enhanced structures significantly affect force generation in Fy and Fz directions better than attachments, improving molar distalization, consistent with previous reports on increased forces with increased CA thickness [26]. The analysis of buccolingual forces (Fx) revealed buccolingual tipping in all groups, consistent with previous reports [20; 25; 27]. This is possibly due to greater force transmission anterior to the attachment on the buccal side of the second molar during distalization. These results suggest the positive effect of molar distalization on occlusion construction in Class II malocclusion treatment. Intrusive force (Fz) in CA treatment minimizes the increase in vertical height, which is a common issue observed with conventional fixed appliances and devices [28]. This intrusive force, possibly due to the CA thickness and \"bite block\" effect, is particularly beneficial to treat Class II malocclusions with a hyperdivergent vertical pattern. The biomechanics of tooth movement are complex, depending on the center of resistance of the tooth and the forces acting on it [29].