Antibacterial activity of dental gels containing combinations of amine fluoride, stannous fluoride, and chlorhexidine against cariogenic bacteria

The in vitro susceptibility of Streptococcus mutans, S. sobrinus and Lactobacillus casei to dental gels containing various combinations of amine fluoride (AmF 297), stannous fluoride (SnF2), and chlorhexidine (CHX) was studied. The combination of AmF-SnF2 with a total fluoride content of 1.2% was the most effective against mutans streptococci but not against L. casei. At notably lower total fluoride concentration (0.4%), AmF as such or combined with SnF2, was significantly less effective against mutans streptococci than CHX or CHX-AmF-SnF2 combinations. CHX-AmF combination was a slightly more potent inhibitor of streptococcal growth than CHX-NaF. With L. casei the differences between various gels were small but CHX alone seemed to be the most effective. Of the studied agents, CHX seemed to be the most potent individual chemotherapeutic compound whose activity against S. mutans could be enhanced by combining it with AmF. However, clinical experiments are required to test the in vivo antibacterial efficacy of CHX-AmF and AmF-SnF2 combinations which were most effective in our in vitro experiments.     

Comparative antibacterial effects of chlorhexidine and stannous fluoride-amine fluoride containing dental gels against salivary mutans streptococci

Abstract— Forty-five young adults were divided into three groups of equal size and given a professional toothcleaning (3 times during 1 wk) with dental gels containing either chlorhexidine (CHX, 1%), or a SnF₂-amine fluoride (AmF) combination (F⁻ content 1.20%). The control group received toothcleaning with a placebo gel. The study was done double blind. The number of salivary mutans streptococci was monitored for 11 wk after the gel treatment using both mitis-salivarius-bacitracin agar plates and the chairside method based on the adhesion of mutans streptococci on plastic strips (DentocuIt-SM Strip mutans). Professional toothcleaning with a CHX gel was clearly most effective ( P < 0.001) but the baseline levels of streptococci returned in 11 wk. SnF₂-AmF gel also reduced significantly ( P < 0.001) mutans streptococci but recolonization occurred already in 7 wk. Placebo gel, i.e. professional toothcleaning as such, did not show any statistically significant effect on the numbers of salivary mutans streptococci. None of the treatments affected the levels of lactobacilli or the total aerobic flora in saliva samples. Professional toothcleaning with a CHX gel, or with a SnF₂,-AmF gel, can be regarded as an alternative to the commonly used, but more patience demanding, application of gel in mouth trays at home for individuals with high caries activity.     

Susceptibility of Streptococcus mutans and Streptococcus sobrinus to antimicrobial agents after short-term oral chlorhexidine treatments

Effects of three different types of short-term applications (1–3 limes during 1 week) of chlorhexidine (1 or 40%) on the susceptibility of 863 clinical isolates of Streptococcus mutans and 53 isolates of Streptococcus sobrinus from 58 subjects were studied. Chlorhexidine-resistant isolates were not found either before or after the treatment. The minimum inhibitory concentrations (MICs) to chlorhexidine of all isolates of S. mutans were ≤1 μg/ml, and of S. sobrinus ≤2 μg/ ml. S. mutans and S. sobrinus were also susceptible to ampicillin, penicillin, cefuroxime, and tetracycline. In conclusion, different short-term chlorhexidine regimens do not induce resistance in S. mutans or S. sobrinus and, furthermore, these species have so far retained their susceptibility to common antibiotics.     

Activity of amine-stannous fluoride combination and chlorhexidine against some aerobic and anaerobic oral bacteria

The in vitro susceptibility of 128 bacterial strains was tested to amine fluoride-stannous fluoride (AmF + SnF) and chlorhexidine (CHX) solutions. Actinobacillus actinomycetemcomitans, Streptococcus mutans, and Bacteroides intermedius were among the species investigated. The 50% and 90% minimal inhibitory concentrations (MICs) were assessed by an agar dilution method. The MIC ranges for A. actinomycetemcomitans were 2-32 micrograms/ml for CHX and 0.25-64 micrograms/ml for AmF + SnF. The respective values for S. mutans were 0.5-8 micrograms/ml (CHX) and 2-8 micrograms/ml (AmF + SnF); and 4-8 micrograms/ml (CHX) and 2-4 micrograms/ml (AmF + SnF) for B. intermedius. Streptococcus faecalis and Staphylococcus aureus were most resistant of the control strains (MIC 64 micrograms/ml to CHX and 32 micrograms/ml to AmF + SnF, respectively). Thus, both solutions tested exerted a definite inhibitory action on the dental plaque pathogens studied.     

Salivary mutans streptococci and dental caries in three-year-old children after maternal exposure to chewing gums containing combinations of xylitol,sorbitol, chlorhexidine,and fluoride

The aim of this study was to evaluate the effect of maternal use of chewing gums containing combinations of xylitol, sorbitol, chlorhexidine, and fluoride on salivary mutans streptococci (MS) counts and caries prevalence in the mothers' 3-year-old children. After screening 416 women with newborn babies, 173 mothers with high counts of salivary MS were randomly assigned into 3 experimental chewing gum groups containing (A) xylitol (n=61), (B) chlorhexidine/xylitol/sorbitol (n=55), and (C) sodium fluoride/xylitol/sorbitol (n=57). Mothers with low or medium MS counts formed a reference group (D) without any intervention (n=232). The participants in the experimental groups were instructed to chew one piece of the gum for 5 min 3 times a day. The chewing regimen started when the child was 6 months old and was terminated 1 year later. The outcome measures were salivary MS counts and caries prevalence at the age of 3 years. Bacterial enumeration was carried out with a chair-side technique and caries (defs) was scored by clinical examination. Medium and high counts of salivary MS were found in 13%, 16%, and 22% in groups A, B, and C, respectively. The mean defs was 0.1 in group A, 0.2 in group B, and 0.4 in group C. The differences concerning salivary MS and caries were not statistically significant. The MS counts and caries prevalence in children of mothers with low MS counts (group D) were similar to those found in groups A and B. In conclusion, lower but non-significant levels of salivary MS and dental decay were observed in 3-year-old children to mothers who used high-content xylitol gums compared with those who used lower amounts of xylitol. The efficiency of this type of targeted intervention in a low-caries community may be questioned.     

Short-term bactericidal activity of chlorhexidine gel, stannous fluoride gel and amine fluoride gel tested in periodontal pockets

The short-term bactericidal effect of 2% chlorhexidine gel, 4% stannous fluoride gel or amine fluoride gel containing 1.25% fluoride on the subgingival microflora was determined in 40 periodontal pockets of 10 patients. The antimicrobial gels or placebo gel were applied in 5-9 mm deep periodontal pockets 3 times within 10 min. Before and 30 min after the applications, samples were taken of the subgingival microflora for determination of the total number of bacteria as well as the number of black pigmented Bacteroides. Reductions of the total number of bacteria were found in all test groups. The reductions found in the pockets treated with chlorhexidine gel or stannous fluoride gel were significantly greater than the reduction found in the pockets treated with a placebo gel. A significant reduction of black-pigmented Bacteroides was found after treatment with chlorhexidine gel or amine fluoride gel. It is concluded that 2% chlorhexidine gel or 4% stannous fluoride gel has a more than 99% reduction effect on the microflora of periodontal pockets within 30 min after application.     

The antibacterial activity of chlorhexidine digluconate against Streptococcus mutans biofilms follows sigmoidal patterns

The aim of this study was to determine the pattern of the antibacterial activity of chlorhexidine digluconate (CHX) against mature Streptococcus mutans biofilms. Streptococcus mutans biofilms were formed on saliva‐coated hydroxyapatite discs and then treated with 0–20% CHX, once, three times, or five times (1 min per treatment) during the period of mature biofilm formation (beyond 46 h). After the treatments, the colony‐forming unit (CFU) counts of the treated biofilms were determined. The pH values of the spent culture medium were also determined to investigate the change in pH resulting from the antibacterial activity of CHX. The relationships between the concentration of CHX and the CFU counts and the concentration of CHX and culture medium pH, relative to the number of treatments performed, were evaluated using a sigmoidal curve‐fitting procedure. The changes in CFU counts and culture medium pH followed sigmoidal curves and were dependent on the concentration of CHX (R² = 0.99). The sigmoidal curves were left‐shifted with increasing number of treatments. Furthermore, the culture‐medium pH of the treated biofilms increased as their CFU counts decreased. The lowest CHX concentration to increase culture‐medium pH above the critical pH also decreased as the number of treatments increased. These results may provide fundamental information for selecting the appropriate CHX concentrations to treat S. mutans biofilms.     

Inhibition of plaque formation and plaque acidogenicity by zinc and chlorhexidine combinations

Abstract – Zinc ions and chlorhexidine (CH) were found to exhibit a synergistic inhibitory effect on in vitro growth of S. sobrinus OMZ 176 and of S. sanguis 10556. A clinical mouthrinsing experiment was performed in a group of 10 volunteers to assess the plaque-inhibiting capacity of this combination. Sucrose enhanced plaque accumulations were assessed (Plaque Index, Silness & Löe) after 4 days of twice daily mouthrinses with 10 ml aqueous solutions of either 10.0 mM zinc or 0.55 mM CH, or with a combination of zinc ions and CH, during which period no mechanical toothcleaning was performed. The Zn–CH combination showed improved inhibition properties compared to the individual agents. The effects on plaque acidogenicity of 8.0 mM zinc, 0.44 mM CH, and of zinc and CH in combination were also assessed in a test panel of five volunteers. The Zn–CH combination inhibited acid production by dental plaque significantly (P< 0.05) more than the individual agents 1 h 30 min after a single rinse.     

Comparative antibacterial effects of chlorhexidine and stannous fluoride-amine fluoride containing dental gels against salivary mutans streptococci.

Forty-five young adults were divided into three groups of equal size and given a professional toothcleaning (3 times during 1 wk) with dental gels containing either chlorhexidine (CHX, 1%), or a SnF2-amine fluoride (AmF) combination (F- content 1.20%). The control group received toothcleaning with a placebo gel. The study was done double blind. The number of salivary mutans streptococci was monitored for 11 wk after the gel treatment using both mitis-salivarius-bacitracin agar plates and the chairside method based on the adhesion of mutans streptococci on plastic strips (Dentocult-SM Strip mutans). Professional toothcleaning with a CHX gel was clearly most effective (P less than 0.001) but the baseline levels of streptococci returned in 11 wk. SnF2-AmF gel also reduced significantly (P less than 0.001) mutans streptococci but recolonization occurred already in 7 wk. Placebo gel, i.e. professional toothcleaning as such, did not show any statistically significant effect on the numbers of salivary mutans streptococci. None of the treatments affected the levels of lactobacilli or the total aerobic flora in saliva samples. Professional toothcleaning with a CHX gel, or with a SnF2-AmF gel, can be regarded as an alternative to the commonly used, but more patience demanding, application of gel in mouth trays at home for individuals with high caries activity.     

Antimicrobial and antiplaque effects of a chlorhexidine and Triton X-100 combination

Abstract – This study aimed to assess the in vitro antimicrobial effect and in vivo plaqueinhibiting capacity of chlorhexidine (CH) combined with the nonionic detergent Triton X-100. Synergistic inhibition was observed by the combination of Triton X-100 and CH on in vitro growth of S. sobrinus OMZ 176 and of S. sanguis 10556. In the clinical experiments, 10 subjects rinsed twice dally with 10 ml aqueous solutions of 11.6 mM Triton X-100, and 0.55 mM CH, and with a combination of the two agents. All mechanical oral hygiene was suspended during the test periods. Sucrose enhanced plaque accumulations were recorded after 4 days of rinsing. The combination of CH-Triton X-100 decreased plaque accumulations significantly compared to placebo, but was less effective than CH alone ( P <0.05). Thus no beneficial clinical effect was gained by combining the nonionic agent Triton X-100 with the cationic agent CH. The results also clearly demonstrate that additions which increase the antibacterial activity of CH do not necessarily coincide with improved in vivo antiplaque efficacy.     

Prolonged oral reduction of Streptococcus mutans in humans after chlorhexidine disinfection followed by fluoride treatment

Abstract – The effect of oral chlorhexidine gel treatment supplemented with fluoride applications was studied in subjects with high salivary levels of S. mutans. In two experiments short-term treatment with a 1% chlorhexidine gel was followed by applications of either a 1% NaF gel daily for 2 weeks or a 1% NaF gel daily for 6 weeks supplemented twice with topical application of an 8% SnF₂ solution. The salivary numbers of S. mutans were lower in the test group than in the placebo group after 6 and 12 weeks in experiments 1 and 2, respectively, and considerably lower than the pretreatment values. The findings show that fluoride applications can be a valuable adjunct to chlorhexidine treatment for combatting S. mutans.     

定量聚合酶链反应检测致龋性变形链球菌

目的 创建一种临床定量检测致龋性变形链球菌的分子生物学方法。方法 采用靶基因与参照基因同步扩增法，根据变形链球菌葡聚糖酶（dexA)基因序列，设计一对特异性引物，以pET23b质粒DNA为参照基因。对196名儿童的唾液样品进行定量PCR检测并进行常规培养法的对比研究。结果 196份唾液样品定量PCR检测致龋性变形链球菌≥10^8CFU/L，唾液的检出率为91.3%。与常规培养计量法的对比符合率为94.9%。结论 变形链球菌PCR定量检测是一种早期发现龋病活性的新方法，具有快速可靠、特异性强、符合率高等特点，有广泛的临床应用前景。     

洗必泰对变形链球菌、远缘链球菌耐氟菌株与亲代菌株生长抑制的测定

目的：通过洗必泰对变形链球菌、远缘链球菌耐氟菌株与亲代菌株生长抑制的测定，探讨一种新的防龋途径。方法：将醋酸洗必泰液稀释成不同的浓度，分别加入变形链球菌、远缘链球菌及耐氟菌株菌悬液，测得最小抑菌浓度（MIC）、最小杀菌浓度（MBC）。结果：洗必泰对变形链球菌、远缘链球菌及耐氟菌株均有抑菌、杀菌作用，4种细菌最小抑菌浓度（MIC）均值为338μg/L，最小杀菌浓度（MBC）均值为375μg/L。结论：洗必泰可有效抑制变形链球菌、远缘链球菌及耐氟菌株生长。     

Human strains of mutans streptococci show different cariogenic potential in the hamster model

The cariogenic potential of fresh humans strains of Streptococcus mutans and Streptococcus sobrinus was examined in hamsters maintained on a high sucrose diet. The strains 1B 16 (S. mutans) and B13 (S. sobrinus) isolated 20-25 yrs ago served as positive controls. Three series of experiments were run. Some strains were tested once and some strains were tested in all 3 experiments. The animals infected with S. sobrinus strains generally showed lower caries scores than those infected with S. mutans strains. Among the groups infected with the different strains of S. mutans the caries scores varied. In one of the experiments the caries score of the animals infected with one of the Icelandic S. mutans strains was significantly higher than that of the positive control group and the group infected with one of the fresh Swedish isolates. Thus, different strains of mutans streptococci where shown to induce varying caries activity in the hamster model.     

Oral implantation of Streptococcus mutans in man with and without prior chlorhexidine mouthrinses

Abstract — Oral implantation of streptomycin resistant S. mutans was enhanced when chlorhexidine mouthrinses were applied before implantation. The difference in recovery of implanted bacteria between implantations with and without prior chlorhexidine mouthrinses was significant 9 days ( P<0.05 ), 15 days ( P <0.05) and 28 days ( P <0.01) after implantation. After 28 days implanted bacteria were no longer detected in any of the 20 test subjects when chlorhexidine was not used prior to implantation, but persisted in 11 subjects when chlorhexidine was used.     

Mechanism of inhibition of glycolysis in Streptococcus mutans NCIB 11723 by chlorhexidine

Inhibition of the rate of acid production from glucose by the cells of Streptococcus mutans was directly related to the concentrations of 0.075 to 0.20 mM chlorhexidine. Lactate production was inhibited to a greater extent than acetate and formate. Quantification of glycolytic intermediates revealed that the steps in glycolysis inhibited by chlorhexidine were the reactions catalyzed by phosphofructokinase and glyceraldehyde 3-phosphate dehydrogenase and/or phosphoglycerate kinase. However, the activities of these enzymes were not decreased in cells treated with the inhibitor. It was demonstrated that chlorhexidine caused leakage of metabolites from the cells. Our results indicate that the decreased rate of glycolysis caused by chlorhexidine is due to the leakage of metabolic intermediates and not to direct effects on enzymes involved in glycolysis by S. mutans NCIB 11723.     

Transient reduction of Streptococcus mutans interdentally by chlorhexidine gel

Abstract – Chlorhexidine gel was applied interproximalJy with the intent to reduce Streptococcus mutans at these sites. Bacterial samples, were obtained using toothpicks, which were inserted in eachinterproximal space and then immediately pressed against agar plates, selective for S. mutans. Duplicate bacterial samples of non-treated subjects showed that this method gave reproducible results. Using a split mouth technique, 10 subjects were exposed to short term chlorhexidine exposures of varied intensity. At the baseline sampling about 90% of the sites showed growth of S. mutans. One week after the chlorhexidine applications about 55% were infected. After 40 d S. mutans were back to about baseline levels except for the most intensively treated interproximals, which showed 75% infected sites. Thus, at many sites the reduction of S. mutans was only transient. Four subjects with more than 1 million S. mutans per ml saliva participated in a study where salivary andinterproximal levels of S. mutans were compared after a rinsing period with chlorhexidine lasting for 2 weeks. The effect of the rinses varied individually, but it was noted that several inter proximal spaces could be infected, even if the saliva numbers did not reach detectable levels of S. mutans.     

Clinical and microbiological effects of local chlorhexidine applications

AIM: To study the effects of an application of chlorhexidine varnish (40%) on dental plaque. DESIGN: Randomised controlled clinical trial. SUBJECTS: 40 patients (50% females), aged 25-34 years after undergoing any necessary restorative treatment. Exactly one half of these individuals practiced good oral hygiene, the efforts of the others were poor. METHOD: Test groups received a chlorhexidine varnish application, the control group received a placebo varnish. Initially and after 2 and 6 weeks, a modified Dentocult SM-test, bleeding on probing, and a plaque index (Quigley-Hein) were recorded. RESULTS: In contrast to the control group, improvements in plaque index and bleeding on probing scores were found in patients with poor oral hygiene. The results of the Dentocult SM-tests showed a considerable reduction of streptococcus colonisation. The test group with good oral hygiene showed only slight improvement of the examined indices after chlorhexidine application. The index parameters of all patients of the placebo groups remained unchanged over the examination time period. CONCLUSION: The application of a chlorhexidine varnish reduced the quantity of the Streptococcus mutans colonies significantly and improved clinical parameters in patients with elevated plaque accumulation.