title: Effects of various mixing techniques on physical properties of white mineral trioxide aggregate.
abstract: BACKGROUND
  The aim of this study was to evaluate the effects of three different mixing techniques on surface microhardness, initial setting time, and phase formation of white mineral trioxide aggregate.
  
  
  METHODS
  Twenty-one cylindrical glass tubes were selected and divided into three groups of seven in each (n = 7). White mineral trioxide aggregate (WMTA) in groups A, B, and C were mixed by conventional, trituration, and ultrasonic techniques, respectively. Cements were mixed and packed into the glass tubes and incubated at 37°C for 3 days. After incubation, samples were subjected to microhardness evaluation, and four specimens from each group were prepared and observed under a scanning electron microscopy and X-ray diffraction. For setting time assessment, WMTA was mixed in three parts again, and Gilmore needle test was performed until the initial setting time of cement. Data were analyzed by one-way anova and post hoc Tukey's test.
  
  
  RESULTS
  Samples mixed by trituration technique significantly showed the highest microhardness (P < 0.001) and the lowest setting time, while the ultrasonically mixed specimens significantly revealed the highest setting time in comparison with other groups (P < 0.001). Samples mixed by trituration technique showed the highest uniformity in the bulk and highest amount of hydrated calcium silicate (CS) phases, while the lowest value was observed in ultrasonically mixed cements, which also showed the highest amount of anhydrated CS phases.
  
  
  CONCLUSIONS
  Trituration and conventional techniques were more suitable mixing methods for mineral trioxide aggregate in comparison with ultrasonic technique. Trituration resulted in better hydration and crystallization, which prevents clustering of powder and reduces voids and setting time of mixed cement.
authors.affiliation: Research Associate Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public health, Madison, WI; Kamal Asgar Research Center, Encino, CA.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Saghiri
authors.forename: Franklin
authors.initials: F
authors.lastname: Garcia-Godoy
authors.forename: James L
authors.initials: JL
authors.lastname: Gutmann
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Lotfi
authors.forename: Armen
authors.initials: A
authors.lastname: Asatourian
mesh_terms: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D008855:Microscopy, Electron, Scanning; D010087:Oxides; D017640:Silicates; D014961:X-Ray Diffraction
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D017640:Silicates; C086631:mineral trioxide aggregate
keywords: Mineral trioxide aggregate; mixing technique; setting time; trituration; ultrasonic