[The microscope pressure button, Purkinje's contribution to microscopy technology]. / Mikroskopické tlacidlo, purkynuv príspevek k mikroskopické technice.

Purkyne was familiar even with microscopic technique, he improved some procedures and elaborated many himself. He described also a microscope button which made it possible to regulate sensitively the compression of the preparation by the micrometric screw. The author submits Purkyne's paper which was not published in Czech so far.

[Fluoride ions and apatite recrystallization of apatite in enamel]. / Fluoridové ionty a rekrystalizace apatitu ve sklovine.

The authors discuss the basic process on which the principle of fluoridation in based--i.e. the mutual exchange of F- ions and the OH- group in hydroxyapatite of enamel. Model investigations assessing the energy difference between hydroxyapatite and F- and fluorapatite and the OH- group indicate that fluorapatite tends to release steadily fluoride ions and to change into hydroxyapatite. This tendency, apparently inopportune from the aspects of caries prevention, ensures, however, a permanent low F- level above the enamel surface. The presence of F- ions facilitates recrystalization of apatite in the initial caries stage. The investigation tries to throw new light, from the point of view of theoretical chemistry at a molecular level, on the mechanism of remineralization, one of the most important ways which implements the preventive action of fluoride.

[The human dental pulp as viewed through a scanning electron microscope (author's transl)]. / Die Pulpa der menschlichen Zähne im Rasterelektronenmikroskop.

The human dental pulp was examined using a scanning electron microscope. The odontoblasts are pear-shaped and have a fine-grain surface structure. Tomes' process divides into fine branches before entering the predentin. Very few fibroblasts were found. These had stronger cell processes at the two terminal poles. Adhering to their surfaces were fine fibers. Collagenous and nerve fibers could not be accurately identified in the rich fibrillary network of the pulp. Stronger nerve fasciculi were readily observable through longitudinal sulci. Thinner fibers were seen to spread out in branches from some nerve bundles. The capillaries were observed to be surrounded by a sheath of fine fibrils.

Scanning electron microscopic examination of root after apicoectomy.

The scanning electron microscope was used to examine resected areas of eight roots of human teeth extracted after long intervals following surgical procedures. Some resorption lacunae were observed in the areas with protuberances of newly formed cementum. In the lacunae, honeycomb-like structures were found. On the resected surface, residues of ligaments and periodontal fibers, and in one of the specimens dentinal tubules with odontoblastic processes protruding above the surface were present.

[Root canal filling after apicoectomy, as seen on the scanning electron microscope]. / Wurzelkanalfüllung nach Wurzelspitzenresektion im Rasterelektronenmikroskop.

The radiologically controled apicectomy shows frequently unsuccessful results. In histological examinations of the root apex area after apicectomy chronic inflammation is regularly seen even in negative radiologic findings. Examination of the most frequently used root filling material (zincoxyphosphate with guttapercha point) by scanning electron microscopy shows a porous surface and between the canal wall and the root filling material there appears regularly a deep groove as no contact is achieved. The rough surface structure, the chemical composition and the loose contact of the components in this area are considered irritative factors and reasons of failure in treatment.