Release of TGF-β1 into root canals with various final irrigants in regenerative endodontics: an in vitro analysis

To investigate the release of growth factors into the root canal space after various final irrigants during regenerative endodontic procedures. The residual cytotoxic effect of final irrigants on stem cells from the apical papilla (SCAP) was also examined.

To measure the release of TGF-β1, root segments (8 mm long) were irrigated with 1.5% NaOCl followed by 20 mL of final irrigants; Saline, 17% EDTA, 10% citric acid, 10% or 37% phosphoric acid. Specimens were then immersed into culture medium for 24 h and the supernatants were collected to measure TGF-β1 by ELISA. For the cytotoxicity of residual final irrigants, dentine chips (5 × 5 × 1 mm) treated with irrigants as above were placed in the upper chamber of transwell system. Stem cells from the apical papilla were incubated indirectly in the lower chamber for 24 h and MTS assay was performed after 24 h. The surfaces of irrigated root canals were examined for smear layer with a scanning electron microscope (SEM). Log transformation was performed for ELISA data to compare different groups (one-way ANOVA, α = 0.05).

Ten percent citric acid released the greatest amount of TGF-β1 amongst all groups, which was significantly different to 17% EDTA (P < 0.01). All dentine chips irrigated with the irrigants showed no significant difference of cytotoxicity on SCAP compared to nonirrigated dentine (P > 0.05). SEM revealed completely open dentinal tubules in 10% citric acid, whereas 17% EDTA was associated with partially open dentinal tubules.

Ten percent citric acid was effective as a final irrigant for releasing TGF-β1 with good biocompatibility in regenerative endodontics.