Luan Xianghong, Walker Cameron, Dangaria Smit, Ito Yoshihiro, Druzinsky Robert, Jarosius Kristina, Lesot Herve, Rieppel Olivier
Departments of Oral Biology, University of Illinois at Chicago, Chicago, IL 60612, USA.
Evol Dev. 2009 May-Jun;11(3):247-59. doi: 10.1111/j.1525-142X.2009.00327.x.
Vertebrate teeth are attached to jaws by a variety of mechanisms, including acrodont, pleurodont, and thecodont modes of attachment. Recent studies have suggested that various modes of attachment exist within each subcategory. Especially squamates feature a broad diversity of modes of attachment. Here we have investigated tooth attachment tissues in the late cretaceous mosasaur Clidastes and compared mosasaur tooth attachment with modes of attachment found in other extant reptiles. Using histologic analysis of ultrathin ground sections, four distinct mineralized tissues that anchor mosasaur teeth to the jaw were identified: (i) an acellular cementum layer at the interface between root and cellular cementum, (ii) a massive cone consisting of trabecular cellular cementum, (iii) the mineralized periodontal ligament containing mineralized Sharpey's fibers, and (iv) the interdental ridges connecting adjacent teeth. The complex, multilayered attachment apparatus in mosasaurs was compared with attachment tissues in extant reptiles, including Iguana and Caiman. Based on our comparative analysis we postulate the presence of a quadruple-layer tissue architecture underlying reptilian tooth attachment, comprised of acellular cementum, cellular cementum, mineralized periodontal ligament, and interdental ridge (alveolar bone). We propose that the mineralization status of the periodontal ligament is a dynamic feature in vertebrate evolution subject to functional adaptation.
脊椎动物的牙齿通过多种机制附着于颌骨，包括端生齿、侧生齿和槽生齿的附着方式。最近的研究表明，每个亚类中都存在多种附着方式。特别是有鳞目动物具有广泛多样的附着方式。在这里，我们研究了白垩纪晚期沧龙克利达斯的牙齿附着组织，并将沧龙的牙齿附着与其他现存爬行动物的附着方式进行了比较。通过对超薄磨片的组织学分析，确定了将沧龙牙齿固定在颌骨上的四种不同矿化组织：（i）牙根与细胞性牙骨质界面处的无细胞牙骨质层；（ii）由小梁状细胞性牙骨质组成的块状锥体；（iii）含有矿化沙比纤维的矿化牙周韧带；（iv）连接相邻牙齿的齿间嵴。将沧龙复杂的多层附着装置与现存爬行动物（包括鬣蜥和凯门鳄）的附着组织进行了比较。基于我们的比较分析，我们推测爬行动物牙齿附着存在一种四层组织结构，由无细胞牙骨质、细胞性牙骨质、矿化牙周韧带和齿间嵴（牙槽骨）组成。我们提出，牙周韧带的矿化状态是脊椎动物进化过程中受功能适应影响的一个动态特征。
