Relative distribution of bacteria at clinically healthy and periodontally diseased sites in humans*

Abstract

Abstract Samples of subgingival bacteria were collected with a clean curette from two relatively normal and two periodontally diseased sites in each of 12 patients with advanced periodontal disease. The samples were suspended in physiologic saline containing 1 % gelatin and examined within 1 hour by darkfield microscopy. From 100‐200 bacteria were classified on a percentage basis into one of the following categories: (1) coccoid cells, (2) straight rods, (3) filaments, (4) fusiforms, (5) curved rods, (6) small spirochetes, (7) medium‐sized spirochetes, (8) large spirochetes, and (9) motile rods. For each area sampled the following clinical criteria were also recorded: (1) Gingival Index, (2) Plaque Index, (3) probing depth and (4) gingival fluid flow. For each patient separate mean values were calculated for the normal and the diseased sites. The results indicated that significant differences existed in the microbial flora of clinically normal and diseased sites using a paired t‐test comparison (2α= 0.001), with coccoid cells more predominant at normal sites (74.3 % vs. 22.3 %), while at diseased sites motile rods were more frequent (12.7 % vs. 0.3 %), as well as curved rods (1.7 % vs. 0 %), small spirochetes (12.6 % vs. 1.1 %), medium‐sized spirochetes (18.5 % vs. 0.5 %) and large spirochetes (6.7 % vs. 0.2 %). The ratio of motile to non‐motile cells in the normal was 1:49, whereas at diseased sites the ratio was in the vicinity of 1:1. These results clearly show that a different flora is associated with healthy and periodontally diseased sites in the same patient population and that these differences can be detected by means of a technique which is simple and readily adaptable to a clinical setting. The data obtained in this fashion may be useful in monitoring the effect of various treatment modalities on the periodontal flora and possibly in determining the presence or absence of active disease.