Focused Ion Beam-Sem 3d Study of Osteodentin in the Teeth of the Atlantic Wolfish Anarhichas Lupus

Abstract

The palette of mineralized tissues in fish is wide, and this is particularly apparent in fish dentin, which includes several very different types. The dentin in the teeth of most Osteichthyes (bony fish) is orthodentin, identical to mammalian dentin. Orthodentin is produced by odontoblasts, and its acellular matrix is traversed by numerous 1-2 µm tubules containing processes of odontoblasts lining its inner surface. Osteodentin, the second-most common dentin type in fish, which is found in most Selachians (sharks and rays) as well as in several teleost species, is structurally different from orthodentin.Here 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, and the appearance of a hyper-mineralized layer in the early stages of the formation of osteodentin.

Keywords: dentin, osteodentin, bone material, FIB/SEM, nanochannels