Effect of Storage Temperature and Storage Time on the pH and Oxidation–Reduction Potential of Commercial Oral Moisturizers

<b>Background/Objective</b>: The criteria for selecting and managing oral moisturizers have yet to be clearly defined. The purpose of this study was to examine the effects of storage temperature and storage time on the pH and oxidation-reduction potential (ORP) of oral moisturizers. <b>Methods</b>: The pH and ORP of 20 commercially available oral moisturizers stored at 37 °C, 25 °C, and 4 °C were measured immediately after opening (0M) and at 1 month (1M), 3 months (3M), and 6 months (6M) post-opening. The data were analyzed using Fisher's exact test based on the critical pH of enamel and dentin, two-way repeated-measures analysis of variance (ANOVA), and Pearson's correlation analysis. <b>Results</b>: At 0M, 25% of the products had pH values below the critical threshold for enamel, and 75% fell below that for dentin. The distribution of products significantly differed based on critical pH thresholds (<i>p</i> < 0.05). The two-way repeated-measures ANOVA showed that the pH was significantly affected by the storage time (<i>p</i> < 0.05), but not by the storage temperature or its interaction with time. By contrast, ORP was significantly affected by the storage temperature, storage time, and their interaction (<i>p</i> < 0.05). The Pearson's correlation analysis revealed a significant negative correlation between pH and ORP at 4 °C (6M), 25 °C (1M, 3M, 6M), and 37 °C (all time points) (<i>p</i> < 0.05). <b>Conclusions</b>: Many oral moisturizers exhibit acidic pH values, indicating that products with a pH of 6.7 or higher should be selected. Additionally, to minimize degradation, oral moisturizers should be stored at 4 °C and used within 3 months of opening.