摘要:

Remineralization experiments of bovine enamel with subsurface lesions were carried out with the use of a sandwich technique. The remineralizing solutions contained no or 2 ppm fluoride added to the solution. The amount of remineralization was determined after remineralization periods up to 324 h by means of quantitative microradiography. After 84 h the group with fluoride showed significantly (p < 0.05) less remineralization than the nonfluoride group. This inhibition of fluoride on the remineralization may be explained by the inhibiting effect that fluoride at certain concentrations has on the crystal growth of apatites.

ISSN:0008-6568    

DOI:10.1159/000261244

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

A possible mechanism of acquired acid resistance of lased enamel was proposed on the basis of the investigations of optical properties, compositional and structural changes and permeability of lased and unlased human dental enamel. Lased enamel showed a high positive birefringence, suggesting the formation of ‘microspaces’ in enamel. No new products were found, though a decrease of lattice strain and a slight a-axis contraction were recognized in lased enamel compared with unlased enamel. The contents of water, carbonate and organic substances were reduced in lased enamel. Gradual changes of birefringence were observed in lased enamel during treatment with acid solutions, and this change was attributed to mineralization of the microspaces. The ions released by an acid decalcification would be trapped in the microspaces in lased enamel, whereas such ions diffuse to the surrounding solution in unlased ena

ISSN:0008-6568    

DOI:10.1159/000261245

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The effect of a strontium-polyacrylate complex on fluoride uptake by bovine enamel was determined. A salivary pellicle was formed on sound enamel and enamel with artificially formed caries lesions. Ten specimens of each were treated with solutions containing (A) 225 ppm F, (B) 225 ppm F plus Sr complex, (C) 200 ppm F, 0.1 Mphosphate, pH 4.5 or (D) placebo for 1 h and then washed 24 h to remove labile fluoride. Analysis of ten thin layers of enamel showed that, on both enamel types, solution (C) deposited the largest amount of fluoride. The strontium complex decreased fluoride deposition, particularly in the outermost layer.

ISSN:0008-6568    

DOI:10.1159/000261246

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Mineral and fluoride concentration changes in the outermost layers of bovine enamel (depth less than 1 μm) were measured after demineralization in unbuffered hydroxyethylcellulose gels of pH = 5.4 with an intrinsic fluoride concentration of about 0.02 ppm. A combination of two nuclear analytical techniques, Rutherford backscattering spectrometry (RBS) and proton-induced gamma ray emission spectrometry (PIGE) was applied to determine the Ca/P molar ratios and F depth profiles, respectively. When compared to deeper layers, a reduced loss of mineral content is observed for the depth range of about 0–0.1 μm corresponding well with a F concentration increase from about 500 to about 5,000 ppm in the same range. These findings are interpreted as a fluoride-induced partial remineralization of the superficial surface layer during an overall demineralization proc

ISSN:0008-6568    

DOI:10.1159/000261247

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The effect of purified monofl·uorophosphate (MFP) on the formation of hydroxyapatite (HA) in supersaturated calcium phosphate solutions was determined. In solutions initially at pH 7.4 and seeded with HA crystals, MFP was hydrolysed to a small extent, releasing F––. Once the crystal growth-enhancing property of this F–– was compensated for, 4 mmol/l MFP could be shown to inhibit precipitation by 40%. Without compensation for F––, MFP appeared to inhibit precipitation by only 18%. This inhibition was weaker than that caused by pyrophosphate or ethane-1-hydroxy-11-diphosphonic acid. Because MFP is hydrolysed on apatite surfaces to F––, use of sodium MFP as an anticaries agent is unlikely to cause significant inhibition of enamel

ISSN:0008-6568    

DOI:10.1159/000261248

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The acid production from sorbitol and glucose was studied under anaerobic conditions in resting cell suspensions of bacteria from the predominant sorbitol-fermenting human dental plaque flora, belonging to the genera Streptococcus, Lactobacillus and Actinomyces. The acid production activity of the bacterial cells was followed by titration with alkali, at environmental pH 7.0, 6.0 and 5.0 after addition of carbohydrate solution. The metabolic end products formed in the suspensions were analyzed thereafter by isotachophoretic and enzymatic methods. The results showed that sorbitol was fermented at a slower rate than glucose. Lowering the environmental pH decreased the acid production activity from the two carbohydrates. Compared with glucose, the catabolism of sorbitol was affected to greater extent by the pH conditions. The total amount of acids formed from sorbitol was considerably less than from glucose. Lactic acid, which was the major end product in glucose-challenged suspensions, was produced only in low concentrations from sorbitol by all strains tested. The ratio strong (formic + lactic)/weak acids was moreover lower for sorbitol than for glucose. The present results further illustrate some of the mechanisms behind the low cariogenic potential of this sugar substitute.

ISSN:0008-6568    

DOI:10.1159/000261249

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Some antimicrobial compounds were tested for their antiplaque activity by a simple method involving measurement of the weight of Streptococcus sobrinus plaque on a glass surface. Chlorhexidine, cetylpyridinium chloride, and n-tetradecylamine reduced the weight of plaque produced by S. sobrinus in vitro; some N-palmityl and palmitoyl derivatives of polymethylenediamines were also found to possess antiplaque activity. The results suggest that an antiplaque effect does not necessarily depend on high bactericidal activity.

ISSN:0008-6568    

DOI:10.1159/000261250

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

This study was undertaken to determine the fluoride distribution in cementum and neighboring hard tissues of the rat after different levels of fluoride administration via the drinking water. Specimens of cementum with underlying dentine and adjacent bone were removed from the distal roots of the first lower molars. The fluoride distribution in each specimen was determined in samples removed sequentially using an abrasive microsampling technique. Fluoride concentrations were highest at or near the surface and decreased towards the interior of cementum, dentine and alveolar bone in both control and experimental groups. With increasing fluoride intake, concentrations increased throughout the tissue. The distribution patterns of fluoride in cementum of contralateral teeth from the same animal were similar. Fluoride concentrations in cementum were higher than those of dentine and alveolar bone.

ISSN:0008-6568    

DOI:10.1159/000261251

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Fasted Sprague-Dawley male rats were used in three experiments to determine the acute LD50 values of fluoride when it was administered intragastrically as NaF, disodium monofluorophosphate (Na2PO3F, MFP) or NaF and MFP. Another study was done to examine the relationship between the likelihood of a fatal outcome and peak plasma fluoride concentrations as well as 6-hour AUC values. It was concluded that fatalities due to the acute toxic effects of fluoride were: (1) independent of the chemical form in which it was given; (2) independent of the vehicle (dentifrice or water), and (3) not predictable in terms of a well-defined threshold range of peak plasma fluoride concentrations or AUC values.

ISSN:0008-6568    

DOI:10.1159/000261252

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000261253

出版商:S. Karger AG    

年代:1990

数据来源: Karger