摘要:

Human molars were exposed to lactate buffers, pH 5.0, with or without diphosphonate (MHDP) for periods of 1 h to 10 days. Lesion progress was assessed by chemical analysis and polarized light microscopy. Mineral loss was initially similar with or without MHDP. Subsurface porosity increased in each system, in addition to surface etching which occurred without MHDP. The results from the two model systems suggest that initial opening up of the surface is a prior step to the subsequent progression of subsurface demineralization and eventual formation of the zones of the classical ‘white spot’ carious les

ISSN:0008-6568    

DOI:10.1159/000260824

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Crowns of human molars were exposed to lactate buffers, pH 5.0, with or without diphosphonate (MHDP) for periods of 1 h to 10 days. The changes in the enamel surface appearance were observed by scanning electron microscope (SEM) at up to × 40,000, and lesion progress was assessed by chemical analysis and polarized light microscopy. In both model systems subsurface caries-like demineralization was produced. The SEM observations showed that the opening up of the intercrystalline spaces by acid over the entire exposed enamel surface appears to be the initiating stage during the first few minutes or hours of caries attack in both systems. These intercrystalline pathways provide the route for subsequent mineral loss during carious lesion progression prior to establishment of the classical subsurface lesion

ISSN:0008-6568    

DOI:10.1159/000260825

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

A model for subsurface lesion formation in dental enamel is presented that takes into account the known calcium phosphate chemistry and the transport processes occurring within the enamel and across the enamel surface-solution interface. The model, illustrated through the use of solubility diagrams (‘potential plots’), explains the presence of a relatively intact enamel layer overlying a zone of demineralization as a result of reprecipitation processes occurring within the enamel surface layer as dissolved ions, from beneath the surface, diffuse into the enamel surface and across the enamel surface-solution interface. Two conditions must be fulfilled, however, in order to form the intact layer. First that the rate at which ions diffuse across the enamel surface-solution interface does not exceed the rate of the envisioned reprecipitation processes. This rate is effectively controlled by the level of saturation of the demineralization media with respect to enamel mineral. The second requirement is that appropriate conditions are present within the enamel surface which support the reprecipitation processes. A working hypothesis is presented which states that demineralization solutions which support the formation of dicalcium phosphate dihydrate within the enamel surface will foster the formation of subsurface lesions under the appropriate kinetic conditions. The proposed model is noted to be consistent with experimental observati

ISSN:0008-6568    

DOI:10.1159/000260826

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Marked differences were observed when human enamel surfaces were exposed to partially saturated lactate buffers containing varying amounts of calcium and phosphorus at different pH values and at a constant pH 4.3. The degree of saturation of these buffers was defined as the ratio of the activity product for hydroxyapatite in solution to a working estimate of the solubility product constant for enamel (KE= 5.5 × 10––55). It was observed that when using buffers in a well-defined saturation range (2–7 × 10––8), subsurface lesions were produced within a 72-hour time period. Within the same time frame, however, cavitations were produced using buffers of a relatively low degree of saturation (10––9–10––13) and essentially no mineral loss could be detected by microradiography or polarized light microscopy using relatively highly saturated buffers (3.5 × 10––7 –– 4 × 10––6). The results obtained are shown to be consistent with a proposed caries model which explains the observed histological features of the incipient lesion. Based on these findings it was concluded that the driving force for enamel demineralization is best described by the degree of saturation of the demineralization medium with respect to enamel and not by simpler parameters such as pH. It is noted, therefore, that extreme caution must be taken when interpreting observed changes in pH in both in vivo and i

ISSN:0008-6568    

DOI:10.1159/000260827

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Most of the fluoride acquired during topical applications will be released in the oral environment. This investigation deals with the effectiveness and retention of fluoride after different treatments of the enamel. The effect of acidified phosphated fluoride (APF) on sound, and etched, and neutral KF on etched enamel were investigated by studying the F profiles in the enamel after 0, 1, 2, 4 and 8 weeks exposure to running tap water. APF application on etched enamel showed the deepest fluoride penetration and retention. At 8 weeks the differently treated enamel samples were exposed to an artificial caries-inducing solution. The etched and subsequently APF-treated enamel showed least release of minerals.

ISSN:0008-6568    

DOI:10.1159/000260828

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The purpose of this work was to explain how the caries-preventive agent xylitol interferes with the growth of Streptococcus mutans. It was found that the xylitol-sensitive strain of S. mutans 27352 (serotype g) and LG1 (serotype c) took up 14C-xylitol when the labelled pentitol was added to cells growing at the expense of glucose. Uptake of xylitol by growing cells of S. mutans 27352 XR and LG1 XR, two xylitol-insensitive spontaneous mutants, and of S. mutans GS5-2, which was also insensitive to xylitol, was practically inexistent under the same conditions. Alkaline phosphatase treatment followed by enzymatic analysis and thin-layer chromatography revealed that the accumulated product was xylitol phosphate. Intracellular concentrations of 5–7 mM for resting cells and of up to 60 mM for growing cells were calculated. Xylitol was phosphorylated at the expense of phosphoenolpyruvate by toluenized cells of S. mutans LG1, but not by toluenized cells of GS5–2 and S. mutans LG1 XR. The phosphorylation of xylitol was dependent on phosphoenolpyruvate and required the presence of both soluble and membrane cellular fractions in the reaction mixture. This indicated that xylitol was transported and phosphorylated by a phosphoenolpyruvate: sugar phosphotransferase system. The phosphoenolpyruvate-dependent phosphorylation by isolated membranes of S. mutans LG1 in the presence of the soluble fraction was inhibited by fructose but not by glucose, mannose or galactose. Measurement of phosphoenolpyruvate: phosphotransferase activities in isolated membrane revealed that strain 27352 and LG1 had activities for fructose and xylitol; membrane from 27352 XR and LG1 XR had very little activity for fructose and xylitol. It was concluded that xylitol was transported and phosphorylated by a constitutive phosphoenolpyruvate:fructose phosphotransferase system in S. mutans. The data suggested that xylitol toxicity in S. mutans is caused by the intracellular accumulation of xylitol phosph

ISSN:0008-6568    

DOI:10.1159/000260829

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The effect of 0.07 or 0.15 mM chlorhexidine (CHX) and 4.0 or 8.0 mM potassium fluoride (F), added singly and in combinations, on acid production by Streptococcus mutans and Streptococcus sanguis was studied. Cells were grown in a chemostat under different environmental conditions and acid production from glucose or sucrose was measured as a rate at pH 7.0 and by pH-fall experiments. CHX had a greater inhibitory action on S. mutans while S. sanguis was more sensitive to F. Growth conditions affected the sensitivity of both strains to the two inhibitors and, in general, cells grown glucose-limited were the most sensitive. Combinations of F and CHX showed additive inhibitory effects on acid production, irrespective of the method of measurement.

ISSN:0008-6568    

DOI:10.1159/000260830

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260831

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

In 1975 and in 1982 more than 1,500 Budapest high school pupils aged 14–17 years were examined. The percentage of caries-free pupils increased from 1.5% in 1975 to 4.8% in 1982 (in girls from 1.4 to 5.1 % and in boys from 1.8 to 4.2%). The overall reduction in caries prevalence was 15.1% (18.8%) in girls and 12.8% in boys). Oral hygiene and periodontal indices showed no improvement. Higher sales of fluoridated toothpaste and lower sugar consumption are possible contributing factor

ISSN:0008-6568    

DOI:10.1159/000260832

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The purpose of this paper was to develop and test an empirically based system to estimate the effectiveness of caries-preventive agents. Using accepted statistical methods, effectiveness predictions for fluoride supplementation, APF gels and solutions, and fluoride varnishes were calculated and used to illustrate the statistical formulation. The resulting predictions were then compared to commonly cited estimates of reduction for the respective procedures. The proposed system could be useful to public health administrators in determining the cost-effectiveness estimates for various preventive programs.

ISSN:0008-6568    

DOI:10.1159/000260833

出版商:S. Karger AG    

年代:1985

数据来源: Karger