This experimental study aims to evaluate the efficiency of the Modified Fixed Mandibular Retractor Appliance in the treatment of skeletal class III malocclusion.

The study sample will consist of 44 patients with skeletal class III malocclusion. The sample will be allocated randomly into two groups: experimental group and untreated control group.

The soft and hard tissue changes will be assessed using lateral cephalometric radiographs before the treatment and after obtaining 3mm positive overjet.

This research aimes to evaluate the effects of a Class III functional appliance [the modified fixed mandibular retractor (MFMR)] in the early treatment of skeletal Class III deformities.

It was not ethical to expose all candidate children to radiographic examination. Therefore, the assessment of skeletal Class III malocclusion was based on clinical judgment. Each patient was examined, while his/her mandible was kept at its retruded contact position to evaluate both jaws in space. Those who met the inclusion criteria were then sent to the radiographic department.

The radiographic lateral cephalograms were obtained in the patients' habitual occlusion.

All patients in the treatment group were treated by one specialist orthodontist 'AA' using the MFMR. The appliance consisted of the following elements: (1) Two acrylic upper posterior bite planes which cover the deciduous and permanent molars ( 2) Two transpalatal arch (0.8-mm TMA) with opposite U loop, the anterior one is near the first deciduous molars while the posterior one is near the first permanent molars (3) upper reversed labial bow (0.9-mm stainless steel) extending to the cervical edges of the mandibular anterior teeth from the labial surface of the lower primary canine on one side to the other labial surface of the contralateral tooth. This bow will be activated to hold the mandible in its maximum posterior physiologic position; and (4) the anterior spring (0.8-mm TMA) which starts from the acrylic bite plane in both sides, makes loop, then bends to touch the cingulum of upper incisors to procline the upper permanent incisors when diagnosed as retroclined.

The untreated group will receive no orthodontic treatment during the observation period. According to the Dental School Local Research Ethics Committee's guidelines, all children in the untreated group will receive orthodontic treatment after the end of the observational period of the study at no cost.

Inclusion Criteria:

• Patients in early mixed dentation (7-9 years old).
• Skeletal class III caused by mandibular prognathism with or without maxillary deficiency judged clinically and confirmed radiographically (ANB≤1).
• Anterior crossbite on two teeth or more.
• Normal inclination of the lower incisors with the mandibular plane.
• Good oral hygiene.

Exclusion Criteria:

• Poor oral hygiene.
• Previous orthodontic treatment.
• Patients with syndromes, clefts, or craniofacial abnormalities.
• Severe skeletal class III resulting primarily from mandibular prognathism (ANB less than - 4 with no functional shift on closure)
• Patients with facial asymmetry.
• Patients with vertical growth pattern.

The Individual participant data will be only available for the researchers in the department of Orthodontics, Damascus University

A person who is not related to the research will paste a piece of paper over the Patient's name and the date of the photo then will give each x-ray a code and blind these codes on the researcher during the assessing process.