Method: iMTAs contain mainly the same components as original MTA with changed proportions to accelerate setting (4—8 minutes). iMTAs with fluoride (3.5%, group A) and high fluoride (15%, group B) contents were cap-mixed in different powder-to-liquid ratio with diluted polycarboxylic acid, filled into molds (n=3), and immersed in 20ml PBS for 1,7,28 and 56 days. Sample´s surface were analyzed using scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Intensity of apatite (965cm-1) / belite (860cm-1) was measured by Raman spectra. Data were analyzed using One-way ANOVA with Bonferroni correction (alpha=0.05).
Result: In group A, spherical precipitates with peripheral acicular crystallites observed since day1. After 28days, typical “cauliflower” morphologies of hydroxyapatite were formed. After 56days, surface was covered with compact petal-like precipitates. In group B, the globular precipitates were seen since day1, which covered the surface after 7days. After 28and 56days, compact lath-like globular structure covered the surface. EDX showed mainly calcium and phosphate in precipitations with different calcium/phosphate ratios. Raman spectroscopy revealed the formation of apatite layer (965cm-1 band assigned to phosphate) since day1. After 28 days, Raman bands supported the formation of β-type carbonated apatite on iMTAs. Apatite layer thickened in both groups by aging-time. High fluoride version showed significantly higher formed-apatite after 28 and 56 days (P< 0.05).
Conclusion: This study confirmed that apatite is formed over the iMTAs surface. Increased formation of apatite-like layers was observed in iMTA with high fluoride content.