Effects of Various Irrigation Protocols Used in Regenerative Endodontic Procedures on the Migration, Proliferation, and Differentiation of Human Stem Cell from the Apical Papilla

Abstract Objectives The aim of this study was to evaluate the effect of various irrigation protocols in regenerative endodontic procedures (REPS) on the attachment, proliferation, migration, and differentiation of stem cells from the apical papilla (SCAPs). Materials and Methods Dentin specimens from 140 human third molars were irrigated with various protocols; group 1: normal sterile saline (NSS), group 2: EDTA, group 3: EDTA then 5 mL NSS, or group 4: EDTA then 20 mL NSS. The specimens were used in cell assays. For cell proliferation, SCAPs were seeded on dentin and the cell viability on days 1, 3, and 7 was determined using an MTT assay. At day 3, the attached cells’ morphology was observed using SEM and cell migration was investigated using a Transwell-migration assay. The ALP activity and odonto/osteogenic differentiation gene expression was evaluated at day 7, 14, and 21 using an ALP activity assay and RT-qPCR. Results On day 3 and 7, group 4 demonstrated more viable cells than group 1 (p < 0.01). The amount of migrated cells in group 2, 3, and 4 was greater compared with group 1 (p < 0.05). Moreover, SCAP differentiation was similar between groups. Conclusions Irrigating dentin with EDTA alone or with EDTA then NSS promoted SCAP migration. However, a final irrigation with 20 mL NSS after EDTA promoted SCAP proliferation without affecting their differentiation. Clinical relevance When using a blood clot as a scaffold, a final flushing with 20 mL NSS after EDTA could be beneficial for clinical REP protocols.