Post-Retention Changes in Maxillary Molar Position Following Cervical Traction

Objective: Determine what results are produced with early cervical traction on maxillary molar sagittal position and associated midface skeletal changes, and stability of these changes post-retention as compared to growth changes of a control normal occlusion sample matched for age and time. Methods: Cephalometric data was collected from 56 hyperdivergent ClassII Div1 patients prior to treatment with cervical pull headgear (T1), at the time of retention (T2) and at an average of 18 months following removal of all retention (T3). Interjaw or “B” angle was used to determine hyperdivergency, indicated when “B” angle was greater than one standard deviation from standard norms. Twelve angular linear and proportional dimensions were acquired for each patient at each time interval. Measurements were compared with 58 neutral occlusions of same age level at the same three periods studied to evaluate if any differences occurred relative to maxillary molar position in relation to skeletal components. Results: Following treatment, convexity was reduced without a significant increase in facial angle as compared to neutral occlusions. “B” angle was balanced due to flattening of palatal plane angle (PPL) and an increase in mandibular plane angle (MPL). Linear and proportional Maxillary length (Ptm-A) was reduced during treatment, and both anterior (NM) and posterior (Pns-Go) face heights increased. Maxillary molar was distalized into Class I molar relationship. During post-retention period, PPL and MPL relapsed without disrupting the B angle. Facial angle increased, but remained lower than neutral measurements. Maxillary length and midface depth (BaN) experienced growth after discontinued therapy. Maxillary molar showed mesial drift post-retention, but remained in ClassI molar relationship despite relapse. Conclusion: Anterior posterior correction was accomplished and maintained post-retention both skeletally with a reduction in convexity of 2mm without a greater increase in facial angle and a 1mm more posterior location of maxillary molar.