Disinfection efficacy of photon-induced photoacoustic streaming on root canals infected with Enterococcus faecalis: an ex vivo study

Background: In 2010, one of the authors proposed that lasers could be used to enhance the decontaminating action of sodium hypochlorite (NaOCl). The authors conducted a study to compare the disinfection efficacy of laser-activated irrigation (LAI) by using a photon-induced photoacoustic streaming (PIPS) tip with conventional irrigation and specifically LAI's ability to remove bacterial film formed on root canal walls. Methods: The authors shaped 26 human anterior teeth to a master apical file size of International Organization for Standardization 25/06 (size 25 tip and size .06 taper) and then sterilized the teeth, infected them with Enterococcus faecalis and incubated them for four weeks. The authors used two irrigation protocols. Group A received two cycles of 30 seconds each of 5 percent NaOCl laser activation and one cycle of 30 seconds with laser activation involving the use of 17 percent ethylenediaminetetraacetic acid (EDTA). The erbium:yttrium-aluminumgarnet (Er:YAG) laser's settings were 20 millijoules, 15 hertz, 50-microsecond pulse duration, and it had a 600-micrometer PIPS tip. Group B received two cycles of 30 seconds each of 5 percent NaOCl and 17 percent EDTA irrigation alone, delivered via a syringe with a 25-gauge needle. Results: The authors found that group A had significantly better disinfection compared with group B (P < .05). The results of cultures obtained after 48 hours showed that disinfection was maintained better in group A compared with group B (P < .0001). Scanning electron microscopic images showed absence of bacterial biofilm remaining after LAI using PIPS. Conclusions: Er:YAG laser activation of 5 percent NaOCl and 17 percent EDTA was more effective than conventional irrigation for eradicating E. faecalis and preventing new bacterial growth ex vivo. Additional clinical studies are needed to clarify the effect on endodontic treatment outcomes. Practical Implications. PIPS appears to be effective in enhancing the effect of the irrigants commonly used in endodontics