Dental plaque formation

Exploring oral bacterial compositional network in two oral disease groups using a convergent approach of NGS-molecular diagnostics

BACKGROUND

Since most of the commonly known oral diseases are explained in link with balance of microbial community, an accurate bacterial taxonomy profiling for determining bacterial compositional network is essential. However, compared to intestinal microbiome, research data pool related to oral microbiome is small, and general 16S rRNA screening method has a taxonomy misclassification issue in confirming complex bacterial composition at the species level.

OBJECTIVE

Present study aimed to explore bacterial compositional networks at the species level within saliva of 39 oral disease patients (Dental Caries group: n = 26 and Periodontitis group: n = 13) through comparison with public Korean-specific healthy oral microbiome data.

METHODS

Here, we applied comprehensive molecular diagnostics based on qRT-PCR and Sanger sequencing methods to complement the technical limitations of NGS-based 16S V3-V4 amplicon sequencing technology.

RESULTS

As a result of microbiome profiling at the genus level, relative frequencies of many nitrate-reducing bacteria within each oral disease group were found to be significantly low compared to the healthy group. In addition, the molecular diagnostics-based bacterial identification method allowed the determination of the correct taxonomy of screened primary colonizers (Streptococcus and Actinomyces unclassification clusters) for each oral disease. Finally, as with the results of microbiome profiling at the genus level, many core-species classified within the saliva of each oral disease group were also related to nitrate-reduction, and it was estimated that various pathogens associated with each disease formed a bacterial network with the core-species.

CONCLUSION

Our study introduced a novel approach that can compensate for the difficulty of identifying an accurate bacterial compositional network at the species level due to unclear taxonomy classification by using the convergent approach of NGS-molecular diagnostics. Ultimately, we suggest that our experimental approach and results could be potential reference materials for researchers who intend to prevent oral disease by determining the correlation between oral health and bacterial compositional network according to the changes in the relative frequency for nitrate-reducing species.

Oral infection with periodontal pathogens induced chronic obstructive pulmonary disease-like lung changes in mice

BACKGROUND

Epidemiological studies have demonstrated that periodontitis is an independent risk factor for chronic obstructive pulmonary disease (COPD). However, the mechanism underlying the association between these two diseases remains unclear. The lung microbiota shares similarities with the oral microbiota, and there is growing evidence to suggest that the lung microbiome could play a role in the pathogenesis of COPD. This study aimed to investigate whether periodontal pathogens could contribute to the pathogenesis of COPD in a mouse model.

METHODS

We established mouse models with oral infection by typical periodontal pathogens, porphyromonas gingivalis (Pg group) or fusobacterium nucleatum (Fn group), over a three-month period. Mice that did not receive oral infection were set as the control group (C group). We assessed the level of alveolar bone resorption, lung function, and histological changes in the lungs of the mice. Additionally, we measured the levels of inflammatory factors and tissue damage associated factors in the lung tissues.

RESULTS

Lung function indices, including airway resistance, peak inspiratory/expiratory flow and expiratory flow-50%, were significantly reduced in the Fn group compared to the C group. Additionally, histological examination revealed an increased number of inflammatory cells and bullae formation in the lung tissue sections of the Fn group. Meanwhile, levels of inflammatory factors such as IL-1β, IL-6, IFN-γ, and TNF-α, as well as tissue damage associated factors like matrix metalloproteinase-8 and neutrophil elastase, were significantly elevated in the lung tissue of the Fn group in comparison to the C group. The Pg group also showed similar but milder lung changes compared to the Fn group. Pg or Fn could be detected in the lungs of both oral infected groups.

CONCLUSION

The results indicated that oral periodontal pathogens infection could induce COPD-like lung changes in mice, and they may play a biological role in the association between periodontitis and COPD.

Insights into the enigma of oral streptococci in carcinogenesis

SUMMARYThe genus Streptococcus consists of a taxonomically diverse group of Gram-positive bacteria that have earned significant scientific interest due to their physiological and pathogenic characteristics. Within the genus Streptococcus, viridans group streptococci (VGS) play a significant role in the oral ecosystem, constituting approximately 80% of the oral biofilm. Their primary role as pioneering colonizers in the oral cavity with multifaceted interactions like adherence, metabolic signaling, and quorum sensing contributes significantly to the complex dynamics of the oral biofilm, thus shaping oral health and disease outcomes. Perturbations in oral streptococci composition drive oral dysbiosis and therefore impact host-pathogen interactions, resulting in oral inflammation and representing VGS as an opportunistic pathogen. The association of oral streptococci in tumors across distant organs, spanning the esophagus, stomach, pancreas, and colon, illuminates a potential association between oral streptococci, inflammation, and tumorigenesis. This finding emphasizes the need for further investigations into the role of oral streptococci in mucosal homeostasis and their involvement in carcinogenesis. Hence, here, we review the significance of oral streptococci in biofilm dynamics and how the perturbation may impact mucosal immunopathogenesis in the context of cancer, with a vision of exploiting oral streptococci for cancer intervention and for the development of non-invasive cancer diagnosis.

An insight into the last 5-year patents on Porphyromonas gingivalis and Streptococcus mutans, the pivotal pathogens in the oral cavity

INTRODUCTION

The oral cavity harbors an extensive array of over 700 microorganisms, forming the most complex biome of the entire human body, with bacterial species being the most abundant. Oral diseases, e.g. periodontitis and caries, are strictly associated with bacterial dysbiosis. Porphyromonas gingivalis and Streptococcus mutans stand out among bacteria colonizing the oral cavity.

AREAS COVERED

After a brief overview of the bacterial populations in the oral cavity and their roles in regulating (flora) oral cavity or causing diseases like periodontal and cariogenic pathogens, we focused our attention on P. gingivalis and S. mutans, searching for the last-5-year patents dealing with the proposal of new strategies to fight their infections. Following the PRISMA protocol, we filtered the results and analyzed over 100 applied/granted patents, to provide an in-depth insight into this R&D scenario.

EXPERT OPINION

Several antibacterial proposals have been patented in this period, from both chemical - peptides and small molecules - and biological - probiotics and antibodies - sources, along with natural extracts, polymers, and drug delivery systems. Most of the inventors are from China and Korea and their studies also investigated anti-inflammatory and antioxidant effects, being beneficial to oral health through a prophylactic, protective, or curative effect.

Microbial Communities and Functional Genes in Periodontitis and Healthy Controls

BACKGROUND

Periodontitis is a chronic progressive disease and the leading cause of tooth loss in adults. Recent studies have shown the impact of oral microbial communities on systemic health and diseases such as cancer, atherosclerosis, rheumatoid arthritis, inflammatory bowel disease, diabetes, hypertension, and Alzheimer's disease. In previous case control studies investigatin the relationship between periodontal disease and the oral microbiota, little attention has been paid to the intersections of these domains.

METHODS

Here, we used high-throughput 16S rRNA sequencing to analyse the differences in the microbial composition in saliva between a group of patients with chronic periodontitis (C; n = 51) and a healthy control group (H; n = 61) and predicted the functional gene composition by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States.

RESULTS

We found significant alterations in oral microbial diversity between C and H (P = 0.002). Sixteen genera were significantly different between C and H, and 15 of them were enriched in C linear discriminant analysis (LDA > 2). Fifty functional genes were significantly different between C and H, and 34 of them were enriched in C (P < .025).

CONCLUSIONS

Periodontitis is associated with significant changes in the oral microbial community.

Construction of a versatile in vitro cultivation screening platform using human oral microbiota

We developed a simulation model of human oral microbiota using Bio Palette oral medium (BPOM) containing 0.02% glucose and lower bacterial nitrogen sources, derived from saliva and dental plaque. By decreasing the concentration of Gifu anaerobic medium (GAM) from 30 to 10 g L-1 , we observed increased ratios of target pathogenic genera, Porphyromonas and Fusobacterium from 0.5% and 1.7% to 1.2% and 3.5%, respectively, in the biofilm on hydroxyapatite (HA) discs. BPOM exhibited the higher ratios of Porphyromonas and Fusobacterium, and amplicon sequence variant number on HA, compared with GAM, modified GAM and basal medium mucin. Mixing glycerol stocks of BPOM culture solutions from four human subjects resulted in comparable ratios of these bacteria to the original saliva. In this simulation model, sitafloxacin showed higher inhibitory effects on P. gingivalis than minocycline hydrochloride at a low dosage of 0.1 μg mL-1 . Probiotics such as Streptococcus salivarius and Limosilactobacillus fermentum also showed significant decreases in Porphyromonas and Fusobacterium ratios on HA, respectively. Overall, the study suggests that BPOM with low carbon and nutrients could be a versatile platform for assessing the efficacy of antibiotics and live biotherapeutics in treating oral diseases caused by Porphyromonas and Fusobacterium.

Microbial dextran-hydrolyzing enzyme: Properties, structural features, and versatile applications

Dextran, an α-glucan mainly composed of (α1 → 6) linkages, has been widely applied in the food, cosmetic, and medicine industries. Dextranase can hydrolyze dextran to synthesize oligodextrans, which show prominent properties and promising applications in the food industry. Dextranases are widely distributed in bacteria, yeasts, and fungus, and classified into glycoside hydrolase (GH) 13, 15, 31, 49, and 66 families according to their sequence similarity, structural features, and reaction types. Dextranase, as a dextran-hydrolyzing enzyme, displays great application potential in the sugar-making, oral health care, medicine, and biotechnology industries. Here we mainly focused on presenting the enzymatic properties, structural features, and versatile (potential) applications of dextranase. To date, seven crystal structures of dextranases from GH 13, 15, 31, 49, and 66 families have been successfully solved. However, their molecular mechanisms for hydrolyzing dextran, especially on the size determinants of the hydrolysates, remain largely unknown. Additionally, the classification, microbial distribution, and immobilization technology of dextranase were also discussed in detail. This review discussed dextranase from different aspects with the ambition to present how they constitute the groundwork for promising future developments.

Hemophore-like proteins of the HmuY family in the oral and gut microbiome: unraveling the mystery of their evolution

SUMMARY

Heme (iron protoporphyrin IX, FePPIX) is the main source of iron and PPIX for host-associated pathogenic bacteria, including members of the Bacteroidota (formerly Bacteroidetes) phylum. Porphyromonas gingivalis, a keystone oral pathogen, uses a unique heme uptake (Hmu) system, comprising a hemophore-like protein, designated as the first member of the novel HmuY family. Compared to classical, secreted hemophores utilized by Gram-negative bacteria or near-iron transporter domain-based hemophores utilized by Gram-positive bacteria, the HmuY family comprises structurally similar proteins that have undergone diversification during evolution. The best characterized are P. gingivalis HmuY and its homologs from Tannerella forsythia (Tfo), Prevotella intermedia (PinO and PinA), Bacteroides vulgatus (Bvu), and Bacteroides fragilis (BfrA, BfrB, and BfrC). In contrast to the two histidine residues coordinating heme iron in P. gingivalis HmuY, Tfo, PinO, PinA, Bvu, and BfrA preferentially use two methionine residues. Interestingly, BfrB, despite conserved methionine residue, binds the PPIX ring without iron coordination. BfrC binds neither heme nor PPIX in keeping with the lack of conserved histidine or methionine residues used by other members of the HmuY family. HmuY competes for heme binding and heme sequestration from host hemoproteins with other members of the HmuY family to increase P. gingivalis competitiveness. The participation of HmuY in the host immune response confirms its relevance in relation to the survival of P. gingivalis and its ability to induce dysbiosis not only in the oral microbiome but also in the gut microbiome or other host niches, leading to local injuries and involvement in comorbidities.

Transcriptome and metabolome analyses of Streptococcus gordonii DL1 under acidic conditions

OBJECTIVES

Streptococcus gordonii is associated with the formation of biofilms, especially those that comprise dental plaque. Notably, S. gordonii DL1 causes infective endocarditis (IE). Colonization of this bacterium requires a mechanism that can tolerate a drop in environmental pH by producing acid via its own sugar metabolism. The ability to survive acidic environmental conditions might allow the bacterium to establish vegetative colonization even in the endocardium due to inflammation-induced lowering of pH, increasing the risk of IE. At present, the mechanism by which S. gordonii DL1 survives under acidic conditions is not thoroughly elucidated. The present study was thus conducted to elucidate the mechanism(s) by which S. gordonii DL1 survives under acidic conditions.

METHODS

We analyzed dynamic changes in gene transcription and intracellular metabolites in S. gordonii DL1 exposed to acidic conditions, using transcriptome and metabolome analyses.

RESULTS

Transcriptome analysis revealed upregulation of genes involved in heat shock response and glycolysis, and down regulation of genes involved in phosphotransferase systems and biosynthesis of amino acids. The most upregulated genes were a beta-strand repeat protein of unknown function (SGO_RS06325), followed by copper-translocating P-type ATPase (SGO_RS09470) and malic enzyme (SGO_RS01850). The latter two of these contribute to cytoplasmic alkalinization. S. gordonii mutant strains lacking each of these genes showed significantly reduced survival under acidic conditions. Metabolome analysis revealed that cytoplasmic levels of several amino acids were reduced.

CONCLUSIONS

S. gordonii survives the acidic conditions by recovering the acidic cytoplasm using the various activities, which are regulated at the transcriptional level.

Interactions and effects of a stannous-containing sodium fluoride dentifrice on oral pathogens and the oral microbiome

Numerous studies have investigated the effects of stannous ions on specific microbes and their efficacy in reducing dental plaque. Nonetheless, our understanding of their impact on the oral microbiome is still a subject of ongoing exploration. Therefore, this study sought to evaluate the effects of a stannous-containing sodium fluoride dentifrice in comparison to a zinc-containing sodium fluoride dentifrice and a control group on intact, healthy oral biofilms. Utilizing the novel 2bRAD-M approach for species-resolved metagenomics, and FISH/CLSM with probes targeting periodontal and caries associated species alongside Sn2+ and Zn2+ ions, we collected and analyzed in situ biofilms from 15 generally healthy individuals with measurable dental plaque and treated the biofilms with dentifrices to elucidate variations in microbial distribution. Although significant shifts in the microbiome upon treatment were not observed, the use of a stannous-containing sodium fluoride dentifrice primarily led to an increase in health-associated commensal species and decrease in pathogenic species. Notably, FISH/CLSM analysis highlighted a marked reduction in representative species associated with periodontitis and caries following treatment with the use of a stannous-containing sodium fluoride dentifrice, as opposed to a zinc-containing sodium fluoride dentifrice and the control group. Additionally, Sn2+ specific intracellular imaging reflected the colocalization of Sn2+ ions with P. gingivalis but not with other species. In contrast, Zn2+ ions exhibited non-specific binding, thus suggesting that Sn2+ could exhibit selective binding toward pathogenic species. Altogether, our results demonstrate that stannous ions could help to maintain a healthy oral microbiome by preferentially targeting certain pathogenic bacteria to reverse dysbiosis and underscores the importance of the continual usage of such products as a preventive measure for oral diseases and the maintenance of health.

3Y-TZP/Ta Biocermet as a Dental Material: An Analysis of the In Vitro Adherence of Streptococcus Oralis Biofilm and an In Vivo Pilot Study in Dogs

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic-metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic-metal biocomposite may be a promising new material for use in dentistry.

Alcohol Consumption and the Diversity of the Oral Microbiome in Postmenopausal Women

BACKGROUND

Alcohol reduces neutrophil function and decreases salivary flow, which could affect the composition of the oral microbiome.

OBJECTIVE

We hypothesized that the α- and β-diversity of the oral microbiome and the relative abundance of bacterial taxa would differ by frequency and type of alcohol consumption.

METHODS

We used a food frequency questionnaire to assess the frequency of consumption of beer, wine, and liquor (drinks/week) in a sample of 1179 postmenopausal women in the Osteoporosis and Periodontal Disease Study. Women were categorized as nondrinkers, drinking <1 drink/wk, ≥1 to <7 drinks/wk, or ≥7 drinks/wk for total alcohol consumption and for beer, wine, and liquor consumption. The composition and diversity of the oral microbiome was assessed from subgingival plaque samples using 16S ribosomal RNA amplicon sequencing. Permutational multivariate analysis of variance (PERMANOVA) was used to examine β-diversity (between-sample diversity) in the microbiome between alcohol consumption categories. Analysis of covariance was used to examine the mean α-diversity (within-sample diversity), assessed by the Shannon index (species evenness), Chao1 index (species richness), and observed operational taxonomic unit (OTU) count and the mean relative abundance of 245 bacterial taxa across alcohol consumption categories.

RESULTS

Over half of the participants (67%) consumed alcohol, with 14% reporting ≥1 drink/d. The β-diversity across categories of total alcohol consumption, but not categories of alcohol type, was statistically significantly different (P for PERMANOVA = 0.016). Mean α-diversity measures were statistically significantly higher (P < 0.05) in the highest category of total alcohol and wine consumption compared to nondrinkers; no significant associations were found for beer or liquor consumption. The relative abundance of 1 OTU, Selenomonassp._oral_taxon_133, was significantly lower in the highest level of total alcohol consumption compared to nondrinkers after adjustment for multiple comparisons.

CONCLUSIONS

Alcohol consumption was associated with the diversity and composition of the subgingival microbiome.

Pudilan Keyanning mouthwash inhibits dextran-dependent aggregation and biofilm organization of Streptococcus mutans

AIMS

This research aimed to investigate the inhibitory effects of Pudilan mouthwash (PDL) on Streptococcus mutans (S. mutans) biofilms and identify its chemical components.

METHODS AND RESULTS

The impacts of 100% concentrated PDL on S. mutans biofilm were detected by colony-forming unit (CFU) assays, crystal violet staining, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and quantitative real-time PCR (qRT‒PCR). The biocompatibility with human gingival fibroblasts (HGFs) was evaluated by Cell-Counting-Kit-8 (CCK-8) assay. And chemical components were identified by UPLC-HRMS. PBS and 0.12% chlorhexidine were used as negative and positive controls, respectively. Results indicate early 8-h S. mutans biofilms are sensitive to PDL. Additionally, it leads to a decrease in bacterial activities and dextran-dependent aggregation in 24-h S. mutans biofilms. PDL significantly downregulates the gene expression of gtfB/C/D and smc. And 114 components are identified.

CONCLUSIONS

PDL has an inhibitory effect on S. mutans and favorable biocompatibility. It has potential to be exploited as a novel anti-biofilm agent.

Characteristics of oral microbiota and oral health in the patients treated with clear aligners: a prospective study

OBJECTIVES

In this prospective clinical study, the effect of clear aligners on periodontal health and oral hygiene was examined. As the same time, microbial changes of the aligner tray and subgingival microbiota community were investigated.

METHODS

The study recruited fifteen patients, and clinical parameters were recorded at three different time points: before the initiation of aligner treatment (T0), 1 month after treatment onset (T1), and 3 months after treatment onset (T3). Plaque samples were collected from the inner surface of aligners and subgingival sulcus at each of these time points. The microbial composition of the samples was analyzed using 16S rRNA gene sequencing, and changes were evaluated based on the abundance of amplicon sequence variants (ASVs).

RESULTS

Reduction in plaque index and improvement in periodontal health were observed. In aligner tray plaque samples, the relative abundance of Streptococcus increased significantly, as well as the richness and diversity of microbiota decreased substantially as the duration of treatment time. In subgingival plaque samples, alpha and beta diversity of microbiota did not change significantly.

CONCLUSIONS

During the clear aligner treatment, the patients' periodontium remained in a healthy condition, and clear aligner treatment had no significant impact on the composition of subgingival microbiota. The structure of the aligner tray microbiota altered significantly at both phylum and genus levels and attracted a unique and less diverse microbiota community.

CLABSINABSICAL RELEVANCE

Clear aligner treatment has no significant impact on periodontal health and subgingival microbiota composition of patients.

The composition of the dental pellicle: an updated literature review

Background

The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation.

Methods

For this updated literature review, the PubMed database was searched for the dental pellicle and its composition.

Results

The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates.

Conclusions

The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.

The recovery of the microbial community after plaque removal depends on periodontal health status

Plaque accumulation and microbial community changes are important causes of periodontal disease. Cleaned plaque microorganisms will reattach to form biofilms, but the recovery and outcome of plaque microbial communities in different periodontal health states remain unknown. In this study, we tracked the biofilm remodeling process in 206 dental plaque samples from 40 healthy periodontal, gingivitis and periodontitis volunteers at 6 time points before and after supragingival scaling. We found that microbial communities of different periodontal states changed asynchronously during the process, and the more severe the periodontal disease condition, the more lagged the recovery of plaque microorganisms to their original state after cleaning; this reflected a higher degree of plaque development in periodontitis samples. The plaque index and bleeding index were significantly correlated with plaque recovery, especially the recovery of bacteria such as Abiotrophia and Capnocytophaga. Meanwhile, we found that the microbial community structure of different periodontal health states was most similar at the Day 3 after plaque cleaning, and the communities gradually differentiated and developed in different directions. Abiotrophia and other bacteria might play an important role in determining the development trend of plaque biofilms. The discovery of specific time points and bacteria was of great value in clarifying the pathogenesis of periodontal disease and in seeking targets for prevention and treatment.

Antimicrobial activity of probiotic Streptococcus salivarius LAB813 on in vitro cariogenic biofilms

OBJECTIVE

To investigate the antimicrobial activity of a novel commensal strain of Streptococcus salivarius, LAB813, against Streptococcus mutans biofilms.

METHODS

The inhibitory activity of LAB813 towards S. mutans was tested using mono-, dual-, and multi-species cariogenic biofilms formed on three types of orthodontic appliances (metal, ceramic, aligner). The activity of the commercially available probiotic, BLIS M18™ was used as control.

RESULTS

LAB813 significantly inhibited S. mutans biofilms with cell killing approximating 99% for all materials. LAB813 showed effectiveness at inhibiting S. mutans in more complex multi-species biofilms with cell killing approximating 90% for all three materials. When comparing the killing kinetics of the probiotics, LAB813 had a faster rate of killing biofilms than M18. Experiments conducted with cell-free culture supernatant confirmed the presence of an inhibitory substance of proteinaceous nature. The addition of xylitol, a common sugar substitute used for human consumption, potentiated the inhibitory effects of LAB813 against S. mutans embedded in a more complex fungal-bacterial biofilm.

CONCLUSIONS

LAB813 possesses strong antimicrobial activity, potent anti-biofilm properties, and enhanced antimicrobial activity in the presence of xylitol. The identification and characterization of strain LAB813 exhibiting antimicrobial activity towards S. mutans hold exciting promise for this novel strain to be developed as an oral probiotic for use in the prevention of dental caries.

Effectiveness of Toothbrushing Technique for Biofilm Removal and Postoperative Infection Control after Spinal Fusion Surgery: A Retrospective Study

This retrospective study was designed to investigate the effectiveness of using a toothbrush, which is commonly used in our daily life, for biofilm removal and infection control in the treatment of spinal infections occurring after spinal fusion surgery. Currently, a biofilm is thought to form on the surface of the metal inserted during spine fusion surgery. We aim to determine the differences in clinical outcomes between using and not using a toothbrush to remove biofilm while performing conventional drainage, curettage, and debridement. A total of 1081 patients who underwent anterior or posterior spinal fusion surgery between November 2018 and October 2022 were screened. The study included 60 patients who developed surgical site infection and underwent incision and drainage surgery either with a toothbrush (n = 20) or without a toothbrush (n = 40). Failure of infection control that requires revision surgery occurred in 2 patients (10%) in the Toothbrush group and in 14 patients (35%) in the No-Toothbrush group (p = 0.039). Thus, the rate of additional surgery was significantly lower in the Toothbrush group. Additionally, normalization of c-reactive protein levels occurred significantly faster in the Toothbrush group (p = 0.044). Therefore, using a toothbrush to treat spinal infections following spinal fusion surgery appears to have beneficial mechanical debridement effects, resulting in improved clinical results, which were also confirmed based on the electron microscopic images.

Development of a xylose-inducible promoter and riboswitch combination system for manipulating gene expression in Fusobacterium nucleatum

Inducible gene expression systems are important for studying bacterial gene function, yet most exhibit leakage. In this study, we engineered a leakage-free hybrid system for precise gene expression controls in Fusobacterium nucleatum by integrating the xylose-inducible expression system with the theophylline-responsive riboswitch. This innovative method enables concurrent control of target gene expression at both transcription and translation initiation levels. Using luciferase and the indole-producing enzyme tryptophanase (TnaA) as reporters, we demonstrated that the hybrid system displays virtually no observable signal in the absence of inducers. We employed this system to express FtsX, a protein related to fusobacterial cytokinesis, in an ftsX mutant strain, unveiling a dose-dependent manner in FtsX production. Without inducers, cells form long filaments, while increasing FtsX levels by increasing inducer concentrations led to a gradual reduction in cell length until normal morphology was restored. Crucially, this system facilitated essential gene investigation, identifying the signal peptidase lepB gene as vital for F. nucleatum. LepB's essentiality stems from depletion, affecting outer membrane biogenesis and cell division. This novel hybrid system holds the potential for advancing research on essential genes and accurate gene regulation in F. nucleatum. IMPORTANCE Fusobacterium nucleatum, an anaerobic bacterium prevalent in the human oral cavity, is strongly linked to periodontitis and can colonize areas beyond the oral cavity, such as the placenta and gastrointestinal tract, causing adverse pregnancy outcomes and promoting colorectal cancer growth. Given F. nucleatum's clinical significance, research is underway to develop targeted therapies to inhibit its growth or eradicate the bacterium specifically. Essential genes, crucial for bacterial survival, growth, and reproduction, are promising drug targets. A leak-free-inducible gene expression system is needed for studying these genes, enabling conditional gene knockouts and elucidating the importance of those essential genes. Our study identified lepB as the essential gene by first generating a conditional gene mutation in F. nucleatum. Combining a xylose-inducible system with a riboswitch facilitated the analysis of essential genes in F. nucleatum, paving the way for potential drug development targeting this bacterium for various clinical applications.

Social networking at the microbiome-host interface

Microbial species colonizing host ecosystems in health or disease rarely do so alone. Organisms conglomerate into dynamic heterotypic communities or biofilms in which interspecies and interkingdom interactions drive functional specialization of constituent species and shape community properties, including nososymbiocity or pathogenic potential. Cell-to-cell binding, exchange of signaling molecules, and nutritional codependencies can all contribute to the emergent properties of these communities. Spatial constraints defined by community architecture also determine overall community function. Multilayered interactions thus occur between individual pairs of organisms, and the relative impact can be determined by contextual cues. Host responses to heterotypic communities and impact on host surfaces are also driven by the collective action of the community. Additionally, the range of interspecies interactions can be extended by bacteria utilizing host cells or host diet to indirectly or directly influence the properties of other organisms and the community microenvironment. In contexts where communities transition to a dysbiotic state, their quasi-organismal nature imparts adaptability to nutritional availability and facilitates resistance to immune effectors and, moreover, exploits inflammatory and acidic microenvironments for their persistence.

Efficient clearance of periodontitis pathogens by S. gordonii membrane-coated H2O2 self-supplied nanocomposites in a "Jenga" style

As a key pathogen of periodontitis, P. gingivalis requires support of the initial colonizing bacterium (S. gordonii preferably) to form symbiotic biofilms on gingival tissues with enhanced antibiotic resistance. Here, we report a new strategy to treat periodontitis biofilms with S. gordonii membrane-coated H2O2 self-supplied nanocomposites (ZnO2/Fe3O4@MV NPs) in a "Jenga" style. Integration of our special MV coatings enables selectively enhanced internalization of the cargos in S. gordonii, thus inducing severe damage to the foundational bacterial layer and collapse/clearance of symbiotic biofilms consequently. This strategy allows us to clear the symbiotic biofilms of S. gordonii and P. gingivalis with active hydroxyl radicals (˙OH) derived from ZnO2-Fe3O4@MV NPs in a H2O2 self-supplied, nanocatalyst-assisted manner. This "Jenga-style" treatment provides a cutting-edge proof of concept for the removal of otherwise robust symbiotic biofilms of periodontitis where the critical pathogens are difficult to target and have antibiotic resistance.

Methods for Evaluating the Effectiveness of Home Oral Hygiene Measures-A Narrative Review of Dental Biofilm Indices

Dental plaque is a biofilm structured in an extracellular matrix of polymers of host and microbial origin; the microorganisms can coexist in harmony with the host, thus guarantying oral health. Environmental modifications can lead to dysbiosis and onset of oral diseases; in fact, plaque is the etiological agent both of periodontal disease and dental decay. The use of an effective oral hygiene index should be considered as a relevant goal for the clinicians and the researchers, and consequently, numerous plaque indices have been proposed during the years. The present literature review aims primarily to obtain a complete summary of these scores to assess plaque deposits. It is useful because the clinician/researcher will select the right scoring method for the specific situation only if he knows the available options and if he is aware of both their strengths and weaknesses. This review applies a basic classification of plaque indices that distinguishes the ones that use non-quantitative methods from the ones that use quantitative methods. Non-quantitative methods are more subjective because they are based on the ability of the clinician to point out the presence or the entity of deposits, while quantitative methods introduce objectifiable means to measure plaque deposits.

Development of a novel, entirely herbal-based mouthwash effective against common oral bacteria and SARS-CoV-2

BACKGROUND

Parallel to the growth of the oral healthcare market, there is a constantly increasing demand for natural products as well. Many customers prefer products that contain fewer toxic agents, therefore providing an environmentally friendly solution with the benefit of smaller risk to the user. Medieval and early modern medicinal knowledge might be useful when looking for natural, herbal-based components to develop modern products. Along with these considerations we created, tested, and compared an entirely natural mouthwash, named Herba Dei.

METHODS

The manufacturing procedure was standardized, and the created tincture was evaluated by GC/MS analysis for active compounds, experimentally tested in cell-based cytotoxicity, salivary protein integrity, cell-free antioxidant activity, anti-bacterial and anti-viral assays, and compared with three market-leading mouthwashes.

RESULTS

Our tincture did not show significant damage in the cytotoxicity assays to keratinocyte and Vero E6 cells and did not disrupt the low molecular weight salivary proteins. Its radical scavenging capacity surpassed that of two tested, partly natural, and synthetic mouthwashes, while its antibacterial activity was comparable to the tested products, or higher in the bacterial aerobic respiratory assay. The active compounds responsible for the effects include naturally occurring phenylpropanoids, terpenes, and terpenoids. Our mouthwash proved to be effective in vitro in lowering the copy number of SARS-CoV-2 in circumstances mimicking the salivary environment.

CONCLUSIONS

The developed product might be a useful tool to impede the transmission and spread of SARS-CoV-2 in interpersonal contact and aerosol-generating conditions. Our mouthwash can help reduce the oral bacterial flora and has an antioxidant activity that facilitates wound healing and prevents adverse effects of smoke in the oral cavity.

Development of a Xylose-Inducible Promoter and Riboswitch Combination System for Manipulating Gene Expression in Fusobacterium nucleatum

Inducible gene expression systems are important for studying bacterial gene function, yet most exhibit leakage. In this study, we engineered a leakage-free hybrid system for precise gene expression controls in Fusobacterium nucleatum by integrating the xylose-inducible expression system with the theophylline-responsive riboswitch. This innovative method enables concurrent control of target gene expression at both transcription and translation initiation levels. Using luciferase and the indole-producing enzyme tryptophanase (TnaA) as reporters, we demonstrated that the hybrid system displays virtually no observable signal in the absence of inducers. We employed this system to express FtsX, a protein related to fusobacterial cytokinesis, in an ftsX mutant strain, unveiling a dose-dependent manner in FtsX production. Without inducers, cells form long filaments, while increasing FtsX levels by increasing inducers concentrations led to a gradual reduction in cell length until normal morphology was restored. Crucially, this system facilitated essential gene investigation, identifying the signal peptidase lepB gene as vital for F. nucleatum . LepB's essentiality stems from depletion, affecting outer membrane biogenesis and cell division. This novel hybrid system holds the potential for advancing research on essential genes and accurate gene regulation in F. nucleatum .

Influence of the vegan, vegetarian and omnivore diet on the oral health status in adults: a systematic review and meta-analysis

OBJECTIVE

This systematic review aimed to evaluate the influence of the nature of diet (vegan, vegetarian, and omnivore) on the oral health status in adults.

METHODS

This systematic review and meta-analysis was performed using the PRISMA guidelines. Electronic databases [PubMed, Embase, CENTRAL], online search engines (Google Scholar), research portals, and hand searches were performed systematically to identify studies. The last literature search was performed February 1st, 2021. Studies were included if they reported on the influence of the nature of diet on the oral health status (oral hygiene, periodontal health, dental status, and salivary function) in adults, by two investigators. Inter-investigator reliability was evaluated using Kappa (κ) statistics. PROSPERO registration number: CRD42020211567.

RESULTS

Twenty-two studies were included for data extraction and final analysis. The meta-analysis revealed that the bleeding on probing measure was higher in omnivores (Z = -4.057, p < 0.0001; 95% CI: -0.684, -0.238; I² = 0.0%) and the overall periodontal health was significantly better in vegan/vegetarians than omnivores (Z = -2.632, p = 0.008; 95% CI: -0.274, -0.073; I² = 29.7%). Vegan/vegetarians demonstrated more dental erosion (Z = 3.325, p = 0.001; 95% CI: 0.170, 0.659; I² = 0.0%). In adults over 60 years old, the prevalence of caries was higher in omnivores (Z = 3.244, p = 0.001; 95% CI: 0.092, 0.371; I² = 0.0%), while complete edentulism was more prevalent in vegetarians (Z = -4.147, p < 0.0001; 95% CI: -0.550, -0.197; I² = 0.0%).

CONCLUSIONS

This review reveals that adults on an omnivore diet may be associated with a higher risk for periodontal problems and dental caries, while vegetarians/vegans may be associated with a higher risk for dental erosion.

Modulation of Biofilm Formation and Permeability in Streptococcus mutans during Exposure To Zinc Acetate

The penetration of biofilms by antimicrobials is a potential limiting factor in biofilm control. This is relevant to oral health, as compounds that are used to control microbial growth and activities could also affect the permeability of dental plaque biofilm with secondary effects on biofilm tolerance. We investigated the effects of zinc salts on the permeability of Streptococcus mutans biofilms. Biofilms were grown with low concentrations of zinc acetate (ZA), and a transwell transportation assay was applied to test biofilm permeability in an apical-basolateral direction. Crystal violet assays and total viable counts were used to quantify the biofilm formation and viability, respectively, and short time frame diffusion rates within microcolonies were determined using spatial intensity distribution analysis (SpIDA). While the diffusion rates within biofilm microcolonies were not significantly altered, exposure to ZA significantly increased the overall permeability of S. mutans biofilms (P < 0.05) through decreased biofilm formation, particularly at concentrations above 0.3 mg/mL. Transport was significantly lower through biofilms grown in high sucrose conditions. IMPORTANCE Zinc salts are added to dentifrices to improve oral hygiene through the control of dental plaque. We describe a method for determining biofilm permeability and show a moderate inhibitory effect of zinc acetate on biofilm formation, and that this inhibitory effect is associated with increases in overall biofilm permeability.

Selenomonas sputigena Interactions with Gingival Epithelial Cells That Promote Inflammation

Increased prevalence and abundance of Selenomonas sputigena have been associated with periodontitis, a chronic inflammatory disease of tooth-supporting tissues, for more than 50 years. Over the past decade, molecular surveys of periodontal disease using 16S and shotgun metagenomic sequencing approaches have confirmed the disease association of classically recognized periodontal pathogens such as Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia while highlighting previously underappreciated organisms such as Filifactor alocis and S. sputigena. Despite abundant clinical association between S. sputigena and periodontal disease, we have little to no understanding of its pathogenic potential, and virulence mechanisms have not been studied. In this study, we sought to characterize the response of gingival epithelial cells to infection with S. sputigena. Here, we show that S. sputigena attaches to gingival keratinocytes and induces expression and secretion of cytokines and chemokines associated with inflammation and leukocyte recruitment. We demonstrate that S. sputigena induces signaling through Toll-like receptor 2 (TLR2) and TLR4 but evades activation of TLR5. Cytokines released from S. sputigena-infected keratinocytes induced monocyte and neutrophil chemotaxis. These results show that S. sputigena-host interactions have the potential to contribute to bacterially driven inflammation and tissue destruction, the hallmark of periodontitis. Characterization of previously unstudied pathogens may provide novel approaches to develop therapeutics to treat or prevent periodontal disease.

Inhibitory Activity of Essential Oils of Mentha spicata and Eucalyptus globulus on Biofilms of Streptococcus mutans in an In Vitro Model

The aim of this study was to evaluate the inhibitory activity of the commercially available essential oils of Mentha spicata (spearmint) and Eucalyptus globulus (eucalyptus) on Streptococcus mutans ATCC 25175 biofilms in vitro, emulating dental plaque conditions. The composition of the essential oils (EOs) was determined using gas chromatography coupled with mass spectrometry (GC-MS), with the main metabolites being Carvone (57.93%) and Limonene (12.91%) for Mentha spicata and 1,8-Cineole (Eucalyptol) (65.83%) for Eucalyptus globulus. The inhibitory activity was evaluated using the methods of agar-well diffusion and colorimetric microdilution. The inhibition halos were 18.3 ± 0.47 mm and 27.0 ± 0.82 mm, and the MICs were 1.8484 mg/mL and 1.9168 mg/mL for the EOs of Mentha spicata and Eucalyptus globulus, respectively. The activity against the biofilms was evaluated on a substrate of bovine enamel pieces using a basal mucin medium (BMM) in anaerobic conditions with daily sucrose exposition cycles in order to emulate oral cavity conditions. The EOs were applied in a concentration of 0.5% in a sterile saline vehicle with 1% polysorbate 20. After 72 h of cultivation, a significant reduction was observed (p < 0.001%) on the biofilm biomass, which was evaluated by its turbidity in suspension and using a count of the recoverable organisms with regards to the control. The effects of the Eos were not significantly distinct from each other. The EOs showed antimicrobial activity against both the Streptococcus mutans planktonic and biofilm cultures. Thus, EOs may have great potential for the development of pharmaceutical and sanitary products for oral health.

Identification of a Czc-like operon of the periodontal pathobiont P. gingivalis involved in metal ion efflux

OBJECTIVE

The study aimed to investigate the role of the PGN2012 gene of the periodontitis contributing pathobiont Porphyromonas gingivalis. PGN2012 is a homolgue of TolC and is a gene our group previously showed was overexpressed in hyperinvasive cells.

METHODS

The study used a combination of bioinformatics, knockout mutagenesis, growth experiments, biofilm assays and human cell invation assays to investigate PGN2012 function.

RESULTS

Bioinformatics identified that PGN2012 is part of one of four TolC containing gene loci in P. gingivalis that we predicted may encode a metal resistance RND family tripartite pump, similar to those present in other Gram-negative bacteria, but which are not well understood in anaerobic bacteria. A ΔPGN2012 deletion displayed slightly reduced growth in liquid culture but did not effect biofilm formation or human cell invasion. When metal ions were included in the medium the mutant displayed significantly increased sensitivity to the divalent metal ions Zn²⁺ (500 μM), Co²⁺ (2 mM), and Cd²⁺(0.1 mM) but not Cu²⁺.

CONCLUSIONS

We propose to rename the PGN2012-2014 genes czcCBA, which we suggest plays a role in intracellular stress resistance where zinc is often employed by host cells in antibacterial defence with implications for chronic infection in humans.

Methods to Study Antagonistic Activities Among Oral Bacteria

Most bacteria in nature exist in multispecies communities known as biofilms. In the natural habitat where resources (nutrient, space, etc.) are usually limited, individual species must compete or collaborate with other neighboring species in order to perpetuate in the multispecies community. The human oral cavity is colonized by >700 microbial species known as the indigenous microbiota. This indigenous flora normally maintains an ecological balance through antagonistic as well as mutualistic interspecies interactions. However, environmental perturbation may disrupt this balance, leading to overgrowth of pathogenic species which could in turn initiate diseases such as dental caries (tooth decay) and periodontitis (gum disease). Understanding the mechanisms of diversity maintenance may help developing novel approaches to manage these "polymicrobial diseases". In this chapter, we will focus on a well-characterized form of biochemical warfare: bacteriocins produced by Streptococcus mutans, a primary dental caries pathogen, and hydrogen peroxide (H₂O₂) produced by several oral commensal streptococci. We will describe detailed methodologies on the competition assay, isolation, purification, and characterization of bacteriocins.

Novel protein-repellent and antibacterial polymethyl methacrylate dental resin in water-aging for 6 months

Background

The present study aimed to develop a novel protein-repellent and antibacterial polymethyl methacrylate (PMMA) dental resin with 2-methacryloyloxyethyl phosphorylcholine (MPC) and quaternary ammonium dimethylaminohexadecyl methacrylate (DMAHDM), and to investigate the effects of water-aging for 6 months on the mechanical properties, protein adsorption, and antibacterial activity of the dental resin.

Methods

Four groups were tested: PMMA control; PMMA + 3% MPC; PMMA + 1.5% DMAHDM; and PMMA + 3% MPC + 1.5% DMADDM in acrylic resin powder. Specimens were water-aged for 1 d, 3 months, and 6 months at 37 ℃. Their mechanical properties were then measured using a three-point flexure test. Protein adsorption was measured using a micro bicinchoninic acid (BCA) method. A human saliva microcosm model was used to inoculate bacteria on water-aged specimens and to investigate the live/dead staining, metabolic activity of biofilms, and colony-forming units (CFUs).

Results

The flexural strength and elastic modulus showed a significant loss after 6 months of water-ageing for the PMMA control (mean ± SD; n = 10); in contrast, the new protein repellent and antibacterial PMMA resin showed no strength loss. The PMMA–MPC–DMAHDM-containing resin imparted a strong antibacterial effect by greatly reducing biofilm viability and metabolic activity. The biofilm CFU count was reduced by about two orders of magnitude (p < 0.05) compared with that of the PMMA resin control. The protein adsorption was 20% that of a commercial composite (p < 0.05). Furthermore, the PMMA–MPC–DMAHDM-containing resin exhibited a long-term antibacterial performance, with no significant difference between 1 d, 3 months and 6 months (p > 0.05).

Conclusions

The flexural strength and elastic modulus of the PMMA–MPC–DMAHDM-containing resin were superior to those of the PMMA control after 6 months of water-ageing. The novel PMMA resin incorporating MPC and DMAHDM exhibited potent and lasting protein-repellent and antibacterial properties.

Peridontitis as a Risk Factor for Attention Deficit Hyperactivity Disorder: Possible Neuro-inflammatory Mechanisms

Periodontitis is a condition caused mostly by the creation of a biofilm by the bacterium P. gingivalis, which releases toxins and damages the tooth structure. Recent research studies have reported association between dental health and neuropsychiatric illnesses. Neuroinflammation triggered by the first systemic inflammation caused by the bacterium present in the oral cavities is a plausible explanation for such a relationship. Substantial amount of evidence supports the role of neuroinflammation and dysfunction of the dopaminergic system in the pathology of ADHD (Attention deficit hyperactivity disorders). Recent epidemiological, microbiological and inflammatory findings strengthen that, periodontal bacteria, which cause systemic inflammation can contribute to neuroinflammation and finally ADHD. Although both diseases are characterized by inflammation, the specific pathways and crosslink's between periodontitis and ADHD remain unknown. Here, the authors describe the inflammatory elements of periodontitis, how this dental illness causes systemic inflammation, and how this systemic inflammation contributes to deteriorating neuroinflammation in the evolution of ADHD. Therefore, the aim of this review is to present possible links and mechanisms that could confirm the evidence of this association.

The role of bacterial corrosion on recolonization of titanium implant surfaces: An in vitro study

BACKGROUND

Inflammation triggered by bacterial biofilms in the surrounding tissue is a major etiological factor for peri-implantitis and subsequent implant failure. However, little is known about the direct effects of bacterial corrosion and recolonization on implant failure PURPOSE: To investigate the influence of oral commensals on bacterial corrosion and recolonization of titanium surfaces.

MATERIALS AND METHODS

Streptococcus sanguinis (S. sanguinis) and Porphyromonas gingivalis (P. gingivalis), which are key bacteria in oral biofilm formation, were cultured on commercially pure titanium and titanium-aluminum-vanadium (Ti6Al4V) plates in artificial saliva/brain heart infusion medium under aerobic or anaerobic conditions. Biofilm formation was examined after 7 and 21 days by crystal violet and live/dead staining. Titanium ions released into culture supernatants were analyzed over a period of 21 days by atomic absorption spectrometry. Visual changes in surface morphology were investigated using scanning electron microscopy. Biofilm formation on sterilized, biocorroded, and recolonized implant surfaces was determined by crystal violet staining.

RESULTS

S. sanguinis and P. gingivalis formed stable biofilms on the titanium samples. Bacterial corrosion led to a significant increase in titanium ion release from these titanium plates (p < 0.01), which was significantly higher under aerobic conditions on pure titanium (p ≤ 0.001). No obvious morphological surface changes, such as pitting and discoloration, were detected in the titanium samples. During early biofilm formation, the addition of titanium ions significantly decreased the number of live cells. In contrast, a significant effect on biofilm mass was only detected with P. gingivalis. Bacterial corrosion had no influence on bacterial recolonization following sterilization of titanium and Ti6Al4V surfaces.

CONCLUSION

Bacterial corrosion differs between oral commensal bacteria and leads to increased titanium ion release from titanium plates. The titanium ion release did not influence biofilm formation or bacterial recolonization under in vitro conditions.

Evaluation of antimicrobial and cytotoxic effects of Echinacea and Arctium extracts and Zataria essential oil

Dental caries and oral infections have become a widespread issue in the modern world. This study aimed to investigate the antibacterial, antifungal, and cytotoxicity characteristics of the extracts of Echinacea purpura, Arctium lappa, and the essential oil of Zataria multiflora as a potential herbal mouthwash. The essential oil of Z. multiflora leaves and the extracts of E. purpurea and A. lappa roots were prepared. The characterization was carried out by GC-MS and also, total phenol and flavonoid were assed for all three samples. The antimicrobial and anti-biofilm effects were evaluated against Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Lactobacillus acidophilus, Escherichia coli, Staphylococcus aureus, and Candida albicans. The cytotoxic effect of the samples was evaluated on HEK 293 and HDFa cells by MTT test. Thymol and carvacrol contents in EO of Z. multiflora were measured at 31% and 42.2%, respectively. A. lappa had the lowest total phenolic and flavonoid value among the samples. On the other hand, the total phenolic content of Z. multiflora and the total flavonoid content of E. purpurea were the highest. The MIC values of Zataria, Arctium, and Echinacea against S. mutans were 0.011% v/v, 187.5 mg/ml, and 93.75 mg/ml, while MBC were 0.011% v/v, 375 mg/ml, and 187.5 mg/ml, respectively. The formulation showed bactericidal activity against S. mutans in the concentration of 5.86 mg/ml for Echinacea and Burdock extracts and 0.08 µl/ml for EO of Zataria. The formulation significantly affected microbial biofilm formation and induced biofilm degradation. The cell viability percentages were higher than 50% during 24 and 48 h. The formulation had a significant antimicrobial effect on cariogenic bacteria and C. albicans, with the lowest cytotoxic effects. Therefore, this formulation can be an appropriate candidate for mouthwash.

Association between Vitamin D Receptor Gene Polymorphisms and Periodontal Bacteria: A Clinical Pilot Study

Background: Periodontitis is an inflammatory disease caused by microorganisms involving the supporting tissues of the teeth. Gene variants may influence both the composition of the biofilm in the oral cavity and the host response. The objective of the study was to investigate the potential correlations between the disease susceptibility, the presence and the quantity of periodontopathogenic oral bacterial composition and the VDR gene polymorphisms. Methods: Fifty (50) unrelated periodontal patients and forty-one (41) healthy controls were selected for genomic DNA extraction. DNA concentration was measured and analyzed. The periodontopathogenic bacterial species were identified and quantified using a Real Time PCR performed with species-specific primers and probes. Results: Genotype distribution showed a different distribution between the groups for BsmI rs1544410 genotypes (p = 0.0001) with a prevalence of the G(b) allele in periodontal patients (p = 0.0003). Statistical significance was also found for VDR TaqI rs731236 (p ≤ 0.00001) with a prevalence of the T(T) allele in periodontal patients (p ≤ 0.00001). The average bacterial copy count for the periodontitis group was significantly higher than that of control group. Dividing patients into two groups based on high or low bacterial load, FokI rs2228570 T allele (f) was statistically more represented in patients with high bacterial load. Conclusions: The findings of the study suggest the involvement of the VDR gene BsmI and TaqI polymorphisms in periodontal disease, while FokI and BsmI may be involved in determining an increased presence of periodontopathogens.

A Cross-Talk between Diet and the Oral Microbiome: Balance of Nutrition on Inflammation and Immune System's Response during Periodontitis

Over the last few decades, studies on the oral microbiome have increased awareness that the balance between the host and the microbial species that coexist in it is essential for oral health at all stages of life. However, this balance is extremely difficult to maintain, and many factors can disrupt it: general eating habits, sugar consumption, tobacco smoking, oral hygiene, and use of antibiotics and other antimicrobials. It is now known that alterations in the oral microbiota are responsible for developing and promoting many oral diseases, including periodontal disease. In this context, diet is an area for further investigation as it has been observed that the intake of particular foods, such as farmed animal meat, dairy products, refined vegetable oils, and processed cereals, affects the composition of the microbiota, leading to an increased representation of acid-producing and acid-tolerant organisms and periodontal pathogens. However, little is known about the influence of diet on the oral microbiome and the creation of a suitable microenvironment for the development of periodontal disease. The aim of the present study is to evaluate current knowledge on the role of diet in the oral dysbiosis underlying periodontal disease.

An innovative oral management procedure to reduce postoperative complications

Background

Numerous studies have shown that improving oral hygiene contributes to a reduction in the risk of postoperative complications in patients with head and neck cancer, cardiac disease, and esophageal cancer. However, the beneficial standard for oral management procedures during the perioperative period has not yet been established. Therefore, our aim was to determine whether or not their innovative oral management intervention contributed to a reduction in postoperative complications in lung cancer.

Methods

We performed a retrospective analysis of medical records of patients who underwent lung cancer surgery with lobectomy and pneumonectomy at Kyorin University Hospital. Patients were divided into 2 groups: a perioperative oral management intervention group that underwent lung cancer surgery from April 2016 to March 2018 (n = 164), and a control group without oral management that underwent surgery from April 2014 to March 2016 (n = 199). In particular, our oral management procedure emphasized oral mucosa stimulation to induce saliva discharge as in gum chewing, rather than simply using teeth brushing to reduce oral microbiome. Therefore, our oral management procedure is different from traditional oral care.

Results

This study demonstrated that our oral management practice was associated with a decline in the occurrence of postoperative pneumonia (odds ratio, 0.184; 95% CI, 0.042-0.571; P = .009), postoperative hospital stay duration (β coefficient, −4.272; 95% CI, −6.390 to −2.155; P < .001) and Clavian-Dindo classification grade II or above (odds ratio, 0.503; 95% CI, 0.298-0.835; P = .009).

Conclusions

We propose an innovative new strategy using their unique oral management procedure to reduce postoperative complications resulting from pulmonary resection.

Mechanistic Effects of E-Liquids on Biofilm Formation and Growth of Oral Commensal Streptococcal Communities: Effect of Flavoring Agents

Background: Vaping has become a global health concern. As research continues, more studies are beginning to question the relative safety of E-liquid flavoring additives. The oral cavity is the first site of exposure to E-liquid aerosol, making it critical for investigation. Because of the importance of commensal bacterial biofilms for oral health, we sought to explore the effects of E-liquids ± flavors on the formation and growth of single- and multi-species biofilms and to investigate the mechanism of inhibition. Methods: Quantitative and confocal biofilm analysis, death curves, and colony-forming units (CFU) were evaluated with flavorless and flavored (tobacco, menthol, cinnamon, strawberry, blueberry) E-liquids using four strains of oral commensal bacteria (Streptococcus gordonii, Streptococcus intermedius, Streptococcus mitis, and Streptococcus oralis). Results: All flavoring agents show a dose-dependent inhibition in the growth of single-species and multi-species biofilms. Furthermore, CFUs, death curves, and light microscopy show that flavoring agents have a bactericidal mode of inhibition on the growth of these oral streptococci. Conclusions: These results show that flavored, rather than unflavored, E-liquids are more detrimental to biofilm formation and growth of oral commensal bacteria. Consequently, E-liquid flavorings agents could pose risks to the oral microenvironment, and by extension, to systemic health.

The Role of Glycoside Hydrolases in S. gordonii and C. albicans Interactions

Candida albicans can coaggregate with Streptococcus gordonii and cocolonize in the oral cavity. Saliva provides a vital microenvironment for close interactions of oral microorganisms. However, the level of fermentable carbohydrates in saliva is not sufficient to support the growth of multiple species. Glycoside hydrolases (GHs) that hydrolyze glycoproteins are critical for S. gordonii growth in low-fermentable-carbohydrate environments such as saliva. However, whether GHs are involved in the cross-kingdom interactions between C. albicans and S. gordonii under such conditions remains unknown. In this study, C. albicans and S. gordonii were cocultured in heart infusion broth with a low level of fermentable carbohydrate. Planktonic growth, biofilm formation, cell aggregation, and GH activities of monocultures and cocultures were examined. The results revealed that the planktonic growth of cocultured S. gordonii in a low-carbohydrate environment was elevated, while that of cocultured C. albicans was reduced. The biomass of S. gordonii in dual-species biofilms was higher than that of monocultures, while that of cocultured C. albicans was decreased. GH activity was observed in S. gordonii, and elevated activity of GHs was detected in S. gordonii-C. albicans cocultures, with elevated expression of GH-related genes of S. gordonii. By screening a mutant library of C. albicans, we identified a tec1Δ/Δ mutant strain that showed reduced ability to promote the growth and GH activities of S. gordonii compared with the wild-type strain. Altogether, the findings of this study demonstrate the involvement of GHs in the cross-kingdom metabolic interactions between C. albicans and S. gordonii in an environment with low level of fermentable carbohydrates. IMPORTANCE Cross-kingdom interactions between Candida albicans and oral streptococci such as Streptococcus gordonii have been reported. However, their interactions in a low-fermentable-carbohydrate environment like saliva is not clear. The current study revealed glycoside hydrolase-related cross-kingdom communications between S. gordonii and C. albicans under the low-fermentable-carbohydrate condition. We demonstrate that C. albicans can promote the growth and metabolic activities of S. gordonii by elevating the activities of cell-wall-anchored glycoside hydrolases of S. gordonii. C. albicans gene TEC1 is critical for this cross-kingdom metabolic communication.

The Microbiome in Periodontitis and Diabetes

Objectives

To perform a comprehensive and integrative review of the available literature on the potential changes in the microbiome of healthy and individuals with diabetes under periodontal health and disease.

Materials and Methods

The review was conducted by two independent reviewers. Indexed electronic databases (PubMed/Medline, Cochrane Library, Web of Science and Scopus) were searched, including articles published in English and dated from 5 years ago until December 2021. A manual search also was performed to identify co-related articles. Following the removal of duplicates and eligibility criteria, the articles were included in tables for analysis and described in the manuscript.

Results

According to this review, diabetes mellitus was associated with significant changes in the subgingival and salivary microbiome, either in its association with periodontitis or in cases of periodontal health. In addition to affecting microbial diversity in terms of taxonomy, metagenomic studies have shown that this endocrine disorder may also be directly related to increased pathogenicity in the oral microbiome.

Conclusion

Although the reviewed studies demonstrate important differences in the subgingival and salivary microbiome composition because of diabetes mellitus, further studies are needed to clarify the real effects of hyperglycemia on oral microbial profiles and support new diagnostic approaches and innovative treatments.

Efficient Antimicrobial Effect of Alginate-Catechol/Fe2+ Coating on Hydroxyapatite toward Oral Care Application

Reducing the formation of oral bacterial biofilms is critical to prevent common dental diseases. Though many strategies for restricting bacterial adhesion on tooth surfaces have been reported, a simple method for efficient oral bacteriostasis is still highly expected. Herein, we have proved a soft gel made of an alginate-catechol conjugate (SA-DA) and the ferrous cation (Fe²⁺) as an effective antibacterial coating on hydroxyapatite (HAP, a tooth model). As suggested by quartz crystal microbalance (QCM) measurements, SA-DA/Fe²⁺ coating possessed a high binding affinity to HAP without destruction by either immersion in artificial saliva or simulated tooth brushing. Significantly less protein (bovine serum albumin) and Streptococcus mutans (S. mutans, an oral bacterial model) could be found on HAP after coating with SA-DA/Fe²⁺, indicating that the prepared gel could resist well the adhesion of biofouling and microbes due to its hydrophilicity. Notably, such an antibacterial effect (around 70% S. mutans was inhibited) could be maintained for 3 d, which resulted from the extremely good stability of SA-DA/Fe²⁺ coating, as confirmed by QCM analysis. Our results may offer possibilities for developing applications in order to further improve oral hygiene.

Hurdle technology using encapsulated enzymes and essential oils to fight bacterial biofilms

Biofilm formation on abiotic surfaces has become a major public health concern because of the serious problems they can cause in various fields. Biofilm cells are extremely resistant to stressful conditions, because of their complex structure impedes antimicrobial penetration to deep-seated cells. The increased resistance of biofilm to currently applied control strategies underscores the urgent need for new alternative and/or supplemental eradication approaches. The combination of two or more methods, known as Hurdle technology, offers an excellent option for the highly effective control of biofilms. In this perspective, the use of functional enzymes combined with biosourced antimicrobial such as essential oil (EO) is a promising alternative anti-biofilm approach. However, these natural antibiofilm agents can be damaged by severe environmental conditions and lose their activity. The microencapsulation of enzymes and EOs is a promising new technology for enhancing their stability and improving their biological activity. This review article highlights the problems related to biofilm in various fields, and the use of encapsulated enzymes with essential oils as antibiofilm agents. KEY POINTS: • Problems associated with biofilms in the food and medical sectors and their subsequent risks on health and food quality. • Hurdle technology using enzymes and essential oils is a promising strategy for an efficient biofilms control. • The microencapsulation of enzymes and essential oils ensures their stability and improves their biological activities.

Cytotoxic effects of different detergent containing children's toothpastes on human gingival epithelial cells

Background

This study aimed to evaluate possible cytotoxic effects to gingival epithelial cells exposed to children toothpastes containing different detergent.

Methods

Tissues required for the isolation of human gingival epithelial cells were obtained by biopsy during the extraction of the impacted third molar tooth. Toothpaste solutions of different concentrations were prepared from five different children’s toothpastes with different detergent contents. Isolated gingival epithelial cells were stimulated with experimental groups consisting of toothpaste solutions (Colgate, Sensodyne, Splat, Nenedent, Perlodent) at different concentrations and a control group consisting of complete Dulbecco’s modified eagle medium. After the experiments, cell viability was evaluated using flow cytometry. 2 Way ANOVA was used to see the interaction effect of the main effects of toothpaste solution and concentration factors. Pairwise comparisons were made by Tukey post hoc tests. In the study, the significance level was taken as 0.05.

Results

As a result of the analysis, it was seen that the toothpaste solution and concentration factors and the interactions of these 2 factors were effective on the viable, early apoptotic, late apoptotic and necrotic cell rates. The statistically highest live cell ratios were detected in Splat’s toothpaste solutions (90.14% at 0.4% concentration) after the control group (90.82%) and the group with the lowest viability values was determined in Colgate group (75.74% at 0.4% concentration) (p < 0.05).

Conclusions

According to the results of the study, it was observed that toothpastes containing SLS affected the viability of cells more negatively than toothpastes with other detergent contents.

Oral biosciences: The annual review 2021

BACKGROUND

The Journal of Oral Biosciences is devoted to advancing and disseminating fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review features review articles in the fields of "Extracellular Vesicles," "Propolis," "Odontogenic Tumors," "Periodontitis," "Periodontium," "Flavonoids," "Lactoferrin," "Dental Plaque," "Anatomy," "Induced Pluripotent Stem Cells," "Bone Cell Biology," "Dysgeusia," "Dental Caries," and "Dental Pulp Cavity," in addition to the review article by the winners of the "Lion Award" ("Sox9 function in salivary gland development") presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews in the Journal of Oral Biosciences have inspired its readers to broaden their knowledge regarding various aspects of oral biosciences. The current editorial review introduces these exciting review articles.

Tyrosine Kinases and Phosphatases: Enablers of the Porphyromonas gingivalis Lifestyle

Tyrosine phosphorylation modifies the functionality of bacterial proteins and forms the basis of a versatile and tunable signal transduction system. The integrated action of tyrosine kinases and phosphatases controls bacterial processes important for metabolism and virulence. Porphyromonas gingivalis, a keystone pathogen in periodontal disease, possesses an extensive phosphotyrosine signaling network. The phosphorylation reaction is catalyzed by a bacterial tyrosine (BY) kinase, Ptk1, and a Ubiquitous bacterial Kinase UbK1. Dephosphorylation is mediated by a low-molecular-weight phosphatase, Ltp1 and a polymerase and histidinol phosphatase, Php1. Phosphotyrosine signaling controls exopolysaccharide production, gingipain activity, oxidative stress responses and synergistic community development with Streptococcus gordonii. Additionally, Ltp1 is secreted extracellularly and can be delivered inside gingival epithelial cells where it can override host cell signaling and readjust cellular physiology. The landscape of coordinated tyrosine kinase and phosphatase activity thus underlies the adaptive responses of P. gingivalis to both the polymicrobial environment of bacterial communities and the intracellular environment of gingival epithelial cells.

A Randomized, Double-Blind, Placebo-Controlled Clinical Trial of a Mouthwash Containing Glycyrrhiza uralensis Extract for Preventing Dental Caries

This study sought to confirm the effect of using a mouthwash containing Glycyrrhiza uralensis extract for oral health management by investigating changes in the pH of dental plaque and bacteria that cause dental caries. A randomized, double-blind, placebo-controlled study was conducted on 60 subjects categorized in either the Glycyrrhiza uralensis extract gargle group (n = 30) or the saline gargle group (n = 30). Scaling was conducted in order to ensure the homogeneity of the oral environment, while gargling was performed once daily before the subjects went to bed for 5 days based on the group. Caries activity was assessed using the Cariview test, while detection of the bacteria that cause dental caries was confirmed using microbiological analysis. All clinical measurements and evaluations were conducted by two trained dental hygienists under the supervision of a dentist. Based on the analysis of dental caries activity and dental caries-causing bacteria, the Glycyrrhiza uralensis extract gargle group showed a clear decrease in bacteria compared to the saline gargle group. Glycyrrhiza uralensis extract demonstrated no risk of tooth demineralization. It also showed excellent antibacterial activity through inhibition and effective reduction of bacteria that cause dental caries. Therefore, the mouthwash containing Glycyrrhiza uralensis extract is an effective oral care product suitable for use as an effective dental caries prevention agent.

Streptococcus gordonii DL1 evades polymorphonuclear leukocyte-mediated killing via resistance to lysozyme

Streptococcus gordonii is an etiological bacterial agent of infective endocarditis. Although the pathogenesis mechanisms are not well understood, the interaction between streptococci and phagocytes is considered important for the development of infective endocarditis. Previous studies show that some S. gordonii strains, including DL1, survive in polymorphonuclear leukocytes (PMNs), whereas other strains such as SK12 are sensitive to PMN-dependent killing. In this study, we assessed the differences between the sensitivity of S. gordonii DL1 and S. gordonii SK12 to PMN-dependent killing. S. gordonii DL1 showed a higher survival when treated with PMNs than SK12. Both S. gordonii DL1 and S. gordonii SK12 showed high resistance to low pH condition. Compared to S. gordonii SK12, S. gordonii DL1 was sensitive to hydrogen peroxide. However, the resistance of S. gordonii DL1 to the tested bactericidal agents, especially lysozyme, was higher than that of SK12. Furthermore, we performed a bactericidal assay by treating a mixture of S. gordonii DL1 and SK12 with PMNs. S. gordonii DL1 did not enhance the survival of S. gordonii SK12 exposed to PMNs. These results indicated that S. gordonii DL1 is resistant to bactericidal agents that degrade bacteria in phagolysosomes. In addition, there was no secretory factor involved in the resistance to bactericidal agents. The findings of this study may help develop treatments for infective endocarditis caused by S. gordonii.

Antimicrobial activity of a novel Spanish propolis against planktonic and sessile oral Streptococcus spp

Increased bacterial resistance to traditional antimicrobial agents has prompted the use of natural products with antimicrobial properties such as propolis, extensively employed since ancient times. However, the chemical composition of propolis extracts is extremely complex and has been shown to vary depending on the region and season of collection, due to variations in the flora from which the pharmacological substances are obtained, being therefore essential for their antimicrobial activity to be checked before use. For this purpose, we evaluate the in vitro antimicrobial and anti-biofilm activity of a new and promising Spanish ethanolic extract of propolis (SEEP) on Streptococcus mutans and Streptococcus sanguinis, responsible, as dominant 'pioneer' species, for dental plaque. Results reveal that S. sanguinis is more sensitive to SEEP, slowing and retarding its growth considerably with lower concentrations than those needed to produce the same effect in S. mutans. SEEP presents concentration- and time-dependent killing activity and, furthermore, some of the subinhibitory concentrations employed increased biofilm formation even when bacterial growth decreased. Mono and dual-species biofilms were also inhibited by SEEP. Findings obtained clearly show the relevance of using biofilm and subinhibitory concentration models to determine optimal treatment concentrations.

A review on natural teeth whitening

BACKGROUND

Discoloration of teeth occurs for various reasons. Common ingredients like substances from tea and coffee, as well as antibiotics like tetracycline, or food dyes, can percolate into the teeth, and, as such, these stains may persist in the porous structure of the enamel. Smoking is also contributory to dental discoloration, with toxins of tobacco smoke accumulating in a similar way. With aging, teeth tend to be discolored with accumulation of various stains in addition to the enamel gradually eroding to expose the yellow dentin.

HIGHLIGHT

This review focused on the effect of several natural ingredients with teeth-whitening properties and their daily clinical application. Metabolic dental bleaching mechanisms, as well as tooth discoloration and decay, were also reviewed. The current scientific literature (mostly from 2000 to 2020) was consolidated from manuscripts retrieved from Scopus, PubMed, ResearchGate, and Google Scholar.

CONCLUSION

Natural teeth whitening effectively lightens the natural color of teeth without eroding dental surfaces. On the other hand, commercially available whiteners containing hydrogen peroxide and carbamide peroxide, in high concentrations, can lead to deproteinization and demineralization of teeth through oxidation processes. If used extensively, these compounds may cause a number of adverse effects. Alternative natural teeth-whiteners include ingredients like lemons, strawberries, oranges, papaya, and other fruits. Such natural ingredients offer a milder and safer way of whitening teeth than whiteners containing hydrogen peroxide or carbamide peroxide.

Periodontal Disease: The Good, The Bad, and The Unknown

Periodontal disease is classically characterized by progressive destruction of the soft and hard tissues of the periodontal complex, mediated by an interplay between dysbiotic microbial communities and aberrant immune responses within gingival and periodontal tissues. Putative periodontal pathogens are enriched as the resident oral microbiota becomes dysbiotic and inflammatory responses evoke tissue destruction, thus inducing an unremitting positive feedback loop of proteolysis, inflammation, and enrichment for periodontal pathogens. Keystone microbial pathogens and sustained gingival inflammation are critical to periodontal disease progression. However, recent studies have revealed the importance of previously unidentified microbes involved in disease progression, including various viruses, phages and bacterial species. Moreover, newly identified immunological and genetic mechanisms, as well as environmental host factors, including diet and lifestyle, have been discerned in recent years as further contributory factors in periodontitis. These factors have collectively expanded the established narrative of periodontal disease progression. In line with this, new ideologies related to maintaining periodontal health and treating existing disease have been explored, such as the application of oral probiotics, to limit and attenuate disease progression. The role of systemic host pathologies, such as autoimmune disorders and diabetes, in periodontal disease pathogenesis has been well noted. Recent studies have additionally identified the reciprocated importance of periodontal disease in potentiating systemic disease states at distal sites, such as in Alzheimer's disease, inflammatory bowel diseases, and oral cancer, further highlighting the importance of the oral cavity in systemic health. Here we review long-standing knowledge of periodontal disease progression while integrating novel research concepts that have broadened our understanding of periodontal health and disease. Further, we delve into innovative hypotheses that may evolve to address significant gaps in the foundational knowledge of periodontal disease.