Effect of irrigation protocol with nanoparticles on the physical and mechanical properties of dentin in root canal treatment

The aim of this study is to investigate the effects of final irrigation protocols including the use of chitosan nanoparticles (CSNPs) and crosslinking with genipin (GE) on the microhardness, surface properties and chemical structure of dentin against enzymatic dissolution. CSNPs were synthesized using ionic gelation method and its stability was evaluated by measuring the particle size, polydispersity and zeta-potential. The root canals of 90 extracted single-rooted teeth were prepared and irrigated with sodium hypochlorite (NaOCl). Dentin discs were obtained and divided into groups for use in microhardness (n=15), ATR-FTIR (n=5) and SEM/EDS (n=6) analyses, and kept in the following solutions: (1)NaOCl+Ethylenediaminetetraacetic acid (EDTA), (2)NaOCl+CSNPs, (3)NaOCl+EDTA+CSNPs, (4)NaOCl+CSNPs+GE, (5)NaOCl+EDTA+CSNPs+GE or (6)distilled water. Dentin microhardness was measured before and after treating the specimens with the irrigation protocols. ATR-FTIR and SEM/EDS analyses were performed after the specimens were treated with the irrigation protocols. All analyses were repeated after the discs were soaked in collagenase solution for 24 hours. Data were analyzed statistically (p=0.05). After collagenase application, dentin microhardness decreased in all groups, except for the NaOCl+EDTA+CSNPs+GE group, compared to the values after final irrigation (p<0.05). Microhardness values of NaOCl+EDTA+CSNPs and NaOCl+CSNPs+GE groups after collagenase application were similar to the initial microhardness values (p>0.05). After collagenase, the Amid III/PO4-3 ratio presented no significant change in the NaOCl+EDTA+CSNPs, NaOCl+CSNPs+GE and NaOCl+EDTA+CSNPs+GE groups (p>0, 05), while decreased in other groups (p<0.05). Collagenase did not change the CO3-2/ PO4-3 ratio in the groups (p>0.05). There were no significant changes in the groups in terms of elemental level before and after collagenase application (p>0.05). The use of CSNPs and GE in the final irrigation protocol of root canal treatment can be recommended as they have positive effects on dentin against enzymatic dissolution.