摘要:

Four thin layers of enamel totaling approximately 8 μm were removed from each of two bicuspids in 215 subjects, age 14–24 years, and analyzed for fluoride. The concentration of fluoride in the outer layers decreased significantly with subjects’ age. A small but statistically significant correlation between enamel fluoride and DMFS of individual subjects was found. Correlations were somewhat stronger in the outer enamel layers and in subjects from nonfluoridated a

ISSN:0008-6568    

DOI:10.1159/000260871

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Third molars just erupting and premolars (before eruption or half a year or 3.5 years after eruption) were extracted and sawn vertically through the buccolingual plane. Tracings of the Ca, P, Na and Mg contents of the outer 100-μm layer of the enamel were made with an electron microprobe. Care was taken to limit the diameter of the excited volume to about 1 μm and to suppress the evaporation of Na. On the unerupted and freshly erupted surfaces the Na and Mg content varied from 50 to 80% of the content at 100 μm depth. However, half a year or 3.5 years after eruption the Na and Mg contents were negligibly small at the tooth surface and they remained smaller than in unerupted or freshly erupted teeth up to a depth of 10–30 μm. These data suggest that posteruptive maturation occurs in the mineral of the outer layer of tooth enamel whereby it builds up a higher resistance to carious breakdown. This interpretation is corroborated by clinical findings reported in the literature. The consequences of wear and abrasion on these phenomena are not known yet. The above-mentioned depth of 10–30 μm agrees with the penetration depth of pH changes estimated to result from the consumption of foods and drinks with va

ISSN:0008-6568    

DOI:10.1159/000260872

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

This paper describes the influence of very small amounts of F (0.12 ppm) in a demineralizing solution on lesion formation in bovine enamel at pH = 5. Polished bovine enamel has a very low F content and does not ‘contaminate’ the demineralizing solution with fluoride from the enamel itself. Standardized enamel areas were demineralized for various periods up to 240 h; after a given period the liquid was analyzed for Ca, phosphate and F; the enamel defects formed were investigated by means of microradiography and microscopy. The results show that (1) lesion depth is hardly influenced by the presence of about 0.12 ppm F in the liquid; (2) the amount of mineral dissolved from the enamel is strongly influenced by F; (3) demineralization without fluoride in solution resulted in enamel defects without a surface layer (softened), and (4) demineralization with 0.12 ppm F in solution resulted in subsurface lesi

ISSN:0008-6568    

DOI:10.1159/000260873

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Caries-like subsurface lesions were produced in synthetic calcium hydroxyapatite aggregates by a modified application of the acid-gel method. The progress of lesion development was monitored using the technique of quantitative scanning microradiography. Although demineralization occurred in the subsurface region, the mineral content of the surface layer varied only by a small fraction during lesion development.

ISSN:0008-6568    

DOI:10.1159/000260874

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The purpose of this in vivo study was to compare the fluoride acquisition on (Fon) as well as in (Fin) enamel after a single application of polyurethane varnishes. The varnishes investigated were all on the same polyurethane basis but contained either 0, 0.05, 0.1 or 0.7 wt% fluoride. The varnishes were removed after an application period of 24 h. A new technique for in vivo experimentations was developed using frame prostheses with slots to hold the experimental human enamel specimens. 11 participants carried 52 enamel specimens in frames for 1 week. Fon and Fin measurements were done after the experiment. The acquired amount of fluoride as Fon varnish 0.1% ≃ varnish 0.05% ≃ varnish 0% ≃ control. The acquired fluoride as Fin showed the same ranking. From a clinical point of view this study shows that it is not interesting to consider varnishes with a content of 0.1 wt% F–– or lower for caries prevention, because 6 days after removal both Fon and Fin are hardly different from unfluoridated c

ISSN:0008-6568    

DOI:10.1159/000260875

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Human salivary lysozyme (HSL) was purified from human saliva and added to cultures of Streptococcus mutans. 14C-2-deoxyglucose incorporation, L-(+)-lactic acid production from glucose and the number of viable cells were then determined. Both sugar incorporation and lactic acid production were inversely related to the lysozyme concentration and the time of lysozyme treatment. At a lysozyme activity corresponding to 20.0 μg/ml hen egg white lysozyme, the amount of sugar taken up after 30 min was reduced by approximately 50%. No L-(+)-lactic acid was detected after 3 h of incubation. Strains of S. mutans of serotypes b and c were susceptible to the action of HSL, whereas serotypes a, d and e were resistant. A significant reduction in viable cell count was found for strains BHT (b) and Ingbritt (c) after 2 h of incubation with HSL. The results suggest that the reduction in sugar uptake and acid production was due to initial damage of the bacterial cell membrane and a reduced number of viable cells

ISSN:0008-6568    

DOI:10.1159/000260876

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Approximal plaque was collected from 14- to 15-year-old females taking part in a 3-year trial of a plaque control programme in which subjects in the experimental group visited a hygienist fortnightly. Samples were collected (a) during and (b) 1 year after completing the trial. Samples were stored in liquid nitrogen prior to cultural analysis. In study 1, samples (a) and (b) from 20 subjects in the experimental group were compared. In study 2, plaque collected during the trial was compared in 23 matched pairs of subjects from the experimental and control groups. Few of the differences observed in microbiological composition were statistically significant in either study. However, in study 1 the proportion of streptococci in plaque was higher during the trial than 1 year after completion (p < 0.05). No comparable difference was observed between groups in study 2, but the proportion of gram-negative anaerobic cocci was higher in the experimental group (p = 0.05) and the proportion of non-facultative anaerobes higher in the control group (p < 0.01). In addition, counts on TYC medium indicated a shift of streptococcal species in the experimental group where Streptococcus sanguis was increased (p < 0.05) at the expense of Streptococcus mitior (p < 0.01). The results indicate some microbiological shifts related to plaque control, but against a background of overall stability in the basic flora of interdental plaque.

ISSN:0008-6568    

DOI:10.1159/000260877

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The question whether low doses of fluoride have in vivo effects on the adenylate cyclase-cyclic AMP system or not is still not fully elucidated. In this experiment, 10 young adults received 0.05 and 0.07 mg fluoride/kg body weight per os. Their parotid salivas were analyzed for secretory rate and concentrations of fluoride, cyclic AMP and amylase at rest and after stimulation with citric acid. The results showed that fluoride caused a statistically significant increase in secretory rate and cyclic AMP concentration. A slight, statistically not significant, increase in amylase concentration was recorded. The interpretation of the results is that caries-preventing doses of fluoride have in vivo effects on the adenylate cyclase-cyclic AMP system in the parotid gland. However, the increase in saliva cyclic AMP concentration is marginal to that reported after physiological stimulation.

ISSN:0008-6568    

DOI:10.1159/000260878

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Maltose glycolysis and transport in Streptococcus mutans OMZ 176 were shown to be inhibited by maltotriitol (MTL). The sugar alcohol was taken up, but was not metabolized. The phosphoenolpyruvate: maltose phosphotransferase (PEP:PTS) system activity was present in cells grown on glucose and maltose and was not inhibited by MTL. The product of the maltose PTS reaction was isolated and identified as maltose 6′-phosphate. The phospho-α-glucosidase induced by maltose hydrolyzed maltose phosphate into glucose and glucose 6-phosphate. The maltose-inducible amylomaltase which catalyses the transfer of both glucosyl and maltodextrinyl units was purified. The apparent Km for maltose was 21.8 mM. MTL inhibited the enzyme activity on maltose (Ki 2.0 mM) and maltotriose without being itself a substrate, but transglycosylation occurred on MTL when maltoheptaose was the donor substrate. These results indicated that in strain OMZ 176, maltose transport was mediated by a PEP-dependent maltose PTS yielding maltose 6′-phosphate which subsequently was hydrolyzed by a maltose-inducible phospho-α-glucosidase. It was suggested that MTL inhibits glycolysis of maltose by reducing the rate of maltose transport and inhibiting amylomaltase and phospho-α-glucosidase activities, resulting in an accumulation of maltose 6′-p

ISSN:0008-6568    

DOI:10.1159/000260879

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:0008-6568    

DOI:10.1159/000260880

出版商:S. Karger AG    

年代:1985

数据来源: Karger