Study of a hydraulic DCPA/CaO-based cement for dental applications

Abstract

A CPC was obtained by mixing calcium hydrogenphosphate (DCPA: CaHPO₄) and calcium oxide with either water or sodium phosphate (NaP) buffers. Physical and mechanical properties such as compressive strength (CS), initial (I) and final (F) setting times, cohesion time (T_C), dough time (T_D), swelling time (T_S), dimensional and thermal behavior, injectability (t_100%), antimicrobial properties, setting reaction kinetics, and powder stability over time were investigated by varying different parameters such as liquid-to-powder (L/P) ratio (0.35 to 0.7 mL g⁻¹), molar calcium-to-phosphate (Ca/P) ratio (1.67 to 3), the pH (4, 7 or 9) and the concentration (0 to 1 M) of the NaP buffer. The best results were obtained with the pH 7 NaP buffer at a concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (CS), 6 to 10 min (I), 11 to 15 min (F), 15 to 45 min (T_S), 3 to 12 min (t_100%), 16 min (T_D). This cement expanded during its setting (2.5–7%), and is thus appropriate for tight filling. Finally the cement has antimicrobial activity from Ca/P = 2 and the whole properties were conserved after 8 months storage. Given the mechanical, rheological and antimicrobial properties of this new DCPA/CaO-based cement, its use as root canal sealing or pulp capping material may be considered as similar to calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point.