Synergistic effect of Er: YAG laser irradiation in combination with chlorhexidine on the viability of enterococcus faecalis: An in vitro study

Objective: This study aimed to examine the potential synergistic effect of laser and chlorhexidine (CHX) applications on the growth of Enterococcus faecalis. Background data: CHX has been recommended for root canal irrigation because of its antibacterial properties. Er:YAG 2.94μm laser irradiation was shown to be beneficial in disinfecting infected root canals. Producing minimal side effects is the goal of any clinical procedure. One means of achieving this is via a synergistic effect caused by simultaneously introducing two applications with reduced dosages, with no compromise on their biological effect. Methods: Bacterial suspensions of E. faecalis supplemented with 0.01-0.0001% v/v CHX solutions were lased at energy levels between 300 and 500mJ. Bacterial growth was continuously monitored for 18h using a GENios apparatus. Results: Laser irradiation between 350 and 500mJ delayed initiation of bacterial growth for 6h. A concentration of 0.0001% CHX did not delay bacteria growth. However, a combination of 0.0001% CHX and laser irradiation had a synergistic effect on bacterial growth. A maximal inhibition period of bacterial growth was observed at energy levels of 500mJ with 0.0001% CHX. Conclusions: Laser combined with CHX has a synergistic effect in killing E. faecalis. A combined regimen of a low concentration of CHX with laser irradiation was found to be a potential means of inhibiting bacterial growth.