GutmannEvidence-BasedEndodontics (2016) 1:4 Evidence-Based Endodontics DOI10.1186/s41121-016-0004-8 REVIEW Open Access Apical termination of root canal — procedures ambiguity or disambiguation? James L. Gutmann Abstract Theissuesofworkinglengthdetermination,itsapicalextent,andthepositionofthefinalrootcanalfillinghavebeen controversial,asdifferingpointsofviewhaveexistedbetweenthebiologicallybasedandclinicallybasedendodontic gurusregardingthisconceptfordecades.Coupledwiththefollowingissues,ithasbecomesomewhatofanempirical bastion for clinicians, especially those in the limelight or who use social media to augment their clinical prowess: (1) the variable anatomy of the root apex; (2) where to terminate canal enlarging and shaping apically; (3) status of the accessory communications apically; (4) size of the apical preparation; (5) ability to debride the apical extent of the root canal and remove both bacteria and biofilm; (6) response of the periapical tissues, when both vital andnecrotic,totheintracanalfillingmaterialsandtechniquesthatmayimpingeonthesetissues;and(7)long-term outcomesandassessmentsoftheproceduresrendered.Forpurposesofsuccinctness,theconceptofworkinglength, theapicalpositionofinstrumenttermination,andthepositionofthefinalfillingwillbeaddressedsimultaneouslyin thispaper. Beyond the apex—danger lurks Review Cravens JE. Immediate root filling. Trans Ill State Dent Codificationoftheprinciplesofrootcanalprocedures Soc—29th Annual Meeting,The Dental Review Co., HD Up until the First World Conference on Endodontics Justi &Son1893;45–59. was convened by Dr. Louis I. Grossman (Fig. 1) during the week of June 22, 1953 (Grossman 1953), multiple treatment parameters were being used daily by clinicians Introduction and different philosophies of treatment were being es- One could consider using a systematic review to try and poused in dental education around the world. Primarily, answer the controversial challenges cited in the abstract; teeth were being extracted as opposed to addressing the however, this approach would not work historically, and many challenges of root canal procedures due to the from a contemporary standpoint, so very few, if any, overwhelming impact of the focal infection theory, along published studies qualify to fit into the higher levels of with the apical anatomical challenges that had been the hierarchy of scientific evidence that the essential is- highlightedinthe firstpartofthe 20thcentury. sues would not be addressed (Gutmann & Solomon While not a recognized specialty of dentistry globally 2009). Therefore, a somewhat unorthodox approach to at that time, endodontics and the provision of root canal this concept has been chosen,one in which historical re- procedures had been advocated routinely in some, very flection and contemporary assessment will be used to limited, and visionary areas of dentistry, even with the compare and contrast philosophies that address the is- name of endodontia being proposed by Dr. H. B. John- sues of concern. The starting point will be the First ston and accepted by the community at large, including International Endodontic Conference that occurred in the American Association of Endodontists (Gutmann Philadelphia,PA,USA,in1953. 2008). However, this first world conference established some significant guidelines for clinical procedures based on historical documentation and treatment philosophy up to that point, both clinical and biological. It is here that this manuscript will begin to explore the issue of Correspondence:[email protected] working length in an attempt to clarify all aspects of the TexasA&MUniversityBaylorCollegeofDentistry,Dallas,TX,USA ©2016TheAuthor(s).OpenAccessThisarticleisdistributedunderthetermsoftheCreativeCommonsAttribution4.0 InternationalLicense(http://creativecommons.org/licenses/by/4.0/),whichpermitsunrestricteduse,distribution,and reproductioninanymedium,providedyougiveappropriatecredittotheoriginalauthor(s)andthesource,providealinkto theCreativeCommonslicense,andindicateifchangesweremade. GutmannEvidence-BasedEndodontics (2016) 1:4 Page2of22 that had been smoldering through various levels of con- flagration since 1900 (Hunter 1900) but was brought to a crescendo by William Hunter’s (Fig. 2) diatribe against the dental profession during his classic presentation “An Address on the Role of Sepsis and Antisepsis in Medi- cine” that was delivered to the Faculty of Medicine of McGill University in Montreal in 1910 and published in 1911 (Hunter 1911). Advanced further by Billings (Bil- lings 1916) and Rosenow (Rosenow 1919), and perpetu- ated by others at that time (Grieves 1914a; Grieves 1914b; Grieves 1920), this concept impacted greatly on tooth retention. If tooth retention was deemed possible in the presence of a questionable pulp or a tooth with a periapical lesion, what treatment parameters may be considered as both acceptable and successful? Therefore, the issues addressed and the principles put forth from this conference had to be carefully analyzed and bio- logicallysound.To thatend,someofthefollowingques- tionscould beasked retrospectively: (cid:1) Historically,whatcontributed to thethinkingthat helped tosolidifytheseprinciples? Fig.1Dr.LouisGrossman—reproducedfromtheUniversityof (cid:1) Whatwasitaboutthebiology ofthe periapical Pennsylvania1943.(http://www.aae.org/welcome/0207pulp.html) tissuesand the clinicaltechniquesatthattimethat ledtothisdefinitive position? challenges involved in apical biology in relation to a pre- ferredterminationpoint forrootcanalprocedures. Whatweretheimportantoutcomesofthisfirst conference? While 21 principles of treatment parameters were forth- coming, two very specific guidelines emanated from the presentations and deliberations from a multitude of international experts, in particular Drs. Louis I. Gross- man, Lester B. Cahn, and Ralph Sommer from the USA, Dr. Francisco Pucci from Uruguay, Dr. Birger Nygaard Ostby from Norway, and Dr. George C. Hare from Canada.Thesetwo principleswereasfollows: 1. Traumaticinjurytothe surrounding(periapical)soft tissue shouldbeavoidedatalltimes. Tothisend, instrument stopsshouldbeused and instruments shouldbe confinedentirely within therootcanal (Grossman1953). 2. “…the canal fillingshouldsealthe apicalforamen, and thatiftheapicalmillimeterorso ofthe canal is filled withhealthylivingtissue, therootcanalfilling shouldterminateatthislevel ratherthan atthe apicalforamen”(Grossman1953). What was important at that time was the fact that Fig.2Dr.WilliamHunter—reproducedfromBremnerMDK.The StoryofDentistry,DentalItemsofInterestPublishingCo.,NewYork, dentistry and endodontics were still struggling with the vestiges of the “focal infection theory” (Grossman 1925) 1939.AlsofoundinDentCosmos1934;76(1):19 GutmannEvidence-BasedEndodontics (2016) 1:4 Page3of22 (cid:1) Wasthisapproachtomanagingthe apical portionof It shouldbeborneinmind,thatat thepointwhere theroot canal androot apextobethe sameinteeth the vesselsandnerves inquestion enter theroot,the withviableapicaltissues ornecrotic apicaltissues passageismuchsmallerthatitisimmediatelywithin. withor without theobviouspresenceofanapical Thisstrait (constriction) willbeeasily recognized rarefaction? whenreached,bythetouch,the instrumentappearing (cid:1) Wasthebestevidence availabletothe individuals in tobearrestedbyanobstacle, andnotbybeing thisconference?Whatroledidapicalresorption wedgedinanarrow passage.Careshouldbetaken, I playintheseguidelines,ifany? think,thattheinstrumentisnotallowedtopass (cid:1) Whatwasknown abouttheroot apexin1953that throughthestrait,eitherbybeingtoosmall orby wasnotknown in1911or before? beingrevolvedtheretillitcutsitsway through. For, (cid:1) Whatwasknown abouttreatmentoutcomes in1953 bywoundingthepartswithoutthetooth,andforcing relative tocurrent practicesatthattimeand particles of bone(dentin)out upon thepartsexternal previouspracticesthatmay haveimpactedontooth totheroots,thedangerofanunfavorableresult retention orsuccessfuloutcomes? would begreatly increased.(Harris 1855) Subsequently, EdmundNoyes ofChicago notedthat: Historicalgleanings A sense of respect for the apical constriction in the roots …thetreatmentofpulps wasnot seriously undertaken and the periapical tissues during root canal procedures bytheprofessionprevious to1865,andthatafter already appears in the mid-1800s, when Dr. Harwood of 1870theattemptstosaveteethwith exposed living Boston had communicated with Chapin Harris (Fig. 3), pulps,orwith deadpulps,becamequite common oneoftheco-foundersofthefirstdentalschool,theBalti- practice,themethodgenerallyemployedbeingthe moreCollegeofDentalSurgery,Baltimore,MD,USA,his removalofthe contentsofthe canalandplacing of considerationsintheoperationsofcleaningtherootcanal from onetomanytreatmentsofcreosoteoncotton, ofitspulptissue(Harris1855). mostoperatorsleavingsuchatreatment asaroot filling.(Noyes 1922) Little change in this philosophy existed until the late 1800s and the early 1900s, at which time the playing field was identified as being far more challenging due to studies on the root apex anatomy and apical root canal that proliferated at that time (Fischer 1909; Preiswerk 1912; Hess 1917; Grove 1916; Noyes 1921) (Fig. 4). First, recognizing the fact that there were significant apical ramifications led dentists to performing many proce- dures that only resulted in the removal of one half to two thirds of the dental pulp (partial pulpectomy) (Davis 1923); Itisourpracticeat thistime toamputate largepulps somewhere intheapicalthird oftheroot.With small canals,asinthebuccalrootsofuppermolarsandthe mesialrootsoflowermolars,we havebeen excising at the floorofthe chamber…(Davis1923); leaving challenges of the unpredictable apical anatomy to normal healing processes; or focusing on the use of substances such as arsenic to “sterilize” the retained ap- ical pulp tissue and kill bacteria or tannic acid to form an albuminate of tannin, which was insoluble and pre- vented tissue disintegration (Mills1897): Fig.3Dr. Chapin Harris—reproduced from Prinz H. Dental …wherewe cannot (reachthe apicalforamen), asin Chronology,Lea&Febiger,Philadelphia,1945 contracted ortortuousrootcanals,weforce tannic GutmannEvidence-BasedEndodontics (2016) 1:4 Page4of22 Fig.4aToothanatomydepictedbydyepenetration.FromtheworkofOskarKeller,AnatomiederWurzelkanäledesmenschlichenGebisses nachdemAufhellungsverfahren.Zürich,Buchdruckerei,Berichthaus.1928.KellerwasaprotégéofbDr.WalterHess—reproducedbypermission ofNicolaPerriniownerofthecollectionfromFondazioneCastagnolathatarefoundinStoriaanatomicadelsistemadeicanaliradicolari.Società ItalianadiEndodonzia,2010 acidsolution into theinaccessiblepulp tissues…we usedthetannicacidsolution because whenbrought into contact with anyremainingpulp tissues inthe rootcanal,itforms analbuminateoftannin; a compoundwhich isinsoluble inany ofthe fluids of the surroundingtissues,andconsequently no disintegration cantake placetocause any after trouble.(Mills1897) The challenging nature of the apical root anatomy was presented most vividly by Guido Fischer in 1907 (Fig. 5) when he started his large-scale research, with a new method in looking at human and animal root canals, paying special attention to their thin ramifications and apical terminations (Fischer 2010) (Fig. 6a–c). Fisher di- vided the different morphologic variations of the pulpal cavityinto: (cid:1) Simpleramifications orbranchesand lateralcanals withinthe radiculardentin (cid:1) Intercommunicatingcanal system (cid:1) Islandsof hardtissuewithin the canal These differentiations were named as bifurcations and ramifications, which created a complex system of apical morphology. With his method, Fisher established the accurate morphologic variations of a developing tooth, either in physiological or pathological conditions. He de- scribed very accurately the neoformation of dentin and Fig.5Dr.GuidoFischer—reproducedbypermissionofNicola pulpstoneswithintherootcanals.Furthermore,byassoci- PerriniownerofthecollectionfromFondazioneCastagnolathatare foundinStoriaanatomicadelsistemadeicanaliradicolari.Società ating macroscopic and microscopic observations, he ItalianadiEndotonzia,2010 showed how the root canal morphology is very complex GutmannEvidence-BasedEndodontics (2016) 1:4 Page5of22 Fig.6ApicalramificationsasdescribedbyG.Fischer:asecondpremolar,bfirstmaxillarymolar,csecondmaxillarymolar.BauundEntwicklung derMundhöhledesMenschenunterBerücksichtigungdervergleichendenAnatomiedesGebissesundmitEinschluβderspeziellenmikroskopischen Technik.Leipzig;VerlagvonDr.WernerKlinhardt,1909 due to the ramifications present, calling them lateral ca- in this portion of the canal, dentin should be formed by nals (Seitenkanal), and also apical ramifications called theodontoblastsinthepulp tissue.Ibelievethefact that regioramificatoria,whichisreferredtopresentlyasanap- this does not occur clearly indicates the erroneous char- ical delta. The complexity and inability to predict the acter of the theory that the pulp extends through the canalmorphologybroughthimtonamethewholesystem foramen.” (Grove 1916). It is here that this author asks astheradicularcanalsystem(Kanalsystem). oneofthemostcrucialquestionsthatthepresentmanu- Subsequently, there began a true appreciation for the script is attempting to address: “The question now con- nature of the tissue at the end of the root, as histological fronts us, What shall be done with these tissues when studies were able to demonstrate that the pulp tissue thepulp isdevitalized?”(Grove1916)(Fig. 7). ended at the dentinal-cemental junction and that there Key investigators, such as Noyes (Noyes 1922; Noyes were few if any incidences of pulp tissue going all the 1921), Grieves (Grieves 1915; Grieves 1919), Blayney way to the end of the root or to the extent of the major (Blayney 1927; Blayney 1922; Blayney 1926; Blayney 1940; foraminal opening (Grove 1916; Noyes 1921). The issue Blayney 1932; Blayney 1936; Blayney 1929a; Blayney nowwasthe clinicalmanagementofthese tissues. 1929b),Skillen(Skillen1922),Hatton(Hatton1922),Coo- According to C.J. Grove, “It should be remembered lidge (Coolidge 1921; Coolidge 1922), Groves (Grove that the apical foramen of fully developed teeth is 1921; Grove 1931),and Davis (Davis 1922a; Davis 1922b), formed bythe cementum. Ifthe pulp tissue werepresent recognized these anatomical challenges, including that of GutmannEvidence-BasedEndodontics (2016) 1:4 Page6of22 failure, while others had been in the mouth for a num- ber of years (Blayney 1929b). Very early on in his study, he realized that “it was unusual to find a root-end with but a single apical foramen.” His conclusions strongly suggestedthat: “1)Thedentalpulpmayberemovedwithout causing irreparabledamage totheperiapicaltissues, providedthe followingdefiniteplanofoperationis carriedout:a)surgicallycleantechnic ;b)useof onlymildantiseptics,allcausticsbeingeliminated;c) avoidanceofinjurytosofttissue inthe apical foramina;d)removalofalltruepulp tissue;(and) e) filling ofthe canal with abland,non-irritating, non-absorbablefilling materialtonearthesiteof amputation. 2) Followingtheoperation,thereisbegun,intheapical region,aprocessofresorptionthatenlargesthe apicalforamen,or anewchannelmay be cutthat more successfullymeetsthe conditionswithin the canal. 3) Theseresorptionsmay heal,with theformationof calcifiedmaterialresemblingcementum. 4) Manyofthe apicalforaminamaybereduced insize byrepair calcification.Butthisreductionseldom obliteratesthe canal.assufficient spaceusually remains foranefficientcirculatoryapparatus. 5) Thefilling material,when incontact withsoft tissues,excitesaforeign-bodyreaction.Better results Fig.7Histologicalviewoftherootapexwithrootcanalfilling terminating2–3mmfromtheendoftheroot.Notethetissue areobtainedinthecasesthatareslightlyunderfilled.” belowtherootfillingisperiodontalinnatureandthewallsofthe (Blayney1929b). canalinthisareaarecoveredwithcementum.Thereisalsoahard tissuebarrierthathasformedadjacenttotherootfillingthatmay Similar findings were identified, and clinical tech- havebeeninducedbydentinchipsorrepresentsanosteocemental niques to achieve these results were supported by a response.Thispresentationamplifiesthefactthatinmanyteeththe pulpandpulpalcanalterminatesfarabovetheanatomicalrootend multitude of individuals during that era. As early as 1922, Noyes echoed these same directives as follows; however, he was also concerned with root fillings that cementalpermeability,especiallyinlightofthefocalinfec- were tooshort(NoyesE1922): tion theory and still approached teeth with compromised or necrotic pulps with the same focus, “Shall we, or shall Thereisone morethingIwant tosayinregard to we not, attempt to retain the pulpless tooth? In the pres- thesefillings thatdonot reachtheends ofthe canal. ence of the irrefutable dictum that the natural organ is Itismybeliefthatweshouldineverycase,wherever betterthanany substitute, the answer is ‘Weshall.’ Noyes we canpossibly do so,getourfillingtotheendofthe saidit succinctly; ‘…let us rathermakeita practiceto ex- PULP CANAL(Author’sEmphasis). Ineveryone of tractonlysuchteethasdiligent,conscientiousandpersist- those casesinwhich Ididnot getthere,you may ent effort have proven conclusively to be beyond our dependIspentanhour ormore,may two orthree,in present ability to put in wholesome, safe condition.’” trying toget there.Butthe pointIwant tomake (Noyes1921). particularly isthatwemay ignoreabsolutely the In 1929, Blayney published his results on 10 years of foramenthroughcementum ifwe can fillthepulp making histological analyses of root ends from extract canaltotheendofthedentin.Whileyou cannot filla teeth that had been root treated. He had several thou- minuteforamen, which isasfineasahair insome sand teeth in his history profile but chose to examine cases,inmyjudgmentatooth isthree orfourorten histologically 250 of these teeth, some of which were ex- timesassafeifyou filltheroottotheendofthe pulp tracted shortly after treatment due to a diagnosed canal,leavingthefine foramen throughthe cementum GutmannEvidence-BasedEndodontics (2016) 1:4 Page7of22 oftherootwithoutmeddling with it,asitwould beif you drilledthroughtheforamen andcarriedthefilling totheendoftherootandput acape overtheendof it, as Dr. Rhein advocates. (Fig. 8) (Author’s note: Dr. Rhein advocated filling beyond the end of the root so the filling material would encapsulate the apical 2–3 mm, thereby sealing off all the accessory communications.Hereferredtothisas“mortarization” oftherootend.)(Fig.9) However, Dr. Rhein had different opinions regarding root canal therapy that stood in opposition to the main- stream clinicians at that time, regarding procedural ac- complishments(Rhein 1920): Fig.9Maxillarymolarthathasrootfilingbeyondtheendofthe Thequestionofroot-canaltherapy isone that rootthatencompassestheroot-endanatomy,asproposedbyRhein embracesavery particular point,andthatis,thereis withhis“mortarization” noquestion thatIknowof, asamedicalman,outside of brain surgery, (andIwould even includealarge apicesoftheroots -Idefinitelyrefute the essential amountof brainsurgery) thatrequiresthesame pointofcriticism oftheessayist’spaper. (Rhein 1920) amountofskill,patienceandtime…When Ishow (Author’snote:thatrootcanalsshouldonlybefilled hundredsofroentgenograms -some ofthem dating totheendofthedentinalcanalandnotimpingeon backtoworkdonealmost30yearsago(Author’snote: the cementum). whichwould beinthelate1890s),showingabsolutely, sofarasaroentgenogram canshow,normaltissue To rationalize his technique of encapsulation even (with)thoroughencapsulationofgutta percha onthe further,Dr.Rheinindicatedthat: WhereIhavefound re-infectioninmyowncasesand havehadtoextract teeth, Ihavealso found invariably extraforaminaat somepointthathadnotbeen encapsulated, andwhich were the cause ofthe recurrenceofinfection.(Rhein 1920) The issue of necrotic remnants being left in apical accessory canals and treatment failure still reverberates in today’s clinical practice and provides the impetus for the promotion of filling to the root apex, using a tech- nique in which these canals may be filled. However, this achievement may be flawed with regard to histologically identifiedoutcomes(Ricucci&Siqueira2010). Interestingly, Grieves had fostered directives similar to Blayneyasearly as 1914–1915relative to the importance ofperiapicalpathosis,cemental repair,andapicalhealing in the presence of the apical ramifications (Grieves 1914a; Grieves 1914b). Thereissomeevidencefor believingthatremaining vesselsandapical pulp-shreds,lyingintouch with surrounding vascularity,eitherbecomeorganizedinto fibroustissueorforaminaare closed bydepositsof cementum orosteo-dentin.Thiscan occur onlyina vital apex,notinfected, norsaturatedwith chemicals, Fig.8Dr. Meyer L. Rhein—reproduced from J Dent Research norPERFORATEDANDOVER FILLED (Authors’ 1933;13:100 Emphasis);andonly inone towhichthe GutmannEvidence-BasedEndodontics (2016) 1:4 Page8of22 periodontiumisphysically attached.However,hegoes Therebedentistswhoconscientiously believethata ontosay, inhis extensive treatise, “The vital apex is, pulplesstoothisadeadtooth; thatevery deadtoothis thus,the cruxofallcanaloperations.Itsmaintenance doomedtoinfection; andthatallinfected teeth area isworth anyamountoftime andeffort. Itcannotbe menacetothehealth oftheindividual. tosuch encapsulated (Author’snote: asperDr.Rhein) practitionersthis communicationisnot addressed. because periodontalfibers areeverywhereattachedto Therebeotherswho believethatapulplesstoothmay it.Thereis,therefore,nodenudationorhypoplasiain besotreated thatitwillnot onlybetolerated bythe whichencapsulationsmaylie,unlesstheytraumatically humanbody,but maybemadetoserveitsfunction of protrudeintothemembrane,granulomata,orcysts. mastication,andaid intheinitialstepofdigestion, Quite the reverse: the denuded apex, necrotic by thusbecominganimportantfactor inmetabolismand whatever means, is not worth a moment’s effort, no anultimate contributortothe healthofthesubject. matter how medicated nor how well filled (Author’s Fromsuch assubscribe tothese tenetsIcrave note: this reflects the impact of focal infection). One attention,trustingthatImaydelivertothema of the gravest mistakes of dentistry is the stubborn messagewhich mayinsomesmall degreerendertheir belief that correct root-canal filling will cure apical effortstoministertosufferinghumanity more certain disease.” (Author’s note: this same concept is present andmoreeffacious.(Ricucci&Siqueira2010) today when clinicians say they are treating periapical lesions or apical periodontitis) The most perfect To do so, Ottolengui dictated his doctrines for root canaloperationisnevercurative,butonlyapreventive canalfillingprocedures(Ottolengui1922): procedure.(Grieves1920) “1.Anyradiographicevidenceofgutta percha beyond Quite vocal in this controversy of where to terminate theapex oftheroot,is aprotrusionofthefilling the root canal filling and the issue of retaining pulpless material… teeth was Dr. Rodrigues Ottolengui (Fig. 10) of New 2. Theprotusionofguttaperchabeyond the apex YorkCity(Ottolengui 1922): demandsspaceforitsoccupation. 3. …anyappearanceofgutta-perchabeyond theapex ofahealthyroot isanevidence ofafault inthe technique. 4. In the presence of infected apical areas…and the gutta percha has been forced beyond the apex… whether such infection, both of the area and of the protruding foreign body can be overcome, will be determined solely by the vital responses of the patient in each instance. Sometimes a cure will be accomplished in spite of the gutta percha. It is inconceivable, however, that the protruded material can act as a curative factor.” (Ottolengui 1922) Transitionsinthoughtandreaffirmationofclinical directives In the late 1930s, Dr. Bernhard Gottlieb (Fig. 11) pub- lished a monograph entitled “Dentistry in Individual Phases” (Gottlieb 1938). In this monograph, he dis- cusses the challenges that are present in dealing with root canal procedures, i.e., instruments and medica- ments, thatmaycomeincontact withtheperiapicaltis- sues during treatment. He indicated that he had no concept as to the response of these tissues to the treat- ment procedures, while at the same time hoping to Fig.10Dr.RodriguezOttolengui—reproducedfromPrinzH.Dental control any inflammatory responses that may prevent Chronology,Lea&Febiger,Philadelphia,1945.AlsofoundinDent healing with calcified tissues. To these purposes, he Cosmos1934;76(1):158 used a dog model in his investigations: GutmannEvidence-BasedEndodontics (2016) 1:4 Page9of22 Gottlieb understood the challenges faced with human teeth that required the removal of a viable dental pulp, but he also realized the importance of this same set of clinical circumstances in the presence of an infected pulp ornecrotic pulp: The claimsthatwe hadtosatisfy inthetreatmentofa periapicalfocusofinfection tookanamuchmore complicatedform, andaspectsdevelopedthatwe could innowiseanticipate. We could formnoclear pictureofwhat happened tothe necrotic root surfaces,norcouldweimaginewhatmightbe expected from branchings oftherootcanalsthat harboureddeadtissue. Itwasdemonstrated that soon after sterilizingandfreeingthesedeadtissue ofgerms, the neighbouringinflamedconnectivetissueregained health,andalmost atonce deposited cementum upon the necrotic surfaces ofthe tooth.Thiscementum may alsoclose uptheapical foramen, andthus produceacomplete surface consistingofliving cementum, which removescompletelyeverydoubt concerning retentionofsuchatooth. (Gottlieb 1938) In his assessment, Gottlieb defies the tenets of focal infection, indicating that properly performed root canal Fig.11Dr. Bernhard Gottlieb—reproduced from Gutmann JL. procedures, with retention of root-filling materials inside Bernhard Gottlieb’s impact on contemporary endodontology. the canal in the presence of a necrotic pulp, will result J Hist Dent 61:(2)85-106, 2013. Erratum 61:(3) 128, 2013. (http:// in biologic healing of the periapical tissues and the for- www.alumni-meduniwien.at/news/medizin+im+bild/bernhard+ mation of a cementum closure of the canal apically gottlieb). (http://www.alumni-meduniwien.at/news/medizin+im+ (Fig. 12). Furthermore, he was quite adamant about bild/bernhard+gottlieb) where to terminate these procedures, especially in the presenceofavital,yetpossibly inflamed, pulp, indicating that “surgical common sense forbids it” (that is, going past the apical foramen). He indicated that there are …inthe caseofextractionofthepulp itwasor healthy tissues at the point of severance apically, and importancetoestablish,how any givenmethodwould therefore, the use of caustic drugs was prohibited, files operatewhen thepulpcanalwasindirect connection must not penetrate the foramen (present day concept of with theperiapicalconnectivetissue. In the case of patency filing), and any damage to the periapical tissues the dog, on account of its ramifications the pulp may well prevent the healing of these tissues with the tissue is without exception separated from the cementum (Davis 1923). He published his findings in connective tissue, so that no connection is 1928 and presented them at the 8th International Dental established with the periapical connective tissue Congress—FDI in 1931 in a special session that featured throughout the manipulation in the canal. We world-class authorities who addressed the controlling of now had to drill through the tooth to this area, rootcanaltreatmentprocedures (Gottlieb et al.1928): and at once it was evident that we must use a much more pretentious method, if we are to come Onceapieceofforeignmaterialhaspenetrated in direct contact the periapical tissue and if we throughtheforamen, nofavorable condition ofany were to care for injuries to the connective tissue. kindcaninducethe closureoftheentrancebythe This change made in the procedure of the formation ofahardwall.(Gottliebetal.1950) experiment by this drilling was necessitated by the fact that in the human mouth it was not at Gottlieb’s philosophies went far beyond where to ter- all uncommon to come in contact with the minate both instrumentation and obturation. Being one periapical connective tissue during pulp extraction. of the stalwarts from the Vienna School of Medicine, (Gottlieb 1938) who came to the USA (Gutmann 2013; Kremenak & GutmannEvidence-BasedEndodontics (2016) 1:4 Page10of22 Fig.12Rootapexshowingcementalcoveragefollowingrootcanalproceduresandsubsequenthealing.Arepresentstherootfilling;Cisthe originalcementum,whileDisthenewcementum;Bisthejunctionofthetwotissues;andEistheinflammation-freeperiodontalligament. GottliebB.FromdataaccumulatedonProfessorGottliebfromtheGottliebCollectionpresentlylocatedattheBaylorCollegeofDentistry,Dallas,TX Squier 1997), his focus in dentistry was highly biological that had been ground fine and sterilized. After mixing and he devised a method to ensure the development of the dentin powder with sulfathiazole or restorative ce- hard tissue (cementum) at the root apex following root ment, it was applied to the apical portion of the root canal procedures. His method to achieve apical healing canal prior to obturation. The success of his approach with cementum was simple. He used dentin from teeth was demonstrated in an animal model (Fig. 13) and Fig.13Healingattherootapexwithcementumfollowingtheuseofadentin-cementrootcanalfillingintheapicalportionoftheroot.Gottlieb B.FromdataaccumulatedonProfessorGottliebfromtheGottliebCollectionpresentlylocatedattheBaylorCollegeofDentistry,Dallas,TX