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C van Loveren

Publications and source records attributed to C van Loveren.

52 records · Page 3Linked to original sources
PubMed1992

[Caries and fluoride].

The cariostatic effect of fluoride is well documented, but the exact mechanisms of action are still subject of many studies. Re-evaluations of the clinical data of water fluoridation studies have confirmed that fluoride can have a pre-eruptive effect. But in general, the post-eruptive effects of low concentrations of fluoride on the de- and remineralisation processes are regarded to be of greater importance. Infrequent applications of concentrated fluoride solutions may only be effective in demineralised enamel. The Dutch national recommendations for the use of fluorides correspond well with the present views on the mechanisms of action of fluoride.

Cariostatic Agents↗
PubMed1991

Differences in cariogenicity between fresh isolates of Streptococcus sobrinus and Streptococcus mutans.

Streptococcus sobrinus is known to possess cariogenic properties in vitro. It can produce acid in large amounts and it has the capacity to adhere to enamel and other surfaces. However, most studies on cariogenicity have been performed with laboratory strains that have been subcultured over long periods of time. Therefore, the cariogenicity and acidogenicity of 9 fresh isolates of both S. sobrinus and Streptococcus mutans from human dental plaque were compared. The bacteria were inoculated into the oral cavity of rats. The rats were fed diet SSP 20/5, containing 20% sucrose and 5% glucose. After the experimental period of 42 days, the amount of caries was assessed and bacterial counts were determined using monoclonal antibodies. Four out of 9 S. sobrinus strains and 3 out of 9 S. mutans strains did not colonize the rats. Colonizing strains constituted 39-78% of the total anaerobic cultivable microflora. The numbers of advanced dentinal lesions in the fissures of the rats colonized with S. mutans were significantly lower than those colonized with S. sobrinus (p less than 0.05). S. sobrinus produced acid more rapidly than S. mutans in a pH-stat system at pH values between 6.5 and 5.0 (p less than 0.01). The results indicate that fresh isolates of S. sobrinus are more cariogenic in rats than fresh isolates of S. mutans. This is possibly due to differences in glycolytic properties of these two species.

Animals↗
PubMed1991

Competition between fluoride-resistant and fluoride-sensitive Streptococcus mutans in rat dental plaque.

The experiments were designed to study the effects of fluoride on the competition between a fluoride-sensitive strain of Streptococcus mutans (C180-2) and a fluoride-resistant mutant (S. mutans C180-2FR) in rat dental plaque. Competition was induced either by superinfecting rats or by co-caging rats infected with either strain with non-infected rats. Sodium fluoride was applied in diet and drinking water (60 ppm F), as daily brushings with a 1% F solution, or as a combination of both administrations. The fluoride applications favoured S. mutans C180-2FR, but not enough to outcompete the parent strain successfully under all conditions. Fluoride protected rat dental plaque harbouring S. mutans C180-2FR against colonization by the parent strain. In rats not previously infected with S. mutans, the fluoride in diet and drinking water in combination with the fluoride brushings favoured S. mutans C180-2FR in colonizing rat dental plaque. However, the fluoride applications did not benefit S. mutans C180-2FR in colonizing plaque in which the parent strain was already present. Human dental plaque may be colonized by fluoride-resistant S. mutans strains after spontaneous mutation in response to a fluoride pressure. Our data suggest that this pressure may also provide an ecological advantage to this mutant to colonize the dental plaque.

Animals↗
PubMed1990

Development and establishment of fluoride-resistant strains of Streptococcus mutans in rats.

Fluoride-resistant strains of mutans streptococci have been found to be less cariogenic than their parent strains in the rat model system. Therefore, it is important to determine whether the use of fluorides in vivo will increase the fluoride resistance of mutans streptococci and thereby possibly decrease their cariogenic potential. We studied (1) the fluoride resistance of Streptococcus mutans C180-2 in rat dental plaque exposed to various fluoride treatments (experiment 1), (2) the cariogenic potential of the exposed plaque after transmission to other animals (experiment 2), and (3) whether the fluoride treatments favoured the establishment of in vitro induced fluoride-resistant S. mutans in competition with a fluoride-sensitive strain in rat dental plaque (experiment 3). In all experiments, specific pathogen-free Osborne-Mendel rats were used, and all animals received diet SSP 20/5, containing 20% (w/w) sucrose and 5% (w/w) glucose, and tap water ad libitum. In experiment 1, the rats were inoculated with S. mutans C180-2. For an experimental period of 44 days, the rats either received no F treatment or received NaF mixed in the diet and drinking water (20 or 60 ppm F) or were brushed 6 days per week with an aqueous NaF solution containing either 0.1% (w/v) or 1% (w/v) F, respectively. Bacteriological analyses at the end of the experiment revealed that none of the fluoride treatments had caused a detectable increase in the inherent fluoride resistance of S. mutans C180-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1989

In vitro induced fluoride resistance of Streptococcus mutans and dental caries in rats.

The aim of this investigation was to study the effect of an in vitro acquired, stable, fluoride-resistant strain of Streptococcus mutans on dental caries in rats. Three groups (P0, P5 and P10) of SPF Osborne-Mendel rats were inoculated with the fluoride-sensitive S. mutans C180-2. Three other groups (FR0, FR5 and FR10) were inoculated with cultures of the fluoride-resistant S. mutans C180-2FR. Diet SSP 20/5 and tap water (less than 0.2 ppm fluoride) were available ad libitum to all groups. The drinking water of groups P5 and FR5 was supplemented with 5 mg F-/1 and the drinking water of groups P10 and FR10 with 10 mg F-/1. At the end of the caries experiment (days 58/59) there were no significant differences in the percentages and in the numbers of S. mutans in the total maxillary plaques of groups P0 to P10 and of groups FR0 to FR10, respectively. The fluoride tolerance of S. mutans cells re-isolated from rats, inoculated with the fluoride-sensitive strain, showed an unstable decrease compared to before inoculation. S. mutans cells re-isolated from rats, inoculated with the fluoride-resistant strain, showed both unstable and stable adaptation towards fluoride sensitivity. The animals superinfected with the fluoride-resistant strain developed less dentinal/fissure caries. Fluoride given in the drinking water at concentrations of 5 and 10 mg/l was effective in reducing caries irrespective of whether the animals were superinfected with the fluoride-sensitive or the fluoride-resistant strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Similarity of bacteriocin activity profiles of mutans streptococci within the family when the children acquire the strains after the age of 5.

It has been shown that there is a window of infectivity for mutans streptococci between the ages of 19 and 31 months, when many children acquire mutans streptococci transmitted from their mothers. Part of the children that escape this window acquire mutans streptococci at a later age. In this group, maternal transmission is expected to be less prevalent. The present study compared the bacteriocin activity profiles of mutans streptococci isolated from mothers, fathers and children when the children acquired the mutans streptococci between the ages of 5 and 11. Twelve families were randomly selected from a group of 11-year-old children who were known to have acquired mutans streptococci during this age period. From the saliva of the mothers (n = 12), fathers (n = 8) and children (n = 12) approximately 30 mutans streptococci strains were isolated. All isolates were tested twice for bacteriocin activity against 21 indicator strains with a double-layer technique. Bacteriocin activity of strains was considered to be different when the number of strains against which bacteriocin was produced differed >1 or when the width of one or more inhibition zones differed > or =4 mm. In 7/12 mother-child pairs similar profiles were found. In the 8 father-child pairs similar profiles were only found on 2 occasions. In these 2 families, all 3 ( mother, father and child) harboured strains with a similar profile. In 4/8 father-mother pairs similar profiles were found. There was no correlation between the prevalence of mutans streptococci strains, the number of indicator strains against which the strains made bacteriocin, nor the mean size of the inhibition zones and the presence of similarity of bacteriocin activity profiles of mutans streptococci within the family members. The results show that even when a child acquires mutans streptococci after the age of 5, there may be similarity between mutans streptococci in mother, father and child, indicating that transmission between the family members occurs.

Age Factors↗
PubMedDate not supplied

Prognosis of caries increment with past caries experience variables.

This study aimed to select past caries experience variables as caries predictors and to compare their prognostic accuracy with the variables used in a method of caries prognosis developed in a Swiss child population. The data used for the analyses originated from an 8-year longitudinal study starting in 1980 on caries of 7.5-year-old Dutch children. Stepwise logistic regression analyses provided predictor variables. The newly introduced variables D23fi, D(123)i and D23pifi were interchangeable and the most powerful caries predictors. For the sake of uniformity and ease of application, D23fi (number of fissures of the permanent first molar with non-cavitated or cavitated caries lesions) was chosen as the first variable in the logistic regression equations. The gain in accuracy of the second and third predictor variables (number of sound primary molars and the number of buccal and lingual smooth surfaces of the permanent first molar with non-cavitated or cavitated caries) in the regression equations was limited. The D1 condition of surfaces could be omitted from the prediction models. The present forced three-predictor-regression equations for 7.5-, 9.5- and 11.5-year-old children were evaluated to assess their prognostic performance by using the area under the ROC curve as a measure of prognostic quality. For the present regression equations, the area under the ROC curve was 81-87%, which was higher compared to the Swiss regression equations for caries prognosis.

Adolescent↗
PubMedDate not supplied

The effect of a single application of 40% chlorhexidine varnish on the numbers of salivary mutans streptococci and acidogenicity of dental plaque.

The relationship between the numbers of salivary mutans streptococci and the acid production in dental plaque after a single application of the 40% chlorhexidine varnish EC40 has been studied. Thirteen healthy subjects were treated with EC40 varnish. Saliva samples were taken before and up to 12 weeks after treatment to count mutans streptococci and lactobacilli. At the same time points plaque samples were taken before and after sucrose challenge and analyzed for protein and organic acid. Suppression of salivary mutans streptococci was observed together with a reduced production of lactic acid in sucrose-challenged dental plaque in 9 subjects while inhibition of acid production without significant suppression of mutans streptococci was observed in the other 4 participants. The duration of the effects differed among the individuals but never exceeded 6 weeks. We conclude that a prolonged suppression of mutans streptococci and acid production was not achieved by a single treatment with EC40 varnish in all subjects. Moreover, reduced acidogenicity of dental plaque after chlorhexidine treatment was not necessarily predicted by suppression of mutans streptococci in saliva.

Adult↗
PubMedDate not supplied

Efficacy of fluoride toothpaste in preventing demineralization of smooth dentin surfaces and narrow grooves in situ under frequent exposures to sucrose or bananas.

The use of models simulating fissures allows studying demineralization at sites that are most prone to caries in vivo. In practice, most in situ models use flat surfaces. Our objectives were: (1) to compare the demineralizing potential of sucrose solution with that of bananas and (2) to study the effect of fluoride toothpaste on demineralization in situ in an easily accessible site and a plaque stagnation site. Four volunteers wore bovine dentin specimens with narrow grooves and a smooth surface for two 1-week in situ periods, with eight 1-min sugar exposures daily: either by a rinse with 10% sucrose, or by consumption of a piece of banana. Twice daily, the appliance was dipped in toothpaste slurry of a control (fluoride-free) toothpaste at one side and a fluoride toothpaste at the contralateral side. Demineralization was assessed by transversal microradiography. We found no difference in dentin demineralization after frequent exposure to either sucrose solution or bananas. Fluoride toothpaste effectively protected dentin only at the smooth surface. In the grooves, fluoride affected the demineralization pattern; it drove lesions towards the bottom of the groove. We conclude that assessing only smooth surfaces in intraoral tests might lead to underestimated food cariogenicity and to overestimated efficacy of fluoride-containing toothpaste.

Adult↗
PubMedDate not supplied

Caries-preventive agents induce remineralization of dentin in a biofilm model.

The aim was to study remineralization in dentin underneath a biofilm. This was done in a constant depth film fermentor (CDFF) which was modified so that two treatments can be applied simultaneously in one experiment. Forty-five Streptococcus mutans biofilms were grown in grooves in dentin. Growth medium (3.7 g/l BHI, 1.5 mM calcium and 25 mM PIPES) was administered alternately with 2% sucrose pulsing 4 x 30 min/day. Fluoride at 135 ppm as NaF only or in a mixture with 0.2% chlorhexidine was applied for 2 x 5 min/day. The treatments started 5 days after inoculation and lasted 15 days. Five specimens per group were removed at various time points. The biofilms were checked for viability (by plating) and acid content (by capillary electrophoresis). The dentin specimens were analysed for mineral loss and lesion depth (by transversal microradiography). Fluoride treatment had no effect on the viability but reduced lactic acid production by 75%. The mixture treatment reduced the viability by 80% and the lactic acid content by 93% on the first day and later reduced the two parameters to below the detection limits. Significant differences in changes in mineral loss and lesion depth were observed between the treatment groups. Partial remineralization but deeper lesions were observed in the fluoride group, while nearly complete remineralization was seen in the mixture group. In conclusion, the CDFF S. mutans biofilm model can be used as a de- and remineralization biofilm model, and the split mode is particularly suitable for testing caries-preventive agents.

Animals↗
PubMedDate not supplied

Total and free fluoride in toothpastes from some non-established market economy countries.

In 101 fluoride toothpastes, bought in local shops in Burkina Faso (n = 3), China (n = 5), Myanmar (n = 22), Nepal (n = 19), Philippines (n = 13), Syria (n = 22), Togo (n = 7) and Vietnam (n = 10), the total and free ionisable fluoride concentrations were established. The total fluoride concentration of the toothpastes was determined by gas liquid chromatography. The amount of soluble fluoride was measured after dilution in artificial saliva and treatment of the supernatants with acidic phosphatase. The free fluoride concentration in this mixture was measured with a fluoride electrode. Twenty-five percent of all toothpastes contained less than 738 ppm total fluoride, and another 25% contained between 738 and 977 ppm fluoride. Regarding free ionisable fluoride the 25th, 50th, and 75th percentile contained < or =275, 780 and 990 ppm fluoride, respectively. Of the 61 toothpastes with declared fluoride concentration, 75% contained a total F concentration of > or =89% of the declared concentration. In 25% of these toothpastes the free ionisable fluoride was < or =55% of the declared fluoride, and in another 25% of the pastes the free ionisable fluoride concentration was > or =89% of the declared fluoride. In conclusion, deficiencies were found regarding the total as well as the free ionisable fluoride concentration of toothpastes bought in non-established market economy countries. Unclear labelling concerning the type and concentration of fluoride was often encountered. A need for quality control of fluoride toothpastes is recommended.

Africa↗