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DOI

https://doi.org/10.1016/j.jds.2025.09.001

First Page

323

Last Page

332

Abstract

Background/purpose Conventional irrigants such as chlorhexidine and sodium hypochlorite have strong antimicrobial properties but high cytotoxicity, limiting their use in regenerative endodontics. We hypothesized that thymol vapor could provide effective antibacterial activity with lower cytotoxicity. Materials and methods The antimicrobial activity of thymol in both liquid and vapor phases was tested against Enterococcus faecalis, Streptococcus mutans, and Aggregatibacter actinomycetemcomitans using a resin block model simulating curved root canals. The effect of thymol vapor, alone or with mechanical instrumentation, was tested on early-stage biofilms removal. Cytotoxicity was assessed using MTT assays in L-929 fibroblasts and MG-63 osteoblast-like cells, and pro-inflammatory cytokine gene expression (IL-1β, TNF-α, IL-6) was measured via qRT-PCR. Results Thymol exhibited minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.8–1.0 mg/mL in planktonic cultures. In early-stage biofilms models, 10–100 mg/mL liquid thymol and 5.0 mg/mL thymol vapor significantly reduced bacterial viability. Combining 1.0 mg/mL thymol vapor with mechanical instrumentation enhanced early-stage biofilms removal, particularly against E. faecalis. Direct exposure to thymol and chlorhexidine caused significant cytotoxicity, while 1.0 mg/mL vapor showed lower cytotoxic and did not significantly induce pro-inflammatory cytokine genes in L-929 cells. At higher concentrations, MG-63 cells exhibited increased cytokine expression. Conclusion This study is the first to propose thymol vapor for biofilm removal in curved root canal models and to demonstrate its antibacterial activity with lower cytotoxicity than conventional irrigants. Its potential as an adjunct in regenerative endodontics merits further investigation, particularly in relation to immunomodulatory effects.

Publication Date

1-1-2026

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