## 4 Discussion
The enhanced structure method with flowable resin used in this study has the advantage of easy clinical application. The conventional CA fabrication method, thermoforming, may not be uniform in thickness during the fabrication process [32,33], and when modifications to the treatment are required, it is cumbersome to remake the appliance, and direct 3D printing requires additional design work. On the other hand, the flowable resin approach has the advantage that it can be applied immediately in the clinic and can be modified as needed during treatment. To better understand the impact of flowable resin reinforcement, it is important to consider its mechanical properties. Chamfil Flow (Denkist, Republic of Korea) is a nano-based, light-cured composite with radiopaque properties and low polymerization shrinkage, enhancing stability and reducing deformation. However, it has lower microhardness and shear bond strength (1.9 MPa) compared to Filek XTE (16.8 MPa), leading to weaker adhesion and reduced rigidity. Resin reinforcement increased mesiodistal force application and reduced unwanted tipping and rotation, improving force distribution. Future studies should explore resins with higher mechanical strength and adhesion for optimal aligner modifications. This study has several limitations. First, as an in vitro study, it does not fully replicate clinical conditions, where factors like bone density, periodontal ligament compliance, occlusal forces, and intraoral temperature changes can affect aligner performance [18]. Future studies should incorporate dynamic models or clinical trials. Second, CAs may degrade over time, altering force transmission and treatment predictability [11]. Long-term intraoral studies are needed to assess their biomechanical stability. Third, the flowable resin used in this study has lower microhardness and shear bond strength compared to other dental composites. While it enhances force application, its relatively low stiffness and adhesion may limit its reinforcement effect. Variability in resin thickness during application may also introduce minor inconsistencies in force distribution. Standardizing enhancement methods and testing alternative resins with higher rigidity could improve reproducibility and effectiveness. Fourth, attachments were not considered despite their role in bodily movement [9]. Future studies should evaluate the combined effects of enhanced structures and attachments. Finally, this study focused on a single tooth, while real treatments involve multiple teeth and occlusal interactions. Clinical trials incorporating these factors are necessary to validate the findings. Based on these limitations, future research should explore several key areas. First, in vivo clinical trials should be conducted to validate the findings in real treatment conditions, considering physiological factors such as bone density, occlusal forces, and saliva exposure. Second, long-term studies on the mechanical stability of structurally modified aligners will help determine their durability and effectiveness over extended treatment periods. Third, integrating finite element analysis with experimental models can provide deeper insights into force distribution and aligner performance. Lastly, optimizing the combination of attachments and structural modifications may further improve control over bodily movement and minimize unwanted tipping and rotation.