Clinical Effects of Sugar Substitutes on Cariogenic Bacteria: A Systematic Review and Meta-Analysis

BACKGROUND

The use of sugar substitutes in food products has recently increased. Limited information regarding the role of various sugar substitutes in caries prevention was found. This systematic review and meta-analysis was conducted to investigate the effects of sugar substitute consumption on reducing cariogenic bacteria in dental plaque and saliva.

METHODS

We systematically searched PubMed, EMBASE, and Web of Science (inception to July 2023) for prospective controlled trials published in English and investigated the effects of sugar substitute consumption on cariogenic bacteria in dental plaque and saliva. The primary outcome was the changes in cariogenic bacteria. Two independent reviewers screened the papers. Quality was assessed using the Cochrane risk-of-bias tools.

RESULTS

From 977 studies identified, 32 trials were included. Almost half (14/32, 44%) of the included studies had a high risk of bias. Almost all (31/32, 96.88%) were investigations of xylitol and other sugar alcohols (low-intensity sweeteners), such as sorbitol, erythritol, and maltitol. Only one trial investigated stevia, a high-intensity sweetener, whereas no studies on other high-intensity sweeteners, such as sucralose, saccharin, or aspartame, were found. Almost all studies (30/32, 93.75%) showed the consumption of low-intensity sweeteners led to a significant reduction of different types of cariogenic bacteria. The results of the meta-analysis showed that consumption of low-intensity sweeteners led to a significant reduction of cariogenic bacteria in both dental plaque and saliva compared to no treatment.

CONCLUSION

The consumption of low-intensity sweeteners helps reduce cariogenic bacteria in dental plaque and saliva. There is limited clinical evidence regarding the role of high-intensity sweeteners in reducing cariogenic bacteria.

Effects of Hydrogen-rich Water on Cariogenic Bacteria

Context

Some kinds of electrolysed water have been reported to exhibit antioxidant and bactericidal activity. However, studies on the effect of electrolysed hydrogen-rich water (EHW) with a neutral pH on cariogenic bacteria are limited.

Aim

This study aimed to evaluate the feasibility of using EHW as a mouthwash by examining its various effects on cariogenic bacteria.

Materials and Methods

To test the bactericidal and anti-biofilm formation effects of EHW on Streptococcus mutans and Streptococcus sobrinus, bacterial growth curves, colony-forming unit (CFU) counts, and crystal violet staining of biofilms were examined after exposing the bacterial pellets to EHW or tap water as a control for one minute. In addition, the expressions of glucosyltransferase and glucan-binding proteins encoding genes were examined using real-time PCR.

Results

Bacterial growth and biofilm formation were inhibited, and the number of CFUs was significantly reduced in the EHW group compared to the control group. The expression of genes encoding glucosyltransferases (gtfB, gtfC, and gtfI) and glucan-binding proteins (gbpC and dblB) were also decreased in the EHW group compared to the control.

Conclusions

Exposing cariogenic bacteria to EHW at neutral pH for one minute can effectively inhibit bacterial growth and biofilm formation in vitro, suggesting that EHW is a promising mouthwash.

[Research Updates: Cariogenic Mechanism of Streptococcus mutans]

The prevalence of dental caries remains high, posing a major burden on the public health of the global society. Microorganisms are the main cause of dental caries, among which Streptococcus mutans ( S. mutans) is one of the most widely recognized cariogenic bacteria. In recent years, the progress in research technology enabled the academic circle to conduct more in-depth research into caries-inducing S. mutans at the DNA, RNA and protein levels, and to gain thereby a new understanding of the surface structure and extracellular matrix composition of S. mutans. In this paper, we summarized recent findings on the cariogenic mechanism of S. mutans in order to help reveal more targets and potential approaches for the future development of caries prevention agents that target S. mutans, and to promote the development of dental caries prevention campaign.

Anti-Streptococcus mutans and anti-biofilm activities of dextranase and its encapsulation in alginate beads for application in toothpaste

Background

The accumulation of plaque causes oral diseases. Dental plaque is formed on teeth surfaces by oral bacterial pathogens, particularly Streptococcus mutans, in the oral cavity. Dextranase is one of the enzymes involved in antiplaque accumulation as it can prevent dental caries by the degradation of dextran, which is a component of plaque biofilm. This led to the idea of creating toothpaste containing dextranase for preventing oral diseases. However, the dextranase enzyme must be stable in the product; therefore, encapsulation is an attractive way to increase the stability of this enzyme.

Methods

The activity of food-grade fungal dextranase was measured on the basis of increasing ratio of reducing sugar concentration, determined by the reaction with 3, 5-dinitrosalicylic acid reagent. The efficiency of the dextranase enzyme was investigated based on its minimal inhibitory concentration (MIC) against biofilm formation by S. mutans ATCC 25175. Box-Behnken design (BBD) was used to study the three factors affecting encapsulation: pH, calcium chloride concentration, and sodium alginate concentration. Encapsulation efficiency (% EE) and the activity of dextranase enzyme trapped in alginate beads were determined. Then, the encapsulated dextranase in alginate beads was added to toothpaste base, and the stability of the enzyme was examined. Finally, sensory test and safety evaluation of toothpaste containing encapsulated dextranase were done.

Results

The highest activity of the dextranase enzyme was 4401.71 unit/g at a pH of 6 and 37 °C. The dextranase at its MIC (4.5 unit/g) showed strong inhibition against the growth of S. mutans. This enzyme at 1/2 MIC also showed a remarkable decrease in biofilm formation by S. mutans. The most effective condition of dextranase encapsulation was at a pH of 7, 20% w/v calcium chloride and 0.85% w/v sodium alginate. Toothpaste containing encapsulated dextranase alginate beads produced under suitable condition was stable after 3 months of storage, while the sensory test of the product was accepted at level 3 (like slightly), and it was safe.

Conclusion

This research achieved an alternative health product for oral care by formulating toothpaste with dextranase encapsulated in effective alginate beads to act against cariogenic bacteria, like S. mutants, by preventing dental plaque.

Opportunities for caries prevention using an ion-releasing coating material: a randomised clinical study

Ion-releasing materials (containing fluoride and boron, for example) have shown caries-preventive effects in vitro. The purpose of the present study was to investigate the impact of multi-ion-releasing coating material on pH stabilisation, plaque accumulation and the bacterial composition of dental plaque during a time period of 90 days. The null hypothesis tested here was that the evaluated material would not show any differences in pH stabilisation, plaque accumulation or bacterial composition compared with control material.

The study was carried out as a double-blind, split-mouth, randomised, controlled clinical trial in 28 volunteers. Over the evaluation period (days 4, 30, 60 and 90), pH measurements, plaque index and plaque sampling for bacterial analyses were conducted in a calibrated, standardized manner. The study received ethical permission and was carried out in accordance with the Helsinki Declaration.

A significant difference was observed, with less plaque accumulation over time in the subjects in whom the ion-releasing material was applied in comparison to the non-active group. No significant difference was evident in terms of either pH stabilisation or plaque levels of mutans streptococci.

The null hypothesis relating to plaque accumulation was rejected, with a lower plaque index shown for the test group up to 60–90 days. No adverse effects during the observation period were observed. Since the studied cohort was healthy from a caries perspective, more clinical studies are needed to further evaluate the caries-prevention potential of the ion-releasing material in other patient groups.

Dental Caries and Risk Factors in Swedish Adolescents about to Start Orthodontic Treatment with Fixed Appliances

AIM

The aim of this study is to investigate the caries situation in a group of Swedish adolescents, who were scheduled for orthodontic treatment with fixed appliances.

MATERIALS AND METHODS

An age- and gender-matched control group was selected from the same city (Malmö, Sweden). Caries and fillings on smooth surfaces and fillings on occlusal surfaces were diagnosed clinically and caries and fillings on approximal surfaces by bitewings. Numbers of mutans streptococci (MS) and lactobacilli (LB) were analyzed in saliva.

RESULTS

There were no significant differences regarding manifest caries lesions and fillings on smooth surfaces. Numbers of occlusal-filled surfaces (FS) and approximal decayed and filled surfaces were around 10%, but did not differ between the groups. However, 53% had approximal enamel caries lesions in the test group and 46% in the control group. The prevalence of approximal decayed surfaces (DS) and FS was low in both groups, 0.57 ± 1.41 in the test group and 0.65 ± 1.38 in the control group (p > 0.05), i.e., somewhat more DS in the control group (p < 0.05). Most individuals had low/medium counts of cariogenic bacteria in their saliva and less than 10% high counts in both groups.

CONCLUSION

Most Swedish adolescents who have been scheduled for treatment with fixed appliances appear to have a low-to-medium caries risk nowadays. However, around 10% of all approximal tooth surfaces of premolars/molars had enamel caries and one-third of the individuals had medium/high counts of cariogenic bacteria in their saliva, which may be risk factors for future caries during orthodontic treatment.

CLINICAL SIGNIFICANCE

Bitewing radiographs are important before starting orthodontic treatment and approximal caries and many cariogenic bacteria may be risk factors for orthodontic treatment.

Human Pulp Fibroblast Implication in Phagocytosis via Complement Activation

INTRODUCTION

Previous works have shown that human pulp fibroblasts synthetize all complement components. Local complement activation in the dental pulp is known to be involved in inflammation and regeneration and also in pathogen destruction through membrane attack complex formation. Bacterial elimination by complement-mediated phagocytosis implies microorganism opsonization with the complement C3b protein, which is recognized by specific phagocytic cell CR1 receptors for subsequent intracellular destruction. This work was designed to find out whether pulp fibroblasts produce C3b and check its subsequent implication in bacteria phagocytosis.

METHODS

The expression of C3b was investigated in carious and healthy human pulp tissues. To simulate a bacterial infection in vitro, cultured human pulp fibroblasts were stimulated with lipoteichoic acid, and C3b secretion was quantified by an enzyme-linked immunosorbent assay. C3b fixation on bacteria (opsonization) and the inflammatory THP-1 cell complement receptor 1 was studied by immunofluorescence. A gentamycin protection assay was used to check the implication of C3b secretion by fibroblasts in bacteria phagocytosis.

RESULTS

Pulp cells constitutively express C3b in vivo, and cultured pulp fibroblasts produce C3b. We observed a fixation of this C3b protein on the bacterial surface (opsonization) and the THP-1 CR1 receptor. This recognition leads to a significant increase in bacteria phagocytosis.

CONCLUSIONS

These results showed that pulp fibroblasts mediate the process of phagocytosis by producing the complement C3b protein and opsonizing bacteria. This highlights a significant role of fibroblasts in the dental pulp local regulation of inflammation.

Influence of black tea on Streptococcus mutans and Lactobacillus levels in saliva in a Saudi cohort

Objectives

Dental caries are associated with high counts of Streptococcus mutans (SM) and Lactobacillus (LB) and low saliva buffering capacity (BC). This study aimed to evaluate the antimicrobial activity of black tea on salivary cariogenic microflora, SM and LB species in an adult population. Antimicrobial activity was measured from the number of colony forming units (CFUs) of SM and LB, and BC of saliva.

Methods

In this prospective experimental study, unstimulated saliva samples were acquired from the participants before, immediately after, and 1 h after drinking tea by collecting saliva in sterilised containers. Samples were taken to the laboratory for incubation and subsequent counting. SM and LB counts and BC of saliva were calculated using the caries risk test (CRT).

Results

A total of 21 participants, 13 males and 8 females, with a mean age of 32.6 ± 8.02, were recruited in this study. Black tea had no significant effect on reducing the cariogenic bacterial counts (p > 0.05).

Conclusion

Based on this study, it can be deduced that black tea exhibits an insignificant antimicrobial effect against Streptococcus mutans and Lactobacillus bacteria.

Increasing salivary IgA and reducing Streptococcus mutans by probiotic Lactobacillus paracasei SD1: A double-blind, randomized, controlled study

Background/purpose

Our previous study revealed that probiotic Lactobacillus paracasei SD1 could reduce mutans streptococci as evaluated by cultivation-method as well as stimulate innate immunity. This study aimed to further investigate the effect of the probiotic on various oral bacteria by real-time PCR and salivary IgA levels.

Materials and methods

Forty children were included by randomization from either probiotic or control group in the previous study. The probiotic or control received milk-powder with or without L. paracasei SD1, respectively once daily for 6 months. Saliva were collected at baseline 3-, 6-, and 12-months and were evaluated for total bacteria, total lactobacilli (TL), L. paracasei/L. casei (LP/LC), total streptococci (TS) and Streptococcus mutans using the real-time PCR. The salivary IgA (sIgA) was examined using the ELISA method.

Results

All target bacterial levels were not significantly different at baseline in both groups. After milk-powder consumption, TL and LP/LC levels were significantly increased in the probiotic group, whereas TS and S. mutans levels were significantly decreased compared to baseline. TS and S. mutans levels were significantly lower, while the sIgA was greater in the probiotic compared to the control group. In the probiotic group, a positive correlation was found between LP/LC and sIgA, while negative correlations were observed between TS or S. mutans levels and sIgA.

Conclusion

L. paracasei SD1 could control S. mutans level and could stimulate sIgA. Results indicate that the L. paracasei SD1 strain may have a benefit for prevention of dental caries.

Gene expression and protein synthesis of esterase from Streptococcus mutans are affected by biodegradation by-product from methacrylate resin composites and adhesives

An esterase from S. mutans UA159, SMU_118c, was shown to hydrolyze methacrylate resin-based dental monomers.

OBJECTIVE

To investigate the association of SMU_118c to the whole cellular hydrolytic activity of S. mutans toward polymerized resin composites, and to examine how the bacterium adapts its hydrolytic activity in response to environmental stresses triggered by the presence of a resin composites and adhesives biodegradation by-product (BBP).

MATERIALS AND METHODS

Biofilms of S. mutans UA159 parent wild strain, SMU_118c knockout strain (ΔSMU_118c), and SMU_118c complemented strain (ΔSMU_118cC) were incubated with photo-polymerized resin composite. High performance liquid chromatography was used to quantify the amount of a universal 2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA)-derived BBP, bishydroxy-propoxy-phenyl-propane (bisHPPP) in the media. Fluorescence in situ hybridization (FISH) and quantitative proteomic analysis were used to measure SMU_118c gene expression and production of SMU_118c protein, respectively, from biofilms of S. mutans UA159 wild strain that were cultured with bisHPPP.

RESULTS

The levels of bisHPPP released from composite were similar for ΔSMU_118c and media control, and these were significantly lower compared to the parent wild-strain UA159 and complemented strain (ΔSMU_118cC) (p < 0.05). Gene expression of SMU_118c and productions of SMU_118c protein were higher for bisHPPP incubated biofilms (p < 0.05).

SIGNIFICANCE

This study suggests that SMU_118c is a dominant esterase in S. mutans and capable of catalyzing the hydrolysis of the resinous matrix of polymerized composites and adhesives. In turn, the bacterial response to BBP was to increase the expression of the esterase gene and enhance esterase production, potentially accelerating the biodegradation of the restoration, adhesive and restoration-tooth interface, ultimately contributing to premature restoration failure.

STATEMENT OF SIGNIFICANCE

We recently reported (Huang et al., 2018) on the isolation and initial characterization of a specific esterase (SMU_118c) from S. mutans that show degradative activity toward the hydrolysis of dental monomers. The current study further characterize this enzyme and shows that SMU_118c is a dominant degradative esterase activity in the cariogenic bacterium S. mutans and is capable of catalyzing the hydrolysis of the resinous matrix of polymerized composites and adhesives. In turn, the bacterial response to biodegradation by-products from composites and adhesives was to increase the expression of the esterase gene and enhance esterase production, accelerating the biodegradation of the restoration, adhesive and the restoration-tooth interface, potentially contributing to the pathogenesis of recurrent caries around resin composite restorations.

Antimicrobial photodynamic therapy of Lactobacillus acidophilus by indocyanine green and 810-nm diode laser

This study investigated the efficacy of photodynamic therapy (PDT) using EmunDo as a photosensitizer against Lactobacillus acidophilus. A gallium aluminum arsenide diode laser was used in this experiment (810 nm, CW). Standard suspensions of Lactobacillus acidophilus were divided into six groups by treatment: 1) EmunDo, 2) diode laser (100 mW, 90 s), 3) diode laser (300 mW, 30 s); 4) EmunDo + diode laser (100 mW, 90 s), 5) EmunDo + diode laser (300 mW, 30 s), 6) control (no treatment). Bacterial suspensions from each group were subcultured onto the surface of MRS agar plates immediately and 24 h after treatment, and the viable microorganisms of Lactobacillus acidophilus were counted. The data were analyzed by ANOVA and student's t-test at p < 0.05. There was a significant between-group difference in the number of Lactobacillus acidophilus colonies in cell cultures obtained at 24 h after treatment (p < 0.001). The viable counts were significantly lower in EmunDo and both PDT groups, as compared to the other groups (p < 0.05). In the control and laser-irradiated groups, the number of colonies increased significantly at 24 h compared to the immediately after treatment (p < 0.05), whereas in both PDT groups, the number of colonies showed a significant reduction after 24 h of therapy (p < 0.05). Under the conditions used in this study, L. acidophilus colonies were susceptible to PDT after sensitization with EmunDo and exposure to diode laser. These findings imply that PDT is capable to reduce cariogenic bacteria, potentially leading to more conservative cavity preparation.

Evaluation of Antimicrobial Properties of Conventional Poly(Methyl Methacrylate) Denture Base Resin Materials Containing Hydrothermally Synthesised Anatase TiO2 Nanotubes against Cariogenic Bacteria and Candida albicans

The purpose of this study was to investigate the antimicrobial properties of a conventional poly methyl methacrylate (PMMA) modified with hydrothermally synthesised titanium dioxide nanotubes (TNTs). Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentrations (MFC) for planktonic cells of the TiO₂ nanotubes solution against Lactobacillus acidophilus, Streptococcus mutans and Candida albicans were determined. The powder of conventional acrylic resin was modified using 2.5% and 5% by weight synthesised titanium dioxide (TiO₂) nanotubes, and rectangular-shaped specimens (10 mm × 10 mm × 3 mm) were fabricated. The antimicrobial properties of ultraviolet (UV) and non-UV irradiated modified, and non-modified acrylic resins were evaluated using the estimation of planktonic cell count and biofilm formation of the three microorganisms mentioned above. The data were analysed by one-way analysis of variance (ANOVA), followed by a post-hoc Tukey's test at a significance level of 5%. MIC, for Streptococcus. mutans, Lactobacillus. acidophilus, and Candida. albicans, MBC for S. mutans and L. acidophilus and MFC for Candida. albicans were obtained more than 2100 µg/mL. The results of this study indicated a significant reduction in both planktonic cell count and biofilm formation of modified UV-activated acrylic specimens compared with the control group (p = 0.00). According to the results of the current study, it can be concluded that PMMA/TiO₂ nanotube composite can be considered as a promising new material for antimicrobial approaches.

In Vitro Anti-Cariogenic Plaque Effects of Essential Oils Extracted from Culinary Herbs

Introduction

Cariogenic bacteria including mutans streptococci and lactobacilli are partly but significantly involved in dental caries development. An effective prevention strategy against dental caries is to decrease the accumulation of this microbiota either in planktonic or in biofilm form.

Aim

To examine the antimicrobial and anti-plaque effects of some culinary herbs (spices), so the herbs are plausibly used as alternative and effective herbal plaque control supplements to promote good oral health.

Materials and Methods

Essential oils extracted from sweet basil (Ocimum basilicum), cinnamon bark (Cinnamomum zeylanicum), sweet fennel (Foeniculum vulgare), kaffir lime (Citrus hystrix), black pepper (Piper nigrum), peppermint (Mentha piperita), and spearmint (Mentha spicata) were primarily examined for their antimicrobial activities against the cariogenic bacteria (Streptococcus mutans KPSK2 and Lactobacillus casei) using the agar disk diffusion and broth microdilution methods, respectively. These essential oils were then analysed for anti-plaque effects (retardation of S. mutans biofilm formation and reduction of the in vitro established biofilm). This experimental study was performed at the Department of Oral Microbiology, Faculty of Dentistry, Mahidol University during June 2015 till August 2016.

Results

All selected essential oils showed different degrees of antimicrobial activity against the planktonic form of both cariogenic bacteria. Cinnamon bark essential oil expressed the strongest inhibitory effect against S. mutans {MIC of 0.08% (v/v)} and L. casei {MIC of 0.16% (v/v)}, whereas the weakest effect was found in kaffir lime essential oil {MIC values of 2.5% and 5.0% (v/v) for S. mutans and L. casei, respectively}. Up to 80% of S. mutans biofilm was retarded to form on the substratum primed with these spice essential oils, especially cinnamon oil. The preventive effect of these oils was in dose- and exposure time-dependent manners. For reductive effect against the 24-hour pre-established S. mutans biofilm, at least 50% of the biofilm mass was reduced when the biofilm was treated with each essential oil at the MIC for an hour. The reductive effect against the in vitro established S. mutans biofilm of these culinary herb essential oils only depended on the exposure time.

Conclusion

Cinnamon and sweet basil essential oils with impressive in vitro anti-cariogenic bacteria and anti-plaque effects may be proposed as alternative and effective supplements to promote oral health status.

Chemical Composition, Antibacterial, Schistosomicidal, and Cytotoxic Activities of the Essential Oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae)

We have investigated the chemical composition and the antibacterial activity of the essential oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae) (DA-EO) against a representative panel of cariogenic bacteria. We have also assessed the in vitro schistosomicidal effects of DA-EO on Schistosoma mansoni and its cytotoxicity to GM07492-A cells in vitro. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) revealed that the monoterpenes cis-piperitone oxide (35.2%), p-cymene (14.5%), isoascaridole (14.1%), and α-terpinene (11.6%) were identified by as the major constituents of DA-EO. DA-EO displayed weak activity against Streptococcus sobrinus and Enterococcus faecalis (minimum inhibitory concentration (MIC) = 1000 μg/ml). On the other hand, DA-EO at 25 and 12.5 μg/ml presented remarkable schistosomicidal action in vitro and killed 100% of adult worm pairs within 24 and 72 h, respectively. The LC₅₀ values of DA-EO were 6.50 ± 0.38, 3.66 ± 1.06, and 3.65 ± 0.76 μg/ml at 24, 48, and 72 h, respectively. However, DA-EO at concentrations higher than 312.5 μg/ml significantly reduced the viability of GM07492-A cells (IC₅₀  = 207.1 ± 4.4 μg/ml). The selectivity index showed that DA-EO was 31.8 times more toxic to the adult S. mansoni worms than GM07492-A cells. Taken together, these results demonstrate the promising schistosomicidal potential of the essential oil of Dysphania ambrosioides.

Multicenter study on caries risk assessment in Japanese adult patients

OBJECTIVES

This study was conducted to identify significant risk factors for the onset and the accumulation of new caries in adult patients undergoing regular preventive therapy.

METHODS

The data of 732 patients from nine Japanese general dental practices were retrospectively analyzed. Classification and regression tree (CART) analysis was applied to develop a caries prediction model using the following patient parameters: age, number of teeth with caries experience (DMFT), levels of mutans streptococci (SM) and lactobacilli (LB), saliva flow rate and buffer capacity, and compliance with a preventive program. Poisson regression analysis was conducted to identify factors affecting caries accumulation within three years.

RESULTS

CART analysis identified patients at high risk for primary caries with an odds ratio of 3.08 (95%CI, 1.55-5.79; p=0.0018) according to SM levels and compliance; and those for secondary caries with an odds ratio of 3.69 (95%CI, 2.29-5.91; p<0.0001) according to LB and SM levels. Poisson regression analyses showed that accumulation of primary caries was affected by compliance (p<0.001), SM (p<0.001) and LB (p=0.013). Accumulation of secondary caries was affected by DMFT (p<0.001), SM (p<0.001) and LB (p<0.001).

CONCLUSIONS

CART is an important tool in identifying the risk of caries development in individual adult patients. Cariogenic bacteria are important factors for both the onset and accumulation of primary and secondary caries.

CLINICAL SIGNIFICANCE

Participation in a regular preventive program limits the onset and the accumulation of primary caries in adult patients.

Penetration of Streptococcus sobrinus and Streptococcus sanguinis into dental enamel

The aim of this pilot study was to assess the difference in virulence of acidogenic and aciduric oral streptococci in an in vitro caries model using their penetration depths into dental enamel. 30 caries-free extracted molars from 11- to 16-year-olds were cleaned ultrasonically for 1 min with de-ionized water and, after air-drying, embedded in epoxy resin. After 8-h of setting at room temperature, the specimens were ground on the buccal side with SiC-paper 1200 (particle size 13-16 μm). Enamel was removed in circular areas sized 3 mm in diameter; the mean depth of removed enamel was 230 ± 60 μm. 15 specimens each were incubated anaerobically under standardized conditions with 24 h-cultures of Streptococcus sanguinis 9S or Streptococcus sobrinus OMZ 176 in Balmelli broth at 37 ± 2 °C; the pH-values of the broths were measured at the beginning and end of each incubation cycle. After 2, 4, 6, 8, and 10 weeks 3 teeth each were fixed in 2.5% glutaraldehyde in cacodylate buffer for 24 h, washed 3× and dehydrated 30-60min by sequential washes through a series of 30-100% graded ethanol. The teeth were cut in half longitudinally; afterward, two slits were made to obtain fracture surfaces in the infected area. After critical-point-drying the fragments were gold-sputtered and viewed in a scanning electron microscope at magnifications of ×20-20,000. After 10 weeks of incubation, penetration of S. sanguinis of 11.13 ± 24.04 μm below the break edges into the enamel was observed. The invasion of S. sobrinus reached depths of 87.53 ± 76.34 μm. The difference was statistically significant (paired t test: p = 0.033). The experimental penetration depths emphasize the importance of S. sanguinis versus S. sobrinus in the context of the extended ecological plaque hypothesis.

Inhibitory effects of a cured antibacterial bonding system on viability and metabolic activity of oral bacteria

OBJECTIVES

To evaluate the antimicrobial efficacy of Clearfil SE Protect (CP) and Clearfil SE Bond (CB) after curing and rinsed against five individual oral microorganisms as well as a mixture of bacterial culture prepared from the selected test organisms.

METHODS

Bacterial suspensions were prepared from single species of Streptococcus mutans, Streptococcus sobrinus, Streptococcus gordonii, Actinomyces viscosus and Lactobacillus lactis, as well as mixed bacterial suspensions from these organisms. Dentin bonding system discs (6 mm×2 mm) were prepared, cured, washed and placed on the bacterial suspension of single species or multispecies bacteria for 15, 30 and 60 min. MTT, Live/Dead bacterial viability (antibacterial effect), and XTT (metabolic activity) assays were used to test the two dentin system's antibacterial effect. All assays were done in triplicates and each experiment repeated at least three times. Data were submitted to ANOVA and Scheffe's f-test (5%).

RESULTS

Greater than 40% bacteria killing was seen within 15 min, and the killing progressed with increasing time of incubation with CP discs. However, a longer (60 min) period of incubation was required by CP to achieve similar antimicrobial effect against mixed bacterial suspension. CB had no significant effect on the viability or metabolic activity of the test microorganisms when compared to the control bacterial culture. CP was significantly effective in reducing the viability and metabolic activity of the test organisms.

SIGNIFICANCE

The results demonstrated the antimicrobial efficacy of CP both on single and multispecies bacterial culture. CP may be beneficial in reducing bacterial infections in cavity preparations in clinical dentistry.

Potentials of mouthwashes in disinfecting cariogenic bacteria and biofilms leading to inhibition of caries

OBJECTIVES

The aim of this study was to compare the effects of certain commercially available mouthwashes on cariogenic bacteria and biofilms, following the acquisition of inhibition potentials of caries.

MATERIALS AND METHODS

Mouthwashes containing I) chlorhexidine gluconate (CHG; 0.0005% w/v), II) benzethonium chloride (BTC; 0.01% w/v), III) an essential oil (Listerine), and IV) povidone-iodine (PVP-I; 0.035% w/v) were tested on planktonic cariogenic bacteria, biofilms, and an ex vivo caries model. Bacterial aliquots were inoculated with each solution separately and vortexed for 10 seconds at room temperature. Bacterial viability was subsequently investigated by fluorescence microscopy (FM) after staining with a BacLight viability kit and the number of colony-forming units (CFUs) was counted. Similarly, mouthwash solutions were applied to artificial cariogenic biofilms, and bacterial viability of the biofilms was investigated as stated above. Inhibition potentials of two selected mouthwashes of carious lesions were investigated using biofilm-induced caries and a secondary caries model. In all steps, a phosphate-buffered saline (PBS) solution was included as a control.

RESULTS

Planktonic cariogenic bacteria and bacteria embedded in biofilms were killed in remarkably large numbers with Listerine and PVP-I treatment compared to PBS and other gargles. CFU counts also showed significant reduction after treatment with Listerine and PVP-I compared to other solutions (P<0.05). Listerine also displayed significant (P<0.05) inhibition effects in preventing the progression of demineralization.

CONCLUSION

Bactericidal potencies of the mouthwashes varied significantly, suggesting that mouthwashes like Listerine can be useful for the prevention of caries and secondary caries.

Antibacterial and phytochemical studies on Calotropis gigantia (L.) R. Br. latex against selected cariogenic bacteria

In vitro antibacterial potential of the chloroform, ethyl acetate, hexane, methanol and aqueous extracts of Calotropis gigantia (L.) R. Br. was evaluated by using five cariogenic bacteria, Actinomyces viscosus, Lactobacillus acidophilus, Lactobacillus casei, Streptococcus mitis and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The chloroform extracted fraction of latex showed inhibitory effect against S. mutans and L. acidophilus with MIC value of 0.032 and 0.52 mg/mL, respectively. Qualitative investigation on structure elucidation of bioactive compound using IR, NMR and GC-MS techniques revealed the presence of methyl nonanoate, a saturated fatty acid.