Stability of early Class III orthopedic treatment

The objective of the article is to determine the stability of early Class III orthopedic treatment in the primary and early mixed dentitions. A total of 23 patients with Class III malocclusion in the primary or early mixed dentition (mean age = 6.2 ±1.5 years, CVM = 1) were treated consecutively by one of the investigators (T.K.) using maxillary expansion and protraction appliances. The average treatment time was 9.1 ± 2.3 months. For each patient, a lateral cephalogram was taken at pre-treatment (T1), post-treatment (T2), and 2 years post-treatment (T3). Each patient served as his/her own control. Cephalometric analysis described by Bjork (1947) and Pancherz (1982) was used. Sagittal and vertical measurements were made along the occlusal plane (OLs) and the occlusal plane perpendicular (Olp), and superimposed on the mid-sagittal cranial structure. Data were analyzed using paired t-test. All patients in the study were treated to Class I or overcorrected to Class II dental arch relationships. Overjet and sagittal molar relationships improved by an average of 4.1 and 1.8 mm, respectively (T2–T1). This was a result of 2.6 mm of forward maxillary growth, .7 mm of forward mandibular growth, 1.2 mm of labial movement of maxillary incisors, 1.0 mm of lingual movement of mandibular incisors, and .1 mm of greater mesial movement of mandibular than maxillary molars. The mean overbite reduction was .9 mm. The maxillary and the mandibular molars were erupted occlusally by 1.5 and 1.0 mm, respectively. The mandibular plane angle was increased by .9° and the lower facial height by 3.2 mm. Overall, 2 years follow-up observation (T3–T2) revealed a decrease in the overjet and the molar relationship by .3 and .2 mm, respectively. This was contributed by 2.2 mm of excess forward mandibular growth that was compensated by 1.9-mm dentoalveolar compensation. Overall, the changes in the overjet and the molar relationship were 3.8 and 1.5 mm, respectively. The overbite reduction was .6 mm. Significant overjet and overbite corrections can be obtained with maxillary protraction in the primary or early mixed dentition. Overjet and molar relationship corrections were stable 2 years post-treatment. A combination of dentoalveolar compensation and skeletal changes accounted for this stability.