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Dental Tribune Middle East & Africa Edition | 1/2017 9 mCMESELFINSTRUCTIONPROGRAM CAPPmea together with Dental Tribune provides the opportunity with its mCME - Self Instruction Program a quick and simple way to meet your continuingeducationneeds.mCMEoffersyoutheflexibilitytoworkatyour own pace through the material from any location at any time. The content is international, drawn from the upper echelon of dental medicine, but also presentsaregionaloutlookintermsofperspectiveandsubjectmatter. Membership YearlymembershipsubscriptionformCME:1,100AED OneTimearticlenewspapersubscription:250AEDperissue.Afterthe payment,youwillreceiveyourmembershipnumberandallowingyouto starttheprogram. 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Formoreinformationpleasecontactevents@cappmea.comor +97143616174 FORINTERACTIONWITHTHEAUTHORSFINDTHECONTACTDETAILSAT THEENDOFEACHARTICLE. of the laser in NaOCl combined with the high peak power derived from the short pulse duration employed (50 µs) determines a photomechani- cal phenomenon.30 A study showed thattherewasnodifferenceinbacte- rial reduction achieved by NaOCl ac- tivated by laser compared with only NaOCl.31 Another study investigated thecapabilityofLAItoremoveabac- terial biofilm created in vitro on the canal walls.32 This study found that it did not completely remove the bio- film from the apical third of the root canalandinfecteddentinaltubules. However, the finding that laser acti- vationgeneratedahighernumberof samples with negative bacterial cul- turesandalowernumberofbacteria in the apical third was a promising result regarding the effectiveness of the technique, and has been con- firmedbyamorerecentstudy.33 Additionaldisinfection systems In addition to the above-mentioned systems that were able to activate the endodontic irrigants and to im- prove their cleaning capability, en- dodontic research is oriented toward the identification of alternative solu- tions that could further refine disin- fection and assist in the destruction of biofilms and the elimination of micro-organisms. For this purpose, different sub- stances and technologies have been investigatedovertimewithdifferent results. Photoactivateddisinfection A new method recently introduced inendodonticsisphotoactivateddis- infection. This technique is based on the principle that the photosensitiz- ing molecules (photosensitizer, PS) have the ability to bind to the mem- branesofthebacteria. The PS is activated with a specific wavelength and produces free oxy- gen, which causes the rupture of the bacterial cell wall on which the PS is associated, determining a bacteri- cidalaction. 34 Extensive laboratory studies have shown that the two components do not produce any effect on bacteria or on normal tissue when used in- dependently of each other; it is only the combination of PS and light that exerttheeffectonthebacteria.34 An endodontic system called light- activateddisinfection(LAD)hasbeen developed based on a combination ofaPSandaspeciallightsource. ThePSattacksthemembranesofmi- cro-organismsandbindstotheirsur- face, absorbs energy from light and then releases this energy in the form ofoxygen,whichistransformedinto highlyreactiveformsthateffectively destroy microorganisms LAD is ef- fective not only against bacteria, but also against other micro-organisms, including viruses, fungi and proto- zoa. The PSs have far less affinity for the cells of the body; therefore, tox- icity tests carried out did not report adverse effects of this treatment. Clinically, after root canal prepara- tion, the PS is introduced into the canal to working length with an en- dodontic needle and is left in situ for 60 s to allow the solution to come into contact with the bacteria and spread through any structures, such asbiofilms. The specific endodontic tip is then inserted into the root canal up to the depth that can be reached and irradiation is performed for 30 s in each canal (Fig. 4). This technique has proven to be effective in labo- ratory studies at eliminating high concentrations of bacteria present in artificially infected root canals.35 Careshouldbetakentoensuremaxi- mum penetration of the PS, since it is important that it come into direct contact with the bacteria, otherwise theeffectofphotosensitivitywillnot occur. In addition, LAD appears to be effective not only against the bacte- ria in suspension, but also against biofilm.5 Research is now directed toward evaluating the possibility of increasing the antibiofilm effective- ness of LAD, combining the benefits ofphotodynamictherapywiththose of bioactive glasses and nanoparti- cles, which will be described later. Currently LAD is not considered as an alternative, but rather as a pos- sible supplement to standard proto- colsofrootcanaldisinfectionalready inuse.5 Laser One of the main disadvantages of the current endodontic irrigants is that their bactericidal effect is lim- itedprimarilytothemainrootcanal. In the endodontic field, several types of lasers have been used to improve root canal disinfection: the diode laser, carbon dioxide laser, Er:YAG laser and Nd:YAG laser. The bacteri- cidal action of the laser depends on the characteristics of its wavelength andenergy,andinmanycasesisdue to thermal effects. The thermal ef- fect induced by the laser produces an alteration of the bacterial cell wall that leads to changes in osmotic gra- dients up to cell death. Some studies haveconcludedthatlaserirradiation is not an alternative, but rather a possiblesupplementtoexistingpro- tocols to disinfect root canals.36 The laser energy emitted from the tip of the optical fiber is directed along the canalandnotnecessarilylaterallyto- ward the walls. In order to overcome this limitation, a new delivery sys- tem of the laser was developed. The system consists of a tube that allows the emission of the radiation later- ally instead, directed through a sin- gle opening at its terminal end. The objective of this modification was to improve the antimicrobial effect of the laser in order to penetrate and destroy microbes in the root canal wallsandinthedentinaltubules. However, complete elimination of the biofilm and bacteria has not yet beenpossible,andtheeffectofthela- serhasbeenfoundtobelessrelevant than that of the classical solutions of NaOCl.37 In conclusion, strong evidence is not currently available to support the application of high- powerlasersfordirectdisinfectionof rootcanals.38 Ozone Ozone is an unstable and energetic form of oxygen that rapidly dissoci- ates in water and releases a reactive formofoxygenthatcanoxidizecells. It has been suggested that ozone may have antimicrobial efficacy without inducing the development of drug resistance and for this rea- son it was also used in endodontics. However, the results of the available studies on its effectiveness against endodonticpathogensareinconsist- ent,39especiallyagainstbiofilms. The antibacterial effectiveness of ozone was found not comparable andlessthanthatofNaOCl.39 Alternativeantibacterialsystems Nanoparticles Nanoparticles are microscopic par- ticles between 1 and 100 nm in size that have antibacterial properties and a tendency to induce much low- er drug resistance compared with traditional antibiotics. For example, nanoparticles of magnesium ox- ide, calcium oxide or zinc oxide are bacteriostatic and bactericidal. They generate active oxygen species that areresponsiblefortheirantibacterial effect through electrostatic interac- tion between positively charged na- noparticles and negatively charged bacterialcells,resultinginaccumula- tion of a large number of nanopar- ticles on a bacterial cell membrane and a subsequent increase in its per- meability associated with the loss of itsfunctions. Nanoparticles synthesized from powders of silver, copper oxide or zinc oxide are currently used for their antimicrobial activity. In ad- dition, nanoparticles can alter the chemical and physical properties of dentin and reduce the strength of adhesion of bacteria to the dentin itself, thus limiting recolonization and bacterial biofilm formation. In any case, the possible success of the application of nanoparticles in en- dodontics will depend essentially on the manner in which they can be delivered in the most complex root canalanatomy. Bioactiveglass Recently, bioactive glass or bioactive glass-ceramicshavebeenasubjectof considerable interest for endodontic disinfectionowingtotheirantibacte- rialproperties,butconflictingresults havebeenobtained.5 Naturalplantextracts A current trend is the use of natural plant extracts, taking advantage of the antibacterial activity of poly- phenolic molecules generally used for storing food. These compounds have been found to have poor anti- bacterial efficacy, but several dem- onstrate significant ability to reduce the formation of biofilms, although themechanismbywhichthisoccurs isnotclear.5 Noninstrumentationtechniques Thefirsttrialofamethodofcleaning without canal preparation was the noninstrumentation technique con- ceivedbyLussietal.40 Thistechnique did not provide for the enlargement of the root canals because there was no mechanical instrumentation of the root canal walls. In fact, root canal cleaning was exclusively ob- tained with the use of NaOCl at low concentration, introduced and re- moved from the canal using a vacu- umpumpandanelectricpistonthat created fields of alternating pressure insidethecanal. These caused the implosion of the produced bubbles and hydrody- namicturbulencethatfacilitatedthe penetration of NaOCl into the root canal ramifications. At the end of this procedure, the canals were filled withacementconveyedbythesame vacuum pump. This system did not prove to be of substantial effective- nessandwasnevermarketed. Recently, a method has been devel- oped for cleaning the entire root canal system through the use of a broad spectrum of sound waves transmitted within an irrigating so- lution to remove pulp tissue, debris andmicro-organismsquickly. One study showed that this tech- nique was able to dissolve the tis- sue tested at a rate significantly higher than that of conventional irrigation.4 More research is needed to determine whether this approach is effective in the root canal system with minimally invasive or no canal preparation. Conclusion According to current knowledge, en- dodontic pathology is an infection mediated by bacteria and in particu- lar by biofilm. From a biological per- spective, endodontic therapy must then be directed toward the elimina- tionofmicro-organismsandthepre- ventionofpossiblereinfection. Unfortunately, the root canal sys- tem, with its anatomical complex- ity, represents a challenging envi- ronment for the effective removal of bacteria and biofilm adherent to the canal walls. Chemomechanical preparation involves mechanical instrumentationandantibacterialir- rigation,anditisthemostimportant phaseofthedisinfectionoftheendo- dontic space. The technological ad- vances of instruments have brought significant improvements in the ability to shape the root canals, with fewer procedural complications. In themanagementoftheinfectedroot canal system, various antimicrobial agents have been employed. Fur- thermore, some clinical measures, suchasanincreaseinapicalprepara- tion and a more effective system of irrigant delivery and activation of ir- rigant, can promote and make more predictable the reduction of intraca- nal bacteria, especially in complex anatomical and noninstrumented portionsoftherootcanalsystem. Editorial note: A list of references is availablefromthepublisher. Fig.3:Apicalnegative-pressureirrigationsystemusedtoenhance debridement. Fig.4:Disinfectionactivatedbylighttoenhancerootcanalclean- ing. Dr Gianluca Plotino is a senior lecturer in the Department of Endo- dontics and adjunct professor in the School of Dental Hygiene at the Sapienza Univer- Dr Nicola M. Grande is Assistant Professor of Endodontics at Università Cattolica del Sacro Cuore in Rome. He completed his PhD at the same university in 2009, with a thesis on an innovative technique he developedfortherestorationofendodon- tically treated teeth. He has contributed tothedevelopmentofvariousinstrumen- tation systems and new techniques, and holdsinternationalpatentsinthefieldsof endodontics and oral surgery. Dr Grande has published extensively in international peer-reviewedjournalsandhascontribut- edtoseveralbooksofendodonticinterest. Prof. Gianluca Gambarini is Professor of Endodontics at the Sapienza University of Rome’s dental school. He is an interna- tional lecturer and researcher, and active- ly collaborates with a number of manu- facturers all over the world to develop new technologies, operative procedures and materials for root canal treatment. Prof. Gambarini also works in a private endodonticspracticeinRome. sity of Rome in Italy. He serves on the edi- torial boards of and is an official reviewer for several journals, and has organized several research groups worldwide. He is the author and co-author of more than 70 articles in international scientific peer- reviewed journals with high impact fac- tors on different endodontic and restora- tive topics. ◊Page8 mCME Dental Tribune Middle East & Africa Edition | 1/20179