UnitFourINTERPRETATION：RADIOGRAPHICANATOMYOFTHEMANDIBLETheGenialTubercleInocclusalviews,itcanbeobservedasasmallprominenceonthelingualside.TheMentalForamenInmostradiographsofthebicuspidregion,thisstructurecausesaradiolucencyintheapicalareaoftheseteeth.Itmaybesuperimposedontheapexofatooth.TheInferiorDentalCanalThisstructureisusuallyvisibleinradiographscoveringtheposteriormandible;itisaradiolucencyapproximately2.5-3mmwideborderedbyopaquelinesatthesuperiorandinferiorlimits.Itdescribesacurvebetweenthementalforamenanditspointofexitintheramus,remainingatevenwidthuntilexiting,whenitopensintoafunnelshape.TheMylohyoidRidgeInperiapicalviewsoftheposteriormandible,theremaybeanopacityincreasingindensityfromabovedown.Atthelowerlimitoftheridge,thereisanabruptreturntonormaldensity.TheExternalObliqueRidgeInthemolarregionandthelowerramus,thisstructureisseenasapositiveradiopaquelineclosetothesurfaceofthealveoluscurvingsuperiorly.TheAngleoftheMandibleTheSigmoidNotchIncertainextraoralviews,thiscanbeseenasasmoothcurveextendingbetweenthecondyleandthecoronoidprocess.TheCoronoidProcessInoccipitomentalprojections,panoramicviews,andoccasionallyintraoralviewsoftheposteriormaxilla,thisstructurecanbeseen.TheCondyleThecondylemaybeseeninroutineextraoralviews,butitisbettervisualizedinspecializedviewsofthetemporomandibularjoint.VariantsofNormalStafnecavity.LaminaDuraAndPeriodontalStructureINTERPRETATION:RADIOGRAPHICANATOMYOFTHEMAXILLAAnteriorNasalSpineThisareashowsasatriangularprojectioninthemidlineonthebuccalside.IntermaxillarySutureThisstructurecausesathinlinerradiolucencyinthemidlineofthepalateoccasionallyextendingtothecrestofthealveolus.NasalSeptumThisisanothermidlinestructure.Anteriorly,itiscartilageandissometimesdifficulttodetectradiographically;moreposteriorly,itisboneandeasilyseen.TheNasalAirwaysDetectableiswidebilateralradiolucenciesrunninganteroposteriorlyoneithersideofthemidline.IncisiveCanalTheCanineFossaSituatedbetweentherootsofthelateralandthecuspidisadepressioninthebuccalplateofbonewhichcausesanill-definedradiolucency.ZygomaticBoneTheattachmentofthezygomaticbonetothemaxillacausesapronouncedU-shapedradiopacityintheregionoftheapicesofthefirstandsecondmolars.TuberosityTheroundedoutlineofthisstructureisimmediatelyposteriortothethirdmolarandmayberelativelyradiolucent.HamularProcessThehamularprocessisoccasionallyseenasasmallbonyprojectionposteriortothetuberosity.Ithasseveraldifferentappearancesandmaybesuperimposedonthetuberosity.NasolacrimalDuctInocclusalprojections,theseareseenintheposteriormaxilla,Theyareonthepalatalsideofthethirdmolarsandareovalradiolucencies.TheAntrumRadiographicAppearancesofCystsClassificationofCystsBONESOFTTISSUEODONTOGENICNONODONTOGENICDental(Radicular)Maxilla:NasolabialLateralperiodontalNasopalatineThyroglossalDentigerous(follicular)MedianBranchialPrimordialGlobulomaxillaryMucusretentionKeratoMandible:DermoidMultipleMedianEruptionSimplebonecystCalcifyingodontogenicAneurysmalbonecystDental(Radicular)CystsThesearecausedbyanonvitaltoothorroot,toxinsfromwhichstimulatetheepithelialcellsofMalasseztomultiply.Aradiolucentareacircularinoutlineuntilanobstructionisencountered,clearlydefinedmargins,acortexsurroundingthelesion,andoccasionllyfenestrationcausingasmallareaofincreasedradiolucency.Expansionoftheboneoccurs,asevidencedinocclusalviews.intheadult,itisusuallythebuccalplateofbonewhichismostaffected;inthechilditmaybethebuccal,butoftenitisthelingualplateaswell.sometimesthecoveringboneisextremelythin.Inthemandiblethelowerborderismoreresistancetochangethanthelingualorthebuccalplates,Theinferiordentalcanalmaybedisplaced.Inadultsalong-standingcystmaycauseexternalresorptionofteeth;inchildrenitismorelikelytomovetheteeth.Cystsassociatedwithamaxillarylateraltendtogrowintothepalate.Cystsintheposteriormaxillaoftenencroachupontheantrum.Acystmayberesponsibleforapathologicalfracture.Occasionally,theinitiatingtoothorroothasbeenremoved,andthecyst,whichhascontinuedtogrow,isinanedentulousarea.Thisisreferredtoasaresidualcyst.LateralPeriodontalCystAlateralperiodontalcystoriginatesintheperiodontalligamentatthesideofaroot.Itiscausedbyinfectioninthegingiva!orperiodontaltissues,andthetoothwithwhichitisassociatedcanbevital.Aradiolucencyconnectedwiththeperiodontalligament.Whenitissmall,itiscircular,butasitcontactstheneighbouringtooth,itcurvesaroundit.Theradiolucencyissurroundedbyacortex.DentigerousCystsAdentigerouscystisoneinwhichanuneruptedtoothisinvolved,anditisthoughttooriginatefromthereducedenamelepithelium.Dentigerouscystsareseenmostfrequentlyintheyoungeragegroup.Aradioluency,whichiscircularuntilit,meetsanobstructionwhentheshapeismodified.Thelesioniscorticated.Thecrown,partofthecrown,orcrownandpartoftherootareinthecyst.Owingtoeruptionproblem,thethirdmolars,thesecondbicuspids,andthemaxillarycuspidsaremostcommonlyinvolved,butitcanbeanytooth,Asupernumerarytoothcanbethecause.Teetharemovedveryeasi!yandmayevenbeinverted,Inthecaseoftheposteriormaxilla,theinvolvedtoothcanbemovedintotheareanormallyoccupiedbytheantrum.Adentigerouscystinvolvingamaxillarycuspidmaybedifficulttodifferentiatefromanenlargedfollicle;inthecaseofacyst,theoutlineiscircular,andalinearopacitycrossesthetooth.PrimordialCystsManyconsiderthatprimordialcystsarekeratocysts;however,certaincystsdevelopinplaceofatoothanddonotshowevidenceofkeratinizationoftheepitheliallining.Mostcommonly,themandibularthirdmolarregionisthesite.Occasionally,theyarefound':inbicuspidandmaxillarythirdmolarareas.Atoothisabsent.Thereisaradioluencynotquiteasregularinoutlineasadentalcyst.Thecortexmaybesomewhattenuous.Whenthecystislarge,ittendstospreadalongtheboneandthereisanappearanceofsegmentation.KeratocystsKeratocystsdevelopfromcellsoriginatingfromthedentallamina,Theepithelialliningkeratinizes,andsometimesthecystcavityisfilledwithshedkeratinizedepithelium.Themethodofenlargementisthoughttobemostlybyproliferationofthelining,andtheosmoticgradientislessofafactorthaninthecaseofdentalcysts.Thereisatendencyforthiscysttoextendalongtheboneratherthantoexpanditlaterally.Keratocystscanrecuraftersurgicalremoval.Aradioluencylesscircularthaninthecaseofadentalcystandsometimesovalshaped.Thecortexisnoticeablythickinsomeorallofitsextent.Often,loculationsare'present.Thereislimitedlateralexpansion.Sometimes,thelesionextendsuptheramus.Inthemandible,theinferiormarginmaybeirregular.Keratocystscanbesingleormultiple.Whenmultipletheyareusuallypartofthebasalcellnervikeratocystsyndrome(Gorlin'ssyndrome).MultipleCystsMultipledentalcysts,multipledentigerouscysts,multiplekeratocysts.EruptionCystsEruptioncystscanbeconsideredasasubclassofdentigerouscysts.Theydevelopcoronallyoftheocclusalsurfacesandareusuallypartlyinboneandpartlyinsofttissue.Asmoothconcavityonthesurfaceofthebonearoundthecrownofaneruptiontoothcanbeseen.Smoothenlargementofsofttissuemaybevisible.CalcifyingOdontogenicCystThisveryrarelesionisseenasafairlycircularradioluencywithdefinitemargins,containingsmallradiopaquemasses.VOCABULARYl.genialtubercle額棘2.mentalforamen額孔3.radilolucency放射線透過性4.radiopacity射線不透性5.inferiordentalcanal下齒槽神經(jīng)管6.mylohyoidridge頜舌線，也稱內(nèi)斜線或下頜舌骨線7.externalobliqueridge外斜線8.sigmoidnotch乙狀切跡9.coronoidprocess喙突10.condyle髁狀突11.Stafnecavity史蒂芬骨腔12.laminadura骨硬板13.anteriornasalspine前鼻棘14.intermaxillarysuture腭中縫15.nasalseptum鼻中隔16.nasalairways鼻腔17.incisivecanal切牙管18.caninefossa尖牙窩(凹)19.zygomaticbone顴骨20.tuberositv粗隆(直譯)，這里指上頜結(jié)節(jié)21.hamularprocess翼突22.nasolacrimalduct鼻淚管23.antrum竇(直譯)課文中指上領(lǐng)竇24.dental(radicular)cyst相尖囊腫25.lateralperiodontalcyst牙周側(cè)囊