Tricalcium silicate cements with resins and alternative radiopacifiers.

OBJECTIVE

The objectives of this study were the investigation of the setting mechanisms and characterization of radiopacified tricalcium silicate-based materials mixed with different liquid vehicles.

METHODS

Tricalcium silicate cement replaced with 20% of either zirconium oxide or barium zirconate radiopacifier was investigated. The cements were mixed with water, an epoxy resin, or a light-cured Bis-GMA-based resin. The setting mechanism and characterization of set materials after immersion in Hank's balanced salt solution (HBSS) for 28 days were investigated by scanning electron microscopy of polished specimens and x-ray diffraction analysis. The bioactivity and surface microstructure of cements immersed in HBSS or water were also assessed by similar techniques together with leaching in solution investigated by inductively coupled plasma emission spectroscopy.

RESULTS

The formation of calcium hydroxide as a by-product of cement reaction was affected by the type of radiopacifier and also by the resin vehicle used. Barium zirconate enhanced the formation of calcium hydroxide as indicated by both scanning electron microscopy and x-ray diffraction analysis. The use of resins as vehicles reduced the formation of calcium hydroxide, with the Bis-GMA-based resin being mostly affected. Calcium hydroxide was deposited on the material surface regardless of the type of vehicle used. Formation of beta calcium phosphate was observed on materials containing barium zirconate radiopacifier immersed in HBSS. Inductively coupled plasma emission spectroscopy analysis showed high levels of calcium leached from materials by using water and light-curable resin as mixing vehicles. Barium was leached in solution, with the highest amount from the water-based mixtures. Zirconium leaching was negligible in materials containing zirconium oxide as radiopacifier, but leaching of zirconium was measurable in materials by using barium zirconate with tricalcium silicate.

CONCLUSIONS

The resin type and composition of the radiopacifier affect the calcium releasing ability and bioactivity of tricalcium silicate cements. Barium was leached in solution with barium zirconate radiopacified variants. Light-cured Bis-GMA-based resins did not exhibit cement hydration; however, they encouraged leaching of calcium ions in solution and promoted surface deposition of calcium phosphate.