title: The effect of condensation pressure on selected physical properties of mineral trioxide aggregate.
abstract: OBJECTIVE
  To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA).
  
  
  METHODS
  White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mm in height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel.
  
  
  RESULTS
  A trend was observed for higher condensation pressures to produce lower surface hardness values. A condensation pressure of 8.88 MPa produced specimens with significantly lower values in terms of surface hardness than other groups (P<0.001). A condensation pressure of 1.68 MPa conferred the maximum compressive strength; however, it was not statistically different. Higher condensation pressures resulted in fewer voids and microchannels when analysed with SEM. In specimens prepared with lower condensation pressures distinctive crystalline structures were observed. They tended to appear around microchannels.
  
  
  CONCLUSIONS
  Condensation pressure may affect the strength and hardness of MTA. Use of controlled condensation pressure in sample preparation for future studies is suggested.
authors: Endodontology Research Group, School of Dentistry, Cardiff University, Cardiff, UK. nekoofar@yahoo.com
authors: M H
authors: MH
authors: Nekoofar
authors: G
authors: G
authors: Adusei
authors: M S
authors: MS
authors: Sheykhrezae
authors: S J
authors: SJ
authors: Hayes
authors: S T
authors: ST
authors: Bryant
authors: P M H
authors: PM
authors: Dummer
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D019245:Compressive Strength; D003460:Crystallization; D004338:Drug Combinations; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry*; D011076:Polycarboxylate Cement; D016062:Porosity; D011312:Pressure; D012387:Root Canal Filling Materials / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D011076:Polycarboxylate Cement; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; C005506:polycarbonate