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首页> 外文期刊>The Internet Journal of Medical Technology >Evolution And History Of The Periodontal Ligament - A Review
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Evolution And History Of The Periodontal Ligament - A Review

机译：牙周膜的演变与历史-综述

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The periodontium is defined as those tissues supporting and investing the tooth, comprises of root cementum, periodontal ligament, bone lining the tooth socket and that part of the gingiva facing the tooth. The widespread occurrence of periodontal diseases and the realization that lost tissues can be repaired and perhaps regenerated has generated considerable interest in the factors and cells regulating their formation and maintenance. It is important to understand that each of the periodontal components has its very specialized structure and these structural characteristics directly define function. Indeed, proper functioning of the periodontium is only achieved through structural integrity and interaction between its components. Evolution Although the various methods by which teeth are fixed in their position upon the bones which carry them pass by gradational forms into one another, so that a simple and at the same time absolutely correct classification is, impossible, yet for the purpose of description for principal methods may be enumerated, namely, attachment by means of fibrous membrane, by a hinge, by ankylosis and by implantation in bony sockets. There is a fundamental difference between the attachment of reptilian and mammalian teeth. In the ancestral reptiles the teeth are ankylosed to the bone. In mammals they are suspended in their sockets by ligaments. The evolutionary step from reptile to mammal included a series of co-ordinated changes in the jaws. The central point of these changes is the radical “Reconstruction” of the mandible. In reptiles the mandible consists of a series of bones united by sutures. Only the upper most bones, the dentary, carry the ankylosed tooth. The change from the many – boned reptiles to the single-?boned mammalian mandible brought with it a radical change in the mode of growth. In the reptile, the mandibular and maxillary teeth “move” with the bones to which they are fused. In the mammal the teeth have to “move” as units independent of the bones, and this movement is made possible by the remodelling of the periodontium. The evolutionary change from the reptiles to the mammals replaces the ankylosis of tooth and bone to a ligamentous suspension of the tooth. This change permits movement of mammalian teeth and the continued repositioning necessitated by jaw growth or tooth wear. Cells Of The Periodontal Ligament Fibroblasts The fibroblasts lie between the collagen fibers and although various shapes have been described (Fullmer6 ; Roberts and Chamberlain14), it is likely that their appearance is governed by the surrounding matrix (Ross13). The periodontal ligament fibroblast contains a prominent nucleus, which has single distinct nucleolus and clearly defined nuclear pores. When stained with colloidal silver (Crocker and Nar) it demonstrates either one or two regions of acidic proteins which are associated with nucleolar organizer regions (Shore et al., 1991). An internal dense lamina characteristic of connective tissue cells is also found. The nucleus is of a flattened disc shape, and it has a diameter of approximately 10 μm (Shore and Berkovitz2) and may occupy up to 30% of the cell volume. (Beertsen and Everts1; Yamasaki et al.28). Its outline is relatively smooth and no form of crenulation is present in the ‘in vivo’ state. However, in certain induced pathological conditions such as “Cyclosporin-induced hypertrophy”“, a crenulated nuclei may be present in a significant number of cells (Yamasaki et aL, 28). As fibroblasts produce the extra-cellular matrix of the periodontal ligament, which demonstrates a very high rate of turnover (Sodek23) the cells contain significant amounts of organelles involved in protein synthesis and degradation. The synthetic pathway in these cells is same as other protein? matrix producing cells, such as odontoblasts, ameloblasts, etc. Cho & grant3 have demonstrated using tritiated proline in a mise-chase experiment that the synthetic pathway is from: Rough
机译：牙周组织被定义为支撑和伸展牙齿的那些组织，包括牙骨质，牙周膜，骨槽的骨衬以及面对牙齿的牙龈部分。牙周疾病的广泛发生以及丢失的组织可以得到修复和可能再生的认识引起了人们对调节其形成和维持的因子和细胞的极大兴趣。重要的是要了解每个牙周组件都有其非常特殊的结构，并且这些结构特征直接定义了功能。确实，牙周组织的正常功能只能通过结构完整性及其组件之间的相互作用来实现。演化尽管将牙齿固定在骨头上的各种方法通过渐进形式彼此过渡，但是不可能进行简单而绝对正确的分类，但出于描述目的可以列举出主要方法，即通过纤维膜，通过铰链，通过强直和通过在骨窝中植入来进行附着。爬行动物和哺乳动物牙齿的附着之间存在根本差异。在祖先的爬行动物中，牙齿被强直到骨骼。在哺乳动物中，它们被韧带悬挂在它们的窝中。从爬行动物到哺乳动物的进化步骤包括一系列颌骨协调变化。这些变化的中心点是对下颌骨进行彻底的“重建”。在爬行动物中，下颌骨由一系列缝合在一起的骨头组成。只有最上端的骨头，即牙齿，才带有强直牙齿。从许多带骨骼的爬行动物到单链哺乳动物下颌骨的转变，带来了生长方式的根本变化。在爬行动物中，下颌和上颌牙齿与融合了它们的骨骼“运动”。在哺乳动物中，牙齿必须作为独立于骨骼的单元“运动”，并且通过牙周膜的重塑使这种运动成为可能。从爬行动物到哺乳动物的进化变化将牙齿和骨骼的强直性疾病替换为韧带状的牙齿悬浮。这种变化可以使哺乳动物的牙齿运动，并允许颌骨增长或牙齿磨损而需要继续进行重新定位。牙周膜成纤维细胞的细胞成纤维细胞位于胶原纤维之间，尽管已经描述了各种形状（Fullmer6; Roberts和Chamberlain14），但它们的外观可能受周围基质的控制（Ross13）。牙周膜成纤维细胞包含一个突出的核，具有单个不同的核仁和清晰定义的核孔。当用胶体银染色时（Crocker和Nar），它表明一个或两个酸性蛋白区域与核仁组织者区域有关（Shore等，1991）。还发现了结缔组织细胞的内部致密层。核呈扁平的盘状，直径约为10μm（Shore和Berkovitz2），最多可占据细胞体积的30％。 （Beertsen and Everts1; Yamasaki et al.28）。它的轮廓相对光滑，在“体内”状态下没有任何形式的齿状弯曲。但是，在某些诱发的病理情况下，例如“环孢菌素诱发的肥大”，在许多细胞中可能存在有核的核（Yamasaki等，28）。由于成纤维细胞产生牙周膜的细胞外基质，这表明其周转率非常高（Sodek23），细胞中包含大量参与蛋白质合成和降解的细胞器。这些细胞中的合成途径与其他蛋白质相同吗？产生基质的细胞，例如成牙本质细胞，成釉细胞等。Cho＆Grant3已在mis选实验中使用tri化脯氨酸证明合成途径来自：

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