Electron microscopy of undecalcified sections of human adult dentine

Abstract

Ultra-thin sections of non-decalcified human dentine from recently erupted molars, fixed in 1% osmic acid and embedded in n-butyl methacrylate, were cut with a Servall-Porter microtome, equipped with a diamond knife, and examined with the electron microscope. In predentine and dentine near the pulp, the odontoblast process appears to be a cytoplasmic extension which fills the lumen of the dentinal tubule. In the middle and outer parts of calcified dentine, the odontoblast process takes on a tubular form. In calcified dentine, a peritubular zone surrounds both the tubular and the cytoplasmic parts of the odontoblast process. The greater degree of electron absorption exhibited by the peritubular zone, together with the observation that selective area electron diffraction shows the presence of apatite, lead to the conclusion that this zone is more calcified than the intertubular substance. The peritubular zone consists of a fibrillar matrix and inorganic elements, both of which are easily destroyed during routine histological decalcification. Occasional dentinal tubules show no peritubular zone.