Stability of open bite treatment.

Is early orthodontic treatment indicated for anterior open bite malocclusions? Is the stability of open bite treatment a significant clinical problem? To answer these questions, I would like to define open bite as the lack of overlap of the anterior teeth in centric occlusion. Overlap pertains to the incisal edges as viewed from the anterior; the mandibular incisors do not contact any opposing structures, such as the maxillary incisors or the palate. Some use the term open bite tendency as a synonym for overlap. Contact occurs when the anterior and posterior teeth touch opposing structures in centric occlusion. In a soon-to-be published review article on the stability of open bite treatment, Huang searched the English language literature for studies with reasonable methodologies, sample sizes, and follow-up periods. He found 6 that evaluated open bite stability in nonsurgical patients and 15 that evaluated it in orthognathic surgical patients. Obviously, relatively few scientific studies have evaluated stability of open bite treatment. Lopez-Gavito et al evaluated the cephalometric radiographs of 41 patients (29 females, 12 males) pretreatment, immediately posttreatment, and 10 years postretention. At the beginning of treatment, they were adolescents in the permanent dentition who had a Class I or II malocclusion. Each had an open bite of at least 3 mm measured along the long axis of the mandibular incisors. They were treated conventionally with fixed appliances, headgear, and elastics. In the long term, 35% of the patients had an open bite of 3 mm or more, and 65% had relatively stable results. Because of concerns that the measurement of the open bites in this study was unduly influenced by the angular and anteroposterior position of the mandibular incisor, the study was redone a few years later by Zuroff. He expanded the sample and subdivided the subjects into 3 groups: a contact group of 24 with an average overbite of 4.79 mm, an overlap group of 25 with an average overlap of 1.80 mm, and an open bite group with an average overlap of 2.23 mm. The overbite measurement was made relative to the nasion-menton line. At 10 years postretention, 60% of the open bite subjects did not have incisor contact. On the other hand, in the entire sample of 64, the largest vertical relapse was 2.4 mm, and no one had negative incisor overlap. In the subjects who showed instability of overbite correction, the mandibular incisors failed to erupt vertically as they continued to move lingually (with increasing crowding). As with Lopez-Gavito’s study, analysis of pretreatment records did not allow stability or instability to be predicted in the treatment result. Katsaros and Berg evaluated 20 patients who had pretreatment open bites as determined from plaster casts. The open bite, measured perpendicular to the nasion-menton line, was an average of 1.9 mm. Nineteen of the patients were treated with edgewise appliances and 1 with a functional appliance. They were evaluated at least 1 year posttreatment. The criterion for successful treatment was the presence of occlusal contacts of at least 2 incisors in habitual occlusion or after forward sliding of the lower cast. On that basis, 15 of 20 patients (75%) were treated successfully. Huang et al studied the stability of crib therapy in open bite patients. The sample included 26 growing and 7 nongrowing patients who were evaluated cephalometrically before treatment, at the end of treatment, and at least a year posttreatment. Before treatment, the average negative overbite, measured relative to the nasion-menton line, was 2.8 mm. The overall success rate for achieving a positive overbite was 88%. All patients who achieved a positive overbite during treatment maintained it during the follow-up period. It is helpful to compare the stability seen in nongrowing open bite patients treated surgically with that of open bite treatment in children, to give some perspective. Denison et al evaluated 66 patients who had undergone LeFort I osteotomies to decrease facial Clinical professor, Department of Orthodontics, University of Washington, Seattle. Presented at the International Symposium on Early Orthodontic Treatment, February 8-10, 2002; Phoenix, Ariz. Am J Orthod Dentofacial Orthop 2002;121:566-8 Copyright © 2002 by the American Association of Orthodontists. 0889-5406/2002/$35.00 0 8/1/124175 doi:10.1067/mod.2002.124175