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I 07 special _ laser I roots2_2011 lasershavereceivedFDAapprovalforcleaning,shap- ingandenlargingcanals.Afewstudieshavereported positive results for the efficacy of these systems in shaping and enlarging radicular canals. Shoji et al. used an Er:YAG laser system with a conical tip with 80% lateral emission and 20% emission at the tip to enlargeandcleanthecanalsusing10to40mJenergy at 10Hz, obtaining cleaner dentinal surfaces com- pared with traditional rotary techniques.24 In a preliminary study on the effects of the Er:YAG laser equipped with a microprobe with radial emis- sion of 200 to 400µm, Kesler et al. found the laser to have good capability for enlarging and shaping in afasterandimprovedmannercomparedwiththetra- ditionalmethod.TheSEMobservationsdemonstrated a uniformly cleaned dentinal surface at the apex of the coronal portion, with an absence of pulp residue and well-cleaned dentinal tubules.25 Chen presented clinical studies prepared entirely with the Er,Cr:YSGG laser, the first laser to obtain the FDA patent for the entire endodontic procedure (enlarging, clearing and decontaminating), using tips of 400, 320 and 200µm in succession and the crown-down technique at 1.5W and 20Hz (with air/water spray 35/25%).26, 27 Stabholz etal. presented positive results of treat- ment performed entirely using a Er:YAG laser and endodonticlateralemissionmicroprobes.28, 29 Alietal., Matsuoka et al. and Jahan et al. used the Er,Cr:YSGG laser to prepare straight and curved canals, but in these cases, the results of the experimental group wereworsethanthoseofthecontrolgroup.Usingthe Er,Cr:YSGG laser with 200 to 320µm tips at 2W and 20Hz on straight and curved canals, they concluded thatthelaserradiationisabletopreparestraightand curved (less than 10°) canals, while more severely curved canals demonstrated side-effects, such as perforations, burns and canal transportation.21–23 Inamotoetal.investigatedthecuttingabilityandthe morphologicaleffectsofradiationoftheEr:YAGlaser invitro, using 30mJ at 10 and 25Hz with a velocity of extraction of the fibre at 1 and 2mm/seconds, again with positive results.30 Minas et al. reported positive results using the Er,Cr:YSGG laser at 1.5, 1.75 and 2.0W and 20Hz, with water spray.31 The surfaces prepared with the Erbium laser are well cleaned and without smear layer, but often contain ledges, irregularities and charring with the riskofperforationsorapicaltransportation.Ineffect, canal shaping performed by Erbium laser is still a complicated procedure today that can be performed only in large and straight canals, without any partic- ular advantages. Decontaminationoftheendodonticsystem Studies on canal decontamination refer to the action of chemical irrigants (NaClO) commonly used in endodontics, in combination with chelating sub- stances for better cleaning of the dentinal tubules (citricacidandEDTA).OnesuchstudyisthatofBerutti et al., who reported the decontaminating power of NaClOuptoadepthof130µmontheradicularwall.32 Lasers were initially introduced in endodontics in an attempt to increase the decontamination of the endodontic system.2–7 Figs. 9 & 10_SEM images of radiated dentine with Nd:YAG laser (dry, 1.5W, 15 Hz). Note the extensive areas of dentinal melting and bubbles. (Figures 9–16 courtesy of Prof Vasilios Kaitsas, Aristotle University of Thessaloniki, Greece.) Figs. 11 & 12_SEM images of radiated dentine with diode 810nm laser (dry, 1.5W, 15Hz) with 50% ton-toff and 200µm fibre, showing evidence of thermal effects, with detachment and smear layer. Fig. 9 Fig. 10 Fig. 11 Fig. 12