Influence of humidity and setting time on the push-out strength of mineral trioxide aggregate obturations

The aim of this study is to assess how a wet environment curing affects the retention characteristics of mineral trioxide aggregate (MTA), and also to determine the time needed for curing. MTA obturations were carried out in perforated dentine slices and cured under different conditions (presence or absence of humidity and several time intervals). The obturations were then subjected to an increasing mechanical strength until they were displaced from the perforations. The pushout strength was determined as the ration of the dislodging force to the MTA-dentine contact surface. The influence of the different curing conditions on the pushout strength was then analyzed for statistical significance. Humidity significantly increased the push-out strength of MTA obturations. The effect of curing time depended on humidity: while in the absence of humidity the push-out strength did not increase after 3 days, in the presence of humidity a lengthening of the curing time up to 21 days produced a moderate increase over and above the large initial increase obtained in the first 3 days.