下颌切牙根管形态：Mandibular Incisors

舌侧中空而平滑的下颌切牙是成人牙齿中最小的。

Narrowand flatinthe labial-lingual dimension,themandibularincisorsarethesmallesthumanadult teeth. Visibleradiographically from onlyone plane, they often appearmoreaccessiblethantheyreally are.The narrowlingualcrownoffersa limitedareafor access.Smaller fissurebursandno.2 roundburs cause less mutilationofcoronal dentition.Theaccesscavity shouldbe ovoid, with attentiongiventoalingualapproach.Frequentlythemandibular incisorshavetwo canals.Onestudy reported that 41.4%ofmandibularincisorsstudiedhadtwoseparate canals;of these, only 1.3%hadtwo separateforamina.The clinicianshould searchforthe second canalimmediatelyupon completingtheaccess cavity.Endodontic failuresinmandibularincisorsusually arisefrom uncleanedcanals,mostcommonly towardthe lingual. Accessmaybeextendedincisallywhenindicatedtopermitmaximum labiallingual freedom. Althoughlabial perforationsare common, theymaybeavoidediftheclinician remembers thatitisnearly impossibletoperforateina lingual directionbecauseof theburshank'scontactingtheincisaledge.Theribbon-shapedcanaliscommonenoughtobeconsiderednormaland demandsspecial attentionincleaningandshaping.Ribbon-shaped canalsinnarrow hourglass cross-sectionalanatomyinvite lateralperforation byendodontic filesandGates-Glidden drills. Minimal flaringand dowelspace preparationareindicatedto ensure againstripping through proximalrootwalls.Apicalcurvaturesandaccessorycanalsarecommoninmandibularincisors(BurnsRC,BuchananLS.ToothMorphologyandAccessOpenings.PartOne:TheArtofEndodonticsinPathwayofPulp,6thEd.p.152).。