国外口腔解剖乳牙.ppt

THEDECIDUOUSDENTITIONINTRODUCTIONTheworddeciduouscomesfromaLatinwordmeaningtofalloff.Deciduousteethfallofforareshedlikeleavesfromadeciduoustree.Thedeciduous,primary,or,astheyoftenreferredtocolloquially,(MILK)teeth,havearelativelyshortlife-spanbeforetheyexfoliatedtobereplacedbythepermanentteeth.Thisusuallyoccursbetweentheagesof6and13years.Thedeciduousincisorsandcanineshavepermanentsuccessorbutthefirstandseconddeciduousmolarsarereplacedbythefirstandsecondpremolarsrespectively.ThedeciduousdentitioncomprisesfewerteeththanthepermanentdentitionwithatotalofTENmaxillaryandTENmandibularteeth.Theyareasfollows,inorderofpositionfromthemidline:A-First(central)incisor.B-Second(lateral)incisor.C-Canine.D-Firstmolar.BCDEAE-Secondmolar.Theshorthandformulaforthedeciduousteethisasfollows:I2C1M2=10212GENERALCHARACTERISTICSThedeciduousteethgenerallyhaveseveralimportantdifferencesinmorphology,composition,sizecolouraslistedbelow:1-Thedeciduousteetharesmallerthanthepermanentteeth.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETHPRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH2-Theenamelofthedeciduousteethiswhiterandmoreopaque,whichgivesthecrownalightercolourthanthatofthepermanentteeth.3-Theenamelofthedeciduousteethismorepermeableandmoreeasilyworndown.Thedegreeofpermeabilityislessenedafterthestartofrootresorption.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH4-TheDEPTHOFENAMELismoreconsistentandthinnerthaninthepermanentteeth,beingfrom0.5mmto1.00mmthick.PRINCIPALDIFFERENCESBETWEENDECIDUOUSTEETHANDPERMANENTTEETH5-Deciduousteethhaveapronouncedcervicalmargin.Theenamelbulges,insteadoftaperinggently,atthecemento-enamljunction,whichisstraighterthaninthepermanentteeth.Thiscervicalbulgeisaccentuatedinthemesiobuccalareaofdeciduousmolars.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH6-Innewlyerupteddeciduousteeth,thecuspstendtobemorepointed.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH7-Therootsofthedeciduousteethareshorter,lessstrongandlighterincolourthanthoseofthepermanentteeth.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH8-Therootsofanteriordeciduousteetharelongerinproportiontothecrown.Therootsofposteriorteetharemoredivergenttoallowforthedevelopingpermanentsuccessor.Theyflareoutfromeachotherwiderthanthecrownmeasurement,andformaminimalcommonroottrunk.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH9-Thepulpchambersarelargerthaninthepermanentteethandfollowtheexteriormorphologyofthetoothmoreclosely,theretends,thereforetobelessdepthofdentine.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH10-Therootcanalofdeciduousteethareveryfine.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH11-Usuallytherearenodepressionsorperikymataonthelabialsurfaceofthecrownoftheincisors.Thesesurfacesaresmooth.ONTHEANTERIORTEETHONTHEANTERIORTEETH12-Therearenomamelonesontheincisaledges.13-Thecervicalridgeonthefacialsurfacesisprominent.ONTHEANTERIORTEETH15-Therootisnarrowmesiodistally.ONTHEANTERIORTEETH14-ThecingulaeareprominentorseemtobulgeandoccupyaboutonethirdofthecervicoincisallengthlinguallyONTHEPOSTERIORTEETH16-Themolarcrownhaveanarrowchewing(occlusaltable)buccolingually.17-Themolarsoccluosalsurfacesareshallow.Inotherwords,thecuspsareshort,theridgesarenotpronounced,andthegroovesarecorrespondinglynotasdeep.ONTHEPOSTERIORTEETH18-Themolarcrownsarewidemesiodistally,yetveryshortcervico-occlusally.19-Thebuccalcuspsofmolarsarenotpointedorsharp,withcuspslopesmeetingataverywideobtuseangle.20-Therearefewgroovesordepressionsinallsurfacesofthecrowns.ONTHEPOSTERIORTEETH21-Thecervicalridgeisprominentmesially(itiseasytodistinguishrightsfromleft).ONTHEPOSTERIORTEETH22-Thesecondmolarsarelargerthanthefirstmolars.23-Therootfurcationisnearthecrown,andthereislittleifanyroottrunk.ONTHEPOSTERIORTEETHONTHEPOSTERIORTEETH24-Therootsarewidelyspreadbeyondtheconfinesofthecrowntoallowforthedevelopingpermanentsuccessors.ONTHEPOSTERIORTEETHONTHEPOSTERIORTEETHONTHEPOSTERIORTEETH25-Rootsarethinorslender.ONTHEPOSTERIORTEETHONTHEPOSTERIORTEETH26-Thesecondmolarrootsarespreadmorewidelythanthefirstdeciduousmolar(oppositeofthepermanentmolars).ED67IMPORTANTFUNCTIONSOFSOUNDDECIDUOUSTEETH1.Maintenanceofanormalappearance.2.FormulationEfficientmasticationoffood.3.ofclearspeech.4.Maintenanceofaproperdiet.Missingorbadlydecayedteethmaybeonereasonthatyoungchildrenrejectfoodsthataredifficulttochew.IMPORTANTFUNCTIONSOFSOUNDDECIDUOUSTEETH5-Avoidanceofinfectionandconcomitantpain.Anabscessfromadeciduoustoothcancausedarkspots(Turner’sspots)onthepermanenttoothdevelopingbeneathit.6-Maintenanceofspaceandarchcontinuityfortheemergenceofpermanentteeth.Chronology:Initialcalcification3-4monthsinuteroCompletionofcrown4monthsEruption7½monthsCompletionofroot1½yearsMAXILLARYFIRST(CENTRAL)DECIDUOUSINCISORMAXILLARYFIRST(CENTRAL)DECIDUOUSINCISORPRINCIPALIDENTIFYINGFEATURES:1-Roundeddisto-incisalangle:sharpmesio-incisalangle.2-Similartomaxillaryfirstpermanentincisorbutsmallerandchubbieroverall.3-Largelingualcingulumandpronouncedbulgeonlabialsurface.MAXILLARYFIRST(CENTRAL)DECID