Chitosan Molecular Weight Influences on Endodontic Biofilms and Material Enhancement Strategies

Objectives: The identification of novel antimicrobial agents for use in root canal treatment may provide opportunities to improve treatment outcomes. This study aimed to assess the antimicrobial efficacy of different molecular weights of chitosan (CS), and how modification with CS may impact on the antimicrobial, physico-mechanical and biological properties of Biodentine™, a calcium-silicate-based material used in endodontics. Methods:C. albicans biofilms were treated with either 3% sodium hypochlorite (NaOCl) or a 0.05% or 0.1% CS solution for 5 min. The growth medium was replenished, and cells were re-incubated for additional 72 h. Regrowth of biofilms was assessed using a colorimetric XTT assay. Additionally, multispecies biofilms were established and the regrowth of biofilms on Biodentine discs were quantified following the addition of 0.5 wt% and 1 wt% of CS powder using qPCR. The physico-mechanical and biological properties of the new composite of Biodentine and CS were also evaluated. Results: Viability readings revealed significant initial biofilm inhibitory effects of CS solutions, followed by significant regrowth after 72 h. Upon the addition of CS to Biodentine, significant reductions in multispecies biofilm regrowth were determined. Notably, the antibiofilm activity of CS was found to be increased as the molecular weight decreased. The addition of powdered CS of low molecular weight showed a reduction in the mechanical properties of Biodentine, whereas no detrimental effects on the other material properties were noted. Conclusions: Chitosan may not be useful as an alternative irrigant to NaOCl. Addition of CS to Biodentine represents a potential means of augmenting the antimicrobial activity of Biodentine against persistent microorganisms following endodontic therapy. Despite the reductions in mechanical properties of the material, the new composite still represents a viable material option when material strength and hardness are not critical.