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Apical limit of root canal instrumentation and obturation,part 2. A histological studyD. RI CUCCIa&K. L ANGE L ANDbaPrivate practice, Cetraro (CS), Italy;bDepartment of Restorative Dentistry and Endodontology, School of Dental Medicine,University of Connecticut, CT, USASummaryTheresults of aninvivohistological studyinvolvingapical and periapical tissues following root canaltherapy after different observation periodsdemonstrated the most favourable histologicalconditions whentheinstrumentationandobturationremainedat or short of theapical constriction. Thiswasthecaseinthepresenceofvitalornecroticpulps,alsowhenbacteriahadpenetratedtheforamenandwerepresent in the periapicaltissues.When thesealerand/or the gutta-percha was extruded into theperiapical tissue, the lateral canals and the apicalramifications, therewasalwaysasevereinflammatoryreactionincluding a foreignbody reactiondespite aclinical absence of pain.Keywords: apical limit, rootcanal instrumentation/obturation, tissue reactions.IntroductionThefirstscientificbasisformodernclinicalEndodontologywas established by Davis (1922). He was the first tosuggest that careful treatment of theapical tissuewas arequirement for success in root canal treatment.Since thenmanyhistological studies, basedonapicalbiopsies including the surrounding periapical tissues, orendodontically treated teeth which were extracted atvaryingperiods oftime,confirmed hisobservation(Hattonetal. 1928, Blayney 1929, Nygaard-O/stby 193944,Laws 1962, Nyborg & Tullin 1965, Engstrom &Spa ngberg1967, Seltzeretal. 1968and1969). All thesestudies agreed that, in vital pulp treatment, partialpulpectomy was preferred to total pulp removal.Langeland(1957, 1967, 1976, 1981, 1987and1995),Linetal. (1984)describedindetail theprogressionof thepulpnecrosisanddemonstratedthatvitalpulptissuewithnervesandvesselsremaininthemost apical part of themain canal even in the presence of a large periapicallesion. Asalogical clinical consequenceof theseobserva-tions, they suggested terminating instrumentation andobturation at the apical constriction, just short of theradiographic apex, eveninthe presence of a periapicallesion. Theyalsoconcludedthat, intime, all pulptissuewill beinvolvedbynecrosis, finallyincludingapical tissueandthetissuecontainedintheramifications,andbacteriawill establishthemselvesintheperiapical lesionasfarasthe necrosis occurs (Pasconetal. 1987, Oguntebi etal.1982,Linetal.1996).Eveninthisextremesituation,themost appropriate level in limiting the endodonticoperationis still theapical constriction: thearealocatedinside the root canal (Langeland 1995).Thepurposeofthepresentstudywastoinvestigatethehistopathologicalresponseoftheintracanalpulptissue,ofthepulptissuecontainedinthelateral canals, theapicalramifications, and of periapical tissues to endodonticprocedureswhenperformedshortof orbeyondtheapicalconstriction, in both vital and necrotic pulp conditions.Materials and methodsTheexperimentalmaterialconsistedof41humanteeth,atotalof49roots,obtainedfrom36patients(14males,22females) aged 1665years. All human subjects who parti-cipated in the experimental investigation gave theirinformedconsent after the nature of the procedure andpossible discomforts and risks had been fully explained(Table1).Ten of these cases (nine teeth) came from a previous in-vestigation(Ricucci etal. 1990) consistingof biopsies ofthe apex and periapical bone following instrumentationandCa(OH)2medication(cases110).Nineteenteethhadbeen exposed to cariesand/or operative damage, requiringendodontic treatment for pulpal/periapical involvement(cases 1129).394 q1998BlackwellScienceLtdInternational Endodontic Journal (1998) 31, 394409Correspondence: Dr Domenico Ricucci Piazza Calvario 7, I-87022Cetraro (CS), Italy (e-mail:[email protected]).Table1CaseNumberPatientSexAge&Tooth/RootPathologyDiagnosisP.a.lesionMedicationDurationmedication(days)ProceduresApicallevelprocedures(mmfromrad.apex)Obser-vationperiodP.a.lesionatthemomentofthebiopsyClinical/radio-logicalevaluationofthetreatmentBiopsy1APM1814/PalatalrootNoneVitalNoCa(OH)27Instrumentationonly1:57daysNo--Extraction2APM1814/BuccalrootNoneVitalNoCa(OH)27Instrumentationonly1:57daysNo--Apical/P.a.biopsy3GVM4812FractureNecroticYesCa(OH)215Instrumentationonly115daysYes--Apical/P.a.biopsy4RMF1814/BuccalrootCariesNecroticNoCa(OH)235Instrumentationonly135daysNo--Apical/P.a.biopsy5MSF5711CariesNecroticYesCa(OH)27Instrumentationonly1:57daysYes--ApicalP.a.biopsy6AIRM5412Iatrogenesis(prostheticpreparation)NectroticYesCa(OH)215Instrumentationonly1:515daysYes--Apical/P.a.biopsy7PSF5511CariesVitalYesCa(OH)214Instrumentationonly114daysYes--Apical/P.a.biopsy8PSF5521CariesVitalNoCa(OH)214Instrumentationonly114daysNo--Apical/P.a.biopsy9SCF3421CariesVitalNoCa(OH)221Instrumentationonly1:521daysNo--Apical/P.a.biopsy10ERM1911NoneVitalNoCa(OH)282Instrumentationonly1:582daysNo--Apical/P.a.biopsy11EAF3011CariesVitalNoCresatin7Instrumentationonly1:57daysNo--Apical/P.a.biopsy12FRM1912Iatrogenesis(pulpcapping)NecroticYesCa(OH)227Completeendotreatment1:548daysYes--Apical/P.a.biopsy13PAM2211CariesNecroticYesCa(OH)27Completeendotreatment1:548daysYes--Apical/P.a.biopsy14MTSF1821Iatrogenesis(Pulpcapping)NecroticYesNo--Completeendotreatment1:53yearsNoSuccessfulApical/P.a.biopsy15MIF2312CariesNecroticYesNo--CompleteendotreatmentBeyondapex6yearsYesDoubtfulApical/P.a.biopsy16SPF2414/BuccalrootCariesNecroticYesCa(OH)220Completeendotreatment25monthsYesDoubtfulApical/P.a.biopsy17SAF4422CariesNecroticYesCresatin7CompleteendotreatmentBeyondapex13monthsYesDoubtfulApical/P.a.biopsy18LAM3721CariesVitalNoNo--CompleteendotreatmentBeyondapex4monthsYesFailureApical/P.a.biopsyRTC instrumentation and obturation 395q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409Table1Continued.CaseNumberPatientSexAge&Tooth/RootPathologyDiagnosisP.a.lesionMedicationDurationmedication(days)ProceduresApicallevelprocedures(mmfromrad.apex)Obser-vationperiodP.a.lesionatthemomentofthebiopsyClinical/radio-logicalevaluationofthetreatmentBiopsy19EPM3122CariesVitalNoNo--Completeendotreatment1:582daysNo--Apical/P.a.biopsy20EPM3124/BuccalrootCariesVitalNoNo--Completeendotreatment1:562daysNo--Apical/P.a.biopsy21FMM4222CariesNecroticYesCa(OH)210Completeendotreatment1:518daysYes--Apical/P.a.biopsy22DOF2321ExternalrootresorptionVitalNoCa(OH)27Completeendotreatment1&1yearYesFailureApical/P.a.biopsy23RSM3944CariesNecroticYesCa(OH)27Completeendotreatment14monthsYes--Apical/P.a.biopsy24GCF2023CariesNecroticYesNo--Completeendotreatment11yearYesFailureApical/P.a.biopsy25GSM2211CariesNecroticYesNo--Completeendotreatment14yearsYesFailureApical/P.a.biopsy26MGF1822CariesNecroticYesNo--Completeendotreatment0:54yearsYesFailureApical/P.a.biopsy27VVM6221CariesNecroticYesCa(OH)221Completeendotreatment140daysYes--Apical/P.a.biopsy28LVM6512CariesNecroticYesCa(OH)214Completeendotreatment135daysYes--Apical/P.a.biopsy29SZF2121CariesNecroticNoCresatin7Completeendotreatment1:510yearsand8monthsYesFailureApical/P.a.biopsy30MIM2535CariesVitalNoNo--Completeendotreatment26yearsNoSuccessfulExtraction31MFF4312CariesVitalNoNo--Completeendotreatment22yearsNoSuccessfulExtraction32ACF3127/mesialrootCariesVitalNoCresatin7Completeendotreatment1:55yearsNoSuccessfulExtraction33ACF3127/palatalrootCariesVitalNoCresatin7Completeendotreatment25yearsNoSuccessfulExtraction34ACF3127/distalrootCariesVitalNoCresatin7Completeendotreatment25yearsNoSuccessfulExtraction35APF4712Iatrogenesis(Prostheticpreparation)NecroticYesCa(OH)29Completeendotreatment13yearsNoSuccessfulExtraction36AMSF3915Iatrogenesis(Pulpcapping)NecroticYesCa(OH)217Completeendotreatment15monthsNoSuccessfulExtractionq 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409396 D. Ricucci & K. LangelandTable1Continued.CaseNumberPatientSexAge&Tooth/RootPathologyDiagnosisP.a.lesionMedicationDurationmedication(days)ProceduresApicallevelprocedures(mmfromrad.apex)Obser-vationperiodP.a.lesionatthemomentofthebiopsyClinical/radio-logicalevaluationofthetreatmentBiopsy37FLF1635CariesVitalYesNo--Completeendotreatment1:53yearsand1monthNoSuccessfulExtraction38ALF2646/mesialrootCariesVitalNoNo--Completeendotreatment1:57yearsand3monthsNoSuccessfulExtraction39ALF2646/distalrootCariesVitalNoNo--Completeendotreatment1:57yearsand3monthsNoSuccessfulExtraction40EPM2345CariesNecroticYesNo--CompleteendotreatmentBeyondapex6yearsand6monthsNoDoubtfulExtraction41GAF4523CariesVitalNoNo--Completeendotreatment25yearsand4monthsNoSuccessfulExtraction42AMF3126/mesialrootCariesVitalNoCa(OH)27CompleteendotreatmentBeyondapex3yearsand5monthsNoSuccessfulExtraction43AMF3126/palatalrootCariesVitalNoCa(OH)27Completeendotreatment1:53yearsand5monthsNoSuccessfulExtraction44AMF3126/distalrootCariesVitalNoCa(OH)27Completeendotreatment13yearsand5monthsNoSuccessfulExtraction45VVM6246/mesialrootCaries/PerioNecroticYesCresatin7Completeendotreatment1:57yearsNoSuccessfulExtraction46VVM6246/distalrootCaries/PerioNecroticYesCresatin7Completeendotreatment1:57yearsNoSuccessfulExtraction47VVM6236/mesialrootCariesNecroticYesCa(OH)27Completeendotreatment1:56yearsand7monthsNoSuccessfulExtraction48VVM6236/mesialrootCariesNecroticYesCa(OH)27Completeendotreatment0:56yearsand7monthsNoSuccessfulExtraction49APF5533Caries/PerioVitalNoCa(OH)27Completeendotreatment11yearNoSuccessfulExtraction&Theageofthepatientisintendedatthemomentoftheendodontictreatment.&Theobturationwas1mmshortoftheradiographicapex.Actually,inthehistologicsectionsitprotrudedintotheperiapicaltissuefromananticipatedforamen.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 397Endodontic therapy was performed by the sameoperator, using the same technique. In all casesprophylaxis, local anaesthesia, rubber damapplication,disinfectionof the fieldwith30%H2O2followedby5%tinctureof iodinewereperformed(Mo ller 1966). Duringinstrumentationcopiousamountsof1%NaOClwereusedfollowed by thorough aspiration. The canals wereobturatedwithlaterallycondensedcoldgutta-percha,andazincoxide-eugenol sealer(PulpCanal Sealer; KerrMan-ufacturing Co., Romulus, MI, USA).After observation periods varying from 18days to10years and 8months, during which recall follow-upradiographs were taken, biopsies of the apex withsurrounding periapical tissue were taken. After elevating aflap,acirculartrepanbur6mmindiameterrotatingatalow speed was used, to obtain a cylinderof bone includingthe root apex. The remaining sectioned surfaces weresmoothedandbevelled.Retrogradecavitieswerepreparedand filled with amalgam.Thirteen of the teeth (20 roots) were scheduled forextraction, for orthodontic or prosthetic reasons, orbecauseof longitudinal fractures, all followingendodontictherapy which included 1%NaOCl/Ca(OH)2irrigation/medicationandobturation(cases 3049) performedfivemonths to seven years and three months previously.In all cases the medical and dental history wererecorded, at least one diagnostic radiographwas takenand an initial diagnosis established on the basis of acombined clinical and radiographic examination.The teeth were grouped as those with a vital pulpwithoutbacterialcolonizationintherootcanal,andthosewith a necrotic pulp where bacterial colonization hadadvanced into the root canal regardless of how far(Langeland etal. 1976, Andersonetal. 1981, Linetal.1984, Langeland1987). Therationalefor this classifica-tion is that there is a distinct correlation between theclinicallyobservable conditionandthe histological facts.Clinically it was checked and recorded whether or nottherewascontinuous,bloodfilledpulptissueinthecanalorifice(s), whichconstitutedabasis for one-visit therapy.Accordingtothisclassification, governedbymicrobiologi-cal factsregardlessof thepresence/absenceofaperiapicallesion, 24cases wereclassifiedas `cases withvital pulp'and25as `cases withnecrotic pulp'. The latter twoormore visits were considered mandatory, with Ca(OH)2used as an intracanal medicament (Table1).The specimens were immediately immersed ina 10%neutral buffered formalin solution. Radiographs at rightanglestothelongaxisof theroot andphotographsweretakenof all specimens after fixation. Thespecimens wereshipped in fixative to the University of Connecticut for histo-logical processing and evaluation. Serial sections 5 mm thickwere cut and stained alternately with hematoxylin andeosin, Masson's trichrome, or Brown-Brenn techniques.Special care was taken to obtain and locate the sections thatincluded material/tissue contact and the apical foramen(ina)in direct continuation with the periapical tissues.ResultsObservationsIn allcasesremnantsof pulp tissue anddentine chipsoftenintermixedwithsealerwerefoundatdifferentlevelsintheroot canals. Theaccidental presenceof pulpal debris anddentine chips was mainly limited to the pulp wound surface(Fig.1b,c;5c,d),butinsomecaseschipsanddebrisweredisplaced into the apical and periapical tissue.Cases with procedures limited within the canalIn43of the49rootstheprocedureswerelimitedwithintheapical constriction. In10of theseroots onlyinstru-mentationandCa(OH)2medicationhadbeenundertaken,and in one case instrumentation followed by Cresatinmedication.Inthreecasesofthisgroupwhichexhibitedaperiapical radiolucencypriortothetreatment (cases3, 5and6),periapicallesionswerefoundhistologically,withadense concentration of both chronic inflammatory(plasma cells, macrophages, mast cells, lymphocytes,foreignbodycells) andacuteinflammatorycells(neutro-philicleucocytes). Incase7avital pulpstumpwasfoundwithamoderate concentrationof inflammatorycells, incontinuation with the periapical lesion.In the remaining seven cases of this group withoutobturation, in which no periapical radiolucency waspresentpriortothetreatment(cases1,2,4,and811),avital pulpstumpwas observedshowingdifferingdegreesof chronicinflammation. Chronicinflammatorycellswerealsopresentintheperiapical tissueinfourcases(4, 8, 9and11). Inthreecases(1, 2and10) inflammationwasconfinedtothe apical pulpstump, inthe presence of ahealthy periodontal ligament (Fig.1c).Inthegroupwithrootcanalobturation,19caseswereclinicallyclassifiedassuccessful(cases14,3039,41and4349). These showed a vital pulp stump with chronic in-flammatory cells. A healthy periodontal ligament wasobserved incase 14(Fig.7c). Fragments of periodontalligamentattachedtotheextractedrootswerefound, freeof inflammation (in cases 30, 31 and 37) (Fig.4e; 8c).Differing degrees of inflammation were present in theapical and periapical tissues (cases 12, 13, 16, 19, 20, 21, 23,q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409398 D. Ricucci & K. LangelandFig.1Case10(Table1). (a) A19-year-oldmale. Tooth11hadtwocompositerestorations withnoapparent cement or basemesially.Nowideningof periodontal/periapical space. Lagtimenot known. Asymptomatic: thepulprespondedwithinnormal limits tosensitivitytests(cold, hot, electric). Thecanal wasinstrumentedtoapproximately1.5mmfromtheradiographicapex, uptoasize60K-file. Attheendof theinstrumentationthecanal wasrinsedwithsterilesaline, driedandfilledwithCa(OH)2. After84daysduringwhichnopost-operativesymptoms werepresent thecanal was reopened, washed, driedandleft empty; asterilecottonpellet was put intothepulpchamberandatemporaryfillinginserted. Aflapwaselevatedandabiopsyof theapexwithperiapical tissuetaken. (b)Roottipincludingapical foramen. 1.1mmof pulptissueremainsshort of theapical constriction. Foramenopensbeyondtheapical constriction. Apart fromsmall irregularities, thecanal wall isclean. Minoraccumulationof debrisonthewoundsurface. H&E; (12). (c) Debrisonthewoundsurface, scattered chronic inflammatory cells below. H&E; 200. (d) Healthy pulp tissue fromaround the apical constrictionwithfibroblastsandafewscatteredinflammatorycells. H&E; 500.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 39927 and 28) which could not be clinically classified as successor failure because the observation periods were too short.Calcificationswerepresentinthemostapical partof thecanal (cases14, 30, 35, 38and39) narrowingthecanallumenbutinnocasewastheretotal closure. Thispheno-menon coexisted with an inflamed pulp stump (Fig.7c, d).Incases2426and29classifiedasfailuressevereinflammatory reactions were observed in the periapicaltissues. Inall cases bacteriawereidentifiedinthedebrispresent inthe apical part of the canal and inadjacentdentinal tubules.Incase24fooddebriswasnoted,whichwashistologicallyidentifiedasvegetablematerial,infectedbybacterial coloniesinthemostapical partof thecanal,whichhadbeenleft exposedtotheoral environmentforalong period (Fig.5c, d).Cases with overfillingOverfillingwaspresent insixcases(15, 17,18,22,40and42). In one of these (case 22), with the obturation seeminglyending short of the apex radiographically, histologicallyshowed termination on the buccal aspect of the root, severalmillimetres short of the anatomical apex (Fig.6c, d)).In all cases severe inflammatory reactions wereobservedintheperiapical tissues. Periapical necrosisandinflammation were present near the extruded sealer(Fig.3c, d; 6d).Painwasnotpresentinanyof thecases, andincases15and17therewasaconsiderablereductioninsizeofaprevious periapical lesion (Fig.3a, b).Cases with healed lesionsIn eight cases with previous periapical radiolucencies,apparently healed at successive follow-ups, a vital pulpstumpwaspresent inthehistological sections(cases 14,3537 and 4548) (Fig.4d, e; 7c, d).Specimens taken with periapical lesionsIn 16 cases periapical biopsies were performed in thepresenceof radiolucencies. Insixof thesevital pulptissuewas foundcoexistingwiththeperiradicular lesion(cases6, 7, 16, 21, 22and 28). Inthe other 10specimens,necrotictissuewas foundinthemost apical part of thecanal, bordered towards the periodontal ligament by aFig.2Case2(Table1). (a)A18-year-oldmale. Thefirstupperpremolarwasscheduledforextractionfororthodonticreasons. Itwascariesfreewithasupposedly healthyanduninflamedpulptissue.Treatmentasforcase10.Workinglengthatabout1.5mmfromtheapex.Ca(OH)2mixedwithsterilesalineusedasintracanal dressing.After1weekaflapwaselevatedandabiopsytaken, includingthebonewiththebuccalroottip. Immediatelyafter, thetoothwasextracted. (b)Buccal roottipwithPDLandperiapical bone. Mainforamenshortof theapex. Apicalramification (arrow). There is another lateral canal a short distance away from the main canal. H & E; 15.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409400 D. Ricucci & K. Langelanddenseconcentrationofneutrophilicleucocytes(cases3,5,12, 13, 2327 and 29) (Fig.5c).DiscussionDespite careful preparation of optimal access andmeticulous root canal cleaningandshaping, inall casesremnants of pulp tissue and dentine chips, oftenintermixedwithsealer, were foundat different levels oftheroot canals. Theaccidental presenceof pulpal debrisanddentinechipswaslimitedmainlytothepulpwoundsurface,butinsomecaseschipsanddebrisweredisplacedinto the apical and periapical tissue. This confirmedpreviousobservationsindicatingthatacertainamountofdebris may remain in the canal, regardless of thetechniqueemployed (Turek&Langeland1982,LangelandFig.3Case15(Table1). (a) A22-year-oldfemale. Tooth22. Spontaneousflare-upwithpain, swellinginthesoft tissuesandanelevatedtemperature. Incisionanddrainageundertakenandsystemicantibioticsprescribedfor1week. Returnedafter2weekswithout symptoms.Sensitivity tests were negative but the tooth was slightly tender to percussion. The tooth was root canal treated. The post-operativeradiograph showed a large periapical lesion and that the canal had been obturated beyond the foramen, into the periapical tissues,includingalateral canal. (b) At a6-yearfollow-upnopost-operativesymptomswerefound. Therewasnospontaneouspainandnopaintopercussionor palpation. The radiographshowedregenerationof the periapical bone but aradiolucencyremainedaroundthe excessmaterial. The lateral canal was no longer distinguishable. (c) A5.5mmspecimen; root canal with remaining filling material, excessmaterial apicallyandadjacent inflammatorytissuearoundapparent emptyspace. H&E; 12. (d) Fromtheareaof radiolucencyaroundtheexcessmaterial, denseconcentrationof sealerparticlescanbeseenborderedbyfibroustissue, withchronicinflammatorycellsbeyond.Amongstthesealerparticlesthereisdisintegratingperiapical tissuewithremaininglobesof nuclei of neutrophilicleucocytes. H&E; 48.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 401etal. 1985, Pascon etal. 1991). Root canal anatomy(straight, curved or ramified) and pathosis (resorption/apposition) weremoreimportant fortheconsequencesofdebridementthananyparticularmethodofinstrumentingthe canal (Langeland etal. 1985, Pascon etal. 1991).Therecommendationfortheterminationat theapicalconstrictionis basedonsoundwoundhealingprinciples:the severance of the tissue inthat area will create thesmallestpossiblewound: thelesstissuetoheal thebetterthe cure.The patency technique as advocated by Buchanan(1989) violatesthiscure. `Patency' means theuseof `asmall flexible K-file whichwill passively move throughthe apical constricture without widening it'. This is aFig.4Case37(Table1). (a)A16-year-oldfemale. Tooth35hadspontaneouspainwithlargedistal cariouscavity. Thetoothwastendertopercussion, with an exaggerated response to tests (hot, cold, electric). The radiograph shows a deep carious lesion close to the pulp chamber and asmall radiolucencyonthemesial aspect of theroot. Thediagnosis was irreversiblepulpitis andorthograderoutineroot canal treatment wasperformed. (b) Laterally condensed gutta-percha and a zinc oxide-eugenol sealer, terminating 1mm from the radiographic apex. Sealer in a lateralcanal.(c)At3-yearsand1-monthfollow-up. Thesealerinthelateral canalisnolongervisible, andthelesionhaddisappeared.Thetoothwascomfortable and not tender to percussion. The case was recorded as success. The tooth was extracted for orthodontic reasons. (d) Root tip with maincanal just short of theapex, andalateral canal terminating2.1mmshort of theapex. The lateral canal contains sealer. H&E; originalmagnification 25. (e) Apical area with some attached periapical tissue. No inflammation in apical part of main canal and no inflammation in theperiapical tissue. H & E; 155. (f) Termination of lateral canal. Accumulations of sealer squeezed into the pulpal tissue of the lateral canal. An areaof necrosis between the two accumulations of the sealer, and a number of inflammatory cells can be seen. H & E; 155.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409402 D. Ricucci & K. Langelandtotal misconception of the problem. Moving a filethrough the foramen means cutting into undisturbedtissue (Fig.1b; 2b) and causing a larger wound.Nygaard-O/stby (1939 and 1944) stated that a betterprognosis was obtained when that tissue was leftundisturbed in vital cases, and Langeland (1987) hasrepeatedly demonstrated that undisturbed anduninflamed tissue also occurs in cases where there isnecrosis in the canals. It is unfortunate that manyAmericanendodonticschoolsdisregardthehistopatholo-gical factsand50%teachsomeformof patencyintheirgraduate or undergraduate programs. However, onlythree schools requireinstrumentationandfillingtotheradiographicapex(Cailleteau&Mullaney1997).Theirrigantusedinthepresentstudy(1%NaOCl)waschosen because this concentration produces the lowestpossibletoxicitycombinedwiththehighest possiblebac-tericidal effect (Spangberg etal. 1973).The medicament used, Ca(OH)2, was chosenbecause,despite its low solubility the Ca(OH)2 ions raise the pH suf-ficientlytokill bacteria, andthelargeamountof Ca(OH)2can be packed into the root canal with little risk ofperiapical irritationover alongperiod(Safavi &Nichols1993). The initial highpHof the Ca(OH)2is obviouslyFig.5Case24(Table1).(a)A20year-old-female,tooth23.Theclinicalcrownwasdestroyedtotallybycaries.Smallperiapicalradiolucencybut no clinical symptoms. Root canal treatment performed inone visit. (b) At 1-year follow-up the toothwas tender to percussionandpalpation.Theradiographshowedaperiapicalradiolucency.Thecasewasdiagnosedasafailureandanapicectomyperformed.(c)Partofroottipandcanal. Incoronal partof thecanal thereisdebrismixedwithsealerandintheforamenforeignmaterial ispresent. Largevegetal cellsborderedapicallybyanaccumulationofneutrophilicleucocytesarepresent.H&E; 45.(d)Bacterialcoloniesinthevegetablecells.Brown&Brenn; 450.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 403Fig.6Case 22 (Table1). (a) A23-year-old female, tooth 21. Adiagnosis of irreversible pulpitis was made and root canal treatmentundertaken.Inthepost-operativeradiographtheobturationdeviateddistallybutitseemedlimitedtothecanal.Noperiapicalradiolucencywaspresent. (b)At 1-year follow-up a radiolucency wasevident andthe toothwas tender to percussion. The casewas diagnosed asa failure andanapicectomy performed. (c) Section of root bucco-lingually. Obturation material protruding into the periodontal ligament through the foramen onthe buccal aspect of the root. H& E; 12. (d)From the area indicated by the arrow (in Fig.6c),an area of resorption filled with inflamed tissueand resorbing cells, sealer particles in the most apical area. H & E; 400.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409404 D. Ricucci & K. LangelandFig.7Case14(Table1). (a) A18-year-oldfemale, tooth21. Spontaneouspainandpaintopercussion, withswellinginthevestibule. Thetoothhadtwocompositerestorationsanddidnotrespondtosensitivitytests.Asemergencytreatmentincisionanddrainageoftheabscesswasmade, followedaweeklaterbyrootcanal therapy. Instrumentationandobturationisabout1mmfromtheradiographicapex. (b) A3-yearfollow-upindicatedthecompleteradiographichealingofthebonewiththeimage ofacontinuouslaminaduraalong theentirerootsurface. Atthis time a biopsy was taken. (c) Apex with periapical tissue. Healthy periodontal ligament and trabecular periapical bone. Calcified tissue in thissection`obturated' theentirecanal lumen. Softtissuepresentcoronal tothe`obturation'. H&E; 15. (d) ThissectionwastakennumeroussectionsafterthatshowninFig.7c:tissuepenetratingtheapparent`obturation'(inFig.7c).Vessels,nerves,numerouscalcificationsandsealerparticles. H & E; 60.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 405partly responsible for the wound surface conditions(Fig.1b, c), butasCa(OH)2allegedlychangestoCaCO3itis nolonger irritant. Finally, the biological effect of LPSincluding toxicity, pyrogenicity and macrophageactivation is lost by the modification of the lipid Astructure by the calciumions (Safavi &Nichols 1993).Whereasirrigantsdiffuselayerforlayerintoandthroughthepulptissue,theconcentrationoftheirrigantisdilutedFig.8Case30(Table1).(a)A25-year-oldmale,tooth35.Irreversiblepulpitistreatedbyrootcanaltherapyinasinglevisit.Instrumentationandobturationabout1.5mmfromtheradiographicapexusingthecoldlateralcondensationtechnique. (b)After6yearsthepatientreturnedfollowingthe loss of the coronal restoration. There hadbeennosymptoms. The radiographshowedhealthyperiapical structures withanevidentlaminaduraalongtherootapex. Therefore, thecasewasrecordedasanendodonticsuccess. Alongitudinal fracturewasseenonthebuccal aspectof therootandthetoothwasextracted. (c) Roottipwithperiodontal ligamentfragmentsattached. Foramenshortof theapex(oblique arrow) and a lateral canal (vertical arrow). Sealer displaced in the canal. H &E; 13. (d)Uninflamed tissue inthe lateral canal. H &E;212.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409406 D. Ricucci & K. Langelandasitmixeswithtissuefluids. Itmustalsoberealisedthatthe fluids and even Ca(OH)2particles are transportedthrough vessels into the periapical tissues (Barnes &Langeland 1966).Thelongheraldedbeneficialeffectofterminationatthecemento/dentinejunctionis totallyirrelevant tohealing.First, thejunctionisnotwheremostpractitionersbelieveit is, infact it maybe3mmhigher inoneareaof thecanal thaninanother area, and secondly it cannot befound clinically in any case (Langeland 1995).The anatomical location of the apical constrictioncannot be clinically determined with accuracy. It hasbeenrecordedasfaras3.8mmfromtheanatomicalapexinoneSEMstudy(Gutierrez&Aguayo1995). Therefore,althoughclinically desirable, no average millimetre settingmaybemadetosecureacommonconstantdistancefromthe apical constriction to the anatomical apex andcertainlynotfromtheradiographicapex.Thisfactshouldberememberedwhendeterminingthelengthof therootcanal duringroot canal therapy. Ameasurement basedonroot lengthratherthancanal lengthwouldcarrythefillingbeyondtheapical foramenandintotheperiapicaltissue (Fig.6c, d). Only the radiograph together withanatomical knowledge, tactile sense,and keen observationfor tissue fluids and blood on instruments and paperpoints will helpmodifyingthedistance. Thus, the1mmdistanceof theobturationfromtheradiographicapexsetbyStrindberg(1956)asthestandardforultimatesuccessis erroneous. Biologically and logically, according to allprinciples of wound healing, the best healing conditionexists wherethewoundis smallest, andsincetheapicalforamenis, moreoftenthannot, morethan1mmshortof theradiographicapex, obturations 1mmshort of theradiographic apex are in fact in the periapical tissuecreating a larger wound (Ricucci etal. 1990). At thislevel, sealers and gutta-percha will cause tissuedestruction, and inflammation, and a foreign bodyreaction, contrary to that which occurs when theobturationterminates at the apical constriction. This isclearlydemonstratedfrequentlywherethereisanobliqueapex and the filling radiographically ends short ononesideandisover-extendedontheoppositesideof theapex(Fig.6ad). The severe periapical tissue reaction isobviousintheabsenceof bacteria(Fig.3c, d; 6c, d). Themore tissue destructionthat takes place, the more timerequired for healing. The fact is that in none of thesuccess/failure studies has the ever-changing, non-measurabledistance, betweentheradiographicapexandthe apical constriction been taken into consideration.Langeland (1957, 1967, 1987 and 1995) alone hasstatedthat this canonlybemeasuredintheadequatelycut histological sectionandthatis the onlymethod whichallows a distinction between facts and speculation.Althoughcalcifications occur indeadanddyingtissue(Robbins1994a), natural closureof theforamendoesnotoccur.Thedepositionof calcified tissue into thepulp stumpcouldnotbeconsideredaphysiological processof healing.Hence, the histological condition of the pulp stumprepresented (in Fig.7c, d) even though the case wasclinicallysuccessful, couldnot beconsideredhistologicallyhealed because of the presence of inflammatory cellsincludingforeignbodycells andcalcifications, whicharealways indicativeof pathology.In general pathology calcifi-cation, except thedepositionof calciumsaltsduringboneturn-over, isdefinedas`thedepositionof calciumsalts indying or dead tissue' (Robbins 1994a.). In the caseillustrated(inFig. 7c,d),eveninthepresenceofahealthyperiodontium, the pulp stump was not histologically healed,because of the depositionof calcifiedtissue, suggestingametabolic disturbance. Terms like `biological closure' or`physiologicalclosure'donotappear correct, sincethey arephenomenawhichoccurinthepresenceof inflammation.Robbins (1994a) describes this under the heading`Pathologic calcification', be it dystrophic or metastatic.Theclaimeddescriptions of theapical total closurebycalcified tissue are causedby a misinterpretationof thehistological sections. Images like that of Fig.7c couldeasily be misinterpreted as total closure, whereas thepresence of soft tissue and circulation coronally to theplug is evidence that there is anopening. The openingwas found inthe successive sections (Fig.7c, d). For ahistologic study to be valid, serial section through theentire canal systemmust be cut. Any study based onrandomsectioningis`hitandmiss' andinvalid. However,in thisparticular casetheinflammationwaslimitedto thepulpstump, sincenomaterials hadbeenforcedintotheperiapical tissue, andit didnot interferewiththeregen-eration of a healthy periapical bone and periodontalligament.The filling beyond the apex is accompanied with thelowest prognosis. This is because the materials used are notbiocompatible. Whenever such materials are inserted orinjectedintothe connective tissue, tissue destruction, in-flammationandaforeignbodyreactionoccurs (Robbins1994). Undersuchcircumstancesclinical failurescouldbeobserved even in the absence of bacteria (Fig.3c, d; 6c, d).The lateral canals which have received increasedattentionrecentlyarenot relevant tothesuccessrateofendodontic therapy. Since they cannot be debrided(Fig.2b; 8c, d) neither mechanicallynor chemicallywhentheyappear filledradiographically(Fig.4b) this isbecause primarily sealer has been pushed into andq 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 407possiblythroughthem. Incontact withvital tissue thiswill cause tissue disintegration, inflammation and aforeignbody reactioninthe samewayas overfillingof themaincanal, onlyatareducedlevel, becausethereislessmaterial (Fig.4df).Finallyeveninthecasesinwhichnecrosisandbacteriawent beyond the foramen(ina) the apical limit of theprocedurewill betheapical constriction; oncetheoriginof the canal infectionis eliminated, the apical necroticpulpwill beremovedbytheperiodontal circulationandby a foreign body reaction.When cases fail this is because of failure to removebacterial disintegrationproducts fromtheapical spaceofthecanal(Fig.5c,d),orfailuretoavoidbacterialcontam-inationof theroot canal. Whenhealingof theperiapicallesionoccurs, thereisevidenceof eliminationof bacteria,cell walls of bacteria, and their disintegration products(Fig.7c, d).Whenalesionreappearsfollowingpartial healing, thereason is that bacteria that have been dormant or reducedinnumbers, re-establishthemselvesandgrowintherootcanal (Sundqvist 1992) or the bacterial disintegrationproducts, such as lipopolysaccharides, have not beeneliminated fully (Safavi & Nichols 1993, Safavi &Rossomando1991), orthecanal systemiscontaminatedby ingress of microorganisms coronally (Saunders &Saunders 1994).ConclusionsThebest prognosis for root canal treatment is: adequateinstrumentation and homogeneous obturation to theapical constriction. The worst prognosis for root canaltreatment is: instrumentation and filling beyond the apicalconstriction.The second worst prognosis is: obturationmore than2mmshort of the apical constriction, combined withpoor instrumentation and obturation. The distancebetweentheforamenandtheapical constrictionisoftenmore than 1mm, e.g. 3mm. Adequate radiographs,knowledge of anatomy, andtactilesense, andnot `apexlocators' will help to determine apical constriction.Lateral canalsand/orapicalramifications:(i)cannotbedebridedmechanicallyorchemically(ii)when`filled', theinjectedmaterial causestissuedestructionandinflamma-tion. Radiographicdemonstrationof themdoesnotmeanexcellence in endodontics.Since absence/presence of bacteria in one visitevaluationis onlyonealthoughimportant aspect ofmanyvariablesinprognosis, thetreatmentrecommenda-tion will need support of long term comparative studies.ReferencesANDERSONDM, LANGELANDK, CLARKGE, GALICHJW(1981)Diagnosticcriteriaforthetreatmentof caries-inducedpulpitis. Bethesda, MD,USA: Department of the Navy, Navy Dental ResearchInstitute,NDRI-PR 8103.BARNES GW, LANGELAND K(1966) Antibody formationin primatesfollowingintroductionof antigens intothe root canal. 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Acta Odontologica Scandinavica(Suppl.) 14, 21.SUNDQVIST G (1992) Association between microbial species indental RTCinfections. Oral MicrobiologyandImmunology7, 25762.TUREK T, LANGELAND K (1982) A light microscopic study of theefficacy of the telescopic and the Giromatic preparationof rootcanals. Journal of Endodontics 8, 43643.q 1998 Blackwell Science Ltd, International Endodontic Journal, 31, 394409RTC instrumentation and obturation 409


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