Induction and 3D reconstruction of caries-like lesions in an experimental dental plaque biofilm model.

The aim of this study was to examine an in vitro dental plaque model for volumetric assessment and 3D reconstruction of experimentally bacterial induced caries-like lesions. Twenty-three extracted, impacted human molars were coated with a varnish leaving a 3 x 3 mm window on the smooth surface. The teeth were coated with human saliva and Streptococcus sobrinus 6715 adhered onto the enamel via a sucrose dependent mechanism. The coated teeth were incubated for 1, 7, 14 and 28 days. At the end of each incubation period microhardness was measured on three sectioned teeth of each incubation period at the enamel surface and at 450 and 750 microm depth perpendicular to the enamel surface. The enamel surface was investigated by scanning electron microscopy (SEM) prior to embedding and serial sectioning of 12 other teeth. The serial sections were studied with polarization light microscopy to investigate subsurface demineralization. The outlines of the caries-like lesions were then traced consecutively on transparencies, digitized and three-dimensionally reconstructed to demonstrate the expansion of the lesion into enamel for volumetric assessment. Microhardness was significantly reduced on the enamel surface after 7, 14 and 28 days incubation. The SEM investigation showed a surface demineralization with dissolution of the prism cores after 28 days incubation. Polarization light microscopy demonstrated caries-like lesions with an irregular expansion into enamel. The results demonstrate that the described method produces caries-like lesions which can be used for further experimental studies regarding demineralization and remineralization processes.

The role of fructans on dental biofilm formation by Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus.

Dental plaque biofilm plays a pivotal role in the progression of dental diseases. Polysaccharides are of great importance in the ecology of the dental biofilm. We studied the effect of fructans, glucans and a mixture of both fructans and glucans, synthesized in situ by immobilized fructosyltransferase or glucosyltransferase, on the adhesion of Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus to hydroxyapatite beads coated with human saliva (sHA). The adhesion of A. viscosus to sHA was found to be fructan-dependent. Adhesion of both S. sobrinus and S. mutans was found to be mediated mainly by glucans, while the adhesion of S. gordonii was found to be both glucan- and fructan-dependent. Treatment with fructanase prior to A. viscosus adhesion resulted in a significant reduction in adhesion to sHA, while adhesion of S. sobrinus, S. mutans and S. gordonii was slightly influenced by fructanase treatment. Treatment with fructanase after adhesion of S. gordonii to sHA resulted in a significant reduction in their adhesion to sHA. Our results show that fructans may play a role in the adhesion and colonization of several cariogenic bacteria to sHA, thus contributing to the formation of dental plaque biofilm.

Streptococcus mutans in saliva of normal subjects and neck and head irradiated cancer subjects after consumption of honey.

The antibacterial activity of natural honey consumption has been examined in patients suffering from head and neck cancer who developed hyposalivation following irradiation treatment. Enumeration of total bacteria and streptococcus mutans was carried out in saliva of the patients and of a normal volunteer group before and after honey consumption. Total bacteria count was not significantly different between both groups, whereas the streptococcus mutans count decreased significantly in the experimental group following honey consumption.

A laboratory assessment of enamel hypoplasia of teeth with varying severities of dental fluorosis.

The effect of lifelong exposure to drinking-water containing fluoride on tooth enamel microhardness was investigated. Dental fluorosis of teeth from adult subjects, who lived continuously since birth in areas characterized by the hot climate of India, supplied by drinking-water containing between 0.5 and 8.7 parts/10 F, was estimated by the Dean score. Tooth enamel sections were examined from the enamel surface towards the dentino-enamel junction (DEJ) for microhardness. Separated enamel crowns were pulverized and analysed for fluoride. Regarding the distribution of the fluoride concentrations in the drinking-water, we selected a partition below and above 0.8 parts/10 F as a criterion for comparison between the results. Tooth enamel of humans from Israel living in a drinking-water area containing about 0.5 parts/10 F was also examined. Positive associations were evident between fluoride in drinking-water, fluoride concentrations in the bulk enamel and fluorosis selection. A significantly high inverse relationship was evident between the fluoride concentration of the drinking-water and the subsurface enamel microhardness. In similar fluoride-concentration drinking-water areas of India and Israel the microhardness of the subsurface enamel was less for the Indian teeth. The microhardness of the enamel near the DEJ for the three different water fluoride-concentration areas was not significantly different.

Effect of chloroform, xylene, and halothane on enamel and dentin microhardness of human teeth.

OBJECTIVE: The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. STUDY DESIGN: Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker's microhardness analysis. Vicker's microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared. RESULTS: A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time. CONCLUSIONS: Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.

The effect of propolis exposure on microhardness of human enamel in vitro.

Propolis is a resinous wax-like material that is used by bees as a glue-like matrix in their hives. The in vitro effect of propolis solutions was investigated on the microhardness of human dental enamel. The calcium concentration of the solution was 7.8 ppm, the pH values varied between 5 and 6. The fluoride concentration was negligible. The Vickers hardness number of exposed enamel showed a steady increase with the percentage of propolis in the solution. The microhardness increase may be attributed to particular components of mineralization activity in propolis.

Effect of amine fluoride-stannous fluoride containing toothpaste (Meridol) on plaque and gingivitis in adults: a six-month clinical study.

Treatments that aim to reduce the accumulation of bacteria on dental surfaces are considered today as the most efficient way of treating gingivitis and the resultant destruction of periodontal tissues. Mechanical plaque removal was found to be very effective in the control of gingival inflammation for most patients, but the supplement of toothpastes and mouthwashes with anti-plaque properties may benefit individuals with unperfected plaque control. The aim of the present study was to investigate the long-term effect of amine fluoride/stannous fluoride (AmF/SnF2) toothpaste on plaque levels and gingivitis in adults, as an additional measure to standard oral hygiene. One hundred and three adult subjects with gingivitis were divided into two randomised groups. One group used NaF toothpaste (control) and the second group AmF/SnF2 (Meridol) toothpaste. The subjects were examined every two months under double-blind conditions. The recorded parameters were plaque index (PlI), gingival index (GI) and bleeding on probing. The differences in PlI between baseline and the end of the study were statistically significant for both treatments, and no significant differences were found between the two treatment groups. There was a significant drop in GI between baseline and the concluding examination only for the AmF/SnF2 group, but the differences between the two treatment groups were not significant. A significant reduction in the percentage of bleeding sites during the six-month study period was found in the AmF/SnF2 group, but not in the control group. The results of the present study suggest that the long-term use of AmF/SnF2 toothpaste in adults may be of benefit to gingival health.

Effects of honey consumption on enamel microhardness in normal versus xerostomic patients.

The aim was to investigate the effect of honey on the microhardness of enamel in normal and xerostomic patients. Normal subjects and patients who were xerostomic after neck irradiation, wearing prosthetic appliances with slabs of human enamel inserted, were asked to consume a single teaspoonful of pure honey, pH 3.9. Measurements of the saliva pH were taken before, during and after a 5 min exposure to the honey. The pH of the honey-saliva mixtures decreased significantly from about 6 to 4 in both groups, returning to the baseline pH after the mixture was swallowed. The initial microhardness of the surface of the enamel slabs decreased significantly after consumption of a teaspoonful of the honey in the subjects with a regular saliva flow, whereas in the irradiated dry-mouth patients, no enamel microhardness decrease occurred. The supposed solubility-reducing factor present in honey which, according to the literature remains active in the absence of saliva, but will be inactivated by salivary enzymes, gives some support to the hypothesis that honey is less cariogenic in dry-mouth subjects. The absence of adequate controls in the present study prevents the investigation of how specific this effect is to honey.

Effect of amine and stannous fluoride on human neutrophil functions in vitro.

Amine fluoride (AmF)- and stannous fluoride (SnF2)-containing products were found to have a therapeutic effect on gingivitis and periodontitis. This effect was suggested to correlate with the antibacterial activity of the fluoride compounds. However, their effect on inflammatory cell function can also play a role in the therapeutic effect on gingival inflammation. The present study was designed to test the effects of AmF, SnF2, and an AmF/SnF2 combination on the function of human peripheral blood neutrophils, as compared with effects of chlorhexidine and salicylic acid. Neutrophils were isolated from human blood by ficoll centrifugation followed by dextran sedimentation. The neutrophils were pre-incubated with AmF, SnF2, or AmF/SnF2, followed by stimulation with fMLP. Cell vitality was verified by trypan-blue exclusion (> 95% vitality at all tested concentrations). Superoxide production was measured by cytochrome C reduction and the enzymatic activity of lysozyme and beta-glucoronidase by optical density measurement of substrate conversion. The results showed that AmF, SnF2, or AmF/SnF2 enhanced by two- to three-fold the superoxide release from fMLP-stimulated human neutrophils. Furthermore, the effective concentration of the AmF/SnF2 combination was several-fold lower than that of AmF or SnF2 alone (10 nM for AmF, 0.5 microM for SnF2, and 3 pM for SnF2/AmF). On the other hand, chlorhexidine and salicylic acid were found to reduce superoxide production by the cells. All the tested compounds had no effect on granular enzyme release by the stimulated neutrophils. The results suggest that AmF and SnF2 enhance the oxygen-dependent antibacterial activity of neutrophils. This effect may contribute to a more efficient elimination of bacteria from the periodontal environment, resulting in improvement in gingival health.

Antibacterial effect of propolis and honey on oral bacteria.

PURPOSE: To investigate the antibacterial properties of propolis and honey against oral bacteria in vitro and in vivo. MATERIALS AND METHODS: In vitro study: The antibacterial effects of propolis and honey on oral streptococci were determined using the broth method. Clinical study: The short-term antibacterial effect of propolis solution and honey on salivary total bacteria and Streptococcus mutans was tested in 10 volunteers. RESULTS: Propolis demonstrated an antibacterial effect both in vitro on isolated oral streptococci and in the clinical study on salivary bacterial counts. Honey induced bacteria growth at low concentrations, while at high concentrations honey had an inhibitory effect on bacterial growth in vitro. Salivary counts of total bacteria and Streptococcus mutans were lower for 1 hour after application of honey. The antibacterial effect of the honey tested may be attributed to its osmolarity effect.

Fluoride and hard cheese exposure on etched enamel in neck-irradiated patients in situ.

OBJECTIVES: The effect of a fluoride mouth rinse with hard cheese exposure was investigated on rehardening of an etched tooth enamel surface in subjects with radiation-induced hyposalivation in situ. METHODS: Ten patients, six males and four females of mean age 48 years, irradiated with 30 Gy per week for neck and head cancer, volunteered for the present intraoral study. The unstimulated saliva flow rate varied between 0.01 and 0.15 ml min-1. Enamel slabs, approximately 2 mm x 2 mm in size, cut from human molar teeth were embedded in self-curing acrylic resin to fit a microhardness tester. Hardness measurements were carried out on the polished and subsequently etched enamel surface, rinsed for 1 min in the mouth with 10 ml Meridol (GABA INT), containing 0.025% F as amine fluoride and stannous fluoride, and exposed alternatively to mastication of 20 g cheddar cheese for 5 min. RESULTS: Surface erosion of the enamel slabs decreased the mean hardness to a similar degree in all samples. The difference between the mean increased degrees of enamel microhardness following fluoride, fluoride and hard cheese, or repeated fluoride-cheese exposures was significant compared to the etched enamel values. The rate of rehardening derived from a second fluoride-cheese treatment was found to be improved significantly. It seems that the reduced saliva flow in xerostomic patients is sufficient to release bound calcium and phosphate from cheese products. CONCLUSIONS: It is suggested that for xerostomic patients frequent exposures to low-fluoride solutions combined with hard cheese consumption may prevent and remineralize initial demineralization.

The effect of topical fluoride agents on saliva secretion.

The aim of this study was to assess the possible influence of various topical fluoride agents on the rate of saliva secretion. Fifteen healthy volunteers, both males and females, aged 20-60 years, participated in this study. Aminfluorides and monofluorophosphate products in gel, toothpaste and rinse states were used. Each subject brushed or rinsed the teeth and mouth for 2 minutes. Secreted saliva was collected for 5 minutes. Salivary secretion was significantly greater after toothbrushing with aminfluoride compounds as compared to toothbrushing with monofluorophosphate. There was a tendency for an increased saliva flow rate with higher fluoride concentration of the aminfluoride.

Enamel rehardening by bread consumption.

PURPOSE: To investigate the in situ rehardening effect by white or whole-meal bread on softened enamel. MATERIALS AND METHODS: Twelve volunteers wearing orthodontic removable appliances participated in this study. The intraoral test was chosen for measuring microhardness of enamel slabs inserted into the dental appliance. Average microhardness of enamel was calculated at three stages: At start (baseline), after exposing the enamel slabs to a citrus beverage (pH 3.4) for 30 minutes in vitro as a softening agent, followed by intraoral exposure for a duration of 5 minutes to stimulated secreted saliva by parafilm chewing (control), or to 15g white- and wholemeal-bread mastication respectively (experimental). RESULTS: A significant rehardening of the softened enamel surfaces took place following mastication of the two bread samples and salivary secretion. The differences in the rehardening potentials of the bread samples as compared to that of saliva were not significant. From the conditions chosen for the experiment, there was no sufficient evidence to support the hypothesis that bread eating with calcium and phosphate concentrations at the existent levels will afford a significant greater rehardening than saliva alone.

Subgingival irrigation with amine fluoride-stannous fluoride gel in treated periodontal pockets.

PURPOSE: To evaluate the long-term effect of subgingival irrigations with amine fluoride mixed with stannous fluoride on the repopulation of bacteria in deep periodontal pockets (> 5 mm) following the active phase of non-surgical mechanical treatment. MATERIALS AND METHODS: A split-mouth design was utilized in eight periodontal patients and the effect of the treatment was evaluated by microbiological culturing and clinical parameters. RESULTS: Slight reduction in total anaerobe counts were detected in both treated and control sides, up to the first 5 weeks, followed by an increase in the counts reaching a plateau after 30 weeks. In contrast, black-pigmented bacteroides species (BPB) were significantly suppressed in the treated sides as compared to the control sides over the whole study period. The difference between the clinical parameters and between the tested and control sides, although in some points were found to be statistically significant, seem to have no clinical significance. The use of amine fluoride-stannous fluoride gel for irrigations of deep periodontal pockets as an adjunctive to conventional treatment, can prevent the repopulation of the pockets by BPB, which are considered to be a major group of periodontal pathogens.

Enamel rehardening with cheese in irradiated patients.

Radiotherapy of head and neck malignancies results in severe xerostomia which induces radiation caries. Hard cheese has potent anti-cariogenic effects, even with minimal salivary gland function. Eight patients irradiated for neck cancer volunteered for this study. The saliva flow rate varied between 0.0-0.15 ml/minute. In vitro etched enamel slabs, prepared from human teeth, were exposed intraorally to parafilm stimulated salivary secretion for 5 minutes or, alternatively, to cheese compounds and saliva due to masticating 20 gm hard cheese for 5 minutes. Microhardness measurements were carried out on the enamel surface at start (baseline), after etching and after rehardening. Stimulated saliva or cheese compounds and saliva, due to mastication, induced rehardening of surface enamel in both, non-irradiated and irradiated subjects. The rehardening was significantly increased in the irradiated group consuming cheese as compared to rehardening by stimulated saliva only and not significantly less of that achieved in non-irradiated subjects. Rehardening achieved with stimulated saliva in irradiated patients was of a borderline-significant lower degree in comparison to non-irradiated subjects. The reduced rehardening capacity of a decreased saliva flow in irradiated patients may be complemented by cheese compounds. For xerostomic patients, hard cheese consumption may be regarded as effective to keep initial caries under control.

Solubility of irradiated rat molar teeth.

The solubility of molar teeth of rats exposed to irradiation and fluoridated drinking water was studied. Irradiation resulted in an increased molar enamel resistance enhanced by fluoridated drinking water.

Enamel rehardening by soft cheeses.

The in situ rehardening effect by soft cheeses: unsweetened, sucrose-sweetened and strawberry marmalade-flavored, pH 4.5, 4.25 and 4.0 as compared to secreted saliva, was investigated on softened enamel. Ten volunteers wearing orthodontic removal appliances participated in the study. The intraoral test was chosen for measuring microhardness of enamel slabs inserted into the dental appliance. Average microhardness was calculated at three stages: at start (baseline), after exposing the enamel slabs to a citrus beverage (pH 3.3) for 30 minutes in vitro as a softening factor and then intra-oral exposure during 5 minutes to 125 g soft cream cheese mastication, unsweetened and sweetened (experimental), or to saliva secretion, pH 6.8, only by mouth movements (control). Significant rehardening effects on the softened enamel surfaces took place following mastication of the various soft cheeses and salivary secretion. The differences in the rehardening potentials of the cheeses as compared to that of saliva were significant. The rehardening effect of the cheeses decreased (not significantly) in the following order: unsweetened cheese, sucrose-sweetened marmalade flavored cheese and sucrose-sweetened cheese. In spite of the acidic pH of the soft cheese substrates,--the buffering capacity of the protein compounds and the Ca,PO4 ions neutralize a softening effect--the rehardening effect is probably due to an uptake of Ca and PO4 ions by the softened surface enamel from the cheese bolus consumed over the entire 5-minute period.

Effect of fluoride varnish on the retentive strength of provisional crowns luted with various temporary cements.

The retention of temporary crowns was studied with the use of a fluoride varnish (Duraphat) combined with various temporary cements. The mixture of Duraphat varnish and cement improved retention, with the exception of Opotow cement. Applying Duraphat varnish to the tooth surface before cementation enhanced the retentive strength of Tempbond, weakened the retention of Freegenol, but had no effect on Opotow cement. A "transfer effect" was observed, inasmuch as the Duraphat varnish encouraged adherence of the cement to the tooth structure rather than to the temporary crown.