Treatment of Class III Malocclusion Using Modified Fixed Mandibular Retractor Appliance

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Evaluation of the Efficacy of Modified Fixed Mandibular Retractor Appliance in the Treatment of Class III Malocclusion: A Clinical Randomized Controlled Trial

Conditions
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Malocclusion, Angle Class III

Intervention / Treatment
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* Device: Modified Fixed Mandibular Retractor Appliance


Participation Criteria
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Eligibility Criteria
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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.

Ages Eligible for Study
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Minimum Age: 7 Years
Maximum Age: 9 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Modified Fixed Mandibular Retractor<br>All patients in this group will be treated using Modified Fixed Mandibular Retractor Appliance. This appliance will be used full-time. | Device: Modified Fixed Mandibular Retractor Appliance<br>* All patients with Class III malocclusion will be treated using the Modified Fixed Mandibular Retractor Appliance<br>|
| No Intervention: Untreated control group<br>All patients in this group will be observed during the period of treating the patients in the other group to assess the growth changes. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| ANB angle changes | ANB angle changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SNA angle changes | SNA angle changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 
| SNB angle changes | SNB angle changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 
| Profile changes | Profile changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 
| Upper incisor angle changes | Upper incisor angle changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 
| Lower incisor angle changes | Lower incisor angle changes before and after treatment will be assessed and compared with those of the control group using lateral cephalometric radiographs. | Changes will be evaluated before treatment and after obtaining 3mm positive overjet, which will take approximately 8 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Class III treatment, Modified Fixed Mandibular Retractor Appliance, RCT