title: Effect of varying water-to-powder ratios on the setting expansion of white and gray mineral trioxide aggregate.
abstract: BACKGROUND
  Clinicians commonly mix mineral trioxide aggregate (MTA) to a desired consistency rather than use the recommended amounts of powder and water. The purpose of this in vitro study was to evaluate how varying the water-to-powder (WP) ratio affects the setting expansion of white MTA (WMTA) and gray MTA (GMTA).
  
  
  METHODS
  Eight combinations (n = 5) of WMTA and GMTA were mixed using varying WP ratios. Randomized samples were placed in a linear variable displacement transformer and submerged under Hank's balanced salt solution for 25 hours. Expansion was compared using a 2-way analysis of variance (alpha = 0.05).
  
  
  RESULTS
  Mean percent expansions ranged from 0.058%-0.093% for WMTA and 2.15%-2.56% for GMTA. GMTA expanded significantly more than WMTA at p = .001. No differences in expansion were found between WP ratios (p = .218). No significant interaction was found between the WP ratio and material type (p = .228).
  
  
  CONCLUSIONS
  GMTA expanded significantly more than WMTA; however, varying the WP ratio did not affect the setting expansion.
authors.affiliation: Naval Postgraduate Dental School, Bethesda, Maryland, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Hawley
authors.forename: Terry D
authors.initials: TD
authors.lastname: Webb
authors.forename: Gary G
authors.initials: GG
authors.lastname: Goodell
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D055598:Chemical Phenomena; D004338:Drug Combinations; D006801:Humans; D007552:Isotonic Solutions / Q000737:chemistry; D008422:Materials Testing; D010087:Oxides / Q000737:chemistry*; D011208:Powders; D012387:Root Canal Filling Materials / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; C072670:Hanks Balanced Salt Solution; D007552:Isotonic Solutions; D010087:Oxides; D011208:Powders; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; D014867:Water