ROEN0110

I 21 clinical report _ apical microsurgery series I roots1_2010 After the REB has been refined and crypt manage- mentiscompletelyundercontrol,theapicalsurfaceis rinsedanddriedwithaStropkoIrrigator.Thecleanand dried surface is then stained with methylene blue. It is important to allow the methylene blue to remain on the tooth for just a short period before gently rinsing and drying again, in order to enable inspection of the stained surface. Normally, a fresh, white piece of Telfa is reinserted for better lighting. If there are any fractures, isthmus tissue or accessories present, the staining will greatly enhance the operator’s ability to visualise them. Also, the methylene blue will stain the periodontalligamentandenabletheoperatortoensure theapexhasbeencompletelyresected(Figs.5a&b).If thereisanaccessorycanalpresent,theeasiestsolution is usually to bevel past it and re-stain; or, on occasion, the accessory can be troughed-out, leaving the bevel asis. Whentwocanalsarepresentinthesameroot,itis necessarytoprepareforanisthmusbetweenthetwo canals even if the staining did not reveal one. It has beenshownthatintheMBrootsofthemaxillaryfirst molars with two canals, the 4 mm section displayed a partial or complete isthmus 100% of the time.2 This, combined with the finding that two canals in thesamerootinmaxillarymolarspresentclinicallyat least 93% of the time in the MB root of the maxillary first molar, lends importance to always preparing the isthmus area of the REB.3 Although staining does not always reveal the presence of an isthmus, it may lie justbelowtheREBsurface,onlytobeexposedduring the remodelling of the surface of the bevelled root that normally takes place during the healing process (Fig. 6). The rule is to prepare an isthmus when there are two canals in one root. The preparation of the REP is best accomplished using ultrasonics. For the most part, they are all de- pendable and have a good service record. There are multitudes of ultrasonic tips from which to choose. Thenewerdiamond-coatedandventedtips(ProUltra tips,DENTSPLYTulsaDental;KiStips,Obtura/Spartan) are much more efficient and especially good at re- moving gutta-percha. Rather than the brand of the ultrasonicunitortypeoftip,themostimportantcon- sideration is the manner in which the instrument is used. The tendency for the new operator is to use the ultrasonic unit in the same manner (regarding pres- sure) as the handpiece. The secret is to start at a low power setting and use an extremely light touch. The lighter the touch, the more efficient the action of the tip will be. The correct amount of coolant is also im- portant. If too much spray is used, visibility and cut- ting efficiency will both be decreased. If too little spray is used, there will be insufficient cooling and overheating, which can lead to micro-cracks. Various left and right tips of various angles are necessaryonoccasion,butinmostcasesanteriortips will suffice. If the canal is large and/or filled with gutta-percha, a larger, coated tip can be used most efficiently. The key is to: 1) slow down; 2) be gentle; 3) use a light, brushing movement; and 4) carefully regulate the power setting of the ultrasonic unit.Thepowersettingwillvarygreatlydependingon thetipbeingusedandnatureofthepreparationtask. Fig. 2_Long bevel with round bur preparations, demonstrating angulation and orientation problems. (Courtesy: Dr Gary Carr) Figs. 3a & b_Inadequate and acute 45° bevel clearly demonstrates the way perforations can occur and canals can be missed. The operator’s view from the buccal (Fig. 3a). View of actual occurrence, as completely missed by the operator (Fig. 3b). Fig. 2 Fig. 3bFig. 3a

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