Objectives: Currently, different materials are used to obdurate tooth root canals. An ideal root canal flling material should have some specifc properties, including biocompatibility, dimensional stability and insolubility.

Materials and Methods: One of the methods to evaluate these materials is to carry out solubility and microhardness tests. To this end, 20 mineral trioxide aggregate (MTA) samples were prepared for solubility test and 60 samples for microhardness test. MTA (Angelus, Brazil) was prepared based on manufacturer’s instructions by mixing the powder and catalyst at a
ratio of 1:1 and was placed in Teflon molds. The samples were stored in a room with 95% relative humidity at 37°C for 390 minutes (3 times longer than the setting time). The solubility of the materials was tested by immersing the samples in distilled water and measuring weight loss at 24-hour and 7-day intervals. The microhardness was determined using Vickers
test before and after immersion in Ringer’s solution at different intervals and the results were compared. 

Results: The results showed that solubility of white MTA after 1 day was similar to that of gray MTA; however, after 7 days, its solubility increased. There were no signifcant differences in microhardness on day 1 and on the subsequent days between white and gray MTA samples (P<0.05). 

Conclusions: There was no signifcant difference in the solubility of white and gray MTA samples at 24-hour interval; however, at 7-day interval, the solubility of white MTA (WMTA) was signifcantly higher than that of grey MTA (GMTA) (with the solubility of both materials being <3%) In addition, there was no signifcant difference in microhardness of white and gray MTA between the frst day and other intervals (P<0.05).