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ePaper created 2015-03-10, 11:16:47 | version 1.33.01
issue 1/2015 — 75Laser Dentistry Article reduction and reduced apical leakage are advantages of this laser and make it viable for endodontic treatment. The principal laser action is photo-thermal. The thermal effect on tissue depends on the irradiation mode and settings. Wang et al.59 irradiated root canals in vitro and demonstrated a maximum tempera- ture increase of 8.1°C using 5W for seven seconds. Similar results were obtained by Da Costa Ribeiro.60 Gutknecht et al.61eval- uatedintra-canaldiodeirradiationwithan output of 1.5W and observed a tempera- ture increase of 7°C in the external sur- faceoftherootusinga980nmdiodelaser atapowersettingof2.5Watacontinuous and chopped mode, and found that the temperature increase never exceeded 47°C, which is considered safe for peri- odontal structures.41 Cleanintra-canaldentinalsurfaceswith sealeddentinaltubules,indicatingmelting and recrystallization, were morphological changes observed at the apical portion of the root after intra-canal diode irra- diation.62 In general, near infra-red wave- lengths, such as 1,064 and 980nm, pro- mote fusion and recrystallization on the dentinal surface, sealing dentinal tubules. The apparent consensus is that diode laserirradiationhasapotentialantibacter- ial effect. In most cases, the effect is di- rectly related to the amount of energy delivered. In a comparative study by Gutknecht et al.,63 an 810 nm diode was ableto reduce bacterial contamination by upto 88.38% with a distal output of 0.6W incontinuouswavemode.A980 nmdiode laser has an efficient antibacterial effect ofanaverageofbetween77to97%inroot canals contaminated with E. faecalis. En- ergy outputs of 1.7, 2.3 and 2.8W were tested. Efficiency was directly related to the amount of energy and dentine thick- ness.64 Er:YAG laser Er:YAG lasers are solid-state lasers with a lasing medium of erbium-doped yttrium aluminium garnet (Er:Y3A15O12). Er:YAG lasers typically emit light with a wave- length of 2,940nm, which is infra-red light. Unlike Nd:YAG lasers, the output of anEr:YAGlaserisstronglyabsorbedbywa- ter because of atomic resonances. The Er:YAG wavelength is well absorbed by harddentaltissue.Thislaserwasapproved fordentalproceduresin1997.Smearlayer removal, canal preparation and apicoec- tomy are indications for endodontic use (Figs. 7a and b). The morphology of a dentinal surface irradiated with an Er:YAG laser is charac- terizedbycleanareasshowingopendenti- naltubules,freeofasmearlayer,inaglob- ularsurface. Bacterial reduction usingthe Er:YAG was observed by Moritz et al.65 Stabholz et al.37 describe a new en- dodontic tip that can be used with an Er:YAG laser system. The tip allows lateral emission of the radiation rather than di- rect emission through a single opening at the far end. It emits through a spiral tip located along the length of the tip. In examining the efficacy of the spiral tip in removing the smearlayer, Stabholz et al.66 found clean intra-canal dentinal wallsfree of a smear layer and debris under SEM evaluation. Photoactivated disinfection PAD is another method of disinfection in endodontics and is based on the principle that photo-activated substances, which are activated bylight of a particularwave- length, bind to target cells. Free radicals are formed, producing a toxic effect to bacteria. Toluidine blue and methylene blueareexamplesofphoto-activatedsub- stances. Toluidine blue is able to kill most oral bacteria. In in vitro studies, PAD has aneffectiveactionagainstphotosensitive bacteriasuchasE.faecalis,Fusobacterium nucleatum, P. Intermedia, Peptostrepto- coccus micros and Actinomycetemcomi- tans.67, 68 On the other hand, Souza et al.,69 evaluating PAD antibacterial effects as a supplementtoinstrumentation/irrigation of canals infected with E. faecalis, did not Fig.6a Fig.6b Fig.7a Fig.7b Fig. 6a Diode 940 nm (Biolase). Fig. 6b Diode 980 nm intra-canal irradiation. Fig. 7a Er:YAG laser (KaVo). Fig. 7b Er, Cr:YSGG laser (Biolase).