The effect of various mixing techniques on the surface microhardness of mineral trioxide aggregate M. H. Nekoofar 1,2 , Z. Aseeley 2 & P. M. H. Dummer 2 1 Department of Endodontics, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran; 2 Endodontology Research Group, School of Dentistry, Cardiff University, Cardiff, UK Abstract Nekoofar MH, Aseeley Z, Dummer PMH. The effect of various mixing techniques on the surface microhardness of mineral trioxide aggregate. International Endodontic Journal, 43, 312–320, 2010. Aim To evaluate the influence of various mixing procedures including ultrasonic vibration, trituration of customized encapsulated mineral trioxide aggregate (MTA) and condensation on the Vickers surface microhardness of MTA. Methodology ProRoot Ò MTA Original, ProRoot Ò MTA (white), MTA-Angelus Ò (grey) and MTA White Angelus Ò (white) were prepared using several mixing techniques including ultrasonic vibration, trituration of customized encapsulated MTA and conventional con- densation. Twelve experimental groups (four materials: three techniques) were evaluated, each with 35 sam- ples. All samples were incubated after preparation and subjected to Vickers surface microhardness testing after 4 and 28 days. Data was were subjected to a two-way anova. Result At 28 days, the surface microhardness value was significantly greater for all experimental groups compared to 4 days after mixing (P < 0.00001). The application of ultrasonic energy to MTA produced significantly higher surface microhardness values com- pared to the other mixing techniques at both 4 and 28 days (P < 0.0001). However, no significant differ- ence existed between condensation and trituration techniques at both time intervals. Regardless of the mixing technique employed, a significant difference (P < 0.0001) was observed in surface microhardness value between all types of MTA apart from between Angelus grey and ProRoot white at both 4 and 28 days, both of which produced the highest values. Conclusion Compared to trituration and condensa- tion techniques, the application of ultrasonic energy to MTA produced a significantly higher surface microhard- ness value at both 4 and 28 days. Irrespective of mixing technique, ProRoot white and Angelus grey had the highest surface microhardness values. Trituration of encapsulated, premeasured MTA and water provides a standardiszed method of mixing that produces MTA slurries with more controllable handling characteristics. Keywords: condensation, mineral trioxide aggregate, mixing technique, trituration, ultrasonic, Vickers sur- face microhardness. Received 7 April 2009; accepted 21 December 2009 Introduction The clinical outcomes of the majority of dental restor- ative procedures are influenced by the chemical and physical properties of dental materials (Main et al. 2004, Behr et al. 2008, Drummond 2008). These properties can be effected by mixing technique (Nomoto & McCabe 2001, Nomoto et al. 2004), delivery system (Hachmeister et al. 2002), exposure to various clinical environments (Vanderweele et al. 2006), storage con- ditions (Roulet 1995) and the ratio of the constituent components (Fridland & Rosado 2003, Behr et al. 2008). Sensitivity to clinical techniques might also affect the optimum performance of materials Correspondence: Dr Mohammed Hossein Nekoofar, School of Dentistry, Cardiff University, Heath Park, Cardiff CF14 4XY, UK (Tel.: +44 29 20742488; e-mail: nekoofar@yahoo.com). doi:10.1111/j.1365-2591.2010.01683.x International Endodontic Journal, 43, 312–320, 2010 ª 2010 International Endodontic Journal 312