title: Scanning electron micrograph and surface hardness of mineral trioxide aggregate in the presence of alkaline pH.
abstract: BACKGROUND
  The aim of this study was to evaluate morphologic microstructure and surface hardness of white mineral trioxide aggregate (WMTA) after exposure to a range of alkaline environments during hydration.
  
  
  METHODS
  WMTA was mixed and packed into 60 glass tubes. Four groups, each containing 15 tubes, were exposed to pH values of 7.4, 8.4, 9.4, and 10.4, respectively, for 3 days. In 12 tubes in each group, Vickers surface hardness was measured after exposure to alkaline environments. Data were subjected to one-way analysis of variance and a post hoc Tukey test. Three specimens in each group were prepared to be evaluated under a scanning electron microscope using scattered electron (SE) and backscattered electron (BSE) detectors.
  
  
  RESULTS
  The mean surface hardness values +/- standard deviation after exposure to pH values of 7.4, 8.4, 9.4, and 10.4 were 58.28 +/- 8.21, 68.84 +/- 7.19, 67.32 +/- 7.22, and 59.22 +/- 9.14, respectively. The difference between these values was statistically significant (p = 0.000). There were statistically significant differences between pH values of 8.4 and 9.4 and pH values of 7.4 and 10.4 (p > 0.05). The SE detector revealed needle-shaped crystals at pH values of 7.4 and 8.4 and an amorphous microstructure at pH values of 9.4 and 10.4 on WMTA surface. The BSE detector showed more unhydrated structure and pores at pH values of 7.4 and 10.4 compared with pH values of 8.4 and 9.4.
  
  
  CONCLUSIONS
  Surface hardness can be influenced by different alkaline pH values. The BSE detector can reveal more microstructure details of WMTA in conjunction with the SE detector. More porosity and unhydrated structure are observed in WMTA exposed to pH values of 7.4 and 10.4.
authors.affiliation: Department of Biomedical Engineering, Islamic Azad University Science and Research Branch, Azad University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Saghiri
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Lotfi
authors.forename: Ali Mohammad
authors.initials: AM
authors.lastname: Saghiri
authors.forename: Sepideh
authors.initials: S
authors.lastname: Vosoughhosseini
authors.forename: Mohammad
authors.initials: M
authors.lastname: Aeinehchi
authors.forename: Bahram
authors.initials: B
authors.lastname: Ranjkesh
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D017607:Aluminum Compounds / Q000737:chemistry*; D002021:Buffers; D017610:Calcium Compounds / Q000737:chemistry*; D002126:Calcium Hydroxide / Q000737:chemistry; D003461:Crystallography; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D016062:Porosity; D011189:Potassium Chloride / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012542:Scattering, Radiation; D017640:Silicates / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000468:Alkalies; D017607:Aluminum Compounds; D002021:Buffers; D017610:Calcium Compounds; D004338:Drug Combinations; D006878:Hydroxides; D010087:Oxides; D010710:Phosphates; D017680:Potassium Compounds; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; D014867:Water; D012965:Sodium Chloride; D011189:Potassium Chloride; C013216:potassium phosphate; D002126:Calcium Hydroxide; C018279:sodium phosphate; C029943:potassium hydroxide