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Dental plaque (bacteria biofilm ) - g enesis and structure .

Microbiology of dental plaque - differences between immature and mature plaque. Microbial metabolism and plaque biofilm pathogenic potential. Dental plaque (bacteria biofilm ) - g enesis and structure . Prof. d-r Kabaktchieva - 2014y.

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Dental plaque (bacteria biofilm ) - g enesis and structure .

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  1. Microbiology of dental plaque - differences between immature and mature plaque.Microbial metabolism and plaque biofilm pathogenic potential. Dental plaque (bacteria biofilm) - genesis and structure. Prof. d-r Kabaktchieva - 2014y.

  2. Thedental professional comesintocontactwithtwoofthemostwidespreadofallhumandiseases - dentalcariesandperiodontaldiseases

  3. gingivitis caries caries Unliketypicalinfectiousdiseases, dentalcariesandperiodontaldiseasesarenotcausedby a singlepathogenicmicroorganism.

  4. DentalcariesandperiodontaldiseasesresultfromtheaccumulationofmanydifferentspeciesofbacteriathatformDentalcariesandperiodontaldiseasesresultfromtheaccumulationofmanydifferentspeciesofbacteriathatform • dentalplaque a naturallyacquiredbacterialbiofilmthatdevelopsontheteeth

  5. Dentalplaqueis a multi-speciesbiofilm, Somebacterialspeciesmaybeofgreaterrelevanceinthedevelopmentofcariesandperiodontaldiseases. Dental plaque

  6. Tounderstandtheroleofdentalplaqueincaries • mustfirstknowhowdentalplaqueforms ? • howchangesintheproportionsofdifferentplaquebacteria cancontributetothedevelopmentof this oraldisease?

  7. DentalPlaque: A MicrobialBiofilm • Mostnaturalsurfaceshavetheirowncoatingofmicroorganisms, orbiofilm, adaptedtotheirindividualhabitats.

  8. Bacterialadhesiontosurfacesprimarilyinvolvestwotypesofreactions: physicochemicalandbiochemical. Thesesameinteractionsoccurintheformationofplaqueandcalculusonoralstructures.

  9. Alllivingcellsinnature, includingbacterialplaquecells, have a net-negativesurfacecharge. • Thecellscan, therefore, beattractedtooppositelychargedsurfacesasskin. inthecaseofbacterialplaque, have attracting between thesurfacesofcells ,teeth, andsofttissuesoftheoralcavity.

  10. Themicroorganismswithinbacterialplaquecanproduce : • extracellularcoatings, suchas slimelayerswhich prolongtheexistenceof biofilms ; • a varietyofsurfacefibrils, orappendages, thatextendfromtheircellwalls. • Thesemechanismsmediateattachmentofbacteriato a substratebyprovidingadditionalattachmentstructuresbetweenthetoothsurfaceandtheplaque, thusallowingtheformationofadherentmatrices.

  11. BacterialColonizationoftheMouth • Microorganismsfoundintheoralcavityarenaturallyacquiredfromtheenvironment. • Bacteriaareacquiredfromtheatmosphere, food, humancontact. • Bacteriaformcoloniesbetweensalivaandhardtissuessuchaseruptedteeth, andexposedrootcementumanddentin.

  12. Priortoeruption, theexternalsurfaceof toothenamelislinedbyremnantsofthe enamel-formingorgan. • Thesetissueremnantsare: - thereducedenamelepitheliumand - thebasallamina

  13. Thebasallaminaconnectstheepitheliumtotheenamelsurface. • Thebasallaminaisalsocontinuouswithorganicmaterialthatfillsthemicroscopicvoidsinthesuperficialenamel. • Thissubsurfaceorganicmaterialappearsas a fringe-likestructureattachedtothebasallaminaandiscomposedofresidualenamelmatrixproteins. Thismaterialisreferredtoas a subsurfacepellicle. Thepellicleoriginatesfromlocalcellsduringtoothformation; therefore, itisconsideredtobeofendogenousorigin.

  14. SSP B AP ES • The transmissionelectronmicrographdemonstrates: • remnantsofthesubsurfacepellicle (SSP) • theacquiredpellicle (AP) • They are betweentheenamelsurface (ES) and • thebacterialcells (B) ofthedentalplaque.

  15. RA HD EM ES BL Figure .Junctionofreducedenamelepitheliumandenamel. Thereducedameloblasts (RA) areattachedtotheenamelbyhemidesmosomes (HD) and a basallamina (BL). EM, enamelmatrixremnantsform a subsurfacepellicle; ES, enamelspace.

  16. Whenthetoothemergesintotheoralcavity, theremnantsofthereducedenamelepitheliumare: - wornoff - digestedbysalivaryandbacterialenzymes

  17. Aneruptedtoothimmediatelybecomescoveredby a thin, microscopiccoatingofsalivamaterials. • Thesalivarycomponentsbecomeadsorbedtothesurfaceoftheenamelwithinseconds. Thiscoatingisalsoreferredtoas a pellicle.

  18. Becausethepellicleisacquiredaftereruptionofteeth, itissaidtohaveanexogenousorigin thepelliclewasformedby a substancefromoutsidethetooth, ratherthanduringthedevelopmentofteeth.

  19. Theoralbacteriacanformcoloniesintheacquiredpellicle.

  20. TheAcquiredPellicle Thecoatingofsalivaryoriginthatformsonexposedtoothsurfacesiscalledtheacquiredpellicle. Itisacellularandconsistsprimarilyofglycoproteinsderivedfromsaliva B АР ЕS

  21. A glycoproteinis a proteinmoleculethatincludesanattachedcarbohydratecomponent.

  22. Oralfluidsandsmallmoleculescanslowlydiffusethroughtheacquiredpellicleintothesuperficialenamel;Oralfluidsandsmallmoleculescanslowlydiffusethroughtheacquiredpellicleintothesuperficialenamel; • Ifthepellicleisdisplaced, (by a prophylaxis), thepelliclebeginstoreformimmediately; • Ittakesabout a weekforthepellicletodevelopitscondensed, maturestructure, whichmayalsoincorporatebacterialproducts.

  23. Colonizationoftheacquiredpelliclecanbebeneficialforthebacteria, becausethepelliclecomponentscanserveasnutrients. • Forexample: proline-richsalivaryproteinsmaybedegradedbybacterialcollagenases. Thisactionreleases peptides, freeaminoacids, + salivarymucinsmayenhancethegrowthofdentalplaqueorganisms, suchasactinomycetesandspirochetes.

  24. Thecarbohydratecomponentsofcertainpellicleglycoproteinsmayserveasreceptorsforproteinsthatbindbacteriatosurfaces - e.g., adhesins, Тherebythe adhesinscontributingtobacterialadhesiontothetooth.

  25. Thebindingsitesonthepellicle, are alsohostproteins, including: • immunoglobulins (i.e., antibodies), • theenzymelysozyme, and • proteinsofthecomplementsystem. Thesehostproteinsoriginatefromsalivaandgingivalsulcusfluid.

  26. АnantagonisticrelationshipoftenexistsbetweendifferenttypesofbacteriaАnantagonisticrelationshipoftenexistsbetweendifferenttypesofbacteria competingforthebindingsites. • Forexample: ithasbeenshownthatsomestreptococcisynthesizeandreleaseproteinscalledbacteriocins, whichcaninhibitsomestrainsofActinomycesandActinobacillusspecies.

  27. DentalPlaqueFormation • Allbacteriathatinitiateplaqueformation comeincontactwiththeorganicallycoatedtoothsurfacebychance. • Forcesexistthattendeithertoallowbacteriatoaccumulateonteethortoremovethem. • Shiftsintheseforcesdeterminewhethermoreorlessplaqueaccumulatesat a givensiteon a tooth.

  28. Bacteriatendtoberemovedfromtheteethduringmasticationoffoods, bythetongue, andbytoothbrushingandotheroralhygieneactivities. • Forthisreason, bacteriatendtoaccumulateonteethinsheltered, undisturbedenvironments, whichbasicallyaresitesatrisk. • Thesesitesincludetheocclusalfissures, thesurfacesapicaltothecontactbetweenadjacentteeth, andinthegingivalsulcus.

  29. Therefore, itisnocoincidencethatthemajorplaque-baseddiseases - cariesandinflammatoryperiodontaldiseasesariseatthesesiteswhereplaqueismostabundantandstagnant.

  30. Initialplaqueformationmaytakeaslongas 2 hours. • Colonizationbeginsas a seriesofisolatedcolonies, oftenconfinedtomicroscopictoothsurfaceirregularities.

  31. Withtheaidofnutrientsfromsalivaandhostfood, thecolonizingbacteriabegintomultiply. • About 2 daysarerequiredfortheplaquetodoubleinmass, • Duringwhichtimethebacterialcolonieshavebeengrowingtogether.

  32. Themostdramaticchangeinbacterialnumbersoccursduringthefirst 4 or 5 daysofplaqueformation. • Afterapproximately 21 days, bacterialreplicationslows, andplaqueaccumulationbecomesrelativelystable.

  33. Theincreasingthicknessoftheplaquelimitsthediffusionofoxygentotheentrappedoriginal, oxygen-tolerantpopulationsofbacteria. • As a result, theorganismsthatsurviveinthedeeperaspectsofthedevelopingplaqueareeitherfacultativeorobligateanaerobes.

  34. Theformingbacterialcoloniesarerapidlycoveredbysaliva. • Whenseenwiththescanningelectronmicroscope, growingcoloniesprotrudefromthesurfaceoftheplaqueasdomes.

  35. “Domes” have appearanceof a clusterofigloosbeneathnewlyfallensnow Scanningelectronmicrograph ofdomeformationintheplaque. .

  36. Inindividualswithpoororalhygiene, superficialdentalplaquemayincorporate : - fooddebris , - humancellssuchasepithelialcells (desquamatedcells) - leukocytes. • Thisdebrisiscalledmateriaalba, whichliterallymeans "whitematter.“ • Unlikeplaque, itisusuallyremovedeasilybyrinsingwithwater. cloud

  37. Attimes, theplaquedemonstratesstaining, whichiscausedbychromogenicbacteria, whichproduce a brownpigment.

  38. MolecularMechanismsofBacterialAdhesion • Theinitialbacterialattachmenttotheacquiredpellicle ( A)isthoughttoinvolvephysicochemicalinteractions (e.g., electrostaticforcesandhydrophobicbonding) betweenmoleculesoftheaminoacidsphenylalanineandleucine.

  39. detailsA. A sidechainof a phenylalaninecomponentof a bacterialproteininteractsviahydrophobicbondingwith a sidechainof a leucinecomponentof a salivaryglycoproteinintheacquiredpellicle.

  40. Thehydrophobicityofsomestreptococci, iscausedbycellwall-associatedmoleculesincludingglucosyltransferase, anenzymethatconvertstheglucoseportionofthesugar, sucrose, intoextracellularpolysaccharide. • Someglucosyltransferaseshavebeendesignatedashydrophobins. • Thesepolysaccharidesinclude "sticky" glucansthat, throughhydrogenbonding, arethoughttocontributetothemediationofbacterialadhesion (Fig. C). • Oncethebacteriaadhere, theyareoften "entombed" asadditionalglucanisproduced.

  41. C.Thehost'sdietarysucroseisconvertedbythebacterialenzyme, glucosyltransferase, totheextracellularpolysaccharide, glucan, whichhasmanyhydrophobicgroupsandcaninteractwithaminoacidside-chaingroups, suchasserine, tyrosine, andthreonine. intheacquiredpellicle.

  42. MolecularMechanismsofBacterialAdhesion

  43. B.Thenegativelychargedcarboxylgroupof a bacterialproteinisattractedto a positivelychargedcalciumion (i.e., electrostaticattraction), whichinturnisattractedto a negativelychargedphosphategroupof a salivaryphosphoproteinintheacquiredpellicle.

  44. Bacteriaalsohaveexternalcell-surfaceproteinstermedadhesins, whichhavelectin-likeactivity, becausetheycanbindtocarbohydratecomponentsofglycoproteins. • Тheadhesinsmaybelocatedonbacterialsurfaceappendages, suchasfimbriae (FigureD). • Fimbria-associatedadhesinsprobablymediatebacterialadhesionviaionicorhydrogen-bondinginteractions.

  45. D.Thefimbrialsurfaceappendageextendsfromthebacterialcelltopermitthe terminal adhesinportiontobindto a sugarcomponentof a salivaryglycoprotein

  46. Facultativeanaerobescanexistinanenvironmentwithorwithoutoxygen; • obligateanaerobescannotexistinanenvironmentwithoxygen. • Lectinsareplantproteinswithreceptorsitesthatbindspecificsugars.

  47. Anothermolecularmechanismofbacterialadhesioniscalciumbridging. (Figure B). • Inthisprocesspositivelycharged, divalentcalciumionsinthesalivahelptolinkthenegativelychargedcellsurfacesofbacteriatothenegativelychargedacquiredpellicle

  48. BacteriaintheDentalPlaque • Thebacteriacolonizetheteethin a reasonablypredictablesequence. • Thefirsttoadhereareprimarycolonizers, sometimesreferredtoas "pioneerspecies”. • Thesearemicroorganismsthatareabletostickdirectlytotheacquiredpellicle.

  49. Thosethatarrivelateraresecondarycolonizers. • Theymaybeabletocolonizeanexistingbacteriallayer, buttheyareunabletoactasprimarycolonizers. • Generallyspeaking, theprimarycolonizersarenotpathogenic.

  50. Iftheplaqueisallowedtoremainundisturbed, iteventuallybecomespopulatedwithsecondarycolonizersthatarethelikelyetiologicagentsofdentalcariesandperiodontaldiseases. • Theearliestcolonizersarecocci (sphericalbacteria), especiallystreptococci, whichconstitute 47% to 85% ofthecellsfoundduringthefirst 4 hoursafter professional toothcleaning. • Theseorganismstendtobefollowedby shortrodsandfilamentousbacteria.

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