Histological review of the human cellular cementum with special reference to an alternating lamellar pattern.
Cementum is mineralized tissue with collagen fibrils as its major organic component, and it can be roughly classified into acellular and cellular cementum. The latter generally consists of a stack of cellular intrinsic fiber cementum layers, in which intensely and weakly stained lamellae (each about 2.5 microm thick) alternate in light microscopic observations. It has been suggested that the alternate lamellar pattern results from periodic changes of the intrinsic fiber arrangement, but owing to the difficulty of observing the fibril arrangement three dimensionally, details were not understood until recently. The NaOH-maceration method has been developed to overcome this difficulty. For the past two decades, we have studied the structure and development of cementum by scanning electron microscopy using NaOH-maceration, as well as by light and transmission electron microscopy, and have accumulated a significant amount of data with regard to the structure and formation of cementum. In light of these data, we have arrived at the following conclusions: (1) The alternate lamellar pattern conforms to the twisted plywood model, in which collagen fibrils rotate regularly in the same direction to form two alternating types of lamellae; one type consists of transversely and almost transversely cut fibrils and the other consists of longitudinally and almost longitudinally cut fibrils. (2) The development of the intrinsic fiber arrangement may be controlled by cementoblasts; the cementoblasts move finger-like processes synchronously and periodically to create alternate changes in the intrinsic fiber arrangement, and this dynamic sequence results in the alternate lamellar pattern.
Yamamoto
Tsuneyuki
T
Department of Developmental Biology of Hard Tissue, Division of Oral Health Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-Ku, Sapporo, 060-8586, Japan. yamatsu@den.hokudai.ac.jp
Li
Minqi
M
Liu
Zhucheng
Z
Guo
Ying
Y
Hasegawa
Tomoka
T
Masuki
Hideo
H
Suzuki
Reiko
R
Amizuka
Norio
N
D003739:Dental Cementum / Q000166:cytology* / Q000648:ultrastructure; D024022:Fibrillar Collagens / Q000648:ultrastructure; D006801:Humans; D014092:Tooth Root / Q000166:cytology / Q000648:ultrastructure
D024022:Fibrillar Collagens