The effects of maxillary protraction in the treatment of skeletal class Ⅲ malocclusion of different skeletal maturation groups / 实用口腔医学杂志

ABSTRACT

Objective: To investigate hard tissue changes produced by maxillary protraction in patients with skeletal Class III malocclusion at different bone age,and to determine the relationship between the effect of maxillary protraction and bone age.Methods:75 subjects of skeletal Class III malocclusion with retruded maxilla were treated by maxillary protraction and rapid maxillary expansion for 6 months.Cephalometric radiographs were taken before and after treatment.The bone age of individual patients was assessed using cephalometric radiographs at the initiation of treatment on the basis of cervical vertebrace maturation indicators(CVMI).Patients were divided into three groups:Prepubertal growth peak group (CVMI Ⅰ-Ⅱ,8.2-11.3 years old), pubertal growth peak group (CVMI Ⅲ,10.2-12.3 yeasr old), and postpubertal growth peak group (CVMI Ⅳ-Ⅵ,11.5-14.5 years old).Results:(1)There was no difference in the maxillary advancement after maxillary protraction between the prepubertal growth peak and the pubertal growth peak groups;(2) in the postpubertal growth peak group, there was a decrease in maxillary skeletal advancement, whereas the dentoalveolar advancement was increased; (3) the posteroinferior rotation of mandible, the increase of lower facial height, and the eruption of maxillary molars showed no correlation with bone age.Conclusion:The importance of performing a biologic evaluation of bone age in the diagnosis and treatment planning of skeletal Class III malocclusions in individual patients must be emphasized.