Objectives: The aim of the current investigation was to assess the rate and magnitude of dentin fluid flow of dentinal surfaces irradiated with neodymium-doped yttrium aluminum garnet (Nd:YAG) laser.

Materials and Methods: Thirty molars were sectioned, mounted and irradiated with Nd:YAG laser at 2 W power settings. The samples were irradiated automatically at individual runs until all dentin surfaces were completely irradiated. Samples were divided to 3 groups, group 1: the flow was for 5 min after irradiation, group 2: flow was measured over 10 min after irradiation and group 3: teeth were immersed in 1% sodium hypochlorite before irradiation then dentinal fluid flow measured over 10 min after irradiation. Fluid flow was measured using fluid flow apparatus. The rate, magnitude and direction of dentin fluid flow were recorded at baseline and after irradiation.

Results: Non-parametric Wilcoxon Signed Ranks repeated-measure t-test and Kruskal-Wallis ANOVA test revealed statistically significant increase in fluid flow after laser treatment. However, no significant differences were found between the groups. The samples demonstrated a baseline outward flow followed by inward flow due to irradiation then followed by increased outward flow.

Conclusions: Nd:YAG laser at 2 W power settings has significantly increased dentinal fluid flow rate. The removal of smear layer with sodium hypochlorite prior to irradiation did not have any effect on the fluid flow rate.