ROEN0110

22 I I clinical report _ apical microsurgery series For the preparation of an isthmus, an uncoated, fine-pointedtip(CT-1,SybronEndo)isinsertedintothe ultrasonic unit and used to create a precise series of multiple‘dots’onthestainedorimaginarylinebetween the two canals. For the dot technique, the ultrasonic unit is set at a low power setting but inactivated, the water spray is turned off, a CT-1 tip is placed exactly wheredesired,andtherheostatistappedforjustanin- stant. The process is repeated as many times as neces- sary until there is a series of ‘dots’ (Fig. 7a). Then, while thewatersprayisstilloff,thedotsaregentlyconnected tocreatetheinitial,shallowbutprecisetrackinggroove (Fig. 7b). The dot technique is of great value, especially when there is concavity present and the width of the bevelledrootisverythinmesiallytodistally.Theresult- antgrooveservesasadefiniteguideforthecompletion oftheisthmusportionoftheREP.Then,withthewater sprayturnedbackonandthepowerincreasedslightly, a pointed, coated tip can be used more aggressively to deepenthetrackinggroove.Inthismanner,accuracyis completely controlled and there is no chance of slip- ping while preparing the isthmus in a very thin root. Onoccasion,ifthewallsofthepreparationbecometoo thin,furtherbevellingmaybenecessary. Throughout the REP process, it is important to use the Stropko Irrigator to rinse and dry the REP in order to ensure it is kept within the long axis of the canals and all debris is being removed as planned. Various sizes of micro-mirrors or an endoscope can be used to periodically inspect the preparation and confirm accuracy.Apre-cutandpre-bent25-gaugeendodon- tic irrigating needle (Monoject, Carson Dental) works well for this purpose. The notched end is removed by rapidly bending the end third rapidly back and forth with Howe Pliers (Magnum Ortho) until it separates. The needle inserted into the Stropko Irrigator is then bent to a similar angle to that of the ultrasonic tip to be used for the REP (Fig. 8). Always keep in mind that cleanliness and dryness are essential for good visibil- ity when using the OM. The buccal aspect of the internal wall of the REP is of particular interest. Dr Richard Rubinstein was the first to point out that often this area is not debrided, owing to the angulation of the ultrasonic tip within the canal system during the REP. If there is some gutta-perchastreamingupthesideofthewallandthe preparationisfinished,thebestthingistouseasmall plugger and fold the gutta-percha coronally so the wall is clean once more. It is usually futile to attempt to remove that gutta-percha with an ultrasonic tip. The ideal REP should: 1) be within the long axis of the canal system; 2) have parallel walls; 3) be at least 3 mm in depth (including the isthmus portion of the preparation); 4) be adequately extended to include any buccal or lingual variations of the canal system; 5) be clean (free of a smear layer); and 6) be dry and ready to accept any type of root-end filling material. AftercompletionoftheREP,itshouldberinsedand driedoncemorewiththeStropkoIrrigator.TheREPis re-inspected, using micro-mirrors and the varying powers of the OM and/or endoscope, in order to en- sure it is clean and within the long axis of the canal system. At this time, the REP is etched with blue 35% phosphoricacidgel(Ultra-Etch,Ultradent)toremove the smear layer. After 15 to 20 seconds, the REP is thoroughly rinsed and dried with the Stropko Irriga- torandre-examinedwiththeOM.Ifallissatisfactory, a20-secondapplicationof2%chlorhexidinewillhelp eliminate any residual organisms. After a final rinse and dry, the REP is ready for the root-end fill. In the final two parts of this series, we will dis- cuss Retrofill materials and techniques (Part V) and Sutures,suturingtechniqueandhealing (Part VI)._ Editorial note: A complete list of references is available fromthepublisher. roots1_2010 Fig. 4_A surgical handpiece, such as Impact Air (SybronEndo), should be used to prevent the possibility of an air embolism. Figs. 5a & b_Unstained (a) and stained (b) resected root surfaces. (Images courtesy of Dr Gary Carr). Fig. 6_An illustration of an isthmus lying just below the surface that would not be evident even after staining with methylene blue. Fig. 7a_The series of ‘dots’ permit easy and accurate preparation of an isthmus in a root end that is very thin. Fig. 7b_With the water spray still off, the ‘dots’ are connected to establish a tracking groove in order to guide a more aggressive ultrasonic tip in finishing the REP. Fig. 8_For ergonomics, the modified tip used in the Stropko Irrigator should be bent to an angle similar to that of the ultrasonic tip that will be used during the REP. Dr John J.Stropko 8757 E.Double Eagle Dr. Carefree,AZ 85377 USA E-mail:topendo@aol.com _contact roots Fig. 8 Fig. 4 Fig. 6 Fig. 7a Fig. 7b Fig. 5a Fig. 5b