The aim of this study is to compare the effectiveness of two different orthodontic treatment methods used in patients with skeletal Class II malocclusion, a condition in which the lower jaw is positioned backward. Approximately 80% of Class II malocclusions are due to mandibular retrusion. Therefore, functional appliances that stimulate mandibular growth in growing individuals have been widely used in orthodontics for many years.

In recent years, clear aligner systems have become increasingly popular in orthodontic practice. A mandibular advancement feature was recently integrated into these aligners, allowing for simultaneous tooth alignment and forward positioning of the lower jaw. In this study, the newly developed Mandibular Advancement Appliance (MAA), based on clear aligners, will be compared to the traditional functional appliance known as the Activator.

Who Can Participate in the Study? Children with retrusive lower jaws who are in the growth and development period Individuals with no prior orthodontic treatment Patients with specific levels of dental protrusion (overjet) Those with good general health and no contraindications for CBCT imaging What Will the Treatment Process Involve?

Participants will be randomly assigned to one of three groups:

MAA group (clear aligners with mandibular advancement) Activator group (traditional removable appliance) Control group (no treatment, only observation) The active treatment period will last approximately 7-8 months, followed by a retention phase. All patients will be monitored regularly, and strict adherence to appliance use will be expected.

How Will the Outcomes Be Assessed? Before and after the treatment period, participants will undergo cone-beam computed tomography (CBCT) scans to obtain detailed three-dimensional images of the jaws. These images will be analyzed to evaluate volumetric changes. All measurements will be performed by a trained orthodontic specialist using dedicated software.

Potential Benefits for Participants:

Participants will receive close clinical monitoring throughout the study period. The use of advanced imaging technologies may support the development of more effective and individualized treatment plans.

Safety and Confidentiality:

This study has received ethical approval and will be conducted in accordance with relevant data protection and research ethics standards. All personal data will be kept confidential. Written informed consent will be obtained from all participants and/or their legal guardians.

Inclusion Criteria:

• Cervical vertebral maturation (CVM) stage 2 or 3
• Bilateral full or half cusp Class II molar relationship
• Skeletal Class II relationship associated with mandibular retrognathia (ANB angle > 4° and SNB angle < 78°)
• Horizontal or average growth pattern (SN-GoGn ≤ 38°)
• Overjet distance between +4 mm and +8 mm; (6) Good patient compliance throughout the treatment.

Exclusion Criteria:

• CVM stage 5 or 6;(2) Previous orthodontic treatment;
• Presence of maxillary prognathism
• High-angle growth pattern (SN-GoGn > 38°)
• Transverse orthodontic anomalies or facial asymmetry
• Palpation-induced tenderness or pain in the masticatory muscles
• Presence of clicking, crepitus, pain, or tenderness in the temporomandibular joint (TMJ)
• Congenital or acquired craniofacial deformities
• Poor patient compliance or oral hygiene
• Any condition that could interfere with CBCT imaging.