鱼中矿化组织的调色板很宽,这在鱼牙本质中尤为明显。虽然除了鱼以外,所有脊椎动物的牙齿都含有单一的牙本质组织类型,叫做orthodentin,鱼牙齿中的牙本质可以是几种不同组织类型之一。鱼类中最常见的牙本质类型是正齿蛋白。Orthodentin的特征在于几个关键的结构特征,这些特征与骨骼和骨蛋白的特征根本不同。骨桥蛋白,鱼类中第二常见的牙本质类型(基于迄今为止研究牙齿结构的30,000种现存鱼类中的一小部分),在大多数Selachians(鲨鱼和射线)以及几种硬骨鱼物种中发现,在结构上与正统蛋白不同。在这里,我们研究了以下假设:骨蛋白在其微观和纳米结构方面与无骨细胞骨组织相似。我们使用聚焦离子束扫描电子显微镜(FIB/SEM),以及其他几种高分辨率成像技术,表征骨蛋白三个主要成分的3D结构(denteons,齿间矩阵,以及它们之间的过渡区)。我们证明了骨桥蛋白的基质,虽然无细胞,与哺乳动物的骨基质非常相似,无论是在一般形态上还是在其矿化胶原纤维的三维纳米排列上。我们还记录了复杂的纳米通道网络的存在,类似于最近在骨骼中描述的这种网络。最后,我们记录了一系列超矿化的小珍珠的存在,它们围绕着牙齿运河,并表征它们的结构。
The palette of mineralized tissues in fish is wide, and this is particularly apparent in fish dentin. While the teeth of all vertebrates except fish contain a single dentinal tissue type, called orthodentin, dentin in the teeth of fish can be one of several different tissue types. The most common dentin type in fish is orthodentin. Orthodentin is characterized by several key structural features that are fundamentally different from those of bone and from those of
osteodentin.
Osteodentin, the second-most common dentin type in fish (based on the tiny fraction of fish species out of ∼30,000 extant fish species in which tooth structure was so far studied), is found in most Selachians (sharks and rays) as well as in several teleost species, and is structurally different from orthodentin. Here we examine the hypothesis that
osteodentin is similar to anosteocytic bone tissue in terms of its micro- and nano-structure. We use Focused Ion Beam-Scanning Electron Microscopy (FIB/SEM), as well as several other high-resolution imaging techniques, to characterize the 3D architecture of the three main components of
osteodentin (denteons, inter-denteonal matrix, and the transition zone between them). We show that the matrix of
osteodentin, although acellular, is extremely similar to mammalian osteonal bone matrix, both in general morphology and in the three-dimensional nano-arrangement of its mineralized collagen fibrils. We also document the presence of a complex network of nano-channels, similar to such networks recently described in bone. Finally, we document the presence of strings of hyper-mineralized small \'pearls\' which surround the denteonal canals, and characterize their structure.