Morita M
Okamoto Research Laboratory of Dentistry, Yonago, Japan.
Shikwa Gakuho. 1990 Jun;90(6):837-54.
Morphological observation of the roots of 2,164 lower first Japanese molars of known sex and side attributes, obtained from the collection of the Okamto Research Laboratory of Dentistry, produced the following results. 1. Roots varied from single to quadruple, but double roots were most common (70.6% in males and 83.4% in females). Next most frequent were triple roots 28.6% in males, 15.75% in females). Single-root was 0.7% in males, 1.1% in females. 2. Quadruple root occurred in only 1, male case (0.04% of the total). 3. Apical ramification occurred in 19.0% of all roots in the double-root category; 16.2% were ramifications on the mesial side only. In triple-root teeth, the ratio was higher: 21.9% for mesial roots. 4. Double-root teeth demonstrated 3 types of form of root apex pointed, rounded, and flat. These types were subdivided into 8 categories. The pointed type was most common (18.9% of the total) for both mesial and distal roots. 5. Orientation and curvature in doubler-root teeth (mesial and distal) were of 2 types. The separated type (Type I), in which the mesial and distal roots separate on the apical side, was most common (96.6% in males, 95.3% in females). 6. In triple-root teeth, size, orientation, and curvature of distal-lingual roots diversified into 8 types. Type V, in which lengths were about 2/3 that of the buccal root, size about half, and general curvature in the buccal-distal cheek plane with general straightness in the mesial-distal plane, was most common, accounting for 40.9% of the males and 47.0% of the females. 7. In double-root teeth, ramification degree between mesial and distal roots was 20.97 degrees in males and 18.97 degrees in females. In triple-root teeth the corresponding angles were 21.33 degrees in males and 18.98 degrees in females. In both cases, the angle was larger in male specimens. 8. In double-root teeth, root length was 12.75 mm in males and 12.41mm in females; root-trunk length was 3.22mm for males and 3.42mm in females. Differences between the sexes were significant in both cases. The root-trunk-length index was 25.24 for males and 27.56 for females, and the ratio of the length of root trunk to the root was 1/4. In triple-root teeth, root length was 12.66mm for males and 12.28mm for females; root-trunk length was 2.99mm for males and 3.21mm for females. The distal-lingual root length in triple-root teeth was 11.48mm in males and 11.10mm in females.(ABSTRACT TRUNCATED AT 400 WORDS)
对从冈山齿科研究实验室收集的2164颗已知性别和牙侧属性的日本下颌第一磨牙牙根进行形态学观察，得出以下结果。1. 牙根数量从单根到四根不等，但双根最为常见（男性中占70.6%，女性中占83.4%）。其次是三根（男性中占28.6%，女性中占15.75%）。单根在男性中占0.7%，女性中占1.1%。2. 四根仅在1例男性病例中出现（占总数的0.04%）。3. 双根类别的所有牙根中，根尖分叉发生率为19.0%；仅在近中侧分叉的占16.2%。在三根牙中，该比例更高：近中根为21.9%。4. 双根牙表现出3种根尖形态：尖形、圆形和平形。这些类型又细分为8类。尖形在近中根和远中根中最为常见（各占总数的18.9%）。5. 双根牙（近中根和远中根）的方向和弯曲度有2种类型。分离型（I型），即近中根和远中根在根尖侧分离，最为常见（男性中占96.6%，女性中占95.3%）。6. 在三根牙中，远中舌侧根的大小、方向和弯曲度分为8种类型。V型最为常见，其长度约为颊根的2/3，大小约为一半，在颊远中颊平面有一般弯曲度，在近中远中平面基本笔直，男性中占40.9%，女性中占47.0%。7. 在双根牙中，近中根和远中根之间的分叉角度男性为20.97度，女性为18.97度。在三根牙中，相应角度男性为21.33度，女性为18.98度。两种情况下，男性标本中的角度都更大。8. 在双根牙中，牙根长度男性为12.75毫米，女性为12.41毫米；根干长度男性为3.22毫米，女性为3.42毫米。两种情况下两性之间的差异均显著。根干长度指数男性为25.24，女性为27.56，根干长度与牙根长度之比为1/4。在三根牙中，牙根长度男性为12.66毫米，女性为12.28毫米；根干长度男性为2.99毫米，女性为3.21毫米。三根牙中远中舌侧根长度男性为11.48毫米，女性为11.10毫米。（摘要截选至400字）
