American Board of Orthodontics (ABO) Practice Exam 2025 – All-in-One Resource to Master Your Orthodontics Certification!

The functional appliances that are effective in increasing the SNB angle, which represents the angle formed between the Sella (S), Nasion (N), and Gonion (B), are those that facilitate the forward positioning of the mandible. The Herbst, MARA, and Twin Block appliances are specifically designed to promote mandibular growth by encouraging the lower jaw's anterior movement and enhancing the relationship between the maxilla and mandible.

The Herbst appliance works by attaching to both the maxillary and mandibular teeth, allowing for continuous forward positioning of the mandible during functional activities like chewing, which in turn stimulates growth at the condyle and increases the SNB angle.

The MARA (Mandibular Anterior Repositioning Appliance) similarly encourages forward positioning of the mandible, enhancing the growth potential and relationship of the jaw, thus leading to an increase in the SNB angle as well.

The Twin Block appliance is designed with two separate functional blocks to differentially position the maxilla and mandible, promoting a more favorable occlusion and increasing the SNB angle through its influence on jaw posture and growth.

These appliances act effectively to correct Class II relationships and improve functional occlusion, which is critical in orthodontic treatment planning. Understanding their function helps