Department of Pediatric Dentistry, College of Dentistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea.
Arch Oral Biol. 2013 Mar;58(3):248-53. doi: 10.1016/j.archoralbio.2012.07.015. Epub 2012 Sep 13.
The mandibular molars typically have two roots placed mesiodistally, but they occasionally have an additional distolingual (DL) root. This study was to determine the morphological characteristics of the crown of such mandibular molars.
Radiographic records and study models were collected from a Korean population (n=86 patients). Each molar was assigned to either the experimental group (i.e. with a DL root) or the control group (i.e. without a DL root; n=41 patients) based on the radiographic findings. The intercuspal distances of the first permanent molars (total, n=100; control/experimental, n=50/50) and primary second molars (46, 23/23), and the largest buccolingual/mesiodistal widths of those molars and primary first molars (42, 21/21) were measured for molars with and without a DL root. In addition, the correlation between the existence of a sixth cusp and a DL root was examined.
The crowns of first permanent and primary second molars with DL roots had significantly larger intercuspal distances between the distobuccal-distolingual cusp tips and a larger distal-area buccolingual width than those without the DL root (t-test; p<0.05). There was no significant correlation between the existence of a sixth cusp and the presence of a DL root.
The existence of a DL root was associated with larger buccolingual dimensions, especially in the distal area.
下颌磨牙通常有两个颊舌向放置的牙根，但偶尔会有一个额外的远中舌侧（DL）根。本研究旨在确定具有 DL 根的下颌磨牙牙冠的形态特征。
从韩国人群（n=86 例患者）中收集影像学记录和研究模型。根据影像学表现，将每个磨牙分为实验组（即有 DL 根）和对照组（即无 DL 根；n=41 例）。测量第一恒磨牙（总，n=100；对照组/实验组，n=50/50）和乳磨牙第二磨牙（46，23/23）的正中牙合距离，以及有和无 DL 根的磨牙的最大颊舌向/近远中向宽度和乳磨牙第一磨牙（42，21/21）。此外，还检查了第六尖的存在与 DL 根之间的关系。
具有 DL 根的第一恒磨牙和乳磨牙第二磨牙的牙冠，其颊舌向远中尖之间的正中牙合距离和远中颊舌向宽度明显大于无 DL 根者（t 检验；p<0.05）。第六尖的存在与 DL 根的存在之间无显著相关性。
DL 根的存在与颊舌向较大的尺寸有关，尤其是在远中区域。
