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74 — issue 2016 Endodontics Article static and bactericidal. They generate ac- tive oxygen species that are responsible fortheirantibacterialeffectthroughelec- trostatic interaction between positively charged nanoparticles and negatively charged bacterial cells, resulting in accu- mulation of a large number of nanoparti- cles on a bacterial cell membrane and a subsequentincreaseinitspermeabilityas- sociated with the loss of its functions. Nanoparticles synthesized from powders of silver, copper oxide or zinc oxide are currently used for their antimicrobial ac- tivity. In addition, nanoparticles can alter the chemical and physical properties of dentin and reduce the strength of adhe- sion of bacteria to the dentin itself, thus limiting recolonization and bacterial biofilmformation.Inanycase,thepossible successoftheapplicationofnanoparticles in endodontics will depend essentially on themannerinwhichtheycanbedelivered in the most complex root canal anatomy. Bioactive glass Recently, bioactive glass or bioactive glass-ceramicshavebeenasubjectofcon- siderableinterestforendodonticdisinfec- tion owing to their antibacterial proper- ties, but conflicting results have been obtained.5 Natural plant extracts A current trend is the use of natural plant extracts,taking advantage ofthe antibac- terial activity of polyphenolic molecules generally used for storing food. These compoundshavebeenfoundtohavepoor antibacterial efficacy, but several demon- strate significant abilityto reducethefor- mation of biofilms, although the mecha- nism by which this occurs is not clear.5 — Noninstrumentation techniques Thefirsttrialofamethodofcleaningwith- out canal preparation was the noninstru- mentation technique conceived by Lussi et al.40 This technique did not provide for the enlargement of the root canals be- causetherewasnomechanicalinstrumen- tation of the root canal walls. In fact, root canal cleaning was exclusively obtained with the use of NaOCl at low concentra- tion, introduced and removed from the canalusingavacuumpumpandanelectric piston that created fields of alternating pressureinsidethecanal.Thesecausedthe implosion of the produced bubbles and hydrodynamic turbulence that facilitated the penetration of NaOCl into the root canal ramifications. Atthe end ofthis pro- cedure, the canals were filled with a ce- ment conveyed by the same vacuum pump. This system did not prove to be of substantial effectiveness and was never marketed. Recently,amethodhasbeendeveloped for cleaning the entire root canal system through the use of a broad spectrum of soundwavestransmittedwithinanirrigat- ing solution to remove pulp tissue, debris and micro-organisms quickly. One study showedthatthistechniquewasabletodis- solve the tissue tested at a rate signifi- cantlyhigherthan that of conventional ir- rigation.4 More research is needed to determinewhetherthisapproachiseffec- tive in the root canal system with mini- mally invasive or no canal preparation. Conclusion According to current knowledge, endo- dontic pathologyis an infection mediated by bacteria and in particular by biofilm. Fromabiologicalperspective,endodontic therapymustthen be directedtowardthe elimination of micro-organisms and the preventionofpossiblereinfection.Unfor- tunately, the root canal system, with its anatomical complexity, represents a chal- lenging environment for the effective re- movalofbacteriaandbiofilm adherent to the canal walls. Chemomechanicalprepa- ration involves mechanical instrumenta- tion and antibacterial irrigation, and it is the most important phase of the disinfec- tionoftheendodonticspace.Thetechno- logical advances of instruments have brought significant improvements in the abilitytoshapetherootcanals,withfewer procedural complications. Inthe manage- ment of the infected root canal system, various antimicrobial agents have been employed. Furthermore, some clinical measures, such as an increase in apical preparation and a more effective system of irrigant delivery and activation of irri- gant, can promote and make more pre- dictable the reduction of intracanal bac- teria,especiallyincomplexanatomicaland noninstrumented portions of the root canal system. Editorial note: A list of refer- ences is available from the publisher. and Nd:YAG laser. The bactericidal action ofthelaserdependsonthecharacteristics of its wavelength and energy, and in many cases is due to thermal effects. The ther- mal effect induced by the laser produces an alteration of the bacterial cell wall that leads to changes in osmotic gradients up to cell death. Some studies have con- cluded that laser irradiation is not an al- ternative, but rather a possible supple- ment to existing protocols to disinfect root canals.36 The laser energy emitted fromthetipoftheopticalfiberisdirected along the canal and not necessarily later- allytowardthewalls.Inordertoovercome this limitation, a new delivery system of the laser was developed. The system con- sists of a tube that allows the emission of the radiation laterally instead, directed through a single opening at its terminal end.Theobjectiveofthismodificationwas to improvethe antimicrobial effect ofthe laserinordertopenetrateanddestroymi- crobes in the root canal walls and in the dentinal tubules. However, complete eliminationofthebiofilmandbacteriahas not yet been possible, and the effect of thelaserhasbeenfoundtobelessrelevant than that of the classical solutions of NaOCl.37 In conclusion, strong evidence is not currently available to support the applicationofhigh-powerlasersfordirect disinfection of root canals.38 — Ozone Ozone is an unstable and energetic form ofoxygenthatrapidlydissociatesinwater and releases a reactive form of oxygen that can oxidize cells. It has been sug- gestedthat ozone mayhave antimicrobial efficacy without inducing the develop- ment of drug resistance and for this rea- son it was also used in endodontics. How- ever, the results of the available studies on its effectiveness against endodontic pathogens are inconsistent,39 especially against biofilms. The antibacterial effec- tiveness of ozone was found not compa- rable and less than that of NaOCl.39 — Alternative antibacterial systems Nanoparticles Nanoparticles are microscopic particles between 1 and 100 nm in size that have antibacterialpropertiesandatendencyto induce much lower drug resistance com- pared with traditional antibiotics. For ex- ample,nanoparticlesofmagnesiumoxide, calcium oxide or zinc oxide are bacterio- Article_Plotino_00-00.qxp_Layout 1 02.03.16 22:18 Seite 5 Article_Plotino_00-00.qxp_Layout 102.03.1622:18 Seite 5