The aim of the current study is to evaluate the skeletal, dental, soft tissue, TMJ, and upper airway size changes associated with a new design of twin block compared to the conventional twin block appliance. Additionally, patients' satisfaction with the two designs will be assessed.

Twin block appliance is the gold standard for the treatment of skeletal class II patients with deficient mandible. Yet, it has some drawbacks as proclination of the mandibular incisors, development of posterior open bite and the unesthetic appearance. Many modifications in twin block A new design were made to overcome the previous problems, as adding incisor capping, Clasps, sagittal blocks, and esthetic twin block appliances. In the current trial A new design of esthetic twin block appliance with sagittal blocks is investigated and the post treatment skeletal, dental, and soft tissue, TMJ, and upper airway size will be assessed and compared to the changes associated with the conventional design of twin block. Moreover, patient satisfaction with the appliance will be assessed with both appliances.

Inclusion Criteria:

• skeletal class II deficient mandible
• Class II molar and canine relation
• male growing patients CVM 2,3 age range 10-14
• normal vertical growth pattern
• ANB > 4
• mild to moderate crowding

Exclusion Criteria:

• Previous orthodontic treatment.
• Craniofacial syndrome.
• Periodontal disease.
• Extracted first permanent molars.