The pH value changes in the periodontal pockets.

Many studies have been done of the pH values in periodontal pockets. These studies have suggested that the pH value was influenced by the condition of the surrounding tissue. Thus, the measurement of pH in the periodontal pockets would be effective data to use for diagnosis in periodontal tissue. The sensors which have been used for measuring pH had many disadvantages, however, such as large size, slow response speed, instability in chemical substances, weak physical strength, thermal drift and so on. Therefore, there have been few reliable data on the pH values in periodontal pockets. We developed a new type of pH sensor, which was designed for use in the periodontal pocket. The sensor was made by D.C. reactive sputtering of iridium oxide on solid substances. This sensor was easy to miniaturize, had quick response speed, and was stable with respect to chemical interfere, physical shock, thermal changes, and low electrical resistance. It was used in the present study to measure the pH values in the periodontal pockets of 16 subjects for 7-73 weeks. Our results showed that the pH values in the periodontal pockets differed among the measuring points and were changeable. The pattern of change was similar in the same subject. The pH value changed depending on tooth condition. The salivary pH showed no correlation with that in the periodontal pockets.