The aim of this study was to compare the number of live and dead bacteria attached to, or within, the stratified squamous epithelium lining the tissue side of the gingival sulcus.

A total of 50 patients was examined and classified into healthy or diseased sites according to inflammatory status of the gingival tissue. The surface of stratified squamous epithelium was removed by gentle scraping of the gingival sulcus with curettes. The cells were processed in the laboratory by density-gradient centrifugation to separate the epithelial cells from the loose bacteria and debris. The LIVE/DEAD® BacLight™ Bacterial Viability Kit was applied and the specimens were observed by an epifluorescent microscope and the number of bacteria was counted.

Live and dead bacteria were stained to green and red, irrespectively. Generally, the number of total bacteria in the diseased sites was significantly higher than in the healthy sites. The mean number of detected bacteria in the diseased sites was 58.6±36.0 (red bacteria 10.4±9.2 / green bacteria 48.2±30.5), while it was 1.5±1.7 in the healthy sites (red bacteria 0.1±0.3 / green bacteria 1.4±1.5). The percentage of red bacteria was 17.5±11.2% in the diseased sites and 2.0±5.8% in the healthy sites.

The total number of bacteria in the diseased sites was significantly higher than that of the healthy sites. The ratio and the number of red bacteria were also significantly higher in the diseased sites.