الفهرس 
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Abstract
Introduction: Skeletal Class III is considered one of most challenging malocclusions in the children. Maxillary deficiency represents high percentage of skeletal Class III cases. It needs early diagnosis and intervention and long term stability . Purpose: This study was conducted to assess the skeletal , dental and soft-tissue changes of Reverse Twin Block(RTB) with face mask(FM) appliances in early treatment of skeletal Class III malocclusion due to maxillary retrusion. Materials and Methods: A sample of 10 patients (6 boys and 4 girls) in pre-pubertal growth period and an age range from 6-12 years were selected for this study. The patients received Reverse Twin Block(RTB) for two months then attached with face mask(FM) until achieved a positive overjet. A bilateral force of 400g was applied to the maxilla from elastic traction to the face mask appliance. 3D cephalometric measurements were used pre- treatment and after application of RTB and FM to evaluate skeletal ,dental, and soft-tissue effects of the appliances. Data from the 3D cephalometric measurements were analyzed with SPSS version 21 software. Statistical significance was inferred at a P value ≤ 0.005. and highly significant (p ≤ 0.001). Results: Forward maxillary growth as the SNA and ANB angles was increased (p=.005), downward and backward rotation of mandible as the SNB was decreased (p =.033). The maxillary and the mandibular lengths were increased (p=.003). FMA and Sn-Go.Gn angles were increased significantly (p = .022 and p = .023 respectively).On the other hand, total facial heights, anterior and posterior and lower anterior facial height were increased(p = .022 , p = .023 and p <.001 respectively). The upper incisors were tipped labially (U1/SN angle p<.001) and the lower incisors were tipped lingually ( L1/MP angle p=0.004). The Inter-incisal angle U1/L1 was decreased insignificant (p=0.442). The overjet was highly increased (p<.001) also the inter-molar width increased(p=0.029). The upper lip was protruded significantly in relation to E line (p=0.005) while the lower lip was retruded clinically but Statistically was insignificant in relation to E line (p=0.086). Conclusion: Face mask therapy with reverse twin block was effective in early treatment of skeletal Class III malocclusions due to maxillary deficiency and produce skeletal, dental, and soft tissue changes. Skeletal changes were primarily a result of anterior movement of the maxilla, backward and downward rotation of the mandible with increase in the vertical facial dimensions. Dental and soft tissues changes also contributed to the correction of the malocclusion.