Cephalometric Evaluation of a Clear Mandibular Advancement Appliance Based on the Twin-block Design

A Clear mandibular advancement appliance is constructed comprised of a clear dental splint of 1.5 mm thickness adapted on the patient's teeth. This is followed by the construction of acrylic bite ramps bonded over the splints. The bite ramps are constructed as such when the patient bites into occlusion, he/she has to advance the mandible to bring the two parts of the appliance together. Lateral cephalometric radiographs were obtained pre and post-treatment to evaluate the effects on the patient's maxilla, mandible and dentition.

Inclusion criteria

• Gender: Female subjects.
• Chronological age: All recruited subjects were between the ages of 8-12 years.
• Anteroposterior skeletal relationship: Subjects with skeletal Class II malocclusion with normal maxilla and retrognathic mandible were selected. This was confirmed using lateral cephalometric radiographic analysis with the following parameters: decreased effective mandibular length (Co-Gn) according to McNamara composite , SNB<78, SNA=82+2.
• Dental characteristics:

• Angle Class II molar relationship ranging from edge to edge to full unit Class II.
• Overjet ranging between 5-10 mm.
• Absence of posterior crossbite and/or tendency for posterior crossbite.
• Skeletal maturation stage: The growth stage for all subjects was selected to be before or at the prepubertal growth spurt. This was confirmed by cervical vertebral maturation analysis from the lateral cephalometric radiograph. The cervical vertebrae maturation stage required was Cervical Vertebrae Maturation stage 2-3 according to the cervical vertebrae maturation index by Baccetti et al. allowing sufficient time before the end of the growth spurt.
• No previous history of orthodontic treatment.
• Absence of systemic diseases affecting growth or craniofacial development. -

Exclusion criteria

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