A Novel Self-Mineralizing Antibacterial Tissue Repair Varnish to Condition Root-end Dentin in Endodontic Microsurgery

Introduction: A novel 2-part varnish system containing chitosan nanoparticles (part 1) and chitosan-grafted hydroxyapatite precursor nanocomplex (part 2) was developed to condition the root-end dentin using the principle of biomineralization while rendering both antimicrobial efficacy and bioactivity. This in vitro study aimed to characterize and assess the effectiveness of the chitosan nanoparticles and chitosan-grafted hydroxyapatite precursor nanocomplex containing self-mineralizing antibacterial tissue repair varnish to condition as well as seal root-end dentin during endodontic microsurgery. Methods: In phase 1, the antibacterial properties and cellular response of the varnish were characterized. The antibacterial activity and cellular responses were evaluated using Enterococcus faecalis and periodontal ligament (PDL) fibroblasts, respectively. In phase 2, a resected root-end model was used to apply the 2-part varnish and examine the dentin-varnish interface using transmission electron micro-scopy. The percentage of root end sealed with time was determined using scanning electron microscopy (n 5 6/time point). Statistical analysis was performed using 1-way analysis of variance where applicable. Results: The part 1 and 2 of the varnish displayed significant antibacterial activity and reduced bacterial adherence/survival (P < .01). The attachment and spreading of PDL fibroblasts on the varnish-conditioned dentin was enhanced compared with unconditioned dentin (P < .01). In the resected root-end model, the 2-part varnish displayed a biomineralized varnish layer with close interaction with the subsurface dentin. Root-end coverage with the biomineralized layer increased with incubation time (P < .01), reaching approximately 95% coverage after 24 hours. Conclusions: The 2-part varnish system effectively conditioned/sealed the root end with a biomineralized layer while reducing bacterial load and promoting PDL fibroblast attachment. This therapeutic modification of root-end dentin could provide optimal conditions to enhance healing and improve prognosis in teeth with root-end cracks after endodontic microsurgery. (J Endod 2021;47:939-946.)