THE APICAL BORDER PLAQUE IN SEVERE PERIODONTITIS - AN ULTRASTRUCTURAL-STUDY

THIS STUDY CONCERNS THE APICAL BORDER (AB) plaque in relation to sever e forms of periodontitis (SP), including juvenile, post-juvenile, and rapidly progressing periodontitis. Twenty-four (24) teeth from 16 pati ents with SP were examined by transmission electron microscopy (TEM). The AB was not discrete, with islands of bacteria in the so-called pla que-free zone (PFZ). Coronal to the AB the established plaque consiste d of a layer of Gram-positive cocci and ghost cells and a superficial layer mainly of Gram-negative morphotypes, including cocci, rods, fila ments, fusiforms, and spirochetes. The most apical apparently intact o rganisms in the PFZ were in bacterial islands or in isolation and were predominantly Gram-negative cocci and rods, with ghost cells in abund ance. Ruthenium red, alcian blue-lanthanum nitrate, and safranin O wer e used to label matrix polyanionic macromolecules, and periodic acid ( thiosemicarbazide) silver proteinate for intracellular polysaccharide (IFS). The matrix components were mainly fibrillar. Many intact bacter ia exhibited extracellular polysaccharides of glycocalyces associated with their cell wall, and cytoplasmic IFS granules. The latter varied in distribution and were evident even in the most apically advanced in tact microorganisms. The results indicate that IFS and some matrix fea tures of the apical border plaque in severe periodontitis in certain a spects resemble those of sub-contact area plaque on children's teeth, in health or associated with early chronic gingivitis, and with those in chronic adult periodontitis. They also suggest the establishment of acidic regions in the microniche at the bottom of the periodontal poc ket in the various forms of periodontitis differing in rate of progres sion. It was concluded that there was a limited range of intact bacter ial morphotypes in the apical border plaque in severe periodontitis, s imilar to those in chronic adult periodontitis.