The Impact of Silver Nanoparticles' Size on Biofilm Eradication.

Abstract

INTRODUCTION Efficient intracanal disinfection is required for a successful regenerative endodontic treatment. Thus, this study aimed to identify the silver nanoparticles' (NPs) size (AgNPs) with the highest antibiofilm efficacy when mixed with calcium hydroxide [Ca(OH)2] to eradicate an in vitro endodontic biofilm. METHODS The various sizes of AgNPs and mixtures were characterized by scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible spectroscopy. A total of 168 dentin root segments were prepared, sterilized, and inoculated for 3 weeks with Actinomyces naeslundii and Fusobacterium nucleatum. Samples were randomly allocated to 4 experimental groups (n = 28/group): 2 nm AgNPs + 35% Ca(OH)2, 5 nm AgNPs + 35% Ca(OH)2, 10 nm AgNPs + 35% Ca(OH)2, and 35% Ca(OH)2 alone. Samples exposed to saline and triple antibiotic paste (TAP) acted as negative and positive control groups, respectively. After 1 and 2 weeks, samples were stained with LIVE/DEAD BacLight dye and examined under a confocal laser scanning microscope to determine the proportion of dead bacteria. RESULTS The characterization procedure revealed a spherical NP's structure with minor aggregations. Except for Ca(OH)2 group, all groups had significantly higher antibiofilm efficacy at 2 weeks. Both the 10 nm mixture (99.5%) and TAP (99.2%) exhibited the highest antibiofilm efficacy at 2 weeks and were not significantly different from one another (P > .05). No significant difference was noted between the 2 and 5 nm mixtures at 1 week (81% and 84%) and 2 weeks (89% and 91%). CONCLUSION The 10 nm AgNPs (0.02%) + 35% Ca(OH)2 mixture exhibited the highest antibiofilm efficacy at 2 weeks compared to all other mixtures at both observation periods. Interestingly, the 10 nm mixture performed similarly to TAP at 2 weeks. Excluding Ca(OH)2 group, longer application significantly improved the antibiofilm efficacy of all tested medicaments. CLINICAL RELEVANCE The 10 nm AgNPs + 35% Ca(OH)2 mixture revealed promising results as an intracanal medicament in the regenerative endodontic treatment protocol.