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Please cite this article as follows: Bahrololoomi Z, Dadkhah A, Alemrajabi M. The effect of Er:YAG laser irradiation and different concentrations of sodium hypochlorite on shear bond strength of composite to primary teeth's dentin.

Background Bacterial microleakage is an important cause of apical periodontitis and endodontic treatment failure. This study aimed to assess the bacterial microleakage of nano-mineral trioxide aggregate (nano-MTA) as a sealer, Endoseal MTA, and GuttaFlow Bioseal sealers in atmospheric pressure, and simulated underwater diving and aviation conditions. Methods In this in vitro, experimental study, 180 extracted single-rooted teeth were cleaned and shaped, and were then randomly divided into three groups for single-cone obturation using Endoseal MTA, GuttaFlow Bioseal, or nano-MTA as a sealer. Each group was then randomly divided into three subgroups, and subjected to ambient atmospheric pressure, 2 atm pressure (to simulate underwater diving), and 0.5 atm pressure (to simulate aviation) using a custom-made pressure chamber. The teeth then underwent microbial leakage test using Streptococcus mutans (S. mutans), and the percentage of samples showing microleakage was recorded for up to 1 month, and analyzed using the Chi-square test. Results The three sealer groups were significantly different regarding bacterial microleakage (P < 0.05). The nano-MTA group showed significantly higher microleakage after 15 days than the other two groups (P = 0.006). The effect of pressure on bacterial microleakage was not significant in any sealer group (P > 0.05). Conclusion Within the limitations of this in vitro study, it may be concluded that single-cone obturation technique using nano-MTA as a sealer results in lower resistance to bacterial microleakage compared with the use of GuttaFlow Bioseal, and Endoseal MTA. Pressure changes in simulated underwater diving and aviation conditions had no significant effect on bacterial microleakage. Trial Registration Number This is not a human subject research.

Background: This study aimed to assess the cytotoxicity of four commonly used endodontic sealers namely AH Plus, AdSeal, Endoseal MTA, and GuttaFlow Bioseal against human gingival fibroblasts (HGFs). Methods: After culturing the HGFs, they were exposed to the respective sealers in set form and in five different weights, after sterilization. The cytotoxicity of the sealers was evaluated after 1, 3 and 7 days using the methyl thiazolyl tetrazolium (MTT) assay. Data were analyzed by repeated measures ANOVA. Results: After 24 h, all sealers showed low cytotoxicity. However, all sealers in 250 mg and 500 mg weights showed significantly higher cytotoxicity than the negative control group at 72 h, and 7 days (P<0.05) except for AdSeal in 80 mg weight (P>0.05). AH Plus was significantly more cytotoxic than other sealers at 3 and 7 days (P<0.05) while AdSeal had the closest results to the negative control group, and showed significantly higher biocompatibility than other sealers in 250 mg concentration. Conclusion: AdSeal showed the highest biocompatibility while AH Plus had the highest cytotoxicity among the tested sealers. Thus, its application may delay the healing of periapical lesions.

Background: Bacterial microleakage is an important cause of apical periodontitis and failure of endodontic treatment. This study aimed to assess the bacterial microleakage of nano-mineral trioxide aggregate (nano-MTA) as a sealer, Endoseal MTA, and GuttaFlow Bioseal sealers in atmospheric pressure, and simulated underwater diving and aviation conditions. Methods: In this in vitro, experimental study, 180 extracted single-rooted teeth were cleaned and shaped, and were then randomly divided into three groups for single-cone obturation using Endoseal MTA, GuttaFlow Bioseal, or nano-MTA as a sealer. Each group was then randomly divided into three subgroups, and subjected to ambient atmospheric pressure, 2 atm pressure (to simulate underwater diving), and 0.5 atm pressure (to simulate aviation). The teeth then underwent microbial leakage test using Streptococcus mutans (S. mutans), and the percentage of samples showing microleakage was recorded for up to 1 month, and analyzed using the Chi-square test.Results: The three sealer groups were significantly different regarding bacterial microleakage (P<0.05). The nano-MTA group showed significantly higher microleakage after day 15 than the other two groups (P=0.006). The effect of pressure on bacterial microleakage was not significant in any sealer group (P>0.05).Conclusion: Within the limitations of this study, it may be concluded that single-cone obturation technique using nano-MTA as a sealer results in lower resistance to bacterial microleakage compared with the use of GuttaFlow Bioseal, and Endoseal MTA. Pressure changes in simulated underwater diving and aviation conditions had no significant effect on bacterial microleakage. Trial Registration Number: This is not a human subject research.