The purpose of this study was to investigate the effect of a sodium phosphate dibasic (Na2HPO4) setting accelerator on the properties of white-colored mineral trioxide aggregate (WMTA). Setting times were measured by using a Gilmore needle. Changes in the pH value, diametral tensile strength, and phase composition of WMTA were evaluated. By using a 15% Na2HPO4 solution as a liquid phase mixed with WMTA, the setting time was significantly reduced to 26 minutes rather than the usual 3 hours. The 15% Na2HPO4 promoted WMTA to achieve a maximum diametral tensile strength of 4.9 MPa at an initial 6-hour aging time and 1 MPa for the cement mixed with water. The pH value of the 15% Na2HPO4-mixed cement was changed from an initial 11.0 to a high of 13.2, which was similar to the results using water. The results suggest that the Na2HPO4 solution may be an effective setting accelerator for WMTA.
