Fixed Versus Conventional Twin Block Appliances for Skeletal Class II Malocclusion

Overview

This study compares two types of dental appliances a fixed Twin Block appliance and a conventional (removable) Twin Block appliance used to treat a bite problem called skeletal Class II malocclusion in growing children and teenagers. In this condition, the lower jaw is positioned further back than the upper jaw. Both appliance types work by guiding the lower jaw forward during growth. The study uses 3D imaging (cone beam computed tomography, or CBCT) before and after treatment to measure how each appliance affects the bones of the jaw, the teeth, the soft tissue profile of the face, and the jaw joint (temporomandibular joint). The goal is to determine whether the fixed or the conventional version of the appliance produces better treatment outcomes.

This comparative clinical study evaluates the skeletal, dentoalveolar, soft-tissue, and condylar/temporomandibular joint (TMJ) effects of fixed versus conventional Twin Block appliances in growing patients diagnosed with skeletal Class II malocclusion due to mandibular retrognathia. Participants were allocated to receive treatment with either a fixed or a conventional (removable) Twin Block appliance. Pre-treatment and post-treatment cone beam computed tomography (CBCT) scans were obtained to assess sagittal jaw relationships, mandibular advancement, dentoalveolar changes (including overjet and overbite correction), soft-tissue profile changes, and condylar position/remodeling within the glenoid fossa, including TMJ disc space measurements. Outcomes between the two appliance groups were compared to evaluate differences in skeletal and dental effects, as well as any differences in condylar/TMJ adaptation associated with each appliance design.