Osteodentin in the Atlantic wolffish (Anarhichas lupus): Dentin or bone?

• Published in: Journal of morphology (1931) Vol. 283; no. 2; pp. 219 - 235
• Main Authors: Thangadurai, Senthil, Brumfeld, Vlad, Milgram, Joshua, Li, Ling, Shahar, Ron
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.02.2022
• Subjects: Animals; denteon; Dentin; Fishes; Odontoblasts; osteodentin; osteon; Perciformes; wolffish; osteon; denteon; wolffish; osteodentin
• ISSN: 0362-2525; 1097-4687
• DOI: 10.1002/jmor.21438

The teeth of actinopterygian fish, like those of mammals, consist of a thin outer hyper‐mineralized layer (enamel or enameloid) that surrounds a core of dentin. While all mammalian species have a single type of dentin (called orthodentin), various dentin types have been reported in the teeth of actinopterygian fish. The most common type of actinopterygian fish dentin is orthodentin. However, the second most common type of actinopterygian fish dentin, called osteodentin, found in several teleost species and in many Selachians, is structurally radically different from orthodentin. Osteodentin, comprising denteons and inter‐denteonal matrix, is characterized by an appearance that is similar to mammalian osteonal bone, however, it lacks cells and a lacuno‐canalicular system. The current consensus is that although osteodentin is morphologically different from orthodentin, it is a true dentinal material, the product of odontoblast cells. We present the results of a study of osteodentin found in the teeth of the Atlantic wolffish, Anarhichas lupus. Using a variety of microscopy techniques, high‐resolution microCT scans, and micro‐indentation we describe the three‐dimensional structure of both its components (denteons and inter‐denteonal matrix), as well as their mineral density distribution and mechanical properties, at several length‐scales. We show that wolffish osteodentin is remarkably similar to the anosteocytic bone of the swords of several swordfish species. We also describe the three‐dimensional network of canals found in mature osteodentin. The high density of these canals in a metabolically inactive, acellular tissue casts doubt upon the accepted paradigm, that the canals house a vascular network. Osteodentin is the second‐most common type of dentin in fish. We studied in detail the three‐dimensional structure of osteodentin, its mineral density distribution, and mechanical properties, at several length scales, in the teeth of the Atlantic wolffish (a, b). Osteodentin is comprised of denteons and inter‐denteonal material (c, d, f). Based on our findings we point out the similarity of osteodentin and the anosteocytic bone present in the swords of swordfish, and suggest they may be the same material. The dense canal system within osteodentin (e) is considered to house a vascular network, but its high density in a metabolically‐inactive acellular tissue raises doubts about this paradigm.