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At least 19 recordsLinked to original sources
PubMed1975

Composition and structure of dental enamel: elemental composition and crystalline structure of dental enamel as they relate to its solubility.

The same elements, 21 in number, were found in both acid-resistant and acid-susceptible enamel specimens by ion microprobe analyses. However, there were differences in the concentrations of 14 elements between groups. Of the 16 trace elements found in enamel, the concentrations of K, F, and Na in parts per million were the greatest. Enamel surface analyses showed V and Zn were more concentrated in acid-resistant specimens by factors of 7.4 and 6.1 respectively, followed by nine other elements, the last molybdenum, that were just slightly more prevalent in acid-resistant enamel. Four elements were equally concentrated in both groups of samples, and only one trace element, B, was more abundant in the acid-susceptible samples by a factor of ten. Ca and P were predominantly more abundant in acid-resistant speciems, and C, H, and O were more concentrated in acid-susceptible samples. The enamel substance in acid-resistant and acid-susceptible groups was found to be similar by these methods. --Ion microprobe: the same elements were detected in both groups. Four trace elements (titanium, lead, Cl, and lithium) were equally abundant in the two groups. --Electron diffraction: the crystal structure type was the same in both groups of samples. --Infrared absorption: the crystalline substance showed the same spectra in both groups. The enamel substance in the two groups of specimens was found to be dissimilar by these methods. --Ion microprobe: the concentrations of 11 trace elements as well as Ca and P were greater in acid-resistant enamel. The concentrations of C, H, O, and B were greater in acid-susceptible enamel. --X-ray diffraction: crystallites in the acid-resistant specimens were larger by a factor of more than two. Enamel solubility appears not to be related to atomic species but associated with one, some, or all elements quantitatively and also with its physical form (crystallite size and probably density).

Calcium Phosphates↗
PubMed1978

[Thermic behavior of dental enamel, dentin and selected dental materials].

The linear coefficient of expansion of enamel, dentin as well as selected dental working materials is estimated by means of holographic-interferometric measurements. A good correlation was found between hard dental texture and a phosphate glass envisaged for use with lasers. The possible effects of the greatly increased coefficient of expansion of tested composites is discussed.

Biophysical Phenomena↗
PubMed1976

[REM and Hommel tester studies of the dental enamel surfaces after removal of dental calculus with 2 different scalers].

Removal of gingival calculus was performed with two different scalers on teeth that had been extracted previously. Using scanning electron microscopic prints and the Hommel tester, it was demonstrated that the dental surface had obtained a clearly visible roughness. This is determined by the dental surface, the compressive strength and the characteristics of the various scalers. The use of a Tompkin reamer to smooth the surface produced even deeper criss-cross grooves than the scaler, and not a satisfactory smooth surface.

Dental Calculus↗
PubMed1979

[Late development of human dental enamel].

Planes of longitudinal fractures of human dental enamel observed in scanning electron microscopy showed morphological variations related to age. This late maturation was observed along the enamel sheaths which disappeared in the subsurface and decreased in the rest of the structure. The destructions produced by demineralizing substances (phosphoric acid, citric acid, EDTA) were always more severe in enamel of older teeth when compared to younger samples. A pretreatment of the fragments with a urea solution increased the acid effects only in young enamel. It is suggested that the late maturation of enamel consists in a reduction of matrix components.

Acid Etching, Dental↗
PubMedDate not supplied

[Participation of protein-lipid complexes in the mineralization of dental enamel].

Insoluble complex protein-lipid-calcium phosphate was formed on neutralization of dental enamel solution. Nonpolar lipids were extracted by chloroform-methanol mixture; the phospholipids maintained their connection with the solid phase. After incubation of the enamel precipitate with an anionic detergent the enamel protein became solubilized and was studied by means of electrophoresis. The role of proteins and lipids in calcification of the dental enamel is discussed. Biological calcification appears to operate via a universal mechanism, as evidenced by similarity in molecular structures of organic mixtures of various mineralized tissues.

Amelogenesis↗
PubMed1977

Luminescence quantum yields of sound and carious dental enamel.

The absorption and emission spectra of slabs of human and bovine dental enamel were determined. The absorption and scattering coefficients and emission quantum yields were computed according to theoretical models. The samples were gradually demineralized. The absorption, scattering, and emission parameters were determined as a function of the demineralization time. Using the theoretical models combined with the experimental values, ratio of the visible and UV luminescence, and the decrease of visible emission intensity upon demineralization are explained.

Absorption↗
PubMed1976

[Ultrastructure of conditioned enamel surfaces and their adhesive matrices in dental enamel sealing].

The enamel sealant Nuva Seal was tested in model tests on caries-free human molars and premolars. Under the scanning electron microscope the acid-etched enamel areas (natural and ground surfaces) and the corresponding Nuva Seal matrices were studied. In the evaluation, the surface reliefs of the objects were compared. Thus, information on flow capacity, wetting and polymerization behavior of the adhesive was obtained. Evaluation of pairs of stereo pictures of the inverse surface reliefs in the enamel/adhesive contact zone suggests that the sealant has an average measurable depth of penetration of 7 mum. Peg-shaped elevations 10-20 mum in size that can sometimes be observed in the Nuva Seal impressions are interpreted as representing enamel defects.

Bicuspid↗
PubMed1975

The absorption and scattering of light in bovine and human dental enamel.

The reflectance and transmission of thin slabs of dental enamel has been measured at all wavelenghts between 220 and 700 nm by means of an integrating sphere. From the results the true scattering and absorption coefficients have been computed. The theoretical model used is an extended two-flux model, which is presented and discussed. The absorption spectrum of the dissolved organic component of enemel was also determined. An absorption peak at 270 nm is common to all the spectra. This peak in the bovine enamel spectrum is about three times as high as in the spectrum of human enamel. The peak of the dissolved material is about as high as the peak of the corresponding enamel. Hence it is concluded that the organic component, presumably aromatic amino acids, is responsible for most or all of the observed optical absorption.

Absorption↗
PubMed1977

Improved adhesion of acrylic restorative materials to dental enamel by precoating with monomers containing phosphonate groups.

The adhesion of acrylic composite restorative materials to etched dental enamel is increased by a factor of two or more when the enamel is coated with a thin layer of vinyl-benzyl phosponic acid (VBPA) prior to forming the enamel-restorative bond. The present results support the suggestion that the enhanced adhesion is attributable to bonding between calcium ions in the enamel surface and phosphonate groups in the VBPA.

Acrylic Resins↗
PubMed1976

Fluoride reactions with dental enamel following different forms of fluoride supply.

The reactions with dental enamel of NaF as tablets dissolved in different beverages or supplied with NaCl, simulating domestic salt fluoridation, were studied in tests with enamel surfaces and enamel powder. It was confirmed that powdered enamel can react quite differently from enamel surfaces under certain conditions. Enamel surfaces took up much more fluoride (F) from orange juice than from water or milk, and neither the low pH nor the citrate content of the juice increased the formation of unstable CaF2 in the enamel, as judged from a KOH leaching test. The F uptake by enamel surfaces from 0.25 mM NaF in 175 mM NaCl, corresponding to a dish prepared with salt containing 500 parts/106 F, was about 80% greater than from the same NaF concentration in water. This NaCl concentration did not increase the formation of CaF2 in the enamel, as judged from the KOH test, while 350 mM NaCl caused a moderate increase. The investigations support the administration of NaF tablets with orange juice and plans for domestic salt fluoridation.

Adult↗
PubMedDate not supplied

Composition of fluoridated dental enamel studied by x-ray photoelectron spectroscopy (ESCA).

A combination of ESCA and argon-ion etching has been shown to be effective in determining the surface and subsurface composition of dental enamel. The heavy organic coating on enamel has been investigated. Beneath this coating, untreated enamel was found to have invariant phosphorus and calcuim concentrations over the region surface. The surface of enamel treated with an acid phosphate-fluoride gel was shown to be almost entirely connected to calcium fluoride. A phosphate species, noncalcium and possibly a sodium salt, was found to be present in the surface layer. At a depth lower than about 60 nm, there was a gradual increase in phosphorus concentration that approached the value for untreated enamel with increasing depth. The increasing phosphorus and decreasing fluorine concentrations were primarily caused by the increasing concentration of unreacted hydroxyapatite. These results have shown that ESCA coupled with argon-ion etching, can be used effectively to examine the surface and subsurface composition of dental enamel. The surface sensitivity, ability to strip thin layers of material, sensitivity to low atomic weight elements, and ability to differentiate between different oxidation states makes a combination of these two techniques extremely useful for dental research.

Acetates↗
PubMed1976

[Effect of an electric field on the penetration of fluorides into dental enamel, studied in vitro and in vivo].

The aim of the present study is to determine the influence of iontophoresis on the deposition of fluorine in dental enamel. A micromethod of fluorine-deposition and of dental enamel-sampling was perfected in vitro; it was then applied in vivo. Fluorine was layed down by topical and iontophoretical way, under the form of sodium fluoride in neutral solution. In in-vitro and in 2 in-vivo asseys 18F was used as an indicator, while in other ones fluorine was titrated by mean of a specific lanthan-fluoride electrode. Results from both methods agree. It is stated that the fluorine deposition on enamel remains lightly but significantly higher, in vivo as well as in vitro, when the tooth is subjected to a continuous electrical field.

Adolescent↗
PubMed1976

[Sealing dental enamel by means of photopolymerisable adhesives under exposure lasers light].

Electronmicroscopic examinations - analogous to those of the previous investigation [4] - suggest a relatively good interlocking of the adhesive with the conditioned dental enamel. In the demineralized microsections, clear differences are found among the strands of resin, in the light microscope. While they reach a length of 10 to 20 mum after UV light polymerisation, they become 100 to 200 mum long after exposure to laser light. First advantages resulting from these experiments are explained and critically discussed.

Dental Enamel↗