ROEN0110

14 I I special _ endo-implant algorithm transport,bacterialpenetration,glucoseleakage)was used to evaluate the sealing efficacy of endodontic filling materials and techniques by assessing the de- gree of penetration/absorbance of these tracers.31–33 Unfortunately, leakage studies are limited static models that do not simulate the conditions found intheoralcavity(temperaturechanges,dietaryinflu- ences, salivary flow). Given the historic dominance of in vitro testing, the clinician must be cautious in extrapolating study findings to the clinical situation, regardless of manufacturer’s claims.34 This reliance on invalid testing protocols diminishes the mono- block assertions applied to the new generation of adhesive obturating materials proposed as the re- placement material for gutta-percha.35 Gutta-perchawasintroducedtodentistrybyEdwin Truman in 1847.36 The concept of thermo-labile verticalcondensationofgutta-perchawasoriginally described by Dr J. R. Blaney in 1927.37 The defining article on obturation remains Dr Schilder’s classic on filling the root-canal space in three dimensions, published 40 years later.38 Logically, one cannot physically fill the root canal in two dimensions; however, one can fill the root- canal space badly in three dimensions. This does not disprove Dr Schilder’s exposition, but it does demon- stratethatwordscaneasilybemisconstruedandalter perspective once they become, as Kipling said, “the mostpowerfuldrugofmankind”.Ironically,Schilder’s articlecamesevenyearspriortohistreatiseonclean- ing and shaping the root-canal system, which even to this day remains the iconic standard. TheWashingtonStudybyIngleindicatedthat58% of treatment failures were due to incomplete obtura- tion.39Thecorollaryisobvious:teeththatarepoorlyob- turatedareinvariablypoorlydebridedanddisinfected. Procedural errors such as loss of working length, canal/apical transportation, perforations, loss of co- ronalsealandverticalrootfractureshavebeenproven toaffecttheintegrityoftheapicalsealadversely.40,41 TheTorontostudythatevaluatedsuccessandfail- ure of endodontic treatment at four to six years after completion of treatment found that teeth treated with a flared canal preparation and vertical conden- sation of thermo-labile gutta-percha had a higher success rate when compared with step-back canal preparation and lateral compaction. Highlighting the vertical condensation of warm gutta-percha ob- turation technique as a factor influencing success andfailuresimplyconfirmedaperspectiveevidentto most endodontists from years of clinical empiricism. Thereisanever-endingarrayofobturationmate- rials, delivery systems and sealers appearing in the marketplace. Each is hallmarked by proprietary mod- ificationsandeachisheraldedasthemostsignificant iteration in obturation since the previous one; today, we practice with a sad truism—marketing inexorably directs science. However, gutta-percha in combina- tion with a myriad of sealers and solvents remains the primary endodontic obturating material. The dominant systems remain carrier-based obturation (Thermafil, Tulsa Dental Specialties), Continuous Fig. 11_Numerous researchers have demonstrated that the concept of keeping the apical foramen as small as practical does not mean a size #20 or 25 file. This Schilderian concept should read as small as the apical morphology permits in order to ensure that the free flow of irrigant to the apical terminus enables more definitive cleaning of the apical segment of the root-canal space. Fig. 12_The artist/clinician recognises that negative space surrounding an object is equally important as the object itself. In the case of root-canal therapy, the positive space is alterable but must be created in balance with the encompassing negative space to ensure morphological integrity. Fig. 13_While there is no meta- analysis to elucidate this concern, the incidence of fracture of the mesial root of mandibular molars has been shown to have a significant correlation to cusp fracturing. roots1_2010 Fig. 11 Fig. 13 Fig. 12