Photon Induced Photo-Acoustic Streaming (PIPS) and its ability to remove smear layer and debris: a systematic review

This study systematically reviewed the effect of photon induced Photo-Acoustic Streaming (PIPS), compared to Conventional Syringe Irrigation (CSI), on the removal of smear layer and/or debris from root canals. Searches and screening were conducted by two independent reviewers in PubMed/MEDLINE and EMBASE up to August 2025. Eligible studies were in vitro investigations on extracted human teeth evaluating smear layer and/or debris removal using Scanning Electron Microscopy (SEM). A descriptive analysis was performed, and the quality of the studies was assessed by an adapted version of the Joanna Briggs Institute (JBI) checklist. Of 911 screened studies, 14 met the inclusion criteria. PIPS generally showed superior smear layer removal compared with CSI. One study attributed the effect to 20% EDTA rather than the activation technique. Regardless of the irrigant used (distilled water, saline, NaOCl or EDTA), PIPS enhanced smear layer reduction. Removal was more effective in the cervical and middle root thirds than in the apical third. Risk of bias assessment classified 9 articles as medium, 4 as high and 1 as low risk. PIPS appears more effective than CSI in reducing smear layer on root canal walls and can be considered an alternative irrigant activation method. However, heterogeneity among studies limits direct comparisons, highlighting the need for standardized experimental protocols to clarify the effectiveness of PIPS and other techniques. Enhancing smear layer and/or debris removal is critical for disinfection and sealing in endodontics. PIPS shows potential to improve root canal cleanliness compared with CSI.