Walkow Todd M, Peck Sheldon
Oral and Developmental Biology (Orthodontics), Harvard School of Dental Medicine, Boston, MA, USA.
Am J Orthod Dentofacial Orthop. 2002 Dec;122(6):608-13. doi: 10.1067/mod.2002.129189.
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.
安氏II类2分类（II/2）错牙合畸形的一种严重表现型，伴有极深的覆牙合，在早期德语描述中被称为覆盖咬合，或“Deckbiss”。这种独特的咬合变异的特征是骨骼面部低角发散、下颌牙牙槽后缩、骨性颏部过度前突、近远中牙体尺寸减小、上颌切牙舌倾，以及至少100%的覆牙合，咬合时至少覆盖1颗下颌切牙。在本研究中，从23例患有II/2覆盖咬合错牙合畸形患者的石膏模型上记录了第一磨牙和尖牙处测量的上颌和下颌牙弓宽度。将这些数据与46例年龄和性别匹配的正畸患者的对照参考样本进行比较。在覆盖咬合组中，两个牙弓的磨牙间宽度和上颌的尖牙间宽度与对照样本相当。然而，II/2覆盖咬合组的下颌尖牙间宽度显著小于对照组（P = 0.01）。这些发现表明，II/2深覆牙合错牙合畸形的特征是上颌和下颌后段的横向尺寸正常且相对协调。本研究确定的下颌从尖牙到尖牙的横向发育不足可能是导致下颌切牙受压和拥挤的原因，这是II/2覆盖咬合深覆牙合的自然后果。因此，对于II/2深覆牙合患者常见的下颌牙牙槽代偿，一个合理的正畸治疗方案通常是扩大下颌牙弓宽度，这通常会减少正畸拔牙的需求，并增加固定保持的可行性。
