Nonsurgical and nonextraction treatment of skeletal Class III open bite: Its long-term stability

Abstract

Two female patients, aged 14 years 5 months and 17 years 3 months with skeletal Class III open bite and temporomandibular dysfunction are presented. They had previously been classified as orthognathic surgical cases, involving first premolar removal. The primary treatment objective was to eliminate those skeletal and neuromuscular factors that were dominant in establishing their malocclusions. These included abnormal behavior of the tongue with short labial and lingual frenula, bilateral imbalance of chewing muscles, a partially blocked nasopharyngeal airway causing extrusion of the molars, with rotation of the mandible and narrowing of the maxillary arch. Resultant occlusal interference caused the mandible to shift to one side, which in turn produced the abnormal occlusal plane and curve of Spee. As a result, the form and function of the joints were adversely affected by the structural and functional asymmetry. These cases were treated by expanding the maxillary arch, which brought the maxilla downward and forward. The mandible moved downward and backward, with a slight increase in anterior facial height. Intruding and uprighting the posterior teeth, combined with a maxillary protraction, reconstructed the occlusal plane. A favorable perioral environment was created with widened tongue space in order to produce an adequate airway. Myofunctional therapy after lingual and labial frenectomy was assisted by vigorous gum chewing during and after treatment, together with a tooth positioner. Normal nasal breathing was achieved. (Am J Orthod Dentofacial Orthop 2000;117:267-87)