title: Microstructural characterization of dental zinc phosphate cements using combined small angle neutron scattering and microfocus X-ray computed tomography.
abstract: To characterize the microstructure of two zinc phosphate cement formulations in order to investigate the role of liquid/solid ratio and composition of powder component, on the developed porosity and, consequently, on compressive strength.
  
  
  
  X-ray powder diffraction with the Rietveld method was used to study the phase composition of zinc oxide powder and cements. Powder component and cement microstructure were investigated with scanning electron microscopy. Small angle neutron scattering (SANS) and microfocus X-ray computed tomography (XmCT) were together employed to characterize porosity and microstructure of dental cements. Compressive strength tests were performed to evaluate their mechanical performance.
  
  
  
  The beneficial effects obtained by the addition of Al, Mg and B to modulate powder reactivity were mitigated by the crystallization of a Zn aluminate phase not involved in the cement setting reaction. Both cements showed spherical pores with a bimodal distribution at the micro/nano-scale. Pores, containing a low density gel-like phase, developed through segregation of liquid during setting. Increasing liquid/solid ratio from 0.378 to 0.571, increased both SANS and XmCT-derived specific surface area (by 56% and 22%, respectively), porosity (XmCT-derived porosity increased from 3.8% to 5.2%), the relative fraction of large pores ≥50μm, decreased compressive strength from 50±3MPa to 39±3MPa, and favored microstructural and compositional inhomogeneities.
  
  
  
  Explain aspects of powder design affecting the setting reaction and, in turn, cement performance, to help in optimizing cement formulation. The mechanism behind development of porosity and specific surface area explains mechanical performance, and processes such as erosion and fluoride release/uptake.
authors.affiliation: Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč, Czechia. Electronic address: viani@itam.cas.cz.
authors.forename: Alberto
authors.initials: A
authors.lastname: Viani
authors.affiliation: Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč, Czechia.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Sotiriadis
authors.affiliation: Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč, Czechia.
authors.forename: Ivana
authors.initials: I
authors.lastname: Kumpová
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5 Area Science Park, 34149 Trieste, Basovizza, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Mancini
authors.affiliation: Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science JCNS, Aussenstelle am MLZ, Lichtenbergstraße 1, 85747 Garching, Germany.
authors.forename: Marie-Sousai
authors.initials: MS
authors.lastname: Appavou
mesh_terms: D001843:Bone Cements; D002130:Calcium Phosphates; D019245:Compressive Strength; D003738:Dental Cements; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053838:Scattering, Small Angle; D014057:Tomography, X-Ray Computed; D014961:X-Ray Diffraction; D015036:Zinc Phosphate Cement
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D003738:Dental Cements; D015036:Zinc Phosphate Cement
keywords: Acid-base cements; Small angle neutron scattering; X-ray micro-computed tomography; X-ray powder diffraction; Zinc oxide; Zinc phosphate cements