Removal efficiency of calcium hydroxide dressing from the root canal

The aim of this study was to investigate whether differences in the composition of calcium hydroxide (Ca(OH)2) preparations influence the removal efficiency of irrigation solutions used in combination with filing of the canal. Three Ca(OH)2 preparations were used: Calxyl, Pulpdent paste, and chemically pure Ca(OH)2 mixed with distilled water. Fifty-one single-rooted extracted human teeth were prepared with a step-back technique and divided into groups A, B, and C. In each group, 15 teeth were assigned to each Ca(OH)2 preparation while the remaining two served as positive and negative controls. Each group of treated teeth was divided into three subgroups of five teeth each: subgroup I--canals were irrigated with saline, filed with a #25 file, and finally flushed with saline; subgroup II--canals were irrigated with NaOCl, filed with a #25 file, and finally flushed with NaOCl; and subgroup III--canals were irrigated with NaOCl, filed with a #25 file, and finally flushed with tetrasodium EDTA. Canal sections were then photographed, and the percentage ratios of Ca(OH)2 coated area to the total canal surface area were calculated by image processing analysis. Results revealed: (a) none of the methods efficiently removed all dressing from the walls, and (b) concentration of the paste used had little effect on the efficacy of the methods applied for the removal of the dressing. Excipients (i.e. methylcellulose contained in Pulpdent) possibly effect retention of Ca(OH)2.