Study on decalcifying and calcifying process of hydroxyapatite hap using structural and optical characterizations

Apatite is expected to be a useful material for artificial bones in surgery and artificial dental roots in dentistry. In particular, studies have recently been conducted into the reconstruction of teeth using Hydroxyapatite (HAp), and several supplements such as gum have become popular for keeping teeth in good condition. However, the decalcifying and calcifying processes are still not well understood. The aim of this research is to study the decalcifying and calcifying mechanisms of HAp. Specifically, the calcifying process was carried out on a sintered pellet of HAp without pores using a Phosphate Acid Maltodextrin (PMD) calcifying promotion agent developed by Oji Paper Co. together with a HEPES (C(8)H(18)N(2)O(4)S) buffer solution, and a natural calcifying liquid which simulates the situation within a human mouth as a reference. SEM, EDX and X-ray analyses were used for the characterization of the structure, morphology and forming elements. Optical characterizations like IR and Raman spectroscopy were also used for the study of physical properties. As a result, it was found that the rate of decalcification can be monitored from the change of the Raman intensity corresponding to the stretching vibrational mode of PO(3-). It was confirmed that the calcification treatment enabled the growth of a precursor material OCP on the HAp pellet for both agents. The rate of growth was dependent on the agent, and it was found that PMD is more effective to grow OCP faster and with high density.