title: Compressive strength and surface characterization of glass ionomer cements modified by particles of bioactive glass.
abstract: OBJECTIVE
  The aim of this study was to determine compressive strength, Young's modulus of elasticity, and Vickers' surface hardness, of conventional cure and resin-modified glass ionomer cements after the addition of bioactive glass (BAG) particles into the cements.
  
  
  METHODS
  Experimental glass ionomer cement (GIC)-BAG materials were made by mixing 10- or 30-wt% of BAG particles with conventional cure and resin-modified GIC powders. Materials were processed into cylindrical specimens and immersed in water for 1, 3, 7, 14, 30 and 180 days before mechanical tests. SEM and EDS analysis was used to characterize the changes in surface topography and the main elemental composition.
  
  
  RESULTS
  The compressive strength of the test specimens decreased with the increasing amount of BAG. The compressive strength of resin-modified GIC increased during the immersion, but remained at a lower level than that of the other materials. The conventional cure GIC-based materials had on average 55% higher surface microhardness than the resin-modified materials. In the elemental composition, more Ca was detected in the BAG-containing materials than in the pure GICs. The amount of F was significantly higher (p < 0.001) on all resin-modified materials, being highest on resin-modified GIC with 30-wt% of BAG after 180d of immersion.
  
  
  CONCLUSIONS
  The addition of BAG to GIC compromises the mechanical properties of the materials to some extent. Thus, their clinical use ought to be restricted to applications where their bioactivity can be beneficial, such as root surface fillings and liners in dentistry, and where high compressive strength is not necessarily needed.
authors.affiliation: Department of Prosthetic Dentistry and Biomaterials Research, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, Turku 20520, Finland. helena.yli-urpo@utu.fi
authors.forename: Helena
authors.initials: H
authors.lastname: Yli-Urpo
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Timo
authors.initials: T
authors.lastname: Närhi
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D000704:Analysis of Variance; D002516:Ceramics; D019245:Compressive Strength; D003799:Dental Stress Analysis; D004548:Elasticity; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D007101:Immersion; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties
chemical_list: C022107:Bioglass; D005899:Glass Ionomer Cements