Self-Mineralizing Antibacterial Tissue-Repair (SMART) Varnish to condition dentin in microsurgery

Objectives: To characterize the biomineralization potential, antibacterial properties, biocompatibility and dentin interaction of CS-HA and to assess the effectiveness of a CS-HA containing SMART varnish to seal the root end via biomineralization.
Methods: Experiments were carried out in two phases, beginning with characterization of CS-HA. First, biomineralization potential was characterized using X-ray diffraction and Fourier-transform infrared spectroscopy. Antimicrobial activity and bioactivity of CS-HA were evaluated utilizing E. faecalis and human PDL fibroblasts, respectively. Ultrastructure of the dentin-varnish interface was observed using transmission electron microscopy. In the second phase, a root-end microcrack model was optimized and conditioned with CS-HA. The percentage of root-end covered with the biomineralized layer was analyzed after 0, 6 and 24 hours using scanning electron microscopy (n=6/time point).
Results: CS-HA formed a mineral layer with properties characteristic of hydroxyapatite crystals.It displayed significant antimicrobial activity, showing reduction in both bacterial adherence and bacterial survival (p<0.01). The proliferation, attachment and spreading of PDL fibroblasts on CS-HA-conditioned dentin were enhanced compared to unconditioned dentin (p<0.01). There was a close interaction between the varnish layer and subsurface dentin matrix and the varnish stabilized the underlying collagen. Root-end coverage increased between 0, 6 and 24 hours of incubation (p<0.01), reaching almost 100% of coverage after 24 hours.
Conclusions: SMART varnish effectively sealed the root-end with a biomineralized layer while reducing bacterial load and promoting PDL fibroblast attachment. This could provide optimal conditions to enhance healing following endodontic microsurgery and could help to improve the prognosis when cracks are present.