64 research outputs found
The influence of fluoride on in vitro remineralization of bovine enamel
Remineralization experiments using bovine enamel were carried out with 2 ppm fluoride or no fluoride added to the remineralizing solutions.The group without fluoride showed (quantitative microradiography) significantly more remineralization in the first 50 ”m of the lesion than the fluoride group.It is suggested that fluoride may inhibit remineralization.Une expĂ©rimentation portant sur la reminĂ©ralisation de lâĂ©mail a Ă©tĂ© menĂ©e sur de lâĂ©mail bovin, en utilisant des solutions de reminĂ©ralisation sans adjonction de fluorure et avec adjonction de 2 ppm de fluorure.La microradiographie quantitative a montrĂ©, dans le groupe sans fluorure, une reminĂ©ralisation plus importante, dans les premiers 50 ”m de la lĂ©sion, que dans le groupe avec fluorure.Ces rĂ©sultats suggĂšrent que les fluorures puissent inhiber la reminĂ©ralisation
A systemic approach to the oral problem of mandibular resorption
It is argued that mandibular resorption can be considered as osteoporotic in nature. This calls for a systemic approach in its treatment. One aspect mostly neglected is the tendency of bone to bind calcium and phosphate ions. A direct measure for this tendency is the difference in pH between the bone extracellular fluid and blood plasma. This pH difference is directly reflected by the degree of saturation of blood plasma with octocalcium phosphate. Calculation of these degrees of saturation of about 2000 data of blood plasma compositions given in the literature indicates that calcitonin injection, estrogen replacement and magnesium supplementation increase the tendency of bone to bind calcium and phosphate ions and hence should be used in the therapy of mandibular resorption and of bone resorption in general.Il est prouvĂ© que la rĂ©sorption mandibulaire peut ĂȘtre considĂ©rĂ©e comme Ă©tant de nature ostĂ©oporotique.Ceci veut dire que le traitement doit ĂȘtre systĂ©mique. Lâun des aspects souvent nĂ©gligĂ©s est la tendance quâa lâos Ă fixer les ions calcium et phosphate. Une mesure directe de cette tendance est obtenue par la difference de pH entre le fluide extracellulaire de lâos et le plasma sanguin. Cette diffĂ©rence de pH est directement rĂ©vĂ©lĂ©e par le degrĂ© de saturation du plasma sanguin par rapport au phosphate octocalcique. Le calcul de ce degrĂ© de saturation sur environ 2000 donnĂ©es de compositions plasmatiques fournies dans la littĂ©rature indiquent que des injections de calcitonine, lâĂ©quilibration en oestrogĂšnes et un apport de magnĂ©sium augmentent la tendance de lâos Ă fixer les ions calcium et phophate et, par consĂ©quent, devraient ĂȘtre utilisĂ©s pour la thĂ©rapie de la rĂ©sorption mandibulaire et de la rĂ©sorption osseuse en gĂ©nĂ©ral
Some physical properties of Na- and CO3-containing apatites synthesized at high temperatures
The structure of manganese-iron-oxygen spinels
The positions of the metal ions in the spinel-type structures of compds. of the type MntFe3-tO4 in the region 0.25 <t <1.50 were detd. by the method of Skolnick, et al., (CA 52, 9750h) which employs the diffraction of x-rays of different wavelengths. After a single-phase spinel has been formed by solid-state reaction of Mn and Fe oxide mixts., a change in the distribution of cations during heating still occurs. The time needed for reaching the equil. state of the distribution of cations depends on the compn. The final structure of samples quenched from 1000 Deg and from 1400 Deg, both with the compn. MnFe2O4, is different. The relation between position and valence of the cations is discussed
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