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Two combined scanning electron microscopic methods including modified fixative procedures were used for studying the morphologic aspects of the odontoblasts and the corresponding dentinal wall at different endodontic levels. The odontoblasts were tightly packed in the pulp horn, where they assumed pear-shaped profiles and, from crown to apex, successively looked spindle shaped, club shaped, and globular. Their number decreased in the pulp radicular portion, where the interglobular spaces were enlarged. The filling fibrillar material varied from crown to apex. A globular circumpulpal dentin was observed at all levels of the root canal. The tubule openings varied in number and size.

A combination of preventive methods have been used to reduce dental caries in children aged 7-8 at baseline, living in a non-fluoridated area in the West of France. The preventive program involved a daily supervised toothbrushing at school with 180 mg of fluoridated toothpaste, professional prophylaxis every 2 months with topical application of fluoride gel and reinforced motivation. The oral hygiene level was measured using the Silness-Löe plaque index and caries were recorded using the def and DMF surface indices, including incipient lesions. The 3-yr results showed a significant 52% plaque reduction in the test group compared with the control group. Caries reduction was significant at the 0.01% level: 44% for primary teeth and 60% for permanent teeth.

The present paper using classical and transmission electron microscopy brings the first data on the pulp of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits). The pulp of the fangs of Viperidae shows a poor collagen and fibroblast content and a high developed vascular system. The odontoblasts are polarized, with a high organelle content. The interconnections are constituted of lateral "gap junction" systems. At a late secretion stage, the odontoblastic processes show a poor cytoplasm, mainly constituted of microfilaments.

The repairing effects of vit. D3 and vit. D3 sulfate upon the hard tissues of vit. D3 deficient pigs have been studied using SEM and electron microprobe analyses. It was demonstrated that a vit. D3 therapy could balance lesions induced by vit. D3 deficiency. The effects of vit. D3 sulfate were not so clear. Results obtained were varying, sometimes similar to those obtained with vit. D3 but not always statistically significant. The rate of mineralization of dentine and bone was higher in animals having received vit. D3 and vit. D3 sulfate compared to the deficient group. In dentine and bone, the Ca/P ratio, thus the crystalline phases, wee modified, which was not the case for enamel and acellular cementum. It was shown that dentine and bone, which both include cells and cell processes in the calcified matrix, undergo similar modifications in the course of vit. D3 deficiencies and their therapy. On the contrary, enamel and acellular cementum in vit. D3 deficiency presented a lower rate of mineralization without any structural defects or modifications in Ca, P, Mg and F- ratios. Repair of lesions due to vit. D3 deficiencies by vit. D3 and, to a lower degree, by vit. D3 sulfate, concern, in order, bone, dentine, cementum and very little enamel.

The ultrastructural and chemical differences between mature enameloid and dentine in the teleost fish Lophius were demonstrated using transmission (TEM) and scanning (SEM) electron microscopy, X-ray diffraction analysis, electron diffraction analysis and electron microprobe analysis. An enameloid cap (about 50 micron thick) and a thin layer (1 micron thick) of collar enameloid were revealed in the scanning (SEM) and transmission (TEM) electron microscopes. Collar enameloid, structurally different from dentine both in SEM and TEM, proved to be less mineralized than the cap as revealed by electron microprobe analysis. The enameloid cap was seen to differ from dentine by (i) its electron density in TEM; (ii) the structural arrangement perpendicular to the underlying dentine, observed in SEM and TEM and corroborated by electron diffraction data, which showed a preferred orientation of enameloid crystallites; (iii) its higher F content decreasing gradually from the apex of the tooth to the junction with dentine and falling suddenly below this junction; and (iv) its lower Mg content. Establishment of a classification of enameloids is proposed, similar to that for dentines, in which selachian enameloid would be a reference standard.

In 1983 an investigation involving a homogeneous population sample from a western city of Burkina Faso has been performed in 1983 in order to estimate the oral health status of the population cut off from any dental assistance and to assess the importance of traditional practices in the city. The investigation, performed using World Health Organization techniques (WHO, 1977) involved 354 subjects, male and female, divided into age groups from 10 to 54. It was shown that: although the oral hygiene level was very low and no dental treatments were performed, caries level was very low--although gingivitis rate was high, advanced periodontitis rate was low--the frequency of interincisive diastema (one subject out of 4 in the 15-19 age group), the progressive decline of tooth cutting, a traditional practice, in town people but the large extent of cola use (one adult out of two). The present data will be used as base-line reference to evaluate the incidence of a dental care and prevention program which has just started in the same city of Burkina Faso.

In vitro caries-like lesion formation in F-containing tooth enamel (shark) showed a lower depth of penetration compared to that in human enamel (42 vs. 100%). After longer periods of exposure, the depth of penetration in shark enamel is only 33% relative to that in human enamel. The extent of dissolution in acetate buffer for powdered human enamel and for synthetic F-free calcium-carbonated-apatites was greater than for powdered shark enamel and for synthetic F-containing apatites. These results suggest that the cariostatic action of fluoride may be explained in terms of a combination of two effects: (a) the stabilizing effect against acid dissolution (caries) when fluoride is incorporated in the tooth mineral (apatite), and (b) a greater degree of remineralization (repair) in the presence of F solution.

The coronal pulps of four primary canines, free from radicular resorption, and of three primary teeth, with roots entirely resorbed, were prepared for electron microscopy. Mature fibroblasts, similar to those reported in the pulps of permanent teeth, were present in the pulps of the clinically mature teeth. Regression of fibroblasts, evident in the pulps of deciduous teeth at the root resorption stage, was characterized by cytoplasmic changes, modifications in the cytoskeleton and dissociation of cells and fibrils. Deciduous teeth might provide a model for studying pulp fibroblast ageing.

Dysplastic enamel and calcifications at the enamel surface in 7 odontomas were studied, using correlated light microscopy of decalcified and undecalcified material, microradiography and SEM. Much of the dentin in the odontomas was not covered with enamel. When present, the enamel was immature and assumed a prismatic structure. The prisms were irregular distributed and associated with spherical calcifications. The calcifications adhering to the enamel surface or separated from it presented variations in size, morphology, staining reactions and radiodensity. The correlated techniques of light microscopy, microradiography and SEM indicated that all the calcifications adhering to the enamel surface and part of those separated from it may be related to a pathological process of amelogenesis. Most of the calcifications separated from enamel and often formed around nidi of ghost cells, are the result of a dystrophic mineralizing process, definitely distinct from amelogenesis.

Light microscopy, microradiography, SEM and TEM of 4 tooth follicles in a 12-year-old caucasian girl presenting regional odontodysplasia showed widespread globular dentin, calcifications located in the enlarged pulp chambers, hypoplastic and hypomineralized enamel. Hypomineralized strands were sandwiched between two normal enamel layers, which indicates that amelogenesis, interrupted for a while, has once more become established. The enamel surface was covered with calcoglobules. Numerous rounded calcifications were scattered within the dental follicles. Some of these occurred in microfibrils (possibly oxytalan fibers), distinct from collagen fibers. Calcification of the sheath surrounding epithelial rests was a conspicuous feature. The fibroblasts in contact with calcifications developed numerous cytoplasmic extensions, which suggests that they may have assumed a phagocytosis behaviour.

An uncommon case of dentinogenesis imperfecta with dens in dente was studied by light microscopy, microradiography, and electron-microprobe analysis. Numerous canals and cellular inclusions were found in the coronal portion of the dentin where the tubules were sparse and irregularly distributed. In the radicular portion of the molar, large canals ran parallel to each other down to the apical region. The cementum was thinner and the Tomes granular layer greater in amount than usual. A dens in dente occurred in the radicular portion of the molar. It was located in a cavity and consisted of a mineralized cap of enamel, a spherical dentinal mass, and cellular cementum, located outside the cavity and in the "cervical" portion of the dens in dente.

An original method for fractionating and preparing isolated crystals of homogeneous size was developed. It was demonstrated that enamel apatite crystals are at least 100 micron long. The flexibility of the very long crystallites was demonstrated. Crystal curvatures, accounting for the irregular course of the prisms through the enamel thickness, were visualized and measured. It was shown that in the deep forming enamel layer, lateral branches may grow out of the crystals and crystal fusing often occurs, inducing the crystallites to assume pyramidal shapes with their wide bases pointing toward the dentino-enamel junction and one or two tops toward Tomes' processes. During the maturation process, the two tops of the still immature crystals also fuse so that the mature crystals acquire a rodlike aspect, with parallel faces and steplike graduations along the c axis, allowing a close contact between the crystals. These results support the hypothesis that the crystallites would be continuous from the dentino-enamel junction to the surface.

Microradiographs of a tooth affected by odontodysplasia showed a clear delineation between the hypoplastic enamel and dentin. Two different zones, one presenting a prismatic structure and the other a globular structure, were found in the enamel layer. In areas where normal prismatic enamel was found, a scalloped dentinoenamel junction and a normal mantle dentin layer were present. Crystallites in those areas were of normal size but the intercrystalline spaces were enlarged. Hypoplastic globular enamel consisted of smaller, closely packed crystallites resembling a type of enameloid found in teleost fishes. Round calcified bodies attached or unattached to the hypoplastic enamel were composed of still smaller irregularly distributed crystallites. It is suggested that the outer hard tissues in odontodysplasia involve different processes. The prismatic enamel zones are formed by the first differentiated ameloblasts. The hypoplastic enamel is due to a decrease in the number of ameloblasts. A localized loss of ameloblasts induces lack of enamel in places. The round calcified bodies attached or unattached to the hypoplastic enamel are most likely formed without any involvement of the ameloblasts.

Calcifications found in the coronal pulps of primary teeth extracted in an 8-year-old child were studied by TEM. Different types of relationship were observed between fibroblasts and pulp calcifications: extension of cell processes towards calcifications, modelling of the cells upon calcifications, internalizing process of calcifications. Fibroblasts proved to be able to enclose small pulp calcifications within intracytoplasmic vesicles. There was no evidence of any active role played by fibroblasts in the genesis of pulp calcifications. It was shown that collagen fibres could be involved or not in the mineralizing process. It is suggested that mitochondria might provide an adequate environment for initial mineralization. It is likely that the role played by the cytoskeleton in the internalizing process of calcifications is important.

The inorganic phase in dentin with dentinogenesis imperfecta was investigated, using the correlated techniques of high resolution TEM, X-ray diffraction analyses, infrared absorption spectroscopy, thermogravimetry, and chemical and electron microprobe analyses. It was shown that crystallites in dentin with dentinogenesis imperfecta are of normal size (from 3 to 6 lattice planes thick), but less numerous than in normal dentin. Electron microprobe analyses indicated significant differences in the mineral content of dentin with dentinogenesis imperfecta compared to normal dentin. A higher Ca/P ratio, a loss in Ca and P, and a severe significant loss in Mg, corroborated by chemical analyses, were recorded. The main component of the inorganic phase in dentin with dentinogenesis imperfecta was found to be poorly crystallized carbonated apatite. It is suggested that the water content, greatly increased in dentin with dentinogenesis imperfecta, is at least partly related to lattice water tightly bound to the inorganic phase.

The present study, using classical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, has shown the dental hard tissues of the fangs of Viperidae (poisonous serpents with terrestrial or semi-aquatic habits) to be constituted of: a calcified outer layer, 0.4 microns thick, made of very small needle-like crystals, randomly distributed. The calcified outer layer contains organic invaginations inducing pores at the surface and many collagen fibres incompletely mineralized, which may suggest enameloid. a calcified inner layer, in the wall of the poison canal. The calcified inner layer, 0.6 microns thick, is constituted of very small crystals, which are parallel to each other and perpendicular to the calcified outer layer. It might be the inner layer of enameloid, an orthodentine, whose tubules present a special lateral branching system resembling a fish bone. The TEM data, which show the dentine to be constituted of very small ill-defined crystals and incompletely mineralized collagen fibres are corroborated by chemical analyses which reveal a poorly mineralized apatite with high carbonate content.

Dental involvement in a case of congenital chloride diarrhea (CCD) was studied using light microscopy of decalcified and undecalcified sections, microradiography and TEM. Mixed enamel lesions were found, involving gross hypoplasia at the cuspal level and hypocalcification occurring all over enamel. The hypocalcification resulted in the immature aspect of the prismatic enamel, porosities, amorphous areas, prominent incremental lines and round-ended crystallites. A marked hypocalcification suggests a temporary break of amelogenesis likely related to acute episodes of the disease. Globular calcifications were associated with enamel formation. Dentinal hypocalcification was conspicuous and diffuse all over dentine. A globular mineralization pattern was revealed by the tretracycline (TC) stain which was well preserved in decalcified sections, thus indicating that TC uptake is related to the organic matrix. It is unlikely that TC alone is responsible for the hypocalcified areas which extended widely beyond the TC-stained bands. It is suggested that TC uptake only adds to dental defects induced by the metabolic troubles of CCD.

Two premolars removed from a 14 year old girl, with suspicion of pseudohypoparathyroidism (PHP) have been studied, using several of the correlated techniques applied to the study of calcified tissues (light microscopy, microradiography and scanning electron microscopy). Enamel gross and micro hypoplasia, hypomineralization of the enamel surface and dentin hypocalcification were similar to dental abnormalities observed in pseudohypoparathyroidism. Microradiography showed for the first time calcifications present in blood vessels of the dental pulp. Light microscopy and SEM revealed dystrophic globular calcifications within enamel hypoplastic pits. Cemental changes consisting of hypoplasia, aplasia, localized hyperplasia and cementicules were described for the first time. It is suggested that enamel, dentine and pulp abnormalities observed in the present case might be pathognomonic of PHP.

The lesion of microhypoplasia of an unerupted tooth was composed of small, irregularly distributed crystals, similar to those of immature and hypomineralized enamel. The lesion appeared to be a defect of crystal growth and maturation, probably involving a partial and momentary failure of the operating cycle of an ameloblast.

The effects of fluoride on human enamel and selachian enameloid in vitro were visualized in TEM and analyzed with electron diffraction. It is demonstrated that under precise pH conditions, inducing concentration balance between F-ions and apatite, calcium fluoride is no longer formed, and crystalline changes occur instead. A secondary growing process, inducing a twofold increase in crystal size, involves all crystal faces, altering the hexagonal symmetry. It is suggested that the mechanism involved is not a dissolution/precipitation process but rather a secondary growth of residual crystallites induced by apatite dissolution.

TEM, SEM and X-ray diffraction analysis demonstrate the heterogeneity of the dentinal tissue on Anarhichas lupus, a vascular osteodentine. The disordered aspect of collagen fibres, incompletely mineralized (the periodical striation being still visible), explains the scattered distribution of crystallites since they are responsible for their arrangement. The low degree of mineralization revealed by the visible collagen striation is confirmed by X-ray diffraction analysis (the crystallinity of vascular osteodentine being much lower than that of the peripheral dental tissue) as well as by high resolution TEM, since no lattice planes could be observed. Osteodentine, supporting bone and proper bone have in common a mineral phase, more or less organized, different from the apatite system.

Ion thinning technique applied to high resolution T.E.M. study of human dental enamel crystallites makes it possible to visualize a great number of dislocations. Dislocations proved not to be due to artifacts induced by the ultramicrotome diamond knife. They are related to the crystal apartite structure.

Structural, ultrastructural, microradiographic, and electron microprobe studies of an unusual case of odontodysplasia were performed. Two cusps were absent from one molar. Normal prismatic enamel and mantle dentin were present on the two others. The dentinal mass resembled osteodentin. The mineral content of enamel and dentin was decreased compared to that of the controls.

The effect of synthetic granular hydroxyapatite (HAP) on cultured fibroblastic cells (L929, human bone and gingiva cells) was studied. Phagocytosis of HAP particles and resulting morphological cell changes were demonstrated by microscopic examinations. Cell counts and [3H]thymidine uptake indicated significant increases in cell proliferation and DNA synthesis. These results could account for some of the alterations of the fibroblast behavior induced by changes in intracellular levels of calcium ions released from the material.

Soft-tissue calcifications of the dental follicle in regional odontodysplasia were studied via the correlated techniques of light microscopy, scanning electron microscopy (SEM), calcium x-ray cartography, and high-resolution transmission electron microscopy (TEM). The study revealed several types of calcification, mostly located within an area normally occupied by enamel formation. Some of them are produced without collagen being involved; others result from the mineralization of collagen fibers. Sometimes they were surrounded by a structureless homogeneous zone and resulted from the fusion of several smaller globules. High-resolution TEM revealed two different types of calcifications: a few composed of platelike crystallites, presenting a "sheath" characteristic of apatite formation, most of them poorly crystallized. The calcifications were in close contact with the cytoplasm of the neighboring connective tissue cells in which an abundance of microfilaments was found. It is suggested that these filaments might be involved in the formation of dystrophic soft-tissue calcifications.

Ghost cells in complex odontoma were studied by light microscopic and scanning electron microscopic examination of decalcified sections. They were found at different locations in odontomas: next to tubular dentin, at the site where enamel would be expected; adjacent to remnants of enamel matrix or surrounded by enamel matrix; within granular calcified masses in contact with bone or tubular dentin; in contact with ameloblasts or adjacent to small rests of odontogenic epithelium. They were either isolated or arranged in groups. Their cytoplasm presented a fibrillar component and a lack of keratohyaline. In a complex odontoma, ghost cell keratinization occurs as a result of metaplastic transformation. The calcifying process in these cells was found to be a passive one, with the cells becoming gradually entrapped within the calcified material--bone, osteoid, dentin, dystrophic osteodentin, or dystrophic granular or lamellar types of calcification. Complex odontomas contain both normal and metaplastic odontogenic epithelial cells, which may have lost their developmental and inductive properties.

Fragments of sound human molars were prepared for the scanning electron microscope (SEM) using modified fixative procedures and the carbon dioxide critical-point method to study the predentin-pulpal border zone. This technique minimizes the usual artifacts related to SEM procedures. The elongated odontoblast bodies are closely related to each other at the predentin level. For the first time in SEM procedures, the cell processes almost completely fill the predentinal tubules. Fibers measuring 0.3 to 0.5 micron in diameter are visible between the odontoblasts and fan out into the predentin. They correspond to the so-called Korff's fibers. Others, measuring less than 0.2 micron in diameter, are visible on the predentinal surface and follow the cell processes into the predentinal tubules. They correspond to nerve fibers. This study demonstrates that the proper use of improved SEM fixative techniques and the carbon dioxide critical-point method provides data on the relation between the different components of the predentin-pulpal border zone, which are in agreement with transmission electron microscope data.

Enamel pearls are small rounded or egg-shaped nodules which most frequently develop in the furcation area of molars. They may consist of enamel only or enamel containing a small core of tubular dentin. They often sit upon strands of cementum or Tomes granular layer. Histologically, the enamel surface of enamel pearls resembles immature enamel and may be covered with cementum. Small calcoglobules presenting varying degrees of organization are often found related to enamel pearls. Some of them, which have the same radiodensity as the enamel of the pearl and of the affected tooth, may be considered as an enamel-type of calcifications. Others, which present a concentric structure revealed by a polarization cross when viewed between cross polars, may be similar to cementicles. All calcifications located in contact with enamel pearls or at a distance, from them are dystrophic calcifications.