Calcium hydroxide inhibits substrate adherence capacity of macrophages.

The purpose of this study was to investigate the effect of calcium hydroxide on substrate adherence capacity of rat inflammatory macrophages to determine if calcium hydroxide can alter macrophage function. Inflammatory macrophages were obtained from Wistar rats and resuspended in RPMI-1640 medium. Substrate adherence capacity assays were carried out in Eppendorf tubes for 15 min of incubation at 37 degrees C in a humidified atmosphere of 5% CO2. The adherence index (AI) was calculated. Results showed that calcium hydroxide decreased substrate adherence capacity of inflammatory macrophages in a time and dose-dependent manner. The lowest calcium hydroxide concentration that caused a significant inhibition of AI was 1 mM (p < 0.05), and the concentration of calcium hydroxide that caused half-maximal inhibition (IC50) was 1.54 mM (p < 0.01). We conclude that calcium hydroxide decreased substrate adherence capacity of macrophages. When adhesion as the first step in the phagocytic process and in antigen presentation is taken into account, calcium hydroxide could inhibit macrophage function and reduce inflammatory reactions in periapical tissues or in dental pulp when it is used in root-canals therapy or in direct pulp capping and pulpotomy, respectively. Moreover, this effect could explain, at least in part, the mineralized tissue-inducing property of calcium hydroxide.