Non-conventional therapeutics for oral infections

Oral microbiota and metabolites: key players in oral health and disorder, and microbiota-based therapies

The review aimed to investigate the diversity of oral microbiota and its influencing factors, as well as the association of oral microbiota with oral health and the possible effects of dysbiosis and oral disorder. The oral cavity harbors a substantial microbial burden, which is particularly notable compared to other organs within the human body. In usual situations, the microbiota exists in a state of equilibrium; however, when this balance is disturbed, a multitude of complications arise. Dental caries, a prevalent issue in the oral cavity, is primarily caused by the colonization and activity of bacteria, particularly streptococci. Furthermore, this environment also houses other pathogenic bacteria that are associated with the onset of gingival, periapical, and periodontal diseases, as well as oral cancer. Various strategies have been employed to prevent, control, and treat these disorders. Recently, techniques utilizing microbiota, like probiotics, microbiota transplantation, and the replacement of oral pathogens, have caught the eye. This extensive examination seeks to offer a general view of the oral microbiota and their metabolites concerning oral health and disease, and also the resilience of the microbiota, and the techniques used for the prevention, control, and treatment of disorders in this specific area.

Efficacy of methylene blue-mediated antimicrobial photodynamic therapy on clinical and radiographic outcomes among patients with periodontal diseases: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This study aimed to assess the influence of methylene blue (MB)-mediated adjunctive antimicrobial photodynamic therapy (aPDT) when compared to conventional mechanical debridement (MD) alone on periodontal clinical and radiographic outcomes among periodontitis patients.

METHODS

Randomized clinical trials (RCTs) were incorporated by conducting an electronic search in Web of Science, Scopus, and PubMed for articles published in English up to August 2023 to address the following focused question based on the PICO format: "Whether the application of MB-mediated aPDT as an adjunctive to MD (Intervention) leads to improved periodontal clinical and/or radiographic outcomes (Outcome) among participants with and without periodontal diseases (Population) as compared to MD alone (Conparison)". The risk of bias (RoB) of the included studies was assessed using the modified Jadad scale. A meta-analysis was conducted, and it included the presentation of the standard mean difference (SMD) along with a 95 % confidence interval (CI).

RESULTS

In total, 11 studies were included in this systematic review and meta-analysis. The meta-analysis demonstrated statistically significant improvements in periodontal plaque index (SMD: -0.72 % [95 % CI: -0.99 % to -0.45 %]; p<0.00001), probing depth (SMD: -0.38 % [95 % CI: -0.57 % to -0.19 %; p<0.00001), and bleeding on probing (SMD: -0.44 % [95 % CI: -0.68 % to -0.20 %]; p = 0.0003) scores at the final follow-up visit after the application of MB-mediated aPDT in comparison with MD alone. Nevertheless, there was no statistically significant difference was observed in periodontal clinical attachment level values (SMD: -0.01 % [95 % CI: -0.21 % to 0.19 %]; p = 0.95) between the control group and the experimental group. Six studies achieved a low RoB, five were rated as having medium RoB, while no study received a high RoB.

CONCLUSION

MB-mediated aPDT, when used as an adjunct to conventional MD contributes to the improvement of periodontal clinical outcomes including PI, PD, and BOP in patients with periodontitis.

Mechanism of Action of Streptococcus downii, a New Bacterial Species with Probiotic Potential

Streptococcus downii is a recently reported bacterial species of oral origin, with inhibitory capacity against Streptococcus mutans, Actinomyces naeslundii, Veillonella parvula and Aggregatibacter actinomycetemcomitans, which confers upon it the potential of being an oral probiotic. The aim of the present study was to identify the potential mechanisms by which S. downii exerts its inhibitory effect on S. mutans. To this end, the study assessed the consumption of glucose and proteins available in the culture medium, the modification of the pH, the production of short-chain fatty acids, the changes in the protein panel of the inhibition halo, the production of hydrogen peroxide and the effect of proteinase K. There were no differences in the glucose values or in the protein content of the medium, but there was a reduction in pH (with no effect on the growth of S. mutans). Significant increases were detected in the levels of lactic and formic acid (with no effect on the growth of S. mutans), as well as changes in the peptide panel (with no effect on the growth of S. mutans). The inhibitory effect was maintained in the presence of peroxidase but disappeared after adding proteinase K. Based on these results, it is suggested that the main mechanism of inhibition of S. downii against S. mutans is the production of bacteriocins.

Evaluating Alterations of the Oral Microbiome and Its Link to Oral Cancer among Betel Quid Chewers: Prospecting Reversal through Probiotic Intervention

Areca nut and slaked lime, with or without tobacco wrapped in Piper betle leaf, prepared as betel quid, is extensively consumed as a masticatory product in many countries across the world. Betel Quid can promote the malignant transformation of oral lesions as well as trigger benign cellular and molecular changes. In the oral cavity, it causes changes at the compositional level in oral microbiota called dysbiosis. This dysbiosis may play an important role in Oral Cancer in betel quid chewers. The abnormal presence and increase of bacteria Fusobacterium nucleatum, Capnocytophaga gingivalis, Prevotella melaninogenica, Peptostreptococcus sp., Porphyromonas gingivalis, and Streptococcus mitis in saliva and/or other oral sites of the cancer patients has attracted frequent attention for its association with oral cancer development. In the present review, the authors have analysed the literature reports to revisit the oncogenic potential of betel quid and oral microbiome alterations, evaluating the potential of oral microbiota both as a driver and biomarker of oral cancer. The authors have also shared a perspective that the restoration of local microbiota can become a potentially therapeutic or prophylactic strategy for the delay or reversal of lip and oral cavity cancers, especially in high-risk population groups.

Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue

The delivery of safe, visible wavelengths of light can be an effective, pathogen-agnostic, countermeasure that would expand the current portfolio of SARS-CoV-2 intervention strategies beyond the conventional approaches of vaccine, antibody, and antiviral therapeutics. Employing custom biological light units, that incorporate optically engineered light-emitting diode (LED) arrays, we harnessed monochromatic wavelengths of light for uniform delivery across biological surfaces. We demonstrated that primary 3D human tracheal/bronchial-derived epithelial tissues tolerated high doses of a narrow spectral band of visible light centered at a peak wavelength of 425 nm. We extended these studies to Vero E6 cells to understand how light may influence the viability of a mammalian cell line conventionally used for assaying SARS-CoV-2. The exposure of single-cell monolayers of Vero E6 cells to similar doses of 425 nm blue light resulted in viabilities that were dependent on dose and cell density. Doses of 425 nm blue light that are well-tolerated by Vero E6 cells also inhibited infection and replication of cell-associated SARS-CoV-2 by > 99% 24 h post-infection after a single five-minute light exposure. Moreover, the 425 nm blue light inactivated cell-free betacoronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner. Importantly, clinically applicable doses of 425 nm blue light dramatically inhibited SARS-CoV-2 infection and replication in primary human 3D tracheal/bronchial tissue. Safe doses of visible light should be considered part of the strategic portfolio for the development of SARS-CoV-2 therapeutic countermeasures to mitigate coronavirus disease 2019 (COVID-19).

Antimicrobial and Antibiofilm Activity of the Probiotic Strain Streptococcus salivarius K12 against Oral Potential Pathogens

Oral probiotics are increasingly used in the harmonization of the oral microbiota in the prevention or therapy of various oral diseases. Investigation of the antimicrobial activity of the bacteriocinogenic strain Streptococcus salivarius K12 against oral pathogens shows promising results, not only in suppressing growth, but also in eliminating biofilm formation. Based on these findings, we decided to investigate the antimicrobial and antibiofilm activity of the neutralized cell-free supernatant (nCFS) of S. salivarius K12 at various concentrations against selected potential oral pathogens under in vitro conditions on polystyrene microtiter plates. The nCFS of S. salivarius K12 significantly reduced growth (p < 0.01) in Streptococcus mutans Clarke with increasing concentration from 15 to 60 mg/mL and also in Staphylococcus hominis 41/6 at a concentration of 60 mg/mL (p < 0.001). Biofilm formation significantly decreased (p < 0.001) in Schaalia odontolytica P10 at nCFS concentrations of 60 and 30 mg/mL. Biofilm inhibition (p < 0.001) was also observed in Enterobacter cloacae 4/2 at a concentration of 60 mg/mL. In Schaalia odontolytica P10 and Enterobacter cloacae 4/2, the nCFS had no effect on their growth.

A Review of the Role of Probiotic Supplementation in Dental Caries

Dental diseases are among the common health issues experienced around the world. Dental caries is one of the most predominant oral diseases worldwide. Major factors associated with caries development include poor oral hygiene, the content of specific carbohydrates in the diet, dental biofilm formation, the cariogenic microbial load, reduction in salivary flow, insufficient fluoride exposure, gingival recession, genetic factors, and lack of personal attention to one's dental health. Several preventive measures have been implemented to reduce the risk of the development of caries. Probiotics are live microbes that when administered in suitable amounts confer health benefits on the host; they are recognized as potential adjunct therapeutic agents for several diseases. The present manuscript summarizes recent findings on the role of probiotics in dental caries prevention and the possible mechanisms of probiotic effects. Review of the literature indicates the regular consumption of probiotic products significantly reduced the risk of caries by inhibiting cariogenic bacteria and enriching commensal microbes in the oral cavity. Buffering the salivary pH, production of bacteriocin and enzymes (dextranase, mutanase, and urease), the capacity of competing for the adhesion and colonization on tooth surfaces are the possible mechanisms behind the beneficial effect of probiotics. Further studies are necessary to address the efficacy of long-term probiotic supplementation on the control of dental diseases and the influence of childhood probiotic supplementation on the risk of caries development.

Effect of probiotics on gingival inflammation and oral microbiota: A meta-analysis

To evaluate the effect of probiotics on gingival inflammation and oral microbiota in patients suffering from plaque-induced gingivitis. PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE were electronically searched until December 2020. The quality of included studies was assessed with the Cochrane Collaboration's Risk of Bias tool. The differences were expressed as weighted mean differences (WMD) and 95% of confidence interval (95% CI). I² test was performed to evaluate the heterogeneity of the studies. All analyses were performed using Review Manager (version 5.3). Eleven randomized and controlled trials were included, enrolling 554 patients. All comparisons displayed that oral probiotics had no significant improvement in the Gingival Index (GI), Plaque Index (PI), and bleeding on probing (BOP) of patients with plaque-induced gingivitis. In terms of microecology, no significant difference in the volumes of gingival crevicular fluid (GCF), the concentration of IL-1β, and the counts of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), and Fusobacterium nucleatum (Fn) were found between the probiotic group and the placebo group. There exists no clear evidence that oral probiotics have positive effect on gingival inflammation and oral microecological environment of patients with plaque-induced gingivitis.

Current status and future of delivery systems for prevention and treatment of infections in the oral cavity

Oral health reflects the general health, and it is fundamental to well-being and quality of life. An infection in the oral cavity can be associated with serious complications in human health. Local therapy of these infections offers many advantages over systemic drug administration, targeting directly to the diseased area while minimizing systemic side effects. Specialized drug delivery systems into the oral cavity have to be designed in such a fashion that they resist to the aqueous environment that is constantly bathed in saliva and subject to mechanical forces. Additionally, a prolonged release of drug should also be provided, which would enhance the efficacy and also decrease the repeated dosing. This review is aimed to summarize the current most relevant findings related to local drug delivery of various drug groups for prevention and treatment of infections (viral, bacterial, fungal) and infection-related manifestations in the oral cavity. Current therapeutic challenges in regard to effective local drug delivery systems will be discussed, and the recent approaches to overcome these obstacles will be reviewed. Finally, future prospects will be overviewed to promote novel strategies that can be implemented in clinical management for prevention and treatment of oral infections.

Effects of a tart cherry (Prunus cerasus L.) phenolic extract on Porphyromonas gingivalis and its ability to impair the oral epithelial barrier

Periodontal diseases, including gingivitis and periodontitis, are a global oral health problem. Porphyromonas gingivalis, a key pathogen involved in the onset of periodontitis, is able to colonize the subgingival epithelium and invade the underlying connective tissue due to the contribution of cysteine proteases known as gingipains. In this study, we investigated the effects of a phenolic extract prepared from tart cherry (Prunus cerasus L.) juice on the growth, adherence, and protease activity of P. gingivalis. We also assessed the protective effect of the tart cherry extract on the disruption of the oral epithelial barrier induced by P. gingivalis. The tart cherry extract that contains procyanidins and quercetin and its derivatives (rutinoside, glucoside) as the most important phenolic compounds attenuated P. gingivalis growth, reduced adherence to an experimental basement membrane matrix model, and decreased the protease activities of P. gingivalis. The tart cherry extract also exerted a protective effect on the integrity of the oral epithelial barrier in an in vitro model infected with P. gingivalis. More specifically, the extract prevented a decrease in transepithelial electrical resistance as well as the destruction of tight junction proteins (zonula occludens-1 and occludin). These results suggest that the tart cherry phenolic extract may be a promising natural product for the treatment of periodontitis through its ability to attenuate the virulence properties of P. gingivalis and curtail the ability of this pathogen to impair the oral epithelial barrier.

Focal Infection and Periodontitis: A Narrative Report and New Possible Approaches

The "focal infection theory" is a historical concept based on the assumption that some infections may cause chronic and acute diseases in different districts of the body. Its great popularity spanned from 1930 to 1950 when, with the aim to remove all the foci of infection, drastic surgical interventions were performed. Periodontitis, a common oral pathology mainly of bacterial origin, is the most evident example of this phenomenon today: in fact, bacteria are able to migrate, develop and cause health problems such as cardiovascular and respiratory diseases, diabetes, and osteoporosis. The aim of this narrative report is to verify the hypothesis of the association between oral infections and systemic diseases by different ways of approach and, at the same time, to propose new kinds of treatment today made possible by technological progress. The analysis of the literature demonstrated a strong relationship between these conditions, which might be explained on the basis of the recent studies on microbiota movement inside the body. Prevention of the oral infections, as well as of the possible systemic implications, may be successfully performed with the help of new technologies, such as probiotics and laser.

The Impact of Photosensitizer Selection on Bactericidal Efficacy Of PDT against Cariogenic Biofilms: A Systematic Review and Meta-Analysis

BACKGROUND

There are investigations on multiple photosensitizers for modulation of caries-related biofilms using PDT. However, much controversy remains about recommended parameters mostly on the selection of an efficient photosensitizer.

OBJECTIVE

The study performed a systematic review to identify the answer to the following question: What photosensitizers present high bactericidal efficacy against cariogenic biofilms?

METHODS

Systematic review with meta-analyses were carried out for English language articles from October to December 2019 (PRISMA standards) using MEDLINE, Scopus, Biomed Central, EMBASE, LILACS, and Web of Science. Information on study design, biofilm model, photosensitizer, light source, energy delivery, the incubation time for photosensitizer, and bacterial reduction outcomes were recorded. We performed two meta-analyses to compare bacterial reduction, data was expressed by (1) base 10 Logarithm values and (2) Log reduction RESULTS: After the eligibility criteria were applied (PEDro scale), the selected studies showed that toluidine Blue Ortho (TBO) and methylene blue (MBO) (5-min incubation time and 5-min irradiation) demonstrated better bacterial reduction outcomes. For the data expressed by Log TBO, MBO, curcumin, and Photogem® presented a significant bacterial decrease in comparison to the control (p = 0.042). For the data represented by Log reduction, the bacterial reduction toward S.mutans was not significant for any photosensitizer (p = 0.679).

CONCLUSION

The lack of methodological standardization among the studies still hinders the establishment of photosensitizer and bactericidal efficiency. TBO, MBO, curcumin, and photogem generate greater PDT-based bacterial reduction on caries-related bacteria.. Further clinical studies are necessary in order to obtain conclusive results.

Rapid Release Polymeric Fibers for Inhibition of Porphyromonas gingivalis Adherence to Streptococcus gordonii

Active agents targeting key bacterial interactions that initiate biofilm formation in the oral cavity, may alter periodontitis progression; however, to date, specifically-targeted prophylactic and treatment strategies have been limited. Previously we developed a peptide, BAR (SspB Adherence Region), that inhibits oral P. gingivalis/S. gordonii biofilm formation in vitro and in vivo, and BAR nanoparticles that increase BAR effectiveness via multivalency and prolonged delivery. However, limited BAR loading and nanoparticle retention in the oral cavity can result in inadequate release and efficaciousness. Given this, an effective delivery platform that can release concentrations of BAR suitable for twice-daily applications, may offer an alternative that enhances loading, ease of administration, and retention in the oral cavity. With this in mind, the study objectives were to develop and characterize a rapid-release platform, composed of polymeric electrospun fibers (EFs) that encapsulate BAR, and to evaluate fiber safety and functionality against P. gingivalis/S. gordonii biofilms in vitro. Poly(lactic-co-glycolic acid) (PLGA), poly(L-lactic acid) (PLLA), and polycaprolactone (PCL) were electrospun alone or blended with polyethylene oxide (PEO), to provide high BAR loading and rapid-release. The most promising formulation, 10:90 PLGA:PEO EFs, provided 95% BAR release after 4 h, dose-dependent inhibition of biofilm formation (IC50 = 1.3 μM), disruption of established dual-species biofilms (IC50 = 2 μM), and maintained high cell viability. These results suggest that BAR-incorporated EFs may provide a safe and specifically-targeted rapid-release platform to inhibit and disrupt dual-species biofilms, that we envision may be applied twice-daily to exert prophylactic effect in the oral cavity.

Nanoparticles for the Treatment of Oral Biofilms: Current State, Mechanisms, Influencing Factors, and Prospects

Due to their excellent size, designability, and outstanding targeted antibacterial effects, nanoparticles have become a potential option for controlling oral biofilm-related infections. However, the formation of an oral biofilm is a dynamic process, and factors affecting the performance of antibiofilm treatments are complex. As such, when examining the existing literature on the antibiofilm effects of nanoparticles, attention should be paid to the specific mechanisms of action at different stages of oral biofilm formation, as well as relevant influencing factors, in order to achieve an objective and comprehensive evaluation. This review is intended to detail the antibacterial mechanisms of nanoparticles during the four stages of the formation of oral biofilms: 1) acquired film formation; 2) bacterial adhesion; 3) early biofilm development; and 4) biofilm maturation. In addition, factors influencing the antibiofilm properties of nanoparticles are summarized from the aspects of nanoparticles themselves, biofilm models, and host factors. The limitations of current research and possible trends for future research are also discussed. In summary, nanoparticles are a promising antioral biofilm strategy. It is hoped that this review can serve as a reference and inspire ideas for further research on the application of nanoparticles for effectively targeting and treating oral biofilms.

Functional assessment of peptide-modified PLGA nanoparticles against oral biofilms in a murine model of periodontitis

The interaction of the periodontal pathogen Porphyromonas gingivalis (Pg) with commensal streptococci promotes Pg colonization of the oral cavity. Previously, we demonstrated that a peptide (BAR) derived from Streptococcus gordonii (Sg) potently inhibited adherence of Pg to streptococci and reduced Pg virulence in a mouse model of periodontitis. Thus, BAR may represent a novel therapeutic to control periodontitis by preventing Pg colonization of the oral cavity. However, while BAR inhibited the initial formation of Pg/Sg biofilms, much higher concentrations of peptide were required to disrupt an established Pg/Sg biofilm. To improve the activity of the peptide, poly(lactic-co-glycolic acid) (PLGA) nanoparticles were surface-modified with BAR and shown to more potently disrupt Pg/Sg biofilms relative to an equimolar amount of free peptide. The goal of this work was to determine the in vivo efficacy of BAR-modified NPs (BNPs) and to assess the toxicity of BNPs against human gingival epithelial cells. In vivo efficacy of BNPs was assessed using a murine model of periodontitis by measuring alveolar bone resorption and gingival IL-17 expression as outcomes of Pg-induced inflammation. Infection of mice with Pg and Sg resulted in a significant increase in alveolar bone loss and gingival IL-17 expression over sham-infected animals. Treatment of Pg/Sg infected mice with BNPs reduced bone loss and IL-17 expression almost to the levels of sham-infected mice and to a greater extent than treatment with an equimolar amount of free BAR. The cytotoxicity of the maximum concentration of BNPs and free BAR used in in vitro and in vivo studies (1.3 and 3.4 μM), was evaluated in telomerase immortalized gingival keratinocytes (TIGKs) by measuring cell viability, cell lysis and apoptosis. BNPs were also tested for hemolytic activity against sheep erythrocytes. TIGKs treated with BNPs or free BAR demonstrated >90% viability and no significant lysis or apoptosis relative to untreated cells. In addition, neither BNPs nor free BAR exhibited hemolytic activity. In summary, BNPs were non-toxic within the evaluated concentration range of 1.3-3.4 μM and provided more efficacious protection against Pg-induced inflammation in vivo, highlighting the potential of BNPs as a biocompatible platform for translatable oral biofilm applications.

[The effect of probiotics on the secretory immunity of saliva in patients with type 2 diabetes]

To study the effect of the use of probiotics on the state of mucosal immunity in patients with type 2 diabetes. Evaluation of the results was carried out based on immunological parameters of the saliva of 50 patients suffering from type 2 diabetes with moderate periodontitis, before and 1 month after taking a probiotic complex based on Lactobacillus. In the salivary fluid of patients, a decrease in the concentration of pro-inflammatory cytokines IL-1β, TNF-α and IL-8 was noted, while an increase in the anti-inflammatory cytokine IL-10 was observed. An increase in local mucosal immunity was also observed, manifested in an increase in the synthesis of secretory immunoglobulin A.

Análise da atividade antimicrobiana de probióticos e sua adesividade a bráquetes ortodônticos: estudo in vitro

Resumo Introdução A presença de aparelho ortodôntico fixo dificulta a higienização e potencializa o acúmulo de biofilme bacteriano nas superfícies dentárias. O desenvolvimento de produtos que minimize isso é desejo de pesquisadores em todo o mundo. Objetivo Verificar a ação bacterapêutica de produtos lácteos contendo ou não probióticos sob pool de Streptococcus mutans (SM) (ATCC 25175) e S salivarius (SS) (ATCC 7073), além da adesão desses produtos à superfície de bráquetes ortodônticos. Material e método Pool de cepas ATCC de SM e SS foi formado e plaqueado sobre placa de Petri contendo meio de cultura brain heart infusion ágar (BHI). Após formação do meio, um orifício foi feito no centro da placa seguido do seu preenchimento com 150 µL dos produtos a serem testados, formando os seguintes grupos: GL - Leite bovino; GLP - Leite bovino com probiótico; GLF - Leite fermentado; e GLFP - Leite fermentado com probiótico. Na sequência, as placas foram incubadas por 48h, em estufa a 37ºC. A seguir, foi feita a medição do halo formado entre o produto e o meio com régua milimetrada. Já no disco de membrana, foi formado biofilme com o mesmo pool de cepas, sob discos de membrana. Em seguida, foi feita a diluição seriada contendo o produto de acordo com o grupo: P1 (água); P2 (L); P3 (LP); P4 (LFP), seguida do plaqueamento e a contagem total de micro-organismos. Para a adesividade dos produtos lácteos, bráquetes ortodônticos foram submergidos em cada solução (GL, GLP, GLF e GLFP) e foram incubadas a 37°C/24h. Posteriormente, cada bráquete foi transferido para um ependorf contendo solução salina estéril, que foi submetida a diluições seriadas, posteriormente incubadas a 37°C/48h sob microaerofilia para contagem das UFC/mL. Para análise dos dados, utilizaram-se os testes Levene, Shapiro-Wilk e Kruskal-Wallis. O nível de significância adotado foi de 5% (α = 0,05). Resultado Não houve formação de halo de inibição entre os produtos e o meio de cultura (p<0,05); no disco de membrana, não foram observadas diferenças estatísticas entre os grupos (p=0,679); os grupos tratados com leite bovino com probiótico e leite fermentado com probiótico apresentaram adesividade aos bráquetes ortodônticos (p=0,056). Conclusão Os achados do presente estudo permitem concluir que, em estudos in vitro, não foi possível verificar a bacterioterapia a partir de produtos lácteos contendo ou não probióticos em cepas de SM e SS.

Nanoparticles and the control of oral biofilms

Nanoparticles, novel in size, shape, and surface chemistry when compared to more conventional materials, offer additional functional properties to a range of possible oral applications, from drug-delivery systems to dental implant coatings. Exploitation of the toxic properties of nanoparticles to bacteria, viruses, and fungi has increased markedly over recent years. Metal and metal oxide nanoparticles and their incorporation into other materials have been of particular interest. The potential of nanoparticles to control the formation of biofilms within the oral cavity, as a function of their antimicrobial, anti-adhesive, and delivery capabilities, is coming under close scrutiny. However, optimum formulation of materials at the nanoscale does require innovative physical and chemical approaches.

BAR-encapsulated nanoparticles for the inhibition and disruption of Porphyromonas gingivalis-Streptococcus gordonii biofilms

Background

Porphyromonas gingivalis adherence to oral streptococci is a key point in the pathogenesis of periodontal diseases (Honda in Cell Host Microbe 10:423–425, 2011). Previous work in our groups has shown that a region of the streptococcal antigen denoted BAR (SspB Adherence Region) inhibits P. gingivalis/S. gordonii interaction and biofilm formation both in vitro and in a mouse model of periodontitis (Daep et al. in Infect Immun 74:5756–5762, 2006; Daep et al. in Infect immun 76:3273–3280, 2008; Daep et al. in Infect Immun 79:67–74, 2011). However, high localized concentration and prolonged exposure are needed for BAR to be an effective therapeutic in the oral cavity.

Methods

To address these challenges, we fabricated poly(lactic-co-glycolic acid) (PLGA) and methoxy-polyethylene glycol PLGA (mPEG-PLGA) nanoparticles (NPs) that encapsulate BAR peptide, and assessed the potency of BAR-encapsulated NPs to inhibit and disrupt in vitro two-species biofilms. In addition, the kinetics of BAR-encapsulated NPs were compared after different durations of exposure in a two-species biofilm model, against previously evaluated BAR-modified NPs and free BAR.

Results

BAR-encapsulated PLGA and mPEG-PLGA NPs potently inhibited biofilm formation (IC50 = 0.7 μM) and also disrupted established biofilms (IC50 = 1.3 μM) in a dose-dependent manner. In addition, BAR released during the first 2 h of administration potently inhibits biofilm formation, while a longer duration of 3 h is required to disrupt pre-existing biofilms.

Conclusions

These results suggest that BAR-encapsulated NPs provide a potent platform to inhibit (prevent) and disrupt (treat) P. gingivalis/S. gordonii biofilms, relative to free BAR.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0396-4) contains supplementary material, which is available to authorized users.

Nanomaterials in dentistry: a cornerstone or a black box?

Aim: The studies on tooth structure provided basis for nanotechnology-based dental treatment approaches known as nanodentistry which aims at detection and treatment of oral pathologies, such as dental caries and periodontal diseases, insufficiently being treated by conventional materials or drugs. This review aims at defining the role of nanodentistry in the medical area, its potential and hazards. Materials & methods: To validate these issues, current literature on nanomaterials for dental applications was critically reviewed. Results: Nanomaterials for teeth restoration, bone regeneration and oral implantology exhibit better mechanical properties and provide more efficient esthetic outcome. However, still little is known about influence of long-term function of such biomaterials in the living organism. Conclusion: As application of nanomaterials in industry and medical-related sciences is still expanding, more information is needed on how such nano-dental materials may interfere with oral cavity, GI tract and general health.

Ecological Approaches to Dental Caries Prevention: Paradigm Shift or Shibboleth?

Contemporary paradigms of dental caries aetiology focus on the ecology of the dental plaque biofilm and how local environmental factors can modulate this to cause disease. The crucial role that a healthy oral microbiome plays in preventing caries and promoting oral health is also being increasingly recognized. Based on these concepts, several ecological preventive approaches have been developed that could potentially broaden the arsenal of currently available caries-preventive measures. Many of these ecological approaches aim for long-term caries control by either disrupting cariogenic virulence factors without affecting bacterial viability, or include measures that can enhance the growth of health-associated, microbially diverse communities in the oral microbiome. This paper argues for the need to develop ecological preventive measures that go beyond conventional caries-preventive methods, and discusses whether these ecological approaches can be effective in reducing the severity of caries by promoting stable, health-associated oral biofilm communities.

Use of Probiotics and Oral Health

PURPOSE OF REVIEW

The purpose of this study is to critically assess recent studies concerning the use of probiotics to control periodontal diseases, dental caries and halitosis (oral malodour).

RECENT FINDINGS

Clinical studies have shown that probiotics when allied to conventional periodontal treatment can ameliorate microbial dysbiosis and produce significant improvement in clinical indicators of disease. However, this effect is often not maintained by the host after the end of probiotic use. Current probiotics also show limited effects in treating caries and halitosis. Novel approaches based up on replacement therapy and using highly abundant health-associated oral species, including nitrate-reducing bacteria, have been proposed to improve persistence of probiotic strains and maintain oral health benefits.

SUMMARY

Probiotics have potential in the management of multifactorial diseases such as the periodontal diseases and caries, by more effectively addressing the host-microbial interface to restore homeostasis that may not be achieved with conventional treatments.

Influence of Oral and Gut Microbiota in the Health of Menopausal Women

Sex differences in gut microbiota are acknowledged, and evidence suggests that gut microbiota may have a role in higher incidence and/or severity of autoimmune diseases in females. Additionally, it has been suggested that oral, vaginal, and gut microbiota composition can be regulated by estrogen levels. The association of vaginal microbiota with vulvovaginal atrophy at menopause is well described in the literature. However, the relevance of oral and gut microbiota modulation in the immune system during estrogen deficiency and its effect on inflammatory diseases is not well explored. Estrogen deficiency is a condition that occurs in menopausal women, and it can last approximately 30 years of a woman’s life. The purpose of this mini- review is to highlight the importance of alterations in the oral and gut microbiota during estrogen deficiency and their effect on oral and inflammatory diseases that are associated with menopause. Considering that hormone replacement therapy is not always recommended or sufficient to prevent or treat menopause-related disease, we will also discuss the use of probiotics and prebiotics as an option for the prevention or treatment of these diseases.

Insight into Oral Biofilm: Primary, Secondary and Residual Caries and Phyto-Challenged Solutions

INTRODUCTION

Dental caries is known to be one of the most widespread, chronic infections affecting all ages and populations worldwide. The plethora of oral microbial population paves way for various endogenous infections and plays a crucial role in polymicrobial interactions contributing to biofilm-mediated diseases like caries and periodontal diseases.

METHODS

Extensive literature survey was conducted using the scientific databases like PubMed, Google scholar, Science Direct, etc. using the key words like dental caries, orodental infections, dental microbes, dental biofilm, secondary caries, phytotherapy, etc. The literature was analyzed thoroughly and critical review was performed.

RESULTS

The risk of development of secondary caries and residual caries further results in treatment failure. Drug resistance developed by oral microbes and further side effects pose serious hurdles in the current therapeutic strategies. The hyperactivities of various MMPs and the resulting massive ECM degradation are the challenging part in the design of effective therapeutic approaches. Anticariogenic phytotherapy is well appreciated owing to lesser side effects and versatility of their action. But appreciable outcomes regarding the phytochemical bioavailability and bioretention are still challenging. Site-specific delivery of phytoagents at the infected site may enhance the efficiency of these drugs. Accordingly emerging phytodentistry can be promising for the management of secondary and residual caries.

CONCLUSION

This article presents major cariogens and their mechanisms in initiating and aggravating dental caries. Effectiveness of phytotherapy and different mode of action of phytochemicals against cariogens are outlined. The article also raises major concerns and possibilities of phytochemical based therapeutics to be applied in the clinical arena of caries management.

Peptide-modified nanoparticles inhibit formation of Porphyromonas gingivalis biofilms with Streptococcus gordonii

PURPOSE

The interaction of Porphyromonas gingivalis with commensal streptococci promotes P. gingivalis colonization of the oral cavity. We previously showed that a synthetic peptide (BAR) derived from Streptococcus gordonii potently inhibited the formation of P. gingivalis/S. gordonii biofilms (IC₅₀ =1.3 µM) and reduced P. gingivalis virulence in a mouse model of periodontitis. Thus, BAR represents a novel therapeutic to control periodontitis by limiting P. gingivalis colonization of the oral cavity. Here, we sought to develop drug-delivery vehicles for potential use in the oral cavity that comprise BAR-modified poly(lactic-co-glycolic)acid (PLGA) nanoparticles (NPs).

METHODS

PLGA-NPs were initially modified with palmitylated avidin and subsequently conjugated with biotinylated BAR. The extent of BAR modification was quantified using a fluorescent-labeled peptide. Inhibition of P. gingivalis adherence to S. gordonii by BAR-modified NPs was compared with free peptide using a two-species biofilm model.

RESULTS

BAR-modified NPs exhibited an average size of 99±29 nm and a more positive surface charge than unmodified NPs (zeta potentials of -7 mV and -25 mV, respectively). Binding saturation occurred when 37 nmol BAR/mg of avidin-NPs was used, which resulted in a payload of 7.42 nmol BAR/mg NPs. BAR-modified NPs bound to P. gingivalis in a dose-dependent manner and more potently inhibited P. gingivalis/S. gordonii adherence and biofilm formation relative to an equimolar amount of free peptide (IC₅₀ of 0.2 µM versus 1.3 µM). BAR-modified NPs also disrupted the preformed P. gingivalis/S. gordonii biofilms more effectively than free peptide. Finally, we demonstrate that BAR-modified NPs promoted multivalent association with P. gingivalis, providing an explanation for the increased effectiveness of NPs.

CONCLUSION

These results indicate that BAR-modified NPs deliver a higher local dose of peptide and may represent a more effective therapeutic approach to limit P. gingivalis colonization of the oral cavity compared to treatment with formulations of free peptide.

Probiotics and Disease: A Comprehensive Summary-Part 5, Respiratory Conditions of the Ears, Nose, and Throat

This article series provides a literature review of the disease-specific probiotic strains studied in published clinical trials in humans and animals. The goal of the series is to provide clinically useful tools. The table design allows for quick access to supportive data and will be helpful as a guide for both researchers and clinicians. The first article (part 1) focused on mental health and neurological conditions and the second article (part 2) explored cultured and fermented foods that are commonly available in the United States. The third article (part 3) explored the relationship between bacterial strains and 2 of the most prevalent diseases we have in modern society, cardiometabolic disease and fatigue syndromes. The fourth article (part 4) elucidated the role of the microbiome in infectious diseases, and this fifth article (part 5) investigates probiotic strains on respiratory conditions that affect the ears, nose, and throat. Future articles will review conditions related to autoimmunity and dermatological conditions; the influence of the microbiome on cancer development and prognosis; gastrointestinal and genitourinary diseases associated with dysbiosis conditions; followed by an article focused on probiotic supplements. This literature review is specific to disease condition, probiotic classification, and individual strain.

A novel antimicrobial peptide against dental-caries-associated bacteria

Dental caries, a highly prevalent oral disease, is primarily caused by pathogenic bacteria infection, and most of them are anaerobic. Herein, we investigated the activity of a designed antimicrobial peptide ZXR-2, and found it showed broad-spectrum activity against a variety of Gram-positive and Gram-negative oral bacteria, particularly the caries-related taxa Streptococcus mutans. Time-course killing assays indicated that ZXR-2 killed most bacterial cells within 5 min at 4 × MIC. The mechanism of ZXR-2 involved disruption of cell membranes, as observed by scanning electron microscopy. Moreover, ZXR-2 inhibited the formation of S. mutans biofilm, but showed limited hemolytic effect. Based on its potent antimicrobial activity, rapid killing, and inhibition of S. mutans biofilm formation, ZXR-2 represents a potential therapeutic for the prevention and treatment of dental caries.

High‑throughput sequencing analyses of oral microbial diversity in healthy people and patients with dental caries and periodontal disease

Recurrence of oral diseases caused by antibiotics has brought about an urgent requirement to explore the oral microbial diversity in the human oral cavity. In the present study, the high-throughput sequencing method was adopted to compare the microbial diversity of healthy people and oral patients and sequence analysis was performed by UPARSE software package. The Venn results indicated that a mean of 315 operational taxonomic units (OTUs) was obtained, and 73, 64, 53, 19 and 18 common OTUs belonging to Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria, respectively, were identified in healthy people. Moreover, the reduction of Firmicutes and the increase of Proteobacteria in the children group, and the increase of Firmicutes and the reduction of Proteobacteria in the youth and adult groups, indicated that the age bracket and oral disease had largely influenced the tooth development and microbial development in the oral cavity. In addition, the traditional ‘pathogenic bacteria’ of Firmicutes, Proteobacteria and Bacteroidetes (accounted for >95% of the total sequencing number in each group) indicated that the ‘harmful’ bacteria may exert beneficial effects on oral health. Therefore, the data will provide certain clues for curing some oral diseases by the strategy of adjusting the disturbed microbial compositions in oral disease to healthy level.

The role of bacteriophages in periodontal health and disease

The human periodontium health is commonly compromised by chronic inflammatory conditions and has become a major public health concern. Dental plaque, the precursor of periodontal disease, is a complex biofilm consisting mainly of bacteria, but also archaea, protozoa, fungi and viruses. Viruses that specifically infect bacteria - bacteriophages - are most common in the oral cavity. Despite this, their role in the progression of periodontal disease remains poorly explored. This review aims to summarize how bacteriophages interact with the oral microbiota, their ability to increase bacterial virulence and mediate the transfer of resistance genes and suggests how bacteriophages can be used as an alternative to the current periodontal disease therapies.

Bacterial peptide transporters: Messengers of nutrition to virulence

Bacteria possess numerous peptide transporters for importing peptides as nutrients. However, these peptide transporters are now consistently reported to play a role in the virulence of various bacterial pathogens. Their ability to transport peptides has implications in antibacterial therapy as well. Therefore, it would be instrumental to have complete knowledge about the role of peptide transporters in mediating this cross connection between metabolism and pathogenesis. Studies on various peptide transporters in bacterial pathogens have improved our understanding of this field. In this review, we have given an overview of the functioning of bacterial peptide transporters and their contribution in virulence of major bacterial pathogens.