Effect of two antimicrobial agents on early in situ biofilm formation

Impact of pH-adjusted fluoride and stannous solutions on the protective properties on the pellicle layer in vitro and in situ

This study evaluates the ideal pH for anti-erosion and anti-adherent efficacy of fluoride and stannous solutions (sodium fluoride (SF), amine fluoride (AF), sodium monofluorophosphate (SMFP), stannous fluoride (SnF2) with 500 ppm fluoride concentration each and stannous chloride (SnCl2, 1563 ppm stannous)). In vitro, solutions were tested at pH 4.5 and 5.5. The main in situ experiments were carried out at the pH of 4.5: For pellicle formation 6 volunteers wore bovine enamel slabs intraorally for 1 min, rinsed with 8 ml solution for 1 min and continued for up to 30 min/8 h. Physiological pellicle samples served as controls. After incubation in HCl (2.0, 2.3) for 2 min mineral release was determined photometrically. Bacterial counts on 8 h biofilms were determined by fluorescence microscopy (BacLight™ and DAPI with Concanavalin A). Modification of the pellicle ultrastructure was examined by TEM. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney-U tests with Bonferroni-correction (p < 0.05). SnF2 showed a significant erosion protection. AF, SnF2, and SnCl2 were most anti-adherent. SnF2 and SnCl2 caused a pronounced basal pellicle with stannous precipitates. Compared to other fluoride monosubstances, stannous ions offer greater protection against erosive acidic attacks. Stannous ions act as crucial co-factor in this process.

Screening Antibacterial Constituents of Scutellaria Radix Based on Spectrum-Effect Relationships Between HPLC Fingerprints and the Inhibition of Oral Bacteria

Scutellaria Radix (SR) is a widely used traditional Chinese medicine in clinics for the therapy of upper respiratory tract infectious diseases. Modern pharmacological investigations indicate that SR exerts a significant bacteriostatic effect on different oral bacteria, but few studies have systematically investigated the main active constituents of SR causing this activity. Spectrum-effect correlation analysis was applied to screening anti-oral-microbial constituents from SR. The aqueous extract of SR was divided into fractions of different polarity and the active fraction was screened using the agar diffusion method. Eighteen batches of SR were further prepared and the chromatography fingerprint was established using high-performance liquid chromatography. The antibacterial activities of these constituents were examined against different oral bacteria. Finally, the spectrum-effect relationship between the fingerprint and those antibacterial effects was analyzed by gray correlation analysis and partial least squares regression. Five active constituents were screened out and their antibacterial activity was systematically confirmed by a knockout/in strategy combined with a biofilm extraction method, which indicated that these five compounds were responsible for the antibacterial activity of SR. These results form the basis for further development and improved quality control of SR in the treatment of oral diseases.

A New Device for In Situ Dental Biofilm Collection Additively Manufactured by Direct Metal Laser Sintering and Vat Photopolymerization

Dental biofilms are complex medical biofilms that cause caries, the most prevalent disease of humankind. They are typically collected using handcrafted intraoral devices with mounted carriers for biofilm growth. As the geometry of handcrafted devices is not standardized, the shear forces acting on the biofilms and the access to salivary nutrients differ between carriers. The resulting variability in biofilm growth renders the comparison of different treatment modalities difficult. The aim of the present work was to design and validate an additively manufactured intraoral device with a dental bar produced by direct metal laser sintering and vat photopolymerized inserts with standardized geometry for the mounting of biofilm carriers. Additive manufacturing reduced the production time and cost, guaranteed an accurate fit of the devices and facilitated the handling of carriers without disturbing the biofilm. Biofilm growth was robust, with increasing thickness over time and moderate inter- and intraindividual variation (coefficients of variance 0.48-0.87). The biofilms showed the typical architecture and composition of dental biofilms, as evidenced by confocal microscopy and 16S rRNA gene sequencing. Deeper inserts offering increased protection from shear tended to increase the biofilm thickness, whereas prolonged exposure to sucrose during growth increased the biofilm volume but not the thickness. Ratiometric pH imaging revealed considerable pH variation between participants and also inside single biofilms. Intraoral devices for biofilm collection constitute a new application for medical additive manufacturing and offer the best possible basis for studying the influence of different treatment modalities on biofilm growth, composition, and virulence. The Clinical Trial Registration number is: 1-10-72-193-20.

Liquid crystal precursor system as a vehicle for curcumin-mediated photodynamic inactivation of oral biofilms

Curcumin has great potential as a photosensitizer, but it has low solubility in aqueous solutions. This study reports the antimicrobial efficacy of photodynamic inactivation (PDI) mediated by a curcumin-loaded liquid crystal precursor (LCP) on in situ dental biofilms. Thirty volunteers used intraoral devices containing enamel samples for 48 hours for biofilm formation. The samples were then removed from the device and treated either with LCP with 160 μM of curcumin plus illumination at 18 J/cm² (C + L+ group) or with LCP without curcumin in the dark (C - L - group). Following this, the biofilm from the samples was plated for quantifying the viable colonies at 37°C for 48 hours. Specific and nonspecific media were used for the presumptive isolation of Streptococcus mutans, Lactobacillus species/aciduric microorganisms, Candida species, and total microbiota. The C + L+ group showed a highly significant (P < .001) reduction in the log₁₀ (colony forming units/mL) values as compared to the C - L - group for all culture media. Hierarchical linear regression indicated that there may be predictors at individual volunteer level explaining the difference in the PDI efficacy among different individuals (P = .001). The LCP system retained curcumin and released it slowly and continuously, thus protecting the drug from photodegradation. LCP with curcumin is considered effective for the photoinactivation of dental biofilms, but the PDI efficacy may differ based on the host's individual characteristics.

In vitro versus in situ biofilms for evaluating the antimicrobial effectiveness of herbal mouthrinses

For centuries, diverse mouthrinses have been applied for medicinal purposes in the oral cavity. In view of the growing resistance of oral microorganisms against conventional antimicrobial agents e.g. chlorhexidine, the implementation of alternative treatments inspired by nature has lately gained increasing interest. The aim of the present study was to compare in vitro biofilm models with in situ biofilms in order to evaluate the antimicrobial potential of different natural mouthrinses. For the in vitro study a six-species supragingival biofilm model containing A. oris, V. dispar, C. albicans, F. nucleatum, S. mutans and S. oralis was used. Biofilms were grown anaerobically on hydroxyapatite discs and treated with natural mouthrinses Ratanhia, Trybol and Tebodont. 0.9% NaCl and 10% ethanol served as negative controls, while 0.2% CHX served as positive control. After 64h hours, biofilms were harvested and quantified by cultural analysis CFU. For the in situ study, individual test splints were manufactured for the participants. After 2h and 72h the biofilm-covered samples were removed and treated with the mouthrinses and controls mentioned above. The biofilms were quantified by CFU and stained for vitality under the confocal laser scanning microscope. In the in vitro study, 0.2% CHX yielded the highest antimicrobial effect. Among all mouthrinses, Tebodont (4.708 ± 1.294 log10 CFU, median 5.279, p<0.0001) compared with 0.9% NaCl showed the highest antimicrobial potential. After 72h there was no significant reduction in CFU after 0.2% CHX treatment. Only Trybol showed a statistically significant reduction of aerobic growth of microorganisms in situ (5.331 ± 0.7350 log10 CFU, median 5.579, p<0.0209). After treatment with the positive control 0.2% CHX, a significant percentage of non-vital bacteria (42.006 ± 12.173 log10 CFU, median 42.150) was detected. To sum up, a less pronounced effect of all mouthrinses was shown for the in situ biofilms compared to the in vitro biofilms.

Transcriptomic Stress Response in Streptococcus mutans following Treatment with a Sublethal Concentration of Chlorhexidine Digluconate

Despite the widespread use of antiseptics such as chlorhexidine digluconate (CHX) in dental practice and oral care, the risks of potential resistance toward these antimicrobial compounds in oral bacteria have only been highlighted very recently. Since the molecular mechanisms behind antiseptic resistance or adaptation are not entirely clear and the bacterial stress response has not been investigated systematically so far, the aim of the present study was to investigate the transcriptomic stress response in Streptococcus mutans after treatment with CHX using RNA sequencing (RNA-seq). Planktonic cultures of stationary-phase S. mutans were treated with a sublethal dose of CHX (125 µg/mL) for 5 min. After treatment, RNA was extracted, and RNA-seq was performed on an Illumina NextSeq 500. Differentially expressed genes were analyzed and validated by qRT-PCR. Analysis of differential gene expression following pathway analysis revealed a considerable number of genes and pathways significantly up- or downregulated in S. mutans after sublethal treatment with CHX. In summary, the expression of 404 genes was upregulated, and that of 271 genes was downregulated after sublethal CHX treatment. Analysis of differentially expressed genes and significantly regulated pathways showed regulation of genes involved in purine nucleotide synthesis, biofilm formation, transport systems and stress responses. In conclusion, the results show a transcriptomic stress response in S. mutans upon exposure to CHX and offer insight into potential mechanisms that may result in development of resistances.

Efficacy of Experimental Mouth Rinses on Caries-Related Biofilms in vitro

This study assessed the efficacy of tin and Polyethylenglycol (PEG-3) tallow aminopropylamine in different concentrations on Streptococcus mutans (S. mutans) biofilms to establish a new screening process for different antimicrobial agents and to gain more information on the antibacterial effects of these agents on cariogenic biofilms. Isothermal microcalorimetry (IMC) was used to determine differences in two growth parameters: lag time and growth rate; additionally, reduction in active biofilms was calculated. Experimental mouth rinses with 400 and 800 ppm tin derived from stannous fluoride (SnF₂) revealed results (43.4 and 49.9% active biofilm reduction, respectively) similar to meridol mouth rinse (400 ppm tin combined with 1,567 ppm PEG-3 tallow aminopropylamine; 55.3% active biofilm reduction) (p > 0.05), while no growth of S. mutans biofilms was detected during 72 h for samples treated with an experimental rinse containing 1,600 ppm tin (100% active biofilm reduction). Only the highest concentration (12,536 ppm) of rinses containing PEG-3 tallow aminopropylamine derived from amine fluoride (AmF) revealed comparable results to meridol (57.5% reduction in active biofilm). Lower concentrations of PEG-3 tallow aminopropylamine showed reductions of 16.9% for 3,134 ppm and 33.5% for 6,268 ppm. Maximum growth rate was significantly lower for all the samples containing SnF₂ than for the samples containing control biofilms (p < 0.05); no differences were found between the control and all the PEG-3 tallow aminopropylamine (p > 0.05). The growth parameters showed high reproducibility rates within the treated groups of biofilms and for the controls; thus, the screening method provided reliable results.

Establishment of novel in vitro culture system with the ability to reproduce oral biofilm formation on dental materials

Intensive research has been conducted with the aim of developing dental restorative/prosthetic materials with antibacterial and anti-biofilm effects that contribute to controlling bacterial infection in the oral cavity. In situ evaluations were performed to assess the clinical efficacy of these materials by exposing them to oral environments. However, it is difficult to recruit many participants to collect sufficient amount of data for scientific analysis. This study aimed to assemble an original flow-cell type bioreactor equipped with two flow routes and assess its usefulness by evaluating the ability to reproduce in situ oral biofilms formed on restorative materials. A drop of bacterial suspension collected from human saliva and 0.2% sucrose solution was introduced into the assembled bioreactor while maintaining the incubation conditions. The bioreactor was able to mimic the number of bacterial cells, live/dead bacterial volume, and volume fraction of live bacteria in the in situ oral biofilm formed on the surface of restorative materials. The usefulness of the established culture system was further validated by a clear demonstration of the anti-biofilm effects of a glass-ionomer cement incorporating zinc-releasing glasses when evaluated by this system.

Remineralizing efficacy of fluoride in the presence of oral microcosm biofilms

OBJECTIVES

The oral biofilm structure or composition can affect the penetration of remineralizing agents. Therefore, this study evaluated the remineralizing efficacy of fluoride using a pH-cycling model with oral microcosm biofilms.

METHODS

Artificial carious lesions were formed in 80 bovine incisors. The pH-cycling conditions with or without oral microcosm biofilms were applied to 40 specimens each. The pH-cycling scheme was repeated for 12 days. Fluorescence loss (ΔF,%) of early carious lesions was measured for all specimens using a quantitative light-induced fluorescence-digital camera, before and after fluoride application. Biofilms on specimens were further analyzed for red fluorescence intensity (red/green ratios) and colony-forming unit counts. The effects of pH-cycling conditions and treatments on changes in ΔF (ΔΔF) and the effects of interactions between factors were analyzed using two-way analysis of variance.

RESULTS

The fluoride-treated group with oral biofilms had an approximately 0.89-fold lower ΔΔF than the fluoride-treated group without oral biofilms (p < 0.0001). When oral biofilms were absent, the fluoride-treated group showed a 1.31-fold greater ΔΔF compared to that in the distilled water-treated group (p < 0.0001). When oral biofilms were present, the fluoride-treated group showed a 1.14-fold greater ΔΔF compared to that in the distilled water-treated group; however, this difference was not statistically significant.

CONCLUSIONS

There was a significant difference in fluoride remineralizing efficacy based on the presence of biofilms on early carious lesions. Therefore, fluoride remineralization assessment in the absence of oral biofilms could lead to an overestimation of efficacy.

CLINICAL SIGNIFICANCE

Fluoride application might not have a robust remineralization effect on early carious lesions in the presence of a mature biofilm on the tooth surface.

Long-Term Use of Oral Hygiene Products Containing Stannous and Fluoride Ions: Effect on Viable Salivary Bacteria

The aim of this randomized, controlled clinical trial was to isolate and identify viable microorganisms in the saliva of study participants that continuously used a stannous and fluoride ion (F/Sn)-containing toothpaste and mouth rinse over a period of three years in comparison to a control group that used stannous ion free preparations (noF/Sn) over the same time period. Each group (F/Sn and noF/Sn) included 16 participants that used the respective oral hygiene products over a 36-month period. Stimulated saliva samples were collected at baseline (T0) and after 36 months (T1) from all participants for microbiological examination. The microbial composition of the samples was analyzed using culture technique, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, and 16S rDNA Polymerase Chain Reaction (PCR). There were only minor differences between both groups when comparing the absolute values of viable microbiota and bacterial composition. The treatment with F/Sn led to a slight decrease in disease-associated and a slight increase in health-associated bacteria. It was shown that the use of stannous ions had no negative effects on physiological oral microbiota even after prolonged use. In fact, a stabilizing effect of the oral hygiene products containing stannous ions on the health-associated oral microbiota could be expected.

Alcohol and light-polymerizing glaze effect on the physical and mechanical properties of a bisacrylate composite resin before and after immersion in chlorhexidine gluconate

STATEMENT OF PROBLEM

The use of 0.12% chlorhexidine gluconate (CHX) may damage bisacrylate composite resin interim restorations, but whether they can be protected with an application of alcohol and/or the use of a glaze is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of applying a 70% alcohol solution on the physical and mechanical properties of a bisacrylate composite resin, with and without the application of a light-polymerizing glaze subjected to 0.12% CHX twice a day for 7 days.

MATERIAL AND METHODS

Forty specimens of an autopolymerized bisacrylate composite resin were divided into 4 groups (n=10): Group C (without alcohol, without glaze), Group G (without alcohol, with glaze), Group A (with alcohol, without glaze), and Group AG (with alcohol, with glaze). All specimens were submitted to in vitro treatment with 0.12% CHX for 7 days, and tests of color alteration (ΔE₀₀), microhardness, roughness, and surface were performed initially and after treatment. Data were submitted to analysis of variance (ANOVA) and the Tukey HSD test (α=.05).

RESULTS

Group A had the lowest mean value of ΔE₀₀ with a significant statistical difference from Group C. The groups with alcohol presented higher microhardness mean values compared with groups without alcohol in both periods of analysis, except for the groups with glaze in the final period. Group C showed higher mean roughness values in comparison with Group A in both periods. Group AG presented higher mean roughness values than Group G. Surface energy values did not vary significantly among groups, except between Groups C and A in the final period.

CONCLUSIONS

The application of alcohol optimized the properties of the autopolymerized bisacrylate composite resin analyzed, with and without the application of glaze. Overall, the use of CHX changed the microhardness and roughness when the glaze was applied.

The antibacterial efficacy of silver diamine fluoride (SDF) is not modulated by potassium iodide (KI) supplements: A study on in-situ plaque biofilms using viability real-time PCR with propidium monoazide

Silver diamine fluoride (SDF) is commonly used to arrest caries lesions, especially in early childhood caries. Recently, it was suggested that SDF can be combined with potassium iodide (KI) to minimize the discoloration of demineralized dentine associated with SDF application. However, the antibacterial efficacy of SDF alone or combined with KI on in-situ biofilm is unknown. Hence, we compared the anti-plaque biofilm efficacy of two different commercially available SDF solutions, with or without KI, using an in-situ biofilm, analysed using viability real-time PCR with propidium monoazide (PMA). Appliance-borne in-situ biofilm samples (n = 90) were grown for a period of 6 h in five healthy subjects who repeated the experiment on three separate occasions, using a validated, novel, intraoral device. The relative anti-biofilm efficacy of two SDF formulations; 38.0% Topamine (SDFT) and 31.3%, Riva Star (SDFR), KI alone, and KI in combination with SDFR (SDFR+KI) was compared. The experiments were performed by applying an optimized volume of the agents onto the biofilm for 1min, mimicking the standard clinical procedure. Afterwards the viability of the residual biofilm bacteria was quantified using viability real-time PCR with PMA, then the percentage of viable from total bacteria was calculated. Both SDF formulations (SDFT and SDFR) exhibited potent antibacterial activities against the in-situ biofilm; however, there was non-significant difference in their efficacy. KI alone did not demonstrate any antibacterial effect, and there was non-significant difference in the antibacterial efficacy of SDF alone compared to SDF with KI, (SDFT v SDFR/KI). Thus, we conclude that the antibacterial efficacy of SDF against plaque biofilms is not modulated by KI supplements. Viability real-time PCR with PMA was successfully used to analyze the viability of naturally grown oral biofilm; thus, the same method can be used to test the antimicrobial effect of other agents on oral biofilms in future research.

Influence of the long-term use of oral hygiene products containing stannous ions on the salivary microbiome - a randomized controlled trial

Oral hygiene products containing tin are suitable to prevent erosive tooth wear, yet effects on the oral microbiota are not known yet. Therefore, this study determined the salivary microbiome of 16 participants using products with stannous ions for three years (TG) compared with a control group (CG) to assess their influence on the microbiota. Participants were included in a randomized controlled clinical trial (RCT) with biannual visits. Illumina Miseq sequencing revealed as most abundant genera: Streptococcus (TG 14.3%; CG 13.0%), Veillonella (TG 11.3%; CG 10.9%), Prevotella (TG 7.0%; CG 9.8%), Haemophilus (TG 6.6%; CG 7.2%), Porphyromonas (TG 5.9%, CG 5.1%), Leptotrichia (TG 5.8%; CG 4.9%), Actinomyces (TG 4.0%; CG 4.6%) and Neisseria (TG 5.4%; CG 4.2%). Beta-Diversity was not significantly different between groups at both time points, although significant differences between groups were found for certain taxa after three years. The genus Prevotella was found in higher abundance in CG whereas Neisseria and Granulicatella, health-associated taxa, were found more abundantly in TG. Salivary microbiota after three years reflected a composition associated with oral health, hence continual use as a preventive measure for dental erosion can be considered safe and benefitting oral health for patients with a high risk of erosion.

Chlorhexidine rinsing inhibits biofilm formation and causes biofilm disruption on dental enamel in situ

OBJECTIVES

This in situ study aims to evaluate the effects of chlorhexidine (CHX) mouth rinsing on biofilm formation and moreover on the disruption of existing mature dental biofilms.

METHODS

Biofilms were formed in situ by five volunteers on bovine enamel specimens fixed to individual acrylic splints. For biofilm formation analysis, the volunteers intraorally exposed the splint for 48 h. Mouth rinsing using 10 ml of 0.2% CHX or water as control was performed for 30 s every 12 h. For analysis of biofilm disruption, the biofilm was formed on enamel specimens for 48 h. Then, the first CHX rinse was carried out. A second rinse followed after an additional 12 h, again for 30 s using 10 ml of 0.2% CHX. Biofilm vitality was imaged by fluorescence microscopy after vital fluorescence staining. Additionally, the ultrastructure of the biofilm was examined by transmission electron microscopy.

RESULTS

Rinses with 0.2% CHX significantly reduced biofilm formation on enamel. Both biofilm colonization and vitality were dramatically impaired. Moreover, a considerable biofilm disruption induced by the CHX rinses was observed. Remarkably, a single application of CHX to a 48-h mature biofilm causes biofilm ultrastructure alterations and induces a substantial reduction in biofilm thickness and bacterial vitality.

CONCLUSIONS

CHX mouth rinses induced a significant inhibition of biofilm formation on native enamel. Furthermore, an important biofilm disrupting effect under in situ conditions was detected.

CLINICAL RELEVANCE

CHX rinses could be used as a short-term treatment protocol for biofilm management focused on patients unable to reach adequate oral hygiene.

Intraoral appliances for in situ oral biofilm growth: a systematic review

Background: Oral biofilms are the root cause of major oral diseases. As in vitro biofilms are not representative of the intraoral milieu, various devices have been manufactured over the years to develop Appliance Grown Oral Biofilm (AGOB). Objective: To review various intraoral appliances used to develop AGOB for microbiological analysis, and to judge the optimal means for such analyses. Design: Four databases (PubMed, Science Direct, Scopus and Medline) were searched by two independent reviewers, and articles featuring the key words 'device' OR 'splint' OR 'appliance'; 'Oral biofilm' OR 'dental plaque'; 'in vivo' OR 'in situ'; 'Microbiology' OR 'Bacteria' OR 'microbiome'; were included. The standard Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) were adopted for data gathering. Results: Of the 517 articles which met the initial inclusion criteria, 24 were deemed eligible for review. The age of the AGOB, sampled at various intervals, ranged from 30 min to 28 days. The most commonly used microbiome analytical methods were fluorescence microscopy, total cell count using conventional, and molecular tools including Next Generation Sequencing (NGS) platforms. Conclusions: No uniformly superior method for collecting AGOB could be discerned. NGS platforms are preferable for AGOB analyses.

No differences in microbiome changes between anti-adhesive and antibacterial ingredients in toothpastes during periodontal therapy

Aim

This subgroup analysis of a 12‐week randomized, double‐blind, and two‐center trial aimed to evaluate whether two different toothpaste formulations can differentially modulate the dental microbiome.

Material and Methods

Forty one mild to moderate periodontitis patients used as an adjunct to periodontal treatment either a toothpaste with anti‐adhesive zinc‐substituted carbonated hydroxyapatite (HA) or with antimicrobial and anti‐adhesive amine fluoride/stannous fluoride (AmF/SnF₂) during a 12‐week period. Plaque samples from buccal/lingual, interproximal, and subgingival sites were taken at baseline, 4 weeks after oral hygiene phase, and 8 weeks after periodontal therapy. Samples were analyzed with paired‐end Illumina Miseq 16S rDNA sequencing. The differences and changes on community level (alpha and beta diversity) and on the level of single agglomerated ribosomal sequence variants (aRSV) were calculated with analysis of covariance (ANCOVA) and likelihood ratio test (LRT).

Results

Interproximal and subgingival sites harbored predominately Fusobacterium and Prevotella species associated with periodontitis, whereas buccal/lingual sites harbored mainly Streptococcus and Veillonella species associated with periodontal health. Alpha and beta diversity did not change noticeably differently between both toothpaste groups (P > 0.05, ANCOVA). Furthermore, none of the aRSVs showed a noticeably different change between the tested toothpastes during periodontal therapy (P_adj .> 0.05, LRT).

Conclusion

The use of a toothpaste containing anti‐adhesive HA did not induce statistically noticeably different changes on microbial composition compared to an antimicrobial and anti‐adhesive AmF/SnF₂ formulation.

Biofilm formation by the oral pioneer colonizer Streptococcus gordonii: an experimental and numerical study

For decades, extensive research efforts have been conducted to improve the functionality and stability of implants. Especially in dentistry, implant treatment has become a standard medical practice. The treatment restores full dental functionality, helping patients to maintain high quality of life. However, about 10% of the patients suffer from early and late device failure due to peri-implantitis, an inflammatory disease of the tissues surrounding the implant. Peri-implantitis is caused by progressive microbial colonization of the device surface and the formation of microbial communities, so-called biofilms. This infection can ultimately lead to implant failure. The causative agents for the inflammatory disease, periodontal pathogenic biofilms, have already been extensively studied, but are still not completely understood. As numerical simulations will have the potential to predict oral biofilm formation precisely in the future, for the first time, this study aimed to analyze Streptococcus gordonii biofilms by combining experimental studies and numerical simulation. The study demonstrated that numerical simulation was able to precisely model the influence of different nutrient concentration and spatial distribution of active and inactive biomass of the biofilm in comparison with the experimental data. This model may provide a less time-consuming method for the future investigation of any bacterial biofilm.

In Situ Antibacterial Activity of Essential Oils with and without Alcohol on Oral Biofilm: A Randomized Clinical Trial

Currently, there is little evidence on the in situ antibacterial activity of essential oils (EO) without alcohol. This study aimed to evaluate in situ the substantivity and antiplaque effect on the plaque-like biofilm (PL-biofilm) of two solutions, a traditional formulation that contains EO with alcohol (T-EO) and an alcohol-free formulation of EO (Af-EO). Eighteen healthy adults performed a single mouthwash of: T-EO, Af-EO, and sterile water (WATER) after wearing an individualized disk-holding splint for 2 days. The bacterial viability (BV) and thickness of the PL-biofilm were quantified at baseline, 30 s, and 1, 3, 5, and 7 h post-rinsing (Test 1). Subsequently, each volunteer wore the splint for 4 days, applying two daily mouthwashes of: T-EO, Af-EO, and WATER. The BV, thickness, and covering grade (CG) of the PL-biofilm were quantified (Test 2). Samples were analyzed by confocal laser scanning microscopy after staining with the LIVE/DEAD® BacLight™ solution. To conduct the computations of the BV automatically, a Matlab toolbox called Dentius Biofilm was developed. In test 1, both EO antiseptics had a similar antibacterial effect, reducing BV after a single rinse compared to the WATER, and keeping it below baseline levels up to 7 h post-rinse (P < 0.001). The mean thickness of the PL-biofilm after rinsing was not affected by any of the EO formulations and ranged from 18.58 to 20.19 μm. After 4 days, the T-EO and Af-EO solutions were significantly more effective than the WATER, reducing the BV, thickness, and CG of the PL-biofilm (P < 0.001). Although, both EO antiseptics presented a similar bactericidal activity, the Af-EO rinses led to more significant reductions in the thickness and CG of the PL-biofilm than the T-EO rinses (thickness = 7.90 vs. 9.92 μm, P = 0.012; CG = 33.36 vs. 46.61%, P = 0.001). In conclusion, both essential oils antiseptics had very high immediate antibacterial activity and substantivity in situ on the 2-day PL-biofilm after a single mouthwash. In the 4-day PL-biofilm, both essential oils formulations demonstrated a very good antiplaque effect in situ, although the alcohol-free formula performed better at reducing the biofilm thickness and covering grade.

In vitro efficacy of essential oil mouthrinse versus dentifrices

OBJECTIVES

To compare the antimicrobial efficacy and kill penetration of essential oils (EO) mouthrinse versus stannous fluoride, and triclosan dentifrice slurries on saliva-derived biofilms using confocal laser scanning microscopy (CLSM).

METHODS

Saliva-derived biofilms were grown for 48h on hydroxyapatite discs using pooled, homogenized saliva from 8 healthy volunteers as the inoculum. The mean thickness of these biofilms was 84μm (range, 23-241μm). CLSM with viability mapping was used to visualize the antimicrobial kill penetration of each treatment regime within a biofilm.

RESULTS

At 30s treatment durations, CLSM imaging revealed greater antimicrobial activity and kill penetration of EO mouthrinse compared to sodium fluoride-, stannous fluoride-, and triclosan-containing dentifrice slurries. Quantification of biovolume revealed that EO mouthrinse treatment at 30s resulted in a greater non-viable biovolume proportion (84.6%±15.0%) than other treatment groups. Increasing the treatment duration of the triclosan dentifrice (to 60 and 120s) resulted in better penetration and an increased reduction of viable cells, comparable to EO mouthrinse treatment at 30s duration. Further, CLSM imaging showed that the combined treatment of a non-antimicrobial dentifrice (45s) with EO mouthrinse (30s) showed superior antimicrobial activity (96.2%±3.7%) compared to the antimicrobial triclosan-containing dentifrice used without a mouthrinse step (26.0%±32.0%).

CONCLUSIONS

Within typical exposure times, the EO-containing mouthrinse can penetrate deep into the accumulating plaque biofilm compared to the chemotherapeutic dentifrice slurries, and may provide an efficacious alternative to triclosan, when used as an adjunct with a mechanical oral care regimen.

CLINICAL SIGNIFICANCE

Using viability mapping and CLSM, this study demonstrated that EO-containing mouthrinse penetrates and kills microorganisms deeper and more effectively in plaque biofilm in typical exposure times when compared to dentifrice chemotherapeutic agents, providing an efficacious alternative to triclosan or stannous fluoride when used as an adjunct to mechanical oral care.

Effects of octenidine mouth rinse on apoptosis and necrosis of human fibroblasts and epithelial cells - an in vitro study

This study aimed at comparing the cytotoxicity of a new octenidine mouth rinse (MR) on gingival fibroblasts and epithelial cells using different established MRs. Octenidol (OCT), Chlorhexidine 0.2% (CHX), Meridol (MER), Oral B (OB), and control (PBS only) were used. Human primary gingival fibroblasts (HGFIBs) and human primary nasal epithelial cells (HNEPCs) were cultivated in cell-specific media (2 × 10⁵ cells/well) and treated with a MR or PBS for 1, 5, and 15 min. All tests were performed in duplicate and repeated 12 times. The apoptosis and necrosis were determined using a Caspase-3/7 assay and LDH assay, respectively. The data were analyzed using two-way analysis of variance with subsequent Mann-Whitney U-test. No significant differences could be found between the incubation times of the MR, neither for apoptosis nor necrosis (p > 0.05). Regarding apoptosis of HGFIBs, MRs had no influence at all. In HNEPCs, OCT induced relevantly lower apoptosis than CHX (p = 0.01). Considering necrosis, MER showed the lowest numbers of necrotic HGFIBs and HNEPCs, whereas OB induced the highest number of necrotic cells. The differences between both MR were statistically relevant (p < 0.01). OCT did neither differ from the other MRs nor from the control (PBS) in induction of necrosis in both cell types. In conclusion, the slightly negative effect of OCT considering apoptosis and necrosis of HGFIBs and HNEPCs is nearly the same or even lower compared to the established MRs included in this study. The results confirm that OCT is a potential alternative to CHX.

The effect of a tooth/tongue gel and mouthwash regimen on morning oral malodour: A 3-week single-blind randomized clinical trial

AIM

To compare the effects of a regimen consisting of a tooth/tongue gel, tongue cleaner and mouthwash with the effects of using standard fluoride dentifrice on the organoleptic oral malodour score (ORG) and volatile sulphur compounds (VSCs).

MATERIALS AND METHODS

A total, 66 non-dental students participated in a 3-week parallel, single-blind, randomized, controlled clinical trial. The test group used a tongue cleaner, a tooth/tongue gel and mouthwash containing amine fluoride/stannous fluoride and zinc lactate as oral malodour counteractive. The control group used a standard fluoride dentifrice. Measurements were taken in the morning at baseline, at days 1, 7 and 21. The primary outcome was the ORG score. The secondary outcome, the VSC measurement, was assessed using OralChroma™ (H₂ S, CH₃ SH, (CH₃ )₂ S) and Halimeter^® . Tongue coating thickness and tongue discoloration were scored. At baseline and day 21, the participants' self-perceptions were assessed.

RESULTS

At day 1 for the ORG, H₂ S, CH₃ SH and Halimeter^® readings, a significant decrease was observed in the test group. At day 21, the decrease in H₂ S and the Halimeter^® outcomes were maintained for the test group, and a significant increase in tongue surface discoloration was observed. The test group evaluated their "morning breath upon awakening" as significantly better (P=.001) after 21 days.

CONCLUSION

A significant overnight effect on morning oral malodour was observed for most of the parameters in favour of the test group. At day 21, the effect of prolonged use was significant for H₂ S and the Halimeter^® readings, although not for the primary ORG outcome parameter.

Oxygen tension during biofilm growth influences the efficacy antimicrobial agents

Abstract Objective To compare the antimicrobial efficacy of a 0.12% chlorhexidine (CHX) and herbal green tea (Camellia sinensis) solution on established biofilms formed at different oxygen tensions in an in situ model. Method Twenty-five dental students were eligible for the study. In situ devices with standardized enamel specimens (ES) facing the palatal and buccal sides were inserted in the mouths of volunteers for a 7 day period. No agent was applied during the first four days. From the fifth day onward, both agents were applied to the test ES group and no agent was applied to the control ES group. After 7 days the ES fragments were removed from the devices, sonicated, plated on agar, and incubated for 24 h at 37 °C to determine and quantify the colony forming units (CFUs). Result CHX had significantly higher efficacy compared to green tea on the buccal (1330 vs. 2170 CFU/µL) and palatal (2250 vs. 2520 CFU/µL) ES. In addition, intragroup comparisons showed significantly higher efficacy in buccal ES over palatal ES (1330 vs. 2250 CFU/µL for CHX and 2170 vs, 2520 CFU/µL for CV) for both solutions. Analysis of the ES controls showed significantly higher biofilm formation in palatal ES compared to buccal ES. Conclusion CHX has higher efficacy than green tea on 4-day biofilms. The efficacy of both agents was reduced for biofilms grown in a low oxygen tension environment. Therefore, the oxygen tension environment seems to influence the efficacy of the tested agents.

Devices for In situ Development of Non-disturbed Oral Biofilm. A Systematic Review

Objective: The aim of this review was to assess the types of devices used for in situ development of oral biofilm analyzed microbiologically.

Materials and Methods: A systematic search of the literature was conducted to identify all in situ studies of oral biofilm which used an oral device; the Ovid MEDLINE and EMBASE databases complemented with manual search were used. Specific devices used to microbiologically analyze oral biofilm in adults were included. After reading of the selected full texts, devices were identified and classified according to the oral cavity zone and manufacturing material. The “ideal” characteristics were analyzed in every group.

Results: The search provided 787 abstracts, of which 111 papers were included. The devices used in these studies were classified as palatal, lingual or buccal. The last group was sub-classified in six groups based on the material of the device. Considering the analyzed characteristics, the thermoplastic devices and the Intraoral Device of Overlaid Disk-holding Splints (IDODS) presented more advantages than limitations.

Conclusions: Buccal devices were the most commonly used for the study of in situ biofilm. The majority of buccal devices seemed to slightly affect the volunteer's comfort, the IDODS being the closest to the “ideal” model.

Clinical Relevance: New devices for in situ oral biofilm microbiological studies should take into account the possible effect of their design on the volunteer's comfort and biofilm formation.

Can Chemical Mouthwash Agents Achieve Plaque/Gingivitis Control?

Also note that structured abstracts are not allowed per journal style: What is the effect of a mouthwash containing various active chemical ingredients on plaque control and managing gingivitis in adults based on evidence gathered from existing systematic reviews? The summarized evidence suggests that mouthwashes containing chlorhexidine(CHX) and essential oils (EO) had a large effect supported by a strong body of evidence. Also there was strong evidence for a moderate effect of cetylpyridinium chloride(CPC). Evidence suggests that a CHX mouthwash is the first choice, the most reliable alternative is EO. No difference between CHX and EO with respect to gingivitis was observed.

Ex vivo vs. in vivo antibacterial activity of two antiseptics on oral biofilm

Aim: To compare the immediate antibacterial effect of two application methods (passive immersion and active mouthwash) of two antiseptic solutions on the in situ oral biofilm.

Material and Methods: A randomized observer-masked crossover study was conducted. Fifteen healthy volunteers wore a specific intraoral device for 48 h to form a biofilm in three glass disks. One of these disks was used as a baseline; another one was immersed in a solution of 0.2% Chlorhexidine (0.2% CHX), remaining the third in the device, placed in the oral cavity, during the 0.2% CHX mouthwash application. After a 2-weeks washout period, the protocol was repeated using a solution of Essential Oils (EO). Samples were analyzed for bacterial viability with the confocal laser scanning microscope after previous staining with LIVE/DEAD® BacLight™.

Results: The EO showed a better antibacterial effect compared to the 0.2% CHX after the mouthwash application (% of bacterial viability = 1.16 ± 1.00% vs. 5.08 ± 5.79%, respectively), and was more effective in all layers (p < 0.05). In the immersion, both antiseptics were significantly less effective (% of bacterial viability = 26.93 ± 13.11%, EO vs. 15.17 ± 6.14%, 0.2% CHX); in the case of EO immersion, there were no significant changes in the bacterial viability of the deepest layer in comparison with the baseline.

Conclusions: The method of application conditioned the antibacterial activity of the 0.2% CHX and EO solutions on the in situ oral biofilm. The in vivo active mouthwash was more effective than the ex vivo passive immersion in both antiseptic solutions. There was more penetration of the antiseptic inside the biofilm with an active mouthwash, especially with the EO. Trial registered in clinicaltrials.gov with the number NCT02267239. URL: https://clinicaltrials.gov/ct2/show/NCT02267239.

Antiplaque effect of essential oils and 0.2% chlorhexidine on an in situ model of oral biofilm growth: a randomised clinical trial

OBJECTIVE

To evaluate the in situ antiplaque effect after 4 days of using of 2 commercial antimicrobial agents in short term on undisturbed plaque-like biofilm.

TRIAL DESIGN AND PARTICIPANTS

An observer-masked, crossover randomised clinical trial on 15 oral and systemically healthy volunteers between 20-30 years who were randomly and sequentially allocated in the same group which performed 3 interventions in different randomised sequences.

INTERVENTION

The participants wore an appliance in 3 different rinsing periods doing mouthwashes twice a day (1/0/1) with essential oils, 0.2% chlorhexidine or sterile water (negative control). At the end of each 4-day mouthwash period, samples were removed from the appliance. Posteriorly, after bacterial vital staining, samples were analysed using a Confocal Laser Scanning Microscope.

MAIN OUTCOME MEASURES

Bacterial vitality, thickness and covering grade by the biofilm after 4 days of applying each of the mouthwashes.

RESULTS

The essential oils and the 0.2% chlorhexidine were significantly more effective than the sterile water at reducing bacterial vitality, thickness and covering grade by the biofilm. No significant differences were found between the 0.2% chlorhexidine and the essential oils at reducing the bacterial vitality (13.2% vs. 14.7%). However, the 0.2% chlorhexidine showed more reduction than the essential oils in thickness (6.5 μm vs. 10.0 μm; p<0.05) and covering grade by the biofilm (20.0% vs. 54.3%; p<0.001).

CONCLUSION

The essential oils and 0.2% chlorhexidine showed a high antiplaque effect. Although the 0.2% chlorhexidine showed better results with regard to reducing the thickness and covering grade by the biofilm, both antiseptics showed a high and similar antibacterial activity.

CLINICAL RELEVANCE

Daily essential oils or 0.2% chlorhexidine mouthwashes are effective when reducing dental plaque formation in the short term. Although 0.2% chlorhexidine continues to be the "gold standard" in terms of antiplaque effect, essential oils could be considered a reliable alternative.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02124655.

The intraoral device of overlaid disk-holding splints as a new in situ oral biofilm model

Objectives: To design a device that allows the formation of in situ oral biofilm with similar characteristics to those from the dental plaque, overcoming the limitations of previous devices. Study Design: The Intraoral Device of Overlaid Disk-holding Splints (IDODS) was designed and manufactured. To test its validity, five healthy adult volunteers wore them for two and four days allowing the biofilm to grow without any type of distortion. After each period, the thickness, vitality and structure of the formed biofilm were measured with a Confocal Laser Scanning Microscope (CLSM) in combination with a dual fluorescence solution. All volunteers filled out a Likert-type questionnaire to evaluate the device. Results: Mean bacterial vitality in the 2- and 4-day biofilms was 71% and 63%, respectively. Mean thicknesses were 21 µm and 28 µm, respectively. There was predominance in the open and heterogeneous structure whose complexity was ascending as the biofilm matured. The results obtained from the questionnaire were 2/5 in the influence in aesthetics, 3.4/5 in comfort, and 5/5 in ease of maintaining oral hygiene and withdrawal from the oral cavity. Conclusions: A biofilm with optimum characteristics was obtained by IDODS. Its use is associated with good aesthetic and comfort results and is absent of functional limitations, allowing optimal oral hygiene without altering the structure of the in situ oral biofilm.

Key words:Confocal Laser Scanning Microscope, fluorochromes, in situ, intraoral device, oral biofilm.

Use of a high-throughput in vitro microfluidic system to develop oral multi-species biofilms

There are few high-throughput in vitro systems which facilitate the development of multi-species biofilms that contain numerous species commonly detected within in vivo oral biofilms. Furthermore, a system that uses natural human saliva as the nutrient source, instead of artificial media, is particularly desirable in order to support the expression of cellular and biofilm-specific properties that mimic the in vivo communities. We describe a method for the development of multi-species oral biofilms that are comparable, with respect to species composition, to supragingival dental plaque, under conditions similar to the human oral cavity. Specifically, this methods article will describe how a commercially available microfluidic system can be adapted to facilitate the development of multi-species oral biofilms derived from and grown within pooled saliva. Furthermore, a description of how the system can be used in conjunction with a confocal laser scanning microscope to generate 3-D biofilm reconstructions for architectural and viability analyses will be presented. Given the broad diversity of microorganisms that grow within biofilms in the microfluidic system (including Streptococcus, Neisseria, Veillonella, Gemella, and Porphyromonas), a protocol will also be presented describing how to harvest the biofilm cells for further subculture or DNA extraction and analysis. The limits of both the microfluidic biofilm system and the current state-of-the-art data analyses will be addressed. Ultimately, it is envisioned that this article will provide a baseline technique that will improve the study of oral biofilms and aid in the development of additional technologies that can be integrated with the microfluidic platform.

Non-invasive in vivo imaging by confocal laser scanning microscopy of gingival tissues following natural plaque deposition

AIM

Imaging with Confocal Laser Scanning Microscopy (CLSM) generates high-resolution images and may be well suited for basic research in Periodontology and Implant Dentistry. The present study was aimed to explore the in vivo application of CLSM in experimentally induced gingivitis.

MATERIALS AND METHODS

Ten subjects were recruited and were advised to stop any oral hygiene of the upper front teeth for 7 days. The gingival tissues were observed using a Heidelberg Retina Tomograph combined with a Rostock Cornea Module at baseline and day 7. The system used a laser of 670 nm and the contrast was given by backscattering from different tissues. Each examination created 800-1200 images that were descriptively analysed.

RESULTS

After 7 days of abandoned oral hygiene, plaque scores and bleeding frequencies increased. By using CLSM images tooth hard substances, cells and plaque deposits were distinguishable. Increased epithelial cell irregularities, the apical migration of the sulcular epithelium, cellular infiltrates within the sulcus and plaque deposits were observed at day 7.

CONCLUSIONS

The present study showed for the first time that CLSM is suitable for in vivo imaging of the gingival sulcus and adjacent tissues.

Confusion over live/dead stainings for the detection of vital microorganisms in oral biofilms--which stain is suitable?

BACKGROUND

There is confusion over the definition of the term "viability state(s)" of microorganisms. "Viability staining" or "vital staining techniques" are used to distinguish live from dead bacteria. These stainings, first established on planctonic bacteria, may have serious shortcomings when applied to multispecies biofilms. Results of staining techniques should be compared with appropriate microbiological data.

DISCUSSION

Many terms describe "vitality states" of microorganisms, however, several of them are misleading. Authors define "viable" as "capable to grow". Accordingly, staining methods are substitutes, since no staining can prove viability.The reliability of a commercial "viability" staining assay (Molecular Probes) is discussed based on the corresponding product information sheet: (I) Staining principle; (II) Concentrations of bacteria; (III) Calculation of live/dead proportions in vitro. Results of the "viability" kit are dependent on the stains' concentration and on their relation to the number of bacteria in the test. Generally this staining system is not suitable for multispecies biofilms, thus incorrect statements have been published by users of this technique.To compare the results of the staining with bacterial parameters appropriate techniques should be selected. The assessment of Colony Forming Units is insufficient, rather the calculation of Plating Efficiency is necessary. Vital fluorescence staining with Fluorescein Diacetate and Ethidium Bromide seems to be the best proven and suitable method in biofilm research.Regarding the mutagenicity of staining components users should be aware that not only Ethidium Bromide might be harmful, but also a variety of other substances of which the toxicity and mutagenicity is not reported.

SUMMARY

- The nomenclature regarding "viability" and "vitality" should be used carefully.- The manual of the commercial "viability" kit itself points out that the kit is not suitable for natural multispecies biofilm research, as supported by an array of literature.- Results obtained with various stains are influenced by the relationship between bacterial counts and the amount of stain used in the test. Corresponding vitality data are prone to artificial shifting.- As microbiological parameter the Plating Efficiency should be used for comparison.- Ethidium Bromide is mutagenic. Researchers should be aware that alternative staining compounds may also be or even are mutagenic.

Chlorhexidine substantivity on salivary flora and plaque-like biofilm: an in situ model

OBJECTIVE

To evaluate the in situ antibacterial activity of a mouthrinse with 0.2% Chlorhexidine (M-0.2% CHX) on undisturbed de novo plaque-like biofilm (PL-biofilm) and on salivary flora up to 7 hours after its application.

METHODS

A special acrylic appliance was designed, with 3 inserted glass disks on each buccal side, allowing for PL-biofilm growth. Fifteen healthy volunteers wore the appliance for 48 hours and then performed an M-0.2% CHX; disks were removed at 30 seconds and 1, 3, 5 and 7 hours after the mouth-rinsing. Applying a washout period, saliva samples were collected from each volunteer at 30 seconds and 1, 3, 5 and 7 hours after performing an M-0.2% CHX. The PL-biofilm and saliva samples were analysed by confocal laser scanning and epifluorescence microscopes, respectively.

RESULTS

At 30 seconds after M-0.2% CHX, the levels of viable bacteria detected in saliva were significantly lower than those observed in PL-biofilm. The difference in the percentage of live bacteria detected in saliva was significantly higher than that observed in PL-biofilm at 5 and 7 hours after M-0.2% CHX.

CONCLUSION

After a single mouthrinse of the 0.2% CHX formulation tested in the present study, the 2-day PL-biofilm presented a significantly higher resistance to this antiseptic in situ than that observed in salivary flora. However, this 0.2% CHX formulation showed a higher substantivity on PL-biofilm than on salivary flora at 5 and 7 hours after mouth-rinsing, which could be related to the slower growth rate of PL-biofilm and the possible reservoir function for antimicrobial agents associated with the undisturbed de novo PL-biofilm.

Action of food preservatives on 14-days dental biofilm formation, biofilm vitality and biofilm-derived enamel demineralisation in situ

AIMS

The aims of this double-blind, controlled, crossover study were to assess the influence of food preservatives on in situ dental biofilm growth and vitality, and to evaluate their influence on the ability of dental biofilm to demineralize underlying enamel over a period of 14 days.

MATERIALS AND METHODS

Twenty volunteers wore appliances with six specimens each of bovine enamel to build up intra-oral biofilms. During four test cycles of 14 days, the subjects had to place the appliance in one of the assigned controls or active solutions twice a day for a minute: negative control 0.9 % saline, 0.1 % benzoate (BA), 0.1 % sorbate (SA) and 0.2 % chlorhexidine (CHX positive control). After 14 days, the biofilms on two of the slabs were stained to visualize vital and dead bacteria to assess biofilm thickness (BT) and bacterial vitality (BV). Further, slabs were taken to determine mineral loss (ML), by quantitative light-induced laser fluorescence (QLF) and transversal microradiography (TMR), moreover the lesion depths (LD).

RESULTS

Nineteen subjects completed all test cycles. Use of SA, BA and CHX resulted in a significantly reduced BV compared to NaCl (p < 0.001). Only CHX exerted a statistically significant retardation in BT as compared to saline. Differences between SA and BA were not significant (p > 0.05) for both parameters. TMR analysis revealed the highest LD values in the NaCl group (43.6 ± 44.2 μm) and the lowest with CHX (11.7 ± 39.4 μm), while SA (22.9 ± 45.2 μm) and BA (21.4 ± 38.5 μm) lay in between. Similarly for ML, the highest mean values of 128.1 ± 207.3 vol% μm were assessed for NaCl, the lowest for CHX (-16.8 ± 284.2 vol% μm), while SA and BA led to values of 83.2 ± 150.9 and 98.4 ± 191.2 vol% μm, respectively. With QLF for both controls, NaCl (-33.8 ± 101.3 mm(2) %) and CHX (-16.9 ± 69.9 mm(2) %), negative values were recorded reflecting a diminution of fluorescence, while positive values were found with SA (33.9 ± 158.2 mm(2) %) and BA (24.8 ± 118.0 mm(2) %) depicting a fluorescence gain. These differences were non-significant (p > 0.05).

CONCLUSION

The biofilm model permited the assessment of undisturbed oral biofilm formation influenced by antibacterial components under clinical conditions for a period of 14 days. An effect of BA and SA on the demineralization of enamel could be demonstrated by TMR and QLF, but these new findings have to be seen as a trend. As part of our daily diet, these preservatives exert an impact on the metabolism of the dental biofilm, and therefore may even influence demineralization processes of the underlying dental enamel in situ.

Efficacy of different mouthrinse formulations in reducing oral malodour: a randomized clinical trial

AIMS

The aim of this study was to assess the efficacy of mouthrinses formulations in oral malodour.

MATERIAL & METHODS

This single-centre, double-blind, randomized, parallel group clinical trial compared the efficacy of Halita™ and meridol(®) with and without zinc lactate versus negative and positive control. Volunteers with confirmed oral malodour (18/group) rinsed with one mouthrinse during 7 days (15 ml, 2x/day for 1 min.). 15 min. after a first rinse (masking effect), and after 7 days (therapeutic effect) the change in organoleptic scores and level of sulphur compounds was recorded.

RESULTS

All rinses showed a masking effect (OLS 1 to 2 values reduced), only the rinses with antimicrobial ingredients showed a therapeutic effect (OLS 1 to 1.5 value less). The addition of zinc resulted in a more pronounced masking effect. Halita™ and meridol(®) with zinc showed the best therapeutic effect.

CONCLUSION

Although the masking effect of the rinses can be attributed partially to a dilution and the effect of aromas, the therapeutic effect should be linked to the anti-microbial action of active ingredients and counter action of zinc ions on VSC. A complete resolution of the unpleasant breath by additional mechanical intervention remains to be proven.

In situ chlorhexidine substantivity on saliva and plaque-like biofilm: influence of circadian rhythm

BACKGROUND

The aim of the present study is to assess in situ substantivity of a single mouthrinse with 0.2% chlorhexidine (CHX) on saliva and on undisturbed de novo plaque-like biofilm (PL-biofilm), differentiating between two times of application: 1) CHX mouthrinse in the morning; and 2) CHX mouthrinse at night.

METHODS

The study participants were 10 healthy volunteers who wore an individualized splint with glass disks for 48 hours to boost the growth of PL-biofilm. Saliva samples were collected, and two disks were removed from each volunteer's splint at 8, 10, and 12 hours after performing a mouthrinse with 0.2% CHX at 7:00 am (M-0.2% CHX-diurnal) and 1:00 am (M-0.2% CHX-nocturnal). The saliva and plaque samples were analyzed by epifluorescence and confocal laser scanning microscopy, respectively, using a green fluorescent nucleic acid stain/propidium iodide staining.

RESULTS

With M-0.2% CHX-diurnal, the frequency of vital bacteria in saliva was significantly higher than in the PL-biofilm at 8, 10, and 12 hours after mouthrinse. After M-0.2% CHX-nocturnal, the frequency of vital bacteria in saliva was significantly lower than in the PL-biofilm at 8 hours and higher than in the PL-biofilm at 12 hours after mouthrinse.

CONCLUSION

These results support the more active physiologic dynamics of the salivary flora and the possible reservoir function associated with the structure of undisturbed de novo PL-biofilm.

Biofilm Formation on Composite Resins for Dental Restorations: An in Situ Study on the Effect of Chlorhexidine Mouthrinses

Purpose

Biofilm formation on the surface of dental restorative materials by oral bacteria is considered an important step in the development of secondary caries. The aim of this study was to evaluate the in situ effect of a chlorhexidine (CHX)-containing mouthrinse on the biofilm formation occurring on the surface of human enamel and of two resin-based commercially available materials: a silorane-based material (Filtek Silorane®) and a methacrylate-based material (Filtek Supreme XT®).

Methods

53 disks were obtained for each of the two composites and 37 disks for enamel. The surface was characterized by determining the surface roughness and the surface free energy of 5 samples for each of the three materials tested, then the remaining samples were mounted on splints worn by 16 volunteers. The participants were randomly divided into two groups: an experimental group that used 0.12% CHX-based mouthrinse and a control group that used a placebo mouthrinse. Biofilm formation on the different surfaces after a 24 h period was assessed using MTT assay.

Results

The two composites in the group treated with the placebo mouthrinse showed a similar biofilm formation, which was significantly higher than that occurring on enamel surfaces. The CHX-based mouthrinse significantly reduced biofilm formation on the surfaces of the two resin-based materials when compared with the placebo mouthrinse. The reduction was particularly relevant on the Filtek Silorane surfaces.

Conclusions

The new silorane-based material seems to interact with CHX in a promising way from the point of view of biofilm formation control.

Antimicrobial effect of chlorhexidine digluconate in dentin: In vitro and in situ study

Aim:

The aim of this study was to evaluate a very short-term in vitro and in situ effect of 2% chlorhexidine-digluconate-based (CHX) cavity cleanser on the disinfection of dentin demineralized by cariogenic bacteria.

Materials and Methods:

Human dentin slabs were randomly allocated and used in 2 distinct phases, in vitro and in situ, for obtaining demineralized dentin. In vitro, the slabs (n=15) were immersed for 5 days in BHI broth inoculated with Streptococcus mutans CTT 3440. In situ, a double-blind design was conducted in one phase of 14 days, during which 20 volunteers wore palatal devices containing two human dental dentin slabs. On 5^th day in vitro and 14^th day in situ, the slabs were allocated to the two groups: Control group (5 μl of 0.9% NaCl solution) and CHX group (5 μl of 2% chlorhexidine digluconate solution, Cavity Cleanser™ BISCO, Schaumburg, IL, EUA), for 5 minutes. The microbiological analyses were performed immediately before and after the treatments.

Results:

The log reductions means found for CHX treatment on tested micro organisms were higher when compared to Control group either in vitro or in situ conditions.

Conclusions:

Our results showed that CHX was effective in reducing the cultivable microbiota in contaminated dentin. Furthermore, although the use of chlorhexidine-digluconate-based cavity disinfectant did not completely eliminate the viable microorganisms, it served as a suitable agent to disinfect tooth preparations.

Inhibition of early biofilm formation by glass-ionomer incorporated with chlorhexidine in vivo: a pilot study

BACKGROUND

This pilot study investigated the antibiofilm effects of glass-ionomer cements (GICs) and resin-modified glass-ionomer cements (RMGICs) incorporated with chlorhexidine (CHX) in vivo.

METHODS

Experimental GICs and RMGICs containing 2% CHX were obtained by mixing CHX with the powder of GICs (CHXGIC) and RMGICs (CHXRMGIC). Four groups of specimens were prepared in a standardized size. After polishing and sterilization, they were bonded to the buccal surface of the molars in the first and second quadrant of volunteers and left untouched for 4 hours and 24 hours, respectively. The bacterial vitality of plaque was then analysed by confocal laser scanning microscopy (CLSM). The bacterial morphology and biofilm accumulation were determined by scanning electron microscopy (SEM). The pH value of biofilm was assessed by Plaque Indicator Kits.

RESULTS

CLSM analysis revealed that bacterial vitality of the biofilm on CHXGIC and CHXRMGIC was significantly lower than that on GIC and RMGIC. SEM analysis indicated that the morphology of bacteria on CHXGIC and CHXRMGIC was irregular. The pH value of biofilm on the experimental materials presented no statistically significant difference.

CONCLUSIONS

Twenty-four hour bacterial vitality on GICs and RMGICs with CHX are lower in micro-organisms than on conventional GICs and RMGICs.

Effect of ZnCl2 on plaque growth and biofilm vitality

OBJECTIVE

The aim of this study was to evaluate the effects of ZnCl(2) on plaque-growth and vitality pattern of dental biofilm and to determine the optimum zinc concentration for the inhibition of plaque formation.

DESIGN

Data were collected from nine volunteers for whom a special-designed acrylic appliance was prescribed after a careful dental check up. The volunteers rinsed twice daily for 2min with ZnCl(2) of 2.5, 5, 10, 20mM as treatment and double distilled water (DDW) as control in respective assigned test weeks. The plaque index (PI) was assessed after 48h of appliance wearing. The glass discs with the adhered biofilm were removed from the splints and stained with two fluorescent dyes. The biofilm thickness (BT) and bacterial vitality of the whole biofilm as well as the mean bacterial vitality (BV) of the inner, middle and outer layers of biofilm were evaluated under confocal laser scanning microscope (CLSM).

RESULTS

PI, BT and BV of biofilms treated by various concentrations of ZnCl(2) were reduced significantly when compared with the DDW group (p<0.05). PI, BT and BV of the 2.5mM ZnCl(2) group was significantly higher than groups of 5, 10, 20mM ZnCl(2) (p<0.05). The mean BV of the 3 layers (inner, middle and outer layers) showed that 2.5mM ZnCl(2) was the lowest concentration to inhibit BV in the outer layer, 5mM was the lowest concentration to extend this inhibition of BV to the middle layer, and none of the concentrations investigated in this study has shown any effect on bacteria inhibition in the inner layer.

CONCLUSION

Zinc ions exhibited possible inhibitory effects on plaque formation, and have a promising potential to be used as an antibacterial agent in future dentifrices and mouthrinses.

Quantification of vital adherent Streptococcus sanguinis cells on protein-coated titanium after disinfectant treatment

The quantification of vital adherent bacteria is challenging, especially when efficacy of antimicrobial agents is to be evaluated. In this study three different methods were compared in order to quantify vital adherent Streptococcus sanguinis cells after exposure to disinfectants. An anaerobic flow chamber model accomplished initial adhesion of S. sanguinis on protein-coated titanium. Effects of chlorhexidine, Betadine®, Octenidol®, and ProntOral® were assessed by quantifying vital cells using Live/Dead BacLight™, conventional culturing and isothermal microcalorimetry (IMC). Results were analysed by Kruskal-Wallis one-way analysis of variance. Live/dead staining revealed highest vital cell counts (P < 0.05) and demonstrated dose-dependent effect for all disinfectants. Microcalorimetry showed time-delayed heat flow peaks that were proportioned to the remaining number of viable cells. Over 48 h there was no difference in total heat between treated and untreated samples (P > 0.05), indicating equivalent numbers of bacteria were created and disinfectants delayed growth but did not eliminate it. In conclusion, contrary to culturing, live/dead staining enables detection of cells that may be viable but non-cultivable. Microcalorimetry allows unique evaluation of relative disinfectant effects by quantifying differences in time delay of regrowth of remaining vital cells.