ISSN:0008-6568    

DOI:10.1159/000262031

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

A new method for the in vivo assessment of changes in initial enamel caries lesions was developed and tested. A CCD camera equipped with a high-pass filter (λ > 520 nm) collects the fluorescence image of carious teeth, illuminated intraorally with diffuse laser light (λ=488 nm). Incipient lesions show a loss in fluorescence to be expressed as a percentage of fluorescence radiance of sound tissue. A PC program (Inspektor, model QLF 1.0) is used for display, storage, and subsequent analysis of images. To enable the calculation of fluorescence loss, the fluorescence of sound tissue at the lesion site is reconstructed from the radiances of sound tissue bordering the lesion. This method was tested on 19 visually sound buccal surfaces in vivo. The differences between actual and reconstructed radiance was -1.6 ± (SD) 1.1%, over areas varying between 8 and 14 mm2. The repeatability of the caries quantification was tested by measuring one arrested initial caries lesion 25 times in vivo. The lesion area was 0.56 ± 0.20 mm2, and the loss of fluorescence was 17.6 ± 0.7%, corresponding to a lesion depth of 17 ± 2 μm. The new quantitative method was applied for the testing of an in vivo caries model using plaque-accumulating brackets on premolars scheduled for extraction. Videoimages were recorded in vivo before bracketing and 0, 2, 3, and 5 weeks after debracketing. Clear changes between the different time points were recorded for both lesion size and mineral content. Thus, the method seems suitable for in vivo measurement of mineral changes in natural enamel lesions on smooth surfaces and might be useful for clinical trials and evaluation of preventive me

ISSN:0008-6568    

DOI:10.1159/000262032

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Techniques based on transillumination of teeth with visible light will be a valuable aid in caries diagnosis, if a higher sensitivity than that of the present Foti method is achieved. Therefore, a better understanding of light propagation through teeth is required, and hence it is useful to investigate the propagation of light through sound dental material. In this study the intensities emanating from the surfaces of enamel and dentine bars were measured when these bars were illuminated using a fibre rod transporting the light from a HeNe laser (λ = 633 nm) as a light source. From the measured intensities, the radiant fluxes emanating from the surfaces were calculated. To account for a directional dependence of these fluxes, optical anisotropy in dental material was investigated by comparing the transmitted light intensity in a direction perpendicular and parallel to the approximal surface of the tooth from which the sample was cut. The mean ratio of the transmitted intensities in perpendicular and parallel direction was 0.86 ± 0.06 for enamel and 2.88 ± 0.43 for dentine. In addition, for enamel the asymmetry parameter, g, was estimated. The averaged value was g= 0.68 ± 0.09. It was concluded that for dentine the optical anisotropy as measured supports the idea that tubules are the predominant cause of scattering in dentine. For enamel the results indicate that the hydroxyapatite crystals contribute significantly to scattering and that the influence of the prism structure on the light propagation is sm

ISSN:0008-6568    

DOI:10.1159/000262033

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Recently, several papers investigated the linear dimensional changes in dentine after air-drying. This paper pertains to weight changes, volume changes, and density changes caused by air-drying of sound and demineralized intact dentine. The densities of sound and artificially demineralized human coronal dentine were measured in the wet state and after various drying periods of up to 24 h. The volume was assessed either by means of a pyknometer (wet samples) or by means of dimension measurements. The air-drying experiments were done using a Mettler thermobalance at room temperature. The density of wet sound coronal dentine was found to be 2.24 ± 0.12 g cm3; the value of wet demineralized dentine was about 1.6 g cm-3. The data show that previously published density values of powdered sound dentine may have been influenced by powdering effects, air-drying, and air inclusion. In whole demineralized air-dried dentine, air inclusion can be very severe: up to 30% by volume. The results show furthermore that in demineralized dentine we have two drying stages: during the first one (up to about 10 min of air-drying), the lesions shrink about 23%, while a main part of the water in the lesion evaporates, and air is incorporated into the tissue; during the second stage (drying longer than 10 min), the lesions hardly shrink anymore, but water is evaporated mainly from underlying sound dentine, followed by air incorporation

ISSN:0008-6568    

DOI:10.1159/000262034

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Previous studies have shown that chronic acidosis induced by NH4Cl is associated with disturbances in enamel mineralization that resemble severe fluorosis and increased fluoride concentrations in both soft and hard tissues. It has not been shown whether these effects are due to acidosis per se or exposure to high levels of NH4. This 42-day study with rats fed a low-fluoride diet was done to identify the etiological factor. Two control groups received deionized water or water containing NaCl. Two groups received NH4-containing compounds that did not produce acidosis (NH4HCO3 or HN4 acetate). Two other groups were rendered acidotic by exposure to NH4Cl in the drinking water (metabolic acidosis) or to an atmosphere containing 10% CO2 (respiratory acidosis). The femur epiphysial fluoride concentrations were elevated in the NH4Cl and NH4 acetate groups, and the magnesium concentrations were elevated in the groups exposed to NH4 compounds and in the 10% CO2 group. Microradiographic analysis revealed severe disturbances in the mineralization pattern of incisor enamel in both acidotic groups, but normal enamel in the other groups. Enamel fluoride and magnesium concentrations were highest in the acidotic groups. The enamel fluoride concentrations were low (8-14 ppm) and not regarded as the cause of the defective mineralization. It was concluded that the effects on structure and composition of enamel were due to acidosis and not to exposure to high levels of NH4.

ISSN:0008-6568    

DOI:10.1159/000262035

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The purpose of this study was to compare urinary fluoride excretion with fluoride ingestion in children who had either a low fluoride intake or received supplemental fluoride through salt or water. The urinary samples were collected in two ways. In procedure A, urine was collected in the morning, at noon and during the afternoon. This covered a continuous period of approximately 7 h from the beginning to the end of the school day. In procedure B, morning, afternoon and night samples were collected. The morning and afternoon samples were obtained under supervision at school. Procedure B was more useful than procedure A for monitoring salt fluoridation projects. Children with a history of low fluoride intake excreted a mean of 10 μg F/h during the night and the morning, but 13–16 μg F/h after the main meal. Children in a water-fluoridated town or in comprehensive salt fluoridation programs excreted between 19 and 33 μg F/h. However, after the intake of meals prepared with fluoridated salt (250 ppm F) the mean excretion of fluoride ranged between 31 and 49 μg F/h. The levels of excretion corresponded with the levels of fluoride intake and meal patterns in the various g

ISSN:0008-6568    

DOI:10.1159/000262036

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The purpose of this study was to compare the urinary fluoride levels in subtropical Jamaica just before the beginning of salt fluoridation (250 mg/kg salt) in 1987 and again 20 months later. Four age groups were studied in three locations with low to intermediate fluoride concentrations in the drinking water. The averages of supervised, timed morning fluoride excretions ranged between 12.1 and 27.9 μg/h prior to fluoridation as compared with 23.7–67.4 μg/h 20 months after the beginning of the sale of fluoridated salt. The fluoride excretions obtained from 24-hour collections ranged from 169 to 485 μg/24 h in 1987 and increased to 304–657 μg/24 h in 1989. In 1987, the morning fluoride excretions approximated those of French and Swiss children who had a low fluoride intake, but the fluoride levels of 1989 were similar to the data obtained from children who had an intake of 1.2–1.7 mg F/day or consumed fluorida

ISSN:0008-6568    

DOI:10.1159/000262037

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Two hundred and seventeen approximal spaces, initially caries free, in 58 patients were studied clinically and radiographically, at intervals of 6 months, for 3 years. Samples of approximal dental plaque were removed for culture of Streptococcus mutans, Streptococcus sobrinus, and lactobacilli. During the study approximal caries developed in 16 subjects (27.6%) at 30 sites (13.8%), involving 42 teeth. 56 of 58 (96.7%) subjects harboured S. mutans at some time during the study, 62.1% lactobacilli, and 29.3% had S. sobrinus. The counts of S. mutans were significantly higher in those subjects that also carried S. sobrinus than in the remaining subjects. A persisting high count of S. mutans 105 colony-forming units per millilitre (CFU/ml) or a count that rose by ≥ 1 × log10 CFU/ml during the study was seen in 25 of 30 sites that subsequently became carious (p 103 CFU/ml or rising by ≥l×logo CFU/ml were seen in 17 of 30 sites that became carious (p < 0.001). Although there were strong statistical associations between approximal caries and high or rising counts of these cariogenic bacteria, the bacterial counts were not good predictors of future approximal caries at that particular

ISSN:0008-6568    

DOI:10.1159/000262038

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

It is not known whether the aetiology of occlusal hidden caries lesions (HCL) is identical to that of small visible lesions (SVL). Previous studies of the microflora of HCL suggest that relatively few species can be isolated. The aim of the present study was to compare the bacterial composition of dentine from 10 HCL and 17 SVL in a population of children aged 8-18 years. The following bacteria were identified: Actinomyces spp., mutans streptococci, Streptococcus sanguis, Streptococcus oralis, Streptococcus gordonii, Streptococcus mitis, and Lactobacillus spp. Streptococcus mutans was found more often in the HCL group (p = 0.03), while Streptococcus sobrinus was found more often in the SVL group (p = 0.05). However, proportions of both species were lower in the SVL group as compared with the HCL group (S. mutans p = 0.07; S. sobrinus p = 0.03). Lactobacilli and Actinomyces spp. were found at similar levels in both groups. A more diverse range of streptococcal species and Veillonella was found in the SVL group (p = 0.001). These results show a less complex microflora in HCL as compared with SVL, indicating that the aetiology of hidden caries might be different from that of open caries.

ISSN:0008-6568    

DOI:10.1159/000262039

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Previous studies have found that the fluoride concentration of plaque growing on or adjacent to glass ionomer cement (GIC) is increased and the proportion of mutans streptococci in plaque is reduced. So far, there are only a few studies of the long-term effect of glass ionomer fillings on plaque in vivo. The aim of this study was to determine whether old GIC fillings have effects on plaque fluoride and microflora and whether this effect can be increased by topical application of fluoride on GIC fillings in vivo. The participants were 27 adults with at least 3 GIC fillings about 3 years old. Plaque was collected from sites adjacent to the GIC fillings and from the contralateral teeth, after which a 1.2% fluoride gel was applied to all teeth. Three days later, plaque was collected from the same sites as before. Stimulated saliva was also collected at both appointments. The results show that none of the patients had elevated levels of fluoride in their saliva either before or 3 days after the fluoride treatment. The fluoride concentration was 0.51 μg/mg protein in plaque on GICs and 0.35 μg/mg protein in plaque on contralateral teeth (p = 0.028). After the fluoride treatment, the respective fluoride concentrations were 0.59 μg/mg and 0.75 μg/mg (p = 0.849). No significant differences in the proportion of mutans streptococci and lactobacilli in plaque from GIC and contralateral teeth were found. The results suggest that the fluoride concentration of plaque growing on old GIC fillings is slightly increased. In this study, however, this had no significant effect on the cariogenic microflora. Fluoride application on old GIC fillings did not significantly increase the fluoride concentration of pla

ISSN:0008-6568    

DOI:10.1159/000262040

出版商:S. Karger AG    

年代:1995

数据来源: Karger