This RCT aims to evaluate the effectiveness of a novel 3D printed reverse twin block appliance in the management of maxillary deficiency in growing patients having class III malocclusion. The clinical outcomes of this appliance will be compared with the conventional reverse twin block appliance over 6 months treatment period.

primary objective is evaluating of the effectiveness of 3DRTB in correcting sagittal discrepancies due to maxillary deficiency in class III malocclusion compared to conventional one while secondary objectives are assessment of transverse and vertical jaw relationship produced by 3DRTB compared to CRTB and to evaluate the soft tissue profile of class III patients and to evaluate the maxillary and mandibular incisor inclination, also assessment of patient perception with both appliances by using questionnaire and finally to assess the impact of 3DRTB on oral health compared to CRTB by using oral hygiene index.

Inclusion Criteria:

1. The age group selected is mixed dentition group 8-13 years with residual potential maxillary growth. Patient maturity will be assessed using the Cervical Vertebral Maturation (CVM) method on lateral cephalogram, patients in CS1-CS3 stages will be included to ensure remaining maxillary growth.

2. Presence of permanent first molar with lower anterior teeth to retain the appliance.

3. Skeletal/dental class III tendency with anterior cross bite or reverse overjet: a. Clinically the overjet is equal or less than zero up to -3 mm.

   b. Cephalometric ANB angle equal or less than zero up to -3 degrees and Wits appraisal ≤ -2.

4. Prescence of unilateral or bilateral posterior crossbite.

5. Mild to moderate anterior crowding.

6. Acceptable oral hygiene baseline defined by oral hygiene index (OHI). -

Exclusion Criteria:

1. Patients with cleft lip and palate and/or craniofacial anomalies.
2. History of previous orthopedic and/or orthodontic treatment.
3. Presence of uncontrolled systemic disease or medically compromised status.
4. Uncooperative patient/parents.