The Potential of Cocos nucifera Endocarp Carbon as an Adjunctive Root Canal Irrigant for Dentin Protection and Antibacterial Effects

Enterococcus faecalis is a key pathogen in persistent endodontic infections, known for its resistance to conventional antimicrobial agents, including irrigants. Biocompatible alternatives that preserve dentin collagen are increasingly sought in root canal therapy. This study evaluated the antibacterial efficacy and dentin-preserving ability of coconut shell–derived activated carbon as an irrigant against E. faecalis. An ex vivo model using human premolars was infected with E. faecalis (ATCC 29212) for 21 days. Samples were treated with activated carbon (1:10, 1:20, 1:30), saline, or conventional irrigants (2% CHX, 17% EDTA, 2.5% NaOCl). Antibacterial activity was assessed via inhibition zones, CFU/mL, and OD600. Calcium ion release and hydroxyproline assays were used to evaluate demineralization and collagen degradation. SEM and FTIR (amide I and III) were used to assess the dentin structure and collagen integrity. Activated carbon 1:10 showed potent antibacterial activity (inhibition zone: 17.2 ± 0.4 mm) and CFU/mL reduction comparable to CHX. It had the lowest calcium release (3.9 ± 0.4 ppm) and hydroxyproline levels (4.2 ± 0.3 µg/mL), indicating minimal dentin damage. SEM and FTIR confirmed structural preservation. EDTA and NaOCl caused significant degradation of collagen. Coconut shell–derived activated carbon at a 1:10 concentration effectively inhibits E. faecalis while preserving dentin collagen, highlighting its novelty as a sustainable and biocompatible irrigant with potential clinical implications in root canal therapy.