title: Effects of early activator treatment in patients with class II malocclusion evaluated by thin-plate spline analysis.
abstract: The aim of the present longitudinal cephalometric study was to evaluate the dentofacial shape changes induced by activator treatment between 9.5 and 11.5 years in male Class II patients. For a rigorous morphometric analysis, a thin-plate spline analysis was performed to assess and visualize dental and skeletal craniofacial changes. Twenty male patients with a skeletal Class II malrelationship and increased overjet who had been treated at the University of Heidelberg with a modified Andresen-Häupl-type activator were compared with a control group of 15 untreated male subjects of the Belfast Growth Study. The shape changes for each group were visualized on thin-plate splines with one spline comprising all 13 landmarks to show all the craniofacial shape changes, including skeletal and dento-alveolar reactions, and a second spline based on 7 landmarks to visualize only the skeletal changes. In the activator group, the grid deformation of the total spline pointed to a strong activator-induced reduction of the overjet that was caused both by a tipping of the incisors and by a moderation of sagittal discrepancies, particularly a slight advancement of the mandible. In contrast with this, in the control group, only slight localized shape changes could be detected. Both in the 7- and 13-landmark configurations, the shape changes between the groups differed significantly at P < .001. In the present study, the morphometric approach of thin-plate spline analysis turned out to be a useful morphometric supplement to conventional cephalometrics because the complex patterns of shape change could be suggestively visualized.
authors: Department of Orthodontics, University of Heidelberg, Germany. christopher_lux@med.uni-heidelberg.de
authors: C J
authors: CJ
authors: Lux
authors: J
authors: J
authors: Rübel
authors: J
authors: J
authors: Starke
authors: C
authors: C
authors: Conradt
authors: P A
authors: PA
authors: Stellzig
authors: P G
authors: PG
authors: Komposch
mesh_terms: D000202:Activator Appliances; D000539:Alveolar Process / Q000473:pathology; D002508:Cephalometry / Q000379:methods*; D002648:Child; D005147:Facial Bones / Q000473:pathology; D005500:Follow-Up Studies; D006801:Humans; D007180:Incisor / Q000473:pathology; D008137:Longitudinal Studies; D008297:Male; D008312:Malocclusion, Angle Class II / Q000473:pathology / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D016382:Orthodontic Appliance Design; D018709:Statistics, Nonparametric; D014070:Tooth / Q000473:pathology; D016896:Treatment Outcome