pH changes and calcium ion diffusion from calcium hydroxide dressing materials through root dentin

The purpose of this study was to evaluate Ca²⁺ and OH^- diffusion properties through root dentin by using different calcium hydroxide (CH) dressing materials. Twenty-eight single-rooted teeth were instrumented and external defects were created on the root surface. 17% EDTA was used to eliminate the smear layer. All surfaces except the external defects were sealed, and the teeth were placed in normal saline. Ca²⁺ concentrations and the pH in the saline were determined for 3 days as the control period. After removing the teeth from normal saline, they were filled with: (i) DT Temporary Dressing CH; (ii) CH powder and normal saline; (iii) TempCanal; and (iv) CH points. The teeth were then placed in normal saline, and Ca²⁺ concentrations and pH values were measured at 1, 3, 7, 14, and 28 days. Nonsetting CH pastes gradually released Ca²⁺, whereas this increase was absent from CH points. None of the test materials induced a pH increase in the media during the observation period. This study demonstrated that, when nonsetting CH pastes are applied to the root canal, diffusion of Ca²⁺ without an increase in pH to the surrounding media occurs. This implies that these type of material are more suitable than CH points for treatment of external root resorption.