The local structural changes in amorphous calcium phosphate (ACP) based dental composites were studied upon heating using both static, bulk measurement techniques and recently developed ultra-small angle X-ray scattering X-ray photon correlation spectroscopy (USAXS-XPCS), which permits a dynamical approach. While results from static measurements do not show clear signs of structural change, USAXS-XPCS results reveal unambiguous evidence for local structural variations on a similar time scale to that of water loss in the ACP fillers. A thermal-expansion based simulation indicates that thermal behavior alone does not account for the observed dynamics. Instead, the results suggest that changes in the bound water content of ACP affect the composite morphology due to changes in ACP structure.
Citation: ACTA Materialia
Pub Type: Journals
coherent small-angle X-ray scattering, X-ray photon correlation spectroscopy, amorphous calcium phosphate, polymer dental composites, non-equilibrium dynamics, microstructure characterization