Scanning electron micrograph and surface hardness of mineral trioxide aggregate in the presence of alkaline pH.
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.
Saghiri
Mohammad Ali
MA
Department of Biomedical Engineering, Islamic Azad University Science and Research Branch, Azad University of Medical Sciences, Tehran, Iran.
Lotfi
Mehrdad
M
Saghiri
Ali Mohammad
AM
Vosoughhosseini
Sepideh
S
Aeinehchi
Mohammad
M
Ranjkesh
Bahram
B
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
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