Tehran University of Medical Sciences
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Mohammad Hossein Nekoofar

Effect of acid-etching procedure on selected physical properties of mineral trioxide aggregate

Authors: Kayahan, M. B. - Nekoofar, M. H. - Kazandag, M. - Canpolat, C. - Malkondu, O. - Kaptan, F. - Dummer, P. M. -
Keywords: Acid Etching, Dental/*methods , *Aluminum Compounds , *Calcium Compounds , Compressive Strength , Crystallization , *Dental Bonding , Dental Stress Analysis , Drug Combinations , Hardness , Hydrogen-Ion Concentration , Materials Testing , Microscopy, Electron, Scanning , *Oxides , *Root Canal Filling Materials , *Silicates , Time Factors ,
Int Endod J, Vol.42, No.11, 2009,Page:1004-14
AIM: To evaluate the effect of acid-etch procedures on the compressive strength and surface microhardness of tooth-coloured mineral trioxide aggregate (MTA). METHODOLOGY: White ProRoot MTA (Dentsply Tulsa Dental) was mixed and packed into cylindrical tubes of 4 mm in diameter and 6 mm in height. Three groups, each of 15 specimens were subjected to an acid-etch procedure either 4, 24 or 96 h after mixing. The compressive strength was measured and compared with unetched control groups. Differences between groups were analysed using the Kruskall-Wallis test. A further batch of cylindrical specimens of 6 mm in diameter and 12 mm in height were prepared for testing surface microhardness. Three groups of 15 specimens were subjected to the acid-etch procedure at either 4, 24 or 96 h following mixing. Data were subjected to one-way anova. Changes in the surface microstructure before and after the acid-etch procedures were analysed using a scanning electron microscope (SEM). RESULTS: There was a general trend for the compressive strength and surface microhardness of specimens to increase with time. In terms of compressive strength, the increase was significant between 4 h and the other time periods for both experimental and control groups (P < 0.0001); however, there was no significant difference between 24 and 96 h. The increase in surface microhardness was significant between 4, 24 and 96 h (P < 0.0001). In addition, there was a significant difference between experimental and control groups at all time periods (P < 0.0001). SEM examination revealed morphological differences between the intact and the etched MTA surfaces. CONCLUSIONS: Acid-etch procedures affected the compressive strength and surface microhardness of ProRoot MTA. This indicates that it may be better to postpone restorative procedures for at least 96 h after mixing MTA. Etching created surface changes that might have the potential to enhance bonding of resinous materials.