Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2016-05-18, 11:28:18 | version 1.38.0
| review canal disinfection 18 roots 2 2016 tic with a smooth surface and increased taper or with a surface with lateral plastic extensions, that have dimensions appropriate to achieve the work- inglengthifusedafterthecanalpreparation.Stud- iesonthesesystemshaveshownconflictingresults. In general, the results are better than with hand ir- rigation 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 aparticularinstrumentwithanabrasivesurfacethat enlarges the canal via friction in a vibrating motion andallowsirriganttoflowthroughthefileitself.This system has shown excellent results in terms of re- specting the anatomy and cleaning of difficult root canalanatomies,suchasdifficultisthmuses,ovalca- nalsorC-shapedcanals.19 Thelowcuttingefficiency of this system in some cases may limit its use in root canal preparation, but makes it an excellent addi- tional technique to enhance the cleaning and disin- fection of the root canal system at the end of the preparation.20 The concept of continuous irrigation wasdevelopedinthepastwiththeuseofmechanical instruments for sonic and ultrasonic preparation that could concurrently clean through the continu- ous release of irrigant. 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 effec- tive method for disinfecting the root canals. The recent systems use smooth plastic tips of different sizesactivatedatasonicfrequencybyahandpiece. Thesystemseemstobeabletocleanthemaincanal effectively, to remove the smear layer and to pro- mote the filling of a greater number of lateral ca- nals.17 Anotherrecentlyintroducedtechniqueuses asyringewithsonicvibrationthatallowsthedeliv- ery and activation of the irrigant in the root canal simultaneously. Sonic activation differs from ul- trasonicactivationinthatitoperatesatalowerfre- quency(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-organismsandcanalwallstobeeffective,the accessibility of the irrigant to the whole root canal system, in particular in the apical third, is essential. Inordertodelivertheirrigantintotherootcanalfor the entire length and to obtain a good flow of fluid, apical negative-pressure systems have been intro- ducedthatreleaseandremovetheirrigantsimulta- neously. These systems consist of a macro-cannula for the coronal and middle portions and a microcannula for theapicalportion,andthecannulasareconnectedto a syringe for irrigation and the aspiration system in- tegrated with the dental unit (Fig. 3). During irriga- tion,atipconnectedwithasyringedeliverstheirrig- anttothepulpchamberwithouttheriskofoverflow, while the cannula placed in the canal pulls irrigant into the canal, through the aspiration system to which it is connected, and evacuates it through the suction holes. This system is intended to ensure a constant and continuous flow of new irrigant into the apical third safely and with a lower risk of extru- sion.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 inaccessible areas,26 withresultsinthemajorityofcasessimilarto thoseofultrasonicactivationtechniques.27–29 Froma clinical perspective, apical negative-pressure sys- temscanbeeffectivelyintegratedwithultrasonicir- rigation techniques because they act by different mechanisms. They can operate in synergy with the objective to obtain cleaner canals, especially in the apical third and the most inaccessible areas. Laser activation Theinteractionbetweenthelaserandtheirrigant in the root canal is a new area of interest in the field of endodontic disinfection. This concept is the base of laser-activated irrigation (LAI) and photon-initi- ated photoacoustic streaming (PIPS) technology.30 The mechanism of this interaction has been at- tributedtotheeffectiveabsorptionofthelaserlight by NaOCl. This leads to the vaporization of the irrig- ant and to the formation of vapor bubbles, which expand and implode with secondary cavitation ef- fects. The PIPS technique is based on the power of the Er:YAG laser to create photoacoustic shock waves within the irrigant introduced into the canal. Whenitisactivatedinalimitedvolumeofliquid,the highabsorptionofthelaserinNaOClcombinedwith the high peak power derived from the short pulse duration employed (50 µs) determines a photome- chanical phenomenon.30 A study showed that there was no difference in bacterial reduction achieved by NaOCl activated by laser compared with only NaOCl.31 Another study investigated the capability of LAI to remove a bacterial biofilm created in vitro on the canal walls.32 This study found that it did not completelyremovethebiofilmfromtheapicalthird of the root canal and infected dentinal tubules. However,thefindingthatlaseractivationgenerated a higher number of samples with negative bacterial culturesandalowernumberofbacteriaintheapical thirdwasapromisingresultregardingtheeffective- ness of the technique, and has been confirmed by a more recent study.33 22016