This narrative review explores the applicability, biomechanics, indications, contraindications, scope, limitations, and factors influencing long-term stability and successful outcomes of Clear Aligner Therapy (CAT) in adult orthodontics. CAT, a significant shift in modern orthodontics, offers a convenient and aesthetic alternative to traditional fixed appliance treatments. The review includes various studies, case reports, and analyses to provide a comprehensive understanding of CAT's effectiveness and challenges. Key points include: - **Biomechanics**: Clear aligners are effective for simple tooth movements like tipping and minor rotations. More complex movements require force-driven systems and attachments. - **Clinical Applications**: CAT is suitable for managing crowding, spacing issues, deep overbites, and narrow arches. It is also used for open bite and deep bite corrections, though these cases are more challenging. - **Indications and Contraindications**: CAT is indicated for mild to moderate malocclusions, fully erupted permanent teeth, and non-growing patients. Contraindications include severe crowding, skeletal discrepancies, and severely rotated teeth. - **Long-Term Stability**: Patient compliance, orthodontic expertise, and proper anchorage planning are crucial for long-term success. Retention phases are essential to prevent relapse. - **Material Science**: Advances in aligner materials, such as multi-layer designs, enhance effectiveness and stability. - **Conclusion**: CAT is a prevalent choice for mild to moderate malocclusions and is increasingly being used for more complex cases. Ongoing research is needed to expand its application and optimize outcomes. The review emphasizes the importance of careful case selection, meticulous planning, and adherence to retention protocols for achieving sustained success with CAT.This narrative review explores the applicability, biomechanics, indications, contraindications, scope, limitations, and factors influencing long-term stability and successful outcomes of Clear Aligner Therapy (CAT) in adult orthodontics. CAT, a significant shift in modern orthodontics, offers a convenient and aesthetic alternative to traditional fixed appliance treatments. The review includes various studies, case reports, and analyses to provide a comprehensive understanding of CAT's effectiveness and challenges. Key points include: - **Biomechanics**: Clear aligners are effective for simple tooth movements like tipping and minor rotations. More complex movements require force-driven systems and attachments. - **Clinical Applications**: CAT is suitable for managing crowding, spacing issues, deep overbites, and narrow arches. It is also used for open bite and deep bite corrections, though these cases are more challenging. - **Indications and Contraindications**: CAT is indicated for mild to moderate malocclusions, fully erupted permanent teeth, and non-growing patients. Contraindications include severe crowding, skeletal discrepancies, and severely rotated teeth. - **Long-Term Stability**: Patient compliance, orthodontic expertise, and proper anchorage planning are crucial for long-term success. Retention phases are essential to prevent relapse. - **Material Science**: Advances in aligner materials, such as multi-layer designs, enhance effectiveness and stability. - **Conclusion**: CAT is a prevalent choice for mild to moderate malocclusions and is increasingly being used for more complex cases. Ongoing research is needed to expand its application and optimize outcomes. The review emphasizes the importance of careful case selection, meticulous planning, and adherence to retention protocols for achieving sustained success with CAT.