evaluation of hydroxyl ion diffusion in dentin and injectable forms and a simple powder-water calcium hydroxide paste: an in vitro study

background intra canal medicaments are used to reduce the number of bacteria and reinfection in endodontic procedures. calcium hydroxide was introduced to endodontics by herman as an intracanal antimicrobial agent. objectives the aim of this study was to present an injectable formulation of calcium hydroxide then compare the final ph of this new formulation with metapaste and evaluate the effect of a mixture of calcium hydroxide powder with water on human extracted teeth. patients and methods a total of 49 extracted human single-canal roots without caries and visible microcracks were included in this study. the teeth were decoronated and length of teeth was measured 1 mm anatomic apex. the canals were prepared using step-back technique. a cavity was created in the middle third of the buccal surface of all roots. the teeth were randomly divided into five groups: group a (n = 15): in this group the root canals were filled with a mixture of calcium hydroxide powder and distilled water. group b (n = 15): included roots that were filled with metapaste. group c (n = 15): root canals of this group were filled with new formulation of calcium hydroxide paste. group d (negative control, n = 2): included roots that were filled with a mixture of calcium hydroxide powder and distilled water. group e (positive control, n = 2): root canals of this group were filled with a mixture of calcium hydroxide powder and distilled water. each tooth was immersed in a separate closed container with 4 ml saline for 2 weeks, ph of liquids were measured with an electrical ph meter after 7 and 14 days. the spss software (version 13) was used for data analysis. analysis of variance (anova) and tukey tests were used for the statistical evaluation of results. results there was no significant difference at 7th day between the groups (p = 0.17) but at 14th day, a significant difference was observed between the groups (p = 0.04). conclusions the new formulation of calcium hydroxide with methylcellulose base has slower ionic dissolution, more durability and longevity of alkaline properties in comparison to combination of powder with distilled water and is comparable with other commercial products.