An Improved Method for the Preparation of "Serial" Sections of Undecalcified Dental Tissues
INCE our previous report' various improvements on the existing methods bJof sectioning undecalcified dental tissues have come to our knowledge. Lefkowitz2 used a rapidly revolving large diameter phosphobronze disc, the circumference of which was charged with diamond powder. The width of the cuts produced by his apparatus is not given, but it cannot have been less than 0.150 mm., this being the thickness of the disc. As the thickness of the sections is stated to vary from 0.250 to 0.400 mm., this method can at best have yielded an average of 2 sections per mm. Sognnaes3 cuts a number of sections simultaneously with a set of circular steel saws each 0.250 mm. thick. Only one 0.750 mm. section is produced per mm. But, as in the case of Lefkowitz' apparatus, comparatively large sections can be obtained (e.g., complete longitudinal sections of human molars). His introduction of methyl methacrylate as an embedding medium constitutes an important improvement of the technic. In a very simple arrangement Atkinson4' 5 employed bonded carborundum discs from 0.8 to 0.125 mm. in thickness, but it is not stated how many sections per mm. can be obtained. In this case too, large sections can apparently be made. In 1946 we1 reported on a method producing small sections at the rate of 5 sections per 2 mm. The number of sections per mm. and the size of the sections seemed capable of improvement. A large and very thin circular saw blade is capable of cutting large sections and at the same time causing small losses of material as narrow saw cuts can be made with it. The unstability of its cutting edge calls for an allowance in the distance of the successive saw cuts (i.e., in the thickness of the slabs) which precludes an approach to serial sectioning.* On the other hand, as in our 1946 machine, the unwavering edge of a narrow and thick saw blade enables very thin sections to be cut, but there is a regrettable loss of material and moreover only small blocks of tissue can be cut. In general, a thin free saw blade can be given a firmness comparable to that of a narrow thick blade by subjecting it to a tension as is done in the ordinary bow saw. Our first apparatus built on this principle was a miniature reciprocating saw. The length of the saw blade (a narrow strip of phosphobronze 2 mm. in width and 0.120 mm. thick) was 3 cm. and the stroke 2 cm. It was driven at the rate of 150 strokes per minute. Diamond powder applied to the edge of the saw blade acted as a cutting agent. Owing to the relatively short stroke and the slowness of action only small pieces of dental tissue could be sectioned by this machine, but not less than four 0.075 mm. sections per mm. could be obtained. The saw cuts were 0.175 mm. in width.
Ultrastructural aspects of human dentine decalcified with chromium sulphate
A recently-developed method for histological decalcification using aqueous solutions of basic chromium (III) sulphate has been applied to thin sections of adult human dentine. Subsequent studies in the electron microscope show a very good retention of morphological detail in the extracellular regions.Special attention was given to the appearance of the peritubular matrix within which well-differentiated layers were recognised. There was substantial agreement between electron microscopy and recent studies of the same matric under the light microscope, allowing a novel hypothesis for the formation of the peritubular dentine.RésuméUne méthode nouvelle de décalcification histologique utilisant des solutions aqueuses de sulfate de chrome basique (III) est appliquée à des coupes fines de dentine humaine adulte. L'observation en microscopie électronique montre une bonne conservation structurale dans les régions extra-cellulaires. L'aspect de la matrice péricanaliculaire est particulièrement étudié. On y reconnait plusieurs couches bien individualisées. Une bonne concordance est notée entre les résultats obtenus par microscopie optique et électronique, permettant d'établir une hypothèse nouvelle sur la formation de la dentine péricanaliculaire.ZusammenfassungEine kürzlich entwickelte Methode zur histologischen Entkalkung mittels wäßriger Lösungen von basischem Chrom III-Sulfat wird an dünnen Schliffen von menschlichem Dentin Erwachsener angewandt. Darauffolgende Untersuchungen am Elektronenmikroskop zeigten eine sehr gute Wiedergabe der morphologischen Einzelheiten in den Extrazellulär-Regionen.Besonders beachtet wurde das Aussehen der peritubulären Matrix, innerhalb welcher gut differenzierte Schichten erkannt werden konnten. Eine wesentliche Übereinstimmung bestand zwischen Elektronenmikroskopie und kürzlich durchgeführten Untersuchungen an derselben Matric unter dem Mikroskop. Diese Methode ermöglicht es, eine neue Hypothese über die Bildung des peritubulären Dentins aufzustellen.
Researches on Structural Factor Involvement in Oral Tribology
This study is focused on two ceramic materials, D.SING (Ivoclar) and VM13 (emphasis the VITA TN), frequently used in restorative dentistry practice and it comes to complete a full set of results obtained by the authors over several years of research on oral tribology with main influence on oral health. In this way there are involved more specific structural aspects of dental restorative ceramic materials quality as is shown in [1].