title: Association between Björk's structural signs of mandibular growth rotation and skeletofacial morphology.
abstract: The aim of this study was to apply Björk's structural signs of mandibular growth rotation to answer the questions: (1) Is a hyperdivergent or hypodivergent skeletofacial growth pattern characterized by a specific mandibular morphology? (2) Are severe skeletofacial hyperor hypodivergencies recognized more easily than mild ones? (3) Are skeletofacial hyper- or hypodivergencies recognized more easily in older than in younger subjects? Mandibular cuttings from lateral head films of 135 Class I or Class II subjects were surveyed twice by nine observers. Of the 135 subjects, 95 subjects exhibited a large (ML/NSL > 38 degrees) and 40 a small (ML/NSL < 26 degrees) mandibular plane angle. Using the structural signs of mandibular growth rotation, the observers had to categorize the subjects as having either a high-angle or low-angle skeletofacial morphology. In 14% (13 of 95) of the subjects with a large ML/NSL angle, the skeletofacial hyperdivergency was recognized in all registrations, but in 19% (18 of 95), the hyperdivergency was identified in less than half of the registrations. In 63% (25 of 40) of the subjects with a small ML/NSL angle, the skeletofacial hypodivergency was recognized in all registrations, whereas in only 2.5% (one of 40), the hypodivergency was identified in less than half of the registrations. There was no association between the degree of hypo- or hyperdivergency or the age of the subjects and the number of correct registrations. Using the structural method of Björk, it was difficult to categorize the subjects as having either a hyperor hypodivergent skeletofacial morphology. However, hypodivergency was recognized more easily than hyperdivergency.
authors.affiliation: Department of Orthodontics, University of Giessen, Giessen, Germany. Julia.v.bremen@dentist.med.uni-giessen.de
authors.forename: Julia
authors.initials: J
authors.lastname: von Bremen
authors.forename: Hans
authors.initials: H
authors.lastname: Pancherz
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002508:Cephalometry; D002648:Child; D005147:Facial Bones / Q000033:anatomy & histology*; D005544:Forecasting; D006801:Humans; D007574:Jaw Relation Record; D008310:Malocclusion / Q000503:physiopathology*; D008334:Mandible / Q000254:growth & development*; D012015:Reference Standards