Smear layer removal and bacteria eradication from tooth root canals by Erbium lasers irradiation

Purpose: The main aim of this study was to perform an integrative review on the effects of Erbium lasers irradiation on bacteria eradication and smear layer removal from dentin surfaces of tooth root canals. Method: A bibliographic search was performed on PubMed using the following search terms: “ultrasonic” AND “Er:YAG” OR “Er,Cr:YSGG” AND “laser” AND “bacteria” OR “smear layer” OR “faecalis” OR “disinfection” AND “root canal” OR “endodontic”. Studies published in the English language within the last 12 years were selected regarding the objective of this study. Results: Previous studies reported a percentage decrease of Enterococcus faecalis at around 99% using an association between Er:YAG or Er,Cr:YSGG laser at 0.5 W and 2.5% NaOCl. Er:YAG laser-assisted irrigation at 0.9 and 1 W showed similar outcomes when compared to ultrasonic activation but revealed slightly higher amount removal of remnant intraradicular debris. Er:YAG or Er,Cr:YSGG laser showed a higher smear layer removal and bacteria eradication compared to solely passive ultrasonic activation although other types of lasers were lesser effective than the ultrasonic activation. Er,Cr:YSGG laser at 0.25 to 1.25 W in association with NaOCl was as effective as ultrasonic activation on the eradication of Enterococcus faecalis and multispecies biofilms. Conclusions: Er:YAG and Er,Cr:YSGG lasers revealed significant bacteria eradication and smear layer removal from tooth root canals. Additionally, energy, irradiance, and mode of laser-assisted irradiation can be improved to achieve optimum results, considering different remnant tooth structures and anatomic variables. The combination of ultrasonic irrigation and laser-assisted irradiation may provide full bacteria eradication and removal of the contaminated smear layer, avoiding further bacteria-infection issues.