Effect of PIPS on Properties of Root Canal and Behavior of SCAP

Objectives: The purpose of this study was to evaluate the effect of conventional root canal irrigation optimized with photon induced photoacoustic streaming (PIPS) on smear layer removal, dentin microhardness, attachment morphologyandsurvivalofhuman stem cells of the apical papilla (SCAP) response following dentinconditioning in an organotype root canal model.
Methods: A total of 144 standardized human root segments were randomly divided into 6 groups (n=24 per group) for irrigation: (1)NaOClgroup; (2) NaOCl + EDTA group; (3) NaOCl + PIPS (dH₂O) group; (4) NaOCl + PIPS (EDTA) group; (5) NaOCl + EDTA + PIPS (dH₂O) group; (6) NaOCl + EDTA + PIPS (EDTA) group. All groups were applied with 1.5% NaOCl and 17% EDTA. Then, the root segments from each group were randomly divided into four subgroups(n=6): subgroup 1 for SEM evaluation of dentin cleanliness; subgroup 2 for microhardness of root dentin; subgroup 3 for SEM observation of cell attachment morphology; subgroup 4 for viable SCAP quantification.
Results: The cleanliness score in NaOCl + EDTA + PIPS (EDTA) group was significantly lower than control groups (all p<0.05). Furthermore, the larger number of viable SCAP (all p<0.05), with more stretched cell morphology and longer cytoplasmic processes in NaOCl + EDTA + PIPS (EDTA) group than was founded in the other groups. There was no statistical difference in dentin microhardness among all groups.
Conclusions: Conventional root canal irrigation optimized with PIPS technique (EDTA) for 40s was significantly more effective on smear layer removal without additional dentin microhardness reducing, which created a more cell-friendly dentin conditioning was beneficial for attachment and survival of SCAP.