Dental arch width in Class II Division 2 deep-bite malocclusion.

A severe phenotype of Angle's Class II Division 2 (II/2) malocclusion with extremely deep overbite has been called cover-bite, or "Deckbiss" in its early German descriptions. This distinctive occlusal variation is characterized by skeletofacial hypodivergence, mandibular dentoalveolar retrusion, excessive bony chin projection, reduced mesiodistal tooth size, maxillary incisor retroclination, and at least 100% overbite, covering at least 1 mandibular incisor in occlusion. In this study, maxillary and mandibular dental arch widths measured at the first molars and the canines were recorded from dental casts of 23 subjects with II/2 cover-bite malocclusions. The data were compared with a control-reference sample of 46 orthodontic patients matched for age and gender. In the cover-bite group, the intermolar widths in both arches and the intercanine width in the maxilla were comparable with those in the control sample. However, mandibular intercanine width in the II/2 cover-bite group was significantly less than that of the controls (P =.01). These findings suggest that II/2 deep overbite malocclusion is characterized by normalized and relatively compatible transverse dimensions in the maxilla and in the mandibular posterior segments. The transverse underdevelopment that this study identified in the mandible from canine to canine is probably responsible for mandibular incisor compression and crowding--natural sequelae of the deep overbite in II/2 cover-bite. Thus, a reasonable orthodontic treatment plan for the mandibular dentoalveolar compensation often seen in II/2 deep-bite patients would be anterior expansion of the mandibular arch width, usually reducing the need for orthodontic tooth extractions and increasing the desirability of fixed retention.