root canal anatomy.odt

8/11/2019 root canal anatomy.odt

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PRACTICE

IN BRIEF Emphasises the anatomy of molar teeth in relation to endodontic treatment. Discusses the assessment of teeth prior to commencin endodontic treatment. Descri!es common pro!lems encountered "hen preparin access ca#ities and ho" to

$ERIFIAB%ECPD PAPERo#ercome them.A practical uide to endodontic access ca#itypreparation in molar teeth&. Patel' and (. Rhodes)The main o!*ecti#e of access ca#ity preparation is to identify the root canal entrances for su!se+uentpreparation ando!turation of the root canal system. Access ca#ity preparation can !e one of the most challenin andfrustratin aspectsof endodontic treatment, !ut it is the -ey to successful treatment. Inade+uate access ca#ity preparationmay result in difficulty locatin or neotiatin the root canals. This may result in inade+uate cleanin, shapin andfillin of the root canalsystem. It may also contri!ute to instrument separation and a!errations of canal shape. These factorsmay ultimately leadto failure of treatment. ood access ca#ity desin and preparation is therefore imperati#e for +ualityendodontic treatment, pre#ention of iatroenic pro!lems, and pre#ention of endodontic failure /Fi. '0.The aim of this paper is to present a simple uide to preparin access ca#itiesin molar teeth, and ho" to identify anda#oid potential complications.The 1ideal2 access ca#ity fre+uentlydescri!ed in endodontic te3t!oo-susually sho" easily identifia!le canalentrances at the !ase of a lare pulpfloor /Fi. )0. In the past, access ca#itiestended to !e standardised dependin ontooth type, ho"e#er "ith modern endodontic techni+ues, a dental operatinmicroscope and loupes pro#idin manification and !etter illumination, anaccess ca#ity is no" mostly dictated !ythe indi#idual pulp cham!er morpholoy of the tooth !ein treated.Access ca#ity preparation may !edi#ided into four staes4'5&pecialist Endodontist, 67 8impole &treet, %ondon,8' 9&B: )&pecialist Endodontist, '7 Penn ;ill A#enue,Par-stone, Poole, Dorset, B;'6


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Email4 shanonpatel>hotmail.comRefereed PaperAccepted '? @cto!er )?D@I4 '.'9!d*.).?9)British Dental (ournal ): )4 ''6

Pretreatment assessment Preparation of the tooth forendodontic treatment Remo#al of the roof of the pulpcham!er and coronal pulp tissue Creatin straiht line access.Pretreatment assessmentThe li-elihood of ainin ade+uateaccess for endodontic treatment should!e determined durin treatment plannin. If access to the tooth is difficulttreatment may !e compromised. Thisis li-ely to !e e#en more rele#ant "ithcomple3 retreatment procedures. @nceaccessi!ility has !een confirmed, it isnecessary to mentally #isualise the location of the pulp cham!er. The anulationand any rotation of the tooth or coronal restoration in relation to the rootsshould !e assessed as this "ill ha#e a!earin on the desin of the access ca#ity. The position of the cementoenamel*unction and furcation should also !enoted as these landmar-s help indicate the location of the le#el of the pulpfloor and the pro!a!le position of thecanal entrances.BRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' )A preoperati#e periapical radioraphof the tooth ta-en "ith a !eamaimin de#ice to ensure no imae distortion should !e studied, alon "ith anyrele#ant !ite"in radioraphs. In someinstances it may !e helpful to ta-e additional anled periapical radioraphs toFi. ' ood access ca#ity desin results inidentification and su!se+uent disinfection ando!turation of the entire root canal system' ) Nature Pu!lishin roupPRACTICEaFi. ) Access ca#ity of a lo"er first molar:


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note the three canal orifices are connected!y de#elopmental /dar-0 lines. These lines aresometimes referred to as the 1dentine map2!Fis 7ac /a0 Top to !ottom, standard pro!e,a D'? endodontic e3plorer and a lon shan-

small spooned e3ca#ator. /!0 @peratin dentalmicroscope "ith an o!ser#erscope for thedental assistant /lo!al &urical Corporation,&t. %ouis, =&A0. /c0 %oupes "ith a fi!re opticliht source /lo!al &urical Corporation,&t. %ouis, =&A0ca!Fis a! /a0 %o"er first molar "ith sinificantly reduced pulp cham!er heiht, pulpcalcifications and sins of canal sclerosis:this tooth "ill !e more challenin to access./!0 The canals in this upper first molar toothappear to !e completely sclerosedFi. 6 Pulp calcifications o!scurin thecanal orificesseparate the different roots "hich mayother"ise !e superimposed o#er eachother. From these radioraphs the position, siHe, depth and shape of the pulpcham!er, position of the pulp horns,num!er of roots and the deree of cur#ature can !e assessed.Careful assessment of pretreatmentradioraphs may indicate potentialchallenes to canal identification. %arepulp spaces and o!#iously patent canalentrances may !e common in younerpatients, !ut as teeth ae, secondary dentine is laid do"n resultin in a reductionin the pulp cham!er #olume, and siHe ofthe root canal lumen. This often resultsin the loss of helpful anatomical landmar-s and chanes in the shape of thepulp cham!er "hich "ill !e uni+ue toeach tooth.The dimensions of the pulp cham!erand location of the root canal entrances"ill also !e influenced !y the amountand position of tertiary dentine deposited as a specific response to caries, microlea-ae and tooth surface loss o#er


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the course of a tooth2s life /Fis a!0.These insults on the pulp may ha#e adramatic effect on the siHe and shape ofthe pulp cham!er. Canal entrances mayalso !ecome o!structed !y pulp stonesand other dystrophic calcifications,

resultin in the identification of the'6root canal entrances !ein more challenin /Fi. 60.Preparation of the tooth forendodontic treatmentA front surface mirror, D'? endodontic pro!e, lon shan- small e3ca#ator,manification and ood illuminationare essential for endodontic treatment/Fis 7ac0.Caries and failin restorations must!e completely remo#ed prior to preparin the access ca#ity. If at the pretreatment assessment stae there is any dou!treardin the restora!ility of the tooth,the e3istin restoration should !e completely remo#ed to confirm that thereis sufficient tooth su!stance remainin/Fis ?ae0. Remo#al of e3istin restorations may also re#eal hairline crac-son one or more a3ial "alls "hich couldinfluence the endodontic pronosis andthe desin of the future postendodonticrestoration /Fi. 0.=nsupported cusps should !e remo#edor protected !y placin an orthodontic!and around the tooth to pre#ent cuspfracture durin and immediately aftertreatment. In some cases, follo"indismantlin of the coronal restoration,it may !e necessary to place a pro#isional restoration to fi rstly aid ru!!erdam placement, and secondly createBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' ) ) Nature Pu!lishin roupPRACTICEaFi. Remo#in the entire restoration re#eals acrac- /red arro"0 and caries in the mesial !o3da!


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!eca reser#oir for irriant solution in theaccess ca#ity.Remo#al of the roof of the pulp cham!er

and coronal pulp tissueThe roof of the pulp cham!er should !epenetrated throuh the central portion ofthe cro"n, at a point "here the roof andfloor of the pulp cham!er are at the "idest: this commonly occurs at the point"here the pulp horn relatin to the larest canal is situated /for e3ample, palatalroot in ma3illary molars and distal canalof mandi!ular molars0. Tunsten car!ide!urs are ideal for cuttin throuh metal:ho"e#er, a diamond !ur should !e usedto map out the access in porcelain fusedto metal cro"ns !efore usin a tunstenFis ?ae /a0 8amey /Dentsply GailleferInstruments, Ballaiues, &"itHerland0 can !eused to atraumatically and +uic-ly remo#ecro"ns, /!0 a slot is prepared on the !uccalaspect *ust !elo" the fit surface of the occlusal aspect of this metalceramic cro"n. /c0The 8amey is inserted into the access holeand rotated, /d0 the cro"n comes off in onepiece. /e0 The e3istin restoration is remo#edto re#eal an unrestora!le tooth. If the toothhad !een restora!le the e3istin cro"n mayha#e !een used as a temporary cro"ncar!ide !ur to reduce the li-elihood ofporcelain fracture /Fi. 90. It is al"ays"ise to "arn the patient that the cro"nmay !e irre#ersi!ly damaed and mayneed replacement follo"in endodontic treatment. @nce the roof of the pulpcham!er has !een !reached, the !ur "illsuddenly drop into the pulp cham!erspace /Fis


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!een completely remo#ed, ie no dentineBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' )Fis 9 a! /a0 left to riht, M) round diamond!ur, tunsten car!ide fissure !ur, Endo J !ur,A33cess !ur and M) tunsten car!ide round!ur, the last t"o !urs /&y!ronEndo, @rane,

CA, =&A0 ha#e a loner shan- and allo" !etter#ision "hen used "ith manification. /!0 Closeup of the nonend cuttin EndoJ !ur /DentsplyGaillefer Instruments, Ballaiues, &"itHerland0ledeslips are present.Careful inspection of the pulp cham!er floor of molar teeth "ill re#eal su!tlechanes in the colour of the dentine "hichaid identification of the canal entrances/Fi. )0. Dar- de#elopmental lines may !eidentified lin-in canal entrances and thelocation of an undetected canal entrancemay !e indicated !y trac-in alon thede#elopmental line. The canal entrance"ill appear as a small area of "hiteopa+ue dentine aainst a !ac-roundof yello"rey secondary dentine. Thetiny canal entrance "ill feel stic-y "henpro!ed "ith a D'? endodontic pro!e.Creatin straiht line access@nce the canal entrance/s0 ha#e !een'7 ) Nature Pu!lishin roupPRACTICEcaa!dFis < ad /a, !0 The roof of the pulp cham!er has !een penetrated usin a tunsten car!ide !ur:/c0 an 1EndoJ2 !ur has !een used to completely remo#e the roof of the pulp cham!er. /d0 All canalsreadily identifia!leidentified it may !e necessary to refi nemodify the shape of the access ca#ityto allo" endodontic files to ha#e unimpeded /straiht line0 access into thecoronalthird of the root canal.&traiht line access "ill reduce theli-elihood of iatroenic pro!lems suchas Hips, el!o"s and ledes !ein created !y lare /and therefore infle3i!le0stainless steel files as they attempt tostraihten in cur#ed canals, and "ill


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also allo" easier insertion of rotaryinstruments durin preparation /Fis'ac0. &traiht line access is essential"hen usin nic-eltitanium instruments.Althouh these instruments are #eryfle3i!le, poor straiht line access may

result in the files2 distortion and e#entual separation due to cyclic fatiue/Fi. ''0.C@GG@N PR@B%EG&%imited access%imited mouth openin andor anunfa#oura!ly positioned tooth mayresult in difficulty to correctly alinthe handpiece alon the lon a3is ofthe tooth. E#en "hen the canals ha#e!een located another challene may !etheir neotiation.A "ellpositioned mouth prop and achildren2s fast handpiece "hich has asmaller head "ill sinificantly impro#eaccess and treatment. &tandard lenthfriction rip !urs may also !e shortened "ith a tunsten car!ide !ur !y 6 mm and used in com!ination "ith achildren2s head handpiece to i#e e#enreater access /Fi. ')0. Reducin theheiht of the !uccal cusp tips !y ) mmprior to accessin the pulp cham!er "illincrease the intercuspal distance andimpro#e the #isi!ility and accessi!ility.Full co#erae restorationsIt is not uncommon for molar teethre+uirin endodontic treatment to !ealready restored "ith cro"ns. 8ithoutade+uate manification and illumination the access ca#ity "ill !e nothinmore than a !lac- hole. &u!tle colourchanes of the dentine on the floor ofthe pulp cham!er and other anatomical sins indicatin the position of the'?!cFis ' ac /a0 Inade+uate straiht line accessresultin in the tip of the file attemptin tostraihten itself /red arro"0. /!0 Refinin theshape of the access ca#ity results in unimpeded, straiht line access into the root canal.


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/c0 The mesio!uccal corner of the accessca#ity has !een modified /red arro"0 to ensurestraiht line access into the mesio!uccal canalof this lo"er molarBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' ) ) Nature Pu!lishin roup

PRACTICEFi. '' &eparation of a nic-eltitanium rotaryinstrument due to inade+uate straiht lineaccess of the mesio!uccal in the upper leftfirst molaracFis ' ac /a0 The cro"n on this upper rihtmolar mas-s the true position of the tooth,upon remo#in the cro"n the actual positionof the tooth !ecomes e#ident. /!0 Failure toremo#e the cro"n "ould ha#e most pro!a!lyled to failure to locate all the root canals andperforation. /c0 Posto!turation radioraphFi. ') The handpiece /a$o ? Bellator+ue,a$o Dental m!;, Bi!erach, ermany0 onthe left has a smaller head, "hen used "ith ashortened !ur it ma-es accessin molar teetheasier on patients "ith restricted openincanal entrances "ill !e difficult to identify. This may further !e complicated !ythe cro"n mas-in the orientation ofthe tooth /Fis ' ac0. If the canals cannot !e identified it may !e necessary toremo#e the cro"n. Remo#in the cro"n"ill also reduce the li-elihood of remo#in sound dentine unnecessarily andalso reduce the chances of perforation.Calcifications "ithin the pulp cham!erThe cumulati#e effects of aein andthe conse+uences of restorati#e dentistry reduce the pulp cham!er #olumedue to the deposition of secondary dentine. %ocalised deposition of tertiarydentine as a specific response to caries, microlea-ae and tooth surfaceloss "ill also reduce the #olume of thepulp cham!er. The natural dome shapeof the pulp cham!er floor "ill !ecome!proressi#ely flatter "hich results in thecanals entrances !ecomin narro"erand thus harder to locate /Fi. '60.


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Tertiary dentine o#erlyin the canalentrances may !e differentiated fromphysioloical secondary dentine !y its"hiteropa+ue appearance comparedto the yello"rey colour of secondarydentine. %on shan- !urs or ultrasonic

tips should !e used "ith a entle !rushstro-e action to remo#e tertiary dentine.Pulp stones and calcifications are !estremo#ed "ith small lon shan- e3ca#ators or ultrasonic endodontic tips /Fis'7a!0. @nce the canal entrance has !eene3posed it "ill feel stic-y "hen pro!ed"ith a D'? pro!e.@ften it is prudent to ta-e a radioraphBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' )to confirm that the access ca#ity is !einprepared in the correct direction andsecondly to assess ho" much dentine has!een remo#ed. If necessary ru!!er damshould not !e applied until the canal/s0ha#e !een identified to ensure that accessca#ity preparation is follo"in the lona3is of the root/s0, and also reduce theli-elihood of perforatin the pulpal floor.@nce the canal entrance/s0 ha#e !eenlocated, ru!!er dam should !e applied.@nce a canal has !een identified "itha D'? pro!e, a small file /siHe ? or90 "ith lu!ricant /for e3ample lyde0KDentsply Gaillefer Instruments, Ballaiues, &"itHerlandL0 should ently!e used in a "atch "indin action toneotiate the canal entrance. It may !e' ) Nature Pu!lishin roupPRACTICEaFi. '6 The deposition of tertiary dentine hasresulted in the pulp floor and roof !ecomincloser. The mesial canals pro*ect distally in thecoronal aspect of the tooth /red arro"0. Dentine "ill need to !e remo#ed in order achie#estraiht line access /!lue arro"0necessary to precur#e small fi les toneotiate the canal. $arious manufacturers ha#e specifically desined hand fi lesto aid neotiation of sclerosed canals.Riid 1CPilot2 files /$D8 Endodontic


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&ynery, Gunich, ermany0 ha#e a cuttin tip and are ideal to ently neotiatesclerosed canals as they are less li-elyto distort or !uc-le compared to reularstainless steel files /Fi. '?0. If the canalis completely sclerosed for se#eral mil

limetres apical to the pulp floor, instruments should !e ad#anced raduallyand a confirmatory radioraph ta-en toascertain the orientation of the instrument "ithin the canal.GANDIB=%AR G@%AR TEET;First molarsGandi!ular molar teeth usually ha#et"o roots in "hich there are commonlythree or four root canals. The mesialroot almost al"ays has t"o mesialcanals /mesio!uccal and mesiolinual0lin-ed !y a de#elopmental roo#e.Appro3imately ?O of distal rootsha#e only one canal, and the remainin 6O ha#e t"o canals /disto!uccaland distolinual0.The canals are more readily accessi!le"hen the access ca#ity outline is rectanular or trapeHoid, dependin on thenum!er of canals present /Fis ' a!0.The mesio!uccal canal entrance is usually located under the mesio!uccal cusptip, and the mesiolinual canal "ill !ea!!Fis '7 a! /a0 %eft to riht, a B=C ' ultrasonic endodontic tip /&yronEndo, @rane, CA,=&A0, &tandard M6 rose head !ur and lonshan- M6 rose head !ur. The ultrasonic tip andthe lon shan- !ur are ideal for remo#in smallamounts of dentine from the floor of the pulpcham!er. /!0 =ltrasonic endodontic tip in useslihtly to the !uccal of the mesiolinual cusp tip. The mesial canals commonly cur#e distally, this may result inthe mesio!uccal canal !ein challenin to identify and neotiate as the canalfollo"s a mesial course coronally andthen chanes to a distal direction half tot"othirds of the "ay do"n the canal.Appro3imately 7O of mandi!ular


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molar teeth ha#e three mesial canals,the third mesial /middle mesial0 canal isusually located !et"een the mesio!uccal and mesiolinual canals /Fis '9ad0. This middle mesial canal is usuallylocated alon the de#elopmental roo#e

!et"een the mesio!uccal and mesiolinual canals.The distal canal/s0 are located *ust distal of the !uccal de#elopmental roo#e:the canal entrance is usually o#al inshape if there is only one canal present.If t"o canals are present then the canalentrances tend to !e rounder and are usually connected !y an isthmus. As "iththe mesial canals they tend to !e locatedan e+ual distance a"ay from the mesiodistal midline of the tooth. The distalcanal entrances tend to !e much closertoether than the mesial canal entrances,and once prepared may !e confluent. It is'9cFis '? ac /a0 &iHe 9 1CPilot2 file /top0, anda siHe ' &enseus Profinder stainless steel filesfor neotiatin sclerosed canals /!ottom0. /!08hite opa+ue tertiary dentine indicates canalorifice /red arro"0 /c0 M9 CPilot file is usedto ently neotiate the canal. Irriatin "ithsodium hypochlorite and ethylene diaminetetraacetic acid /EDTA0 "ill aid canal penetration and neotiationrarely necessary to e3tend the accessdistally !eyond the midline as the anulation of the distal root allo"s straihtline access.Appro3imately 7O of molar teeth ha#ea third /distolinual0 root. As "ell as!ein e#ident on a preoperati#e radioraph, careful "idenin /!uccolinually0 of the distal canal may re#eal asecond distal canal entrance.&econd molarsThe anatomy of second molar teeth #aries more than that of first molars, andthe incidence of t"o distal canals insecond mandi!ular molar teeth is lessthan in first molars. The pulp cham!er#olume and canal entrances are smaller


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than in fi rst molars.In a small proportion of mandi!ularsecond molar teeth the roots may !eBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' ) ) Nature Pu!lishin roupPRACTICE

fused resultin in one main Cshapedcanal /in cross section0 once preparationhas !een completed.GAI%%ARQ TEET;First molarsGa3illary molar teeth usually ha#ethree roots, "ith three or four canals.The palatal and disto!uccal roots eachha#e one canal. Appro3imately


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GB', !et"een the GB' entrance andthe palatal canal entrance. The canalentrance is usually co#ered "ith a rideof dentine "hich has to !e remo#ed!efore the GB) can !e identified. =ltrasonic tips andor small rose head !urs

/%N Burs0 are ideal to ently remo#ethis ride of dentine co#erin the GB)canal entrance. The GB) openin "illfeel stic-y "hen pro!ed "ith a D'?/Fis '< ae0.The GB) and to a lesser e3tent the GB'may !e challenin to instruments asthey are commonly cur#ed. &mall siHedfiles are re+uired to initially neotiatethese narro" and tortuous canals. Belo"a!Fis ' a! /a0 Access ca#ity and radioraph of a lo"er first molar tooth three canal orifices, notethat the mesio!uccal and mesiolinual canals are found appro3imately the same distance fromthe midline /mesial to distal0 of the tooth /yello" line0. /!0 Access ca#ity and radioraph of a lo"erfirst molar "ith four root canals, note that the !uccal and linual canals can !e found on eitherside of the mesial to distal midline /yello" line0 of the tooth. If an imainary line is *oined !et"eenthe !uccal and linual canal entrances /yello" dots0 it "ill intersect the mesialtodistal midlineat riht anles. The distal canal orifices are closer to the midline than their mesial counterpartsac!Fis '9 ad /a0 Giddle mesial canal on thede#elopmental roo#e !et"een the mesio!uccal and mesiolinual canals, /!0 M? fileis used to neotiate the middle mesial canal,/c0 posto!turation of three mesial and t"odistal canals, /d0 posto!turation radioraphBRITI&; DENTA% (@=RNA% $@%=GE ) N@. A= '' )d'< ) Nature Pu!lishin roupPRACTICEdaFi. ) The canal orifices in upper secondmolar teeth tend to !e closer toether!ean operator to identify the root canalsentrances in molar teeth, ho"e#er nothin can su!stitute the e3perience and-no"lede leaned from practice !oth in


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a clinical en#ironment and on e3tractedteeth. &uccessful access ca#ity preparation relies on a sound -no"lede of theinternal and e3ternal anatomy of teeth.The importance of ainin straihtline endodontic access cannot !e o#er

emphasised. =ltimately poor accessca#ity desin could lead to inade+uatecleanin, shapin and o!turation compromisin successful outcome.Than- you to @3ford =ni#ersity Press for Fis' a!, "hich are ta-en from Principles of endodontics !y Gichael Ganoue, &hanon Patel andRichard 8al-er, )7. Than-s also to Dr B. &.Chon for his help and ad#ice in the preparationof this article.cFis '< ae /a0 Three root canals ha#e !een identified and prepared in this ma3illary first molar,the second mesio!uccal /GB)0 canal is usually located "ithin ) mm of the first mesio!uccal, !et"een this canal and the palatal canal. /!0 A B=C ' ultrasonic endodontic tip is ideal toremo#e the lip of dentine that may !e co#erin this fourth root canal orifice, it may also !eused to ma-e a ') mm deep trouh !et"een the first mesiocanal and palatal canal e3posinthe entrance of the second mesio!uccal canal. /c0 An ? siHed file is ideal to e3plore the canal,note that the canal is entered from the distal aspect. /d0 All four canals ready to !e o!turated,/f0 post treatment radioraphFurther readin'.)..the canal entrance it is not uncommonfor the GB) to follo" a mesial direction"hich chanes to a distal direction half"ay do"n the canal.&econd molarsThe roots of second molars tend to !ecloser or e#en fused toether, hence thecanal entrances in second molar teethtend to !e located more closely to eachother /Fi. )0. It is not usual to fi ndall three or four root canal entranceslyin alon the same line !et"een themesio!uccal and palatal canals. Thefloor of the access ca#ity is also moredomedshaped.C@NC%=&I@NThe use of manification, illumination and specialised items of e+uipment/for e3ample, ultrasonic endodontictips0 reatly impro#es the a!ility of


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'66.7.?..ulid ( C, Peters D D. Incidence and confiuration

of canal systems in the mesio!uccal root of ma3illary first and second molars. ( Endod '

root canal anatomy.odt

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