Thomas Imfeld

Are Mutans Streptococci Detected in Preschool Children a Reliable Predictive Factor for Dental Caries Risk? A Systematic Review

Research suggests that mutans streptococci play an important role in cariogenesis in children but the usefulness of bacterial testing in risk assessment is unknown. Our objective was to summarize the literature assessing the association of mutans streptococci and dental caries in preschool children, (Pre)Medline (1966–2003), Embase (1980–2003), the Cochrane Register of Controlled Trials (2003, issue 3), and reference lists of included studies were searched. All abstracts found by the electronic searches (n = 981) were independently scrutinized by 2 reviewers. Minimal requirements for inclusion were assessment of preschool children without caries at baseline, reporting of mutans streptococci present in saliva or plaque at baseline and assessment of caries presence after a minimum of 6 months of follow-up. Participants’ details, test methods, methodological characteristics and findings were extracted by one reviewer and cross-checked by another. Homogeneity was tested using χ2 tests. Results of plaque and saliva testing were pooled separately using a fixed effects model. Methodological quality of reports was low. Out of 9 studies included, data from 3 reports on plaque test assessment alone (n = 300) and from 4 reports on saliva test assessment alone (n = 451) were available for pooled analysis. The pooled risk ratio (95% CI) was 3.85 (2.48–5.96) in studies using plaque tests and 2.11 (1.47–3.02) in those using saliva testing. Presence of mutans streptococci, both in plaque or saliva of young caries-free children, appears to be associated with a considerable increase in caries risk. Lack of adjustment for potential confounders in the original studies, however, limits the extent to which interpretations for practice can be made.

Comparison of Three Different Methods for Measurement of Plaque-pH in Humans after Consumption of Soft Bread and Potato Chips

Three different techniques for measurement of plaque-pH—the sampling, the microtouch, and the telemetric methods-were compared after subjects had consumed different starch products. Ten volunteers, equipped with partial lower prostheses, incorporating a miniature glass pH electrode, refrained from toothbrushing for 3 days. Four products were tested: (1) soft bread, (2) potato chips, (3) 5% starch, and (4) 5% sucrose. The pH of plaque was measured for 45 min by means of all three of the methods. The results showed that the mean pH at 10 min was 1.5 units lower with the telemetric than with the sampling method and 1.0 unit lower with the telemetric than with the microtouch method. Relatively small differences were found among the effects of the four test products for all three methods, with the clearest distinctions among the pH curves being with the microtouch and telemetric methods. The main conclusions from the present investigation are: (1) that there were large differences in pH levels measured with the sampling, the microtouch, and the telemetric methods, even though they ranked the test products in about the same order, and (2) that the two starchy foods, bread and potato chips, were both easily fermented by dental plaque.

The impact of the stone age diet on gingival conditions in the absence of oral hygiene.

BACKGROUND The objective of this study was to assess the oral microbiota and clinical data in subjects without access to traditional oral hygiene methods and who ate a diet available in the Stone Age. METHODS Ten subjects living in an environment replicating the Stone Age for 4 weeks were enrolled in this study. Bleeding on probing (BOP), gingival and plaque indices, and probing depth (PD) were assessed at baseline and at 4 weeks. Microbiologic samples were collected at the mesio-buccal subgingival aspects of all teeth and from the dorsum of the tongue and were processed by checkerboard DNA-DNA hybridization methods. RESULTS No subject had periodontitis. Mean BOP decreased from 34.8% to 12.6% (P <0.001). Mean gingival index scores changed from 0.38 to 0.43 (not statistically significant) and mean plaque scores increased from 0.68 to 1.47 (P <0.001). PD at sites of subgingival sampling decreased (mean difference: 0.2 mm; P <0.001). At week 4, the total bacterial count was higher (P <0.001) for 24 of 74 species, including Bacteroides ureolyticus, Eikenella corrodens, Lactobacillus acidophilus, Capnocytophaga ochracea, Escherichia coli, Fusobacterium nucleatum naviforme, Haemophilus influenzae, Helicobacter pylori, Porphyromonas endodontalis, Staphylococcus aureus (two strains), Streptococcus agalactiae, Streptococcus anginosis, and Streptococcus mitis. Bacterial counts from tongue samples were higher at baseline (P <0.001) for 20 species, including Tannerella forsythia (previously T. forsythensis), Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans; serotype a), and Streptococcus spp. CONCLUSIONS The experimental gingivitis protocol is not applicable if the diet (e.g., Stone Age) does not include refined sugars. Although plaque levels increased, BOP and PD decreased. Subgingival bacterial counts increased for several species not linked to periodontitis, whereas tongue bacterial samples decreased during the study period.

Effect of Urea in Sugar-Free Chewing Gums on pH Recovery in Human Dental Plaque Evaluated with Three Different Methods

The aim of this investigation was to study the effect of sugar-free chewing gums containing various amounts of urea on the pH recovery in dental plaque. Three plaque-measuring methods were used, i.e., the telemetric, the microtouch, and the sampling methods. The subjects who had refrained from toothbrushing for 3-7 days rinsed with either 10 or 50% (w/v) sucrose solutions and then chewed for 10 min: (1) one piece of chewing gum in a series of six tests in which the urea content increased from 10 to 80 mg per piece of gum: (2) one or two pieces of gum containing 20 mg urea, and (3) one, two, or three pieces of gum, one after the other, containing 20 mg urea. In some of the test series, a conventional sugarless gum was used as a control. A quick rise in plaque pH was found with all urea-containing chewing gums within the first minutes of chewing, and neutralization continued during the whole 10-min chewing periods. Higher concentrations of urea resulted in more pronounced pH recovery. Slightly higher plaque pH values were found when chewing on two pieces at a time of a 20-mg urea gum was compared with only one piece. Significantly higher pH values were recorded when using three pieces of chewing gum, one after the other (10 + 10 + 10 min), as compared with two pieces (10 + 10 min) or just one piece (10 min). In conclusion, all sugar-free chewing gums tested, particularly the urea-containing ones, initiated a pronounced pH recovery in dental plaque when chewed after a sucrose rinse.(ABSTRACT TRUNCATED AT 250 WORDS)

Fine-tuning of Bioactive Glass for Root Canal Disinfection

An ideal preparation of 45S5 bioactive glass suspensions/slurries for root canal disinfection should combine high pH induction with capacity for continuing release of alkaline species. The hypothesis of this study was that more material per volume of bioactive glass slurry is obtained with a micrometric material (< 5 μm particle size) or a micrometric/ nanometric hybrid, rather than a solely nanometric counterpart. This should correlate with alkaline capacity and antimicrobial effectiveness. Slurries at the plastic limit were prepared with test and reference materials in physiological saline. Total mass and specific surface area of glass material per volume were determined. Continuous titration with hydrochloric acid was performed, and antimicrobial effectiveness was tested in extracted human premolars mono-infected with E. faecalis ATTC 29212 (N = 12 per material). While the nanometric slurry had a 12-fold higher specific surface area than the micrometric counterpart, the latter had a considerably higher alkaline capacity and disinfected significantly better (Fisher’s exact test, P < 0.05). The hybrid slurry behaved similarly to the micrometric preparation.

Impact of toothpaste slurry abrasivity and toothbrush filament stiffness on abrasion of eroded enamel – an in vitro study

Objective. Toothbrush abrasion is significant in the development of tooth wear, particularly when combined with erosion. This in vitro study aimed to evaluate the impact of toothpaste slurry abrasivity and toothbrush filament stiffness on abrasion of eroded enamel. Material and methods. Eroded enamel samples (hydrochloric acid, pH: 2.6, 15 s) were brushed with 40 strokes in an automatic brushing machine using manual toothbrushes with different filament stiffness (filament diameter: 0.15, 0.20, or 0.25 mm). A paste-free control slurry (relative enamel abrasion (REA) value 2) and toothpaste slurries with different abrasivity (REA values 6 or 9) were used for brushing. Erosion and abrasion were followed by storing the enamel samples in artificial saliva for 3 h. After each 4th cycle, the samples were stored in artificial saliva for 15 h. After 60 cycles, enamel loss was measured by profilometry and statistically analyzed by two-way and one-way ANOVA and Bonferroni/Dunn post-hoc tests. Results. Loss of enamel (mean, µm) was influenced mainly by the abrasivity of the slurry and increased along with REA value (REA 2: 0.0–0.2, REA 6: 2.1–3.3, REA 9: 2.9–3.7). Abrasion of eroded enamel was also affected by filament stiffness of the toothbrush, but only groups brushed with toothpaste slurry of REA 6 showed any significant difference between the different toothbrushes. Thereby, toothbrushes with 0.2 mm filament diameter caused higher enamel loss than 0.15 and 0.25 mm filaments. Conclusions. Toothbrush abrasion of eroded enamel is influenced mainly by the abrasivity of the toothpaste slurry, but is also modified by toothbrush filament stiffness.

Some Dental Effects of Xylitol under Laboratory and in vivo Conditions

In vitro, xylitol was not fermented by S. mutans and A. viscosus and had no effect on cell growth. Xylitol neither interfered with the utilization of sucrose by the two bacterial species nor inhibited bacterial colonization of rat molar surfaces in sucrose-containing broth. In a rat caries test, xylitol added to starch diets and starch-sucrose diets did not affect formation of bacterial agglomerates on rat molars. Rinsing with 10% xylitol solutions did not interfere with early plaque formation in young adults consuming their habitual diet. Telemetric recordings of interdental plaque pH showed that 10% xylitol rinses and xylitol chewing gum were non-acidogenic. Xylitol did not prevent rapid sucrose glycolysis. In a 40-day rat caries test, xylitol was non-cariogenic and seemed to reduce the cariogenic potential of sucrose administered simultaneously, however, the animals consuming xylitol diets suffered from severe diarrhoea and gained less weight. In another experiment, rats drank less when xylitol was added to the drinking water.

Radio‐opaque nanosized bioactive glass for potential root canal application: evaluation of radiopacity, bioactivity and alkaline capacity

AIM To produce novel nanosized bioactive glass particles with radio-opaque properties and high alkaline capacity and to evaluate their performance as a potential bioactive root canal dressing or filling material. METHODOLOGY Flame spray-derived bioactive glass particles in the nanometre range were produced including bismuth oxide as a radiopacifier. Calcium hydroxide, barium sulphate and bismuth oxide served as controls. Corresponding materials were compressed to obtain dense specimens with increased alkaline capacity. Radiopacity was evaluated, and in vitro bioactivity was monitored using Raman spectroscopy and scanning electron microscopy. Leaching of bismuth was controlled using atomic absorption spectroscopy. RESULTS Bioactive glass particles with up to 50 wt% bismuth oxide revealed radiopacity with an equivalent of 4.94-mm aluminium. The introduction of bismuth into the bioactive glass altered the alkaline capacity and the in vitro bioactivity only for high bismuth oxide quantities. Bismuth oxide leaching out of the glass matrix was hardly detectable. CONCLUSION Bioactive glass can be modified with bismuth oxide to become radio-opaque.

Relationship between Nanohardness and Mineral Content of Artificial Carious Enamel Lesions

The aim of this study was to compare cross-sectional nanohardness, measured using an ultra-microindentation system, with mineral content, from transversal microradiography, of artificial enamel caries lesions. Sections (85 ± 10 µm) from 16 bovine enamel samples with artificial caries were prepared. The mineral content and cross-sectional nanohardness at known depths from the surface were compared. Both methods showed lesion profiles with a surface layer. The determination of nanohardness seems limited to lesions with a mineral content >45 vol%. There was a moderate linear relationship between mineral content and the square root of nanohardness (R2 = 0.81). It was concluded that the conversion of cross-sectional hardness into mineral content remains questionable and cannot be recommended.

pH changes in human dental plaque from lactose and milk before and after adaptation.

pH changes in human dental plaque in vivo from lactose and milk have been studied in four separate mouthrinse experiments. (1) pH was measured in plaque samples of 12 subjects before and after 6 weeks of frequent daily mouthrinsing with 10% lactose. The pH decreases were significantly more pronounced after the adaptation period than before (p < 0.001), 4 of the 12 subjects showing about the same low plaque pH from lactose as from glucose. (2) Similar to the previous experiment, frequent daily mouthrinsing with low-fat bovine milk in 10 subjects resulted in more pronounced pH decreases in plaque after an adaptation period of 4 weeks (p < 0.001). (3) Single mouthrinses, without any prior adaptation, with bovine standard milk, human breast milk, lactose-hydrolysed bovine standard milk, 5% lactose and 5% sucrose were compared regarding the effect on plaque pH in 7 subjects. All solutions resulted in pH falls. The most pronounced were found with sucrose, followed by the lactose-hydrolysed milk. (4) Bovine standard milk, 5% lactose and 10% sucrose were compared after a single mouthrinse in 5 subjects using interdental plaque pH wire telemetry. Lactose and milk were fermented more slowly than sucrose. In a separate study, acid production from lactose was also measured in two oral strains each of Streptococcus mutans, Streptococcus salivarius and Streptococcus sanguis. The results from these experiments indicated that at least part of the lactose transport and catabolism in all studied streptococcus strains seems to be regulated by inducible enzymes.