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72 — issue 2016 Endodontics Article filledwithirrigant.Eventhismethod,how- ever, has not been found to improve the intracanal cleaning.9, 17 Forthis purpose, in eachcase,well-fittinggutta-perchacones (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 suggested in order to move the irrigant more effectively within the canals. These systems have been shown to be valid in the removal of the smearlayerfrom root canal walls and thus they can be recommended during irriga- tion with EDTA to improve their efficacy at the end of the preparation. — Machine-assisted agitation systems Theevolutionofmanualsystemsledtothe introduction of instruments that can be rotated in handpieces at low speed inside the canal filled with irrigant. They are ro- tarybrushestoo largeto be brought close to the working length; thus, they can be used effectively only in the coronal and middle thirds of the canal. Other similar instruments are files in plastic with a smooth surface and increased taper or with a surface with lateral plastic exten- sions,thathavedimensionsappropriateto achieve the working length if used after the canal preparation. Studies on these systems have shown conflicting results. In general, the results are better than with hand irrigation with a syringe, but lower than that of other more effective systems.16 — Continuous irrigation during instrumentation Recently, a new system for root canal preparation has been introduced to the market. This system uses a particular in- strumentwithanabrasivesurfacethaten- larges the canal via friction in a vibrating motionandallowsirriganttoflowthrough the file itself. This system has shown ex- cellent results in terms of respecting the anatomy and cleaning of difficult root canal anatomies, such as difficult isth- muses, oval canals or C-shaped canals.19 The low cutting efficiency of this system insomecasesmaylimititsuseinrootcanal preparation, but makes it an excellent ad- ditionaltechniquetoenhancethecleaning and disinfection of the root canal system at the end of the preparation.20 The con- cept of continuous irrigation was devel- opedinthepastwiththeuseofmechanical instruments for sonic and ultrasonic preparationthatcouldconcurrentlyclean throughthecontinuousreleaseofirrigant. These techniques were then abandoned for various reasons related to the poor quality of the preparation itself. — Sonic activation Sonic activation has been shown to be an effectivemethodfordisinfectingtheroot canals. The recent systems use smooth plastic tips of different sizes activated at asonicfrequencybyahandpiece.Thesys- tem seems to be able to clean the main canal effectively, to remove the smear layer and to promote the filling of a greaternumberoflateralcanals.17 Another recently introduced technique uses a sy- ringe with sonic vibration that allows the delivery and activation of the irrigant in the root canal simultaneously. Sonic acti- vationdiffersfromultrasonicactivationin that it operates at a lower frequency (1–6 kHz),andforthisreasonitisgenerally found to be less effective in removing debris than are ultrasonic systems.17, 21, 22 — Apical negative-pressure irrigation As the irrigant must be in direct contact with the micro-organisms and canal walls to be effective, the accessibility of the ir- rigant to the whole root canal system, in particularintheapicalthird,isessential.In order to deliver the irrigant into the root canal for the entire length and to obtain a good flow of fluid, apical negative-pres- sure systems have been introduced that release and remove the irrigant simulta- neously. These systems consist of a macro- cannula for the coronal and middle por- tions and a microcannula for the apical portion, and the cannulas are connected to a syringe for irrigation and the aspira- tionsystemintegratedwiththedentalunit (Fig. 3). During irrigation, atip connected with a syringe delivers the irrigant to the pulpchamberwithouttheriskofoverflow, while the cannula placed in the canal pulls irrigant intothe canal,throughthe aspira- tion system to which it is connected, and evacuates it through the suction holes. This system is intended to ensure a con- stant and continuous flow of new irrigant intotheapicalthirdsafelyandwithalower risk of extrusion.23 Most of the studies on this technique have shown that it is very effective at ensuring a greater volume of irrigant in the apical third24 and excellent removal of debris from this area25 and in- accessible areas,26 with results in the ma- jority of cases similar to those of ultra- sonic activation techniques.27–29 From a clinical perspective, apical negative- pressure systems can be effectively in- tegrated with ultrasonic irrigation tech- niques because they act by different mechanisms.Theycan operate in synergy with the objective to obtain cleaner canals, especially in the apical third and the most inaccessible areas. — Laser activation The interaction between the laser and the irrigant in the root canal is a new area of interest in the field of endodontic disin- fection. This concept is the base of laser- activated irrigation (LAI) and photon- initiated photoacoustic streaming (PIPS) technology.30 The mechanism of this in- teraction has been attributed to the ef- fective absorption of the laser light by NaOCl. This leads to the vaporization of the irrigant and to the formation of vapor bubbles, which expand and implode with secondary cavitation effects. The PIPS technique is based on the power of the Er:YAG laser to create photoacoustic shockwaveswithintheirrigantintroduced intothecanal.Whenitisactivatedinalim- ited volume of liquid, the high absorption of the laser in NaOCl combined with the high peak power derived from the short pulse duration employed (50μs) deter- minesaphotomechanicalphenomenon.30 A study showed that there was no differ- ence in bacterial reduction achieved by NaOCl activated by laser compared with only NaOCl.31 Another study investigated the capabilityof LAI to remove a bacterial biofilmcreatedinvitroonthecanalwalls.32 Thisstudyfoundthatitdidnotcompletely remove the biofilm from the apical third of the root canal and infected dentinal tubules.However,thefindingthatlaserac- tivation generated a higher number of samples with negative bacterial cultures and a lower number of bacteria in the api- cal third was a promising result regarding the effectiveness of the technique, and has been confirmed by a more recent study.33 Additional disinfection systems In addition to the above-mentioned sys- tems that were able to activate the en- dodontic irrigants and to improve their Article_Plotino_00-00.qxp_Layout 1 02.03.16 22:18 Seite 3 Article_Plotino_00-00.qxp_Layout 102.03.1622:18 Seite 3