An In Vitro Comparison of the Setting of MTA With and Without the Application of a Moist Cotton Pellet

AN IN VITRO COMPARISON OF THE SETTING OF MTA WITH AND WITHOUT THE APPLICATION OF A MOIST COTTON PELLET Craig D. Johnson, D.D.S. Marquette University, 2010 Introduction: The purpose of this study was to compare the setting of MTA with and without the application of a moist cotton pellet. Methods: Fifty samples of MTA were mixed according to manufacturer’s instructions, placed with an amalgam carrier, and condensed with a plugger into a custom metal block with a well depth of 3.5 mm. Twenty-five of the MTA samples had a moist cotton pellet placed in contact with MTA mixture and twenty-five MTA samples had no moist cotton pellet in contact with the MTA mixture. The samples were placed in 100% humidity at 37°C and evaluated for penetration resistance with a Vickers microhardness tester every 30 minutes for 6 hours and again at 1 and 3 days. A Gillmore needle was used to test the setting time of the MTA. Statistical analysis was completed using repeated measures ANOVA. Results: MTA without the application of a moist cotton pellet displayed significantly greater penetration resistance for 6 hours and set significantly (P<0.05) faster than MTA with the moist pellet. At 1 and 3 days, however, the MTA with the moist pellet was significantly (P<0.05) harder than the MTA without the moist pellet. Conclusions: Application of a moist cotton pellet on MTA affects setting time and the hardness of the cement.