Electron probe micro-analysis of human dental pulp stones.

The mineral composition of ten human dental pulp stones presenting various morphological aspects has been studied by electron probe micro-analysis. The denticles were composed of two major chemical elements: Ca and P with mean concentrations 32.12% and 14.69% respectively giving a Ca/P weight ratio of 2.19 which is very close to the weight ratio of pure stoichiometric hydroxyapatite (2.15). The concentration of some other elements was much lower (0.88% for F; 0.75% for Na; 0.51% for Mg). The other analysed constituents (K, Cl, Mn, Zn, Fe) were present at trace concentrations. The mineral composition of sound human dentine from one tooth containing a pulpal calcification was also analysed for comparative purpose.

Scanning electron microscopic study of pulp stones in human permanent teeth.

Scanning electron microscopy was used to examine pulp stones which are small calcified formations found in the coronal and/or radicular part of the dental pulp. Pulp stones range considerably in size and shape. Most are round or oval but others can be irregular and may correspond to a reduced duplicate of the pulp chamber anatomy. Both free and attached pulp stones were observed. The surface aspect was variable and frequently exhibited large resorption zones. Three characteristic features were observed on fractures: a) no characteristic organization where the mineralized mass is compact and homogeneous, b) a concentric architecture around an initiating central core, and c) a linear orientation along the pulp axis showing mineralized fibres and vessels. The findings suggest that the presence or absence of tubules should not be the sole factor for denticle classification since tubules can be also observed in "false" pulp stones. Cellular oval lacunae connected by long extensions were also found. Various stages of mineralization were seen, in particular, a deposition of fine needle shaped crystals on a collagenous matrix, and the fusion of numerous small calcospherules to the mineralized mass.

SEM contribution to the morphological study of dental structures in ovarian cystic teratoma.

This study in scanning electron microscopy (SEM) was carried out to observe the possible pathologic aspect of five teeth grossly arranged in normal sequence and of their surrounding tissues, found inside an ovarian cystic teratoma. Though the general morphology of the teeth was nearly normal, several anomalies affected the different mineralized dental tissues such as enamel hypoplasia, irregular growth of cementum, altered predentin layer, and immature osteofibrous bony outgrowths.

[Scanning electron microscopic study of keratohyaline granules in the oral epithelium of rats]. / Etude au microscope électronique à balayage des grains de kératohyaline de l'épithélium buccal du rat.

Scanning electron microscopy of rat buccal epithelium on deparaffinized or epon-etched sections provided observations of intracellular structures especially of keratohyaline granules. Cell-walls and nuclei were easily observable and the two types of keratohyaline granules already seen in transmission electron microscopy were identified namely intracytoplasmic or intranuclear single granules and composite granules with a heterogeneous structure which appeared clearly in the scanning method. Tridimensional information from scanning electron microscopy adds significantly to knowledge of keratohyaline granules morphology, so far studied with the transmission method only.

[The role of hypocalcemia on cell renewal and migration in the oral epithelium of the rat]. / Rôle de l'hypocalcémie sur le renouvellement et la migration cellulaire de l'épithélium buccal du rat.

Calcium plays an important role in phenomena relating to permeability and regulation of the extracellular compartments. The diffusion anomalies of sulphur previously observed in the oral epithelium of the hypocalcemic rat could possibly be attributed to a reduction in diffusion of sulphur related to disturbances in cellular renewal. The injection of H3 thymidine was used to compare in parathyroidectomized and control rats the resultant differences in DNA synthesis and the migration of labelled cells. The labelling indices showed the absence of any relation between DNA synthesis and a calcium deficiency, whereas, on the contrary, hypocalcemia should produce modifications of the labelled cell distribution in the control and experimental rats. This difference indicates a reduction in cellular migration in case of hypocalcemia.

[Role of hypocalcemia in the keratinization of the epithelium in the rat]. / Rôle de l'hypocalcémie dans les phénomènes de kératinisation de l'épithélium chez le rat

The role of calcium in the keratinization process has been studied in hypocalcaemic rats after surgical removal of the parathyroids. Intraperitoneal injection of Na2(35) SO4 allowed the study of the incorporation of sulphur in palatal and gingival epithelium. After parathyroidectomy, the calcaemia decreased strongly in the first week, reached its lowest value at the end of the second week and then increased progressively. In the control rats, the concentration of the silver grains increased from the basal layer to the stratum corneum, whereas in the parathyroidectomized rats the grains were concentrated in the basal layers. The variations of the values of the calcaemia and the number of grains were in correlation for the palatal and gingival epithelium. This correlation seemed to be confirmed for the palatal epithelium by the results obtained by radioactivity measurements. A relation between the calcium plasmatic concentration and the sulphur incorporation seemed to be confirmed. The hypocalcaemia was accompanied by diffusion anomalies of sulphur and glycoaminoglycans sulphation.