Abstract The translucency of teeth allows the non-de- structive subsurface visualisation of their microstructure by confocal laser scanning microscopy (CLSM) at a level of about 150 μm below the surface. The dentine–enamel junction (DEJ) is accessible only directly adjacent to the cervix of the tooth. Therefore teeth have to be sectioned for studying marginal areas of the dental hard tissue. The potential of the technique for (pseudo) three-dimensional visualisation allows the study of an array of individual con- focal images, the interpretation of which is similar to that of macroscopic tomographs (CT-scan, MRI). Additionally, the extended focus mode yields the overlay of individual confocal images in the form of a two-dimensional projec- tion. This mode of operation proved to be particularly suited for the visualisation of odontoblast processes in their whole extension. The three-dimensional junction between enamel and dentine, the branches of the odontoblast pro- cesses and their interactions with the DEJ is demonstrable by CLSM without staining or other procedures of sample preparation. The direct microscopic comparison between samples, either fresh or kept in a humid chamber, and Tech- novit-embedded sample blocks gives evidence that the risk of artefacts by sample storage or by the embedding proce- dure is minimal. The tomographs limited to subsurface ar- eas of the tissue also exclude mechanical surface artefacts due to grinding or cutting. Key words Dentine–enamel junction · Odontoblast processes · Dentinal tubules · Confocal laser scanning microscopy Introduction Confocal laser scanning microscopy (CLSM) is an estab- lished technique in cell biology [17]. Jones and Boyde [9] presented the visualisation of dental hard tissue by confo- cal microscopy. The potential of CLSM in histotomogra- phy of hard tissue has been demonstrated on dental ena- mel [6, 7, 10]. These studies revealed the special option of CLSM for in-depth microscopy below the surface of un- treated teeth [8]. Simultaneously, CLSM proved to be use- ful for studying subsurface areas of sectioned samples. Thus, the risk of artefacts caused by, for example, cutting, grinding or drying is minimal [8]. The aim of the present work is to demonstrate the potential of three-dimensional CLSM for studies on the dentine–enamel junction (DEJ), which is characterised by micromorphologically different tissues such as enamel, dentine, and odontoblastic pro- cesses. Materials and methods Fifty totally impacted teeth which had been removed surgically with- out destruction were used for the study. Immediately after extrac- tion, teeth were disinfected in a 0.02% sodium azide solution (2 h; 4°C). Teeth were then cut into two pieces in the vestibulo–oral di- rection. The DEJ in the vestibular and oral areas of one of the moie- ties was subjected to CLSM investigations. The histotomograms were recorded on an electronic storage device. The samples then were placed in a physiological NaCl solution (sealed chamber) at 4 °C, constant temperature. The other moieties of the teeth were embed- ded in Technovit [5]. Tissues were fixed with 50% ethanol. A thin section of about 20-μm thickness was cut from each of the embed- ded samples (sawing–grinding technique [5]). The surface of the re- maining block of the hard tissue was polished with sandpaper. After preparation of the Technovit blocks and the thin sections (5 weeks of processing), intra-individual CLSM comparisons were made between the fresh samples and those stored in physiological NaCl solution. Additionally, microstructure by conventional microscopy of the sections was compared with the corresponding CLSM imag- es of the fresh samples. The Leica confocal laser scanning Aristoplan microscope was equipped with a variable intensity (up to 40 mW) mixed gas Clin Oral Invest (1998) 2: 21–25 © Springer-Verlag 1998 Received: 18 June 1997 / Accepted: 4 December 1997 K. A. Grötz · H. Duschner · T. E. Reichert E. G. de Aguiar · H. Götz · W. Wagner Histotomography of the odontoblast processes at the dentine – enamel junction of permanent healthy human teeth in the confocal laser scanning microscope ORIGINAL ARTICLE K. A. Grötz () · T. E. Reichert · W. Wagner Clinic of Oral and Maxillofacial Surgery, University of Mainz, Augustusplatz 2, D-55131 Mainz, Germany Tel.:+49 6131 175087; Fax: +49 6131 176602 H. Duschner · H. Götz Department of Applied Structure and Microanalysis, University of Mainz, Augustusplatz 2, D-55131 Mainz, Germany E. G. de Aguiar Faculdade de Odontologia, Departamento de Chirurgia, Universidade Federal de Minas Gerais, Rua Conde de Linhares, 141-Cidade Jardim, 30380-030 Belo Horizonte, Brazil