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

A novel non-cytotoxic synthetic peptide, Pug-1, exhibited an antibiofilm effect on Streptococcus mutans adhesion

The aim of this study was to evaluate the effects of synthetic peptides on the growth and biofilm formation of Streptococcus mutans and their cytotoxicity on a human keratinocyte cell line. Four pomegranate-derived peptides; Pug-1, Pug-2, Pug-3 and Pug-4 were synthesized. Streptococcus mutans (ATCC 25175 and DMST 41283) were used. The antibacterial and anti-adherence activities of the peptides were evaluated. The effect of the peptides on S. mutans glucosyltransferase (Gtf) activity was measured. The peptides' cytotoxicity was evaluated on a HaCaT cell line using an MTT assay. The bactericidal penetration depth of Pug-1 into the biofilm was investigated using confocal laser scanning microscopy (CLSM). Among the four peptides, Pug-1 (200 µg ml^-1 ) exhibited antibacterial activity on S. mutans (DMST 41283). All peptides demonstrated anti-adherence activity. Streptococcus mutans Gtf activity was significantly inhibited by Pug-1. Interestingly, Pug-1 peptide was not cytotoxic to the HaCaT cell line. Pug-1 (100-200 µg ml^-1 ) exhibited bactericidal penetration at approximately 50-100% of the biofilm depth. Therefore, Pug-1 might be a candidate of anticariogenic agent. SIGNIFICANCE AND IMPACT OF THE STUDY: Our data highlighted that pomegranate-derived antimicrobial peptides (AMPs) inhibit Streptococcus mutans adhesion, virulence-associated genes and enzymes. This in vitro study supports the hypothesis that pomegranate AMPs would be noncytotoxic to human keratinocytes, with a potent anticariogenic effect via an anti-adherence mode-of-action. The present study provides evidence for further investigation of these AMPs as therapeutic and preventive agents for dental caries.

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.

Oral Biofilm Formation on Different Materials for Dental Implants

Dental implants and their prosthetic components are prone to bacterial colonization and biofilm formation. The use of materials that provides low microbial adhesion may reduce the prevalence and progression of peri-implant diseases. In view of the oral environment complexity and oral biofilm heterogeneity, microscopy techniques are needed that can enable a biofilm analysis of the surfaces of teeth and dental materials. This article describes a series of protocols implemented for comparing oral biofilm formation on titanium and ceramic materials for prosthetic abutments, as well as the methods involved in oral biofilms analyses at the morphological and cellular levels. The in situ model to evaluate oral biofilm formation on titanium and zirconia materials for dental prosthesis abutments as described in this study provides a satisfactory preservation of the 48 h biofilm, thereby demonstrating methodological adequacy. Multiphoton microscopy allows the analysis of an area representative of the biofilm formed on the test materials. In addition, the use of fluorophores and the processing of the images using multiphoton microscopy allows the analysis of the bacterial viability in a very heterogeneous population of microorganisms. The preparation of biological specimens for electron microscopy promotes the structural preservation of biofilm, images with good resolution, and no artifacts.

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.

Full validation of a method for the determination of drugs of abuse in non-mineralized dental biofilm using liquid chromatography-tandem mass spectrometry and application to postmortem samples

Alternative matrices play a major role in postmortem forensic toxicology, especially if common matrices (like body fluids or hair) are not available. Incorporation of illicit and medicinal drugs into non-mineralized dental biofilm (plaque) seems likely but has not been investigated so far. Analysis of plaque could therefore extend the spectrum of potentially used matrices in postmortem toxicology. For this reason, a rapid, simple and sensitive method for the extraction, determination and quantification of ten drugs of abuse from plaque using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and fully validated. Amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), 3,4-methylenedioxyamphetamine (MDA), cocaine, benzoylecgonine, morphine, codeine and 6-acetylmorphine were extracted from 2mg of dried and powdered plaque via ultrasonication with acetonitrile. The extracts were analyzed on a triple-quadrupole linear ion trap mass spectrometer in scheduled multiple reaction monitoring mode (sMRM). The method was fully validated and proved accurate, precise, selective and specific with satisfactory linearity within the calibrated ranges. The lower limit of quantification was 10-15pgmg^-1 for all compounds except for MDA (100pgmg^-1) and amphetamine (200pgmg^-1). The method has been successfully applied to three authentic postmortem samples with known drug history. Amphetamine, MDMA, cocaine, benzoylecgonine, morphine and codeine could be detected in these cases in concentrations ranging from 18pgmg^-1 for cocaine to 1400pgmg^-1 for amphetamine.

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.

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.