Indications for Mandibular Setback

The word prognathism—class III dysgnathia, mandibular prognathism, class III malocclusion—is derived from Greek πρό (pro, “forward”) and γνάθος (gnáthos, “jaw”). Clinical symptoms can be very diverse. They include anterior cross- and headbites, unilateral or bilateral crossbites of various degrees, upper jaw crowding, but also incomplete upper jaw dentitions, compensatory extraverted upper jaw fronts, as well as compensated inverted lower incisors. Furthermore, it must be differentiated whether the respective class III is a forward displacement of the mandible or a backward displacement of the maxilla or a combination of both symptoms. Prognathism can be treated at different ages and stages of development. Depending on this, different therapeutic means can be used, often only with the support of orthognathic surgery. Common to all these means of treatment is that they are visible to the patient’s social environment. Non-treatment may remain a limitation in daily life (Severt and Proffit Int J Adult Orthodon Orthoganthic Surg 12:171–176, 1997). Skeletal class III malocclusion is a widespread, mostly genetically determined malocclusion that can be explained by a growth excess in the mandible and/or growth deficit in the maxilla/midface. A concave facial profile with protruding chin is the result. The prevalence of class III malocclusion varies greatly both among and within populations, and the highest prevalence has been observed in Southeast Asian populations. In pronounced form, biting off food is impossible and the functional range of the temporomandibular joints is limited. This is the functional indication for therapy. The only true option for correction in skeletal class III is surgical. In addition to the BSSO, the inverted L osteotomy and the intraoral vertical ramus osteotomy (IVRO) can also be used (Bell et al. Surgical correction of dentofacial deformities 2:890–895, 1980).