Dissolution versus dislodgment of dentin debris by pulsed erbium-doped yttrium aluminum garnet laser-activated endodontic irrigants

The aim of this study was to weigh dissolving versus physical effects of laser-activated irrigation (LAI) when cleaning simulated human root canals. Dentin debris was selected as the composite organic/inorganic substrate. The cleaning effects of plain 3% sodium hypochlorite (NaOCl, proteolytic), plain 9% 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP, decalcifying), or combined 3% NaOCl + 9% HEDP (NaOCl+HEDP, combined effect) were compared to those of deionized water (no dissolving effect on substrate). Properties of test and control solutions were assessed, including their absorption of infrared light and their viscosity. The isthmus of transparent root canal models (n = 22) was filled with dentin debris obtained from bovine tooth roots. Activated irrigation was done on the models in random order in 3 cycles of 30 s each, at 612 mW/18 Hz. The area of removed debris was measured using digital microscopy. The influence of the irrigating solution on debris removal was assessed by one-way ANOVA and Tukey’s HSD, alpha = 0.05. Infrared absorbance spectra were similar between solutions. Density and viscosity increased cumulatively with the solutes under investigation. The combined NaOCl+HEDP solution displayed a significantly (p = 0.002) better cleaning effect than the plain counterparts, which did not remove more debris from the isthmus than water (p>0.05). Under current conditions, the known dissolving effects by NaOCl and HEDP per se did not affect dentin debris removal by LAI, which was mainly due to physical dislodgment of the debris. The enhanced LAI-endorsed cleaning by the combined NaOCl+HEDP irrigant could be related to altered fluid properties and should be explored in further experiments.