Fluorine deficiency

B. Selenium in the form of selenocysteine is required for three enzymes that remove iodide from thyroid hormones. There are no signihcant areas in which dietary intake of sodium or potassium are problems. Fluorine deficiency is not associated with thyroid hormone metabolism. 

Fluorine-Deficient Discharges and Etch Rate Selectivity... 

The mechanism we believe is responsible for the large SiOj-to-Si etch-rate ratios which have been obtained in fluorine-deficient discharges is based on several experimental observations. First of all, it has been shown that there are several ways in which carbon can be deposited on surfaces exposed to CF, plasmas. One way is to subject the surface to bombardment with CF ions which are the dominant positive ionic species in a CF plasma. The extent to which this can occur is shown by the Auger spectra in Fig. 3.3. Curve (a) is the Auger spectrum of a clean silicon surface and curve (b) is the Auger spectrum of the same surface after bombardment with 500 eV CFj" ions. Note that the silicon peak at 92 eV is no longer visible after the CFj bombardment indicating the presence of at least two or three monolayers of carbon. Another way in which carbon can be deposited on surfaces is by dissociative chemisorption of CFj or other fluorocarbon radicals. 

It is our current opinion that all etching anisotropy or directionality is caused by energetic particle bombardment (primarily ions but in some cases, electrons). Other factors such as the degree of fluorine deficiency in the discharge can influence the... 

Fig. 3.3 Skeletal and joint deformities of a fluorine-deficient goat. 

The impressive damage of the front legs and their joints of older fluorine-deficient... 

Anke M, Groppel B and Krause U (1991d) Fluorine deficiency in goats. In Momdlovic B, ed. Trace Element in Man and Animals - 7, IMI, Zagreb 26 -28-26-29. 

Hypofluoric status, fluorine deficiency in humans, is characterized, along with tooth decay, by the development of osteoporosis (Gabovich and Ovrutskiy 1969). In the first case, acid environment is created by osteo-cytes in the second case, by bacteria populating the surface of tooth enamel. Attention should be paid to the role of bacteria in the development of caries, as disturbed microflora of the mouth cavity seems to be one of its prerequisites. Up-to-date methods of tooth decay prevention (toothpastes, pills) combine the eflfects on the enamel structure and tooth tissue in general, and on the microflora that causes acidity at the points of its location. In this respect, the adaptation of microorganisms to particular fluorine levels is most likely the phenomenon of most significance. 

Now as before, the various forms of tooth decay and osteoporosis each point at fluorine deficiency in humans as being a causative factor. In this respect, the fluoridation of public water supplies and use of fluorine-containing substances are recommended. Dental mottling is a sign of subtoxicity that is related to excessive fluoride intake. Fluorine concentrations below 0.3-0.5mgL indicate a risk of hypofluoric status, as a water level of 1.5 mg L can cause fluorosis, especially in regions with a hot climate... 

Even given the excess of F in the structure the theory of the distorted tetrahedron is not universally accepted. Regnier et al. (1994) used FTIR spectroscopy, NMR, and quantum mechanical calculations on synthetic and natural samples to demonstrate that the repulsion between the F anion and the carbonate anionic complex is too great to form the distorted tetrahedron. They do not dismiss the possibility that F couples with COs to balance the charge, but that if they do both enter the structure, the F enters independently and fills a vacancy in the structure. Nathan (1996) however points out that all of the samples used in these experiments are actually fluorine-deficient apatites and thus unlikely to have the COsF pseudo-tetrahedron, so clearly more research is needed before final judgments can be made. 

Apatites in the hydroxyl-fluor-carbonate apatite series that are only slightly fluorine deficient have a-di-mensions in the ipper rar e of excess-fluorir e francolites (s9.360-9.370A). The carbonate apatites in this series that are assumed to be highly OH substituted have a-dimensions similar to those measured for pure igneous hydroxylapatite (9.410-9.430A) or carbonate-hydroxyl-apatites (9.430A). Perhaps due to a limited sample base. 

Absorption, Metabolism, Excretion Functions of Fluorine Deficiency Symptoms Interrelationships Recommended Daily Allowance of Fluorine Toxicity... 

D. J. M. Bevan, O. Greis, Fluorine-deficient tysonite-type solid solutions (Ca,Ln)F3 and related superstructure phases Ca3Ln7F27, Rev. Chim. Miner., 15, 346-359 (1978). 

Significance.—Fluorine contributes to the hardness of the skeleton, especially the teeth. There are minimal and optimal concentrations in the dietary, beyond which conditions of fluorine deficiency and fluorine poisoning, respectively, are observed. Concentrations of NaF above 0-05 per cent, in the diet of the rat cause pathological over-development of tooth enamel, and defective dentition. 

Polymer films deposited by this procedure were transparent or yellowish this last color has been understood previously as indicating fluorine deficient materials. ... 

One should then consider the fact that the fluorine deficiency can be caused by a fluorine scavenger at high CF4 concentration. 

---