Modified tricalcium silicate cement formulations with added zirconium oxide

This study aims to investigate the effect of modifying tricalcium silicate (TCS) cements on three key properties by adding ZrO2. TCS powders were prepared by adding ZrO2 at six different concentrations. The powders were mixed with 1 M CaCl2 solution at a 3:1 weight ratio. Biodentine (contains 5 wt.% ZrO2) served as control. To evaluate the potential effect on mechanical properties, the mini-fracture toughness (mini-FT) was measured. Regarding bioactivity, Ca release was assessed using ICP-AES. The component distribution within the cement matrix was evaluated by Feg-SEM/EPMA. Cytotoxicity was assessed using an XTT assay. Adding ZrO2 to TCS did not alter the mini-FT (p = 0.52), which remained in range of that of Biodentine (p = 0.31). Ca release from TSC cements was slightly lower than that from Biodentine at 1 day (p > 0.05). After 1 week, Ca release from TCS 30 and TCS 50 increased to a level that was significantly higher than that from Biodentine (p < 0.05). After 1 month, Ca release all decreased (p < 0.05), yet TCS 0 and TCS 50 released comparable amounts of Ca as at 1 day (p > 0.05). EPMA revealed a more even distribution of ZrO2 within the TCS cements. Particles with an un-reacted core were surrounded by a hydration zone. The 24-, 48-, and 72-h extracts of TCS 50 were the least cytotoxic. ZrO2 can be added to TCS without affecting the mini-FT; Ca release was reduced initially, to reach a prolonged release thereafter; adding ZrO2 made TCS cements more biocompatible. TCS 50 is a promising cement formulation to serve as a biocompatible hydraulic calcium silicate cement.