Surface microhardness of three thicknesses of mineral trioxide aggregate in different setting conditions.
OBJECTIVE
This study aimed to compare the surface microhardness of mineral trioxide aggregate (MTA) samples having different thicknesses and exposed to human blood from one side and with or without a moist cotton pellet on the other side.


METHODS
Ninety cylindrical molds with three heights of 2, 4, and 6 mm were fabricated. In group 1 (dry condition), molds with heights of 2, 4, and 6 mm (10 molds of each) were filled with ProRoot MTA (Dentsply Tulsa Dental), and the upper surface of the material was not exposed to any additional moisture. In groups 2 and 3, a distilled water- or phosphate-buffered saline (PBS)-moistened cotton pellet was placed on the upper side of MTA, respectively. The lower side of the molds in all the groups was in contact with human blood-wetted foams. After 4 day, the Vickers microhardness of the upper surface of MTA was measured.


RESULTS
In the dry condition, the 4 and 6 mm-thick MTA samples showed significantly lower microhardness than the 2 mm-thick samples (p = 0.003 and p = 0.001, respectively). However, when a distilled water- or PBS-moistened cotton pellet was placed over the MTA, no significant difference was found between the surface microhardness of samples having the abovementioned three thicknesses of the material (p = 0.210 and p = 0.112, respectively).


CONCLUSIONS
It could be concluded that a moist cotton pellet must be placed over the 4 to 6 mm-thick MTA for better hydration of the material. However, this might not be necessary when 2 mm-thick MTA is used.
Department of Endodontics, School of Dentistry and Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
Noushin
N
Shokouhinejad
School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Leila
L
Jafargholizadeh
Department of Endodontics, School of Dentistry and Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
Mehrfam
M
Khoshkhounejad
Department of Endodontics, School of Dentistry and Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran. ; Endodontology Research Group, School of Dentistry, Cardiff University, Heath Park, Cardiff, UK.
Mohammad Hossein
MH
Nekoofar
Department of Endodontics, School of Dentistry, Oral and Dental Diseases Research Center, Kerman University of Medical Sciences, Kerman, Iran.
Maryam
M
Raoof
Microhardness; Mineral trioxide aggregate; Moist; Setting; Thickness