口腔解剖生理学之国外---the_deciduous_dentition乳牙

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1、THEDECIDUOUSDENTITIONINTRODUCTIONTheworddeciduouscomesfromaLatinwordmeaningtofalloff.Deciduousteethfallofforareshedlikeleavesfromadeciduoustree.Thedeciduous,primary,or,astheyoftenreferredtocolloquially,(MILK)teeth,havearelativelyshortlife-spanbeforetheyexfoliatedtobereplacedbythepermanentte

2、eth.Thisusuallyoccursbetweentheagesof6and13years.Thedeciduousincisorsandcanineshavepermanentsuccessorbutthefirstandseconddeciduousmolarsarereplacedbythefirstandsecondpremolarsrespectively.ThedeciduousdentitioncomprisesfewerteeththanthepermanentdentitionwithatotalofTENmaxillaryandTENmandibul

3、arteeth.Theyareasfollows,inorderofpositionfromthemidline:A-First(central)incisor.B-Second(lateral)incisor.C-Canine.D-Firstmolar.BCDEAE-Secondmolar.Theshorthandformulaforthedeciduousteethisasfollows:I2C1M2=10212GENERALCHARACTERISTICSThedeciduousteethgenerallyhaveseveralimportantdifferencesin

4、morphology,composition,sizecolouraslistedbelow:1-Thedeciduousteetharesmallerthanthepermanentteeth.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETHPRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH2-Theenamelofthedeciduousteethiswhiterandmoreopaque,whichgivesthecrownalightercolourtha

5、nthatofthepermanentteeth.3-Theenamelofthedeciduousteethismorepermeableandmoreeasilyworndown.Thedegreeofpermeabilityislessenedafterthestartofrootresorption.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH4-TheDEPTHOFENAMELismoreconsistentandthinnerthaninthepermanentteeth,beingfrom0.5mmt

6、o1.00mmthick.PRINCIPALDIFFERENCESBETWEENDECIDUOUSTEETHANDPERMANENTTEETH5-Deciduousteethhaveapronouncedcervicalmargin.Theenamelbulges,insteadoftaperinggently,atthecemento-enamljunction,whichisstraighterthaninthepermanentteeth.Thiscervicalbulgeisaccentuatedinthemesiobuccalareaofdeciduousmolar

7、s.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH6-Innewlyerupteddeciduousteeth,thecuspstendtobemorepointed.PRINCIPALDIFFERENCESBETWEENDECIDUOUSANDPERMANENTTEETH7-Therootsofthedeciduousteethareshorter,lessstrongandlighterincolourthanthoseoftheperma