Abstract
A moisture checker of the skin is one type of device that is used to measure the moisture content in the stratum corneum of the skin. Applying the principles of such equipment, an oral moisture checking device was developed in order to measure the moisture content in the oral mucosa. There have been no previous reports of the relationship between the measured values of the oral moisture checking device and the actual moisture content in the oral mucosa. We therefore devised a method in which solid agar processed with varying moisture contents was used as measurement samples, and examined the accuracy of the oral moisture meters via the measurement of these samples.
Materials and methods: Solid agar was produced using powdered agar (standard quantity of moisture content 250 ml per 2g of powder). Maintaining the quantity of 2g of powder and increasing/decreasing the moisture content in 25-ml increments, a total of twelve types of liquid agar were thus prepared with a moisture content varying from 25 to 300 ml. These were then poured into round petri dishes so as to reach a certain volume and solidify at room temperature. Two types of oral moisture checking devices were used for the measurements: Moisture Checker for Mucus (“old type”) and Oral Moisture Checking Device Mucus (“improved type”). A specific sensor cover was attached to each device, and the moisture content of each sample of solid agar was measured three times each.
Results: The measured values showed increases as the contained moisture content increased under 75 ml with both types of the oral moisture checking devices. Furthermore, a close correlation was observed between the moisture content and the measured values, with a significant level 0.1% or less according to the Friedman rank test. In comparisons between the two types of oral moisture checking devices, the improved type showed higher measured values than the old one. The sensitivity was 75% in both types. The specificity was 95% in the old type and 100% in the improved one. The positive predictive value was 75% in the old type and 100% in the improved type. The negative predictive value was 95% in both. Therefore, both oral moisture checking devices were considered to have excellent precision as measuring instruments. However, the ability to accurately predict mouth dryness under clinical conditions was higher for the improved type than for the old type.
