UnitTwoTHEULTRASTRUCTUREOFORALPATHOLOGY(Theultrastructureofpathologicalinoralcavity)Itisnotpossiblewithinthescopeofthiscontributiontodealindepthwiththeelectronmicroscopicallyfeaturesofthedifferentpathologicchanges,whichmayappearintheoralcavity,jawbone,andsalivarygland.Theoralregioncontainsalltypesofhardtissuesfoundinthebody.Further,thenormalmucosalliningexhibitsagreatervariationinstructurethanfoundintheentirethinsurface.Theoralcavitygivesrisetodiseasesnotfoundelsewhereinthebodyand,additionally,agreatvarietyofsystemicdiseasesmightexpressthemselvesintheoralcavityandparaoralregions.Inthefollowingchapters,ultrastructuralfeatureshavebeenselectedtodemonstrateasmanyaspossibleofthepathologicconditions,whichmanyappearmoreorlessfrequentlyintheoralcavity.Thismaygiveallofyoutheimpressionofdealingwithanelectronmicroscope,oralpathologicjumblemarket,butitishopedthatwherefurtherdetailsofagiven,described,pathologicconditionaresoughtthereferenceswillprovidetherequiredinformation.I.DentalHardTissues1.lNormaldentalenamelSeveralstudiesareavailabledealingwiththeultrastructuralfeaturesofnormalandcariousenamel,butingeneraltheuseofthetransmissionelectionmicroscopeinthestudyofdentalhardtissuehavebeenratherdisappointing,mainlybecauseofthegreatdifficultiespreparingthinsectionsundecalcifiedmaterial.Whendealingwithdentalenamel,whichundernormalconditionsconsistsof96percentinorganicmaterial,thetechnicalproblemsintissuepreparationareconsiderable.Fearnheadfirstdescribedsectionsoffull-mineralizedhumandentalenamalthinenoughtobeexamineddirectlybyelectronmicroscopy.Themostcommonappearanceofnormalhumanenamelwasrowsofinterdigitatingprims,eachprismhavinga"head"anda"tail"regionwhencutintransversesection.Thisshapewasdescribedasa"key-hole"Theshapesofthecross-sectionedindividualprismsappearasaresultofasuddenchangeintheorientationofthecrystallitesattheboundariesbetweenprisms.Thecrystalliteorientationintheheadregionispredominantlyparalleltothelongaxisoftheprism,withagradualchangeintheapparentlengthofthecrystalliteswithinasingleprismonmovingfromtheheadtothetailregion.Thisarrangementisconsistentwithwhathasbeenpreviouslysuggested,basedonx-raydiffractionandpolarizedlightmicroscopystudy.Insectioncutparalleltothelongaxisoftheenamelprisms,theheadandtailregionsofadjacentprismsappearasalternatingbands.Theonlydifferencebetweentherebandsisoneofcrystalliteorientation.l.2CariousenamelUltrastructurestudiesbeenshownthatcariousenamelexhibitsadiffusedemineralization,withanincreaseinintercrystallitedistanceaffectingallareaswithintheprismsandinterprismaticenamelseveralworkershaveobservednarrowchannels,50-100nm.wide,partiallysurroundingtheprismsinthecarioustissuewhenexaminedintransversesection.Theeffectsofcariousonindividualcrystalsinenamalappeartobeoftwotypes.Firstlymineralisremovedfromtheexternalsurfaceofthecrystals,seenasanirregularityoftheirmargins.Inthesecondtype.Centraldefectsarefound,thepreferentiallossofcrystalcentersalongthelatticec-axis,resultingintheappearanceof"hairpin"shapes.Intransversesection,thedamagedcrystalsareseenashollowhexagonsorrectangles.l.3CariousdentinSeveralstudieshavebeenpreformedonultrastructurefeaturesofcariousdentin.Mosttubulesinthetranslucentzoneobservedinthelightmicroscopeareoccludedbymineraldeposits,whichcloselyresembleperitubulardentin.Intheouterpartsofthezoneofbacterialpenetrationmanytubulescontainleaf-shapedcrystals,whichmayrepresentoctacalciumphosphate,andlargerhombohedralorroundedisodiametriccrystalswhichappeartobewhitlockite.Althoughextensivedemineralizationisrecordedintheintertubulardentin,bacteriaremainconfinedtotubuleswheretheyareincompletelysurroundedbyremnantsfrompreviouslysclerosedtubulesorremnantsofperitubulardentin.Occasionally,mineralizationoftheinvadingbacteriaisrecorded.l.4CariouscementumUltrastructurestudiesoncariouscementumhavedemonstratedthatthismineralizedtissuedissolvesinanirregularmanner,disclosingthecrossbandingofthecollagenousmatrix.Incontrasttoenamelanddentin,large,rhombohedralcrystalshaveonlybeendescribedinonespecimenofcariouscementum.2.OralMucosaandDiseases2.lNormaloralmucosaCellsarisingbydivisioninthebasalregionoftheepitheliumundergoaprocessofdifferentiationtoformaprotectivesurfacelayer.Thisprocessisnotidenticalinthevariousregionsoftheoralmucosa,andasaconsequencewecanrecognizedifferenttypesofsurfacethatreflectdifferentpatternsofdifferentiation.Thesurfacelayersmaygenerallybedividedintothreetypesdescribedasortho-keratinized,para-keratinizedandnon-keratinized.Ithasalreadybeenpointedoutthatthemajor{unctionoftheoralepithelumistoformaprotectivesurfacelayer,andthatthissurfacehasdifferentcharacteristicsindifferentregions.Thebasalepithelialcellsrepresenttheleastdifferentiatedcellsoftheepithelium;theypossessnotonlytheunsusualorganellesseeninothercelltypesbutalsosomecharacteristicfeaturessuchastonotilamentthatdistinguishthemfromthecellsofmostothertissuetonofilamentarefineintracellularproteinstrands,some8nmindiameterwhicharrangedtogetherinbundles,formtonofibrilsvisiblewiththehigherpowersofthelightmicroscope.Membrane-coatinggranule,alsocalledanOdlandbodyorkeratinosome.Thegranuleshaveadifferentmorphologyinkeratinizedandnon-keratinizedepithelium.Inthegranularlayerofkeratinizingoralepithelium.Manylamellatemembrane-coatinggranulesareapparent.Intheintermediatelayerofnon-keratinizedoralepithelium,Anumberof"membrane-coatinggranules"arepresentandeachwithaboundingmembraneandcentralcore.Keratohyalingranule,Inkeratinizinoralepitheliumthecharacteristicfeatureofthegranularlayeristhekeratohyalingranule.keratohyalingranulesareirregularinbothsizeandshapeandinclosecontactwithtonofilament.Thenon-keratinizedregionsoftheoralmucosadonotpossessagranularlayer,butoccasionallythepresenceofkeratohyalingranuleswhich,althoughsurroundedbyribosomes,differfromtheircounterpartsinkeratinizedepitheliumbyappearingmoreregularandnotbeingassociatedwithtonofilaments.2.2GingivitisandperiodontitisThetissuesupportingtheteethisthesiteoftheoralmucousmembranemostcommonlyaffectedbyinflammatorychanges,i.e.,gingivitisandperiodontitis.Ithasbecomewidelyacceptedthatbacteriaand/orbacterialmetabolitesinthedentalplaquecontributetheprimaryetiologicagentresponsiblefortheinflammatoryreaction.Ultrastructurestudiesofbiopsyspecimensfrompatientswithchronicgingivitishaveshownthatwidenedintercellularspacesoftheepitheliumareacommonfeature.Thechangesintheintercellularrelationshipsareinterpretedasthemorphologicalevidencefortheincreasedexudationintothesulcusorpocketobservedintheirpatients.Neutrophilicleukocytesandbacteriacontainedwithinthisgingivalfluidexhibitacidphosphataseactivityattheulrastructurallevelavariablenumberofinflammatorycells,mainlyneutrophilicleukocytesandlymphocytes,areabservedintercellularlyconcomitantwithlysosomes(releasedfromdisruptingneutrophils)andagranularprecipitate.TheultrastrucureoftheepitheliumliningthegingivalpocketinchronicperiodontitishasbeenstudiedbyTakaradaetal.Intheupperpartofthepocketsmembrane-coatinggranules.keratohyalingranules,andathickeningoftheplasmamembraneisrecorded,reflectingaKeratinizationpotentialofthispartoftheepithe!ium.Thisfindingmayindicatethattheinflammatoryprocesshasinducedashiftintheepithelialdifferentiationpatternasthecrevicularepitheliumisnonkeratinizedinnormalgingiva.Thelowerpartofthepocketepitheliumdemonstratesfeaturessimilartothosedescribedaboveinheavilyinflamedchronicgingivitis,i.e.,wideningofintercellularspaces,decreasednumberofdesmosomes,andepithelialcelldegeneration.Areaswithadiffuseorcompletelyabsentbasementmembraneareobservedinchronicgingivitis,andinperiodontitisinaddition,descriptionsofthickening,detachment,multiplication,fragmentation,anddislocationofthelaminadensaaresimilartothosefoundinthebasementmembraneareaelsewhereinthebodyduringinflammation.Mostofthefibroblastsatthereactionsiteexhibitstructuralalterationsasvizualizedbyelectron-lucentnuclei,swollenmitochondria,vacuolizationofendoplasmicreticulum,ruptureofthecellmembrane.23LeukoplakiaLeukoplakiaisawhiteplaqueorpatchwhichcannotberemovedbyrubbingandwhichcannotbeclassifiedasanyotherdisease.Thehistologicalfeaturesconfinedtoleukoplakiaincludehyperorthokeratosis,hyperparakeratosis,acanthosis,andeventuallydysplasiaandcarcinomainsitu.Themann(1958)andFasskeetal(1958)firstreportedelectronmicroscopicexaminationofhumanoralleukoplakia.Simpleleukoplakia:Mostlesionsclassifiedclinicallyassimpleleukoplakiashowedonlightmicroscopicexaminationepithelialhyperplasia,acanthosisortho-orhyperorthokeratosis,awell-developedgranularlayer,averymildinflammatorycellreactionintheconnectivetissue.Epithelialhyperplasia,acanthosis,partlyhyperparakeratosis,partlyhyperorthokeratosis,withanunderlyinggranularlayerandminimalinfiltrationoftheconnectivetissuecharacterizedleukoplakiaverrucosa.Slightepithelialdysplasiawasobservedinsomecases.Hyperplasticepithelium,surfaceulceration,parakeratosisandmoderatetoheavyinflammatoryinfiltrationofconnectivetissuerevealedleukoplakiaerosive.Moderateorseveredysplasiawasobservedinsomecases.Ultrastructureobservations:Thebasementmembraneinsimplexandverrucousleukoplakiawascontinuous,wellpreserved,insomeplacesthickenedandmultilayered,withramificationsamongtheconnectivetissuefibers.Thewidenedintercellularspacebetweenthebasalcellswaslimitedbymultilayeredbasementmembranesinerosiveleukoplakia,butdiocontinitieswereobservedintheseplaces.Stratumbasale:thecellconnectionsformedbyinterdigitationswereloosenedinverrucousanderosiveleukoplakia,andthenumberofhemidesmosomeswasdecreasedinthelatter.Wide-basedcytoplasmicprocessescontainingribosomeswithouttonofilamentscouldbeobservedinallthreeclinicaltypesofleukoplakia.Thetonofilamentformedbundlesandthemajorityofthemitochondiawereintact.Stratumspinasum:Thevolumeofthecellsandnucleiincreasedgraduallyasthecellsapproachedthesurface.Thenumberofnucleoliincreased.Thenucleusinerosiveleukoplakiawasfoldedwithanunevenchromatindistribution.Theintercellularspacesinleukoplakiasimplexandverrucosawereslightly-andinerosivecasesmore-widened.Theinterce!lularconnectionswerepartiallylostinthelattertype,anddesmosomeswereruptured.Thetonofilamentsformedhomogeizedbundlesandwereattachedtodeomosomesatthecellperiphery.Theribosomeswereevenlydistributedinthecytoplasminleukoplakiasimplexbutformedrostte-likegroupsinleukoplakiaerosiva.Darkandclearcellsoccurredintheupperspinouslayersoferosiveleukoplakia.Thenumberofribosomeswasincreasedinthedarkcellswhiletheclearcellsshowedfewerribosomes.Stratumgranulosum:cellswithandwithoutkeratohylingranuleswereobservedinthesamelayersinsimplexandverrucousleukoplakiacases.Aggregatescomposedofribosomesgranulesoccurredonthesurfaceoftheelectron-densekeratohyalingranules.Keratohyalingranuleswerepresentonlyoccasionallyinerosiveleukoplakia.Theperipheralthickeningofthecytoplasmandthepresenceofodlandbodieswereobservedintheuppermostgranularlayersinsimplexandverrucousleukoplakia.Onthebasisoftheaboveobservations,leukoplakiasimplexandverrucosaarecharacterizedbyabundantkeratinization,increasedamountsoftonofibrils,keratohyalingranulesandOdlandbodies,aswellassignsofdyskeratosis.Incontrast,erosiveleukoplakiarevealedevidenceofdyspalsia,namely,defectsofthebasementmembrane,decreaseofhemidemoromes,pathological,cytoplasmicprocesss,lessofintercenularadherence,alterationsofthenucleusandnucleoli,degenerativechangesofmitochondriaandcharacteristicarrangementofribosomes.2.4LichenplanusTheorallesions,whichareseenmostcommonlyinthebuccalregion,exhibitvariationsintheclinicalappearance,thereticular,erosive,andplaquetypesbeingthemostfrequentlyrecordedmanifestationsofthedisease.Histopathologically,theorallichenplanuslesionsexhibitshyperparakeratosisoralternateareasofortho-andparakeratosesandatrophyratherthanacanthosis.Thepresenceofastratumgranulosum,liquefactiondegenerationofthebasallayer,andawell-definedbandinthejuxtaepitheialconnectivetissueofinflammatorycell,predominantlylymphocytesareadditionalhistoltogiccharacteristicsconfinedtothelichenplanusspecimens.Inlichenplanusseveralchangesappearinbasalcelllayerandbasementmembranearea.Thelaminadensaisthickened,anddiscontinuitiesandmultiplicationofthelaminahavebeenreported.Thepresenceofadenseorganicmassexternaltoormaskingthebasementmembranehasbeendescribed,andsuggestedtorepresentcoagulatedfluidexudateassociatedwiththediseaseprocess.ElectronmicroscopicallystudiesfocusingontheCivattebodiesseeninthedeeperlayersoftheepithelium.andinthesubjacentconnectivetissueoforallichenplanushaverevealedthatthesestructuresconsistofalteredepithelialcellsshowingchangesinbothnucleusandcytoplasm.Thecytoplasmicchangesincludethepresenceoflargenumbersoftonofilamentshowingdifferentdegreesofelectrondensity,andperipheralaggregatesofparticleshavingthesizeofribosomes,concomitantwithmitochondraexhibitingdegenerativefeatures.Thenuclearmaterialoftenappearsverysimilartothatofnormaldividiingbasalepithelialcells,suggestingthattheCivattebodiesaretheoutcomeofdegenerativechangesaffectingepithelialcellsinvariousstagesofmitosis.Thefactorsinvolvedintheproductionofsuchcellsandthereasonsforthepossibleselectiveinvolvmentofcellsundergoingmitosesareunknown.ThepresenceofCivattebodiesintheconnectivetissuehasbeensupposedtobemediatedbyphagocyticcells,i.e.,macrophages.IntherecentstudyoncutaneouslichenplanusitwasconcludedthatCivattebodiesrepresent"filamentousdegeneration"orprematurekeratinigationofkeratinocytes,thuspresentinganultrastructuretypicalofapoptoticcells.2.5Whitespongenevusinoralmucosa'Thetermwhitespongenevus,originallysuggestedbyCannon,isusedtodescribeahereditarydyskeratotichyperplasiaofthemucousmembrane.Themucosalalterationsareconfinedtotheoralcavityandonoccasiontothenasal,pharyngeal,esophageal,vaginal,anal,andrectalmucosa.Thelesionsappearasawhitish,elevatedwrinkledtissuewithaspongytexture.Itsclinicalimportanceismainlyconnectedwithdifferentialdiagnosis.Onhistologicalexaminationtheepitheliumdisplaysanoverallpatternofhyperplasia.Theparakeratoticsurfacelayeramountstotencelllayersinthickness.Keratohyalingranulesaresparselyrepresented.Intercellularedemaisacharacteristicfeatureofthespinouscelllayer.Ultrastructurally,thebasalandparabasalcellwerecylindricalcells.Thecytoplasmictonolilamentswereaggregatedintoboundles.Itwascharacteristicofkeratinizedepithelium.Inthe.middleandsuperficialstratumspinosumthetonofitamentswerehomogeneouslydistributedinthe:cellplasmaandelectron-densegranularswerelocatednearthecellboundarvandattachedtodesmosomesbytonofilaments,unlikenormalnon-keratinizedoralmucosa.ManyOdlandbodieswithalamellarstructureandirregularinbothsizeandshapewereseen.Itisconcludedthatthislesionhasadyskeratinizedprocess.Thecharacteristicfeaturesofkeratinizedoralmucosainnon-keratinizedmucosaisappeared.ThethickeningofsuperficiallayerisduetosheddingdisturbancerelatingtodysfunctionofOdlandbodies.4.OdontogenicCystsandTumors4.lKeratinizingcystsTheultrastructureofepithelialliningofkeratinzizingodontogeniccysts(keratocysts)hasbeendescribedbyHansenandKobayasi,andPhilipsenetal.HansenandKobayasidemonstratatedseveraldifferencesbetweennormalkeratinizedmucousmembraneepitheliumandcystepithelium.Thus,keratinhyalingranuleswererarelyfound,lamellatedbodieswerefew,tonotilamentswerepresentbuttheirnumberandthicknessofthebundlesdidnotincreasetowardsthesurface,andfinally,theribosomesandendoplasmicreticulumwerefoundtobeintactinthekeratinizedcells.ThesefindingswereconfirmedbyPhilipsenetal.whofurtherdemonstratedalargeamountofglycogeninthepricklecelllayersofodontogeniccysts.Asubepithelial"clearzone"withfragmentationofcollagenwasinterpretedassuggestiveofcollagenolysis.4.2AmeloblastomaAbenignbutlocallyaggressiveodontogenicepithelialtumor,theameloblastomahasnopropertiesofproducingdentalhardtissues.Itisconsideredthesecondmostcommonodontogenictumorandappearsmostfrequentlyinthelowermolarregionandramusarea.Althoughthetumorhistologicallyresemblestheenamelorgan,differentcasesandevendifferentareaswithinthesamelesionshowwidemicroscopicvariation.Ultrastructurally,ithasbeendescribedaspossessingtwoorthreecellzones,correspondingtoappearancesseenbylightmicroscopy.Asinglerowoftallcolumnarcellsisseenattheperipheryofthetumorfollicles.Theperipheralcellsareeithercloselypackedtogetherwithfewdesmosomaljunctionsortheymaybeseparatedbyclearintercellularspaces.CellswithsingleciliaandLangerhansgranuleshavebeenidentifiedwithinthetumorfollicles.Virus-likeparticlesweredemonstratedbyCsibaetal.InthisconnectionitmaybeofimportancetonotethatMainandDavehaveinducedameloblastomawithpolyomavirusinnewbornmice.Inmanyperipheraltumorcellsfindingsuchasapicalpolarizationofnuclei,thedevelopmentofrelativelycomplexendoplaxmicreticulum,amarkedincreaseinautophagolysosomeslocalizationofmitochondrianearthebasementmembraneandtheoccurrenceof"darkcells"indicateahigherlevelofdifferentiationfortheameloblastomathanisgenerallyaccepted(basedonlightmicroscopicstudies).Thejuxtaepithelialzoneofhyalinization,ultrastructurallyshowntobecomposedofdense,maturecollageninterspersedwithfinefibrils,conformingtothefeaturesofoxytalanfibres,andtheoverallmatureconnectivetissuestromatypicalofameloblastomas,mayconstitutethenoninductivemilieu,renderingamelablastomasincapableofhardtissueformation.VOCABULARYl.ultrastucture超微結構2.pathology病理3.electronmicroscope電鏡4.enamel釉質5.decalcify使脫鈣6.enamelprism釉柱7.interdigitatingprism柱間質8.crystallite晶體9.carious齲的10.demineralization脫礦11.dentin