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ePaper created 2016-05-18, 11:28:18 | version 1.38.0
| review canal disinfection 20 roots 2 2016 In the endodontic field, several types of lasers have been used to improve root canal disinfec- tion: the diode laser, carbon dioxide laser, Er:YAG laser and Nd:YAG laser. The bactericidal action of the laser depends on the characteristics of its wavelength and energy, and in many cases is due to thermal effects. The thermal effect induced by the laser produces an alteration of the bacterial cell wall that leads to changes in osmotic gradi- ents up to cell death. Some studies have con- cludedthatlaserirradiationisnotanalternative, butratherapossiblesupplementtoexistingpro- tocols to disinfect root canals.36 The laser energy emitted from the tip of the optical fiber is di- rected along the canal and not necessarily later- ally toward the walls. In order to overcome this limitation,anewdeliverysystemofthelaserwas developed. The system consists of a tube that al- lows the emission of the radiation laterally in- stead, directed through a single 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 intherootcanalwallsandinthedentinaltubules. However, complete elimination of the biofilm and bacteria has not yet been possible, and the effect of the laser has been found to be less relevant than that of the classical solutions of NaOCl.37 In conclusion,strongevidenceisnotcurrentlyavail- able to support the application of high-power la- sers for direct disinfection of root canals.38 Ozone Ozone is an unstable and energetic form of oxygen that rapidly dissociates in water and re- leases a reactive form of oxygen that can oxi- dize cells. It has been suggested that ozone may have antimicrobial efficacy without inducing the development of drug resistance and for this reason it was also used in endodontics. How- ever, the results of the available studies on its effectiveness against endodontic patho gens are inconsistent,39 especially against biofilms. The antibacterial effectiveness of ozone was found not comparable and less than that of NaOCl.39 Alternative antibacterial systems Nanoparticles Nanoparticles are microscopic particles be- tween 1 and 100 nm in size that have antibacte- rial properties and a tendency to induce much lower drug resistance compared with tradi- tional antibiotics. For example, nanoparticles of magnesium oxide, calcium oxide or zinc oxide are bacteriostatic and bactericidal. They gener- ate active oxygen species that are responsible for their antibacterial effect through electro- static interaction between positively charged nanoparticles and negatively charged bacterial cells, resulting in accumulation of a large num- ber of nanoparticles on a bacterial cell mem- brane and a subsequent increase in its permea- bility associated with the loss of its functions. Nanoparticles synthesized from powders of sil- ver,copperoxideorzincoxidearecurrentlyused for their antimicrobial activity. In addition, nanoparticles can alter the chemical and physi- cal 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 endodontics will depend essentially on the manner in which they can be delivered in the most complex root canal anatomy. Bioactiveglass Recently, bioactive glass or bioactive glass-ce- ramics have been a subject of considerable inter- est for endodontic disinfection owing to their an- tibacterial properties, but conflicting results have been obtained.5 Naturalplantextracts A current trend is the use of natural plant ex- tracts,takingadvantageoftheantibacterialactiv- ity of polyphenolic molecules generally used for storing food. These compounds have been found to have poor antibacterial efficacy, but several demonstrate significant ability to reduce the for- mation of biofilms, although the mechanism by which this occurs is not clear.5 Fig.4: Disinfection activated by light to enhance root canal cleaning. Fig.4 22016