Patients with skeletal Class II malocclusion due to mandibular retrognathism will be recruited and randomly allocated to three equal groups. first group will be treated by pushing orthopedic force mechanics, second group will be treated by pulling orthopedic force mechanics, and third group will be observed for 9 months to detect the natural growth changes. Skeletal changes will be evaluated and the treatment changes will be compared with the natural growth changes. The study hypothesis is that use of direct bimaxillary miniplate anchorage in conjunction with fixed functional appliance (pushing orthopedic force) or closed coil spring (pulling orthopedic force) will induce statistically significant skeletal mandibular growth in comparison to natural mandibular growth changes.

A randomized controlled clinical trial will be conducted to address the aim of the study. Thirty-nine growing patients with skeletal Class II malocclusion due to mandibular retrognathism will be recruited. The sample will be randomly allocated to three equal groups, each including thirteen subjects. Group A will be treated by pushing orthopedic force mechanics using fixed functional appliance (Sabbagh Advanced Repositioning Appliance) anchored to four miniplates (two miniplates inserted in the mandibular symphysis and two infrazygomatic miniplates), and Group B, will be treated by pulling orthopedic force mechanics using Class II springs (CS Class II correction device) anchored to four miniplates (two inserted in the mandibular posterior buccal segment and two inserted in the maxillary anterior segment). In both groups, the appliances will be removed after reaching an edge-to-edge incisor relationship or after 9 months, whichever happens first. A similar third group (Group C) will be observed for 9 months to detect the natural growth changes. Skeletal changes will be evaluated using pretreatment and posttreatment cone beam computed tomography scans (CBCT). The treatment changes will be compared with the natural growth changes observed in group C. Other variables will be also examined including, the dentoalveolar effects, the soft tissue profile, and the patient's acceptance to this treatment modality.

Inclusion Criteria:

• Chronological age ranges from 11 years to 13 years.
• Skeletal Class II malocclusion with a deficient mandible (SNB ≤ 76°).
• Horizontal growth pattern (MP/SN ≤ 39°).
• Angle Class II division 1 malocclusion with at least 5 mm overjet.
• Mandibular arch crowding less than 5 mm.
• The patients have to be in the prepubertal growth stage (cervical maturational stage 3 or 4) when applying orthopedic force.
• Patients with good oral hygiene, and a healthy periodontal condition.

Exclusion Criteria:

• Patients who underwent previous orthodontic treatment.
• Patients with previous craniofacial surgeries, chronic diseases, syndromes, or growth problems that may affect bone.
• Any signs or symptoms of para-functional habits or previous history of temporomandibular disorders.
• Extracted or missing upper permanent teeth (except for third molars).