Maleic acid as a root canal irrigant- a scoping review

Root canal treatment (RCT) requires thorough removal of the smear layer to ensure proper sealing, reduce microbial contamination, and enhance treatment success. Chelating agents such as ethylenediaminetetraacetic acid (EDTA) are widely used, but they show limitations, especially in the apical third. Maleic acid (MA), a mild organic acid with low pH, has been proposed as a promising alternative due to its superior demineralising and adhesive-enhancing properties.

To evaluate the role of MA in root canal therapy, with emphasis on smear layer removal, antimicrobial efficacy, dentin-related effects, and interactions with dental materials.

The review followed PRISMA-ScR 2018 guidelines and Arksey and O'Malley's six-stage framework. A comprehensive search of PubMed, Scopus, Embase, and Web of Science was conducted up to October 2024. Study eligibility was defined using the PICO framework: (P) human teeth, dentin slices, bacterial cultures, and dental material specimens studied; (I) maleic acid as a root canal irrigant; (C) comparisons with EDTA, sodium hypochlorite, citric acid, and newer chelators; (O) outcomes including smear layer removal, growth factor release, effects on dental materials, antimicrobial efficacy, dentin mineral content, physical and mechanical properties, and bond strength. 71 studies were included.

7% MA was highly effective in smear layer removal, particularly in the apical third, surpassing 17% EDTA and other irrigants. MA enhanced dentin wettability, sealer penetration, and push-out bond strength, and showed superior efficacy in removing calcium hydroxide and intracanal medicaments. It also promoted growth factor release, supporting regenerative potential. While antimicrobial activity was moderate alone, it improved significantly when combined with chlorhexidine or cetrimide. However, MA reduced dentin microhardness and mineral content and negatively impacted calcium silicate-based materials such as mineral trioxide aggregate and Biodentine.

7% MA is a potent root canal irrigant with consistent superiority in apical smear layer removal and unique advantages in adhesion and regeneration. Its demineralising effects highlight the need for controlled application, with shorter conditioning times (1-3 min) optimising outcomes while minimising risks. Overall, MA represents a promising, less cytotoxic alternative to EDTA, but standardised clinical protocols and rigorous in vivo validation are essential for its safe integration into endodontic practice.