Carbon Nanotubes for Improved Performances of Endodontic Sealer

In order to overcome the limitations of current endodontic sealers, especially against resistant bacteria, recent developments in the field of nanotechnology have proved the necessity to reconsider the composition and physico-chemical properties of classical sealers. Nanoparticles with their unique features in terms of small size and high specific surface area, are the best choice for incorporation of antiseptic agents and effective delivery. Multi-walled carbon nanotubes (MWCNTs) encapsulating chlorhexidine (CHX) and colloidal silver nanoparticles (AgNPs) were prepared and incorporated into commercial sealer and investigated in terms of bonding performance to dentin and effectiveness against E. faecalisS. aureus and Candida albicans, which are responsible for the majority of the failures in endodontic treatments. In this context, the challenges related to the long-term biological effects of CHX/AgNPs loaded MWCNTs are discussed.

Development of “smart” endodontic therapeutic agents 

SEM morphological details of CNTs as received from the manufacturer, before (a) and after (b) loading with the mixture CHX/AgNPs (High magnification, 100,000×); (c) photographic image of colloidal CNTs in distilled water (left) compared to colloidal mixture CHX/AgNPs (right).
Ultrastructure details of commercial (a) and modified root canal sealer (c) along with the corresponding EDX spectrum (b,d).
Load–displacement curves (a) recorded on the surface of commercial (black) and modified sealer (red) and the corresponding Young modulus calculation (b)
TGA and DTG thermograms of the modified and commercial sealers.
SEM images (a,c) of interfacial adaptation between sealer and root canal dentine (polished specimens) along with the corresponding EDX spectra (b,d): (a) neat sealer;
(c) CNTs/CHX/AgNPs modified sealer. The transversal section was performed in the middle zone of the root.
Antimicrobial and antifungal effect of different combinations and the mixture CNTs/AgNPs/CHX2% against the tested strains. Data are expressed as average value ± standard deviation of triplicate samples (statistical significance * p < 0.05).

Our original approach, in the context of new generation sealers expecting to have a long-lasting antimicrobial effect, was to demonstrate that the antimicrobial effect of the mixture CNTs/AgNPs/CXH 2% incorporated in commercial sealer, was preserved long enough to efficiently inhibit Gram-positive germs, with excellent results towards E. faecalis in a concentration of 1 mg/mL. The antibacterial and antifungal assay clearly demonstrated a synergic effect of AgNPs, CHX 2% and CNTs with excellent results towards E. faecalis, which is responsible for the primary etiologic factors in pulp and periapical lesions.

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