Methods: 40 extracted single-rooted human teeth with straight canals that had been extracted for periodontal reasons were collected and stored in the sterile saline until employment in the experiment. The teeth were decoronated to a standard 12 mm root segment using diamond disc. After instrumentation of specimens, the external root surface was sealed with two layers of nail polish to avoid environmental contamination. The apical foramen was subsequently closed with composite material. The teeth were randomly divided into two major groups consisting of indocyanine green solution (ICG) and tolonium chloride solution (TCH) with and without EDTA in their subgroups. Specimens in all groups were grooved longitudinally with a diamond disc and were split in two halves with a stainless steel chisel. The measurements were done by the stereo microscope under 20X magnification in three zones of each specimen and the penetration depth of dye was measured.
Results: The results of this study showed that the mean of lateral penetration depth of ICG (224.04 μm) was significantly (P<0.05) higher than TCH (70.15 μm). Regarding to the influence of EDTA, in ICG group without consideration to the different regions, the usage of EDTA improved the mean of lateral penetration depth of ICG, but this improvement was not statistically significant (P>0.05). However, in the TCH group, the mean of lateral penetration depth of TCH into the lateral wall of the canal was significantly improved by EDTA usage (P=0.004).
Conclusions: Further to the findings of this study, it could be assumed that ICG could kill bacteria in deeper regions of the root canal wall. Therefore, it could be used as an alternative to the tolonium chloride in PDT.