Dental plaqueDental plaque

LectuerLectuer (4)(4)

Dr.Dr. BahaBaha ,, HamdiHamdi .AL.AL--AmiediAmiedi

Ph.D.MicrobiologyPh.D.Microbiology

it is now well established that caries &it is now well established that caries &periodontal disease are infectious diseaseperiodontal disease are infectious diseaseassociated with resident microorganismsassociated with resident microorganismsof dental plaque there are two hypothesisof dental plaque there are two hypothesisexplain that:explain that:

The specific plaque hypothesis:The specific plaque hypothesis:proposes that only a few microorganismsproposes that only a few microorganismsare involved in the oral disease processare involved in the oral disease process

NonNon –– specific plaque hypothesis:specific plaque hypothesis:considers that disease result from theconsiders that disease result from theinteraction of the whole plaque with theinteraction of the whole plaque with thehost.host.

there arethere are serveralserveral organic deposits on theorganic deposits on thesurface of the teeth these deposits includesurface of the teeth these deposits includedental plaquedental plaque,, material albamaterial alba,, pelliclepellicle,,calculuscalculus deposits,deposits,

materiamateria alba:alba: so it is the outer portion ofso it is the outer portion ofdental plaque is composed of an unorganizeddental plaque is composed of an unorganized

structure of microbial growth andstructure of microbial growth anddesquamated epithelial &white &red blooddesquamated epithelial &white &red bloodcells loosely to organized structural portion ofcells loosely to organized structural portion ofplaque and is easily removed by mechanicalplaque and is easily removed by mechanicalaction of water spray. but if it with stand theaction of water spray. but if it with stand thewater spray it is calledwater spray it is called dental plaquedental plaque

Dental plaque:Dental plaque:It is a general terms for the complexIt is a general terms for the complex

microbial community found on themicrobial community found on thetooth surface , embedded in a matrixtooth surface , embedded in a matrixof polymers derived from bacteria &of polymers derived from bacteria &saliva. For successful colonizationsaliva. For successful colonizationmicroorganism must first adhere tomicroorganism must first adhere to

a surface this involve interactiona surface this involve interactionbetween abetween a dhesinsdhesins on the microbialon the microbialsurface andsurface and ligandligand s on the hosts on the hostsurfacesurface

Dental plaque formation:Dental plaque formation:

adherence to a surface in the mouth isadherence to a surface in the mouth is

essential for survival of oralessential for survival of oral bacteria.inbacteria.in thethecause ofcause of supragingivalsupragingival plaque formation,plaque formation,

Microorganism interact with a layer of materialMicroorganism interact with a layer of materialon tooth surface called pellicleon tooth surface called pellicle

Pellical:itPellical:it is a layer of material on tooth surfaceis a layer of material on tooth surface

comprisescomprises mucinsmucins, salivary, salivary glycoproteinsglycoproteins,,

Minerals &immunoglobulin, theMinerals &immunoglobulin, the pellicalpellicalformation occurs information occurs in secoundssecounds on cleanedon cleanedenamalenamal and reaches aand reaches a maxmummaxmum thickness inthickness in9090--120 minutes120 minutes

Ecology plaque hypothesis:Ecology plaque hypothesis:

This hypothesis concerning to the mainThis hypothesis concerning to the mainfactors involve in dentalfactors involve in dental caries(salivacaries(saliva, diet,, diet,

tooth surface& plaque ecology) that whentooth surface& plaque ecology) that whensalivary composition & fermentable sugarsalivary composition & fermentable sugar

intake are within normal limits, plaqueintake are within normal limits, plaqueecology favors bacterial species thatecology favors bacterial species thatassociated with a PH of 6associated with a PH of 6--7 (streptococcus7 (streptococcus

oralisoralis& streptococcus& streptococcus sanguissanguis) and intact) and intactenamel& dentine surface. However if theenamel& dentine surface. However if theamount &frequency of intake fermentableamount &frequency of intake fermentable

Sugar increases markedly, with or withoutSugar increases markedly, with or withoutchanges in salivarychanges in salivary composition&functioncomposition&function

plaque ecologyplaque ecology favoursfavours acidacid--toleratingtoleratingbacteria( strepbacteria( strep mutansmutans &lactobacilli&lactobacilli sppspp))

that are associated with lowthat are associated with low--PH less than5PH less than5

andand demineralizeddemineralized tooth surfaces .thattooth surfaces .thatshow only two extremeshow only two extreme situations(healthsituations(health&&

Disease)butDisease)but in reality very wide range ofin reality very wide range ofpossible interaction can occur involvingpossible interaction can occur involvingthe main a etiological factors some whichthe main a etiological factors some whichtend towards demineralization &disease&tend towards demineralization &disease&others towardsothers towards reminaralizaton&healthreminaralizaton&health

There are four stages in plaqueThere are four stages in plaque

formation:formation:

11--transport.transport.

22--initial adhesion.initial adhesion.

33--irreversible attachment.irreversible attachment.

44--colonization.colonization.

StagE1StagE1--TransportTransport

Bacteria must first approach theBacteria must first approach thesurface to which they will later bindsurface to which they will later bindby several wayby several way

11--liquied flow .liquied flow .

22--Diffusion through brown motion.Diffusion through brown motion.

33--bacterial movement (bacterial movement (chemotacticchemotacticactivity)activity)

Two types of force are involved at thisTwo types of force are involved at thisstage at distances of 10stage at distances of 10--100 nm :100 nm :

aa--VanVan derder WaalesWaales

bb--electrostacticelectrostactic forcesforces

As bacterium approaches closer(2nm)As bacterium approaches closer(2nm)

Strong forces, such as hydrogen bondingStrong forces, such as hydrogen bondingbetween hydroxyl group in the pelliclebetween hydroxyl group in the pellicle&phosphate group in bacterial cell wall&phosphate group in bacterial cell wallcome into plaque.come into plaque.

stage 2stage 2--Initial adhesionInitial adhesion

Stage 3Stage 3--Attachment:Attachment:

More permanent attachment canMore permanent attachment can occueroccuerby covalent, ionic or electrostatic bondingby covalent, ionic or electrostatic bondingthese bonds form between specificthese bonds form between specificreceptors on host surface termedreceptors on host surface termed ligandsligands,,and component situated on bacterialand component situated on bacterialappendegesappendeges called adhesion such ascalled adhesion such asfimbriaefimbriae so oral bacterial attachment andso oral bacterial attachment andtherefore plaque formation is affected bytherefore plaque formation is affected byfactors of host and microbial &saliva .factors of host and microbial &saliva .

Stage 4Stage 4--colonizationcolonizationOnce bond to surface, the bacterium canOnce bond to surface, the bacterium can

divide and remain attached extracellulardivide and remain attached extracellularproducts are formed and daughter cellproducts are formed and daughter cellrepeat the process so thatrepeat the process so that microcoloniemicrocoloniedevelop,saliverydevelop,salivery glycoglyco--proteins &proteins &dieterydieterysugars such as glucose &sucrose cansugars such as glucose &sucrose canmetabolized leading to the formation ofmetabolized leading to the formation ofbacterial cell wall, waterbacterial cell wall, water--soluble&insolublesoluble&insoluble

Polysaccharide are important in plaquePolysaccharide are important in plaqueformationformation

Plaque Development:Plaque Development:

Gradually the micro colonies producingGradually the micro colonies producingcomplex three dimensional arrangementcomplex three dimensional arrangement

The resultantThe resultant biofilmbiofilm is called dentalis called dentalplaqueplaque plaqueplaque maturation by increasingmaturation by increasing

quantity &diversity of microorganisms onquantity &diversity of microorganisms on

The tooth surface .after 7 days stillThe tooth surface .after 7 days stillstreptococci the main organism presentstreptococci the main organism present,but after 14 days there is a shift to,but after 14 days there is a shift toanaerobic rods &anaerobic rods &filmentsfilments, with comprising, with comprising

Only 15 % of streptococciOnly 15 % of streptococci

Microbial plaque:Microbial plaque: study of the dentalstudy of the dentalplaque showed the following group in theseplaque showed the following group in thesepercentage:percentage:

Facultative streptococci 27 %Facultative streptococci 27 %

FacultativeFacultative diphtheroidsdiphtheroids 23 %23 %

AnaerobicAnaerobic diphtheroidsdiphtheroids 18 %18 %

PeptostreptococciPeptostreptococci 13 %13 %

VeillonellaVeillonella 6 %6 %

BacteroidesBacteroides 4 %4 %

FustobacteriaFustobacteria 4 %4 %

NeisseriaNeisseria 3 %3 %

VibrioVibrio 2 %2 %

Chemical composition of plaque: containsChemical composition of plaque: contains

* water75* water75--80%,80%,

* protein 40* protein 40--50%. Of dry weight50%. Of dry weight

* carbohydrate 13* carbohydrate 13--18% of dry weight18% of dry weight

*lipid 10*lipid 10--14%. Of dry weight .14%. Of dry weight .

Inorganic compound:Inorganic compound:calicum,phosphatecalicum,phosphate phosphate,phosphate, fluriedfluried&small amount of( mg, k)&small amount of( mg, k)

CalculasCalculas::

when dental plaquewhen dental plaque calcified;salivacalcified;saliva isissupersuper--saturated bysaturated by calicum,phosphatcalicum,phosphat

Ion ,which accumulate within theIon ,which accumulate within theplaque matrix together with organicplaque matrix together with organicdebris from deaddebris from dead microorganisms,thatmicroorganisms,that

lead to formation of insolublelead to formation of insoluble calicumcalicumphosphatephosphate crystals,whichcrystals,which coalesce tocoalesce toform calculus 20% organic compoundform calculus 20% organic compound

80%mineralized material .80%mineralized material .