Effects of patient age and sex on treatment: correction of Class II malocclusion with the Begg technique.

When children are treated orthodontically during a phase of active growth-notably adolescence-there is the opportunity to harness growth to achieve some of the correction, especially in the sagittal plane in which differential jaw growth can harmonize dental relationships. All correction must be from tooth movement when there is no growth. Three questions were addressed in the present study: (1) how much orthodontic correction is achieved by bone growth? (2) do the proportions of tooth and bone movement depend on patient age? and (3) do the jaws of boys and girls grow at discernibly different rates during treatment? A sample of 139 children aged 9 to 17 years at the start of treatment with Class II division 1 malocclusions was studied cephalometrically using Johnston analysis. Maxillary and mandibular growth were highest in the youngest children, with rates decreasing to effectively zero in the oldest adolescents. Means adjusted for age were significantly higher for boys than for girls for upper and lower jaw growth. Age had little influence on the amount of tooth movement except for a marked decline with age in the mesial movement of the maxillary first molar, which was greatest in the youngest patients of both sexes. The amount of orthodontic correction was independent of age, but in the youngest quartile of the sample, most of the correction (87%) was due to differential jaw growth in the youngest quartile of the sample, and the rest (13%) resulted from tooth movement, whereas in the oldest quartile, most of the correction was due to tooth movement (64% tooth movement and 36% bone growth). Overall, the influence of age and sex had significant influences on multiple skeletodental variables, suggesting that research designs need to account for these demographic sources of variability. Although all cases were treated to a Class I occlusion, the nature of the correction was affected measurably by the patient's age and sex.