RESUMEN
The aim of this study was to carry out a microbiological evaluation of sites with and without clinical evidence of moderate and severe periodontitis and their correlation with clinical parameters. A total of 52 disease sites and 10 healthy sites were selected according to clinical criteria. The following clinical indexes were measured for all the sites: plaque index, gingival index, blood on probing, depth on probing and insertion level. Samples of subgingival plaque were collected for culture and for differential counts of microbial morphotypes. In disease sites the most frequently isolated were: Prevotella intermedia/nigrescens (65), Porphyromonas gingivalis (23), Actinobacillus actinomycetemcomitans (23), Fusobacterium nucleatum (10) and Peptostreptococcus sp. (31). The aerobic gram-positive microflora was predominant in healthy sites. Significant differences were observed in microbial morphotypes between healthy and disease sites: cocci 18.71 and 78.90, motile rods 46.12 and 16.70, total spirochetes 26.48 and 2.80, respectively. The presence of motile rods, spirochetes and P. intermedia/nigrescens were the parameters with most sensitivity to suspect periodontal disease. There were significant differences in the subgingival microflora between healthy and disease sites in patients with moderate and severe periodontitis.