title: Bioactive glass particulate filler composite: Effect of coupling of fillers and filler loading on some physical properties.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of silanization of biostable and bioactive glass fillers in a polymer matrix on some of the physical properties of the composite.
  
  
  METHODS
  The water absorption, solubility, flexural strength, flexural modulus and toughness of different particulate filler composite resins were studied in vitro. Five different specimen groups were analyzed: A glass-free control, a non-silanized bioactive glass, a silanized bioactive glass, a non-silanized biostable glass and a silanized biostable glass groups. All of these five groups were further divided into sub-groups of dry and water-stored materials, both of them containing groups with 3wt%, 6wt%, 9wt% or 12wt% of glass particles (n=8 per group). The silanization of the glass particles was carried out with 2% of gamma-3-methacryloxyproyltrimethoxysilane (MPS). For the water absorption and solubility tests, the test specimens were stored in water for 60 days, and the percentages of weight change were statistically analyzed. Flexural strength, flexural modulus and toughness values were tested with a three-point bending test and statistically analyzed.
  
  
  RESULTS
  Higher solubility values were observed in non-silanized glass in proportion to the percentage of glass particles. Silanization, on the other hand, decreased the solubility values of both types of glass particles and polymer. While 12wt% non-silanized bioactive glass specimens showed -0.98wt% solubility, 12wt% silanized biostable glass specimens were observed to have only -0.34wt% solubility. The three-point bending results of the dry specimens showed that flexural strength, toughness and flexural modulus decreased in proportion to the increase of glass fillers. The control group presented the highest results (106.6MPa for flexural strength, 335.7kPA for toughness, 3.23GPa for flexural modulus), whereas for flexural strength and toughness, 12wt% of non-silanized biostable glass filler groups presented the lowest (70.3MPa for flexural strength, 111.5kPa for toughness). For flexural modulus on the other hand, 12wt% of silanized biostable glass filler group gave the lowest results (2.57GPa).
  
  
  CONCLUSIONS
  The silanization of glass fillers improved the properties of the glass as well as the properties of the composite. Silanization of bioactive glass may protect the glass from leaching at early stage of water storage.
authors.affiliation: Department of Biomaterials Science & Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, FI-20014 Turku, Finland. Electronic address: onuora@utu.fi.
authors.forename: Onur
authors.initials: O
authors.lastname: Oral
authors.affiliation: Department of Biomaterials Science & Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, FI-20014 Turku, Finland.
authors.forename: Lippo V
authors.initials: LV
authors.lastname: Lassila
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Ege University, Izmir, Turkey.
authors.forename: Ovul
authors.initials: O
authors.lastname: Kumbuloglu
authors.affiliation: Department of Biomaterials Science & Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, FI-20014 Turku, Finland.
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D001672:Biocompatible Materials; D005898:Glass; D008422:Materials Testing
chemical_list: D001672:Biocompatible Materials
keywords: Bioactive glass; Biopolymer; Biostable glass; Composite; Polymers; Silanization