Department of Orthodontics, Field of Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Angle Orthod. 2013 Jan;83(1):36-42. doi: 10.2319/042412-341.1. Epub 2012 Aug 16.
To determine the root-crown (R/C) ratio and dental root length of teeth in patients with open bite and seek any relationships with occlusal contact (OC) and the mandibular plane (Mp) angle.
Thirty-one patients with open bite with negative overbite of at least four anterior teeth and 31 control patients with clinically normal overjet and overbite were enrolled. R/C ratios, dental root length, OC, and Mp angle were measured using panoramic radiographs, dental casts, and cephalograms, respectively. Mean differences between the groups, and variations between the R/C ratio or root length and Mp angle in patients with open bite were statistically analyzed.
R/C and OC ratios from the incisors to premolars were significantly lower for patients with open bite than for controls, and some teeth had short dental roots. Relationships between low R/C ratio or root length and high Mp angle were significant in patients with open bite.
Patients with open bite, especially those with a high Mp angle, have an unfavorable R/C ratio and short dental roots in some teeth, which may be related to the loss of OC.
确定反颌患者的根冠比和牙齿根长，并探讨其与咬合接触（occlusal contact，OC）和下颌平面（mandibular plane，Mp）角度的关系。
选取 31 例反颌伴至少 4 颗前牙覆颌为负的患者和 31 例具有临床正常覆颌和覆盖的对照组患者。分别使用全景片、牙模和头颅侧位片测量根冠比、牙齿根长、OC 和 Mp 角度。采用独立样本 t 检验比较两组间的差异，分析反颌患者根冠比或根长与 Mp 角度之间的变化。
反颌患者的切牙至前磨牙的根冠比和 OC 比值明显低于对照组，部分牙齿的根较短。反颌患者中，低根冠比或根长与高 Mp 角度之间存在显著相关性。
反颌患者，尤其是高 Mp 角度的患者，在一些牙齿中存在不利的根冠比和较短的牙齿根长，这可能与 OC 的丧失有关。
