Cephalometric evaluation of symmetric and asymmetric extraction treatment for patients with Class II subdivision malocclusions.Am J Orthod Dentofacial Orthop. 2007 Jul; 132(1):28-35.AJ
The purpose of this study was to cephalometrically compare the dentoskeletal and soft-tissue changes consequent to orthodontic treatment in patients with Class II subdivision malocclusion treated with asymmetric and symmetric extractions.
The sample included 54 patients with Class II subdivision malocclusion and full complement of permanent teeth, including first molars, at the beginning of treatment. Patients in group 1 (n = 27) were treated with the asymmetric extraction of 3 premolars and had initial and final mean ages of 14.07 and 16.71 years. Patients in group 2 (n = 27) were treated with the symmetric extraction of 4 premolars and had initial and final mean ages of 13.35 and 15.75 years. Lateral cephalometric radiographs were taken at pretreatment and posttreatment. T tests were used to compare the groups at pretreatment and the treatment changes between groups.
The results demonstrated that the asymmetric extraction group had significantly less mandibular incisor retraction, less soft-tissue retraction, and greater increases in mandibular incisor extrusion and mandibular molar asymmetry index than the symmetric extraction group.
It was concluded that the 3-premolar asymmetric extraction protocol in Class II subdivision malocclusions produces significantly less mandibular incisor and soft-tissue retraction than the 4-premolar extraction protocol.