Community dynamics of subgingival microbiome in periodontitis and targets for microbiome modulation therapy.

The microbial aetiology for periodontitis has been widely studied and deciphered for more than a century. The evolving and changing concepts about periodontal microbiology can be attributed to continuously developing laboratory techniques. The current sequencing platforms have not only expanded the catalog of periodontal pathogens but have also facilitated the understanding of functional interactions of the ecological framework. However, the translation of this new knowledge to advance periodontal therapeutics is minimal. We contend that novel clinical interventions directed beyond conventional therapies need to be emphasized. A clear understanding of the structural and functional dynamics of subgingival microbiota is a pre-requisite for developing any microbiome-based interventions for applications in periodontal health care. In this review, we discuss the 16 s-rRNA gene sequencing-based knowledge of the subgingival microbial community structure, its interactions and functions, and our perspective on the potential to engineer it for periodontal therapeutics. Harnessing this next-generation sequencing-based knowledge, microbiome modulation therapies are poised to change microbiome therapeutics' face.

Antibiotic resistance in the microbiota of periodontitis patients: an update of current findings.

Systemic antibiotics are an effective adjunct in the treatment of periodontitis, but their judicious use is necessary as antimicrobial resistance is a growing global concern. This review aims to explore the current understanding and insight related to antibiotic resistance in the subgingival microbiota of periodontitis patients. A search of MEDLINE (PubMed) was carried out from 1 January 2012 to 25 November 2021 for studies related to antibiotic resistance in periodontitis patients. Of the 90 articles identified, 12 studies were selected for inclusion. A significant incidence of antibiotic resistant isolates was reported for Porphyromonas gingivalis, Prevotella intermedia, Prevotella denticola, Prevotella melaninogenica, Fusobacterium nucleatum, Tanerella forsythia, Aggretibacter actinomycetemcomitans, Streptococcus constellatus, Streptococcus intermedius, and Parvimonas micra, but resistance to specific antibiotics did not reach above 10% of isolates in most studies except for amoxicillin resistance in Aggretibacter actinomycetemcomitans. The highest frequency of resistance across all bacterial species was for amoxicillin, clindamycin, and metronidazole. However, resistance patterns were widely variable across geographical locations, and the high heterogeneity between antibiotic-resistant isolates across studies precludes any clinical recommendations from this study. Although antibiotic resistance has yet to reach critical levels in periodontitis patients, an emphasis on antibiotic stewardship interventions such as point-of-care diagnostics and education for key stakeholders is needed to curb a growing problem.

Salivary Proteomic Profiling Identifies Role of Neutrophil Extracellular Traps Formation in Pregnancy Gingivitis.

Pregnancy gingivitis peaks during mid-pregnancy and resolves transiently towards the postpartum period. However, the role of maternal immune response in orchestrating gingival inflammation has not yet been fully understood. Hence, in this study, we examined the salivary protein profile during the three trimesters of pregnancy, in context to pregnancy gingivitis, employing iTRAQ-based quantitative proteomics. Unstimulated saliva was collected from 10 subjects in each trimester of pregnancy and postpartum period. Samples were analysed using iTRAQ analysis and ELISA and SEM was performed to validate results. Neutrophil mediated immune response was overrepresented in all three trimesters of pregnancy, despite the decrease in phagocytic responses during the second and third trimesters. ELISA showed a significantly higher Neutrophil Extracellular Traps (NETs) formation in the third trimester of pregnancy coinciding with the resolution of pregnancy gingivitis. The NETs-associated proteins (neutrophil elastase and myeloperoxidase) showed a positive correlation with estrogen hormones, which was also highest during the third trimester. Sex hormone-driven NETs formation could be the mainstay of defence that contributes to the remission of pregnancy gingivitis. This study has provided a new insight into the role of immune-modulation in pregnancy gingivitis, which will aid development of new therapeutics for managing pregnancy gingivitis in future.

Coronavirus disease 2019 (COVID-19) vaccines: A concise review.

The development of a successful vaccine against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the agent of coronavirus disease 2019 (COVID-19), in an unmatched period of ten months, is a tribute to human ingenuity in the face of a vicious pandemic. A return to pre-pandemic "normalcy" depends on the successful delivery of the vaccine to a majority (~70%) so as to develop herd immunity critical to arrest the community spread of infection. Vaccination against COVID-19 is particularly important for dentistry as the dental team works in an environment replete with aerosol-generating procedures (AGP) that facilitate virus spread. Hence, a COVID-19 vaccine is likely to be an obligatory requirement for the dental practice, and the latest addition to the extensive list of vaccines required for dental professionals for the safe delivery of dental care. Here, we review the currently available major candidate vaccines against SARS-CoV-2 and their benefits and risks. These include the vaccines developed on next-generation platforms (mRNA, DNA, and viral vector vaccines), and the classic platforms (the live-attenuated virus, and the protein subunit vaccines) The review concludes with a summary of impending issues and challenges facing the provision of COVID-19 vaccines for all stakeholders in dentistry.

Role of the oral microbiome, metabolic pathways, and novel diagnostic tools in intra-oral halitosis: a comprehensive update.

Halitosis or oral malodor is one of the most common reasons for the patients' visit to the dental clinic, ranking behind only dental caries and periodontitis. In the present times, where social and professional communications are becoming unavoidable, halitosis has become a concern of growing importance. Oral malodor mostly develops due to the putrefaction of substrates by the indigenous bacterial populations. Although culture-based studies have provided adequate information on halitosis, the high throughput omics technologies have amplified the resolution at which oral microbial community can be examined and has led to the detection of a broader range of taxa associated with intra-oral halitosis (IOH). These microorganisms are regulated by the interactions of their ecological processes. Thus to develop effective treatment strategies, it is important to understand the microbial basis of halitosis. In the current review, we provide an update on IOH in context to the role of the oral microbiome, metabolic pathways involved, and novel diagnostic tools, including breathomics. Understanding oral microbiota associated with halitosis from a broader ecological perspective can provide novel insights into one's oral and systemic health. Such information can pave the way for the emergence of diagnostic tools that can revolutionize the early detection of halitosis and various associated medical conditions.

Isobaric tags for relative and absolute quantification (iTRAQ)-based quantitative analysis of the salivary proteome during healthy pregnancy and pregnancy gingivitis.

AIM: The present study aimed to investigate the salivary proteome profiles of pregnant women with gingivitis (PG) or without gingivitis (HP) and non-pregnant healthy controls (HC) by employing iTRAQ-based proteomics. MATERIALS AND METHODS: Saliva samples were collected from 30 Chinese women comprising 10 subjects in each of the three groups (PG, HP, and HC). The samples were subjected to iTRAQ-based proteomics analysis, and ELISA was performed to validate the results. The subsequent observations were validated in a cohort of 48 subjects. RESULTS: Pathways associated with neutrophil-mediated immune response and antioxidant defence mechanism were significantly higher in PG than HC. The abundance of salivary cystatins (S, SA, and SN) and antimicrobials were significantly decreased in PG and HP, while cystatin C and D were additionally decreased in PG. Cystatin C was mapped to all the major catabolic pathways and was the most re-wired protein in pregnancy gingivitis. Further validation demonstrated cystatin C to be significantly lower in PG than HC. CONCLUSIONS: While the decrease in levels of salivary cystatins and antimicrobial proteins may predispose healthy pregnant women to pregnancy gingivitis, it may cause persistence of inflammation in pregnant women with gingivitis.

Proteomics Analysis of Candida albicans dnm1 Haploid Mutant Unraveled the Association between Mitochondrial Fission and Antifungal Susceptibility.

Candida albicans is a major fungal pathogen, accounting for approximately 15% of healthcare infections with associated mortality as high as 40% in the case of systemic candidiasis. Antifungal agents for C. albicans infections are limited, and rising resistance is an inevitable problem. Therefore, understanding the mechanism behind antifungal responses is among the top research focuses in combating Candida infections. Herein, the recently developed C. albicans haploid model is employed to examine the association between mitochondrial fission, regulated by Dnm1, and the pathogen's response to antifungals. Proteomic analysis of dnm1Δ and its wild-type haploid parent, GZY803, reveal changes in proteins associated with mitochondrial structures and functions, cell wall, and plasma membrane. Antifungal susceptibility testing revealed that dnm1Δ is more susceptible to SM21, a novel antifungal, than GZY803. Analyses of reactive oxygen species release, antioxidant response, lipid peroxidation, and membrane damages uncover an association between dnm1Δ and the susceptibility to SM21. Dynasore-induced mitochondrial inhibition in SC5314 diploids corroborate the findings. Interestingly, Dynasore-primed SC5314 cultures exhibit increased susceptibility to all antifungals tested. These data suggest an important contribution of mitochondrial fission in antifungal susceptibility of C. albicans. Hence, mitochondrial fission can be a potential target for combined therapy in anti-C. albicans treatment.

Oral microbiome-systemic link studies: perspectives on current limitations and future artificial intelligence-based approaches.

In the past decade, there has been a tremendous increase in studies on the link between oral microbiome and systemic diseases. However, variations in study design and confounding variables across studies often lead to inconsistent observations. In this narrative review, we have discussed the potential influence of study design and confounding variables on the current sequencing-based oral microbiome-systemic disease link studies. The current limitations of oral microbiome-systemic link studies on type 2 diabetes mellitus, rheumatoid arthritis, pregnancy, atherosclerosis, and pancreatic cancer are discussed in this review, followed by our perspective on how artificial intelligence (AI), particularly machine learning and deep learning approaches, can be employed for predicting systemic disease and host metadata from the oral microbiome. The application of AI for predicting systemic disease as well as host metadata requires the establishment of a global database repository with microbiome sequences and annotated host metadata. However, this task requires collective efforts from researchers working in the field of oral microbiome to establish more comprehensive datasets with appropriate host metadata. Development of AI-based models by incorporating consistent host metadata will allow prediction of systemic diseases with higher accuracies, bringing considerable clinical benefits.

Quantitative Proteomics of Strong and Weak Biofilm Formers of Enterococcus faecalis Reveals Novel Regulators of Biofilm Formation.

Enterococcus faecalis is a bacterial pathogen associated with both endodontic and systemic infections. The biofilm formation ability of E. faecalis plays a key role in its virulence and drug resistance attributes. The formation of E. faecalis biofilms on implanted medical devices often results in treatment failure. In the present study, we report protein markers associated with the biofilm formation ability of E. faecalis using iTRAQ-based quantitative proteomics approach. In order to elucidate the biofilm-associated protein markers, we investigated the proteome of strong and weak biofilm-forming E. faecalis clinical isolates in comparison with standard American Type Culture Collection (ATCC) control strains. Comparison of E. faecalis strong and weak biofilm-forming clinical isolates with ATCC control strains showed that proteins associated with shikimate kinase pathway and sulfate transport were up-regulated in the strong biofilm former, while proteins associated with secondary metabolites, cofactor biosynthesis, and tetrahydrofolate biosynthesis were down-regulated. In the weak biofilm former, proteins associated with nucleoside and nucleotide biosynthesis were up-regulated, whereas proteins associated with sulfate and sugar transport were down-regulated. Further pathway and gene ontology analyses revealed that the major differences in biofilm formation arise from differences in metabolic activity levels of the strong and weak biofilm formers, with higher levels of metabolic activity observed in the weak biofilm former. The differences in metabolic activity could therefore be a major determinant of the biofilm ability of E. faecalis The new markers identified from this study can be further characterized in order to understand their exact role in E. faecalis biofilm formation ability. This, in turn, can lead to numerous therapeutic benefits in the treatment of this oral and systemic pathogen. The data has been deposited to the ProteomeXchange with identifier PXD006542.

Comparative Ploidy Proteomics of Candida albicans Biofilms Unraveled the Role of the AHP1 Gene in the Biofilm Persistence Against Amphotericin B.

Candida albicans is a major fungal pathogen causing lethal infections in immunocompromised patients. C. albicans forms antifungal tolerant biofilms contributing significantly to therapeutic failure. The recently established haploid C. albicans biofilm model provides a new toolbox to uncover the mechanism governing the higher antifungal tolerance of biofilms. Here, we comprehensively examined the proteomics and antifungal susceptibility of standard diploid (SC5314 and BWP17) and stable haploid (GZY792 and GZY803) strains of C. albicans biofilms. Subsequent downstream analyses identified alkyl hydroperoxide reductase 1 (AHP1) as a critical determinant of C. albicans biofilm's tolerance of amphotericin B. At 32 µg/ml of amphotericin B, GZY803 haploid biofilms showed 0.1% of persister population as compared with 1% of the diploid biofilms. AHP1 expression was found to be lower in GZY803 biofilms, and AHP1 overexpression in GZY803 restored the percentage of persister population. Consistently, deleting AHP1 in the diploid strain BWP17 caused a similar increase in amphotericin B susceptibility. AHP1 expression was also positively correlated with the antioxidant potential. Furthermore, C. albicans ira2Δ/Δ biofilms were susceptible to amphotericin B and had a diminished antioxidant capacity. Interestingly, AHP1 overexpression in the ira2Δ/Δ strain restored the antioxidant potential and enhanced the persister population against amphotericin B, and shutting down the AHP1 expression in ira2Δ/Δ biofilms reversed the effect. In conclusion, we provide evidence that the AHP1 gene critically determines the amphotericin B tolerance of C. albicans biofilms possibly by maintaining the persisters' antioxidant capacity. This finding will open up new avenues for developing therapies targeting the persister population of C. albicans biofilms. The mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD004274.

Role of periodontal disease in bisphosphonate-related osteonecrosis of the jaws in ovariectomized rats.

OBJECTIVE: This study aimed to investigate the role of progressive periodontal disease in inducing bisphosphonate-related osteonecrosis of the jaws (BRONJ) using an ovariectomized (OVX) rat model mimicking human intracortical remodeling process. MATERIALS AND METHODS: Thirty 12-week-old Spraque-Dawly (SD) female rats were randomly assigned into two groups. All rats underwent bilateral ovariectomy. Six weeks after surgery, zoledronic acid (ZA) or vehicle control was administered intraperitoneally for 12 weeks. On the same day of injection, a cotton ligature was placed subgingivally around the first left lower molar to induce periodontitis. All animals were sacrificed 12 weeks after injection. The entire mandibles were harvested for micro-computed tomography (micro-CT) and histological examinations. RESULTS: Micro-CT examination showed that ligature placement caused significant alveolar bone loss both in ZA (0.63 ± 0.13 vs. 0.38 ± 0.06 mm, P < 0.001) and in control (0.88 ± 0.19 vs. 0.40 ± 0.06 mm, P < 0.001) groups. Whereas in the ZA group, bone loss was attenuated compared with the control group (P < 0.01); the bone mineral density in the ZA group (1.00 ± 0.02 g/cm(3)) was significantly higher than that in vehicle control group (0.96 ± 0.03 g/cm(3), P < 0.001). Histological examination found necrotic bone tissue with extensive, empty lacunae in two of 15 rats in ZA group, but in none of the control group. CONCLUSION: Bisphosphonates inhibit alveolar bone resorption in progressive periodontal disease, which might benefit the management of periodontitis, but increase the risk of developing BRONJ.

Antifungal susceptibility and phenotypic characterization of oral isolates of a black fungus from a nasopharyngeal carcinoma patient under radiotherapy.

BACKGROUND: During a research project on fungal Candida species in patients wearing obturator treated with radiotherapy for their recurrent nasopharyngeal carcinoma, we serendipitously observed the presence of black fungus in two consecutive samples from a patient. CASE PRESENTATION: The samples were collected from a 57 year-old Hong Kong gentleman who diagnosed to have undifferentiated type of nasopharyngeal carcinoma. He was treated with definitive concurrent chemoradiotherapy followed by adjuvant chemotherapy and then received a second-course radiotherapy with IMRT. 18S rDNA sequencing revealed that the isolates belong to Exophiala dermatitidis which was susceptible to fluconazole, itraconazole, ketoconazole and voriconazole. Interestingly, E. dermatitidis isolates were resistant to caspofungin and one isolate was resistant to amphotericin B. Both isolates formed biofilms comparable to that of Candida albicans. Single isolate of E. dermatitidis showed hemolysin and proteinase ability comparable to C. albicans whilst the other isolate was not. CONCLUSION: We, for the first time, reported the discovery of a black fungus-E. dermatitidis isolates derived from a patient with nasopharyngeal carcinoma treated with radiotherapy. These isolates were shown to be resistant to caspofungin, a major antifungal agent for systemic candidiasis. As little is known about the black fungus in the clinical setting, it is important that clinicians must keep abreast of the new discovery in this field.

A Mapping Review of the Pathogenesis of Peri-Implantitis: The Biofilm-Mediated Inflammation and Bone Dysregulation (BIND) Hypothesis.

This mapping review highlights the need for a new paradigm in the understanding of peri-implantitis pathogenesis. The biofilm-mediated inflammation and bone dysregulation (BIND) hypothesis is proposed, focusing on the relationship between biofilm, inflammation, and bone biology. The close interactions between immune and bone cells are discussed, with multiple stable states likely existing between clinically observable definitions of peri-implant health and peri-implantitis. The framework presented aims to explain the transition from health to disease as a staged and incremental process, where multiple factors contribute to distinct steps towards a tipping point where disease is manifested clinically. These steps might be reached in different ways in different patients and may constitute highly individualised paths. Notably, factors affecting the underlying biology are identified in the pathogenesis of peri-implantitis, highlighting that disruptions to the host-microbe homeostasis at the implant-mucosa interface may not be the sole factor. An improved understanding of disease pathogenesis will allow for intervention on multiple levels and a personalised treatment approach. Further research areas are identified, such as the use of novel biomarkers to detect changes in macrophage polarisation and activation status, and bone turnover.

Unveiling clinical applications of bacterial extracellular vesicles as natural nanomaterials in disease diagnosis and therapeutics.

Bacterial extracellular vesicles (BEVs) are naturally occurring bioactive membrane-bound nanoparticles released by both gram-negative and gram-positive bacterial species, exhibiting a multifaceted role in mediating host-microbe interactions across various physiological conditions. Increasing evidence supports BEVs as essential mediators of cell-to-cell communicaiton, influencing bacterial pathogenicity, disease mechanisms, and modulating the host immune response. However, the extent to which these BEV-mediated actions can be leveraged to predict disease onset, guide treatment strategies, and determine clinical outcomes remains uncertain, particularly in terms of their clinical translation potentials. This review briefly describes BEV biogenesis and their internalisation by recipient cells and summarises methods for isolation and characterization, essential for understanding their composition and cargo. Further, it discusses the potential of biofluid-associated BEVs as biomarkers for various diseases, spanning both cancer and non-cancerous conditions. Following this, we outline the ongoing human clinical trials of using BEVs for vaccine development. In addition to disease diagnostics, this review explores the emerging research of using natural or engineered BEVs as smart nanomaterials for applications in anti-cancer therapy and bone regeneration. This discussion extends to key factors for unlocking the clinical potential of BEVs, such as standardization of BEV isolation and characterisation, as well as other hurdles in translating these findings to the clinical setting. We propose that addressing these hurdles through collaborative research efforts and well-designed clinical trials holds the key to fully harnessing the clinical potential of BEVs. As this field advances, this review suggests that BEV-based nanomedicine has the potential to revolutionize disease management, paving the way for innovative diagnosis, therapeutics, and personalized medicine approaches. STATEMENT OF SIGNIFICANCE: Extracellular vesicles (EVs) from both host cells and bacteria serve as multifunctional biomaterials and are emerging in the fields of biomedicine, bioengineering, and biomaterials. However, the majority of current studies focus on host-derived EVs, leaving a gap in comprehensive research on bacteria-derived EVs (BEVs). Although BEVs offer an attractive option as nanomaterials for drug delivery systems, their unique nanostructure and easy-to-modify functions make them a potential method for disease diagnosis and treatment as well as vaccine development. Our work among the pioneering studies investigating the potential of BEVs as natural nanobiomaterials plays a crucial role in both understanding the development of diseases and therapeutic interventions.

The effects of natural compounds-containing mouthrinses on patients with fixed orthodontic appliance treatment: clinical and microbiological outcomes.

AIM: To investigate the effects of two natural compounds-containing mouthrinses (NCCMs) (a fructus mume (FM) extract-containing mouthrinse and an essential oil (EO)-containing mouthrinse) on gingival health and microbial profiles in young orthodontic patients. DESIGN: This 6-month randomized, single-blinded, parallel-controlled clinical trial consists of 90 patients with fixed appliance treatment. The subjects were allocated to (1) negative control group: oral hygiene instruction (OHI) alone; (2) test group 1: OHI plus EO mouthrinse; and (3) test group 2: OHI plus FM mouthrinse. Clinical examinations included plaque index (PI), bleeding index (BI) and modified gingival index (MGI). Salivary microbial quantifications included total aerobic and anaerobic bacteria, Streptococci and Lactobacilli counts. Clinical and microbiological examinations were conducted at baseline, 3rd and 6th months (T1, T2, and T3). RESULTS: BI was significantly reduced in both the FM mouthrinse and EO mouthrinse groups compared with the negative control group at T3 (P < 0.05). There were no significant intergroup differences in salivary bacteria counts in all groups (P > 0.05). CONCLUSION: Both NCCMs effectively reduced gingival bleeding without causing significant alterations of microbial profile in young orthodontic patients.

Amelioration Strategies for Silver Diamine Fluoride: Moving from Black to White.

Topical cariostatic agents have become a reasonable alternative for managing dental caries in young children. Silver diamine fluoride (SDF) is a practical topical approach to arrest caries and avoid extensive and risky dental treatment. However, the literature demonstrates a parental hesitation towards accepting SDF because of black unaesthetic tooth discolouration following application. The rapid oxidation of ionic silver darkens demineralised tooth structure permanently. In this regard, nano-metallic antimicrobials could augment or substitute for silver, and thereby enhance SDF aesthetic performance. Recently, biomedical research has drawn attention to selenium nanoparticles (SeNPs) due to their antimicrobial, antioxidant, and antiviral potencies. Various in vitro studies have examined the effect of SeNPs on the virulence of bacteria. This narrative review explores practical issues when using SDF and suggests future directions to develop it, focusing on antimicrobial metals. Several methods are described that could be followed to reduce the discolouration concern, including the use of nanoparticles of silver, of silver fluoride, or of selenium or other metals with antimicrobial actions. There could also be value in using remineralising agents other than fluoride, such as NPs of hydroxyapatite. There could be variations made to formulations in order to lower the levels of silver and fluoride in the SDF or even to replace one or both of the silver and fluoride components completely. Moreover, since oxidation processes appear central to the chemistry of the staining, adding SeNPs which have antioxidant actions could have an anti-staining benefit; SeNPs could be used for their antimicrobial actions as well. Future research should address the topic of selenium chemistry to optimise how SeNPs would be used with or in place of ionic silver. Incorporating other antimicrobial metals as nanoparticles should also be explored, taking into account the optimal physicochemical parameters for each of these.

BNT162b2 mRNA Vaccine-Induced Immune Response in Oral Fluids and Serum.

OBJECTIVES: The COVID-19 vaccine is currently being administered worldwide to address the ongoing pandemic. Although these vaccines have proven effective in preventing severe disease, the level of immunity required to prevent respiratory mucosal infection remains less well understood. Therefore, it is desirable to develop a noninvasive screening strategy such as oral fluid to monitor secreted antibodies longitudinally as potential surrogates of mucosal immunity. METHODS: We evaluated the anti-spike protein antibodies in gingival crevicular fluid (GCF) and saliva and compared them to immune responses in the blood of 50 healthy health care workers following 2 doses of intramuscular Pfizer/BioNTech-BNT162b2 vaccine. RESULTS: The antibodies to SARS-CoV-2 spike and subdomain proteins (RBD, S1, S2, and NTD) were significantly higher in serum than oral fluids but showed a greater detection rate and higher median titres in GCF than saliva. For all tested SARS-CoV-2 antigens, IgG in GCF (as opposed to saliva) showed a more significant and stronger correlation with IgG in serum. Serum-neutralising antibodies (Nab) titres also displayed a significant and stronger correlation with anti-spike protein and their subdomains in GCF than saliva. Interestingly, the time post-second dose of vaccine and sex had a similar influence on IgG in serum and GCF. However, interferon (IFN)-γ-producing T-cell responses showed no association with SARS-Cov-2 IgG antibodies in serum, GCF, or saliva and neutralisation antibodies in serum. The correlation matrix of all measured parameters grouped serum and GCF IgG parameters separately from salivary IgG parameters indicating that GCF better represents the humoural response in serum than saliva. CONCLUSIONS: Within limitations, we propose that GCF could be a less invasive alternative to serum and more appropriate than saliva to detect antibody responses by current COVID-19 vaccines if the GCF collection procedure could be standardised. Further research is needed to investigate the suitability of GCF for community immune surveillance for vaccines.

Effects of silver diamine fluoride on dentine carious lesions induced by Streptococcus mutans and Actinomyces naeslundii biofilms.

BACKGROUND. Silver diamine fluoride (SDF) has been shown to be a successful treatment for arresting caries. However, the mechanism of SDF is to be elucidated. AIM. To characterize the effects of SDF on dentine carious induced by Streptococcus mutans and Actinomyces naeslundii. DESIGN. Thirty-two artificially demineralized human dentine blocks were inoculated: 16 with S. mutans and 16 with A. naeslundii. Either SDF or water was applied to eight blocks in each group. Biofilm morphology, microbial kinetics and viability were evaluated by scanning electron microscopy, colony forming units, and confocal microscopy. The crosssection of the dentine carious lesions were assessed by microhardness testing, scanning electron microscopy with energy-dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. RESULTS. Biofilm counts were reduced in SDF group than control (P < 0.01). Surfaces of carious lesions were harder after SDF application than after water application (P < 0.05), in S. mutans group, Ca and P weight percentage after SDF application than after water application (P < 0.05). Lesions showed a significantly reduced level of matrix to phosphate after SDF treatment (P < 0.05). CONCLUSION. Present study showed that SDF posses an anti-microbial activity against cariogenic biofilm of S. mutans or A. naeslundii formed on dentine surfaces. SDF slowed down demineralization of dentine. This dual activity could be the reason behind clinical success of SDF.

Human Oral Keratinocytes Challenged by Streptococcus sanguinis and Porphyromonas gingivalis Differentially Affect the Chemotactic Activity of THP-1 Monocytes.

Periodontal diseases are initiated by the shift from microbe-host symbiosis to dysbiosis, and the disrupted host response predominantly contributes to tissue destruction. This study investigated whether and to what extent human oral keratinocytes (HOKs) challenged by a periodontal commensal or pathogen could differentially affect the chemotactic activity of THP-1 monocytes. A selected periodontal commensal (Streptococcus sanguinis ATCC 10556) and a pathogen (Porphyromonas gingivalis ATCC 33277) were cultured and inoculated, respectively, into the lower chamber of Transwell® Permeable Supports with HOKs and incubated for 2 h or 18 h at 37°C under appropriate cell growth conditions. HOKs alone served as the control for the transwell migration assay. Well-stained THP-1 monocytes were seeded in the top chamber of the device, incubated for 2 h and then collected from the lower well for quantitation of the migrated fluorescence-labeled cells by the FACSCalibur™ flow cytometer. The statistical significance was determined using one-way ANOVA. The HOKs challenged by S. sanguinis attracted a significantly higher number of THP-1 cell migration as compared with the control after 2 h or 18 h interaction (p < 0.01). By contrast, P. gingivalis-treated HOKs exhibited a markedly reduced chemotactic effect on THP-1 cells (p < 0.01, 2 h; p < 0.05, 18 h). There was no significant difference in THP-1 cell migration among the groups with either S. sanguinis or P. gingivalis alone. The current findings on P. gingivalis-HOKs interactions with resultant paralysis of THP-1 cell chemotaxis provide further evidence that the keystone periodontopathogen P. gingivalis can evade innate defense and contribute to periodontal pathogenesis.