## 5 Conclusions  
The long-term storage stability of NW prepared by two-stage electrolysis for 126 days revealed the following:  
1. The higher initial ACCs and non-shaded room temperature storage resulted in significant changes in the pH, ORP, and ACC of NW. 2. NW preparations with initial ACCs of 25-300 mg/L had a pH value of 5.9-7.3 after storage, even under non-shaded conditions at room temperature. In contrast, NW preparations with higher initial ACCs (500 and 1000 mg/L) had a pH lower than the critical pH of human enamel (5.5) during storage, even under shaded and refrigerated conditions. 3. NW with an initial ACC of 25 mg/L, stored under non-shaded conditions at room temperature, exhibited the lowest ACC (5 mg/L) after storage, indicating a decrease in bactericidal efficacy. These results suggest that NW used for intraoral treatment should be prepared with an initial ACC of 25-300 mg/L and stored under shaded and refrigerated conditions. Furthermore, when stored NW is diluted for use, its ACC should be checked and appropriately diluted before each use. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14209264/s1](https://www.mdpi.com/article/10.3390/app14209264/s1)]([https://www.mdpi.com/article/10.3390/app14209264/s1](https://www.mdpi.com/article/10.3390/app14209264/s1)), Supplementary Figure S1: Changes in properties of NW preparations according to different storage conditions during the 126-day storage period, Supplementary Figure S2: Changes in ACC of NW preparations according to different storage conditions during the 126-day storage period, Supplementary Figure S3: Correlation between the pH and ORP of NW preparations after the 126-day storage period, and Supplementary Figure S4: Correlation between the ACC and ORP of NW preparations after the 126-day storage period. Conceptualization, Y.N. and H.N. ; Data curation, Y.N. ; Formal analysis, Y.N. ; Funding acquisition, Y.N. and H.I. ; Investigation, Y.N. and H.I. ; Methodology, Y.N. and H.I. ; Project administration, Y.N. ; Resources, Y.N. and H.I. ; Software, Y.N. and H.N. ; Supervision, Y.N. ; Validation, Y.N., H.I. and H.N. ; Visualization, Y.N. and H.N. ; Writing--original draft, Y.N. ; Writing--review and editing, Y.N., H.I. and H.N. All authors have read and agreed to the published version of the manuscript. This study received no external funding. Not applicable. The data presented in this study are available upon reasonable request from the corresponding author. The authors express their gratitude to Medist Sanite (Wakayama, Japan) for modifying some of the neutral electrolyzed water generators to provide variable, freely available chlorine concentrations for this study. The authors declare no conflicts of interest. * (10) [PERSON]; [PERSON]; [PERSON] Efficacy of Neutral Electrolyzed Water for Inactivation of Human Norovirus. _Appl. Environ. Microbiol._**2017**, _83_, e00653-17. Available online: [[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541222/#:-text=doi%20.20%C22%A0%2010.1128/AEM.00653-17](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541222/#:-text=doi%20.20%C22%A0%2010.1128/AEM.00653-17)]([https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541222/#:-text=doi%20.20%C22%A0%2010.1128/AEM.00653-17](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541222/#:-text=doi%20.20%C22%A0%2010.1128/AEM.00653-17)) (accessed on 2 August 2024). [CrossRef] [PubMed]
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