Differentiation of Periodontal Ligament Cell on Hydroxyl- and Carbonated-Apatites

Objectives: The objective of this study is to synthesize carbonated apatite (CA) and to evaluate alkaline phosphatase (ALP) activity of PDL cells on hydroxyapatite (HA) and CA.
Methods: HA and CA powders were synthesized by wet method. Reagents of HA were H₃PO₄ and Ca(OH)₂, and of CA were Na₂HPO₄, Ca(NO₃)₂^.4H₂O, and Na₂CO₃. After the reagents were mixed and stirred for 24h, they were matured for 24h and washed in pure water and dried at 60°C for 5days. Both powders were pressed into a mold at 120MPa to make disks (8mm in diameter, 1mm in thickness) and sintered in a saturated water vapor atmosphere at 1250°C (HA) and in a carbon dioxide atmosphere at 850°C (CA) respectively for 2h. Characterization was done by X-ray Diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). PDL cells from 6-week-old male Wistar rats were isolated and subcultured. Then, ALP activities of PDL cells on those disks were observed at 4 and 7days by ALP assay.
Results: According to the results of characterization, both samples were identified as single-phase hydroxyapatite in XRD, and FTIR results indicated that CO₃ ions were confirmed at 1400cm^-1, 850cm^-1-900cm^-1, and PO₄ ions were confirmed at 1000cm^-1-1100cm^-1, 600cm^-1 for CA specimens. SEM showed no differences between the surfaces of HA and CA disks. The relative carbonate amount was calculated (7.9±0.4wt%). HA disks showed nearly three times-higher ALP activity (57.7±3.4units/mg) than CA disks (19.3±5.1units/μg) at 7days.
Conclusions: CA was successfully synthetized with controlled carbonate amount in a same rage as a bone. Furthermore, in the presence of carbonate, bone formation of PDL cells was less active than in the absence.