First experimental evidence for human dentine crystal formation involving conversion of octacalcium phosphate to hydroxyapatite.

Biological apatite-crystal formation is a complex process starting with heterogeneous nucleation of inorganic calcium phosphate on an organic extracellular matrix [Cuisinier et al. (1995), J. Cryst.

High resolution electron microscopy: structure and growth mechanisms of human dentin crystals.

Biological crystal formation was postulated to begin by a nucleation process. Such processes have been demonstrated for human amelogenesis and bone mineralization. The aim of this study was to confirm if such mechanisms occur during dentin crystal formation.

Ultrastructural aspects of the intact titanium implant-bone interface from undecalcified ultrathin sections.

An osseointegrated oral implant with surrounding bone was used for electron microscopical analyses of the implant-bone interface. The bulk metal was removed by sawing and grinding techniques, leaving only the plasma-sprayed titanium coating anchored in mineralized bone. Ultrathin sections were realized from these reduced interface areas and underwent ultrastructural and crystallographic assessments.

Dental status and fluoride consumption among five-year-old schoolchildren in Strasbourg, France.

An epidemiological survey of the caries prevalence in 1743 five-year-old children was conducted in Strasbourg in 1991 and compared with a similar study performed in 1973 (Jung et al, 1975). In 1991, 44.2 percent of the children were caries-free and 3 percent of the sample had experienced extractions of carious primary molars.

Kinetics of exchange processes in the adsorption of proteins on solid surfaces.

The homogeneous exchange process whereby IgG molecules adsorbed onto latex particles are replaced by IgG molecules from the bulk solution was studied by means of 125I radiolabeling. The exchange mechanism was investigated on surfaces saturated with either labeled or unlabeled proteins in the presence of a solution of the opposite species in two sets of independent experiments. After rinsing of the surface by pure buffer followed by supplementary IgG adsorption, the exchange process followed a kinetic law of first order with respect to the IgG molecules from the bulk solution, and the apparent exchange rate constant was (2.

Caries prevalence in 6- to 15-year-old French children based on the 1987 and 1991 national surveys.

The caries prevalence in a multi-stage probability sample of 18,786 children representative of all French children 6-15 years of age was studied in 1991 and compared with the results of a similar survey made in 1987. A significant decline in dental caries in France became evident. This decline, observed in primary as well as in permanent teeth, was of variable magnitude among the different age groups.

Atomic force microscopy study of human tooth enamel surfaces.

Human enamel features from individual crystals up to prisms were observed by atomic force microscopy (AFM). Low magnification images of vestibular tooth surfaces show the existence of enamel prisms appearing as deep holes. Individual, parallel enamel crystals show lateral faces elongated and formed by the (100) planes of hydroxyapatite (HA).

Human amelogenesis: high resolution electron microscopy of nanometer-sized particles.

Growth of inorganic crystals of enamel is described as a two-stage process with growth of ribbon-like crystals in length and width, followed by their development in thickness. In early stages of crystal growth during human amelogenesis nanometer-sized particles with a mean diameter of 1.1 nm were described between ribbon-like crystals.

Critical analysis of an experimental set-up generally used for the permeability evaluation of dental lining material.

The diffusion constants of iodide through dentine membranes were determined. The DI-values were within the range generally obtained by other investigators. When the estimation of the diffusion coefficient through a well defined polycarbonate membrane was calculated the value was strongly affected by the diffusion through the unstirred diffusion layer.

Competitive adsorption of human immunoglobulin G and albumin: consequences for structure and reactivity of the adsorbed layer.

The affinity of polyclonal anti-IgG for human IgG adsorbed on silica surfaces was investigated by two complementary techniques, scanning angle reflectometry and 125I radiotracing. Special attention was paid to compare the reactivity of IgG adsorbed directly or by exchange with already adsorbed albumin. In particular it was shown that (i) in the first case (direct adsorption) the reaction between anti-IgG and adsorbed IgG was in the ratio 1:1 and (ii) in the second case (adsorption by exchange) there was no reaction.

Human amelogenesis. I: High resolution electron microscopy study of ribbon-like crystals.

Ribbon-like crystals, from developing enamel of human fetuses, were studied by high resolution electron microscopy. These crystals were classically described as the first organized mineral formed during amelogenesis. They were characterized by a mean width-to-thickness ratio (W.

Adsorption/desorption of human serum albumin on hydroxyapatite: a critical analysis of the Langmuir model.

We studied the adsorption of human albumin onto synthetic hydroxyapatite, using a radiotracer technique and a special flow cell. Adsorption was studied under various conditions corresponding to different thermodynamic paths. It appears that (i) as is the usual case, the isotherms obtained within a short time range (a few hours) do not correspond to a true equilibrium situation; (ii) when the adsorption process is followed for longer times, which is necessary at low bulk concentrations, one always reaches the plateau surface adsorption; (iii) this plateau value is independent of the "history" of the adsorption process and corresponds well to the jamming limit predicted by the random sequential adsorption model; and (iv) surface denaturation, leading to enhanced surface binding and thus decreasing desorption constants, is the important phenomenon that can partly and qualitatively explain our observations.

[The effect of an experimental occlusal interference on the masticatory cycle recorded by electromagnetic pantography].

The effects of occlusal interference on masticatory cycles have been studied in twenty nine volunteers with complete natural dentition, using an electromagnetic pantograph (Sirognatograph, Siemens A.G.).

[Behaviour of gingival elastic constituents in periodontal disease].

Disorganization of gingival elastic constituents, including oxytalan fibers, elaunin fibers, and mature elastic fibers, is a feature of periodontal disease. In early stages where inflammation is moderate, this disorganization involves only oxytalan fibers. As the disease progresses, fragmentation and lamination of elaunin fibers and mature elastic fibers is seen.

[Types of interbacterial coaggregation in dental plaque].

Scanning electron microscopic observations of teeth-gingiva fragments removed among children or dogs made an important contribution to our knowledge of the composition of the microbial flora in gingival crevice. It was possible to appreciate special relationships between forms as "corn-cob" or "bristle brush" arrangements. The development of these formations were observed: coccal form apposition preceded corn-cob organization; abundant extra-cellular amorphous material preceded bristle brush arrangement.

Development of elastic-system fibers in human vocal cords.

The morphogenesis of elastic fibers in human, fetal and adult vocal cords was studied by light microscopy and transmission electron microscopy. The elastic system includes elastic, elaunin and oxytalan fibers at different stages. The development of elastic-system fibers in human vocal cord is characterized by every stage of maturation, whether normal, stifled or accelerated, according to areas.

[Epidemiologic study of dental caries in the school population of the provinces of Ille-et-Vilaine, Eure, Orne, Calvados and Manche].

An epidemiological study of 1,063 schoolchildren aged 6 to 15 years, from the Departments of Ille et Vilaine, Eure, Orne, Calvados and Manche was conducted of dental caries prevalence and incidence according to sex and urban or rural origin of the children. The DMFT index was respectively 0.34, 2.

Biochemical study of whole saliva from children with chronic renal failure.

The biochemical composition of unstimulated whole saliva was studied on ten children suffering from chronic renal failure and who, at the same time, displayed a very low caries activity. Various salivary components were studied before (T) and after (To) dialysis and were compared with similar elements of a control group, as well as with blood values. A mean salivary urea concentration of 513 +/- 210 mg/100 ml was found prior to dialysis, whereas after treatment this value dropped to 241 +/- 82 mg/100 ml, about twice as much as in the control group, 110 +/- 48 mg/100 ml.