A New Frontier in Root Canal Disinfection: Evaluating Melatonin as a Potent Intracanal Medicament

Abstract

Background: Persistent endodontic infections are frequently associated with resistant microorganisms such as Enterococcus faecalis and Streptococcus mutans. Although Calcium Hydroxide (Ca(OH)₂) is widely used as an intracanal medicament, its reduced effectiveness against resistant species has encouraged the exploration of newer agents. Melatonin, a hormone with antimicrobial, antioxidant, and immunomodulatory properties, has recently emerged as a potential intracanal medicament. Aim: To compare the antimicrobial efficacy of Melatonin, Calcium Hydroxide, and their 1:1 combination against E. faecalis and S. mutans using the agar well diffusion method. Materials and Methods: Standard strains of E. faecalis (ATCC 29212) and S. mutans (MTCC 497) were cultured in LB broth and standardised to 1×10⁸ CFU/mL. LB agar plates were inoculated, and 6 mm wells were filled with Melatonin, Calcium Hydroxide, the Melatonin + Calcium Hydroxide combination, or DMSO control. Plates were incubated at 37°C for 24 hours, and inhibition zones were measured using a digital Vernier caliper. Data were analysed using SPSS v22.0 with Shapiro–Wilk normality testing and one-way ANOVA with Tukey’s post hoc test (p < 0.05). Results: Melatonin showed greater antimicrobial activity than Calcium Hydroxide against both pathogens. The combination group exhibited the highest inhibition against S. mutans and showed comparable activity to Melatonin against E. faecalis. ANOVA demonstrated significant differences among groups (p < 0.001). Conclusion: Melatonin demonstrated superior antimicrobial efficacy compared with Calcium Hydroxide, while the Melatonin + Calcium Hydroxide combination further enhanced or matched this effect. Melatonin may be a promising alternative or adjunctive intracanal medicament. Further studies using biofilm and dentinal tubule models are recommended.