The complex anatomy of root canals in primary teeth makes root canal treatment and canal filling difficult. Root canal filling materials should meet the basic requirements for hermetic filling in terms of their physicochemical properties, such as radiopacity and viscosity, which might be affected by heat.The aim of this study was to investigate the effect of different temperatures on the filling quality and hermetic obturation ability of primary root canal filling pastes.Primary root canal filling pastes containing calcium hydroxide with barium sulphate and calcium hydroxide with iodoform were heated to four different temperatures (4°C, 23°C, 39°C and 55°C). After instrumentation, 80 endodontic blocks were filled with the heat-treated sealers. Digital radiographs were taken and analysed. The results were analyzed using Tukey's HSD, two-way Robust ANOVA, and the Bonferroni test for multiple comparisons.The results of this study, the obturation radiopacity values of calcium hydroxide paste containing barium sulphate showed significant differences at different temperature values. Paste at 4°C showed significantly higher radiopacity (p<0.001). Paste at 55°C showed both significantly higher radiopacity (p<0.001), and the total unfilled area values obtained at 55°C was found to be significantly lower than the other temperatures (p=0.025).It was observed that the preheating process had a positive effect both on the filling quality and hermetic obturation capacity of primary root canal sealants at high temperatures.