Role of Microbial Biofilms in the Maintenance of Oral Health and In

J Clin Periodontol 2017; 44 (Suppl.18): S5–S11 doi: 10.1111/jcpe.12682

Mariano Sanz1,*, David Beighton2, Role of microbial biofilms in the Michael A. Curtis3, Jaime A. Cury4, Irene Dige5, Henrik Dommisch6, Roger Ellwood7, Rodrigo Giacaman8, maintenance of oral health and David Herrera1, Mark C. Herzberg9, Eija Kon€ onen€ 10, Philip D. Marsh11, Joerg Meyle12, Alex Mira13, Ana in the development of dental Molina1, Andrea Mombelli14, Marc Quirynen15, Eric C. Reynolds16, Lior Shapira17 and Egija Zaura18 caries and periodontal diseases. 1ETEP (Etiolgy and Therapy of Periodontal Diseases) Research Group, University Complutense, Madrid, Spain; 2King’s College Consensus report of group 1 of London School of Medical Education, London, UK; 3Microbiology, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, the Joint EFP/ORCA workshop UK; 4Piracicaba Dental School, UNICAM, Piracicaba, SP, Brazil; 5Department of Dentistry and Oral Health, Faculty of Health, on the boundaries between Aarhus Universitet, Aarhus C, Denmark; 6Charite, Berlin, Germany; 7Manchester University, Manchester, UK; 8Oral Rehabilitation, University of Talca, Talca, caries and periodontal disease Chile; 9University of Minnesota School of Dentistry, Minneapolis, MN, USA; 10Periodontology, University of Turku, Turku, Finland; 11Department of Oral Biology, Sanz M, Beighton D, Curtis MA, Cury J, Dige I, Dommisch H, Ellwood R, School of Dentistry, University of Leeds, € € Giacaman R, Herrera D, Herzberg MC, Kononen E, Marsh PD, Meyle J, Mira Leeds, UK; 12Periodontology, University of A, Molina A, Mombelli A, Quirynen M, Reynolds E, Shapira L, Zaura E. Role of Giessen, Giessen, Germany; 13Centre for microbial biofilms in the maintenance of oral health and in the development of Advanced Research in Public Health, dental caries and periodontal diseases. Consensus report of group 1 of the Joint FISABIO Foundation, Valencia, Spain; 14 EFP/ORCA workshop on the boundaries between caries and periodontal disease. J Periodontology, University of Geneva, 15 Clin Periodontol 2017; 44 (Suppl. 18): S5–S11. doi: 10.1111/jcpe.12682. Geneva, Switzerland; Katholieke Universiteit Leuven, Leuven, Belgium; 16Oral Abstract Health Cooperative Research Centre, Melbourne Dental School, The University of Background and Aims: The scope of this working group was to review (1) ecolog- Melbourne, Melbourne, Australia; ical interactions at the dental biofilm in health and disease, (2) the role of micro- 17Periodontology, Hebrew University and bial communities in the pathogenesis of periodontitis and caries, and (3) the Hadassah Medical Center, Jerusalem, Israel; innate host response in caries and periodontal diseases. 18Department of Preventive Dentistry, Results and Conclusions: A health-associated biofilm includes genera such as Academic Centre for Dentistry Amsterdam Neisseria, Streptococcus, Actinomyces, Veillonella and Granulicatella. Microorgan- (ACTA), Amsterdam, The Netherlands isms associated with both caries and periodontal diseases are metabolically highly specialized and organized as multispecies microbial biofilms. Progression of these Key words: caries; dental biofilm; dysbiosis; diseases involves multiple microbial interactions driven by different stressors. In innate host responses; microbial interactions; caries, the exposure of dental biofilms to dietary sugars and their fermentation to periodontal diseases; symbiosis organic acids results in increasing proportions of acidogenic and aciduric species. Accepted for publication 20 December 2016

Conflict of interest and source of funding statement Workshop participants filed detailed disclosures of potential conflict of interest relevant to the workshop topics, and these are kept on file. Declared potential dual commitments included having received research funding, consultant fees and speakers fee from Colgate Palmolive, Procter & Gamble, Johnson & Johnson, Sunstar, Unilever, Philips, Dentaid, Ivoclar-Vivadent, Heraeus-Kulzer. Funding for this workshop was provided by the European Federation of Periodontology in part through unrestricted educa- tional grants from Colgate Palmolive.

In gingivitis, plaque accumulation at the gingival margin leads to inﬂammation and increasing proportions of proteolytic and often obligately anaerobic species. The natural mucosal barriers and saliva are the main innate defence mechanisms against soft tissue bacterial invasion. Similarly, enamel and dentin are important hard tissue barriers to the caries process. Given that the present state of knowledge suggests that the aetiologies of caries and periodontal diseases are mutually independent, the elements of innate immunity that appear to contribute to resistance to both are somewhat coincidental.

Oral biofilms are present on all site-to-site than previously appreci- of the microorganisms in the bio- intra-oral surfaces. Biofilm composi- ated. The potential interactions film are generally different from tion varies between healthy sites and between individual species, between those in planktonic state. Plaque between different between healthy the biofilm, the environment, and on a tooth surface is a classical and diseased sites. Dental caries and the host have been mainly studied example of a biofilm and is ter- periodontal diseases are among the using in vitro model systems. med: dental biofilm. Microorgan- most prevalent diseases of mankind. Whereas these models cannot com- isms function in dental biofilms These oral diseases have a negative pletely mimic the host environment, as interactive microbial commu- impact on quality of life, and dental they do provide a basis to raise and nities. Biofilms also exist on other test mechanistic hypotheses of surfaces in the mouth and can caries and periodontitis are the main – – causes of tooth loss. The biofilm is microbe microbe and microbe host shed into the fluid phase (saliva, required for the development of interactions contributing to oral gingival crevicular fluid). these oral diseases. The microbial health and disease. • Microbial Interactions: microor- composition of the dental biofilm To better understand the role of ganisms in biofilms are in physi- has been extensively studied using microbial biofilms in the mainte- cal proximity, which facilitates a cultural methods, which limit the nance of oral health and the devel- range of interactions, which may identification and cultivation of all opment of dental caries and be synergistic or antagonistic. microorganisms in the environment. periodontal diseases, the following • Symbiosis is a mutually beneficial Current approaches, however, use working terms have been applied: relationship among members of genome sequencing to identify and • Biofilm: microorganisms attached the microbial community and quantify the microorganisms in den- to a surface embedded in an between the microbial communi- tal biofilms, which is now known to extracellular matrix in contact ties and the host, with varying be more complex and variable from with a fluid phase. The properties degrees of benefit. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Microbioal biofilms in dental caries and periodontal diseases S7

• Dysbiosis is a change in the of oral microorganisms but with the biofilm is characterized by prote- microbial communities associated minimal changes in environmental olytic and often obligately anaerobic with health, resulting in a break- pH. In the presence of a stable pH, species. Inter-microbial interactions down of the beneficial relation- microbial species that grow opti- are necessary for the concerted and – ship with the host, which is mally in the pH range 6.5 7.5 (neu- sequential catabolism of host pro- deleterious to health. trophilic microorganisms) results in teins and glycoproteins for nutri- • Host defence includes host biofilm homoeostasis and generation tional purposes. These interactions responses and physical barriers. of a range of nutritional inter-depen- are also essential for growth factors • Physical barriers, such as enamel dencies among the bacteria. required by fastidious microorgan- and epithelium, together with Dental biofilms develop as func- isms present in these biofilms; exam- oral fluids, protect the underlying tionally and structurally organized ples include the release of haemin tissues from microbial insults. communities of interacting microor- from haemoglobin, and the sharing • Host response is an active process ganisms. These interactions can be of siderophores. Complex food webs that includes innate and adaptive synergistic or antagonistic and pro- develop, whereby the products of immunity, which commonly duce a biofilm that prevents colo- one organism are further degraded arises from a microbial challenge. nization by non-oral microorganisms by neighbouring species, and organ- • Innate host response (versus adap- and provides protection to the dental isms scavenge oxygen creating highly tative immunity) is a protective surfaces. A health-associated biofilm reduced environments suitable for mechanism against microbial is associated with an active balance obligately anaerobic organisms. challenge that is immediate and between slow rates of acid produc- To facilitate survival or persis- of limited specificity. tion and compensatory alkali genera- tence, some microorganisms subvert • Adaptive host response is an tion, resulting in an environment the host defences through the release acquired response to a specific with a broadly neutral pH. Such of certain molecules, such as pro- microbial challenge. conditions help to stabilize the com- teinases, leukotoxins, modified • Functional fluids are fluids pro- position of health-associated species lipopolysaccharides (LPS). Some of duced by the body that carry while restricting the growth of these microorganisms are not only innate and adaptive immune microorganisms associated with car- capable of enduring the host response, mediators. ies and periodontal diseases. but have adapted to exploit the Microbes in a health-associated bio- altered environmental conditions, and This consensus report will pro- film can produce substances includ- are termed inflammophiles “inflam- vide a foundation for designing stud- ing H2O2 and bacteriocins that may mophiles” (Hajishengallis, 2014). ies to elucidate the actual suppress the growth of microorgan- Microorganisms associated with interactions between the biofilm and isms associated with disease. both caries and periodontal diseases the host with the potential to design In addition to saliva, dietary sug- are metabolically highly specialized novel strategies to improve oral ars are a major source of nutrients. and organized as multispecies micro- health. Among them, sucrose has unique bial biofilms. Progression of dental properties. It is considered the most caries and periodontal diseases cariogenic dietary carbohydrate, involves positive feedback loops, but Dental Biofilm: Ecological because fermented to acids by the are driven by different stressors. In Interactions in Health and Disease bacteria biofilm, but also because it caries, the frequent exposure to diet- Multispecies biofilms form naturally can be metabolized to intracellular ary sugars (carbohydrates) and fer- on all oral surfaces. The proximity and extracellular polysaccharides mentation to organic acids can result of microorganisms within these bio- (IPS and EPS). In the presence of in a positive feedback loop resulting films creates opportunities for species dietary sugars, the biofilm is charac- in ever increasing proportions of aci- to interact. Many types of inter- terized by saccharolytic, acidogenic dogenic and aciduric species which microbial interactions have been and aciduric species, that also syn- enhances the acidity of the environ- described, but it should be noted thesize extracellular polysaccharides ment. In gingivitis, plaque accumula- that most of these interactions have that contribute to the biofilm matrix. tion at the gingival margin leads to been investigated in laboratory sys- The saccharolytic and acidogenic inflammation and a positive feed- tems, and occasionally animal mod- microorganisms generate a low pH back loop resulting in ever increasing els, and therefore, some caution from the fermentation of dietary proportions of inflammophiles. Some should be exercised when extrapolat- sugars, which inhibits “neutrophilic highly specialized members of the ing these findings to events in microorganisms” associated with community can subvert and dysregu- humans (Marsh & Zaura 2017). enamel health. In the absence of late the host immune response, Saliva is the primary source of dietary sugars, a caries-associated which may result in destruction of nutrients for health-associated bio- biofilm can generate acids from the periodontal tissues in susceptible films. The metabolism of host glyco- metabolism of extracellular glucans individuals. proteins and proteins by the oral and fructans, and intracellular stor- Biofilms associated with caries microbiota requires microbial coop- age compounds. and periodontal diseases display eration and the sharing of a broad Gingival crevicular fluid (GCF) is emergent properties; that is, the repertoire of glycosidases and pro- a main source of nutrients for properties of the community are teases. The catabolism of these sali- microorganisms in biofilms associ- more than the sum of the individual vary molecules facilitates the growth ated with periodontal diseases, and species. For example, most oral © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd S8 Sanz et al. bacteria can grow only poorly or not (Mira et al. 2017). However, at pre- a wider range of organisms in a at all in pure culture on glycoproteins sent, it is not possible to define a dynamic and potentially interactive in saliva or GCF, but can thrive when “core” microbiome or specific com- community structure. These include metabolizing these complex host munity structures associated with Bifidobacterium dentium (Mant- molecules as part of a microbial com- health because of the following: zourani et al. 2009) and Scardovia munity. Microorganisms that persist • dental biofilms in healthy individ- wiggsiae, the latter associated with in dentin caries and periodontal dis- uals vary substantially within and Early Childhood Caries (Tanner eases require the cooperative degra- between individuals and may et al. 2011). DNA from other bacte- dation of complex host molecules reflect differing susceptibility to ria such as Schlegelella or Pseudo- (proteins and glycoproteins) as nutri- ramibacter appears to be present in disease; tional and energy sources. • during the course of life from dentin caries lesions (Simon-Soro & Many of these interactions have birth through old age, commu- Mira 2015), but the lack of experi- been defined in vitro, using simple nity variations change, reflecting mental studies on these organisms combination(s) of species. Addition- ageing oral anatomy, ecology has precluded evaluation of their ally, the majority of the interactions and immune function; and cariogenic potential. studied involve bacteria only, ignor- • most studies to date using the In periodontal diseases, the com- ing other segments of the oral micro- new technologies have been per- munity structure is historically biota (fungi, Archaea, viruses, formed on relatively few individ- viewed as associated largely with protozoa). Current technological uals and few sites. Gram-negative proteolytic anaerobic advances enable the study of more species. A limited number of species complex community level interac- Nevertheless, there is an emerging were considered to be major patho- tions (Edlund et al. 2015), including consensus that several genera are nor- gens, including: Porphyromonas gin- those among members of the micro- mally associated with health, includ- givalis, Treponema denticola, biota from different kingdoms (Diaz ing Neisseria, Streptococcus, Tannerella forsythia and Aggregati- et al. 2016). Rather than just cata- Actinomyces, Veillonella and Granuli- bacter actinomycetemcomitans. Using loguing which microorganisms are catella. Understanding the role of more recent technologies, the micro- present, attention needs to be these health-associated organisms bial community structure in peri- focussed on what they are doing may have utility in the application of odontal diseases appears to undergo within these microbial communities pre- and probiotic approaches for the major alterations. Dysbiosis is recog- (Takahashi 2015). prevention and treatment of disease. nized as follows: the loss or reduction In the future, a more complete Given high inter-individual vari- in potentially beneficial organisms, understanding of the microbial “in- ability in bacterial composition in increased proportions of species in teractome” (Jenkinson 2011) could health, functional properties of bac- health, and emergence of many facilitate discovery of novel ecologi- terial communities should be a con- organisms that were undetected using cal preventive and therapeutic ceptual focus rather than taxonomic previous technologies. Unlike caries, approaches. Such approaches could composition. Indeed, whole-DNA dysbiosis in periodontal diseases is be applied to disease control by pro- sequencing studies show that differ- associated with an increase in micro- moting health-associated communi- ent healthy individuals may harbour bial diversity, which could be the ties through nutritional or extremely variable bacterial commu- result of impaired local immune func- therapeutic strategies, and interfering nities but their gene content and tion, increased availability of nutri- with the interactions associated with functional capability are remarkably ents or a reflection of the diverse disease. similar (Human Microbiome Project environmental niches at the sampling Consortium 2012). site at the periodontal pocket Role of Microbial Communities in the As the microbial composition (Dewhirst et al. 2010, Camelo-Cas- Pathogenesis of Periodontitis and shifts from health to caries, the com- tillo et al. 2015). This view does not Caries munity structure varies substantially preclude the possibility of occasional instances of periodontitis caused by a Until recently, the microbial commu- from site-to-site and between indi- more restricted spectrum of organ- nity structure of healthy dental bio- viduals and with developing disease. isms as evidenced by the specific role films was based on cultural Nevertheless, there are some unifying of the JP2 clone of A. actino- microbiology, DNA:DNA hybridiza- characteristics of caries-associated mycetemcomitans in cases of aggres- tion and polymerase chain reaction biofilms. Overall microbial diversity sive periodontitis in individuals of (PCR) investigations. From these appears to be lower in disease than West African descent (Haubek et al. studies, the microbial community health, which may reflect the ecologi- 2008). In general, the functional char- was suggested to be of relatively low cal pressure of lowered environmen- acteristics of microbial communities diversity dominated by Gram-posi- tal pH. Characteristic features of in periodontal diseases include the tive organisms including species these organisms include acidogenic- ability to withstand/deregulate the belonging to the genera Streptococ- ity, acid tolerance and the formation immune and inflammatory response, cus and Actinomyces. More recent of extracellular polysaccharides from to prevail in an anaerobic environ- studies using alternative high dietary sucrose. In addition to the ment and to take advantage to the throughput non-cultural approaches classically recognized organisms such altered nutritional availability of suggest the diversity in health is as the mutans streptococci and lacto- potential substrates in gingival crevic- higher than previously thought bacilli, more recent studies implicate ular fluid flow and blood. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Microbioal biofilms in dental caries and periodontal diseases S9

The microbial communities asso- methods for integration of large data epithelial duct cells, neutrophils and ciated with periodontal health and sets will allow a holistic overview of fibroblasts provide protection for caries-free dentition are in symbiosis these diseases which combines the periodontal and enamel health with the host. Maintenance of this contribution of not only microbial (Meyle et al. 2017). In addition, symbiotic state will be dependent populations but also the host and the antimicrobial peptide-rich neu- upon on factors/processes derived environment. Such a holistic over- trophils are found in both saliva and from both bacteria (for example view may allow the translation of the gingival crevicular fluid (Gorr & nutritional interdependencies multifactorial aetiology of these oral Abdolhosseini 2011, Dommisch & between different bacteria) and from diseases into integrated diagnostic Jepsen 2015). Bioactive lipids, such the host (for example salivary glyco- and therapeutic approaches. as resolvins, may be protective medi- proteins which provide a continuous With regard to the functional ators in periodontal health (Hasturk supply of nutrients to the dental bio- roles of microbial populations in & Kantarci 2015). Mucins and films). That the microbial commu- dental biofilms, the development and agglutinins in saliva and pre-existing nity requires these factors and application of the following methods specific antibodies (IgG) in GCF processes would appear to stabilize will be important: contribute to the clearance of the symbiotic state with the host and • advanced imaging at the micro- microbes. Other antimicrobial fac- the maintenance of health. scopic and submicroscopic level tors such as activated complement Stressors applied to the symbiotic to elucidate, for example, com- also function in GCF. state can perturb homoeostasis and munity structures and cell–cell The dental biofilm may be lead to dysbiosis wherein the health- communication in both model affected by the relative abundance associated microbial populations are and natural biofilms; and composition of proteins in the significantly altered and consistent • analysis of gene expression at the salivary pellicle or film coating the with the development of disease microbial community level in teeth, which could protect against (Mira et al. 2017). In dental caries both symbiotic and dysbiotic caries. The salivary pellicle also con- will include dietary sugars and conditions; and tains calcium-binding proteins such reduced salivary flow or altered sali- • application of microbiological as statherin, which can make the pel- vary composition. Stressors in the endpoints into randomized clini- licle supersaturated with calcium and case of periodontal diseases may cal trials. phosphate salts in hydroxyapatite. include alterations to the effective- The pellicle can, therefore, con- ness of the immune response (for The historical paradigm that both tribute to maintaining mineralization example impaired function or caries and periodontal diseases were of the enamel surface and aid in reduced numbers of neutrophils) and a consequence of only a limited resistance to demineralization. In the activities of keystone bacterial repertoire of microorganisms led to response to chewing and the sensory species (for example P. gingivalis) diagnostic, preventive and therapeu- quality of foods (gustatory stimula- able to manipulate the overall bacte- tic strategies with targeted specificity. tion), the salivary flow rate increases. rial population structure. The dysbi- Based on our more recent under- The stimulated saliva has increased otic state may also resist reversion to standing that both groups of diseases buffering capacity and altered com- symbiosis dependent upon factors are associated with complex and position. The shear forces from derived from both bacteria and the variable communities in a dysbiotic increased flow tend to reduce adhe- host. Understanding the factors and state, future approaches should rec- sion of microbes and microbial com- process that are required to maintain ognize this multifactorial and vari- plexes to the tooth surface. The symbiotic and dysbiotic states and able microbial aetiology and the protein composition of stimulated the stressors that drive one state into potential functional importance of saliva can inhibit microbial growth, another could inform new develop- microbial populations in dysbiosis whereas the ionic content reduces ment of preventive and therapeutic with their host. The ultimate chal- enamel solubility. Collectively these strategies in caries and periodontal lenge will be to translate this new mechanisms provide protection diseases. knowledge into novel, practical against caries. To reliably characterize the exten- approaches for prevention, diagnosis Enamel and dentin are important sive within and between individual and therapy of caries and periodon- hard tissue barriers to the caries pro- variations in the microbial communi- tal diseases to the benefit of human cess. Fluoride interferes with the car- ties in dental biofilms in both health populations. ious process by reducing and disease, studies with larger popu- demineralization and enhancing rem- lation sizes and more refined sam- The Innate Host Response in Caries ineralization. Certain developmental pling methods are necessary. To and Periodontal Diseases defects of enamel result in break- elucidate the dimensional and down of the barrier and may changeable presentation of these dis- The oral mucosa, salivary environ- increase the risk of carious lesions. eases, longitudinal investigations will ment, transmigrating polymorphonu- The prevalence of root caries be required on a range of different clear leucocytes (PMNs) and gingival increases in the presence of gingival populations. Functional analysis of crevicular fluid form the first lines of recession, suggesting that intact junc- microbial populations may prove to defence against the microbial chal- tional epithelium and proximal gin- be a more valuable approach than lenge arising from the dental biofilm. giva are protective. During the caries taxonomic analysis. The application Antimicrobial peptides and proteins process, odontoblasts proximal to of -omics technologies coupled with derived from epithelial cells, salivary dentinal tubules may stimulate intra- © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd S10 Sanz et al. tubular mineralization resulting in function of PMNs typically increase reduced removing an impediment to closure (Garces-Ortiz et al. 2013) the risk of periodontitis. For exam- PMN infiltration of the gingiva. and reduced diffusion of intra-tubu- ple, periodontitis is a prominent Commensal bacteria and putative lar fluid. In response, the dental pulp comorbidity of leucocyte adhesion pathogens engage TLRs and other releases soluble proinflammatory deficiency syndrome and chronic pathogen-related receptors (PRRs) mediators. For example, pulpal cells granulomatous disease. to signal for upregulation of key release interleukin-1b and defensins. During periodontitis, the PMN cytokines and antimicrobial peptides. The defensin hBD-2 and IL-1b stim- response tends to reduce proportion- For example, bacterial lipopolysac- ulate the expression of other media- ally to other cells. Periodontitis is charide (LPS) is bound to LPS-bind- tors including dentin also characterized by activation of ing protein (CD14) and selects TLRs sialophosphoprotein, contributing to Langerhans dendritic cells and on neutrophils, monocytes, macro- dentin repair. intraepithelial lymphocytes such as phages and mast cells. Engagement The incidence of gingivitis cd-T cells. These innate immune cells of LPS activates these leucocytes, increases in proximity to cervical capture and present bacterial anti- which reside in the subgingival con- carious lesions. At these sites, the gens to CD4 and CD8 T cells of the nective tissue. The antimicrobial pep- soft tissue inflammation may be pro- adaptive immune system. Activated tide LL-37 may antagonize the moted because dental plaque accu- cd-T cells produce IL-17, which is action of LPS. mulates. During inflammation, the mechanistically associated with peri- Antimicrobial peptides can also integrity of the epithelial barrier pre- odontal bone loss in periodontitis. serve as danger-associated molecular vents bacterial penetration. Inflam- The expression of antimicrobial pep- patterns (DAMPs), which activate mation stimulates turnover of tides also differs in gingival tissues inflammasomes of the epithelial cells gingival and junctional epithelial from gingivitis and periodontitis and PMNs. A major product of the cells. As the superficial epithelial patients. In patients with periodonti- inflammasome, superoxides are toxic cells are shed into the salivary envi- tis, hBD-1 levels are higher than in to both microbes and host tissues. ronment and swallowed, adherent gingivitis. Levels of hBD-2 and While antagonizing the growth of and intracellular bacteria are effec- hBD-3 appear similar in both infec- bacteria, superoxides cause local tis- tively disposed. The self-renewing tions. sue damage and micro-abscess for- quality of squamous epithelia is a Innate immunity during the caries mation. valuable protective mechanism process includes salivary and to a Prostaglandin E2 and related against infection. lesser extent soluble mediators in lipid mediators can activate immune Gingival epithelial cells also pro- GCF. The salivary factors work at cells and stimulate proinflammatory duce soluble proinflammatory medi- the enamel surface to increase sur- and pro-coagulant responses. In con- ators – cytokines – in response to face mineralization and minimize trast, tissue destruction during oral microbes. For example, Gram- bacterial adhesion and growth. inflammation in periodontitis positive and Gram-negative bacterial Within the pulp, stimulated odonto- appears to be somewhat reversible. pathogen-associated molecular pat- blasts also function in innate repara- Tissue damage appears to be terns engage Toll-like receptors tive mechanisms promoting reversed by resolving lipids such as (TLR) to signal to regulate IL-1a, mineralization from within the the resolvins and maresins. IL-6 and IL-8. TLR signalling and tooth. Complement proteins in GCF other signalling pathways work to The antimicrobial role of PMNs percolate through the junctional increase innate antimicrobial resis- in gingivitis tends to be replaced in epithelium into the gingival sulcus. tance of the epithelium. For exam- periodontitis by Langerhans den- Rapidly activated by oral microbes, ple, in response to the pathogenic dritic cells and cd-T cells. Upon complement peptides elicit an inflam- bacteria, epithelial cells release IL-1a stimulation, these cells increase pro- matory response. For example, C3b to stimulate epithelial cells via an duction of proinflammatory cytoki- acts as an opsonin, facilitating autocrine loop, upregulating the nes including IL-1, IL-6, IL-8, IL-17, phagocytosis and intracellular killing expression of antimicrobial peptides, TNF-a and IL-23. The Langerhans of microbes by neutrophils. including hBDs, calprotectin and cells and cd-T cells bridge the innate The present state of knowledge cathelicidin. and adaptive immune responses. suggests that the aetiologies of caries Bacterial chemoattractants and Invading bacteria and their prod- and periodontal diseases are mutu- activated complement components ucts can activate proximal capillary ally independent. Nonetheless, ele- stimulate activation and emigration endothelial cells to increase expres- ments of innate immunity appear of PMNs through the junctional sion of ICAM-1 and selectin recep- common to both types of infections. epithelium into the GCF. As phago- tors (Hajishengallis et al. 2016). Current understanding indicates that cytes are storehouses of antimicro- Concomitantly, capillaries allow exu- similarities in innate immunity to bial proteins, PMNs represent a dation and leucocyte transmigration, caries and periodontal diseases are major innate cellular response. facilitating the presence of leucocytes coincidental. Longitudinal prospec- PMNs are prominent during gingivi- in the tissues. The activated endothe- tive studies are required to obtain tis and early periodontitis. A pre- lial cells also express Del-1, which data to identify cellular and/or sol- ponderance of PMNs also appears blocks leucocyte adhesion to LFA-1 uble mediators of innate immunity during acute exacerbations of peri- receptors and inhibits diapedesis. In that might serve as biomarkers of odontitis. Diseases affecting normal periodontitis, Del-1 production is disease or therapeutic targets.

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Clinical Relevance the development of caries and peri- health and the initiation and pro- Scientific rationale for study: Caries odontal diseases, and hence, knowl- gression of dental caries and peri- and periodontal diseases are among edge of the composition and inter- odontal diseases is key to improve the most prevalent diseases of man- microbial interactions is fundamental preventive strategies and to design kind. Both have a negative impact for developing effective preventive novel strategies to improve oral on quality of life and the main and therapeutic measures. health. cause of tooth loss. Practical implications The knowledge Principal findings: The biofilm is an of the microbe-host interactions essential component involved in involved in the maintenance of oral