Poster V18 - A Novel Nano-Enhanced Electrochemical Tool for Effective Root Canal Irrigation

Introduction: Root Canal Treatment (RCT) is an endodontic procedure performed to preserve severely infected tooth to retain its function. Root canal irrigation is the most important step in RCT for rendering the root canal space free of bacteria. According to an article published by the American Association of Endodontists in October 2023, there has been a rise in the number of endodontic treatments over the past 5 years. Although conventional disinfection methods are successful in most cases and have been used in dental clinics for decades, about 14% of root canal treatments fail due to re-infection. Achieving total disinfection in root canal space is still a major challenge in dentistry. We are developing a novel irrigation approach by combining electrochemistry and nanotechnology to eliminate root canal bacteria effectively.

Materials and

Methods: MG-63 (bone sarcoma) cells were cultured under appropriate conditions and treated with different zinc oxide nanoparticles (ZnO NPs) concentrations for 24 and 72 hours and cell viability was determined using alamarBlue assay after the specified treatment periods. Electrochemical setup and Gamry Instruments Framework software was used to run the experiment. A potential of -5V was applied on MG-63 cells in two samples: 0.9% saline (control) and 5 µg/mL ZnO NPs in 0.9% saline over various time periods (1, 2, 3 mins). The Gamry sequence consists of open circuit potential-1 (OCP-1), potentiostatic scan (PS), and open circuit potential-2 (OCP-2). This was followed by cell viability determination using alamarBlue assay. The experiment was repeated on human gingival fibroblast cells with the same parameters. E. faecalis planktonic and biofilm cultures were then treated using the combination approach, and the number of viable colonies was determined using colony forming units (CFU) plating. For E. faecalis biofilm culture treatment, three controls were used: 5% sodium hypochlorite as positive control, saline or zinc oxide nanoparticles added to biofilm samples which was not electrochemically treated as negative control and the untreated biofilm culture as the control group. SEM analysis was performed for pre-treated and post-treated E. faecalis biofilm culture and was compared for morphological changes. All experiments were done in triplicates.

Results, Conclusions, and Discussions:

Results: Optimum ZnO NPs concentration was chosen to be 5 µg/mL based on the results from cell viability assays. The sample with ZnO NPs generated an increased amount of current compared to the sample with saline when the same potential was applied. A treatment time of 60s showed 80% cell viability in both MG-63 and human gingival fibroblast cell lines. There were no bacterial colonies observed in CFU plates in all treatment groups: saline-1 min, saline-2 min, saline-3min, 5 µg/mL ZnO NPs-1 min, 5 µg/mL ZnO NPs-2 min and 5 µg/mL ZnO NPs-3min. Morphological changes were observed in SEM images in all treatment groups when compared with the non-treated bacterial samples.

Discussion: Root canal re-infections are caused by various bacterial species, of which E. faecalis is the most predominant. E. faecalis is resistant to commonly used antibiotics and can survive nutrient-stringent conditions for a prolonged time. In our study, electrochemical treatment combined with zinc oxide nanoparticles significantly decreased E. faecalis viability while not affecting the cell viability of cells from the surrounding tissues, such as bone and gingival fibroblast cells. This decrease in the viability of E. faecalis and morphological changes in the treatment groups was further confirmed by SEM.

Conclusions: Thus, this combination approach can potentially be used as an alternate or adjunct to the current irrigation techniques to eliminate ~99.99% of bacteria, achieving complete disinfection.

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