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1.
Metabolic Signaling and Spatial Interactions in the Oral Polymicrobial Community.
Miller, DP, Fitzsimonds, ZR, Lamont, RJ
Journal of dental research. 2019;(12):1308-1314
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Abstract
Oral supra- and subgingival biofilms are complex communities in which hundreds of bacteria, viruses, and fungi reside and interact. In these social environments, microbes compete and cooperate for resources, such as living space and nutrients. The metabolic activities of bacteria can transform their microenvironment and dynamically influence the fitness and growth of cohabitating organisms. Biofilm communities are temporally and spatially organized largely due to cell-to-cell communication, which promotes synergistic interactions. Metabolic interactions maintain biofilm homeostasis through mutualistic cross-feeding, metabolic syntrophy, and cross-respiration. These interactions include reciprocal metabolite exchanges that promote the growth of physiologically compatible bacteria, processive catabolism of complex substrates, and unidirectional interactions that are globally important for the polymicrobial community. Additionally, oral bacterial interactions can lead to detoxification of oxidative compounds, which will provide protection to the community at large. It has also been established that specific organisms provide terminal electron acceptors to partner species that result in a shift from fermentation to respiration, thus increasing ATP yields and improving fitness. Indeed, many interspecies relationships are multidimensional, and the net outcome can be spatially and temporally dependent. Cross-kingdom interactions also occur as oral yeast are antagonistic to some oral bacteria, while numerous mutualistic interactions contribute to yeast-bacterial colonization, fitness in the oral community, and the pathogenesis of caries. Consideration of this social environment reveals behaviors and phenotypes that are not apparent through the study of microbes in isolation. Here, we provide a comprehensive overview of the metabolic interactions that shape the oral microbial community.
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2.
Critical Appraisal of Oral Pre- and Probiotics for Caries Prevention and Care.
Zaura, E, Twetman, S
Caries research. 2019;(5):514-526
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Abstract
In recent years, the concept of preventing caries-related microbial dysbiosis by enhancing the growth and survival of health-associated oral microbiota has emerged. In this article, the current evidence for the role of oral pre- and probiotics in caries prevention and caries management is discussed. Prebiotics are defined as "substrates that are selectively utilized by host microorganisms conferring a health benefit." With regard to caries, this would include alkali-generating substances such as urea and arginine, which are metabolized by some oral bacteria, resulting in ammonia production and increase in pH. While there is no evidence that urea added to chewing gums or mouth rinses significantly contributes to caries inhibition, multiple studies have shown that arginine in consumer products can exert an inhibitory effect on the caries process. Probiotics are "live microorganisms which when administrated in adequate amounts confer a health benefit on the host." Clinical trials have suggested that school-based programs with milk supplemented with probiotics and probiotic lozenges can reduce caries development in preschool children and in schoolchildren with high caries risk. Due to issues with research ethics (prebiotics) and risk of bias (prebiotics, probiotics), the confidence in the effect estimate is however limited. Further long-term clinical studies are needed with orally derived probiotic candidates, including the health-economic perspectives. In particular, the development and evaluation of oral synbiotic products, containing both prebiotics and a probiotic, would be of interest in the future management of dental caries.
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3.
The Role of Exopolysaccharides in Oral Biofilms.
Cugini, C, Shanmugam, M, Landge, N, Ramasubbu, N
Journal of dental research. 2019;(7):739-745
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Abstract
The oral cavity contains a rich consortium of exopolysaccharide-producing microbes. These extracellular polysaccharides comprise a major component of the oral biofilm. Together with extracellular proteins, DNA, and lipids, they form the biofilm matrix, which contributes to bacterial colonization, biofilm formation and maintenance, and pathogenesis. While a number of oral microbes have been studied in detail with regard to biofilm formation and pathogenesis, the exopolysaccharides have been well characterized for only select organisms, namely Streptococcus mutans and Aggregatibacter actinomycetemcomitans. Studies on the exopolysaccharides of other oral organisms, however, are in their infancy. In this review, we present the current research on exopolysaccharides of oral microbes regarding their biosynthesis, regulation, contributions to biofilm formation and stability of the matrix, and immune evasion. In addition, insight into the role of exopolysaccharides in biofilms is highlighted through the evaluation of emerging techniques such as pH probing of biofilm colonies, solid-state nuclear magnetic resonance for macromolecular interactions within biofilms, and super-resolution microscopy analysis of biofilm development. Finally, exopolysaccharide as a potential nutrient source for species within a biofilm is discussed.
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Potential of chitosan-based carrier for periodontal drug delivery.
Sah, AK, Dewangan, M, Suresh, PK
Colloids and surfaces. B, Biointerfaces. 2019;:185-198
Abstract
Periodontal diseases are chronic infectious diseases and are a major oral health burden. With the progress in the understanding of etiology, epidemiology and pathogenesis of periodontal diseases coupled with the understanding of the polymicrobial synergy in the dysbiotic oral microbial flora, several new therapeutic targets have been identified. The strategies to curb bacterial growth and production of factors that gradually destroy the tissue surrounding and supporting the teeth have been the cornerstone for inhibiting periodontitis. Systemic administration of antibiotics for the treatment of periodontitis have shown several drawbacks including: inadequate antibiotic concentration at the site of the periodontal pocket, a rapid decline of the plasma antibiotic concentration to sub-therapeutic levels, the development of microbial resistance due to sub-therapeutic drug levels and peak-plasma antibiotic concentrations which may be associated with various side effects. These obvious disadvantages have evoked an interest in the development of localized drug delivery systems that can provide an effective concentration of antibiotic at the periodontal site for the duration of the treatment with minimal side effects. A targeted sustained release device which could be inserted in the periodontal pocket and prolong the therapeutic levels at the site of action at a much lower dose is the need of the hour. Chitosan, a deacetylated derivative of chitin has attracted considerable attention owing to its special properties including antimicrobial efficacy, biodegradability, biocompatibility and non-toxicity. It also has the propensity to act as hydrating agent and display tissue healing and osteoinducting effect. The aim of this review is to shine a spotlight on the chitosan based devices developed for drug delivery application in the effective treatment of various periodontal disorders. The chitosan based carriers like fibers, films, sponge, microparticles, nanoparticles, gels that have been designed for sustained release of drug into the periodontal pocket are highlighted.
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The Role of Oral Cavity Biofilm on Metallic Biomaterial Surface Destruction-Corrosion and Friction Aspects.
Mystkowska, J, Niemirowicz-Laskowska, K, Łysik, D, Tokajuk, G, Dąbrowski, JR, Bucki, R
International journal of molecular sciences. 2018;(3)
Abstract
Metallic biomaterials in the oral cavity are exposed to many factors such as saliva, bacterial microflora, food, temperature fluctuations, and mechanical forces. Extreme conditions present in the oral cavity affect biomaterial exploitation and significantly reduce its biofunctionality, limiting the time of exploitation stability. We mainly refer to friction, corrosion, and biocorrosion processes. Saliva plays an important role and is responsible for lubrication and biofilm formation as a transporter of nutrients for microorganisms. The presence of metallic elements in the oral cavity may lead to the formation of electro-galvanic cells and, as a result, may induce corrosion. Transitional microorganisms such as sulfate-reducing bacteria may also be present among the metabolic microflora in the oral cavity, which can induce biological corrosion. Microorganisms that form a biofilm locally change the conditions on the surface of biomaterials and contribute to the intensification of the biocorrosion processes. These processes may enhance allergy to metals, inflammation, or cancer development. On the other hand, the presence of saliva and biofilm may significantly reduce friction and wear on enamel as well as on biomaterials. This work summarizes data on the influence of saliva and oral biofilms on the destruction of metallic biomaterials.
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Oral fungal-bacterial biofilm models in vitro: a review.
Chevalier, M, Ranque, S, Prêcheur, I
Medical mycology. 2018;(6):653-667
Abstract
Inclusion of fungi as commensals in oral biofilm is an important innovation in oral biology, and this work aimed to review the literature on the available biofilm and related disease in vitro models. Actually, thousands of bacterial and around one hundred of fungal phylotypes can colonize the oral cavity. Taxonomic profiling combined with functional expression analysis has revealed that Candida albicans, Streptococcus mutans and prominent periodontopathogens are not always present or numerically important in candidiasis, caries, or periodontitis lesions. However, C. albicans combined with Streptococcus spp. co-increase their virulence in invasive candidiasis, early childhood caries or peri-implantitis. As Candida species and many other fungi are also members of oral microcosms in healthy individuals, mixed fungal-bacterial biofilm models are increasingly valuable investigative tools, and new fungal-bacterial species combinations need to be investigated. Here we review the key points and current methods for culturing in vitro mixed fungal-bacterial models of oral biofilms. According to ecosystem under study (health, candidiasis, caries, periodontitis), protocol design will select microbial strains, biofilm support (polystyrene plate, cell culture, denture, tooth, implant), pre-treatment support (human or artificial saliva) and culture conditions. Growing mixed fungal-bacterial biofilm models in vitro is a difficult challenge. But reproducible models are needed, because oral hygiene products, food and beverage, medication, licit and illicit drugs can influence oral ecosystems. So, even though most oral fungi and bacteria are not cultivable, in vitro microbiological models should still be instrumental in adapting oral care products, dietary products and care protocols to patients at higher risk of oral diseases. Microbial biofilm models combined with oral epithelial cell cultures could also aid in understanding the inflammatory reaction.
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7.
Biofilms and their properties.
Valen, H, Scheie, AA
European journal of oral sciences. 2018;:13-18
Abstract
Bacteria within the oral cavity live primarily as complex, polymicrobial biofilms. Dental biofilms are necessary etiological factors for dental caries and periodontal diseases but have also been implicated in diseases outside the oral cavity. Biofilm is the preferred lifestyle for bacteria, and biofilms are found on almost any surface in nature. Bacteria growing within a biofilm exhibit an altered phenotype. Substantial changes in gene expression occur when bacteria are in close proximity or physical contact with one another or with the host. This may facilitate nutritional co-operation, cell-cell signaling, and gene transfer, including transfer of antibiotic-resistance genes, thus rendering biofilm bacteria with properties other than those found in free-floating, planktonic bacteria. We will discuss biofilm properties and possible consequences for future prophylaxis.
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Oral lichen planus - Differential diagnoses, serum autoantibodies, hematinic deficiencies, and management.
Chiang, CP, Yu-Fong Chang, J, Wang, YP, Wu, YH, Lu, SY, Sun, A
Journal of the Formosan Medical Association = Taiwan yi zhi. 2018;(9):756-765
Abstract
Oral lichen planus (OLP) is a chronic inflammatory oral mucosal disease that occurs more frequently in middle-aged and elderly female patients. Previous studies indicate that OLP is a T-cell dysfunction-induced localized autoimmune disease. Clinically, six types of OLP, namely reticular, papular, plaque-like, atrophic/erosive, ulcerative, and bullous types, can be identified. OLP more commonly affects buccal mucosa, tongue, and gingiva. It always has a bilateral and symmetric distribution of the oral lesions. Plaque-like and atrophic/erosive OLP may be misdiagnosed as oral leukoplakia and oral erythroleukoplakia, respectively. Our previous study found serum autoantibodies in 195 (60.9%) of the 320 OLP patients. Specific serum anti-nuclear, anti-smooth muscle, anti-mitochondrial, gastric parietal cell, thyroglobulin, and thyroid microsomal autoantibodies are present in 28.1%, 8.4%, 1.6%, 26.3%, 21.3%, and 24.4% of 320 OLP patients, respectively. Furthermore, we also discovered that 21.9%, 13.6%, 7.1%, 0.3%, and 14.8% of 352 OLP patients have hemoglobin, iron, vitamin B12, and folic acid deficiencies, and abnormally high serum homocysteine level, respectively. Therefore, it is very important to examine the serum autoantibody, hematinic and homocysteine levels in OLP patients before starting the treatments for OLP patients. Because OLP is an immunologically-mediated disease, corticosteroids are the drugs of choice for treatment of OLP.
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9.
The Caries Microbiome: Implications for Reversing Dysbiosis.
Tanner, ACR, Kressirer, CA, Rothmiller, S, Johansson, I, Chalmers, NI
Advances in dental research. 2018;(1):78-85
Abstract
The oral microbiome plays a critical role in maintaining oral health. Frequent dietary carbohydrate intake can lead to dysbiosis of the microbial community from overproduction of acid with selection for increases in acidogenic, acid-tolerant bacteria. Knowledge of the caries-associated microbiome is key in planning approaches to reverse the dysbiosis to achieve health. For risk assessment and treatment studies, it would be valuable to establish whether microbial monitoring requires assay of multiple species or whether selected key species would suffice. Early investigations of the oral microbiota relied on culture-based methods to determine the major bacteria in health and disease. Microbial monitoring using gene probes facilitated study of larger populations. DNA probe methods confirmed and expanded the importance of transmission of bacteria from mother to infant and association of preselected species, including mutans streptococci and lactobacilli with caries in larger populations. 16S ribosomal RNA (rRNA) probes confirmed the wide diversity of species in oral and caries microbiomes. Open-ended techniques provide tools for discovery of new species, particularly when strain/clone identification includes gene sequence data. Anaerobic culture highlighted the caries association of Actinomyces and related species. Scardovia wiggsiae, in the Actinomyces/Bifidobacterium family, and several Actinomyces species have the cariogenic traits of acid production and acid tolerance. Next-generation sequencing combined with polymerase chain reaction methods revealed a strong association with mutans streptococci in a high caries population with poor oral hygiene and limited access to care. A population with a lower caries experience generally had lower or no Streptococcus mutans detection but harbored other acidogenic taxa in the microbiome. Study of the microbiome suggests a role for the assay of selected putative cariogenic species in more aggressive diseases. For many populations with caries progression, however, assay of multiple species will likely be warranted to determine the caries profile of the population and/or individuals under study.
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10.
The oral microbiome - friend or foe?
Kilian, M
European journal of oral sciences. 2018;:5-12
Abstract
The microbiome and the human body constitute an integrated superorganism, which is the result of millions of years of coevolution with mutual adaptation and functional integration, and confers significant benefits for both parties. This evolutionary process has resulted in a highly diverse oral microbiome, which covers the full spectrum of acidogenic, aciduric, inflammatory, and anti-inflammatory properties. The relative proportions of members of the microbiome are affected by factors associated with modern life, such as general diet patterns, sugar consumption, tobacco smoking, oral hygiene, use of antibiotics and other antimicrobials, and vaccines. A perturbed balance in the oral microbiome may result in caries, periodontal disease, or candidiasis, and oral bacteria passively transferred to normally sterile parts of the body may cause extra-oral infections. Nevertheless, it should never be our goal to eliminate the oral microbiome, but rather we have to develop ways to re-establish a harmonious coexistence that is lost because of the modern lifestyle. With regard to oral diseases, this goal can normally be achieved by optimal oral hygiene, exposure to fluoride, reduction of sucrose consumption, stimulation of our innate immune defense, smoking cessation, and control of diabetes.