A preliminary comparative study of dental tissues in mammals with different eating habits.

Introduction: In mammals, teeth have different morphological and structural characteristics in relation to their eating habits. The human dental enamel is the most mineralized and the hardest tissue in the body. The armadillo, a mammal from the   Dasypodidae family that lives in rural areas of Argentina, has a special dentition, different from the human, with teeth of continuous growth, cylindrical and reportedly  without enamel. As their teeth do not have chewing function, their diet is relatively soft. Objective: to compare the anatomical, histological and imaging characteristics of human and armadillo teeth. Methodology: The anatomical, histological and tomographic description of human teeth and mandibles of armadillos from rural areas of the province of Córdoba (Argentina) was performed. For the histological analysis, ground sections at level of the first mandibular molar were obtained . Cone-beam tomography slices 1 mm thick were also performed. The images were analyzed with Romexis 4.4.O.R software. Results: it was determined that in the armadillo all its teeth are similar: cylindrical, molariform , and  with open tubular roots. Microscopically the dentine occupied the entire thickness of the tooth. No enamel was observed . The canaliculi started from the tooth cavity ending in the free surface of the tooth. A plenty of opaque dentine, granular layer and longitudinal incremental lines similar to those found in human dental cement were found. In  tomographic sections it was observed that teeth  had a hyperdense  external tissue,( 0.65 mm thick along the entire tooth surface with 1897-1881 HU density), and another internal tissue (1485-1386 HU)  forming  the body of the tooth with a thickness of 1.65 mm. The cylindrical root appeared as a hyperdense circular strip of 1.08 mm maximum thickness in axial sections. Conclusions: The dentine of the armadillo has canaliculi as a structural unit and granular stratum as well as human dentine. However It is noteworthy in the armadillo, the presence of teeth without enamel, so that dentin exposed to external surfaces presents a high degree of mineralization, compared with human dentin. Future studies should be carried out to evaluate in detail, the hyperdense superficial dentinal zone, of the armadillo.