Rasterelektronenmikroskopische Untersuchung zur Neonatallinie an Milchzähnen

Aim of this study was to investigate the ultrastructure of the neonatal line (NNL) using a scanning electron microscope. The study comprised five sound primary front teeth and five sound primary molars. All teeth were hemi-sectioned (Mikro-Trenn MT 1557, Hofer, Swiss). The smear layer was removed in one of the hemi-sectioned specimens by acid etching with 35% phosphoric acid for 30 s. The examination was carried out after drying and gold sputtering of each specimen under a SEM 515 (Philips, Eindhoven, The Netherlands) using a constant cathode voltage of 20 kV and a maximum magnification of 15.000. In seven teeth a NNL was visualized by SEM. At 1.000x magnification only an irregular structure of the enamel prisms was observed. Detailed images showed a typical interruption of the prisms at the NNL between 5.000x to 15.000x magnification; nearly all crystallites of a prism were not mineralised up to a length of 0,5 pm. As a result of frequent consumption of erosive and/or cariogenic drinks and foods the predominant demineralisation of the enamel nearby the NNL could be enabled. This could give an explanation for the initiation and rapid progression of the carious process at the NNL.