71 - Dentoskeletal effects of digital cast herbst+hyrax appliance in the treatment of a Class II/1 malocclusion: A case report

Abstract

Herbst appliance is a fixed functional appliance used in the treatment of skeletal Class II anomaly. This case report presents the skeletal and dental changes achieved using a digital cast Herbst appliance combined with hyrax screw in the treatment of a 15-year-old male patient with skeletal Class II anomaly. The growing male patient (mp3u) has skeletal Class II anomaly with maxillary prognathism (SNA:86°, SNB:80°), low angle pattern (SNGoGn:25°), Class II Division 1 malocclusion, 8mm overjet and 2.5 mm maxillary crowding. The digital oral scanning was done by iTero^Ⓡ and on 3D models, digital cast of the combined Hyrax+Herbst appliance was designed. The digital cast Herbst appliance was used with a total duration of 7 months. The hyrax screw was activated 2 months; twice (0.25 mm per turn) weekly in the first, once weekly in the second month, for a total of 12 turns. During the treatment the appliance was well tolerated. After treatment, significant improvement was observed in convex facial profile, SNA angle decreased to 82°, SNB angle to 78°, mild posterior rotation occurred (SNGoGn:28°) and the molar relationship was corrected to bilateral Class I. Maxillary incisors demonstrated notable retrusion and 1-NB increased from 4 mm to 6 mm, reflecting minor proclination. The 3 mm activation of the expansion screw translated into an approximate 2 mm increase in transverse arch width. This reduced maxillary crowding from 2.5 mm to 0.5 mm. The retrusion of maxillary incisors and maxilla was favorable for this patient that may contributed to the combined application of the Hyrax and the Herbst. Whereas no mandibular advancement had occurred which may attribute to the mandibular posterior rotation. As a conclusion, expansion combined with Herbst treatment is suitable for the patients with skeletal Class II anomaly due to maxillary protrusion with low angle tendency and maxillary incisor protrusion.