title: Compressive Strength of Mineral Trioxide Aggregate with Propylene Glycol.
abstract: BACKGROUND
  The aim of this study was to evaluate the effect of adding propylene glycol (PG) to mineral trioxide aggregate (MTA) liquid with volume ratio of 20% on the compressive strength (CS) of MTA in two time periods (4 and 21 days) after mixing.
  
  
  METHODS
  Four groups of steel cylinders (n=15) with an internal diameter of 3 and a height of 6 mm were prepared and MTA (groups 1 and 2) and MTA+PG (80% MTA liquid+20% PG) (groups 3 and 4) were placed in to the cylinders. In groups 1 and 3 the CS was evaluated after 4 days and in groups 2 and 4 after 21 days. Data were calculated using the two-ways ANOVA. The level of significance was set at 0.05.
  
  
  RESULTS
  The highest (52.22±18.92 MPa) and lowest (4.5±0.67 MPa) of CS was obtained in 21-day MTA samples and 4-day MTA+PG specimen, respectively. The effect of time and PG were significant on the CS (P<0.05). Mixing MTA with PG significantly reduced the CS; but passing the time from 4 to 21 days significantly increased the CS.
  
  
  CONCLUSIONS
  Considering the limitations of this study, PG had a negative effect on CS of MTA.
authors: Dental and Periodontal Research Center, Department of Endodontics, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Negin
authors: N
authors: Ghasemi
authors: Dental and Periodontal Research Center, Department of Endodontics, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Saeed
authors: S
authors: Rahimi
authors: Dental and Periodontal Research Center, Department of Endodontics, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Shahriar
authors: S
authors: Shahi
authors: Department of Endodontics, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Amin
authors: A
authors: Salem Milani
authors: Department of Dental Biomaterials, Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Yashar
authors: Y
authors: Rezaei
authors: Dental School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors: Mahnaz
authors: M
authors: Nobakht
keywords: Compressive Strength; Mineral Trioxide Aggregate; Propylene Glycol