High-pH Environment-inducing Agents Dressed in Liquid Medium Cause the Change of Lipopolysaccharide Concentration

<p> Purpose: Lipopolysaccharides (LPS) have been found in abscesses in cases of apical periodontitis, and are believed to be a factor contributing to periapical disease becoming intractable. It has been reported that LPS break down in environments with a high pH. There are many materials on the market with different bases and additives that induce a high-pH environment, but the effects of these materials on LPS have not been clarified. The aim of the present study was to investigate changes in pH of various materials that induce a high-pH environment and to examine the effects on LPS concentration.</p><p> Materials and methods: Five types of high pH-inducing materials were used in this experiment: CALVITAL (soft: CV-L group, hard: CV-P group), CALCIPEX PLANE Ⅱ (Cal group), Vitapex (Vit group), Bio-C Repair (Bio group), and ProRoot MTA (MTA group). Changes in the pH of the liquid culture medium were evaluated by measuring the pH of the supernatant at 1 h, 12 h, 1 day, and 3 days after addition of the high pH-inducing material. Changes in LPS concentration were measured using LPS originating from Escherichia coli. The concentration of LPS in the culture medium was set at 1,000 ng/mL, and the concentration of LPS remaining in the liquid culture medium 3 days after addition was measured by EndoLISA.</p><p> Results: High pH values were found in the CV-L group, CV-P group, Cal group, and MTA group 1 h after the different high pH-inducing materials were immersed in the liquid culture medium. The CV-P group and the CV-L group showed significantly higher pH at 12 h following immersion, and the Cal group showed significantly lower values than the CV-L group and the Vit group at 1 day following immersion. On the 3rd day, the final measurement day, the Vit group showed significantly higher pH than all other groups except the CV-P group. The remaining concentration of LPS was high in the Cal group and low in the CV-P group, but there were no significant differences between any of the groups.</p><p> Conclusion: The pH environment varied with the amount of free hydroxyl groups, depending on the composition of the material, and the concentration of LPS decreased with increasing pH. Calvital, a calcium hydroxide preparation kneaded to a somewhat firm consistency, indicated the possibility of reducing LPS.</p>