Gu Yongchun, Wang Wei, Ni Longxing
Department of Stomatology, First People's Hospital of Wujiang District, Nantong University, Suzhou, China; State Key Laboratory of Military Stomatology, Department of Endodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
State Key Laboratory of Military Stomatology, Department of Endodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
Arch Oral Biol. 2015 Jun;60(6):811-7. doi: 10.1016/j.archoralbio.2015.02.024. Epub 2015 Mar 3.
To detect the incidence and anatomic features of 4-rooted permanent maxillary molars in a northwestern Chinese population by using cone-beam computed tomography (CBCT).
A total of 725 Chinese patients with well-developed maxillary permanent first and/or second molars were examined by using CBCT. The number of roots and canals, shape, location, and division level of the roots were evaluated. Four-rooted maxillary first and second molars were classified according to modified Versiani's classification. The root length and cross-sectional diameters of 4-rooted molars were measured by the software Galileos Implant 1.7 (SICAT GmbH & Co. KG, Bonn, Germany). One way analysis of variance followed by a Newman-Keuls post hoc test was used to compare the groups in relation to the root length and diameters (P = 0.05).
Among 1365 maxillary first molars, only one tooth had four separated roots, whereas in second molars, 12 out of 1226 teeth (0.98%) exhibited an extra root; the incidences were 1.28% (7/549) for males and 0.74% (5/677) for females. All 4-rooted molars observed were unilateral. Out of a total of thirteen 4-rooted maxillary molars, six exhibited the type I root form, four exhibited the type II root form and one exhibited the type III root form; a type IV category (two molars) was added to Versiani's classification, which described maxillary molars with three buccal roots. A transitional root form between the typical 3-rooted form and double palatal roots was observed in six cases of 3-rooted molars. Measurements of root size showed that the diameter of the distopalatal roots was significantly larger than the extra mesiopalatal roots (P < 0.01).
The prevalence of the 4-rooted maxillary first and second molars in the Chinese population is low. They usually occurred unilaterally, and the shape, location and size of the four roots may be variable.
通过锥形束计算机断层扫描（CBCT）检测中国西北人群中上颌恒磨牙四根的发生率及解剖特征。
对725例上颌恒第一磨牙和/或第二磨牙发育良好的中国患者进行CBCT检查。评估牙根和根管的数量、形状、位置及牙根的分叉水平。根据改良的韦尔西亚尼分类法对上颌第一和第二磨牙的四根情况进行分类。使用Galileos Implant 1.7软件（德国波恩SICAT GmbH & Co. KG公司）测量四根上颌磨牙的根长和横截面直径。采用单因素方差分析及Newman-Keuls事后检验比较各组的根长和直径（P = 0.05）。
在1365颗上颌第一磨牙中，仅有1颗牙有四个分离的牙根，而在第二磨牙中，1226颗牙中有12颗（0.98%）出现额外牙根；男性发生率为1.28%（7/549），女性为0.74%（5/677）。所有观察到的四根磨牙均为单侧。在总共13颗四根上颌磨牙中，6颗表现为I型牙根形态，4颗表现为II型牙根形态，1颗表现为III型牙根形态；在描述有三个颊根的上颌磨牙的韦尔西亚尼分类法中增加了IV型（2颗磨牙）。在6例三根磨牙中观察到典型三根形态与双腭根之间的过渡牙根形态。牙根大小测量显示，远腭根直径明显大于额外的近腭根（P < 0.01）。
中国人群中上颌第一和第二磨牙四根的发生率较低。它们通常单侧出现，且四根的形状、位置和大小可能存在差异。
