Dentin tooth tissue, coloured scanning electron micrograph (SEM). Dentin (also called substantia eburnea) is similar to bone. It is a mineralised connective tissue found under a tooth's enamel. It forms the bulk of a tooth and differs from bone in its microscopic structure, which is seen here. The wavy lines are tubes that have been exposed by cutting into the dentin. The tubes are called dental canaliculi (or tubules). These tubules are where extensions from the odontoblast cells (part of the pulp at the core of a tooth) have formed the surrounding dentin matrix. These odontoblastic extensions (or processes) allow dentin to rebuild itself, unlike enamel. Magnification: x1450 when printed 10cm wide.