Dead tracts

→ Ground section of the dentin under transmitted light sometimes shows a group of dark lines that follow the course of dentinal tubules called as dead tracts. → They are groups of dead degenerated odontoblastic processes in the dentinal tubules → These tubules are empty and are filled with air → They appear black in transmitted and white in reflected light → At some places, Reparative dentin seals dentinal tubules at their pulpal ends → So, dentinal tubules fill with fluid or gaseous substances. → Such groups of tubules may entrap air & appear black in transmitted & white in reflected light Etiology → Caries, attrition, abrasion, cavity preparation, or erosion Location → MC observed in the area of narrow pulpal horns because of crowding of odontoblasts. Significance → These areas demonstrate decreased sensitivity → They appear to a greater extent in older teeth due to the aging process. → Dead tracts are probably the initial step in the formation of sclerotic dentin.