Magnesium phosphate cements for endodontic applications with improved long-term sealing ability

Aim To characterize three radiopaque Magnesium Phosphate Cements (MPCs) developed for endodontic purposes. Methodology Three experimental MPCs containing Bi2O3 were formulated. The experimental cements, which consisted of mixtures of magnesium oxide with different phosphate salts, were characterized for setting time, injectability, porosity, compressive strength and phase composition. The long-term sealing ability of the experimental MPCs applied in single-rooted teeth as root canal filling material or as sealer in combination with gutta-percha was also assessed using a highly sensitive fluid filtration system. A mineral trioxide aggregate (MTA) cement was used as control. Statistical analysis was performed with two- or three-way analysis of variance (anova) and Tukey's test was used for comparisons. Results The addition of 10 wt% Bi2O3 within the composition of the MPCs provided an adequate radiopacity for endodontic applications according to ISO 6876 standard. The reaction products resulting from the MPCs were either struvite (MgNH(4)PO(4)6H(2)O) or an amorphous sodium magnesium phosphate. The porosity of the three MPCs ranged between 4% and 11%. The initial setting time of the experimental cements was between 6 and 9min, attaining high early compressive strength values (17-34 MPa within 2h). All MPC formulations achieved greater sealing ability than MTA (P<0.05) after 3months, which was maintained after 6months for two of the experimental cements (P<0.05). Conclusions These MPCs had adequate handling and mechanical properties and low degradation rates. Furthermore, a stable sealing ability was demonstrated up to 6months when using the cement both as root filling material and as sealer in conjunction with gutta-percha.