摘要:

The adherence of 4 strains of oral bacteria to hydroxyapatite and to chemically modified hydroxyapatite was investigated in vitro. It was found that successive treatment of hydroxyapatite beads with potassium phytate and hexadecylamine lead to complete inhibition of the adherence of three Gram-positive strains, Streptococcus mutans, Streptococcus sanguis and Actinomyces viscosus, but not of the Gram-negative Fusobacterium strain. Coating of the hydroxyapatite surface with saliva prior to treatment with phytate and amine did not significantly change bacterial adherence. When phytate and amine-treated hydroxyapatite was post-treated with saliva, the adherence of S. mutans and A. viscosus, but not of S. sanguis, was still completely blocked.

ISSN:0008-6568    

DOI:10.1159/000260739

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

In this study a buffer system containing calcium and phosphate was used to produce caries-like lesions. The influence of the pH on the lesion characteristics was investigated. The degree of saturation with respect to hydroxylapatite and the concentration of the undissociated acid were kept constant. The pH was either 4.0, 4.5, 5.0 or 6.0. The lesions were examined microradiographically. The lesion characteristics studied were: the mineral content of the surface layer; the mineral content of the body of the lesion; the depths at which these mineral levels were reached, and the depth of the lesion. The most important influence of the pH was that on the rate of demineralization. A striking phenomenon was the sudden change in the rate at which the different levels of demineralization were reached. In solutions with a pH lower than or equal to 4.5, the time needed to reach a certain demineralization was considerably shorter than for solutions with a pH higher than or equal to 5.0.

ISSN:0008-6568    

DOI:10.1159/000260740

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Inhibitory effect of sodium saccharin in concentrations from 10––5 to 10––2M was tested on glycolytic enzymes involved in phosphate transfer in cell-free extracts of Streptococcus mutans NCTC 10449. In the presence of 10––2M sodium saccharin the enzymes hexokinase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate mutase, pyruvate kinase, 3-phosphoglycerate kinase and phosphofructokinase were inhibited 58, 45, ∼16, 12, 3 and 1.4%, respectively. 10––3–10––2M sodium chloride produced little if any inhibition of the gl

ISSN:0008-6568    

DOI:10.1159/000260741

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

In this paper the interaction of urea on plaque-free sound human enamel is described. In 1 week urea penetrates in the enamel several hundred micrometers. It weakens or destroys part of the peptide structure, especially interprismatically. Urea does not or not measurably attack the organic matrix between the crystallites. Due to the urea interaction organic material normally plugging natural defects in the enamel surface, especially in the perikymata, is removed.

ISSN:0008-6568    

DOI:10.1159/000260742

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The purpose of this long-term study was to investigate disturbances in enamel mineralization associated with low, but relatively constant, plasma fluoride levels produced by constant infusion or with fluctuating plasma fluoride levels caused by drinking fluoridated water. Weanling rats were raised for 8 weeks on low-fluoride food and water containing 0, 10, 25 or 60 ppm fluoride. Two other groups received their fluoride from subcutaneously implanted minipumps. The daily fluoride exposure of the two latter groups was 0.14 and 0.32 mg/day, while that of the 10-ppm water group averaged 0.41 mg/day. The terminal plasma fluoride levels of the 10-ppm water group was 3.0 μM, and of the two minipump groups were 1.5 and 3.1 μM, respectively. The mandibular incisor enamel in each of these groups showed microradiographic evidence of fluorotic changes which was most severe in the minipump group with an average plasma fluoride concentration of 3.1 μM. The disturbances in enamel mineralization were most apparent in the 25- and 60-ppm water groups. There were no differences among the groups for plasma calcium concentrations. The findings suggest that: (1) enamel fluorosis has a time component in addition to a concentration or intake component; (2) the rat incisor is a better model for human enamel fluorosis than heretofore believed, and (3) disorders in calcium homeostasis are not necessarily involved in enamel fluoros

ISSN:0008-6568    

DOI:10.1159/000260743

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Root surfaces of teeth extracted because of periodontal disease were evaluated with microradiography for their resistance to acid in vitro. The roots were compared in two categories: (1) surfaces exposed to the oral environment in periodontal pockets versus those unexposed, (2) surfaces exposed in periodontal pockets and scaled versus surfaces exposed in periodontal pockets and root-planed. In addition, three commonly used fluoride topical treatments were evaluated for their effectiveness in increasing the resistance of root surfaces to acid demineralization. The acid challenge was 0.01 M lactic acid buffer, pH 4.0, in 1% carboxymethylcellulose, containing 3.0 mM calcium and 1.8 mM inorganic phosphate, at 37 °C. Root surfaces exposed to the oral environment were more resistant than unexposed surfaces. Scaled roots were more resistant than those which were root-planed. All fluoride treatments increased the resistance of root surfaces to acid in vitro, and contributed to the formation of a thick layer of high mineral density over the body of the lesion

ISSN:0008-6568    

DOI:10.1159/000260744

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The effect of fluoride on the formation of calcium phosphate on an anionpermselective membrane was studied at near-physiological temperature and pH. The fluoride-free precipitate comprised petal-like flaky crystals. When 1 ppm of fluoride ions was added to a phosphate solution, the precipitate contained crystals of two different shapes, flaky and plate-like. With 10 ppm of fluoride, thicker plate-like crystals were formed after 5 days of incubation. X-ray diffraction patterns of all samples were characteristic of calcium apatites. No extraneous peaks due to octacalcium phosphate or dicalcium phosphate dihydrate were found.

ISSN:0008-6568    

DOI:10.1159/000260745

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Acid production from glucose and isomaltulose (Palatinose®) in dental plaque suspensions was studied before and after subjects rinsed their mouths 6 times daily for 6 weeks with a 15% w/v isomaltulose solution. The mean acid production from isomaltulose, expressed in percent of that from glucose, increased significantly (p < 0.01) after the rinsing period. In vivo plaque pH changes caused by a mouth rinse with 10 ml of a 15% w/v glucose or isomaltulose solution were determined also, before and after the rinsing period. The pH decreases from isomaltulose were significantly more pronounced after the rinsing period (p < 0.01) and the raw pH values were about 0.57 units lower than before (p < 0.001), but never below pH 6.2. Isomaltulose was considerably less acidogenic than glucose before as well as after the isomaltulose rinsing period (p < 0.001)

ISSN:0008-6568    

DOI:10.1159/000260746

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The aim of the study was to examine the effect of enamel lipids on the rate of progress of artificial carious lesions in dental enamel. Lipids were extracted from cut halves of human tooth crowns. Artificial carious lesions were formed in both lipid-extracted and control halves in a lactate-diphosphonate system over 2, 1, 14 and 21 days at 37 °C. A twofold increase in lesion formation rate occurred in the lipid-extracted teeth compared to the normal teeth. The lipid component of enamel apparently acts as a diffusion barrier during the enamel caries process, and inhibits demineralization

ISSN:0008-6568    

DOI:10.1159/000260747

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The potential toxicity of fluoride application can be reduced by using lower fluoride concentrations. A previous study has shown that 0.4% F–– and 1.2% F–– organic fluoride gels were equally effective in preventing demineralization in both sound and primed human enamel. In this study 0.4, 0.1 and 0.01 % F–– amine fluoride and acidulated phosphate fluoride (APF) solutions were tested to see whether a further reduction in concentration was possible. All amine fluoride groups and 0.4% F–– APF showed significantly shallower lesions than controls. Lesion depth in both amine fluoride and APF groups increased with decreasing F–– concentration. APF groups showed a tendency for deeper lesions than amine fluoride groups. All fluoride groups showed significantly higher minimum vol% mineral in the subsurface lesion than the controls; these values decreased with decreasing F–– concentration. It can be concluded that under these experimental conditions adequate protection against further acid attack was provided by 0.4% F–– amine fluoride followed

ISSN:0008-6568    

DOI:10.1159/000260748

出版商:S. Karger AG    

年代:1984

数据来源: Karger