The composition of dental plaque has been well defined, whereas currently there is limited understanding of the composition of denture plaque and how it directly influences denture related stomatitis ...(DS). The aims of this study were to compare the microbiomes of denture wearers, and to understand the implications of these towards inter-kingdom and host-pathogen interactions within the oral cavity.
Swab samples were obtained from 123 participants wearing either a complete or partial denture; the bacterial composition of each sample was determined using bar-coded illumina MiSeq sequencing of the bacterial hypervariable V4 region of 16S rDNA. Sequencing data processing was undertaken using QIIME, clustered in Operational Taxonomic Units (OTUs) and assigned to taxonomy. The dentures were sonicated to remove the microbial flora residing on the prosthesis, sonicate was then cultured using diagnostic colorex Candida media. Samples of unstimulated saliva were obtained and antimicrobial peptides (AMP) levels were measured by ELISA.
We have shown that dental and denture plaques are significantly distinct both in composition and diversity and that the oral microbiome composition of a denture wearer is variable and is influenced by the location within the mouth. Dentures and mucosa were predominantly made up of Bacilli and Actinobacteria. Moreover, the presence of natural teeth has a significant impact on the overall microbial composition, when compared to the fully edentulous. Furthermore, increasing levels of Candida spp. positively correlate with Lactobacillus spp. AMPs were quantified, though showed no specific correlations.
This is the first study to provide a detailed understanding of the oral microbiome of denture wearers and has provided evidence that DS development is more complex than simply a candidal infection. Both fungal and bacterial kingdoms clearly play a role in defining the progression of DS, though we were unable to show a defined role for AMPs.
Background
Dental procedures often produce aerosol and splatter which have the potential to transmit pathogens such as SARS‐CoV‐2. The existing literature is limited.
Objective(s)
To develop a ...robust, reliable and valid methodology to evaluate distribution and persistence of dental aerosol and splatter, including the evaluation of clinical procedures.
Methods
Fluorescein was introduced into the irrigation reservoirs of a high‐speed air‐turbine, ultrasonic scaler and 3‐in‐1 spray, and procedures were performed on a mannequin in triplicate. Filter papers were placed in the immediate environment. The impact of dental suction and assistant presence were also evaluated. Samples were analysed using photographic image analysis and spectrofluorometric analysis. Descriptive statistics were calculated and Pearson's correlation for comparison of analytic methods.
Results
All procedures were aerosol and splatter generating. Contamination was highest closest to the source, remaining high to 1‐1.5 m. Contamination was detectable at the maximum distance measured (4 m) for high‐speed air‐turbine with maximum relative fluorescence units (RFU) being: 46,091 at 0.5 m, 3,541 at 1.0 m and 1,695 at 4 m. There was uneven spatial distribution with highest levels of contamination opposite the operator. Very low levels of contamination (≤0.1% of original) were detected at 30 and 60 minutes post‐procedure. Suction reduced contamination by 67‐75% at 0.5‐1.5 m. Mannequin and operator were heavily contaminated. The two analytic methods showed good correlation (r = 0.930, n = 244, P < .001).
Conclusion
Dental procedures have potential to deposit aerosol and splatter at some distance from the source, being effectively cleared by 30 minutes in our setting.
Background
To evaluate possible effects of smoking on clinical, biochemical, and microbiological outcomes of non‐surgical periodontal treatment in patients with periodontitis Stage III or IV and ...Grade C.
Methods
Conventional quadrant‐wise non‐surgical periodontal treatment was performed and whole‐mouth periodontal measurements were recorded at baseline, 1, 3, and 6 months after completion of treatment. Saliva, gingival crevicular fluid, subgingival plaque, and blood samples were obtained at the same time points. Inflammatory cytokine levels, presence, and quantities of 11 different bacterial species were determined. Smoking status was validated by cotinine assay.
Results
Fourteen smoker and 13 non‐smoker patients completed the study protocol and revealed similar clinical findings except for the higher plaque scores in the non‐smokers at 6 months (P <0.01). Significant differences were found between the study groups in biofluid cytokine levels at 1 and 3 months (P <0.01). Gram‐negative bacteria were more abundant in the smokers at baseline and so were Gram‐positive bacteria in the non‐smokers (P <0.01). Gram‐negative bacteria repopulated in the smokers faster than in the non‐smokers (P <0.01).
Conclusions
The present findings suggest that smoker patients with periodontitis Stage III and IV, Grade C respond well to the non‐surgical periodontal treatment during the 6‐month follow‐up. However, smokers exhibit faster repopulation of Gram‐negative bacteria.
Background: This cross‐sectional study assesses cytokine levels in peri‐implant crevicular fluid (PICF)/gingival crevicular fluid (GCF) and a selection of subgingival/submucosal plaque bacteria from ...clinically healthy or diseased sites in the same individuals.
Methods: Samples from 97 implants/teeth (58 implants 19 healthy, 20 mucositis, 19 peri‐implantitis and 39 natural teeth 19 healthy, 12 gingivitis, eight periodontitis in 15 systemically healthy patients were investigated by immunoassay and real‐time polymerase chain reaction. Samples were obtained first, with probing depth, clinical attachment level, bleeding on probing, plaque index scores, and keratinized tissue width then recorded. Data were analyzed by Wilcoxon, Mann–Whitney U, and permutation tests on dependent, independent, and mixed dependent and independent samples and Spearman correlation.
Results: Interleukin (IL)‐1β levels were significantly higher in PICF samples of healthy implants than in GCF samples of healthy teeth (P = 0.003), and soluble receptor activator of nuclear factor‐κB ligand (sRANKL) concentrations were significantly higher in the gingivitis than the mucositis group (P = 0.004). Biomarker levels were similar in peri‐implantitis and periodontitis groups (P >0.05). Actinomyces naeslundi and Streptococcus oralis levels were significantly higher in the healthy implant group than in healthy teeth (P <0.05). Prevotella intermedia and Treponema denticola (Td) levels were lower in the mucositis group than the gingivitis group (P <0.05). Prevotella oralis and S. oralis levels were significantly higher in the periodontitis group (P <0.05), and Td levels were significantly higher in the peri‐implantitis group (P <0.05).
Conclusion: There were many similarities but, crucially, some differences in biomarker levels (IL‐1β and sRANKL) and bacterial species between peri‐implant and periodontal sites in the same individuals, suggesting similar pathogenic mechanisms.
Mesenchymal stem cells (MSCs) are well known for their regenerative potential. Even though the ability of MSCs to proliferate and differentiate has been studied extensively, there remains much to ...learn about the signaling mechanisms and pathways that control proliferation and influence the differentiation phenotype. In recent years, there has been growing evidence for the utility of non-neuronal cholinergic signaling systems and that acetylcholine (ACh) plays an important ubiquitous role in cell-to-cell communication. Indeed, cholinergic signaling is hypothesized to occur in stem cells and ACh synthesis, as well as in ACh receptor (AChR) expression, has been identified in several stem cell populations, including MSCs. Furthermore, AChRs have been found to influence MSC regenerative potential. In humans, there are two major classes of AChRs, muscarinic AChRs and nicotinic AChRs, with each class possessing several subtypes or subunits. In this review, the expression and function of AChRs in different types of MSC are summarized with the aim of highlighting how AChRs play a pivotal role in regulating MSC regenerative function.
Endodontic disease, a biofilm infection of the root canal space, is a significant cause of dental morbidity worldwide. Endodontic treatment, or root canal treatment, as it is commonly known is ...founded on the ability to eradicate microbial biofilm infection and prevent re-infection of the highly complex root canal space. Despite many "advances" in clinical endodontics we have seen little improvement in outcomes. The aim of this critical review paper is to provide a contemporary view of endodontic microbiology and biofilm polymicrobiality, provide an understanding of the host response, and how together these impact upon clinical treatment. Ultimately, it is intended to provide insight into novel opportunities and strategies for the future diagnostics, treatment, and prevention of endodontic disease.
Neuropathic pain, a debilitating condition with unmet medical needs, can be characterised as hyperexcitability of nociceptive neurons caused by dysfunction of ion channels. Voltage-gated potassium ...channels type 7 (Kv7), responsible for maintaining neuronal resting membrane potential and thus excitability, reside under tight control of G protein-coupled receptors (GPCRs). Calcium-sensing receptor (CaSR) is a GPCR that regulates the activity of numerous ion channels, but whether CaSR can control Kv7 channel function has been unexplored until now.
Experiments were conducted in recombinant cell models, mouse dorsal root ganglia (DRG) neurons and human induced pluripotent stem cell (hiPSC)-derived nociceptive-like neurons using patch-clamp electrophysiology and molecular biology techniques.
Our results demonstrate that CaSR is expressed in recombinant cell models, hiPSC-derived nociceptive-like neurons and mouse DRG neurons, and its activation induced depolarisation via Kv7.2/7.3 channel inhibition. The CaSR-Kv7.2/7.3 channel crosslink was mediated via the G
protein-adenylate cyclase-cyclicAMP-protein kinase A signalling cascade. Suppression of CaSR function demonstrated a potential to rescue hiPSC-derived nociceptive-like neurons from algogenic cocktail-induced hyperexcitability.
This study demonstrates that the CaSR-Kv7.2/7.3 channel crosslink, via a G
protein signalling pathway, effectively regulates neuronal excitability, providing a feasible pharmacological target for neuronal hyperexcitability management in neuropathic pain.
Background and Purpose
Neuropathic pain, a debilitating condition with unmet medical needs, can be characterised as hyperexcitability of nociceptive neurons caused by dysfunction of ion channels. ...Voltage‐gated potassium channels type 7 (Kv7), responsible for maintaining neuronal resting membrane potential and thus excitability, reside under tight control of G protein‐coupled receptors (GPCRs). Calcium‐sensing receptor (CaSR) is a GPCR that regulates the activity of numerous ion channels, but whether CaSR can control Kv7 channel function has been unexplored until now.
Experimental Approach
Experiments were conducted in recombinant cell models, mouse dorsal root ganglia (DRG) neurons and human induced pluripotent stem cell (hiPSC)‐derived nociceptive‐like neurons using patch‐clamp electrophysiology and molecular biology techniques.
Key Results
Our results demonstrate that CaSR is expressed in recombinant cell models, hiPSC‐derived nociceptive‐like neurons and mouse DRG neurons, and its activation induced depolarisation via Kv7.2/7.3 channel inhibition. The CaSR‐Kv7.2/7.3 channel crosslink was mediated via the Gi/o protein‐adenylate cyclase‐cyclicAMP‐protein kinase A signalling cascade. Suppression of CaSR function demonstrated a potential to rescue hiPSC‐derived nociceptive‐like neurons from algogenic cocktail‐induced hyperexcitability.
Conclusion and Implications
This study demonstrates that the CaSR‐Kv7.2/7.3 channel crosslink, via a Gi/o protein signalling pathway, effectively regulates neuronal excitability, providing a feasible pharmacological target for neuronal hyperexcitability management in neuropathic pain.
The use of natural compounds as an alternative source of antimicrobials has become a necessity given the growing concern over global antimicrobial resistance. Polyphenols, found in various edible ...plants, offers one potential solution to this. We aimed to investigate the possibility of using curcumin within the context of oral health as a way of inhibiting and preventing the harmful development of
biofilms. We undertook a series of adsorption experiments with varying concentrations of curcumin, showing that 50 μg/ml could prevent adhesion. This effect could be further synergized by the curcumin pre-treatment of yeast cells to obtain significantly greater inhibition (>90%,
< 0.001). Investigation of the biological impact of curcumin showed that it preferentially affected immature morphological forms (yeast and germlings), and actively promoted aggregation of the cells. Transcriptional analyses showed that key adhesins were down-regulated (ALS1 and ALS3), whereas aggregation related genes (ALS5 and AAF1) were up-regulated. Collectively, these data demonstrated that curcumin elicits anti-adhesive effects and that induces transcription of genes integrally involved in the processes related to biofilm formation. Curcumin and associated polyphenols therefore have the capacity to be developed for use in oral healthcare to augment existing preventative strategies for candidal biofilms on the denture surface.
Interleukin-33 (IL-33) is an IL-1 family cytokine that has a role in regulating T helper type 2 cytokines and mast cell development. Expression of IL-33 is also associated with chronic inflammatory ...conditions such as rheumatoid arthritis. However, there is little information regarding IL-33 in myeloid cell immune responses, which are important in immunity and inflammation. We therefore investigated the expression, intracellular location and regulation of myeloid cell IL-33 by lipopolysaccharide (LPS) from Escherichia coli and the periodontal pathogen Porphyromonas gingivalis. We detected IL-33 messenger RNA in the human promonocytic cell line THP-1, in monocytes derived from these cells and in primary human monocytes. However, IL-33 was not expressed in primary monocyte-derived dendritic cells. Stimulation of monocytes with E. coli LPS (Toll-like receptor 4 agonist) and LPS from P. gingivalis (Toll-like receptor 2 agonist) up-regulated IL-33 at both the messenger RNA and protein levels but IL-1β and tumour necrosis factor-α had no effect. The IL-33 protein was mainly found in the cytoplasm of monocytes with no evidence of nuclear translocation in stimulated cells. Furthermore, no IL-33 secretion was detected after stimulation with LPS and/or ATP. These data indicate that the function, if any, of IL-33 in activated monocytes is primarily intracellular. Interestingly, immunofluorescence analysis indicated that IL-33 was sequestered in the nucleus of monocytes undergoing apoptosis but released into the extracellular milieu by LPS-stimulated cells in which necrosis had been induced by freeze-thawing. Therefore, this endorses the view that IL-33 may function as an 'alarmin' and have a role in signalling cellular damage and inflammatory disease pathogenesis through release from damaged or necrotic cells.
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