Intraoral pH Measurement: A Cool Way to Recognize Stress

In recent years, mental disorders has become serious problem caused by excessive stress. Globally more than 60% of workers are testified to be in stress during work hours. The common diagnostic tools for measuring stress are an electroencephalogram (EEG), body temperature, an electrocardiogram (ECG) and self-questionnaire. Though thee measurement techniques are sensitive enough to identify stress, they are quite complex and poorly suitable for point of care (POC) testing. In addition, salivary alpha amylase measurement is commonly used for stress evaluation. However, it's unsuitable for continuous measurement of the enzyme activity. Fortunately there is a link between the pH and stress levels of the body. Therefore in this study we aim to continuously monitor the pH fluctuation in an oral cavity using mouthpiece pH sensor. Although, electrolyte free Ag/AgIO
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reference electrode method facilitated us to make the miniaturized pH sensor. Initially for calibration experiments were done using standard pH buffer solutions (pH4.01, pH5.00, pH6.00 and pH7,01) using Ag/AgIO
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reference electrode and antimony (Sb) electrode supplied by Chemical Equipment Co., Ltd. (Part Number M 20 E 16002). The observed sensor response is shown in Figure 1 and the sensitivity was around -58.433 mV/pH. Then the electrodes were attached to the mouthpiece device and measured the real time pH fluctuation in mouth by applying noise induced stress. The measurement procedure was at first both electrodes were immersed in a buffer solution for 5 mins, then hearing white noise and finally when no noise is heard. The stress load and non-stress load measurement result is shown in Figure 2. A standard solution voltage values were taken for conversion factor for pH. When no stress load is applied the measurement, there is no serious fluctuation was observed in pH values. On the other hand during white noise hearing, the pH was significantly decreases than the normal value. Hence it is proved that stress levels directly affected the pH values of the saliva. More investigation is underway for conformation.