Apatite Formation on Mineral Trioxide Aggregates in Simulated Body Fluid

Methods: White MTA (PROROOT MTA: Tulsa Dental, Tulsa, OK, USA) was used in this study. Hand-mixed MTA paste was prepared as a disc having an diameter of 6 mm and height of 2 mm. After setting, the disc samples were soaked in SBF at 37°C for 2 and 4 weeks (n=3). Surface morphology of the specimen was observed by FE-SEM, and constituent elements of the deposits were semi-quantitatively analyzed by EDS. Ca/P molar ratios were normalized to the measured data of stoichiometric hydroxyapatite (HA). Characterization of the deposits before and after heating at 1,000°C was performed by FTIR and XRD.

Results: SEM images and EDS analysis showed that a layer was formed on the MTA surface and the deposits were identified as calcium phosphate with crystallinity (Ca/P molar ratio =1.45) lower than that of HA =1.67. FTIR analysis revealed CO₃^2- bands characteristic of B-type carbonated apatite that were detected in the 1420, 1458 and 874 cm^-1 regions before heating. Although the XRD patterns of the deposits before heating showed the broad peaks assigned to apatite with low crystallinity, those after heating showed sharp peaks due to HA and b-TCP. These XRD results were in good agreement with those of the FTIR and EDS studies.

Conclusion: The deposits formed on the surface of MTA after soaking in SBF were characterized as calcium-deficient B-type carbonated apatite having low crystallinity and Ca/P = 1.45.