Relationship between oxygen tension and subgingival bacterial flora in untreated human periodontal pockets

The predominance of anaerobic bacteria in subgingival plaque samples suggests that the pocket environment is anaerobic. In the present investigation, a small oxygen tension (pO2) electrode was inserted into the base of the pocket and the pO2 was recorded. In addition, the plaque in these pockets was examined culturally and microscopically. The oxygen tension at the bottom of 36 pockets (5 to 10 mm in depth) ranged from 5 to 27 mmHg (1 mmHg congruent to 133.3 Pa) with a mean value of 13.3 mmHg. Moderate pockets (5 and 6 mm) exhibited a mean pO2 of 15.7 mmHg, which was significantly higher than the 12.0 mmHg found in the deeper pockets. The deep pockets had higher percentages of spirochetes and Bacteroides intermedius, whereas the moderate pockets had elevated proportions of Actinomyces naeslundii and Streptococcus mutans. The sites with oxygen tensions equal to or less than 15 mmHg had significantly higher percentages of spirochetes, whereas the microaerophilic Capnocytophaga species were found in pockets with a pO2 greater than 15 mmHg. The presence of bleeding in the pocket was associated with higher proportions of B. intermedius, Capnocytophaga sp., and A. naeslundii. These pO2 readings of periodontal pockets indicated that there is a spectrum of pO2 values which seem to define, in a general way, the microbiological composition of the pocket.