The Equine Dental Pulp: Analysis of the Stratigraphic Arrangement of the Equine Dental Pulp in Incisors and Cheek Teeth

SIMPLE SUMMARY: The crown pulp of permanent brachydont (short-crowned) teeth features a stratigraphic arrangement composed of a cell-free and a cell-rich zone. This stratigraphy is assumed to reflect a mature, less active status with only minor production of secondary dentin. In contrast, the hypsodont (high-crowned) equine tooth is required to sustain a production of large amounts of subocclusal dentin to compensate for lifelong occlusal wear of several mm per year. It is hypothesized that the remarkable productivity of the equine pulp is reflected by distinct histomorphological features of the pulpal tissue. Therefore, teeth of horses of different ages were investigated, paying special attention to identify the cellular arrangement at the pulp–dentin interface. In general, the layer of odontoblasts was followed by a dense arrangement of fibroblastic cells in a network of small-sized blood vessels as well as a high concentration of single nerve fibers, suggesting a subodontoblastic supportive zone. The formation of distinct zones as described in the brachydont crown pulp is absent. The observed histomorphological characteristics of the equine pulp are regarded as representing a highly productive status, which presumably accounts for the reception of mechanical stimuli; a high capacity for cellular regeneration; and finally, the required subocclusal dentin production. ABSTRACT: In the crown pulp of brachydont teeth, a cell-free and a cell-rich zone are established beneath the odontoblastic layer, indicating a mature status. For the equine dental pulp, there are no descriptions which allow for a comparative analysis with regard to functional requirements in terms of lifelong secondary dentin production to compensate for occlusal wear. For histomorphological and immunohistological investigations, ten incisors and ten check teeth were used from seven adult horses and five foals. In the periphery of the equine dental pulp, a constant predentin and odontoblastic cell layer was present, followed by densely packed fibroblastic cells, capillary networks, and a high concentration of nerve fibers, suggesting a subodontoblastic supportive zone. Whilst the size of the equine dental pulp decreased with age, the numbers of blood vessels, nerve fibers, and fibroblastic cells increased with age. Histological analysis of the equine dental pulp did not show a cell-free and cell-rich zone as described in the brachydont crown pulp. The equine dental pulp remained in a juvenile status even in aged horses, with morphological features indicating a high capacity for dentine production.