摘要:

Cells of cariogenic Streptococcus mutans (Ingbritt) were maintained and grown in a Trypticase-Phytone-based medium which contained either glucose, xylitol or their combinations as the added carbohydrate. 2.5% xylitol retarded the growth of the cells in the presence of 0.25% glucose, but during 2.5 months adaptive period the cells were able to tolerate the presence of xylitol. However, no evidence was obtained in 10 months of a possible adaptation to metabolize xylitol. Instead, indications of an adaptation to metabolize other compounds (for example, amino acids or peptides) were obtained. Xylitol had no strong effect on the uptake of glucose by the cells which were adapted to tolerate this polyol. 3% xylitol inhibited by 40–50% the activity of dextran-hydrolyzing extracellular enzyme(s) in the growth medium of the above cells in the conditions used. The extracellular polysaccharide-forming activity by the cells was increased 60–80% by low concentrations of xylitol (up to 55 mg/ml growth medium). Higher concentrations were inhibit

ISSN:0008-6568    

DOI:10.1159/000260156

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The present study describes the histological features of enamel in teeth showing either mild or severe fluorosis. Sections were examined in transmitted and polarized light after imbibition in aqueous media or alcohols and quinoline. For semiquantitative study contour maps were prepared. Furthermore quantitative imbibition studies were performed along a traverse through the enamel and at selected points. From the values of total path difference, birefringence was calculated and imbibition graphs drawn. Finally, contact microradiographs were made. The study showed that it is only possible to correlate the degree of histological change with clinical features in severe cases of dental fluorosis. The general morphology of fluorosed enamel does not differ from normal enamel, but the tissue comprise areas of diffuse hypomineralization. In polarized light, opposite to microradiography, much more extensive changes were observed. Thus, slight degrees of dental fluorosis were recorded only when using polarized light. In severe cases, a maximum degree of 25% porosity or more were recorded and located immediately deep to a well-mineralized enamel surface. In severe cases of fluorosis, only dark zones were observed when examined in quinoline, and the quantitative imbibition studies showed that the enamel in these cases reacted similar to what is described in initial caries lesions. In both slight and severe dental fluorosis the subsurface porous region behaved as a ‘mixed body’ in aqueous media, but when examined in alcohols, these could only penetrate the tissue completely in severe cases. Thus, in mild dental fluorosis the subsurface region behaved as a ‘molecular sieve’. The findings in the present study are correlated to previous observations of enamel formation in order to explain the pathogenesis of dental fl

ISSN:0008-6568    

DOI:10.1159/000260157

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Washed cells of the FA-1 and K-1 strains of Streptococcus mutans were incubated in buffered solutions, pH 5.9, that were initially either saturated or slightly undersaturated by adding enamel granules. In the presence of enamel in the system, the total cell phosphorus of the nonfermenting cells was higher than in the absence of enamel. This change was reduced by fluoride and a fluoride-propanol combination. When 32P-labelled cells of Strep. mutans were introduced into the above system, a part of the 32P of bacterial origin was found in the enamel. Fluoride alone and in particular fluoride together with propanol or chlorhexidine increased the uptake of bacterial 32P by the enamel. During prolonged incubation of bacteria with softened enamel, the fluoride, especially together with chlorhexidine, caused a marked rehardening of the enamel surface.

ISSN:0008-6568    

DOI:10.1159/000260158

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

A new acid etch enamel microsampling technique was employed to study the effect of artificially produced acquired pellicle on fluoride uptake. The results showed less variance of parts per million fluoride and shallower depth than previously reported acid etch methods. The results of 120 enamel microsamplings showed that all enamel blocks receiving an acidulated fluoride treatment gained significant amounts of fluoride, with the highest concentration found in the groups not exposed to artificial pellicle. No significant difference in fluoride uptake was found between the group brushed with water after pellicle formation and the group which received a pumice prophylaxis after pellicle formation. Fluoride binding to salivary proteins was investigated to determine whether it could be a factor in fluoride measurements of surface enamel and whether the binding might decrease the amount of fluoride reaching the enamel. Salivary residues deposited on Millipore filters showed no measurable binding of fluoride at NaF range from 2 × 10––6 to 2 × 10––3

ISSN:0008-6568    

DOI:10.1159/000260159

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The ability of an epidemiological diagnostic system to distinguish tooth sites with carious cavities from those without was investigated. The diagnostic data were obtained during annual clinical and bitewing radiographical examinations of 551 teenage clinical trial subjects. 109 premolars and permanent molars, extracted during subsequent treatment of the subjects, were kept. Undecalcified serial sections of these teeth were examined in water at × 2.5 magnification under incident light, to compare the original diagnostic findings with the histological extent of caries. Quantitative methods were used to estimate the concurrent validity of clinical diagnosis of pits and fissures and the radiological diagnosis of posterior approximal surfaces. For fissure diagnosis a validity coefficient (rt) of 0.83 was obtained. 84% of cavities were detected while 22% of sites without cavitation were wrongly diagnosed as having cavities. For radiological diagnosis the validity coefficient (rt) was 0.95. Although 97% of surfaces without cavitation were correctly identified, only 73% of approximal cavities were detected radiologically. The effect of different factors on the validity findings is considered

ISSN:0008-6568    

DOI:10.1159/000260160

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260161

出版商:S. Karger AG    

年代:1975

数据来源: Karger