Published: October 31, 2014
Fan Zhang, Andrew J. Allen, Lyle E. Levine, Mark D. Vaudin, Drago Skrtic, Joseph M. Antonucci, Kathleen M. Hoffman, Anthony A. Giuseppetti, Jan Ilavsky
Amorphous calcium phosphate (ACP) based composites are promising restorative dental materials attributable to ACP's capacity to release calcium and phosphate ions through a complex reaction in which ACP is converted to its crystalline, apatitic form hydroxyapatite. The released calcium and phosphate ions have been shown to repair tooth damage by remineralizing mineral-deficient tooth structure. The mechanism responsible for the conversion of ACP within polymeric composites, however, is not well understood. We performed an investigation of this conversion mechanism in controlled acidic environment with in situ ultra-small angle X-ray scattering based X-ray photon correlation spectroscopy and ex situ X-ray diffraction, as well as other complimentary techniques. We established that this conversion is a two-step process. Initially, ACP undergoes a local microstructural rearrangement without losing its amorphous characters. We established the catalytic role of the acid and found the time scale of this rearrangement strongly depends on the pH of the solution, which agrees with previous findings about ACP without the polymer matrix being present. In the second step, ACP is converted to an apatitic form with the crystallinity of the formed crystallites being poor. Separately, we also confirmed that by modifying the ACP with Zr dopant the rate of ACP conversion to hydroxyapatite can be slowed significantly, which is beneficial for the targeted slow release of functional calcium and phosphate ions from dental composite materials.
Citation: Journal of Biomedical Materials Research Part A
Pub Type: Journals
microstructure characterization, ultra-small-angle X-ray scattering, X-ray photon correlation spectroscopy, amorphous calcium phosphate, dental composites
Created October 31, 2014, Updated February 19, 2017