Variation in periodontal floras.

Statistical analyses indicated (i) that the floras of individual samples taken from the depth of sulci with nickel-plated Morse 00 scalers were highly reproducible and representative of the flora present at any given time, (ii) that the different compositions of floras of different people with similar clinical signs were statistically highly significant, and (iii) that floras of different affected sites may differ significantly in some (two of three) people at any one time or may differ from week to week in other people (one of three). Thus the flora composition of individual sites appears to be in dynamic flux, probably in response either to environmental changes or to host responses. There was no evidence that double sampling per se (two single passes with 00 scalers) changed the composition of the flora. Repeat samples taken after 1 week were slightly more similar to the initial samples than were samples taken after 3 weeks.