摘要:

69 streptococcal strains were freshly isolated from human dental plaque and tested for production of antagonistic substances on solid and liquid media under anaerobic conditions. Various bacteria from oral and non-oral origin were used as indicators. Production of, and sensitivity to antagonistic substances appeared to be species-dependent characteristics. Many Streptococcus mutans strains were antagonistic against other oral streptococci and actinomyces. Many Streptococcus salivarius strains inhibited oral streptococci, but not actinomyces. Streptococcus sanguis strains were relatively inactive as producer of antagonistic substances. The production of antagonistic substances was dependent on nutrient limitation. In broth cultures activity could be detected only rarely. Most of the products of S. mutans and S. salivarius were sensitive to proteolytic and sometimes also to lipolytic enzymes. A study of interactions among 46 S. mutans and 71 S. sanguis strains showed that strains isolated from the same plaque sample were slightly less antagonistic to each other than strains from different sites. The role of bacteriocins in regulating dental plaque flora in vivo is discussed.

ISSN:0008-6568    

DOI:10.1159/000260276

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Lactoperoxidase was shown to be adsorbed by human salivary sediment and hydroxyapatite. Phosphate ions (0.5 M) effectively regained the adsorbed activity while sodium fluoride (1 mg/l) was less effective. 45% of the total activity was adsorbed by salivary sediment in whole saliva solution and 64% in distilled water. In case of hydroxyapatite the respective values were 97 and 93%. The adsorbed peroxidase was shown to be antibacterial in the presence of cofactors, SCN–– ions and H2O2. The complete lactoperoxidase system inhibited remarkably the acid production of dental plaque when compared with the cont

ISSN:0008-6568    

DOI:10.1159/000260277

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

In vitro, xylitol was not fermented by S. mutans and A. viscosus and had no effect on cell growth. Xylitol neither interfered with the utilization of sucrose by the two bacterial species nor inhibited bacterial colonization of rat molar surfaces in sucrose-containing broth. In a rat caries test, xylitol added to starch diets and starch-sucrose diets did not affect formation of bacterial agglomerates on rat molars. Rinsing with 10% xylitol solutions did not interfere with early plaque formation in young adults consuming their habitual diet. Telemetric recordings of interdental plaque pH showed that 10% xylitol rinses and xylitol chewing gum were non-acidogenic. Xylitol did not prevent rapid sucrose glycolysis. In a 40-day rat caries test, xylitol was non-cariogenic and seemed to reduce the cariogenic potential of sucrose administered simultaneously, however, the animals consuming xylitol diets suffered from severe diarrhoea and gained less weight. In another experiment, rats drank less when xylitol was added to the drinking water.

ISSN:0008-6568    

DOI:10.1159/000260278

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

To investigate the mechanism of lesion remmeralization, artificial (HEC) lesions in bovine enamel were remineralized in a pH and pF-stat controlled system at 37 °C. In all experiments 5 cm2 lesion was immersed in 12.5 ml of a solution containing 2 mM Ca, 1.2 mM PO4 and either·or 1 ppm F at pH = 7.0. The mineral deposition was followed by monitoring the alkali and fluoride uptake and the solution calcium and phosphate concentration changes. From the ratio of the deposited ions (Ca/PO4, Ca/F, Ca/OH, etc.) and from the analysis of the lesion material after remineralization (IR data, X-ray diffraction), the conclusion can be drawn that the material deposited is most likely (fluoridated) hydroxyapatite (HAP). SEM experiments show that a crystalline material is deposited during remineralization, with rod-like crystals having a diameter of 200 nm. The addition of 1 ppm F to the remineralizing solution causes an about twofold increase in rate of remineralization thus comparable with previous studies of the remineralization of acid-etched enamel. Hardness experiments indicate that during the deposition studied a rehardening of the body of the lesion occur

ISSN:0008-6568    

DOI:10.1159/000260279

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

The effect of Sr and F uptake on powdered enamel and its subsequent resistance to solubility was studied. Varying concentrations of SrCl2 and NaF solutions were used over a 24-hour period. The mean Sr and F concentrations in enamel increased with the concentration of the SrCl2 and NaF immersion solution. The F concentration of enamel treated only with NaF was generally higher as compared with that of the SrCl2 pretreated enamel. No relationship was evident between the SrCl2 concentration of the solution used and the subsequent F uptake of the enamel. Strontium chloride treatment increased enamel solubility and sodium fluoride treatment decreased enamel solubility. Treatment with high Sr concentrations was less damaging than treatment with low concentrations. However, the degree of solubility of the enamel powder which incorporated the largest amount of Sr was still significantly higher than that of the untreated enamel. In most cases, subsequent use of fluoride further decreased the damaging effect of Sr but Sr-F treatments were never as good as fluoride treatments alone.

ISSN:0008-6568    

DOI:10.1159/000260280

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Tangential sections cut from six sound human premolars were imbibed in water, air and Thoulet solution, in order to investigate the influence of form birefringence, intrinsic birefringence and crystallite orientation on total birefringence. Quantitative microradiographic and scanning electron microscopic techniques were used to obtain information about the volume percentage mineral and the direction of the prisms. The results indicate that there is a positive linear correlation between the mean total birefingence and the mean volume percentage mineral occiusally. In the cervical area there is no such correlation and the influence of the prism direction is more marked. The range of the total birefringence values is lower than normal due to the influence of the prism direction in these tangentially cut sections.

ISSN:0008-6568    

DOI:10.1159/000260281

出版商:S. Karger AG    

年代:1977

数据来源: Karger