Root canal disinfection remains challenging due to anatomical complexity and the limitations of mechanical instrumentation. Evidence on irrigation is often fragmented and focused on isolated outcomes, limiting clinically integrated protocols. This narrative review provides a clinically oriented interpretation of contemporary irrigation and activation strategies, introducing a substrate-centered perspective emphasizing dentin modification and material interaction. A structured narrative search was conducted in PubMed, Scopus, and Web of Science up to February 2026 using keywords related to irrigants, irrigation protocols, activation techniques, and dentin–material interactions. Studies were selected based on clinical relevance, including complex anatomy, mature biofilms, and realistic irrigation sequences. Irrigation effectiveness is determined by the interplay between irrigant chemistry, fluid dynamics, and activation-mediated distribution within the root canal system, as well as by irrigation-induced dentin modifications influencing the dentin–material interface. Sodium hypochlorite and chelating agents remain central, although their performance depends on delivery and activation. Activation enhances irrigant exchange, biofilm disruption, and penetration into complex regions. Irrigation also induces physicochemical changes in dentin, affecting sealer penetration and interfacial stability. It should not only be considered a disinfection step but also a substrate-conditioning phase linking cleaning to obturation, with implications for treatment predictability and long-term outcomes.
Aliberti et al. (Thu,) studied this question.