Bacterial invasion of epithelial cells and spreading in periodontal tissue

Current status of Er:YAG laser in periodontal surgery

Lasers have numerous advantageous tissue interactions such as ablation or vaporization, hemostasis, bacterial killing, as well as biological effects, which induce various beneficial therapeutic effects and biological responses in the tissues. Thus, lasers are considered an effective and suitable device for treating a variety of inflammatory and infectious conditions of periodontal disease. Among various laser systems, the Er:YAG laser, which can be effectively and safely used in both soft and hard tissues with minimal thermal side effects, has been attracting much attention in periodontal therapy. This laser can effectively and precisely debride the diseased root surface including calculus removal, ablate diseased connective tissues within the bone defects, and stimulate the irradiated surrounding periodontal tissues during surgery, resulting in favorable wound healing as well as regeneration of periodontal tissues. The safe and effective performance of Er:YAG laser-assisted periodontal surgery has been reported with comparable and occasionally superior clinical outcomes compared to conventional surgery. This article explains the characteristics of the Er:YAG laser and introduces its applications in periodontal surgery including conventional flap surgery, regenerative surgery, and flapless surgery, based on scientific evidence from currently available basic and clinical studies as well as cases reports.

The root canal microbiome diversity and function. A whole-metagenome shotgun analysis

AIM

To evaluate the root canal microbiome composition and bacterial functional capability in cases of primary and secondary apical periodontitis utilizing whole-metagenome shotgun sequencing.

METHODOLOGY

Twenty-two samples from patients with primary root canal infections, and 18 samples obtained from previously treated teeth currently diagnosed with apical periodontitis were analysed with whole-metagenome shotgun sequencing at a depth of 20 M reads. Taxonomic and functional gene annotations were made using MetaPhlAn3 and HUMAnN3 software. The Shannon and Chao1 indices were utilized to measure alpha diversity. Differences in community composition were evaluated utilizing analysis of similarity (ANOSIM) using Bray-Curtis dissimilarities. The Wilcoxon rank sum test was used to compare differences in taxa and functional genes.

RESULTS

Microbial community variations within a community were significantly lower in secondary relative to primary infections (alpha diversity p = .001). Community composition was significantly different in primary versus secondary infection (R = .11, p = .005). The predominant taxa observed among samples (>2.5%) were Pseudopropionibacterium propionicum, Prevotella oris, Eubacterium infirmum, Tannerella forsythia, Atopobium rimae, Peptostreptococcus stomatis, Bacteroidetes bacterium oral taxon 272, Parvimonas micra, Olsenella profusa, Streptococcus anginosus, Lactobacillus rhamnosus, Porphyromonas endodontalis, Pseudoramibacter alactolyticus, Fusobacterium nucleatum, Eubacterium brachy and Solobacterium moorei. The Wilcoxon rank test revealed no significant differences in relative abundances of functional genes in both groups. Genes with greater relative abundances (top 25) were associated with genetic, signalling and cellular processes including the iron and peptide/nickel transport system. Numerous genes encoding toxins were identified: exfoliative toxin, haemolysins, thiol-activated cytolysin, phospholipase C, cAMP factor, sialidase, and hyaluronic glucosaminidase.

CONCLUSIONS

Despite taxonomic differences between primary and secondary apical periodontitis, the functional capability of the microbiomes was similar.

Human buccal epithelial cells as a model system for molecular analysis of DNA, RNA and protein

We report use of human buccal epithelial cells as an easy model system for isolation and molecular analysis of genomic DNA, RNA, and protein to study any gene of interest by Polymerase Chain Reaction (PCR), RNA expression by Reverse Transcription-PCR (RT-PCR), protein-profiling, and expression by western blot as well as DNA-methylation by Msp I/Hpa II-restriction digestion. We used simple methods to isolate genomic DNA, RNA and protein from human buccal cells collected by oral swab and cultured them in-vitro. The microscopic observation of haematoxylin and eosin (EA-50) stained cells, genomic PCR of house-keeping genes (GAPDH and β-actin), RT-PCR of GAPDH and β-actin mRNAs and whole cell protein-profiling by Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) were carried out. Expression of β-actin protein in supernatant and pellet fractions of the cells was determined by western blot analysis. MTT-assay was carried out to assess the cell viability and cell growth. Green Fluorescence Protein (GFP)-DNA was expressed in these cells by transient transfection. DNA-methylation in the genome was analyzed by Msp I/ Hpa II restriction digestion and agarose gel electrophoresis. Thus these methods can be used for molecular analysis of DNA, RNA and protein from the human buccal epithelial cells for studying and monitoring health, disease, population genetics/genomics and epidemiology under different conditions.

Advances in Hydrogels for Periodontitis Treatment

Periodontitis is a common condition characterized by a bacterial infection and the disruption of the body's immune-inflammatory response, which causes damage to the teeth and supporting tissues and eventually results in tooth loss. Current therapy involves the systemic and local administration of antibiotics. However, the existing treatments cannot exert effective, sustained release and maintain an effective therapeutic concentration of the drug at the lesion site. Hydrogels are used to treat periodontitis due to their low cytotoxicity, exceptional water retention capability, and controlled drug release profile. Hydrogels can imitate the extracellular matrix of periodontal cells while offering suitable sites to load antibiotics. This article reviews the utilization of hydrogels for periodontitis therapy based on the pathogenesis and clinical manifestations of the disease. Additionally, the latest therapeutic strategies for smart hydrogels and the main techniques for hydrogel preparation have been discussed. The information will aid in designing and preparing future hydrogels for periodontitis treatment.

Bone Formation and Maintenance in Oral Surgery: The Decisive Role of the Immune System-A Narrative Review of Mechanisms and Solutions

Based on the evidence of a significant communication and connection pathway between the bone and immune systems, a new science has emerged: osteoimmunology. Indeed, the immune system has a considerable impact on bone health and diseases, as well as on bone formation during grafts and its stability over time. Chronic inflammation induces the excessive production of oxidants. An imbalance between the levels of oxidants and antioxidants is called oxidative stress. This physio-pathological state causes both molecular and cellular damage, which leads to DNA alterations, genetic mutations and cell apoptosis, and thus, impaired immunity followed by delayed or compromised wound healing. Oxidative stress levels experienced by the body affect bone regeneration and maintenance around teeth and dental implants. As the immune system and bone remodeling are interconnected, bone loss is a consequence of immune dysregulation. Therefore, oral tissue deficiencies such as periodontitis and peri-implantitis should be regarded as immune diseases. Bone management strategies should include both biological and surgical solutions. These protocols tend to improve immunity through antioxidant production to enhance bone formation and prevent bone loss. This narrative review aims to highlight the relationship between inflammation, oxidation, immunity and bone health in the oral cavity. It intends to help clinicians to detect high-risk situations in oral surgery and to propose biological and clinical solutions that will enhance patients' immune responses and surgical treatment outcomes.

Green Synthesis of Bacopa monnieri-Mediated Magnesium Oxide Nanoparticles and Analysis of Their Antimicrobial, Antioxidant, and Cytotoxic Properties

Background The management of aggressive forms of periodontal disease has become an issue of concern due to the emergence of bacterial resistance. Nanoparticles (NPs) have emerged as a potential therapeutic agent with a multitude of biological functions. The green synthesis of these NPs is more eco-friendly than conventional methods. The present study aimed at the green synthesis of magnesium oxide nanoparticles using Bacopa monnieri (bMgO NPs) and its antibacterial, antioxidant, and cytotoxic analysis. Materials and methods Magnesium oxide NPs were green synthesized using B. monnieri extract using a wet chemical method. The resultant bMgO NPs were assessed for antibacterial activity against Staphylococcus aureus and Escherichia coli. Antioxidant activity was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and the hydrogen peroxide (H2O2) assay. Cytotoxicity was assessed using zebrafish viability on treatment with bMgO NPs. Results Compared to the antibiotic standard, the green synthesized bMgO NPs showed good antibacterial properties against S. aureus and E. coli. It also showed excellent antioxidant activity and biocompatibility. Conclusion The bMgO NPs have great potential as a local drug delivery agent and should be further explored for their antibacterial and antioxidant properties in vivo.

Antimicrobial photodynamic therapy with dendrosomal curcumin and blue laser against Porphyromonas gingivalis

BACKGROUND

Periodontitis is a chronic inflammatory disease that leads to the loss of tooth-supporting structures. Porphyromonas gingivalis is one of the main pathogens responsible for periodontitis. Because of the limitations of antibiotic use, various alternative approaches have been developed. Antimicrobial photodynamic therapy uses photosensitizers and light to eliminate pathogens. Curcumin is a promising photosensitizer, but has low bioavailability and water solubility. However, dendrosomes can efficiently encapsulate curcumin, overcoming these obstacles. This study aimed to evaluate the efficacy of photodynamic therapy with blue laser and dendrosomal curcumin against Porphyromonas gingivalis.

METHODS

In this in vitro experiment, the minimum inhibitory concentration (MIC) of dendrosomal curcumin was determined using a serial dilution approach. Porphyromonas gingivalis suspensions were subjected to blue laser irradiation (447 nm, output power 100 mW) for 30 to 180 s. Finally, several subMIC dendrosomal curcumin concentrations and blue laser irradiation periods were applied to the bacterial suspensions. The negative control group received no therapy, whereas the positive control group was treated with 0.2% chlorhexidine. Consequently, the colony count of each group was calculated.

RESULTS

Treatment of Porphyromonas gingivalis with dendrosomal Curcumin at concentrations of 8-250 μg/mL significantly reduced bacterial growth compared to untreated group. 90 second exposure to a blue laser (31.8 J/cm2) completely inhibited the growth of Porphyromonas gingivalis. Blue laser irradiation for 60 s (21.2 J/cm2) markedly reduced bacterial growth but did not completely prevent its survival. Photodynamic therapy using dendrosomal curcumin at concentrations of 2-4 μg/mL and irradiation for 30-90 s resulted in complete eradication of Porphyromonas gingivalis compared to controls (P < 0.05).

CONCLUSION

The reduction in survival of Porphyromonas gingivalis following photodynamic therapy with dendrosomal curcumin and blue laser indicates that this technique could be a useful approach to eradicate Porphyromonas gingivalis infections.

Expression of tight junction proteins in smokers and non-smokers with generalized Stage III periodontitis

OBJECTIVE

This study aims to evaluate the gingival crevicular fluid (GCF) levels of tumor necrosis factor-α (TNF-α), zonula occludens-1 (ZO-1), occludin (Occ), and tricellulin (Tric) in periodontitis, as well as their alterations due to smoking.

BACKGROUND

Tight junctions (TJ), which consist of transmembrane and cytoplasmic scaffolding proteins, connect the epithelial cells of the periodontium. Occ, claudins, junctional adhesion molecules, and Tric are transmembrane TJ proteins found at the cell membrane. The transmembrane TJ proteins and the intracellular cytoskeleton are directly linked by cytoplasmic scaffolding proteins such as ZO-1. Although the functions and locations of these molecules have been defined, their behavior in periodontal inflammation is unknown.

METHODS

The study included four groups: individuals with periodontal health without smoking (C; n = 31), individuals with generalized Stage III periodontitis without smoking (P; n = 28), individuals with periodontal health while smoking (CS; n = 22), and individuals with generalized Stage III periodontitis while smoking (PS; n = 18). Clinical periodontal parameters were recorded, and enzyme-linked immunosorbent assay (ELISA) was used to examine ZO-1, Occ, Tric, and TNF-α levels in GCF.

RESULTS

In the periodontitis groups, clinical parameters were significantly higher (p < .001). The site-specific levels of TNF-α, ZO-1, Tric, and Occ in the P group were statistically higher than those in the other groups (p < .05). TNF-α, probing pocket depth (PPD), and bleeding on probing (BOP) exhibited positive correlations with all TJ proteins (p < .005).

CONCLUSIONS

Smoking could potentially affect the levels of epithelial TJ proteins in the GCF, thereby potentially playing a significant role in the pathogenesis of the periodontal disease.

Zingerone-Induced Autophagy Suppresses IL-1β Production by Increasing the Intracellular Killing of Aggregatibacter actinomycetemcomitans in THP-1 Macrophages

Periodontitis is caused by the inflammation of tooth-supporting tissue by pathogens such as Aggregatibacter actinomycetemcomitans. Interleukin-1β (IL-1β), a pro-inflammatory cytokine, triggers a series of inflammatory reactions and promotes bone resorption. The aim of this study was to examine the molecular mechanism and anti-inflammatory function of zingerone, a dietary phenolic found in Zingiber officinale, on periodontal inflammation induced by A. actinomycetemcomitans. Zingerone attenuated A. actinomycetemcomitans-induced nitric oxide (NO) production by inhibiting the expression of inducible nitric oxide synthase (iNOS) in THP-1 macrophages. Zingerone also inhibited the expression of tumor necrosis factor (TNF)-α, IL-1β, and their signal pathway molecules including the toll-like receptor (TLR)/mitogen-activated protein kinase (MAPKase). In particular, zingerone suppressed the expression of absent in melanoma 2 (AIM2) inflammasome components on IL-1β production. Moreover, zingerone enhanced autophagosome formation and the expressions of autophagy-associated molecules. Interestingly, zingerone reduced the intracellular survival of A. actinomycetemcomitans. This was blocked by an autophagy inhibitor, which reversed the decrease in IL-1β production by zingerone. Finally, zingerone alleviated alveolar bone absorption in an A. actnomycetemcomitans-induced periodontitis mice model. Our data suggested that zingerone has potential use as a treatment for periodontal inflammation induced by A. actinomycetemcomitans.

The Potential Role of Epigenetic Modifications on Different Facets in the Periodontal Pathogenesis

Periodontitis is a chronic inflammatory disease that affects the supporting structures of teeth. In the literature, the association between the pathogenicity of bacteria and environmental factors in this regard have been extensively examined. In the present study, we will shed light on the potential role that epigenetic change can play on different facets of its process, more particularly the modifications concerning the genes involved in inflammation, defense, and immune systems. Since the 1960s, the role of genetic variants in the onset and severity of periodontal disease has been widely demonstrated. These make some people more susceptible to developing it than others. It has been documented that the wide variation in its frequency for various racial and ethnic populations is due primarily to the complex interplay among genetic factors with those affecting the environment and the demography. In molecular biology, epigenetic modifications are defined as any change in the promoter for the CpG islands, in the structure of the histone protein, as well as post-translational regulation by microRNAs (miRNAs), being known to contribute to the alteration in gene expression for complex multifactorial diseases such as periodontitis. The key role of epigenetic modification is to understand the mechanism involved in the gene-environment interaction, and the development of periodontitis is now the subject of more and more studies that attempt to identify which factors are stimulating it, but also affect the reduced response to therapy.

Porphyromonas gingivalis Evades Immune Clearance by Regulating Lysosome Efflux

Porphyromonas gingivalis, a major periodontal pathogen, invades autophagosomes of cells, including gingival epithelial cells, endothelial cells, gingival fibroblasts, macrophages, and dendritic cells, to escape antimicrobial autophagy and lysosome fusion. However, it is not known how P. gingivalis resists autophagic immunity, survives within cells, and induces inflammation. Thus, we investigated whether P. gingivalis could escape antimicrobial autophagy by promoting lysosome efflux to block autophagic maturation, leading to intracellular survival, and whether the growth of P. gingivalis within cells results in cellular oxidative stress, causing mitochondrial damage and inflammatory responses. P. gingivalis invaded human immortalized oral epithelial cells in vitro and mouse oral epithelial cells of gingival tissues in vivo. The production of reactive oxygen species (ROS) increased upon bacterial invasion, as well as mitochondrial dysfunction-related parameters with downregulated mitochondrial membrane potential and intracellular adenosine triphosphate (ATP), upregulated mitochondrial membrane permeability, intracellular Ca2+ influx, mitochondrial DNA expression, and extracellular ATP. Lysosome excretion was elevated, the number of intracellular lysosomes was diminished, and lysosomal-associated membrane protein 2 was downregulated. Expression of autophagy-related proteins, microtubule-associated protein light chain 3, sequestosome-1, the NLRP3 inflammasome, and interleukin-1β increased with P. gingivalis infection. P. gingivalis may survive in vivo by promoting lysosome efflux, blocking autophagosome-lysosome fusion, and destroying autophagic flux. As a result, ROS and damaged mitochondria accumulated and activated the NLRP3 inflammasome, which recruited the adaptor protein ASC and caspase 1, leading to the production of proinflammatory factor interleukin-1β and inflammation.

Advanced co-culture model: Soft tissue cell and bacteria interactions at the transgingival dental implant interface

OBJECTIVES

To better simulate and understand the clinical situation in which tissue cells and bacteria compete for settlement on an implant surface, the aim was to develop an improved transgingival co-culture model.

METHODS

For this model human gingival fibroblasts (HGF) were seeded on different titanium surfaces in the presence of the early colonizer Streptococcus gordonii or mixed oral bacteria. Subsequently adhesion and viability of HGF cells was analyzed.

RESULTS

Simultaneous co-culture showed no decrease in the viability of HGF cells at early stages compared to the control group. However, a moderate impact on HGF viability (76 ± 23 %) was observed after 4 h of co-culture, which then significantly decreased after 5 h (21 ± 2 %) of co-cultivation, resulting in cell death and detachment from the surface. Further experiments including saliva pre-treatment of smooth and structured titanium surfaces with Streptococcus gordonii or mixed oral bacteria suggested a cell-protective property of saliva.

SIGNIFICANCE

Our study revealed that during simultaneous co-culture of cells and bacteria, which resembles the clinical situation the closest, the viability of gingival cells is considerably high in the early phase, suggesting that increasing initial cell adhesion rather than antibacterial functionality is a major goal and a relevant aspect in the development and testing of transgingival implant and abutment surface modifications.

Zoledronic acid affects the process of Porphyromonas gingivalis infecting oral mucosal epithelial barrier: An in-vivo and in-vitro study

Zoledronic acid (ZA), one of the commonly used bisphosphonates, is mainly used for bone-metabolic diseases. Studies proved that ZA has adverse effects on oral soft tissues. As the first line of innate immunity, the gingival epithelium could be infected by periodontal pathogens, which is a key process of the initiation of periodontal diseases. Yet, how ZA affects the periodontal pathogens infecting the epithelial barrier remains unclear. This study aimed to investigate the influences of ZA on the process of Porphyromonas gingivalis (P. gingivalis) infecting the gingival epithelial barrier via in-vitro and in-vivo experiments. In the in-vitro experiments, under the condition of different concentrations of ZA (0, 1, 10, and 100 μM), P. gingivalis was used to infect human gingival epithelial cells (HGECs). The infections were detected by transmission electron microscope and confocal laser scanning microscope. Besides, the internalization assay was applied to quantify the P. gingivalis, which infected the HGECs, in the different groups. To evaluate the expression levels of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, and IL-8, by infected HGECs, real-time quantitative reverse transcription-polymerase chain reactions were applied. In the in-vivo experiments, rats were given ZA solution (ZA group) or saline (control group) by tail intravenous injection for 8 weeks. Subsequently, we put ligatures around the maxillary second molars of all the rats and inoculated P. gingivalis to the gingiva every other day from day 1 to day 13. The rats were sacrificed on days 3, 7, and 14 for micro-CT and histological analyses. The in-vitro results manifested that the quantity of P. gingivalis that had infected HGECs increased with the ZA concentrations. Pro-inflammatory cytokines expression by HGECs were significantly increased by 100 μM ZA. In the in-vivo study, compared to the control group, more P. gingivalis was detected in the superficial layer of gingival epithelium in the ZA group. Besides, ZA significantly increased the expression level of IL-1β on day 14 and IL-6 on days 7 and 14 in gingival tissues. These findings suggest that the oral epithelial tissues of patients who receive high-dose ZA treatment may be more susceptible to periodontal infections, resulting in severe inflammatory conditions.

Immunomodulatory Effects of Endodontic Sealers: A Systematic Review

Inflammation is a crucial step prior to healing, and the regulatory effects of endodontic materials on the immune response can influence tissue repair. This review aimed to answer whether endodontic sealers can modulate the immune cells and inflammation. An electronic search in Scopus, Web of Science, PubMed, and Google Scholar databases were performed. This systematic review was mainly based on PRISMA guidelines, and the risk of bias was evaluated by SYRCLEs and the Modified CONSORT checklist for in vivo and in vitro studies, respectively. In total, 28 articles: 22 in vitro studies, and six in vivo studies were included in this systematic review. AH Plus and AH 26 can down-regulate iNOS mRNA, while S-PRG sealers can down-regulate p65 of NF-κB pathways to inhibit the production of TNF-α, IL-1, and IL-6. In vitro and in vivo studies suggested that various endodontic sealers exhibited immunomodulatory impact in macrophages polarization and inflammatory cytokine production, which could promote healing, tissue repair, and inhibit inflammation. Since the paradigm change from immune inert biomaterials to bioactive materials, endodontic materials, particularly sealers, are required to have modulatory effects in clinical conditions. New generations of endodontic sealers could hamper detrimental inflammatory responses and maintain periodontal tissue, which represent a breakthrough in biocompatibility and functionality of endodontic biomaterials.

Inhibitory effect of polysaccharides extracted from Changbai Mountain Ganoderma lucidum on periodontal inflammation

As the main bioactive substance of Ganoderma lucidum, Ganoderma lucidum polysaccharide (GLP) has anti-inflammatory, antibacterial, and other biological activities. Studies have shown that GLP can regulate the expression of multiple inflammatory cytokines in different inflammatory models and diseases as part of the anti-infection immune response. We extracted crude Changbai Mountain Ganoderma lucidum polysaccharides (CGLPs), analyzed their physical and chemical properties, and then applied them to the periodontitis model to verify whether they have an inhibitory effect on mouse periodontitis. CGLP was determined to be a heteropolysaccharide with dextran as the main component. Its molecular weight was 17.40 kDa. In vivo experiments in mice showed that CGLP can inhibit the alveolar bone loss and reduced inflammation caused of periodontitis by regulating the expression of the inflammatory factors IL-1β, TNF-α, and IL-10 in a concentration-dependent manner.

Microbiome in paired root apices and periapical lesions and its association with clinical signs in persistent apical periodontitis using next-generation sequencing

AIM

To assess and compare the microbiome of paired root apices and periapical lesions from cases with failed endodontic treatment and to associate the microbiome and bacterial metabolic pathways in both sites with asymptomatic apical periodontitis (AAP) and symptomatic apical periodontitis (SAP), using next-generation sequencing (NGS).

METHODOLOGY

Matched root apices and periapical lesions of patients with failed root canal treatments were surgically extracted. Specimens were cryopulverized, bacterial DNA was extracted and the V3-V4 hypervariable regions of the 16 S rRNA gene were amplified and sequenced using the Illumina Miseq platform. Diversity and community composition were studied in the paired samples, as well as in AAP and SAP cases. Diversity indices were compared in each case by means of the Wilcoxon matched-pairs signed rank and Mann-Whitney U tests. Differences in the community composition were explored with multivariate statistical analysis and Linear discriminant analysis Effect Size (LEfSe). Bacterial functional study was performed through the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis.

RESULTS

Twenty-one paired apices and lesions were successfully sequenced and analysed, identifying a total of 21 phyla and 600 genera. A higher alpha-diversity was observed in the periapical lesions, although no global differences in the community composition between the two sites were found (p = .87), the most prevalent genera being Fusobacterium, Porphyromonas and Streptococcus. Prevotella, Clostridiales_vadinBB60_group, Bosea, Phreatobacter, Afipia and Xanthobacteriaceae_unclassified were enriched in SAP samples, while Pseudopropionibacterium, Campylobacter and Peptoniphilus were significantly more abundant in AAP cases (p < .05). Metabolic pathways involved in the amino acid metabolism or degradation and flagellum assembly were more abundant in SAP samples, whereas glucose metabolism-related pathways were associated with AAP.

CONCLUSIONS

The bacterial community composition was similar in the apices and periapical lesions. The microbiome was different in AAP and SAP samples, gram-negative bacteria showing higher relative abundances in SAP cases. An association was observed between amino acid degradation and flagellum assembly pathways, and the development of tenderness to percussion or palpation.

Pathogenesis of periodontitis - A potential role for epithelial-mesenchymal transition

Epithelial mesenchymal transition (EMT) is a process comprising cellular and molecular events which result in cells shifting from an epithelial to a mesenchymal phenotype. Periodontitis is a destructive chronic disease of the periodontium initiated in response to a dysbiotic microbiome, and dominated by Gram-negative bacteria in the subgingival niches accompanied by an aberrant immune response in susceptible subjects. Both EMT and periodontitis share common risk factors and drivers, including Gram-negative bacteria, excess inflammatory cytokine production, smoking, oxidative stress and diabetes mellitus. In addition, periodontitis is characterized by down-regulation of key epithelial markers such as E-cadherin together with up-regulation of transcriptional factors and mesenchymal proteins, including Snail1, vimentin and N-cadherin, which also occur in the EMT program. Clinically, these phenotypic changes may be reflected by increases in microulceration of the pocket epithelial lining, granulation tissue formation, and fibrosis. Both in vitro and in vivo data now support the potential involvement of EMT as a pathogenic mechanism in periodontal diseases which may facilitate bacterial invasion into the underlying gingival tissues and propagation of inflammation. This review surveys the available literature and provides evidence linking EMT to periodontitis pathogenesis.

Effects of Atmospheric Pressure Plasma in the Treatment of Experimental Periodontitis in Beagle Dogs

OBJECTIVE

The specific objective of this study was to evaluate the effects of atmospheric pressure plasma (APP) in the treatment of experimental periodontitis in Beagle dogs.

METHODS

The APP jet was diagnosed using optical emission spectroscopy and laser-induced fluorescence spectroscopy. Six Beagles received stainless steel ligatures to establish experimental periodontitis model. The teeth in the control group were subjected to conventional root surface debridement (RSD) and chlorhexidine irrigation. The APP group also started with RSD and was then subjected to plasma irradiation. Clinical analyses including plaque index, modified sulcus bleeding index, pocket depth and attachment loss (AL), as well as cone-beam computed tomography (CBCT) analysis, were performed at baseline, 4th week, 8th week and 12th week after treatment.

RESULTS

The results showed that typical reactive oxygen and nitrogen species were found in the full spectrum and the gas temperature of APP was close to room temperature. The highest concentrations of hydroxide and oxygen were obtained at 5 mm away from the nozzle. In both groups, all values in clinical examinations were significantly lower (P<0.05) at 12th week after treatment than those at baseline. At the 12th week, the AL in clinical examinations and the bone loss in CBCT images in the APP group were significantly lower than those in the control group (P<0.05). The hematoxylin-eosin staining showed more renascent alveolar bone in the APP group than in the control group.

CONCLUSION

These findings suggested that APP has profound potential for use as an adjunct approach for periodontitis treatment.

The Link between Stroke Risk and Orodental Status-A Comprehensive Review

One of the primary causes of disability and mortality in the adult population worldwide is stroke. A person's general health is significantly impacted by their oral and dental health. People who have poor oral health are more susceptible to conditions such as stroke. Stroke risk has long been linked to oral and dental conditions. The risk of stroke and its cost impact on the healthcare systems appear to be significantly reduced as a result of the decline in the incidence and prevalence of oral and dental illnesses. Hypothetically, better management of oral hygiene and dental health lead to reduced stroke risk. To the authors' best knowledge, for the first time, the potential link between dental health and stroke were cross-examined. The most typical stroke symptoms, oral and dental illnesses linked to stroke, and the role of oral healthcare professionals in stroke prevention are revealed. The potential mediating processes and subsequent long-term cognitive and functional neurological outcomes are based on the available literature. It must be noted that periodontal diseases and tooth loss are two common oral health measures. Lack of knowledge on the effects of poor oral health on systemic health together with limited access to primary medical or dental care are considered to be partially responsible for the elevated risk of stroke. Concrete evidence confirming the associations between oral inflammatory conditions and stroke in large cohort prospective studies, stratifying association between oral disease severity and stroke risk and disease effects on stroke survival will be desirable. In terms of clinical pathology, a predictive model of stroke as a function of oral health status, and biomarkers of systemic inflammation could be useful for both cardiologists and dentists.

Rodent Gingival Tissue Culture in an Aging Experimental Model: A Pilot Study

Background:

Gingiva acts as a barrier to prevent further invasion of pathogens in periodontitis. The gingival structure consists of epithelial tissue and connective tissue. As the aging process continues, there are several changes in the periodontium. Previous studies have tried to investigate the complex interaction between the host immune system and bacteria by using animal models, especially rodents.

Objective:

The aim of the study was to evaluate the effectiveness of collecting gingival tissue from the palate and retromolar pad.

Materials and Methods:

The aging experimental model had two age categories of male rodents of 18 and 58 weeks. Tissue was collected from the mandible retromolar pad and palate with full-thickness excision. Tissues were transferred to a complete medium at 4°C. Gingival tissue was cultured in a 37°C culture incubator at 5% CO2. Tissue proliferation was observed on the first, third, and fifth days using the hemocytometer. The cell metabolism rate between the two age categories was checked using the MTT Assay. Two-way ANOVA was used for statistical analysis.

Results:

Gingival tissues obtained from the experimental models of two age categories were alive, and proliferation was observed. The old rodent group showed no significant result in terms of cell morphology on the first vs. third day (p>0.05), but significant results were found on the first vs. fifth day and third day vs. the fifth day (p<0.05). The young rodent group showed the most significant morphology changes between days. In both young and old categories, no significant difference was observed in the cell metabolism.

Conclusion:

Rodent gingival tissue collection from the retromolar pad and palate was found suitable for tissue culture in the aging experimental study.

Light-emitting-diode-based antimicrobial photodynamic therapies in the treatment of periodontitis

The use of light-emitting diode (LED)-based photodynamic therapies in the treatment of periodontitis is increasing because these modalities are effective, safe, and painless. They are not subject to acquired drug resistance or environmental issues and are associated with no complications when used appropriately. These light sources have also been used in combination with pharmacological measures to synergize their effects and optimize therapeutic outcomes. This review focuses on optical devices used in treating periodontitis and delineates the current applications of various methods, including their utility and efficacy. The application of LEDs in periodontology is described.

A vitronectin-derived peptide prevents and restores alveolar bone loss by modulating bone re-modelling and expression of RANKL and IL-17A

AIM

This study investigated whether a vitronectin-derived peptide (VnP-16) prevents and/or reverses alveolar bone resorption induced by ligature-induced periodontitis in rodents and identified the underlying mechanism.

MATERIALS AND METHODS

We evaluated the effects of VnP-16 on osteogenic differentiation in human periodontal ligament cells (hPDLCs), lipopolysaccharide-induced inflammatory responses in gingival fibroblasts, and immune response in T lymphocytes. Ligature-induced periodontitis was induced by ligating the bilateral mandibular first molars for 14 days in rats and for 7 days in mice (n = 10/group). VnP-16 (100 μg/10 μl) was applied topically into the gingival sulcus of rats via intra-sulcular injection, whereas the peptide (50 μg/5 μl) was administered directly into the gingiva of mice via intra-gingival injection. To evaluate the preventive and therapeutic effects of VnP-16, micro-computed tomography analysis and histological staining were then performed.

RESULTS

VnP-16 promoted osteogenic differentiation of periodontal ligament cells and inhibited the production of lipopolysaccharide-induced inflammatory mediators in gingival fibroblasts. Concomitantly, VnP-16 modulated the host immune response by reducing the number of receptor activator of NF-κB ligand (RANKL)-expressing lipopolysaccharide-stimulated CD4⁺ and CD8⁺ T cells, and by suppressing RANKL and interleukin (IL)-17A production. Furthermore, local administration of VnP-16 in rats and mice significantly prevented and reversed alveolar bone loss induced by ligature-induced periodontitis. VnP-16 enhanced osteoblastogenesis and simultaneously inhibited osteoclastogenesis and suppressed RANKL and IL-17A expression in vivo.

CONCLUSIONS

Our findings suggest that VnP-16 acts as a potent therapeutic agent for preventing and treating periodontitis by regulating bone re-modelling and immune and inflammatory responses.

Effect of diode laser combined with minocycline hydrochloride in nonsurgical periodontal therapy: a randomized clinical trial

Background

This study aimed to assess the effect of diode laser combined with minocycline hydrochloride in conventional nonsurgical periodontal therapy.

Methods

Ninety-two patients and 1206 teeth were included in this study. The patients were diagnosed moderate or severe periodontal diseases with the presence of teeth in at least 3 quadrants in the oral cavity. Each patient’s quadrants were randomly divided into three treatment groups as following, Control group: scaling and root planning (SRP); Experimental group 1 (Exp 1): SRP + minocycline hydrochloride; Experimental group 2 (Exp 2): SRP + 809 nm diode laser + minocycline hydrochloride. The minocycline in Exp 1 and Exp 2 was applied once per week, for 4 weeks. Clinical examinations including periodontal probing depth (PD), clinical attachment level (CAL) and bleeding index (BI), and the secretion of inflammatory factor (tumor necrosis factor, TNF-α) was detected by ELISA before and 3, 6 months after the treatments. The differences among these groups were assessed by One-Way ANOVA and Kruskal–Wallis test. P-value < 0.05 was considered significant.

Results

All the periodontal indexes (PD, CAL and BI) were improved after each treatment and the secretion of TNF-α was reduced for all three groups. In patients with deep periodontal pockets, Exp 2 showed significant improvements in all indexes comparison with Con group and Exp group 1.

Conclusions

The synergistic effect of SRP and 809 nm diode laser combined with minocycline hydrochloride could play an efficient and reliable effect in the nonsurgical periodontal treatment approach.

Trial registration The clinical trial was retrospectively registered in chictr.org.cn with registration ChiCTR2100051708 (01/10/2021).

Dietary Glutamine Inclusion Regulates Immune and Antioxidant System, as Well as Programmed Cell Death in Fish to Protect against Flavobacterium columnare Infection

The susceptibility of animals to pathogenic infection is significantly affected by nutritional status. The present study took yellow catfish (Pelteobagrus fulvidraco) as a model to test the hypothesis that the protective roles of glutamine during bacterial infection are largely related to its regulation on the immune and antioxidant system, apoptosis and autophagy. Dietary glutamine supplementation significantly improved fish growth performance and feed utilization. After a challenge with Flavobacterium columnare, glutamine supplementation promoted il-8 and il-1β expression via NF-κB signaling in the head kidney and spleen, but inhibited the over-inflammation in the gut and gills. Additionally, dietary glutamine inclusion also enhanced the systematic antioxidant capacity. Histological analysis showed the protective role of glutamine in gill structures. Further study indicated that glutamine alleviated apoptosis during bacterial infection, along with the reduced protein levels of caspase-3 and the reduced expression of apoptosis-related genes. Moreover, glutamine also showed an inhibitory role in autophagy which was due to the increased activation of the mTOR signaling pathway. Thus, our study for the first time illustrated the regulatory roles of glutamine in the fish immune and antioxidant system, and reported its inhibitory effects on fish apoptosis and autophagy during bacterial infection.

Histopathological and immunohistochemical study of periodontal changes in chronic smokers

Periodontal disease is a chronic inflammatory, multifactorial condition, that, in the absence of an early and adequate treatment, may lead to a progressive damaging of the alveolar tissues that support the teeth (periodontal ligament, cement and alveolar bone) followed by teeth mobility and, subsequently, their loss. Periodontal disease is one of the most common inflammatory disease affecting adult individuals all over the world, being considered a real worldwide pandemic. This disease may influence the progression of certain systemic diseases: diabetes mellitus, cardiovascular diseases, ischemic cardiomyopathy, myocardial infarction, stroke, neurodegenerative diseases, chronic kidney diseases, cancer, etc. The association between smoking and periodontal disease was described in numerous clinical and epidemiological studies, suggesting that products derived from tobacco burning may change the clinical aspects and the disease progression. The present study analyzed microscopically and immunohistochemically 58 periodontal fragments, from 50 patients, chronic smokers, clinically diagnosed with severe periodontitis. There were highlighted major changes in the gingival epithelium (epithelium thickening, acanthosis, intraepithelial edema, infiltrates of neutrophils or lymphocytes, epithelial necrosis), in the periodontal conjunctive tissue (more or less intense inflammatory infiltrates, microhemorrhages, vascular congestion, intense immunohistochemical expression for some matrix metalloproteinases). The periodontal changes may be the expression of both toxic factors present in tobacco smoke and due to the changes caused by tobacco in the microbial flora of the oral cavity.

Impact of tooth loss due to periodontal disease on the prognosis of rehabilitation

When periodontal disease is diagnosed, it is difficult to predict the clinical response of treatment of a tooth over time because the result of treatment is affected by several factors and will depend on the maintenance and support of periodontal treatment. Rehabilitation with removable dental prostheses, fixed prostheses, and dental implants makes it possible to restore the function and esthetics of patients with tooth loss due to periodontal disease. The predictive factors of tooth loss in periodontitis patients should be assessed by dentists to inform their clinical decision-making during dental treatment planning. This will provide detailed individualized information and level of risk of patients considered suitable for dental rehabilitation. Therefore, the aim of this article was to review the subject of "Impact of tooth loss due to periodontal disease on the prognosis of rehabilitation" and the effect of fixed, removable, and implant-supported prostheses in periodontal patients.

Polar swimmers induce several phases in active nematics

Swimming bacteria in passive nematics in the form of lyotropic liquid crystals are defined as a new class of active matter known as living liquid crystals in recent studies. It has also been shown that liquid crystal solutions are promising candidates for trapping and detecting bacteria. We ask the question, can a similar class of matter be designed for background nematics which are also active? Hence, we developed a minimal model for the mixture of polar particles in active nematics. It is found that the active nematics in such a mixture are highly sensitive to the presence of polar particles and show the formation of large scale higher order structures for a relatively low polar particle density. Upon increasing the density of polar particles, different phases of active nematics are found and it is observed that the system shows two phase transitions. The first phase transition is a first order transition from quasi-long-ranged ordered active nematics to disordered active nematics with larger scale structures. On further increasing density of polar particles, the system transitions to a third phase, where polar particles form large, mutually aligned clusters. These clusters sweep the whole system and enforce local order in the nematics. The current study can be helpful for detecting the presence of very low densities of polar swimmers in active nematics and can be used to design and control different structures in active nematics.

Paradigm shift in the pathogenesis and treatment of oral cancer and other cancers focused on the oralome and antimicrobial-based therapeutics

The oral microbiome is a community of microorganisms, comprised of bacteria, fungi, viruses, archaea, and protozoa, that form a complex ecosystem within the oral cavity. Although minor perturbations in the environment are frequent and compensable, major shifts in the oral microbiome can promote an unbalanced state, known as dysbiosis. Dysbiosis can promote oral diseases, including periodontitis. In addition, oral dysbiosis has been associated with other systemic diseases, including cancer. The objective of this review is to evaluate the epidemiologic evidence linking periodontitis to oral, gastrointestinal, lung, breast, prostate, and uterine cancers, as well as describe new evidence and insights into the role of oral dysbiosis in the etiology and pathogenesis of the cancer types discussed. Finally, we discuss how antimicrobials, antimicrobial peptides, and probiotics may be promising tools to prevent and treat these cancers, targeting both the microbes and associated carcinogenesis processes. These findings represent a novel paradigm in the pathogenesis and treatment of cancer focused on the oral microbiome and antimicrobial‐based therapies.

Impact of smokeless tobacco-associated bacteriome in oral carcinogenesis

Smokeless tobacco products possess a complex community of microorganisms. The microbial community ferment compounds present in the smokeless tobacco products and convert them into carcinogens like tobacco-associated nitrosamines. However, the potential of smokeless tobacco products associated bacteriome to manipulate systemic inflammation and other signaling pathways involved in the etiology of oral cancer will be a risk factor for oral cancer. Further, damage to oral epithelial cells causes a leaky oral layer that leads to increased infiltration of bacterial components like lipopolysaccharide, flagellin, and toxins, etc. The consumption of smokeless tobacco products can cause damage to the oral layer and dysbiosis of oral microbiota. Hence, the enrichment of harmful microbes due to dysbiosis in the oral cavity can produce high levels of bacterial metabolites and provoke inflammation as well as carcinogenesis. Understanding the complex and dynamic interrelation between the smokeless tobacco-linked bacteriome and host oral microbiome may help to unravel the mechanism of oral carcinogenesis stimulated by smokeless tobacco products. This review provides an insight into smokeless tobacco product-associated bacteriome and their potential in the progression of oral cancer. In the future, this will guide in the evolution of prevention and treatment strategies against smokeless tobacco products-induced oral cancer. Besides, it will assist the government organizations for better management and cessation policy building for the worldwide problem of smokeless tobacco addiction.

Effect of probiotic Lactobacillus rhamnosus by-products on gingival epithelial cells challenged with Porphyromonas gingivalis

OBJECTIVE

Probiotics are usually given as living cells, but their effects may be also achieved by postbiotics. We hypothesized that probiotics products (spent media and lysate) altered the response induced by P. gingivalis in gingival epithelial cells (GECS).

METHODS

Immortalized human OBA-9 GECs (∼2,5 × 10⁵cells/well) were challenged with P. gingivalis ATCC33277, and co-infected with L. rhamnosus Lr-32 for 4 h. L. rhamnosus Lr-32 spent medium or cells lysate was added to GECs co-infected with P. gingivalis. Another set of OBA-9 GECs were first exposed to P. gingivalis ATCC 33277 and then to the living probiotic or probiotic products. Transcription of genes encoding inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) and receptors (TLR2 and TLR4) were evaluated by RT-qPCR. P. gingivalis growth under L. rhamnosus Lr-32 postbiotics was also evaluated.

RESULTS

L. rhamnosus Lr-32 spent media decreased cell viability, while living cells and cell lysates did not. L. rhamnosus Lr-32 lysate, but not spent media, upregulated transcription of inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) in GECs infected with P. gingivalis. Transcription of TRL2 was upregulated in all experimental groups compared to control, whereas TLR4 was upregulated by the probiotic or its postbiotics in P. gingivalis infected cells. Spent media and lysates reduced the growth of P. gingivalis.

CONCLUSION

L. rhamnosus Lr-32 cell components rather than live probiotic enhanced the expression of inflammatory mediators in P. gingivalis infected gingival epithelial cells. The increased potential of Lr-32 cell lysates to promote immune response to the periodontopathogen may favor pathogen elimination but may also lead to additional deleterious effects of the exacerbated inflammation.

Antibacterial Properties of Small-Size Peptide Derived from Penetratin against Oral Streptococci

Periodontitis, an infectious disease originating from dental biofilms that causes the irreversible loss of alveolar bone, is accompanied by gradual biofilm formation and the continuous progression of inflammation. A small peptide derived from penetratin, Arg-Gln-Ile-Arg-Arg-Trp-Trp-Gln-Arg-NH₂ (RR9), appears to have antibacterial properties against selected strains associated with periodontitis. The purpose of this research is to assess the antibacterial activity and mechanism of RR9 against the initial oral colonizers Streptococci oralis, Streptococci gordonii, and Streptococci sanguinis and to investigate the cytotoxicity of RR9 on human gingival fibroblasts in vitro. The effects of RR9 on the initial oral settlers of planktonic and biofilm states were evaluated by measuring the MIC, MBC, bactericidal kinetics, and antibiofilm activity. Visual evidence and antibacterial mechanisms were identified, and the anti-inflammatory activity and cytotoxicity were measured. The results demonstrated that RR9 can inhibit the growth of streptococci in the planktonic state and during biofilm formation in vitro while keeping a low toxicity against eukaryotic cells. The antibacterial mechanism was proven to be related to the lower expression of sspA in streptococci. RR9 may be used as a potential antimicrobial and anti-infective agent for periodontal disease.

Exacerbation of AMD Phenotype in Lasered CNV Murine Model by Dysbiotic Oral Pathogens

Emerging evidence underscores an association between age-related macular degeneration (AMD) and periodontal disease (PD), yet the biological basis of this linkage and the specific role of oral dysbiosis caused by PD in AMD pathophysiology remains unclear. Furthermore, a simple reproducible model that emulates characteristics of both AMD and PD has been lacking. Hence, we established a novel AMD+PD murine model to decipher the potential role of oral infection (ligature-enhanced) with the keystone periodontal pathogen Porphyromonas gingivalis, in the progression of neovasculogenesis in a laser-induced choroidal-neovascularization (Li-CNV) mouse retina. By a combination of fundus photography, optical coherence tomography, and fluorescein angiography, we documented inflammatory drusen-like lesions, reduced retinal thickness, and increased vascular leakage in AMD+PD mice retinae. H&E further confirmed a significant reduction of retinal thickness and subretinal drusen-like deposits. Immunofluorescence microscopy revealed significant induction of choroidal/retinal vasculogenesis in AMD+PD mice. qPCR identified increased expression of oxidative-stress, angiogenesis, pro-inflammatory mediators, whereas antioxidants and anti-inflammatory genes in AMD+PD mice retinae were notably decreased. Through qPCR, we detected Pg and its fimbrial 16s-RrNA gene expression in the AMD+PD mice retinae. To sum-up, this is the first in vivo study signifying a role of periodontal infection in augmentation of AMD phenotype, with the aid of a pioneering AMD+PD murine model established in our laboratory.

Effect of Aging on Homeostasis in the Soft Tissue of the Periodontium: A Narrative Review

Aging is characterized by a progressive decline or loss of physiological functions, leading to increased susceptibility to disease or death. Several aging hallmarks, including genomic instability, cellular senescence, and mitochondrial dysfunction, have been suggested, which often lead to the numerous aging disorders. The periodontium, a complex structure surrounding and supporting the teeth, is composed of the gingiva, periodontal ligament, cementum, and alveolar bone. Supportive and protective roles of the periodontium are very critical to sustain life, but the periodontium undergoes morphological and physiological changes with age. In this review, we summarize the current knowledge of molecular and cellular physiological changes in the periodontium, by focusing on soft tissues including gingiva and periodontal ligament.

Clinical and microbiological effects of adjunctive photodynamic diode laser therapy in the treatment of chronic periodontitis: A randomized clinical trial

Background. Conventional mechanical debridement alone cannot eliminate bacteria and their products from periodontal pockets. Adjunctive therapies improve tissue healing through detoxification and bactericidal effects. Photodynamic therapy (PDT) is a non-invasive treatment procedure that involves the use of a dye as a photosensitizer to attach to the target cell and be activated by a photon of an appropriate wavelength. This study aimed to assess the effectiveness of PDT in treating periodontitis as an adjunct to scaling and root planing.

Methods. Fifteen subjects with chronic periodontitis were treated randomly with scaling and root planing (SRP), followed by a single PDT (test) or SRP (control) episode alone. Full-mouth plaque index (PI), sulcus bleeding index (SBI), probing depth (PD), and clinical attachment level (CAL) were assessed at baseline and 1-month and 3-month intervals. Microbiological evaluation of Porphyromonas gingivalis (Pg) in subgingival plaque samples was performed using a commercially available real-time polymerase chain reaction.

Results. The results revealed a significant difference in PI, SBI, PD, CAL, and microbiological parameters between the groups one and three months after treatment.

Conclusion. A combination of PDT and SRP gave rise to a significant improvement in clinical and microbiological parameters in patients with chronic periodontitis.

Applying nano-HA in addition to scaling and root planing increases clinical attachment gain

Purpose

This study evaluated the efficacy of treating periodontitis using subgingival nano-hydroxyapatite powder with an air abrasion device (NHAPA) combined with scaling and root planing (SRP).

Methods

A total of 28 patients with stage III periodontitis (grade B) were included in this study, although 1 was lost during follow-up and 3 used antibiotics. The patients were divided into a test group and a control group. All patients first received whole-mouth SRP using hand instruments, and a split-mouth approach was used for the second treatment. In the test group, the teeth were treated with NHAPA for 15 seconds at 70% power per pocket. Subgingival plaque samples were obtained from the 2 deepest pockets at the test and control sites before treatment (baseline) and 3 months after treatment. The full-mouth plaque index (PI), gingival index (GI), papillary bleeding index (PBI), bleeding on probing (BOP), probing depth (PD) and clinical attachment level (CAL) were recorded at baseline and at 1- and 3-month post-treatment. Real-time polymerase chain reaction was used to determine the colonisation of Treponema denticola (Td), Porphyromonas gingivalis (Pg), and Aggregatibacter actinomycetemcomitans in the subgingival plaque.

Results

From baseline to the first month, the test group showed significantly larger changes in BOP and CAL (43.705%±27.495% and 1.160±0.747 mm, respectively) than the control group (36.311%±27.599% and 0.947±0.635 mm, respectively). Periodontal parameters had improved in both groups at 3 months. The reductions of PI, GI, BOP, PD, and CAL in the test group at 3 months were greater and statistically significant. The total bacterial count and Td and Pg species had decreased significantly by the third month in both groups (P<0.05).

Conclusions

Applying NHAPA in addition to SRP improves clinical periodontal parameters more than SRP alone. Subgingival NHAPA may encourage clot adhesion to tooth surfaces by increasing surface wettability.

Oral Dysbiosis and Autoimmunity: From Local Periodontal Responses to an Imbalanced Systemic Immunity. A Review

The current paradigm of onset and progression of periodontitis includes oral dysbiosis directed by inflammophilic bacteria, leading to altered resolution of inflammation and lack of regulation of the inflammatory responses. In the construction of explanatory models of the etiopathogenesis of periodontal disease, autoimmune mechanisms were among the first to be explored and historically, for more than five decades, they have been described in an isolated manner as part of the tissue damage process observed in periodontitis, however direct participation of these mechanisms in the tissue damage is still controversial. Autoimmunity is affected by genetic and environmental factors, leading to an imbalance between the effector and regulatory responses, mostly associated with failed resolution mechanisms. However, dysbiosis/infection and chronic inflammation could trigger autoimmunity by several mechanisms including bystander activation, dysregulation of toll-like receptors, amplification of autoimmunity by cytokines, epitope spreading, autoantigens complementarity, autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, and activation or inhibition of receptors related to autoimmunity by microorganisms. Even though autoreactivity in periodontitis is biologically plausible, the associated mechanisms could be related to non-pathologic responses which could even explain non-recognized physiological functions. In this review we shall discuss from a descriptive point of view, the autoimmune mechanisms related to periodontitis physio-pathogenesis and the participation of oral dysbiosis on local periodontal autoimmune responses as well as on different systemic inflammatory diseases.

[Research progress in the relationship between Veillonella and oral diseases]

Veillonella species, known as the early colonizer of oral biofilm, are prevalent in oral microbiota. Seven Veillonella species have been isolated from oral cavity. Their distribution varies not only with different people but also with different sites in the oral cavity. Oral Veillonella are associated with oral diseases. They contribute to the adhesion of Streptococcus mutans and consume the lactate generated by streptococci. Veillonella species play an important role in the occurrence and development of periodontal diseases by providing adhesion sites for Porphyromonas gingivalis and boosting immune responses. The production of lipopolysaccharide and H2S is related to other oral diseases, such as pulpitis, periapical periodontitis, and halitosis. Several studies have been conducted on the relationship between Veillonella and oral diseases and the interaction between Veillonella and other pathological microorganisms, but limited knowledge is available at the molecular level. This article reviews the research progress in the relationship between Veillonella and oral infectious diseases, such as dental caries and periodontal diseases.

Oral Pathogen Porphyromonas gingivalis Can Escape Phagocytosis of Mammalian Macrophages

Macrophages are phagocytic cells that play a key role in host immune response and clearance of microbial pathogens. Porphyromonas gingivalis is an oral pathogen associated with the development of periodontitis. Escape from macrophage phagocytosis was tested by infecting THP-1-derived human macrophages and RAW 264.7 mouse macrophages with strains of P. gingivalis W83 and 33277 as well as Streptococcus gordonii DL1 and Escherichia coli OP50 at MOI = 100. CFU counts for all intracellular bacteria were determined. Then, infected macrophages were cultured in media without antibiotics to allow for escape and escaping bacteria were quantified by CFU counting. P. gingivalis W83 displayed over 60% of the bacterial escape from the total amount of intracellular CFUs, significantly higher compared to all other bacteria strains. In addition, bacterial escape and re-entry were also tested and P. gingivalis W83, once again, showed the highest numbers of CFUs able to exit and re-enter macrophages. Lastly, the function of the PG0717 gene of P. gingivalis W83 was tested on escape but found not related to this activity. Altogether, our results suggest that P. gingivalis W83 is able to significantly avoid macrophage phagocytosis. We propose this ability is likely linked to the chronic nature of periodontitis.

A Novel Small Molecule, 1,3-di-m-tolyl-urea, Inhibits and Disrupts Multispecies Oral Biofilms

An imbalance of homeostasis between the microbial communities and the host system leads to dysbiosis in oral micro flora. DMTU (1,3-di-m-tolyl-urea) is a biocompatible compound that was shown to inhibit Streptococcus mutans biofilm by inhibiting its communication system (quorum sensing). Here, we hypothesized that DMTU is able to inhibit multispecies biofilms. We developed a multispecies oral biofilm model, comprising an early colonizer Streptococcus gordonii, a bridge colonizer Fusobacterium nucleatum, and late colonizers Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. We performed comprehensive investigations to demonstrate the effect of DMTU on planktonic cells and biofilms. Our findings showed that DMTU inhibits and disrupts multispecies biofilms without bactericidal effects. Mechanistic studies revealed a significant down regulation of biofilm and virulence-related genes in P. gingivalis. Taken together, our study highlights the potential of DMTU to inhibit polymicrobial biofilm communities and their virulence.

Intracellular Porphyromonas gingivalis Promotes the Tumorigenic Behavior of Pancreatic Carcinoma Cells

Porphyromonas gingivalis is a member of the dysbiotic oral microbiome associated with oral inflammation and periodontal disease. Intriguingly, epidemiological studies link P. gingivalis to an increased risk of pancreatic cancer. Given that oral bacteria are detected in human pancreatic cancer, and both mouse and human pancreata harbor microbiota, we explored the involvement of P. gingivalis in pancreatic tumorigenesis using cell lines and a xenograft model. Live P. gingivalis induced proliferation of pancreatic cancer cells; however, surprisingly, this effect was independent of Toll-like receptor 2, the innate immune receptor that is engaged in response to P. gingivalis on other cancer and immune cells, and is required for P. gingivalis to induce alveolar bone resorption. Instead, we found that P. gingivalis survives inside pancreatic cancer cells, a trait that can be enhanced in vitro and is increased by hypoxia, a central characteristic of pancreatic cancer. Increased tumor cell proliferation was related to the degree of intracellular persistence, and infection of tumor cells with P. gingivalis led to enhanced growth in vivo. To the best of our knowledge, this study is the first to demonstrate the direct effect of exposure to P. gingivalis on the tumorigenic behavior of pancreatic cancer cell lines. Our findings shed light on potential mechanisms underlying the pancreatic cancer–periodontitis link.

Porphyromonas gingivalis adopts intricate and unique molecular mechanisms to survive and persist within the host: a critical update

is an obligate, asaccharolytic, gram-negative bacteria commonly associated with increased periodontal and systemic inflammation. P. gingivalis is known to survive and persist within the host tissues as it modulates the entire ecosystem by either engineering its environment or modifying the host's immune response. It interacts with various host receptors and alters signaling pathways of inflammation, complement system, cell cycle, and apoptosis. P. gingivalis is even known to induce suicidal cell death of the host and other microbes in its vicinity with the emergence of pathobiont species. Recently, new molecular and immunological mechanisms and virulence factors of P. gingivalis that increase its chance of survival and immune evasion within the host have been discovered. Thus, the present paper aims to provide a consolidated update on the new intricate and unique molecular mechanisms and virulence factors of P. gingivalis associated with its survival, persistence, and immune evasion within the host.

Well-maintained patients with a history of periodontitis still harbor a more dysbiotic microbiome than health

BACKGROUND

It remains unclear whether well-maintained subjects, with periodontitis in the past, effectively treated, and maintained for a long time, have the same subgingival microbiome as healthy subjects. Therefore, the objective of this study was to investigate the characteristics of the subgingival microbiome in well-maintained patients with a history of periodontitis compared with healthy subjects.

METHODS

We recruited in 17 well-maintained individuals (no evidence of clinical inflammation and progress of periodontitis) and 21 healthy individuals. Periodontal clinical parameters, consisting of missing teeth, plaque index (PLI), periodontal depth (PD), and bleeding index (BI), were recorded and analyzed. The pooled subgingival samples from mesiobuccal sites of two maxillary first molars were collected. The V3-V4 region of 16S rRNA gene from 38 subgingival samples was sequenced and analyzed. Alpha diversity, microbial composition, types of bacteria, functional pathways between well-maintained group and health group were compared using Mann-Whitney U test. Spearman correlation was used in analyzing the symbiotic relationship among taxa. A classification model was constructed to distinguish two ecological types.

RESULTS

The maintained individuals demonstrated a different microbiome from healthy subjects, with higher diversity, more disordered structure, more pathogenic microbiota, and more host-destructive metabolism pathways. The genera Actinomyces, Streptococcus, Leptotrichia, Capnocytophaga, Lautropia, and Fusobacterium were predominant components with relative abundance >5% in the subgingival microbiome of well-maintained patients. The classification model by microbiota got a remarkable accuracy of 83.33%.

CONCLUSIONS

Individuals with well-maintained periodontitis showed a more dysbiotic microbial community than healthy individuals. Therefore, close monitoring and scheduled maintenance treatment are necessary for them to maintain a healthy periodontal condition.

In Vitro Homeostasis of Rat Oral Epithelial Cell Cultures Following Withdrawal of Periodontal Pathogens

Inflammation of periodontal tissues is the consequence of interaction between periodontal pathogens and immune system. This is associated with increased expression of inflammatory cytokines, which may exert destructive effect to the periodontal tissues when released over long period. The aim of this study was to chronologically track the homeostasis of oral keratinocytes following removal of periodontal pathogens. This was done by investigating expression of selected inflammatory markers and integrity of epithelial monolayers in vitro. Rat oral keratinocytes were stimulated with heat-killed Fusobacterium nucleatum and Porphyromonas gingivalis over 7-days then bacteria were washed away and epithelial cells re-cultured for 3-days. Expression of IL-1β, IL-6, and IL-8 was measured by ELISA while transcription of tissue inhibitor of metalloproteinase-1 (TIMP-1) and matrix metalloproteinase -8 (MMP-8) was measured by polymerase chain reaction before and after removal of bacteria. Integrity of epithelial sheet was investigated by using transepithelial electrical resistance. Data showed general downregulation of IL-1b, IL-6, and IL-8 associated with restoring transcription of TIMP-1 and MMP-8 to normal level following removal of bacteria from epithelial cultures. However, expression of IL-8 and MMP-8 remained significantly higher than unstimulated epithelial cells despite withdrawal of F. nucleatum and P. gingivalis respectively from oral keratinocytes cultures. In addition, integrity of epithelial barrier function remained compromised even after removal of P. gingivalis. Results suggest that even after three days following removal of periodontal pathogens, oral keratinocytes sustained persistent upregulation of certain inflammatory markers that could compromise integrity of epithelial barrier function.

Interleukin-1α and -1β assessment in the gingival crevicular fluid of periodontal patients with chronic hepatitis C

The study assessed whether the increased production of interleukin-1α (IL-1α) and interleukin-1β (IL-1β), as a result of chronic hepatic inflammation, could be the expression of the negative impact on periodontal disease. The study included chronic periodontitis patients who were systemically healthy, chronic periodontitis patients suffering from chronic hepatitis C, as well as control patients, being systemically and periodontally healthy. After periodontal examination and the assessment of certain periodontal parameters, gingival crevicular fluid was collected from all participating patients. By using the enzyme-linked immunosorbent assay method, a quantitative assessment of IL-1α and IL-1β levels was possible. The immunologic results were correlated to the clinical periodontal data. The gingival fluid levels of cytokines were higher for periodontitis patients with chronic hepatitis C than for the systemically healthy periodontitis patients (1.8-fold higher for IL-1α and 2.1-fold higher for IL-1β). In addition, the gingival fluid cytokine levels were significantly higher for the periodontal patients (with/without chronic hepatitis C) than for the control group. Positive correlations were found between gingival fluid IL-1α and IL-1β levels and certain clinical periodontal parameters or the age of the viral hepatitis C diagnosis, in periodontitis patients with chronic hepatitis C. The chronic hepatic inflammation may have an important additional negative impact on the periodontal status, as both inflammatory reactions seem to be promoted by common pro-inflammatory cytokines.

Better oral hygiene is associated with lower risk of stroke

BACKGROUND

Periodontal disease or poor oral hygiene may lead to local infection, inflammation, and systemic inflammatory reactions, which are important mediators of development of stroke. We aimed to investigate the association of oral hygiene with risk of stroke in a nationwide population-based cohort.

METHODS

From Korean National Health Insurance System-Health Screening Cohort, 206,602 participants without missing data regarding demographic information, medical history, or blood/urine examination results were included. The presence of periodontal disease and indicators of oral hygiene, such as number of tooth brushings, dental visit history, dental scaling, and number of teeth loss and dental caries were evaluated. Occurrence of stroke including cerebral infarction, cerebral hemorrhage, and subarachnoid hemorrhage was defined as newly registration of International Classification of Diseases-10 codes from I60 to I64 accompanying brain CT and/or MR examination at that time of diagnosis.

RESULTS

The 7337 (3.6%) cases of stroke including 5795 (79.0%) cases of cerebral infarction, 1568 (21.4%) cases of cerebral hemorrhage, and 621 (8.5%) cases of subarachnoid hemorrhage occurred during a median 10.4 years follow-up. In multivariable analysis, frequent tooth brushing (≥3 times per day) was negatively associated with risk of stroke occurrence (hazard ratio [HR]: 0.78, 95% confidence interval [CI]: 0.73-0.84). Number of dental caries (≥4) was positively related to stroke occurrence (HR: 1.28, 95% CI: 1.13-1.44).

CONCLUSIONS

Regular oral hygiene behavior was negatively, and infrequent oral hygiene care was positively associated with risk of occurrence for stroke, respectively. Brushing one's teeth three or more times daily may be associated with lower risk of stroke.

Effect of Hydrogen Peroxide Photoactivated Decontamination Using 940 nm Diode Laser in Periodontal Treatment: A Pilot Study

Objective: The aim of this study was to compare the antimicrobial effects of hydroxyl radical generation by photoactivation of hydrogen peroxide (H₂O₂) with diode laser (λ = 940 nm) in combination with conventional nonsurgical periodontal therapy. Materials and methods: Thirty-eight patients and 114 teeth were included in this study. The test teeth were randomly assigned to one of the three treatment groups: Group 1 (control group): scaling and root planning (SRP); and the following experimental groups: Group 2: SRP +940 nm diode laser; Group 3: SRP+photoactivation of H₂O₂ with 940 nm diode laser. Clinical examinations, such as periodontal probing depth (PPD), clinical attachment level (CAL), and bleeding on probing (BoP) were performed before and after the treatment. The microbiological evaluation included nine periodontal bacterial species investigated by means of real-time polymerase chain reaction assay before and after the treatment. The clinical and bacterial differences were assessed between the investigated groups. Results: The total bacteria load was reduced for all three studied groups and all periodontal indexes (PPD, CAL, and BoP) were improved after each treatment. Group 3 showed significant bacterial reduction of the major periodontal bacteria such as Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Prevotella intermedia, Peptostreptococcus micros, Fusobacterium nucleatum, Eubacterium nodatum (p < 0.001) in contrast to the other two groups (p > 0.001). Differences between tested groups showed significant results with regard to Group 3. Conclusions: The synergistic effect of SRP and photoactivation of H₂O₂ with 940 nm diode laser offers an efficient and reliable antimicrobial effect in the nonsurgical periodontal treatment approach.