title: Effect of acid-etching procedure on selected physical properties of mineral trioxide aggregate.
abstract: OBJECTIVE
  To evaluate the effect of acid-etch procedures on the compressive strength and surface microhardness of tooth-coloured mineral trioxide aggregate (MTA).
  
  
  METHODS
  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.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Yeditepe University, Istanbul, Turkey.
authors.forename: M B
authors.initials: MB
authors.lastname: Kayahan
authors.forename: M H
authors.initials: MH
authors.lastname: Nekoofar
authors.forename: M
authors.initials: M
authors.lastname: Kazandağ
authors.forename: C
authors.initials: C
authors.lastname: Canpolat
authors.forename: O
authors.initials: O
authors.lastname: Malkondu
authors.forename: F
authors.initials: F
authors.lastname: Kaptan
authors.forename: P M H
authors.initials: PM
authors.lastname: Dummer
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D017607:Aluminum Compounds; D017610:Calcium Compounds; D019245:Compressive Strength; D003460:Crystallization; D001840:Dental Bonding; D003799:Dental Stress Analysis; D004338:Drug Combinations; D006244:Hardness; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; D013997:Time Factors
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate