Ultrastructure of human dentine 40 years ago — progress and perspectives

In the 1959 premier issue of the Archives of Oral Biology, the first TEM observations were presented of sections of undecalcified human mature dentine produced with diamond knives. The odontoblast process was clearly shown to be a cytoplasmic extension of the odontoblast. The peritubular dentine appeared to be more calcified than the intertubular dentine and contained hydroxyapatite as demonstrated by selective area electron diffraction. In the 40 years which followed, significant progress was made in TEM methodology, including improvements in fixation and embedding, development of ultrastructural cytochemistry and immunocytochemistry, and the use of electron microscope autoradiography. Additionally, we saw the advent of SEM and HRTEM. Thus, better knowledge was gained of (1) the odontoblast and its process and the lamina limitans, (2) the dentinal nerve fibrils and (3) the HRTEM aspects of dentine. Interestingly, to the present day, diamond knives have continued to serve as the best tool for preparing thin sections of non-decalcified mature hard tissue for TEM and HRTEM, not only for dentine but also for bone, enamel and cementum.