Antibacterial effect of a hydraulic calcium phosphate cement for dental applications

Calcium hydroxide is currently used in dentistry for endodontic treatment where its main advantage consists of its antibacterial and anti-inflammatory potency. However, it also has some drawbacks such as pulp necrosis, slight solubility, slow and low hardening, and retraction on drying. Since the studies conducted by Brown and Chow (IADR 1983, abst. 207), calcium phosphate-based cements (CPC) have attracted considerable interest in bone reconstruction because of their good osteoconductivity. By mixing calcium bis-dihydrogenphosphate monohydrate (MCPM) and calcium oxide with sodium phosphate buffer in the form of liquid phase, we obtained a CPC with better mechanical properties than calcium hydroxide. The setting reaction produced a mixture of calcium-deficient hydroxyapatite and calcium hydroxide, making this cement more suitable for dental applications than orthopedic ones. The presence of calcium hydroxide a priori confers antibacterial properties to this cement, which were investigated in agar plates (diffusion method) against Streptococcus mutans, Lactobacillus acidophilus, Candida albicans (clinical isolates) and a preparation of polymicrobial flora isolated from dental plaque. The cement samples tested were prepared at calcium-to-phosphate molar ratios (Ca/P) ranging from 1.67 to 2.75. A pure calcium hydroxide paste was used as reference material. Clear and reproducible bacterial growth inhibition was observed for cement samples with Ca/P greater than or equal to 2 against all the microorganisms tested. MCPM-CaO-based cement is therefore a potential candidate for pulp capping and cavity lining.