Abstract
Assessment of the physicochemical conditions of the gingival sulci and periodontal pockets was made by measuring the pH and pO2 in 47 sites of 5 patients.
The HIS-FET (Hydrogen Ion Sensitive-Field Effect Transistor), developed by M. Esashi and T. Matsuo, and a Ag/AgCl reference electrode were used to measure the pH. Prior to the measurements, the drift, pH sensitivity, and linearity of the system were examined by standard solutions.
A platinum electrode, covered with celluloseacetate, and a Ag/AgCl electrode were adopted to measure the pO2 of the sulci and pockets. The Pt-electrode was connected to the negative terminal and the reference electrode to the positive terminal of the current source. The pO2 was estimated from the current observed during the reduction process at the tip of the Pt-electrode. The sensitivity and the linearity of the measuring system were also calibrated before the measurements.
The pH was measured at depth of 1mm from the gingival margin and the pO2 measurements were made at the bottom of sulci or pockets.
The results were as follows:
1. The range of pH sensitivity of the HIS-FET electrode was distributed between 44.5 and 51.8mV/pH, and the maximum drift was 0.03pH/min.
2. When the HIS-FET electrode and the Ag/AgCl electrode were repeatedly immersed in the solution, the maximum drift was 1.4mV/90s.
3. Three kinds of buffer solution (i. e. mixture of 0.1N-NaOH and 0.1M-KH2PO4, 1/15 M-KH2PO4 and 1/15M-Na2HPO4, and 0.1M-citric acid and 0.2M-Na2HPO4 respectively) were used to examine pH-linearity. The average sensitivity of the electrode was 51.6mV/pH.
4. The pO2 was recorded by the method based on the polarographic principle. Three kinds of buffer solutions and a solution that contained 5 kinds of salt (MgSO4: 0.06g/l, MgCl2: 0.10g/l, K2HPO4: 0.27g/l, NaHCO3: 2.60g/l, NaCl: 5.80g/l) were examined. A plateau of the reduction current was obtained between -0.55V and -0.75V in those solutions.
5. A linear relationship was obtained between the pO2 concentration and the reduction current. The sensitivity of pO2 was 64.0×10-12A/mmHg (35.0°C).
6. The average pH and the pO2 of the periodontal pockets in patients were 6.35 (S.D.=0.149) and 24.9mmHg (S.D.=17.7mmHg) respectively, and those of the sulci in normal adults were 6.59 (S.D.=0.174) and 36.4mmHg (S.D.=17.1mmHg) respectively. The difference between the average pH value in periodontal pockets and in sulci was significant (p<5%).
