This thesis was based on the hypothesis that the hierarchical structure and the micro- to nano-architecture of the dentin in the teeth of the Atlantic wolfish, A. lupus, are adapted to their mechanical function. The dentin in the teeth of the wolfish is of a type called osteodentin, which is the second most common type of dentin in fish. It is  morphologically distinct  which is similar to that of osteonal bone. Although this type of dentin has been recognized for about 200 years, its structure is still controversial although it is universally considered true dentin . The purpose of this thesis was to examine this padygm, employing advanced and high resolution 2-D and 3-D methods to characterize its structure and mechanical properties, measure the deformation and strain fields developing in whole teeth under load, study the process of development of replacement teeth to mature teeth and describe the 3D nano-arrangement of the mineralized collagen fibrils of which they are constituted. I show that our findings  point toward a remarkable similarity of osteo-dentin (at all hierarchical levels) to fibro-lamellar and osteonal bone, and lead me to suggest that osteodentin is in fact bone. These findings contribute to the basic understanding of the evolution of mineralized tissues.