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roots - international magazine of endodontology No. 2, 2016

canal disinfection review | 17 roots 2 2016 UltrasonicactivationofNaOClof30–60 sforeach canal, with three cycles of 10–20  s (always using newirrigant),appearstobesufficienttimetoobtain clean canals at the end of the preparation phase (Figs. 1&2).7 Ultrasoundappearstobelesseffective in enhancing the activity of EDTA, although it may contributetobetterremovalofthesmearlayer.7 The accumulationofdebrisproducedbymechanicalin- strumentation in inaccessible areas is preventable byusingultrasonicactivationofNaOClevenduring thepreparationphase.8 Theuseofasystemofultra- sonic continuous irrigation might therefore be ad- vantageous.Itinvolvestheuseofaneedleactivated by ultrasound. With this method, the irrigant is re- leased into the canal and is activated by the action of the ultrasonic needle simultaneously.9 Chlorhexidine A final flush with 2 % chlorhexidine (CHX) after the use of NaOCl (to dissolve the organic compo- nent) and EDTA (to eliminate the smear layer) has been proposed to ensure good results in cases of persistent infection, owing to its broad spectrum of actionanditspropertyofsubstantivity.5, 10 However, the use of CHX is hindered by the interaction be- tween NaOCl and CHX, which tends to create prod- ucts that may discolor the tooth and precipitates that may be potentially mutagenic. For this reason, CHX should not be used in conjunction with or im- mediatelyafterNaOCl.11 Thisinteractioncanbepre- vented or minimized by an intermediate wash with absolute alcohol, saline or distilled water.12 Activation systems Mechanical instrumentation alone can reduce the number of micro-organisms present within the root canal system even without the use of irrigants and intracanal dressings,13 but it is not able to en- sureaneffectiveandcompletecleaning.14 Irrigating solutionswithouttheaidofmechanicalpreparation are not able to reduce the intracanal bacterial in- fection significantly.15 For these reasons, today re- search is oriented toward the study of systems that can improve root canal disinfection through me- chanical activation of endodontic irrigants, and in particularNaOCl.Multipleagitationtechniquesand systems for irrigants have been used over time,16 demonstrating more or less positive results.17 Manual agitation techniques The simplest technique of mechanical activation of irrigants is manual agitation, which can be per- formed with different systems. The easiest way to achievethiseffectistomoveverticallyanendodon- tic file that is passive in the canal. The use of the file facilitates the penetration of the irrigant, leads to a moreeffectivedeliveryofirriganttotheuntouched canal surfaces and reduces the presence of air bub- bles in the canal space,18 but does not improve the final cleaning.17 Another similar technique moves vertically a gutta-percha cone to working length withthecanalfilledwithirrigant.Eventhismethod, however, has not been found to improve the in- tracanal cleaning.9, 17 For this purpose, in each case, wellfitting gutta-percha cones (increased taper) were more effective than cones with the standard taper (0.02).9 The use of endodontic brushes and of particular needles for endodontic irrigation with bristles on their surface is another technique sug- gestedinordertomovetheirrigantmoreeffectively within the canals. These systems have been shown to be valid in the removal of the smear layer from rootcanalwallsandthustheycanberecommended duringirrigationwithEDTAtoimprovetheirefficacy at the end of the preparation. Machine-assisted agitation systems Theevolutionofmanualsystemsledtotheintro- ductionofinstrumentsthatcanberotatedinhand- piecesatlowspeedinsidethecanalfilledwithirrig- ant. They are rotary brushes too large to be brought close to the working length; thus, they can be used effectively only in the coronal and middle thirds of thecanal.Othersimilarinstrumentsarefilesinplas- Figs. 1 & 2: Ultrasonic activation with a passive file (Fig.1) and an active file (Fig.2). Fig.1 Fig.2 22016

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