Dentin and pulp are histologically different. However,
they have the same embryonic origin; ectomesenchymal
origin. The formation of dentin-pulp causes
dentin to be affected by pulp and vice versa. Dentin has
very minute tubules which are filled with odontoblastic
process. The processes are also surrounded by dentinal
fluid which forms about 22% of the total volume of
dentin. The fluid is completely filtrated and originates
from the blood vessels of the pulp