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Biomedical subjects

R Legros

Publications and source records attributed to R Legros.

At least 37 records · Page 2Linked to original sources
PubMed1980

[Identification of the mineral constituents of various salivary calculi by study of their thermal behavior].

Studies of the physicochemical nature of five salivary calculi have shown that they are practically similar. They are composed of a nucleus and a shell which contain an organic phase and two crystalline mineral phases. These two phases are respectively a whitlockite and an apatite: the composition of the last agrees with the general formula: Ca10-(x+y) (PO4) T-(x+y) (CO3) x (HPO4) y (20H,CO3) (Formula: see text). The shell is different from the nucleus by the fact that it is less mineralized than the nucleus. The apatite of the shell contains more carbonate ions than the apatite of the nucleus.

Apatites↗
PubMed1980

[Crystal chemistry of two cases of subdeltoid calcification].

We studied the mineral phase of two cases of subdeltoid calcification by thermogravimetry, infrared spectometry and X ray diffraction. We have shown that these were phosphates deficient in calcium ions with an apatite structure. They contained both carbonate ions and HPO4 ions in variable proportions from one sample to another. These phosphates are very similar both by their structure and their composition to phosphates in bony tissue. They differ by the fact that they are better crystallised than the latter.

Adult↗
PubMed1978

Types of "H2O" in human enamel and in precipitated apatites.

Types of "H2O" in human enamel and in precipitated apatites are characterized using X-ray diffraction, infrared (IR) absorption spectroscopic and thermogravimetric analyses. Changes in lattice parameters (principally in the a-axis dimensions) and in the character of the IR absorption bands are correlated with weight losses at pyrolysis temperatures of 100 degrees to 400 degrees C and with effect of rehydration and reignition of previously ignited samples. This study demonstrated that the loss of "H2O" below 200 degrees C is reversible and causes no significant change in the lattice parameter of these apatites, whereas loss of "H2O" between 200 degrees and 400 degrees C is irreversible and causes a contraction in the a-axis dimension. It is proposed that two general types of "H2O" are present in these apatites: (a) adsorbed H2O--characterized by reversibility, thermal instability below 200 degrees C, and lack of effect on lattice parameters; and (b) lattice H2O--characterized by irreversibility, thermal instability between 200 and 400 degrees C, and induction of expansion in the a-axis dimensions of human enamel and precipitated apatites. Lattice H2O is assumed to be due to H2O-for-OH and/or HPO4-for-PO4 substitutions in these apatites. Loss of adsorbed H2O caused sharpening of the OH absorption bands in the spectra of these apatites. Loss of lattice H2O caused the appearance of P-O-P absorption bands (due to the presence of P2O74- group) in precipitated apatites containing small amounts of CO32-.

Adult↗