The Effect of a Setting Accelerator on the Physical and Mechanical Properties of a Fast-set White Portland Cement Mixed with Nano-zirconium Oxide

Objective: This study compared the effects of calcium chloride dihydrate (CaCl2.2H2O) on the physical properties and push-out bond strength of white Mineral Trioxide Aggregate (WMTA) and an experimental Malaysian Portland cement mixed with nano-zirconium oxide (nano-ZrO) [(radiopaque Malaysian Portland cement (RMPC). Mineral Trioxide Aggregate (MTA) was the first calcium silicate cement (CSC) introduced in dentistry, but up to date, it is an expensive cement with long setting time and causes tooth discolouration. Although Portland cement has been introduced as a potential substitute to MTA, it still faces some challenges such as long setting time and lack of sufficient radiopacity.
Methods: Four groups [WMTA, RMPC, fast-set WMTA (FS-WMTA) and fast-set RMPC (FS-RMPC)] were prepared. Initial setting time was evaluated using Vicat apparatus. The pH was measured at seven-day intervals. For discolouration potential, cements were packed in the pulp chamber of 46 extracted maxillary incisors. Spectrophotometric readings were obtained at seven-day intervals, and the rate of colour change (ΔE) was recorded. For the push-out bond strength testing, cements were applied in 48 sectioned root samples, and the test was performed using universal testing machine at crosshead speed of 0.5 mm/min until bond failure. Statistical analysis was done according to the nature of each group of data using SPSS 26.
Results: Addition of CaCl2.2H2O decreased the initial setting times of both RMPC and WMTA significantly (p<0.05). The pH values of FS-WMTA and FS-RMPC were comparable to their non-accelerated counterparts ranging from 10 to 12. Discolouration effect was more obviously observed with WMTA and FS-WMTA with time compared to RMPC formulations. Push-out bond strength of the two materials also showed an increase with the addition of the accelerator, however, only FS-WMTA showed statistically significant difference compared to WMTA (p<0.05).
Conclusion: The addition of CaCl2.2H2O improves the physical and mechanical properties of the newly formulated RMPC and WMTA. The RMPC formulation overcomes the discolouration potential of WMTA. (EEJ-2022-12-155)