High Fluoride Exposure Research Articles

Physiology and pharmacology of hard tissues--effect of chemicals on the formation and the resorption mechanism of tooth and bone

This review described the effects of several drugs on the formation and the resorption mechanism of tooth and bone. The enamel formed during high fluoride exposure showed marked hypocalcification, and the organic substances appeared on the incisors in these regions. Such changes following fluoride administration appear to indicate an inhibition of the mineral deposition and/or an inhibition of organic matrix withdrawal. The successive bisphosphonate (HEBP) injections reduced both the progress of the mineral deposition and the formation of the enamel matrix. Colchicine showed a remarkable inhibitory effect on the matrix-forming cells of the dentin and enamel in teeth through its striking inhibitory action on the cytoskeletal system and secretary function. The dentin formation in rabbit and rat incisor dentin was reduced markedly. Colchicine induced reparative dentinogenesis in dental pulp and ectopic calcification in the bone marrow. Both sodium salicylate and aspirin reduced dentin formation through a mechanism that reduces the incorporation of collagen precursors into odontoblasts. Sodium salicylate also inhibited the growth of the upper jaw and tibia in rats. The recruitment of osteoclast-like multinucleated cells was inhibited by sodium salicylate in vitro. A pharmacological approach for studying the formation and resorption mechanism of hard tissue is useful tool for developing hard tissue research.

High Fluoride Exposure in Hemodialysis Patients

The observation of higher plasma flouride levels in our hemodialysis (HD) patients than our continuous ambulatory peritoneal dialysis (CAPD) patients (4.0 +/- 0.5 mumol/L [n = 17] v 2.5 +/- 0.3 mumol/L [n = 17], P less than 0.005) prompted an evaluation of fluoride metabolism during HD. We found that serum fluoride was completely ultrafiltrable across cuprophane membranes (99% +/- 4%) and that HD produced acute changes in plasma fluoride levels that correlated well with the fluoride gradient between plasma and dialysis fluid at the start of dialysis. Our HD fluids contained significantly higher fluoride concentrations than were present in commercially prepared peritoneal dialysis fluid. Our fluids are prepared from fluoridated tap water that is purified by reverse osmosis (RO). We conclude that the different concentrations of fluoride in our dialysis fluids account for the differences in the plasma flouride concentrations between our dialysis groups. Since many HD units rely on RO systems to purify fluoridated tap water, it is likely that many HD patients are being exposed inadvertently to increased concentrations of fluoride.

Scanning electron microscopical study on the fluorosis of enamel in rats.

Sixteen 28-day-old male rats of Wistar strain, with a mean body weight of 179 g, were divided into two equal groups. Each group of eight animals was maintained for 70 days on drinking water, ad lib., containing no fluorine (control group) and 100 ppm of fluorine (experimental group). All specimens examined were obtained from the incisal portions of the incisors. The following types of enamel specimens were prepared for scanning electron microscopy: (1) acid-etched specimens; (2) acid-etched specimens followed by low temperature microincineration; and (3) fractured specimens. The enamel formed during high fluoride exposure showed marked hypocalcification, that is, the crystallite density in the prism core and interprismatic region was lower than that of control animals. The organic substances appeared to increase in these regions. The changes were prominent in the outer and middle enamel layers. Such changes following fluoride administration appear to indicate an inhibition of enamel maturation, that is, an inhibition of the mineral deposition and/or an inhibition of organic matrix withdrawal.

Effect of long-term administration of fluoride on physico-chemical properties of the rat incisor enamel.

Rats were maintained on drinking water containing different amounts of fluoride (0, 9, 23 45, 68, and 113 ppm) for 70 days. Physico-chemical properties of the incisor enamel were examined after fluoride administration, using contact microradiography, histochemistry, and microhardness tests. The tooth enamel formed during high fluoride exposure showed marked hypocalcification. Much of organic substance in the enamel seemed to have been retained. In addition, the microhardness of enamel showed a marked decrease. These changes were most prominent in the outer region of enamel and were proportional to the concentration of fluoride administered. Such changes following fluoride administration indicated inhibition of enamel maturation, i.e., an inhibition of the progressive depposition of minerals and/or in inhibition of organic matrix withdrawal by ameloblasts. Enamel seemed more affected by fluoride than dentine.