A salivary testing instrument has an advantage that the method is simple and can be performed in a short time.
However, it is necessary to verify the factors that affect the reliability of the result, because the device is easy to use and even saliva collection is simple. The aim of this study was to compare the difference of the test results according to the measurement time in order to analyze the time factor of the external variable among the factors that may affect the measurement results of the salivary testing instrument. The relationship between the measured values of the salivary testing instrument to identify the internal variables was analyzed. Saliva was collected from 20 randomly selected patients regardless of age, sex, or diseases. The mean age was 46.6 years, 10 males and 10 females. The saliva collected was directly measured with the salivary testing instrument as group I. The saliva samples were placed in air in a paper cup for 10 minutes, and then measured as group III. Then group I was remeasured after 30 minutes and assigned as group II. Group III was remeasured after 30 minutes and called as group IV. As a result, all of the cariogenic bacteria, acidity, buffer capacity, blood, leukocyte, protein and ammonia, except buffer capacity, showed statistically significant changes in group II and IV. This means that the reliability of the test results is poor if the measurement time is not observed.
Cariogenic bacteria were correlated with leukocyte and protein, buffer capacity was related to acidity, protein, and protein was related to buffer capacity and leukocyte. In conclusion, the result according to the measurement time as the external variable was different, which means that time must be strictly monitored when testing saliva. It is also necessary to take into account the relevance of the correlations between the internal variables and the clinical data.