EFFECT OF ER:YAG LASER ON SMEAR LAYER REMOVAL OF EXTRACTED HUMAN TEETH ROOT CANALS: A SEM STUDY

Purpose: the success of endodontic treatment depends on the root canal system being thoroughly cleaned, disinfected and obturated. it has been recognized for many years that root canal instrumentation produces a smear layer that covers the surfaces of prepared canal walls. various methods have been used to remove the smear layer. the purpose of this study was to determine the effectiveness of er:yag laser to remove the smear layer, compared with that of 17% ethylene diamine tetra acetic acid (edta) and 5.25% sodium hypochlorite (naocl). material and methods: twenty one extracted single-rooted human teeth were prepared by a crowndown technique using rotary nickel-titanium files. sodium hypochlorite was used as the intracanal irrigant. the roots were divided randomly into 3 groups of 7 roots each. then the canals were treated with (1) 5ml 17% edta, (2) 5 ml 5.25% sodium hypochlorite (naocl) and (3) er:yag laser. the presence or absence of smear layer in the coronal, middle and apical portion of each canal was examined with a scanning electron microscope. results: there were statistical significant differences between naocl and edta and naocl and er:yag laser groups of the coronal, middle and apical onethirds of the root canals. statistical analysis showed no significant differences of smear layer scores between coronal, middle and apical one-thirds of edta, naocl and er:yag laser groups. conclusion: based on the results of this study, er:yag laser is effective for removal of smear layer from root canals.