Pulp Dentin Organ

The dentin and the pulp must be considered as one organ (the pulp-dentin complex) because of the intimate relationship between the cellular tissue within the dentin and the peripheral pulp tissue. The embryonic dental papilla is responsible for the formation of this coupled tissue. Hence it is obvious that the response of the pulp to any restorative material will be influenced by its surrounding dentin also. The dentinal tubules occupy 20-39% of dentin, and the dentinal fluid within them represents about 22% of the total volume of dentin. Dentinal fluid in the tubules, which is continuous with the extra-cellular fluid of the pulp, serves as a medium for relaying injurious agents to the pulp to reduce an inflammatory response.

Thus anything that contacts the living dentin can be carried into the pulp. Also, either positive hydrostatic pressure or negative osmotic pressure may move the fluid in the dentinal tubules, which may displace the odontoblastic process or nerve endings resulting in pain.