Three-Dimensional Evaluation Of The Changes In Glenoid Fossa And The Mandible In Children With Class III Malocclusion Using Modified Reverse Twin Block Appliance

Class III malocclusion represents a complex three dimensional facial skeletal imbalance between maxillary and mandibular growth along with varying degrees of dentoalveolar and soft tissue compensations. Various interceptive orthodontic treatments for class III malocclusion include facemask, reverse twin block, tandem traction bow appliance , skeletal anchorage system and chin cup.

The Reverse Twin Block has proven to be a simple, comfortable, well tolerated and eflicient functional appliance for the correction of developing Class III malocclusions during mixed dentition. However, the eflects of this appliance are primarily limited to the dentition. Skeletal changes are limited to slight downward and backward rotation of the mandible. Another treatment modality for class malocclusion is the Bone Anchored Maxillary Protraction (BAMP), but the surgical intervention for the placement of miniplates makes the patient apprehensive.

To overcome these disadvantages a modification of the conventional Reverse Twin Block was designed combining the following principles BAMP

HYRAX

FACEMASK

REVERSE TWIN BLOCK

In the modified design of the reverse twin block appliance, along with upper and lower bite blocks of conventional reverse twin block appliance, several other components are added

Rapid Maxillary Expansion Device (Hyrax Screw) Hooks placed in the upper molar region in the upper bite block and in between the lateral incisor and canine, in the lower bite block.

Intra-oral elastics are used engaging both the hooks on either side. (The force applied passes through the Centre of Resistance of Maxilla and is at 30 degrees to the occlusal plane).

Various studies have shown changes in the TMJ following chincup. BoneAnchored Maxillary Protraction |BAMP), Facemask therapy.

Though TMJ can be visualized in 2D cephalometry, superimpositions have some limitations with respect to accuracy and reliability and superimposition on 3D images have been used to provide more reliable infornation.

To date, however, there is a lack of knowledge on the changes occumring in the mandible and glenoid fossa following the conventional or modified reverse twin block therapy Hence, in this study we sought to evaluate the effects of the modified reverse twin block appliance on the mandible and the glenoid fossa in class III subjects using Cone Beam Computed Tomography.

15 children with class III malocclusion in the age group of 10-13 years reporting to the Out Patient Department of the Department of Pediatric and Preventive Dentistry at A B Shetty Institute of Dental Sciences, Deralakatte will be included in the study.

A detailed case history, clinical examination and cephalometric analysis will be done to confirm the skeletal pattern of the patient.

child before the commencement of the study. Pre-operative CBCT will be taken before delivering the Modified reverse twin block appliance. All instructions regarding the appliance like changing of the intermaxillary elastics daily and the activation of the screw will be given to the patient. follow up CBCT will be recorded after 12-14 months of appliance wear. Data will be collected and statistically analyzed.