The quality of smear layer removal in the root canal in in vitro studies (literature review)

Introduction. The treatment of chronic apical periodontitis remains a relevant issue in dentistry. A key stage of endodontic treatment is the removal of the smear layer (SL), which forms during mechanical root canal instrumentation and prevents adequate disinfection. Traditional chelating agents, such as EDTA, have limited effectiveness in the apical third and may damage dentin. Etidronic acid (HEBP) is considered a promising alternative, as it allows continuous chelation simultaneously with antiseptic irrigation. Aim. To evaluate the effectiveness of smear layer removal in the root canal using various chelating agents according to in vitro studies. Materials and methods. A literature review was conducted in the Scopus, PubMed, Web of Science, eLIBRARY.RU, and Google databases for the period 2015–2025 using the following keywords: HEBP, EDTA, etidronate, smear layer, in vitro study. Out of 1,218 identified publications, after excluding duplicates, reviews, clinical cases, and studies with non uniform irrigant activation, 23 full text articles were selected for analysis. Results. EDTA is effective in the coronal and middle thirds but removes the smear layer less effectively in the apical part. Activation (ultrasonic, sonic) improves its performance; however, the risk of reduced dentin strength remains. HEBP, especially in combination with sodium hypochlorite, provides stable smear layer removal throughout the entire canal, including the apical third, and prevents debris accumulation. At the same time, HEBP solutions are less effective in dissolving pulp compared to pure hypochlorite. Conclusions. HEBP in a continuous chelation protocol has advantages over EDTA in terms of cleaning uniformity and dentin safety, but it requires consideration of its impact on the organic tissue dissolution ability of sodium hypochlorite.