Three-dimensional skeletal mandibular changes associated with Herbst appliance treatment

Area of Science:

• Orthodontics and Dentofacial Orthopedics
• Craniofacial Biology
• Biomedical Imaging

Background:

• Class II malocclusion often involves mandibular retrognathism.
• Orthopedic correction aims to reposition the mandible and improve facial aesthetics.
• Three-dimensional imaging provides precise assessment of skeletal changes.

Purpose of the Study:

• To quantitatively evaluate three-dimensional skeletal mandibular changes after Herbst appliance treatment.
• To compare mandibular growth and displacement in patients treated with the Herbst appliance versus a control group.

Main Methods:

• Retrospective case-control study with 25 patients in the Herbst appliance group (HAG) and 25 in the control group (CG).
• Cone beam computed tomography (CBCT) scans were used for pre-treatment (T0) and post-treatment (T1) 3D model generation.
• Volumetric registration techniques assessed mandibular displacement and growth, with quantitative and qualitative analyses.

Main Results:

• The Herbst appliance group (HAG) showed significant forward mandibular displacement (1.7 mm) compared to the control group (CG).
• Both groups exhibited downward mandibular displacement, more pronounced in HAG (2.4 mm) than CG (1.5 mm).
• HAG demonstrated significantly greater superior and posterior condylar growth (3.5 mm and 2.0 mm, respectively) and posterior ramus growth than CG.

Conclusions:

• Herbst appliance therapy effectively achieves significant forward mandibular displacement through enhanced bone remodeling.
• The treatment induces greater condylar and ramus growth compared to non-orthopedic dental treatments.
• Three-dimensional analysis reveals specific changes in the direction and magnitude of condylar growth following Herbst treatment.