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We sought to determine (i) the association of subgingival bacterial profiles to clinical periodontal status in a population with limited access to dental care in Thailand, and (ii) the external validity of our earlier findings from a similar study in rural China. We examined 356 subjects, 30-39 yr old and 50-59 yr old, with respect to clinical periodontal status and subgingival plaque at maximally 14 sites per subject. Checkerboard hybridizations were used to analyse a total of 4343 samples. The prevalence of the 27 species investigated ranged between 87.2% and 100%. Discriminant analysis based on microbial profiles classified correctly 67.5% of all deep (> or = 5 mm) and 64.2% of all shallow sites, and 67.4% of all subjects with and 69.3% of all subjects without > or = 3 deep pockets. High colonization by 'red complex' bacteria was four times as likely (95% Confidence Limits (CL) 2.5-6.6) in subjects with > or = 10 sites with attachment loss of > or = 5 mm, and 4.3 times as likely (95% CL 2.6-7.1) in subjects with > or = 30 such sites. The data confirmed (i) the ubiquitous prevalence of the bacteria investigated in subjects with no regular access to dental care; and (ii) the high odds for periodontal pathology conferred by increased levels of specific periodontal bacteria.

The "checkerboard" Dna-Dna hybridization technology was used to study the epidemiology of 18 microbial species associated with various states of periodontal health and disease, in a sample of 148 Chinese subjects never exposed to systematic dental therapeutic intervention, aged 30 to 39 and 50 to 59 years. Our aims were to: 1) describe the prevalence of these microorganisms; 2) correlate the microbiological and clinical profiles of the subjects; and 3) examine the association between the microbiological variables and the longitudinal changes of periodontal status that occurred over a preceding 10-year period. A maximum of 14 subgingival samples were obtained from each subject-1,864 in all. The frequency of occurrence of the 18 species examined was high in this Chinese population, on both the subject and the tooth site level. However, all species were not found equally capable of reaching high numbers in the subgingival samples and, as a rule, colonized heavily only limited proportions of tooth sites within each mouth. There was a profound increase of certain species such as Porphyromonas gingivalis, Treponema denticola, and Bacteroides forsythus in deep pockets or progressing sites. Multivariate techniques using the subgingival profile could effectively discriminate between deep/shallow pockets and progressing/ stable tooth sites. The microbiological variables showed an enhanced discriminating potential when classifications were performed on the individual subject level. Colonization by P. gingivalis, B. forsythus, Campylobacter rectus, and T. denticola at levels exceeding certain thresholds entailed a significantly increased probability (odds ratios > 4) for an individual subject to harbor deep pockets or progressing tooth sites.