Impact of Types of Moisturizer and Humidity on the Residual Weight and Viscosity of Liquid and Gel Oral Moisturizers.

Purpose: Oral moisturizers need to be selected based on their material properties. The purpose of this study was to investigate the effects of moisturizer type and humidity on the residual weight and viscosity of oral moisturizers.

Materials And Methods: The weight and viscosity of 17 oral moisturizers (7 liquid and 10 gel) at baseline and after 8 hours were measured using an incubator maintained at 37°C at either 85% or 40% relative humidity (RH). The rate of change in weight (RCW) and the rate of change in viscosity (RCV) were calculated. Data were analyzed with two-way analysis of variance (ANOVA) and Scheffe's test to evaluate the effect of the type of moisturizer (liquid or gel) and humidity (85% or 40% RH) on RCW and RCV. Pearson's correlation coefficient was used to evaluate the relationship between RCW and RCV.

Results: Two-way ANOVA results indicated that the type of moisturizer and RH had a significant effect on RCW and RCV (p < 0.05); however, the interaction between them was not significant. The results of multiple comparisons showed that gel moisturizers had a significantly lower RCW and higher RCV than liquid moisturizers (p < 0.05). The RCW and RCV at 40% RH were significantly higher than those at 85% RH (p < 0.05). There was no correlation between RCW and RCV in the liquid moisturizer group, but a significant negative correlation was found in the gel moisturizer group (pp = 0.01).

Conclusion: Because viscosity of gel moisturizers increases as weight decreases, selecting gel moisturizers with a minimal change in weight and viscosity would be preferable in the case of a long-time application and severe dry mouth.