Characterization of lymphocyte subpopulations in periapical lesions by flow cytometry.

The mechanisms by which the bacterial root-canal infection leads to periapical bone destruction (cysts or granulomas) are not yet well understood. Previous works have shown elements of an active immune response in the lesions. In the present study, flow cytometry was used to improve the characterization of immune cells. Semiquantitative immunohistochemical analysis showed the presence of plasma cells, macrophages and B and T cells. The simultaneous use of several antibodies in flow cytometry allowed a more precise phenotype of the lymphocytes. The cysts displayed an abundance of B lymphocytes at the same time as a relative scarcity of CD8+ cells. CD4+ lymphocytes were the dominant lymphocyte population in most cases. A small number of gamma delta T lymphocytes and natural killer cells was found. These preliminary results show that flow cytometry may be used to characterize immune cells from inflamed tissue and opens the possibility for further functional studies.

Relationship between endodontic preparations and human dentin permeability measured in situ.

Endodontic preparations may induce changes in the permeability of radicular dentin. The aim of this study was to analyze the variation of hydraulic conductance measured in situ after three endodontic preparations (manual K+H files, ultrasonic preparation, and manual with NaOCI and EDTA). Scanning electron microscopic analysis of the canal walls was made to permit correlations between variations of permeability and the amount of surface covered with smear layer or organic debris. There was an inverse relationship between the variations in dentin permeability and the presence of smear layer. The significance of this correlation was variable according to the techniques used. Dentin thickness was as significant a factor in influencing radicular permeability as was the smear layer. The use of EDTA induced a considerable increase in radicular permeability. The use of ultrasonics produced a similar but weaker effect.

Migration of a Streptococcus sanguis strain through the root dentinal tubules.

The persistent presence of bacteria in the root canal system often leads to the failure of treatment. The aim of this study was to study the in vitro penetration of root dentinal tubules by bacteria. Bovine dentin was inoculated with a strain of Streptococcus sanguis, NCTC 7863; samples were taken at 10, 20, and 28 days, and bacterial penetration of the tubules was demonstrated using two techniques, scanning electron microscopy and light microscopy after Brown and Brenn staining. The results showed that S. sanguis can penetrate deep inside the tubules (792 microns). The maturity of the dentin blocks seems to be a major factor in tubule penetration.

[The effect of the magnification ratio on 2 methods of computerized image analysis in scanning electron microscopy]. / Influence du rapport d'agrandissement sur deux méthodes d'analyse informatisée d'image de microscopie électronique à balayage.

The aim of this study is to compare two computerized analysis methods of SEM dentinal walls views. The first technic is an indirect one using a primary marking and a secondary measurement. The second one is a direct threshold analyse, using the grey levels selection. The influence of the magnification is analysed in a second part. The first technic is considered as a reference one. The results show that the threshold measurement technic is only reliable at a high magnification. A direct surface measurement cannot be used at a low magnification. A pretreatment could enhance the ability of a computer to measure the areas covered with smear-layer or organic debris on SEM micrographs.

[Removal of two calcium hydroxide preparations: S.E.M. study]. / Elimination de deux présentations d'hydroxyde de calcium: étude en M.E.B.

Calcium hydroxide is one of the most often medication used for temporary treatment in endodontics. Different forms of preparation are available. The aim of this study is to evaluate in vitro the elimination of the pharmaceutical and the commercial forms of presentation. The aspect of the dentinal walls were analysed using SEM and X-ray microanalysis. The results show that Ca(OH)2 removal is difficult but there is no significant difference of elimination between the two forms.

[Interpretation of S.E.M. images using a treatment system and image analysis: preliminary study]. / Interprétation des images de M.E.B. à l'aide d'un système de traitement et d'analyse d'images: étude préliminaire.

The scanning electron microscope has multiple applications in the research of endodontics, but there are not standard methods for the evaluation of the results. The use of the computerized processing and analysing systems for the images reduces the sources of error due to the subjectivity of the operator. This first part, after the introduction of the principles of processing and analysis, puts in view two methods of computerized analysis used in the study of the films of dentinal walls in the scanning electron microscope.

[The tooth-amalgam joint: the role of the marginal bevel]. / Joint amalgame-dent: rôle du biseau périphérique.

Three amalgams, Standalloy, Dispersalloy and Formibel are used to fill class I cavities (bevelled or not) and applied over fresh-removed wisdom teeth. Macroscopic examination with a binocular lamp shows a better marginal adaptation of amalgams when cavity walls and edges have no asperity nor bevel and regardless of the quality of the amalgam. This MEB examination reveals a gap at dentinal level that might result from the vacuum processing of the samples.