Tooth Movements Associated with Deep Overbite Correction of Class II Division 1 and Class II Division 2 Malocclusions in Post-Pubertal Patients Using Continuous Archwire Mechanics

Abstract

The orthodontic profession has assumed much of the responsibility for the improvement of function of the teeth and jaws. Since function is closely associated with overbite, the correction of vertical overbite discrepancies comprises a major part of clinical orthodontics. This investigation was undertaken to describe the movements that teeth undergo during the correction of excessive overbites and to correlate these movements to the change in overbite. A total of 139 cases were selected from the records of the Indiana University School of Dentistry, Department of Orthodontics, including 87 Class II Division 1 and 52 Class II Division 2 cases. The selected cases had an excessive pre-treatment overbite of 4.0 nm or more as seen cephalometrically and a satisfactory post-treatment result. In addition, they were clinically determined to be post-pubertal, indicating essentially no growth potential during the treatment period. Pre and post-treatment tracings of the cephalograrns were made and measurements collected from the tracings. Superimpositions were prepared of the pre and post-treatment radiographs and the general trends that appeared were noted. The change in overbite was correlated to tooth movements in both Class II Division 1 and Class II Division 2 cases using the Pearson test of correlation coefficients. The results indicate that the tooth movements most commonly seen in treatment to reduce excessive overbite occur mainly in the mandibular arch. In Class II Division 1 cases, the change in overbite was significantly correlated to the reduction in vertical height of the mandibular incisor and to the increase in the angulation of the mandibular incisor to the mandibular plane. In Class II Division 2 cases, the change in overbite was significantly correlated to the increase in vertical height of the mandibular molar, decrease in the vertical height of the mandibular incisor, increase in angulation of the mandibular incisor to the mandibular plane and increase in the angle formed by the occlusal and mandibular planes. Not all measurements recorded were significantly correlated to the change in overbite. However, it should be noted that the findings of this study describe a group, that a great deal of individual variation exists, and that are factors which do not show any statistical significance for the group may have an effect in isolated cases.