Dental plaque as a microbial biofilm

Effect of Novel Antibacterial Composites on Bacterial Biofilms

Continuing cariogenic bacterial growth demineralizing dentine beneath a composite filling is the most common cause of tooth restoration failure. Novel composites with antibacterial polylysine (PLS) (0, 4, 6, or 8 wt%) in its filler phase were therefore produced. Remineralising monocalcium phosphate was also included at double the PLS weight. Antibacterial studies involved set composite disc placement in 1% sucrose-supplemented broth containing Streptococcus mutans (UA159). Relative surface bacterial biofilm mass (n = 4) after 24 h was determined by crystal violet-binding. Live/dead bacteria and biofilm thickness (n = 3) were assessed using confocal laser scanning microscopy (CLSM). To understand results and model possible in vivo benefits, cumulative PLS release from discs into water (n = 3) was determined by a ninhydrin assay. Results showed biofilm mass and thickness decreased linearly by 28% and 33%, respectively, upon increasing PLS from 0% to 8%. With 4, 6, and 8 wt% PLS, respectively, biofilm dead bacterial percentages and PLS release at 24 h were 20%, 60%, and 80% and 85, 163, and 241 μg/disc. Furthermore, initial PLS release was proportional to the square root of time and levelled after 1, 2, and 3 months at 13%, 28%, and 42%. This suggested diffusion controlled release from water-exposed composite surface layers of 65, 140, and 210 μm thickness, respectively. In conclusion, increasing PLS release initially in any gaps under the restoration to kill residual bacteria or longer-term following composite/tooth interface damage might help prevent recurrent caries.

Influence of a novel pH-cycling model using dental microcosm biofilm on the remineralizing efficacy of fluoride in early carious lesions

OBJECTIVES

To evaluate the remineralizing efficacy of fluoride in early carious lesions using a novel microbial pH-cycling model that combines the chemical pH-cycling model with dental microcosm biofilms.

MATERIALS AND METHODS

Artificial carious lesions were formed in 48 bovine incisors. The chemical and microbial pH-cycling models were applied to 24 specimens, respectively; the latter was applied after formation of dental microcosm biofilms for 6 days, based on the human saliva inoculation. The pH-cycling schedule was repeated for 12 days. All specimens were evaluated for fluorescence loss (ΔF) using quantitative light-induced fluorescence-digital before and after the pH-cycling. Specimen biofilms were further analyzed for red/green values (R/G ratios) and colony-forming units (CFUs). One-way analysis of variance and Tukey's post hoc analysis were used to analyze change in fluorescence loss (ΔΔF) according to the pH-cycling model and treatment.

RESULTS

When the chemical pH-cycling and microbial pH-cycling models were used, ΔΔF was 1.36 (p = 0.008) and 1.17 (p > 0.05) times higher, respectively, in the fluoride-treated group than that in the distilled water-treated group. In the microbial pH-cycling model, R/G ratios and CFU counts of biofilms were not significantly different between treatments (p > 0.05).

CONCLUSIONS

No significant difference was observed in the remineralizing efficacy of fluoride according to the presence of dental biofilms covering early carious lesions.

CLINICAL RELEVANCE

The remineralizing efficacy of fluoride could be overestimated in the absence of dental biofilms. Therefore, for accurate evaluation of the clinical value of remineralizing agents, dental biofilms should be included in in vitro tests.

Characterization of biofilm formed by multidrug resistant Pseudomonas aeruginosa DC-17 isolated from dental caries

The present work reports with the screening of biofilm-producing bacteria from the dental caries. The dental pathogens showed resistance against various antibiotics and biofilm forming ability at various levels. Among the bacterial strain, Pseudomonas aeruginosa DC-17 showed enhanced biofilm production. Extracellular polymeric substance (EPS) was synthesized by the selected bacterial isolate considerably and contributed as the major component of biofilm. EPS composed of eDNA, proteins and lipids. The total protein content of the EPS was found to be 1.928 mg/mL and was the major component than carbohydrate and DNA. Carbohydrate content was 162.3 mg/L and DNA content of EPS was 4.95 μg/mL. These macromolecules interacted in the matrix to develop dynamic and specific interactions to signalling biofilm to differentiating various environments. Also, the isolated bacteria showed resistant against various commercially available antibiotics. The isolates showed more resistance against penicillin (98%) and were sensitive against amoxicillin. Among the factors, temperature, pH and sugar concentration influenced biofilm formation. Biofilm forming ability of the selected bacterial stain was tested at various pH values and alkaline pH was favoured for biofilm production. Biofilm production was found to be maximum at 40 °C and 8% sucrose enhanced biofilm formation. Biofilm formed by P. aeruginosa DC-17 was resistant against various tested antimicrobials and chemicals.

Suppressive Effects of Hainosan (Painongsan) against Biofilm Production by Streptococcus mutans

Streptococcus mutans, a bacterium that causes dental plaques, forms a biofilm on tooth surfaces. This biofilm can cause gingivitis by stimulating the gingival margin. However, there is no established treatment for biofilm removal. Hainosan (Painongsan), a traditional Japanese Kampo formula, has been used to treat gingivitis. Therefore, we investigated the biofilm suppressive effects of the hainosan extract (HNS) and its components on S. mutans. We conducted scanning electron microscopy and confocal laser microscopy analyses to clarify the anti-biofilm activities of HNS and its crude drugs. We also performed a quantitative RT-PCR assay to assess the biofilm-related gene expression. HNS showed a significant dose-dependent suppressive effect on biofilm formation. Both the scanning electron microscopy and confocal laser microscopy analyses also revealed the significant inhibitory effects of the extract on biofilm formation. Transmission electron microscopy analysis showed that HNS disrupted the surface of the bacterial wall. Furthermore, HNS reduced the hydrophobicity of the bacteria, and suppressed the mRNA expression of β-glucosyltransferase (gtfB), glucosyltransferase-SI (gtfC), and fructosyltransferase (ftf). Among the constituents of hainosan, the extract of the root of Platycodon grandiflorum (PG) showed the strongest biofilm suppression effect. Platycodin D, one of the constituent natural compounds of PG, inhibited S. mutans-associated biofilm. These findings indicate that hainosan eliminates dental plaques by suppressing biofilm formation by S. mutans.

Effect of Etching Procedures on the Adhesion of Biofilm-Coated Dentin

Oral biofilms coat all surfaces in the oral cavity including the exposed dentin surface. This study aimed to investigate biofilm removal by acid etching procedures and the effects of the residual biofilm on dentin surfaces on composite-dentin adhesion. Dentin discs were assigned to five groups: no biofilm formation (C); biofilm formation and no surface treatment (BF); biofilm formation and acid etching (BF-E); biofilm formation and acid etching followed by chlorhexidine soaking (BF-EC); and biofilm formation and rubbing with pumice, followed by acid etching (BF-RE). Biofilms were formed on saliva-precoated dentin discs by soaking the discs in Streptococcus mutans (S. mutans) suspension. Biofilm removal from the dentin surface was evaluated quantitatively and qualitatively by confocal laser scanning microscopy and scanning electron microscopy, respectively. To compare the bond strength of the biofilm-coated dentin discs with the surface treatments, specimens were assigned to four groups: no biofilm formation and acid etching (C-E); BF-E; BF-EC; and BF-RE. Assessments of the micro-shear bond strength and subsequent failure modes were performed. BF-E and BF-EC did not remove the biofilm, whereas BF-RE partially removed the biofilm attached to the dentin (p < 0.05). The bond strength of BF-RE was significantly higher than those of BF-E and BF-EC, but lower than that of C-E (p < 0.05). In conclusion, mechanical biofilm removal is recommended before etching procedures to enhance adhesion to the biofilm-coated dentin.

Antibiofilm efficacy of tea tree oil and of its main component terpinen-4-ol against Candida albicans

Candida infection is an important cause of morbidity and mortality in immunocompromised patients. The increase in its incidence has been associated with resistance to antimicrobial therapy and biofilm formation. The aim of this study was to evaluate the efficacy of tea tree oil (TTO) and its main component - terpinen-4-ol - against resistant Candida albicans strains (genotypes A and B) identified by molecular typing and against C. albicans ATCC 90028 and SC 5314 reference strains in planktonic and biofilm cultures. The minimum inhibitory concentration, minimum fungicidal concentration, and rate of biofilm development were used to evaluate antifungal activity. Results were obtained from analysis of the biofilm using the cell proliferation assay 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and confocal laser scanning microscopy (CLSM). Terpinen-4-ol and TTO inhibited C. albicans growth. CLSM confirmed that 17.92 mg/mL of TTO and 8.86 mg/mL of terpinen-4-ol applied for 60 s (rinse simulation) interfered with biofilm formation. Hence, this in vitro study revealed that natural substances such as TTO and terpinen-4-ol present promising results for the treatment of oral candidiasis.

Biofilm formation on different dental restorative materials in the oral cavity

Background

Bacterial biofilms adhere to all tissues and surfaces in the oral cavity. Oral biofilms are responsible for the decay of human dental structures and the inflammatory degeneration of the alveolar bone. Moreover, oral biofilms on artificial materials influence the lifespan of dental prostheses and restoratives.

Methods

To investigate in vivo oral biofilm formation and growth, five different dental restorative materials were analyzed and compared to human enamel. The roughness of the materials and the human enamel control probe were measured at the start of the study. The dental restorative materials and the human enamel control probe were placed in dental splints and worn for 3 h, 24 h and 72 h.

Results

Scanning electron microscopy (SEM) revealed major differences between oral biofilm formation and growth on the materials compared to those on human enamel. Microbiological analyses showed that bacterial strains differed between the materials. Significant differences were observed in the roughness of the dental materials.

Conclusions

It can be concluded that material roughness affects biofilm formation on dental surfaces and restoratives, but other factors, such as surface charge, surface energy and material composition, may also have an influence.

H-type lectins - Structural characteristics and their applications in diagnostics, analytics and drug delivery

Lectins are ubiquitous carbohydrate-binding proteins that interact with sugar moieties in a highly specific manner. H-type lectins represent a new group of lectins that were identified in invertebrates. These lectins share structural homology and bind mainly to N-acetylgalactosamine (GalNAc). Recent structural studies on the H-type lectins provided a detailed description of the GalNAc-lectin interaction that is already exploited in a number of biomedical applications. Two members of the H-type lectin family, Helix pomatia agglutinin (HPA) and Helix aspersa agglutinin (HAA), have already been extensively used in many diagnostic tests due their ability to specifically recognize GalNAc. This ability is especially important because aberrant glycosylation patterns of proteins expressed by cancer cells contain GalNAc. In addition, H-type lectins were utilized in diagnostics of other non-cancer diseases and represent great potential as components of drug delivery systems. Here, we present an overview of the H-type lectins and their applications in diagnostics, analytics and drug delivery.

Bacterial Populations in Subgingival Plaque Under Healthy and Diseased Conditions: Genomic Insights into Oral Adaptation Strategies by Lactobacillus sp. Strain DISK7

Human oral cavity is a complex habitat comprising about 700 microbial species and represents the most complex microbiota after gastrointestinal tract. In fact, oral microbiota directly influences health, metabolism and immune responses of the host. Metagenomic studies based on 16S rDNA profiling has reported the inhabitant bacteria mainly belonging to phyla Firmicutes, Proteobacteria, Actinobacteria, Fusobacteria, Spirochaetes and Bacteroidetes. Therefore, it is essential to isolate these strains and characterize in detail to understand their interaction. We have isolated strains from subgingival plaque from healthy to diseased individuals and the molecular characterization based on 16S rRNA gene sequence analysis showed predominance of Firmicutes, specifically members of the genus Streptococcus. Species of Lactobacillus and Veillonella were also found in significant number, which are considered as secondary colonizers. However, the population of Lactobacillus was decreased in diseased conditions with the increase in opportunistic pathogenic strains pertaining to genera like Campylobacter, Neisseria, Enterobacter, Pseudomonas and Morococcus. Further, we have also made an attempt to gain genomic insights on adaptation features and interactions of an isolate, Lactobacillus sp. strain DISK7 by performing whole genome sequencing and analysis, subsequently biochemical characterization to explore its functional and metabolic properties for the development as probiotic agent.

Photodynamic therapy in oral lichen planus: A prospective case-controlled pilot study

Oral lichen planus (OLP) is a common, chronic relapsing inflammatory disorder of the mucous membranes, which causes major discomfort. Current treatment includes topical/systemic glucocorticoids, immune modulators and systemic immunosuppressants, which may lead to considerable side-effects. The aim of this study was to determine the clinical and immunological efficacy of photodynamic therapy (PDT) in OLP as an alternative, easy-to-use, safe and non-invasive treatment. Twenty patients with OLP were treated with PDT in a prospective case-controlled pilot-study. PDT was performed on the most extensive oral lesion in 4 sessions (day 1, 3, 7, 14). Peripheral blood and lesional T cells were analysed before (day 1) and after PDT treatment (day 28). PDT led to a statistically significant reduction of clinical parameters (lesion size, ABSIS, Thongprasom-score) and improvement of all evaluated quality-of-life (QOL) items. The clinical improvement was accompanied by a significant decrease of the relative number of CD4+ and CD8+ T cells in mucosal OLP-lesions. Furthermore, CXCL10 plasma levels were decreased and the number of activated peripheral CD4 + CD137+ and CD8 + CD137+ T cells and IL-17-secreting T cells was diminished. PDT treatment in OLP leads to lesion reduction and improvement of QOL, and induces local and systemic anti-inflammatory effects. The study identifies PDT as a novel therapeutic option in OLP.

Targeted metabolomics of pellicle and saliva in children with different caries activity

Pellicle is the initial proteinaceous layer that is formed almost instantaneously on all solid surfaces in the oral cavity. It is of essential relevance for any interactions and metabolism on the tooth surface. Up to now, there is no information on the metabolome of this structure. Accordingly, the present study aims to characterise the metabolomic profile of in-situ pellicle in children with different caries activity for the first time in comparison to saliva. Small molecules such as carbohydrates, amino acids, organic acids, and fatty acids, putatively involved in the formation of caries were quantified using mass spectrometry (MS)-based techniques, such as (stable isotope dilution analysis)-ultra-performance liquid chromatography-tandem MS and gas chromatography/electron ionisation-MS. Pellicle and corresponding saliva samples were collected from caries-active, caries-free and caries-rehabilitated 4- to 6-year-old children. The most abundant analytes in pellicle were acetic acid (1.2-10.5 nmol/cm2), propionic acid (0.1-8.5 nmol/cm2), glycine (0.7-3.5 nmol/cm2), serine (0.08-2.3 nmol/cm2), galactose (galactose + mannose; 0.035-0.078 nmol/cm2), lactose (0.002-0.086 nmol/cm2), glucose (0.018-0.953 nmol/cm2), palmitic acid (0.26-2.03 nmol/cm2), and stearic acid (0.34-1.81 nmol/cm2). Significant differences depending on caries activity were detected neither in saliva nor in the corresponding pellicle samples.

Lipidomic profiling of non-mineralized dental plaque and biofilm by untargeted UHPLC-QTOF-MS/MS and SWATH acquisition

Dental plaque is a structurally organized biofilm which consists of diverse microbial colonies and extracellular matrix. Its composition may change when pathogenic microorganisms become dominating. Therefore, dental biofilm or plaque has been frequently investigated in the context of oral health and disease. Furthermore, its potential as an alternative matrix for analytical purposes has also been recognized in other disciplines like archeology, food sciences, and forensics. Thus, a careful in-depth characterization of dental plaque is worthwhile. Most of the conducted studies focused on the screening of microbial populations in dental plaque. Their lipid membranes, on the other hand, may significantly impact substance (metabolite) exchange within microbial colonies as well as xenobiotics uptake and incorporation into teeth. Under this umbrella, a comprehensive lipidomic profiling for determination of lipid compositions of in vivo dental plaque samples and of in vitro cultivated biofilm as surrogate matrix to be used for analytical purposes has been performed in this work. An untargeted lipidomics workflow utilizing a ultra-high-performance liquid chromatography (UHPLC)-quadrupole-time-of-flight (QTOF) platform together with comprehensive SWATH (sequential window acquisition of all theoretical fragment ion mass spectra) acquisition and compatible software (MS-DIAL) that comprises a vast lipid library has been adopted to establish an extensive lipidomic fingerprint of dental plaque. The main lipid components in dental plaque were identified as triacylglycerols, followed by cholesterol, cholesteryl esters as well as diacylglycerols, and various phospholipid classes. In vivo plaque is a rare matrix which is usually available in very low amounts. When higher quantities for specific research assays are required, efficient ways to produce an appropriate surrogate matrix are mandatory. A potential surrogate matrix substituting dental plaque was prepared by cultivation of in vitro biofilm from saliva and similarities and differences in the lipidomics profile to in vivo plaque were mapped by statistical evaluation post-analysis. It was discovered that most lipid classes were highly elevated in the in vitro biofilm samples, in particular diacylglycerols, phosphatidylglycerols, and phosphatidylethanolamines (PEs). Furthermore, an overall shift from even-chain lipid species to odd-chain lipids was observed in the cultivated biofilms. On the other hand, even-chain phosphatidylcholines (PCs), lysoPCs, cholesteryl esters, and cholesterol-sulfate were shown to be specifically increased in plaque samples.

Shockwave Therapy Efficiently Cures Multispecies Chronic Periodontitis in a Humanized Rat Model

Biofilms are ubiquitous in nature and are invariably associated with health and diseases of all living beings. Periodontal diseases & dental caries are the most prevalent conditions in which biofilm has established as a primary causative factor. Managing poly-microbial biofilm is the mainstay of periodontal therapy. Plethora of antimicrobials have been used till date to combat biofilm, but the emergence of antibiotic tolerance and resistance in biofilms is a major cause of concern. Apart from use of antimicrobials, various anti-biofilm strategies have evolved which include the use of mechanical, and chemical means to disrupt biofilms. However, none of these approaches have led to desired or optimal biofilm control and hence search for novel approach continues. Shockwaves are used in medical practice for various therapeutic purposes and in local drug delivery, gene therapy, wound healing & regeneration. With this background, a study was designed with an attempt to explore the possibility of using the shockwave for their effect on multispecies oral biofilm development from subgingival plaque samples obtained from chronic periodontitis patients. Plaque samples from 25 patients were used to derive multispecies biofilm which were used to check the efficacy of shockwaves and antibacterial efficacy of four clinically relevant antimicrobials. Biofilms were analyzed by scanning electron microscope; atomic force microscope and their biomass was quantitated by crystal violet staining. Further, a humanized rat model of periodontitis was developed. Patient derived plaque was used to establish periodontitis in healthy rats. The model was validated by performing colony forming unit (CFU) analysis of the infected tissue. The animals were subjected to low intensity shockwaves using a hand-held shockwave generator at the site of infection. Shockwave treatment was done with or without antimicrobial application. The animals were monitored for clearance of infection and for mortality. The results show that shockwave treatment in combination with antimicrobials is significantly effective in clearing a multispecies biofilm. This also brings out the possibility of application of shockwaves in the management of oral biofilms either alone or in combination with established antimicrobial agents. With further research, safety profile validation and clinical trials, shockwaves can be an effective, novel approach in management of biofilm associated periodontal disease.

Effects of Norspermidine on Dual-Species Biofilms Composed of Streptococcus mutans and Streptococcus sanguinis

The present study aimed at investigating the influence of norspermidine on the formation of dual-species biofilms composed of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Crystal violet assay was conducted to assess the formation of single-species biofilms of S. mutans and S. sanguinis, and the growth curve was carefully observed to monitor the growth of these two species of bacteria. Fluorescence in situ hybridization (FISH) and MTT array were used to analyze the composition and metabolic activity of the dual-species biofilms, respectively. Extracellular polysaccharides (EPS)/bacteria staining, anthrone method, and scanning electron microscopy (SEM) imaging were conducted to study the synthesis of EPS by dual-species biofilms. Lactic acid assay and pH were measured to detect dual-species biofilm acid production. We found that norspermidine had different effects on S. mutans and S. sanguinis including their growth and biofilm formation. Norspermidine regulated the composition of the dual-species biofilms, decreased the ratio of S. mutans in dual-species biofilms, and reduced the metabolic activity, EPS synthesis, and acid production of dual-species biofilms. Norspermidine regulated dual-species biofilms in an ecological way, suggesting that it may be a potent reagent for controlling dental biofilms and managing dental caries.

Evidence-based strategy for dental biofilms: Current evidence of mouthwashes on dental biofilm and gingivitis

Therapeutic mouthwash (MW) is an adjunctive tool along with a regular oral hygiene routine of daily tooth brushing and daily flossing. Previous systematic reviews have demonstrated that it is effective against dental biofilm and gingival inflammation, for prevention of dental caries, and for managing one's bad breath condition according to the active ingredients. MWs prevent the microorganisms from bacterial adhesion that corresponds to the initial step in biofilm formation. This review summarized the current state of evidence such as anti-biofilm, anti-gingivitis and cariostatic properties of MWs by evaluating systematic reviews from the past six years. The anti-biofilm property has been proven to be effective, with strong evidence of three main clinical efficacies. The most commonly studied active agent was chlorhexidine gluconate (CHX), followed by essential oil (EO) and cetylpyridinium chloride. All the systematic reviews are in complete agreement that CHX and EO provide statistically significant improvements in terms of plaque and gingival indices. These effects have held up over the years as the number of studies has increased. While the use of fluoride MW is proven to be effective in improving the oral health of both children and adults, the quality of evidence is still regarded as low.

The bactericidal effect of an atmospheric-pressure plasma jet on Porphyromonas gingivalis biofilms on sandblasted and acid-etched titanium discs

Purpose

Direct application of atmospheric-pressure plasma jets (APPJs) has been established as an effective method of microbial decontamination. This study aimed to investigate the bactericidal effect of direct application of an APPJ using helium gas (He-APPJ) on Porphyromonas gingivalis biofilms on sandblasted and acid-etched (SLA) titanium discs.

Methods

On the SLA discs covered by P. gingivalis biofilms, an APPJ with helium (He) as a discharge gas was applied at 3 different time intervals (0, 3, and 5 minutes). To evaluate the effect of the plasma itself, the He gas-only group was used as the control group. The bactericidal effect of the He-APPJ was determined by the number of colony-forming units. Bacterial viability was observed by confocal laser scanning microscopy (CLSM), and bacterial morphology was examined by scanning electron microscopy (SEM).

Results

As the plasma treatment time increased, the amount of P. gingivalis decreased, and the difference was statistically significant. In the SEM images, compared to the control group, the bacterial biofilm structure on SLA discs treated by the He-APPJ for more than 3 minutes was destroyed. In addition, the CLSM images showed consistent results. Even in sites distant from the area of direct He-APPJ exposure, decontamination effects were observed in both SEM and CLSM images.

Conclusions

He-APPJ application was effective in removing P. gingivalis biofilm on SLA titanium discs in an in vitro experiment.

Comparative clinical efficacy of three toothpastes in the control of supragingival calculus formation

OBJECTIVES

The purpose of this double-blind, parallel clinical study was to assess clinical efficacy in supragingival calculus formation reduction using Abhaibhubejhr Herbal Toothpaste compared to Colgate Total and Colgate Cavity Protection toothpastes.

MATERIALS AND METHODS

A total of 150 subjects participated in the pretest phase. All subjects were given oral soft/hard tissue evaluation, calculus examination using Volpe-Manhold calculus, and whole mouth oral prophylaxis. They received noncalculus control fluoride toothpaste and a soft-bristled toothbrush to brush for 1 min two times daily for 8 weeks. After which, subjects were given a test phase oral soft/hard tissue evaluation and calculus examination and were randomized into one of the three toothpaste groups. All subjects in the test phase received a whole mouth oral prophylaxis and were given their assigned toothpaste and a soft-bristled toothbrush to brush for 1 min two times a day for 12 weeks. Thereafter, subjects were assessed for their oral soft/hard tissue and calculus formation.

RESULTS

Mean Volpe-Manhold calculus index scores for the Cavity Protection, Abhaibhubejhr, and Total toothpaste groups were 0.78, 0.62, and 0.48, respectively, at the 12-week test phase evaluation. Abhaibhubejhr and Total toothpaste groups show 20.51% and 38.46% significantly less calculus formation than the Cavity Protection toothpaste group (P < 0.05). Total toothpaste group also show 22.58% significantly less calculus formation than the Abhaibhubejhr toothpaste group (P < 0.05).

CONCLUSION

The use of Colgate Total toothpaste over a 12-week period was clinically more effective than either Abhaibhubejhr or Colgate Cavity Protection toothpastes in controlling supragingival calculus formation.

Effect of nicotine on biofilm formation of Streptococcus mutans isolates from smoking and non-smoking subjects

Objectives: To investigate effects of nicotine on biofilm formation of Streptococcus mutans isolates from oral washes of smoker and non-smoker human subjects. Materials and methods: This study was conducted using 60 S. mutans isolates with three S. mutans isolates collected from oral washes of ten smoking subjects and ten from non-smoking subjects. Biofilm was formed by culturing each S. mutans strain (10 μl) in 190 μl of TSB supplemented with 1% sucrose (TSBS) containing 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0, and 32.0 mg/ml of nicotine for 24 h in 5% CO2 at 37°C in 96 well microtiter plates. The absorbance values of biofilm were measured at 490 nm in a microplate spectrophotometer. Results: There was a significant effect (p-value < 0.05) of nicotine concentrations and smoking on the growth of biofilm, planktonic cells, and total absorbance, for all strains of S. mutans. Isolates from smokers had significantly more biofilm at 0-16 mg/ml of nicotine compared to those from non-smokers (p-value < 0.0001). Conclusion: S. mutans smoker isolates are more affected by high nicotine concentrations than non-smoker isolates. Clinical Relevance: The use of nicotine products increases the growth of S. mutans and may place tobacco users at risk for dental decay.

Gene expression of Porphyromonas gingivalis ATCC 33277 when growing in an in vitro multispecies biofilm

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis, an oral microorganism residing in the subgingival biofilm, may exert diverse pathogenicity depending on the presence of specific virulence factors, but its gene expression has not been completely established. This investigation aims to compare the transcriptomic profile of this pathogen when growing within an in vitro multispecies biofilm or in a planktonic state.

MATERIALS AND METHODS

P. gingivalis ATCC 33277 was grown in anaerobiosis within multi-well culture plates at 37°C under two conditions: (a) planktonic samples (no hydroxyapatite discs) or (b) within a multispecies-biofilm containing Streptococcus oralis, Actinomyces naeslundii, Veillonella parvula, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans deposited on hydroxyapatite discs. Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) combined with Fluorescence In Situ Hybridization (FISH) were used to verify the formation of the biofilm and the presence of P. gingivalis. Total RNA was extracted from both the multispecies biofilm and planktonic samples, then purified and, with the use of a microarray, its differential gene expression was analyzed. A linear model was used for determining the differentially expressed genes using a filtering criterion of two-fold change (up or down) and a significance p-value of <0.05. Differential expression was confirmed by Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR).

RESULTS

SEM verified the development of the multispecies biofilm and FISH confirmed the incorporation of P. gingivalis. The microarray demonstrated that, when growing within the multispecies biofilm, 19.1% of P. gingivalis genes were significantly and differentially expressed (165 genes were up-regulated and 200 down-regulated), compared with planktonic growth. These genes were mainly involved in functions related to the oxidative stress, cell envelope, transposons and metabolism. The results of the microarray were confirmed by RT-qPCR.

CONCLUSION

Significant transcriptional changes occurred in P. gingivalis when growing in a multispecies biofilm compared to planktonic state.

Ruthenium Chloride-Induced Oxidative Cyclization of Trans-Resveratrol to (±)-ε-Viniferin and Antimicrobial and Antibiofilm Activity Against Streptococcus pneumoniae

Polyphenol ε-viniferin (2) is a protective phytochemical found in several plant families. Here, we report a simple and effective method for the synthesis of (±)-ε-viniferin (2) as major product and (±)-(E)-ω-viniferin (3) as a minor product. Synthesized viniferin compounds and standard viniferin were analyzed for antibacterial and antibiofilm activity against Gram-positive bacteria Streptococcus pneumoniae. The minimum inhibitory concentrations (MICs) of (±)-ε-viniferin (2) and standard viniferin were 20 µm. However, the MICs of (±)-(E)-ω-viniferin (3) and compound 8 were 40 µm. Although viniferin significantly (p < 0.05) reduced pre-established in vitro biofilms and killed bacteria within the biofilm, it was unable to prevent biofilm formation at sub-MIC concentrations. The time kill experiment revealed that viniferin killed bacteria and reduced 2.8 log10 bacteria at 2 × MIC concentration after 24 h. Scanning electron microscope (SEM) analysis and live/dead biofilm staining of pre-established biofilms revealed that viniferin treatment disrupts membrane integrity of biofilm bacteria. Crystal violet absorption, total protein, and DNA and RNA release revealed that viniferin alters bacterial cell permeability, eventually killing bacteria.

Biofilm formation on polyetheretherketone and titanium surfaces

Objective

Polyetheretherketone (PEEK) is a polymer used in devices in orthopedic and dental rehabilitation. The aim of this in vitro study was to compare biofilm formation by a range of important oral bacterial species on PEEK, blasted PEEK, commercially pure titanium (cp-Ti), and titanium-6 aluminium-4 vanadium (Ti6Al4V).

Material and methods

Coin-shaped samples were manufactured, and the surfaces were characterized using optical interferometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and contact angle measurements. Bacterial species of Streptococcus sanguinis, Streptococcus oralis, Enterococcus faecalis, and Streptococcus gordonii were cultured on the four material surfaces for varying amounts of time. Biofilms were quantified following staining with crystal violet.

Results

Roughness and contact angle results showed blasted PEEK > PEEK > cp-Ti = Ti6Al4V. There was increased biofilm formation on blasted PEEK by S. sanguinis, S. oralis, and S. gordonii, whereas the bacterial adhesion was similar on PEEK, cp-Ti, and Ti6Al4V. The bacterial growth of E. faecalis was significantly higher on cp-Ti compared with the other three groups.

Conclusion

The results, taking into consideration the biofilm formation, suggest that PEEK should perform as well as cp-Ti or TiAl6V4 when used as a dental restorative material.

Fusobacterium Species and Subspecies Differentially Affect the Composition and Architecture of Supra- and Subgingival Biofilms Models

Fusobacteria are common obligately anaerobic Gram-negative bacteria of the oral cavity that may act as a bridge between early and late colonizing bacteria in dental plaque and have a role in oral and extra-oral infections. Fusobacterium nucleatum has a crucial role in oral biofilm structure and ecology, as revealed in experimental and clinical biofilm models. The aim of this study was to investigate the impact of various Fusobacterium species on in vitro biofilm formation and structure in three different oral biofilm models namely a supragingival, a supragingival “feeding”, and a subgingival biofilm model. The standard six-species supragingival and “feeding” biofilm models employed contained Actinomyces oris, Candida albicans, Streptococcus mutans, Streptococcus oralis, Veillonella dispar, and Fusobacterium sp. The subgingival biofilm model contained 10 species (A. oris, Campylobacter rectus, F. nucleatum ssp. nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Streptococcus anginosus, S. oralis, Tannerella forsythia, Treponema denticola, and V. dispar). Six different Fusobacterium species or subspecies, respectively, were tested namely F. nucleatum ssp. fusiforme, F. nucleatum ssp. nucleatum, F. nucleatum ssp. polymorphum, F. nucleatum ssp. vincentii, F. naviforme, and F. periodonticum). Biofilms were grown anaerobically on hydroxyapatite disks in 24-well culture dishes. After 64 h, biofilms were either harvested and quantified by culture analysis or proceeded to fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM). All Fusobacterium species tested established well in the biofilms, with CFUs ranging from 1.4E+04 (F. nucleatum ssp. fusiforme) to 5.6E+06 (F. nucleatum ssp. nucleatum). The presence of specific Fusobacterium sp./ssp. induced a significant decrease in C. albicans levels in the supragingival model and in V. dispar levels in the “feeding” supragingival model. In the subgingival model, the counts of A. oris, S. oralis, P. intermedia, P. gingivalis, and C. rectus significantly decreased in the presence of specific Fusobacterium sp./ssp. Collectively, this study showed variations in the growing capacities of different fusobacteria within biofilms, affecting the growth of surrounding species and potentially the biofilm architecture. Hence, clinical or experimental studies need to differentiate between Fusobacterium sp./ssp., as their biological properties may well vary.

Host modulation therapy using anti-inflammatory and antioxidant agents in periodontitis: A review to a clinical translation

OBJECTIVE

To highlight the shifting paradigm of periodontitis, describe mechanism of periodontal bone destruction, and propose an updated host modulation therapy (HMT) strategy. To add further clinical relevance, related studies investigating the efficacy of several HMT agents in periodontitis will be discussed.

DESIGN

Literature searches were conducted from articles published in PubMed using keywords "periodontal disease AND periodontitis AND host modulation therapy AND anti-inflammatory AND antioxidant", and then the findings were comprehensively summarized and elaborated.

RESULT

Accumulating evidence indicates that periodontitis is no longer defined solely as a pathogen-induced disease; rather, it is now recognized as a consequence of uncontrolled immune response and oxidative stress leading to periodontal tissue damage. Although periodontopathic bacteria initiate the disease, inflammation and oxidative stress were reported to be the main causes for the severity of tissue destruction. Thus, since the concept of periodontitis has shifted, our approach to its management needs to be adjusted to accommodate the latest paradigm. Nowadays, the modulation of inflammation and oxidative stress is considered a target of HMT. HMT agents, such as probiotics, anti-inflammatory drugs, anti-chemokines, lipid mediators, and bio-active fatty acids, have been extensively investigated for their remarkable functions in modulating the immune response and providing antioxidant effects.

CONCLUSION

Findings from in vitro, in vivo, and human studies frequently demonstrate positive association by the administration of HMT in periodontitis. HMT strategy targeted on anti-inflammatory and antioxidant in periodontitis might serve as an excellent therapeutic approach to reach the level of clinical benefit.

Detection of dental plaque and its potential pathogenicity using quantitative light-induced fluorescence

Quantitative light-induced fluorescence (QLF) technology can detect some dental plaque as red fluorescence. This in vivo study aimed to identify the microbial characteristics of red fluorescent (RF) dental plaque using 16S rRNA gene sequencing and evaluate the correlations between RF plaque and the clinical symptoms of dental diseases. Paired supragingival plaque samples collected from each 10 subjects and consisted of RF and non-RF dental plaques as observed by QLF technology using a 405 nm blue light source for excitation. The characteristics of the bacterial communities in the RF and non-RF plaque samples were compared by sequencing analysis. An increase in microbial diversity was observed in RF plaque compared with the non-RF plaque. There were significant differences in the community compositions between the 2 types of dental plaque. Periodontopathic bacteria were significantly more abundant in the RF plaque than non-RF plaque. The fluorescence intensity of RF plaque was significantly related to the proportion of the periodontopathic bacterial community and the presence of gingival inflammation. In conclusion, the plaque red fluorescence is associated with changes in the microbial composition and enrichment of periodontopathic pathogens, which suggests that RF plaque detected by QLF technology could be used as a risk indicator for gingival inflammation.

Comparison of the Photosensitivity of Biofilms of Different Genera of Cariogenic Bacteria in Tooth Slices

This study compared the outcome of photosensitization on the viability of four different cariogens in planktonic form as well as biofilms in human dentine. Photodynamic therapy was carried out with a gallium aluminium arsenide laser (670 nm wavelength) using Toluidine blue O (TBO) as the photosensitizer. Cariogenic bacteria (Streptococcus mutans, Lactobacillus casei, Streptococcus salivarius and Actinomyces viscosus) were exposed to TBO and then to the laser for 1 minute in planktonic suspension. Then, tooth slices previously incubated for 24 hours with broth cultures of broth culture of the four cariogenic organisms were exposed to antimicrobial photosensitization. The control samples consisted of planktonic and sessile cells that were exposed to TBO alone, laser alone and the bacterial cells that were not treated with TBO or laser. The results showed significant reductions in the viability of S. mutans, L. casei and A. viscosus in both planktonic form (to 13%, 30%, and 55%, respectively) and sessile form hosted in dentinal tubules (to 19%, 13% and 52%, respectively), relative to the controls. S. salivarius was the least affected in planktonic (94% viability) and sessile form (86% viability). In conclusion, sensitivity to photosensitization is species-dependent and sessile biofilm cells are affected to the same extent as their planktonic counterparts.

PgFur participates differentially in expression of virulence factors in more virulent A7436 and less virulent ATCC 33277 Porphyromonas gingivalis strains

Background

Porphyromonas gingivalis is considered a keystone pathogen responsible for chronic periodontitis. Although several virulence factors produced by this bacterium are quite well characterized, very little is known about regulatory mechanisms that allow different strains of P. gingivalis to efficiently survive in the hostile environment of the oral cavity, a typical habitat characterized by low iron and heme concentrations. The aim of this study was to characterize P. gingivalis Fur homolog (PgFur) in terms of its role in production of virulence factors in more (A7436) and less (ATCC 33277) virulent strains.

Results

Expression of a pgfur depends on the growth phase and iron/heme concentration. To better understand the role played by the PgFur protein in P. gingivalis virulence under low- and high-iron/heme conditions, a pgfur-deficient ATCC 33277 strain (TO16) was constructed and its phenotype compared with that of a pgfur A7436-derived mutant strain (TO6). In contrast to the TO6 strain, the TO16 strain did not differ in the growth rate and hemolytic activity compared with the ATCC 33277 strain. However, both mutant strains were more sensitive to oxidative stress and they demonstrated changes in the production of lysine- (Kgp) and arginine-specific (Rgp) gingipains. In contrast to the wild-type strains, TO6 and TO16 mutant strains produced larger amounts of HmuY protein under high iron/heme conditions. We also demonstrated differences in production of glycoconjugates between the A7436 and ATCC 33277 strains and we found evidence that PgFur protein might regulate glycosylation process. Moreover, we revealed that PgFur protein plays a role in interactions with other periodontopathogens and is important for P. gingivalis infection of THP-1-derived macrophages and survival inside the cells. Deletion of the pgfur gene influences expression of many transcription factors, including two not yet characterized transcription factors from the Crp/Fnr family. We also observed lower expression of the CRISPR/Cas genes.

Conclusions

We show here for the first time that inactivation of the pgfur gene exerts a different influence on the phenotype of the A7436 and ATCC 33277 strains. Our findings further support the hypothesis that PgFur regulates expression of genes encoding surface virulence factors and/or genes involved in their maturation.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1511-x) contains supplementary material, which is available to authorized users.

In vitro Evaluation of Photodynamic Effects Against Biofilms of Dermatophytes Involved in Onychomycosis

Dermatophytes are the most common cause of onychomycosis, counting for 90% fungal nail infection. Although dermatophyte pathogens are normally susceptible to antifungal agents, onychomycosis often results in refractory chronic disease, and the formation of biofilms frequently underlines the inadequate responses and resistance to standard antifungal treatment. Numerous in vitro and in vivo antimicrobial photodynamic therapy (aPDT) studies have shown biofilm eradication or substantial reduction, however, such investigation has not yet been expanded to the biofilms of dermatophytes involved in onychomycosis. To shed a light on the potential application of aPDT in the clinic management of onychomycosis, in particular with the manifestation of dermatophytoma, we investigated photodynamic effects on the viabilities and the drug susceptibilities of the biofilm of dermatophytes in vitro. Here, methylene blue at the concentration of 8, 16, and 32 μg/ml applied as photosensitizing agent and LED (635 ± 10 nm, 60 J/cm²) as light source were employed against six strains of Trichophyton rubrum, ten strains of Trichophyton mentagrophytes and three strains of Microsporum gypseum isolated from clinical specimens. Our results indicated highly efficient photodynamic inhibition, exhibiting CFU (colony forming unit) reduction up to 4.6 log₁₀, 4.3 log₁₀, and 4.7 log₁₀ against the biofilms formed by T. rubrum, T. mentagrophytes, and M. gypseum, respectively. Subjected biofilms displayed considerable decreases in SMICs (sessile minimum inhibitory concentrations) to multiple antifungal agents when compared with untreated groups, indicating the biofilms of dermatophytes became more susceptible to conventional antifungal drugs after aPDT. Additionally, the obliteration of biofilm after aPDT could be observed as shattered and ruptured structures being evident in SEM (Scanning Electron Microscopy) images. These findings suggest that aPDT is an attractive alternative treatment holding great promise for combating recalcitrant onychomycosis associated with the biofilm formation.

Porphyromonas gingivalis and digestive system cancers

Porphyromonas gingivalis (P. gingivalis) is an anaerobic gram-negative bacterium that colonizes in the epithelium and has been strongly associated with periodontal disease. Recently, various degrees of associations between P. gingivalis and digestive system cancers, including oral squamous cell carcinoma in the oral cavity, oesophageal squamous carcinoma in the digestive tract, and pancreatic cancer in pancreatic tissues, have been displayed in multiple clinical and experimental studies. Since P. gingivalis has a strong association with periodontal diseases, not only the relationships between P. gingivalis and digestive system tumours but also the effects induced by periodontal diseases on cancers are well-illustrated in this review. In addition, the prevention and possible treatments for these digestive system tumours induced by P. gingivalis infection are also included in this review. At the end, we also highlighted the possible mechanisms of cancers caused by P. gingivalis. One important carcinogenic effect of P. gingivalis is inhibiting the apoptosis of epithelial cells, which also plays an intrinsic role in protecting cancerous cells. Some signalling pathways activated by P. gingivalis are involved in cell apoptosis, tumourigenesis, immune evasion and cell invasion of tumour cells. In addition, metabolism of potentially carcinogenic substances caused by P. gingivalis is also one of the connections between this bacterium and cancers.

Making sense of medieval mouths: Investigating sex differences of dental pathological lesions in a late medieval Italian community

OBJECTIVES

Bioarchaeological investigations of sex-based differences in the prevalence of dental pathological lesions, particularly caries, have drawn considerable attention, and out of this work, two dominant models have emerged. Traditionally, the first model interprets sex-related patterns in caries as a product of gendered differences in diet. A more recent model interprets a generally higher propensity for caries prevalence in females in light of reproductive ecology. To test the hypothesis that females have higher risk of caries in accordance with reproductive ecology, we examined and analyzed caries prevalence and other potentially synergistic oral pathological lesions in a late medieval (A.D. 1300-1500) Italian archaeological sample.

MATERIALS AND METHODS

We examined sex- and age-related prevalence in caries and other oral pathological lesions in a late medieval Italian skeletal assemblage excavated from Villamagna consisting of 38 females and 37 males (n = 1,534 teeth). We examined age- and sex-related patterns in six dental traits: antemortem tooth loss, caries, calculus, periapical inflammation, tooth wear, and periodontitis.

RESULTS

Significant age-related increases in antemortem tooth loss, caries, calculus, and tooth wear were observed in both males and females. However, there was a lack of expected sex differences in oral pathological lesions, with instead older males exhibiting significantly more antemortem tooth loss and corrected caries than females.

DISCUSSION

Results are discussed in relation to the ethnohistoric context of medieval rural dietary practices as well as biomedical salivary literature, which suggest that dietary changes throughout the life course may have facilitated trade-offs that buffered females from higher rates of dental pathological lesions.

[The need for specific toothpaste in patients receiving occlusal splint therapy]

The aim of the study is to determine the optimal properties of toothpaste for patients receiving occlusal splint therapy. The study comprised 50 people with full dentition (21 male and 29 female) divided into two groups. The main group included 25 individuals receiving occlusal splint therapy while 25 people who did not use splints were recruited as controls. Each group was further divided into two subgroups according to toothpaste used for regular oral hygiene. Examinations were performed after 14, 30 and 90 days using hygienic indices of NCI-C and Turesky and PMA gingival index. The combined effect of toothpaste was estimated by the change in the volume and acidity of saliva. The results suggest a better level of hygiene in the group I, which used toothpaste with sodium bicarbonate and silica.

Streptococcus mutans yidC1 and yidC2 Impact Cell Envelope Biogenesis, the Biofilm Matrix, and Biofilm Biophysical Properties

YidC proteins are membrane-localized chaperone insertases that are universally conserved in all bacteria and are traditionally studied in the context of membrane protein insertion and assembly. Both YidC paralogs of the cariogenic pathogen Streptococcus mutans are required for proper envelope biogenesis and full virulence, indicating that these proteins may also contribute to optimal biofilm formation in streptococci. Here, we show that the deletion of either yidC results in changes to the structure and physical properties of the EPS matrix produced by S. mutans , ultimately impairing optimal biofilm development, diminishing its mechanical stability, and facilitating its removal. Importantly, the universal conservation of bacterial yidC orthologs, combined with our findings, provide a rationale for YidC as a possible drug target for antibiofilm therapies.

Antimicrobial effect of herbal extract of Acacia arabica with triphala on the biofilm forming cariogenic microorganisms

Background

Dental caries is a biofilm-related infectious disease with a multifactorial etiology, over five billion inhabitants have affected worldwide due to this disease.

Objective

Antimicrobial efficacy of a mixed herbal powder extract (MHPE) against cariogenic microorganisms was investigated.

Materials and methods

MIC, MBC, kinetics of killing, biofilm disruption and anticaries effect of MHPE were determined. For biofilm disruption, biofilms of Streptococcus mutans, Lactobacillus casei, Actinomyces viscosus and Candida albicans were treated with MHPE for 30 min and attached cells were quantified after staining. For live/dead staining biofilm assay, S. mutans biofilm treated with MHPE for 1min, 5min and 1 h was examined with confocal laser scanning system after live/dead staining. Efficacy was experimented by structural quality using Scanning Electron Microscope (SEM). Anticaries effect was determined by formation of caries-like lesion in continuous flow biofilm model.

Results

MHPE exhibited inhibition zones ranging from 12.5 to 24.0 mm. The highest inhibition zone was recorded at concentration of 50 μg/ml. MIC for S. mutans was between 12.23 and 36.7 μg/ml, while the MBC values ranged from 36.7 to 110.65 μg/ml. Inhibitory concentration of MHPE was three fold higher than CHLX. Significant reduction of cell count (49–95%) was observed with increasing time and higher concentration. Percentage biofilm reduction compare with negative control was 96.9% (A. viscosus), 94% (C. albicans), 99.8% (L. casei) and 91.7% (S. mutans). For MHPE-treated biofilm, live/dead staining demonstrated significant (p < 0.05) higher in deceased red fluorescence areas in all kinetics points from 53.6% (1min) to 85% (1h). SEM confirmed the damage in the outer layers of S. mutans. MHPE has components with effective antibacterial activity against caries-inducing microorganisms.

Conclusion

The anti-adherence and anti-biofilm effect as well as the faster killing activity suggests that MHPE formula has effective antibacterial activity and could be a useful source of anti-cariogenic agents in near future.

Randomized Controlled Clinical Study to Determine the Oral and Dermal Tolerability of an Experimental Denture Wipe

Purpose

To evaluate oral and dermal tolerance following use and user acceptability of an experimental denture‐cleansing wipe. An exploratory objective was to develop a method to assess denture wipe effectiveness in removing debris from denture surfaces.

Materials and Methods

This was a single‐center, randomized, controlled, parallel‐group, examiner‐blind study in participants with ≥1 full/partial denture. Participants were randomized to clean their dentures with the denture wipe (n = 76) or water (n = 76) up to 4 times per day for 14 days. Tolerability was assessed by treatment‐emergent adverse events (TEAEs), oral soft tissue examination, and lead hand dermatological assessment. Acceptability was assessed by questionnaire. The feasibility of a methodology to assess the efficacy of the wipe at removing food particles was also evaluated through determination of the mass of chewed peanut particles that the wipe removed after a single use (n = 31).

Results

The proportion of participants experiencing oral TEAEs by day 14 was 0.039% with the denture wipe (lip injury [n = 1], mouth injury [n = 2]) and 0.013% with the water rinse (coated tongue [n = 1]). There were no dermal TEAEs and no TEAE‐related study withdrawals. Skin irritation scores with the denture wipe remained unchanged from baseline. Comparing before vs. after cleaning with the denture wipe, a higher proportion of participants rated their dentures as feeling extremely/very fresh (28.9% pre‐/85.5% post‐cleaning), feeling extremely/very clean (34.2%/86.8%) and looking extremely/very clean (43.5%/85.5%). More denture‐wipe group participants than water‐rinse group participants were extremely/very satisfied with the amount of debris removed from their dentures (88.1% vs 72.4%). The methodology used to assess the weight of peanut particles captured from the wipes/dentures appeared to be a feasible investigation technique.

Conclusions

The denture wipe was generally well‐tolerated and had good user acceptability. The methodology for assessing the mass of peanut particles removed by denture wipes was successful.

Sugar Substitutes: Mechanism, Availability, Current Use and Safety Concerns-An Update

BACKGROUND

Dental caries has continued to be the major oral disease in the past, as well as the present scenario. Cariogenic sugars in the presence of specific bacteria Streptococcus mutans over a period have been attributed as the major etiologic agent for dental caries. The association between sugar consumption and dental caries has been well documented.

AIM

Hence, the dental profession shares an interest in the search for safe, palatable sugar substitutes.

METHODS

Therefore, the use of a suitable sugar substitute can help in combating dental caries.

RESULTS

Out of the various sugar substitutes available, xylitol is the most widely used. It is available in various forms. It decreases the plaque formation, bacterial adherence and inhibits the growth of Mutans Streptococci.

CONCLUSION

This article provides a comprehensive review of the sugar substitutes, present-day availability, role in the prevention of dental caries and their safety concerns.

Historical and Contemporary Perspectives on the Microbiological Aspects of Endodontics

The microbiota of the oral cavity plays a significant role in pulpal and periapical diseases. Historically, 100 years ago little was known on microbiota, but after a century of investigations, only now can many of the intimate secrets of microbial growth, expansion, persistence, communal activities, and virulence be revealed. However, with the capabilities of the microbiota for mutation, quorum sensing, and information transference, researchers are hard-pressed to keep up with both the changes and challenges that an amazingly wide range of bacterial species pose for both the scientist and clinician. Fortunately, the development and expansion of a vast array of molecular biological investigative techniques have enabled dentistry and its associated medical fields to attempt to keep pace with the wide and fascinating world of oral microbiology.

Comparison of initial oral microbiomes of young adults with and without cavitated dentin caries lesions using an in situ biofilm model

Dental caries is caused by acids released from bacterial biofilms. However, the in vivo formation of initial biofilms in relation to caries remains largely unexplored. The aim of this study was to compare the oral microbiome during the initial phase of bacterial colonization for individuals with (CC) and without (NC) cavitated dentin caries lesions. Bovine enamel slabs on acrylic splints were worn by the volunteers (CC: 14, NC: 13) for in situ biofilm formation (2 h, 4 h, 8 h, 1 ml saliva as reference). Sequencing of the V1/V2 regions of the 16S rRNA gene was performed (MiSeq). The relative abundances of individual operational taxonomic units (OTUs) were compared between samples from the CC group and the NC group. Random forests models were furthermore trained to separate the groups. While the overall heterogeneity did not differ substantially between CC and NC individuals, several individual OTUs were found to have significantly different relative abundances. For the 8 h samples, most of the significant OTUs showed higher relative abundances in the CC group, while the majority of significant OTUs in the saliva samples were more abundant in the NC group. Furthermore, using OTU signatures enabled a separation between both groups, with area-under-the-curve (AUC) values of ~0.8. In summary, the results suggest that initial oral biofilms provide the potential to differentiate between CC and NC individuals.

Efficacy of red propolis hydro-alcoholic extract in controlling Streptococcus mutans biofilm build-up and dental enamel demineralization

OBJECTIVE

The efficacy of a red propolis hydro-alcoholic extract (RP) in controlling Streptococcus mutans biofilm colonization was evaluated. The effect of RP on dental demineralization was also investigated.

METHODS

Chemical composition was determined by High Performance Liquid Chromatography (HPLC). Minimum Inhibitory and Bactericidal Concentration (MIC and MBC, respectively) were investigated against Streptococcus mutans (ATCC 25175). The cytotoxic potential of 3% RP in oral fibroblasts was observed after 1 and 3 min. Bovine dental enamel blocks (N = 24) were used for S. mutans biofilm formation (48 h), simulating 'feast or famine' episodes. Blocks/biofilms were exposed 2×/day, for 3 days, to a cariogenic challenge with sucrose 10% (5 min) and treated (1 min) with: 0.85% saline solution (negative control), 0.12% Chlorhexidine (CHX, positive control for biofilm colonization), 0.05% Sodium Fluoride (NaF, positive control to avoid demineralization) and 3% RP. Biofilms were assessed for viability (CFU/mL), and to observe the concentration of soluble and insoluble extracellular polysaccharides (SEPS and IEPS). Dental demineralization was assessed by the percentage of surface hardness loss (%SHL) and through polarized light microscopy (PLM).

RESULTS

The RP presented 4.0 pH and ºBrix = 4.8. The p-coumaric acid (17.2 μg/mL) and luteolin (15.23 μg/mL) were the largest contents of phenolic acids and flavonoids, respectively. MIC and MBC of RP were 293 μg/mL and 1172 μg/mL, respectively. The 3% RP showed 43% of viably cells after 1 min. Lower number (p < 0.05) of viable bacteria (CFU/mL) was observed after CHX (1.8 × 105) followed by RP (1.8 × 107) treatments. The lowest concentration (μg/CFU) of SEPS (12.6) and IEPS (25.9) was observed in CHX (p < 0.05) followed by RP (17.1 and 54.3), and both differed from the negative control (34.4 and 63.9) (p < 0.05). Considering the %SHL, all groups differed statistically (p < 0.05) from the negative control (46.6%); but NaF (13.9%), CHX (20.1%) and RP (20.7%) did not differ among them (p > 0.05). After all treatments, suggestive areas of caries lesions were observed by PLM, which were lower for CHX and NaF.

CONCLUSION

The 3% RP reduced S. mutans colonization, decreased concentration of extracellular polysaccharides and reduced dental enamel demineralization.

Oral Biofilms: Development, Control, and Analysis

The oral cavity harbors hundreds of microbial species that are present either as planktonic cells or incorporated into biofilms. The majority of the oral microbes are commensal organisms. Those that are pathogenic microbes can result in oral infections, and at times can initiate systemic diseases. Biofilms that contain pathogens are challenging to control. Many conventional antimicrobials have proven to be ineffective. Recent advances in science and technology are providing new approaches for pathogen control and containment and methods to characterize biofilms. This perspective provides (1) a general understanding of biofilm development; (2) a description of emerging chemical and biological methods to control oral biofilms; and (3) an overview of high-throughput analytical approaches to analyze biofilms.

Multivariate optimization of a method for the determination of fatty acids in dental biofilm by GC-MS

AIM

Phospholipid fatty acid methyl ester (FAME) analysis offers a simple option additionally to 16S rRNA sequencing to characterize microbial communities and to monitor changes. A method was established for the characterization of dental plaque via FAME profiles.

METHODOLOGY

Fatty acids were determined as FAMEs (direct, acidic transesterification) and analyzed by GC-MS using an optimized temperature gradient. The transesterification reaction was optimized using a fractional factorial central composite face-centered design.

RESULTS

Optimal conditions for the transesterification in methanol/toluene: hydrochloric acid concentration 2% (w/v), reaction time 40 min, temperature 110 °C. Method validation showed satisfactory accuracy, precision and linearity.

CONCLUSION

The method provides a useful tool to characterize plaque via FAME profiles and was successfully applied to samples from ten subjects demonstrating its applicability.

Green Tea Polyphenol Epigallocatechin-3-Gallate-Stearate Inhibits the Growth of Streptococcus mutans: A Promising New Approach in Caries Prevention

Streptococcus mutans (S. mutans) is the main etiological bacteria present in the oral cavity that leads to dental caries. All of the S. mutans in the oral cavity form biofilms that adhere to the surfaces of teeth. Dental caries are infections facilitated by the development of biofilm. An esterified derivative of epigallocatechin-3-gallate (EGCG), epigallocatechin-3-gallate-stearate (EGCG-S), was used in this study to assess its ability to inhibit the growth and biofilm formation of S. mutans. The effect of EGCG-S on bacterial growth was evaluated with colony forming units (CFU) and log reduction; biofilm formation was qualitatively determined by Congo red assay, and quantitatively determined by crystal violet assay, fluorescence-based LIVE/DEAD assays to study the cell viability, and scanning electron microscopy (SEM) was used to evaluate the morphological changes. The results indicated that EGCG-S was able to completely inhibit growth and biofilm formation at concentrations of 250 µg/mL. Its effectiveness was also compared with a commonly prescribed mouthwash in the United States, chlorhexidine gluconate. EGCG-S was shown to be equally effective in reducing S. mutans growth as chlorhexidine gluconate. In conclusion, EGCG-S is potentially an anticariogenic agent by reducing bacterial presence in the oral cavity.

Antimicrobial effects of terpinen-4-ol against oral pathogens and its capacity for the modulation of gene expression

This study evaluated the antibacterial activity of terpinen-4-ol against Streptococcus mutans and Lactobacillus acidophilus and its influence on gbpA (S. mutans) and slpA (L. acidophilus) gene expression. As measured by XTT assay, the concentrations of terpinen-4-ol that effectively inhibited the biofilm were 0.24% and 0.95% for S. mutans and L. acidophilus, respectively. Confocal microscopy revealed the presence of a biofilm attached to the enamel and dentin block surfaces with significant terpinen-4-ol effects against these microorganisms. The expression of the gbpA and slpA genes involved in adherence and biofilm formation was investigated using RT-PCR. Expression of these genes decreased after 15 min with 0.24% and 0.95% terpinen-4-ol in S. mutans and L. acidophilus, respectively. These findings demonstrate the antimicrobial activity of terpinen-4-ol and its ability to modulate the expression of gbpA and slpA genes, emphasizing the therapeutic capacity of terpinen-4-ol as an alternative to inhibit adherence in biofilm.

[Oral and periodontal hygiene in orthodontic patients]

INTRODUCTION

Orthodontic appliances promote dental plaque retention and make tooth-brushing less easy. They result in both quantitative and qualitative changes in dental plaque, exposing orthodontic patients to dental caries and periodontal diseases.

MATERIALS AND METHODS

The authors explain the effects of orthodontic treatments on dental plaque and the occurrence of dental and periodontal problems; they emphasize the role of pathogenic bacteria and highlight the need for efficient (both individual and professional) control of dental plaque.

DISCUSSION

Therefore, orthodontists have to educate their patients on oral and periodontal hygiene in order to control this bacterial factor and to avoid the occurrence of dental and/or periodontal complications.

An Overview of Dental Adhesive Systems and the Dynamic Tooth-Adhesive Interface

From the conception of resin-enamel adhesion to today's contemporary dental adhesive systems, clinicians are no longer afraid of exploring the many advantages brought by adhesive restorative concepts. To maximize the performance of adhesive-based restorative procedures, practitioners must be familiar with the mechanism of adhesion, clinical indications, proper handling, the inherent limitations of the materials and the biological challenges. This review provides an overview of the current status of restorative dental adhesives, their mechanism of adhesion, mechanisms of degradation of dental adhesive interfaces, how to maximize performance, and future trends in adhesive dentistry.

Antimicrobial photodynamic therapy - what we know and what we don't

Considering increasing number of pathogens resistant towards commonly used antibiotics as well as antiseptics, there is a pressing need for antimicrobial approaches that are capable of inactivating pathogens efficiently without the risk of inducing resistances. In this regard, an alternative approach is the antimicrobial photodynamic therapy (aPDT). The antimicrobial effect of aPDT is based on the principle that visible light activates a per se non-toxic molecule, the so-called photosensitizer (PS), resulting in generation of reactive oxygen species that kill bacteria unselectively via an oxidative burst. During the last 10-20 years, there has been extensive in vitro research on novel PS as well as light sources, which is now to be translated into clinics. In this review, we aim to provide an overview about the history of aPDT, its fundamental photochemical and photophysical mechanisms as well as photosensitizers and light sources that are currently applied for aPDT in vitro. Furthermore, the potential of resistances towards aPDT is extensively discussed and implications for proper comparison of in vitro studies regarding aPDT as well as for potential application fields in clinical practice are given. Overall, this review shall provide an outlook on future research directions needed for successful translation of promising in vitro results in aPDT towards clinical practice.