Effects of penetration enhancers on the performance of irrigants for root canal disinfection.

Objectives: To evaluate the effects of penetration enhancers on the physicochemical properties, dentinal tubule penetration, tissue dissolution, and antimicrobial efficacy of root canal irrigants.

Materials and methods: Azone, Triton X-100, or iso-octyl polyoxyethylene ether (JFC-E) (0.1%-5%) were individually added to sodium hypochlorite (NaOCl) or chlorhexidine (CHX) to assess the influence of penetration enhancers. Surface tension, contact angle, viscosity and free available chlorine (FAC) were measured. Dentinal penetration of NaOCl was assessed via discolored area and depth under stereomicroscopy. Soft tissue dissolution was evaluated by changes in bovine pulp tissue weight and volume. The inhibition of protease activity was examined by monitoring matrix metalloproteinase (MMP) gelatinolytic activity via in situ zymography in radicular dentin. Confocal laser scanning microscope (CLSM) was used to analyze multispecies biofilms clearance and bacterial viability.

Results:  0.5% Azone significantly enhanced NaOCl penetration into dentinal tubules (p < 0.05) while maintaining chlorine stability over 90 days. Although tissue dissolution was not significantly improved (p > 0.05), azone-supplemented NaOCl provided deeper infiltration and greater collagen disruption. In situ zymography revealed lower gelatinolytic activity in dentin treated with azone-supplemented NaOCl or CHX (p < 0.05). In biofilm models, azone-supplemented irrigants showed superior bactericidal effects and biofilm reduction compared to irrigants alone (p < 0.05).

Conclusions: Penetration enhancers, particularly azone, effectively enhance the dentinal tubule penetration and antimicrobial performance of endodontic irrigants without negatively affecting their chemical stability.

Clinical relevance: The irrigants supplemented with penetration enhancers may improve disinfection of complex root canal anatomies, contributing to more predictable endodontic outcomes.