The effect of fluoride pretreatment and ascorbic acid on bone growth in tissue culture

Effects of fluoride intake on the mineral content, acid solubility and resorption caused by experimental periodontitis of rat alveolar bone

Adult rats were given either distilled water or drinking water containing 100 parts/10(6) of fluoride. The alveolar bone of rats given fluoride for 90 days showed an increased mineral content and decreased acid solubility compared to the bone of rats given distilled water. Experimental periodontitis was initiated in both groups after 110 days of treatment to cause alveolar bone resorption. Fourteen days later, the rats were killed and it was found that the alveolar bone resorption caused by experimental periodontitis was significantly smaller in the rats given fluoride in their drinking water than in those given distilled water. The findings suggest that fluoride intake might have a protective effect on rapidly progressing alveolar bone resorption.

The effect of local controlled release of sodium fluoride on the stimulation of bone growth

This study was performed to test the feasibility of using a biodegradable delivery system for the local controlled release of sodium fluoride as a mechanism for the stimulation of local bone growth. Sodium fluoride grains were mixed with poly-DL-lactic acid (PLA), and the mixture was then dissolved in acetone. After driving off the solvent, sheets of this material were rolled into rods 3.2 mm in diameter and 28.6 mm long. These were inserted into the intramedullary canals of the right femora of adult New Zealand White rabbits. A sham implant, made the same way but containing no fluoride, was inserted into the contralateral left leg. The effects of three different concentrations of sodium fluoride, 0.125 g NaF/g PLA, 0.250 g NaF/g PLA, and 0.500 g NaF/g PLA, were determined after a 4-week implantation period. In a second set of experiments, the concentration was fixed at 0.500 g NaF/g PLA with implantation durations of 4, 8, and 16 weeks. Expressed in terms of property ratios (experimental/control), bending strengths of the femora were significantly raised in most groups with the notable exception of Group 3 (0.500 g NaF/g PLA, 4 weeks). Cross-sectional area ratios in the distal femora were increased in all groups compared to right/left values for a normal unoperated group (p less than 0.05), with the highest ratio being 1.50 (SD = 0.44) for Group 4 (0.500 g NaF/g PLA, 8 weeks). Only Group 4 animals showed significant (p less than 0.05) increases in midshaft area ratio and none had responses proximally. Growth rates, measured by sequential fluorochrome labeling of bone followed the area ratio data and were only significant for the distal femora.

Short-term effects of fluoride on biosynthesis of enamel-matrix proteins and dentine collagens and on mineralization during hamster tooth-germ development in organ culture

The effect of various concentrations of fluoride (F-) on cell proliferation, matrix formation and mineralization was examined in hamster molar tooth germs in premineralizing and mineralizing stages. The exposure lasted 16 h (mineralizing stages) and 24 h (premineralizing stages) and the F- levels ranged from 2.63 microM to 2.63 mM; [3H]-thymidine, [3H]-proline, 45Ca and 32PO4 were used as markers for cell proliferation, matrix formation and mineralization, respectively. The proline-labelled amelogenins were isolated by sequential extraction with water and formic acid and their nature examined by SDS-urea-polyacrylamide electrophoresis. Digestion by collagenase was used to assess the amount of proline incorporated into collagens. F- in concentrations up to 1.31 mM inhibited neither biosynthesis of DNA and amelogenins, nor synthesis of collagens and their hydroxylation. Amelogenins extracted from F- induced, non-mineralizing enamel matrix had the same electrophoretic mobility and the same degree of phosphorylation as amelogenins from normal, mineralizing enamel. However, F- increased the uptake of 45Ca and TCA-soluble 32P dose-dependently, starting with 52 microM. Thus, interference with secretion of enamel matrix by F- takes place at much lower concentrations than required to inhibit biosynthesis of enamel matrix.

Effect of fluoride on protein and collagen biosynthesis in rabbit dental pulp in vitro

The time course for incorporation of KC-proline into various fractions of rabbit dental pulp in vitro has been measured. In the TCA-soluble precursor pool a steady state level of activity was indicated upon incubation after 3 h, whereas incorporation into protein and 14C-hydroxyproline, i.e. collagen formation, increased linearly for 9 h, leveling off upon further incubation. A lag period of about 3 h was indicated for the appearance of high molecular weight 14C-activity, including 14C-hydroxyproline, in the medium, increasing linearly from 3 h to the end of the incubation period (22 h). In this system, fluoride exhibited a dose-dependent inhibitory effect. At 5.3 mM fluoride the uptake of 14C-proline into the TCA-soluble pool was inhibited by about 50%, and the incorporation into protein and the subsequent conversion to hydroxyproline by about 90 and 60%, respectively. Release of collagen, i.e. 14C-hydroxyproline-containing material, seemed to be the process most sensitive to fluoride; it was inhibited by about 50% at the lowest concentration (1.3 mM) tested.

Histologic and histometric study of the effect of fluoride on the rat mandibular condyle

The effect of fluoride on the rat mandibular condyle was studied histologically and histometrically. The condyles of the rats that received 50 ppm fluoride in the drinking water for 17 weeks did not differ in structure from those of the control rats fed tap water containing 1 ppm fluoride. However, the condyles of the rats given 100 ppm fluoride in the drinking water for the same period showed a significant increase in both the thickness of the cartilage layer (P smaller than 0.02) and the density of cancellous bone (P smaller than 0.01) when compared to the controls. The thickening of the cartilage layer was due to an increase in the number of hypertrophied chondrocytes. The trabeculae of cancellous bone were thicker and consequently the bone marrow spaces were extremely reduced. The trabeculae contained more calcified cartilage in their cores.