Apical Plaque Border Research Articles

The apical border plaque in severe periodontitis. An ultrastructural study.

This study concerns the apical border (AB) plaque in relation to severe forms of periodontitis (SP), including juvenile, post-juvenile, and rapidly progressing periodontitis. Twenty-four (24) teeth from 16 patients with SP were examined by transmission electron microscopy (TEM). The AB was not discrete, with islands of bacteria in the so-called plaque-free zone (PFZ). Coronal to the AB the established plaque consisted of a layer of Gram-positive cocci and ghost cells and a superficial layer mainly of Gram-negative morphotypes, including cocci, rods, filaments, fusiforms, and spirochetes. The most apical apparently intact organisms in the PFZ were in bacterial islands or in isolation and were predominantly Gram-negative cocci and rods, with ghost cells in abundance. Ruthenium red, alcian blue-lanthanum nitrate, and safranin O were used to label matrix polyanionic macromolecules, and periodic acid (thiosemicarbazide) silver proteinate for intracellular polysaccharide (IPS). The matrix components were mainly fibrillar. Many intact bacteria exhibited extracellular polysaccharides or glycocalyces associated with their cell wall, and cytoplasmic IPS granules. The latter varied in distribution and were evident even in the most apically advanced intact microorganisms. The results indicate that IPS and some matrix features of the apical border plaque in severe periodontitis in certain aspects 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 pocket in the various forms of periodontitis differing in rate of progression. It was concluded that there was a limited range of intact bacterial morphotypes in the apical border plaque in severe periodontitis, similar to those in chronic adult periodontitis.

The "plaque-free zone" in health and disease: a scanning electron microscope study.

A "plaque-free" zone has been described on the enamel surface of healthy extracted teeth. This study examined this zone on chronic adult periodontitis-affected teeth (CAPT). Ten healthy controls and 16 CAPT were collected immediately after extraction, fixed, dehydrated, critical point dried, coated, and viewed by scanning electron microscopy (SEM). The "plaque-free" zone was observed in both groups as an area with few bacteria between the apical plaque border and the coronal limit of an epithelial layer on the root surface, extending to the residual periodontal ligament. On the healthy specimens, the apical plaque border consisted mainly of cocci and short rods, while on the CAPT specimens spirochetes predominated. Isolated or small groups of microorganisms were always present in the "plaque-free" zone and at its apical limit, close to or in contact with junctional epithelial cells. This zone is therefore not completely free of plaque, as suggested. It was concluded that a tissue complex, analogous to that in health on enamel, persists on the root surfaces of CAPT throughout the disease process. It comprises a discrete plaque border, a dental cuticle with sparse organisms, and an epithelium analogous to junctional epithelium. Its main function would appear to be to prevent bulk access of plaque to the surrounding tissues, including direct contact of bacteria with underlying ligament.

The apical border plaque in chronic adult periodontitis. An ultrastructural study. I. Morphology, structure, and cell content.

THIS STUDY CONCERNS THE APICAL BORDER (AB) plaque in relation to chronic adult periodontitis (AP). Fifty-six teeth from 24 patients with AP were examined by transmission electron microscopy (TEM). The AB was not discrete with islands of bacteria in the so-called plaque-free zone (PFZ). Coronal to the AB, the established plaque commonly consisted of three to four layers of Gram-positive and Gram-negative cocci, rods, filaments, and spirochetes and a superficial layer, mainly of spirochetes, but including filaments, "test tube brush," and "corn-cob" formations. The most apical apparently intact organisms in the PFZ were in bacterial islands or in isolation and were predominantly Gram-negative cocci and rods, with occasional other morphotypes. The most apical microorganisms were invariably ghost cells. A cuticle of varying thickness and structure was present at the plaque/tooth interface. It was concluded that there was a limited range of intact bacterial morphotypes in the apical border plaque in chronic periodontitis.

The apical border plaque in chronic adult periodontitis. An ultrastructural study. II. Adhesion, matrix, and carbohydrate metabolism.

THE AIM OF THIS STUDY was to characterize the plaque matrix and relevant aspects of metabolism of the apical border plaque in relation to teeth affected by chronic adult periodontitis. The material comprised 56 teeth from 24 patients. Ruthenium red, alcian blue, lanthanum nitrate, and safranin 0 were used to label matrix polyanionic macromolecules and periodic acid-thiosemicarbazide-silver proteinate for intracellular polysaccharide (IPS). The matrix components were amorphous, fibrillar, or globular. Many intact bacteria exhibited extracellular polysaccharides or glycocalyces associated with their cell wall and cytoplasmic IPS granules. The latter varied in size and distribution and were evident even in the most apically-advanced intact microorganisms. The results indicate that the matrix and IPS features of the apical border plaque in chronic periodontitis in certain respects resemble those of subcontact area plaque on children's teeth, associated with chronic gingivitis and approximal caries. They also suggest the establishment of acidic regions in the microniches of the periodontal pocket.

Associations between subgingival plaque bacterial morphotypes and clinical indices?

The aim of the present study was to evaluate possible associations between subgingival plaque bacterial morphotypes, as assessed by darkground microscopy, and clinical indices of routine adult chronic periodontitis. Clinical indices were plaque index (PlI), gingival index (GI), sulcus bleeding index (SBI), papilla bleeding index (PBI), attachment loss (AL), pocket depth (PD) and probeable pocket depth (PPD). Apical border plaque was sampled in vivo and after extraction to test whether direct or indirect sampling affected any such associations. Similarly, pocket depth and attachment loss were also assessed directly and indirectly on the same teeth, in vivo or after extraction. The influence of the type of index used to record inflammation (GI, SBI, PBI) was also assessed, as were the effects of the numbers of sampled subjects and the method of analysis, which comprised the use of transformed and untransformed data and of parametric and non-parametric tests. Data were collected in relation to the approximal surfaces of 44 teeth extracted from 22 adults (2 teeth each) and from 1 pair of contralateral upper anterior or premolar teeth in each of 100 adults, all which untreated routine chronic periodontitis. Selected subjects had greater than or equal to 4 mm probeable pocket depth and/or attachment loss, and radiographic evidence of bone loss in relation to 1 approximal surface on each of 1 pair of contralateral anterior or premolar teeth, or to 2 teeth scheduled for extraction. Plaque preparation and darkground microscopy were as described previously. Insignificant associations (p greater than 0.05) were demonstrated between supragingival plaque (PlI) and periodontal inflammation (GI, SBI, PBI) or destruction (PPD and AL), as well as between inflammation and attachment level. In contrast, significant moderate associations (r = 0.5-0.77) were demonstrated between each of the 3 morphotype groups; spirochaetes, other motiles and cocci. Spirochaetes showed a significant moderate (r = 0.5) positive association with pocket depth with a 2.43% mean increase of spirochaetes for each 1 mm increase of PPD. Although highly significant associations (r = 0.9) were demonstrable between the 3 inflammation indices (GI, SBI, PBI) themselves, only PBI showed significant positive associations (r = 0.3) with spirochaetes and other motiles. Also, PlI showed significant associations with each of the 4 morphotypes (r = 0.3-0.5). The heterogeneity of spirochaetes and other motiles as well as the multiplicity of possible aetiological microbial agents in plaque may have resulted in underestimated associations between subjects as well as undetectable association within a given mouth using only 4 morphotype groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification ofPorphyromonas gingivalisandActinobacillus actinomycetemcomitansin Apical Border Plaque

This study concerns the identification of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans in subgingival plaque close to the bottom of the pocket using the combination of ultrastructural criteria and postembedding immunogold labelling. Specimens of plaque from deep periodontal pockets were fixed in 0.5 per cent glutaraldehyde in 0.1 M sodium cacodylate buffer, dehydrated, and embedded in LR White acrylic resin. Pure cultures of P. gingivalis and A. actinomycetemcomitans were processed in the same way. Ultrastructural differences in the structure of the cell wall envelope and cytoplasm were noted between the two organisms. Similar differences were observed in certain Gram-negative organisms within the apical border plaque samples. Following immunogold labelling, cells with the same ultrastructural features as P. gingivalis or A. actinomycetemcomitans showed positive labelling. None of the other organisms in the plaque was labelled. We therefore suggest that the combination of morphological criteria and a specific marking system such as colloidal gold provides a method by which organisms in apical border plaque can be identified in situ , although differentiation between strains may as yet be more difficult. Keywords: Porphyromonas gingivalis ; Actinobacillus actinomycetemcomitans ; Periodontitis; Plaque; Ultrastructure; Immunogold.

Middle zone of the root surface integument of human teeth affected by chronic periodontitis.

This study has confirmed the presence on the root surface of teeth affected by chronic periodontitis of a zoned organic integument analogous to that on enamel. Measurements showed a highly significant correlation between the levels of the bounding structures of this zone, that is, the apical plaque border and the coronal border of residual periodontal ligament, for both shallow and deep pockets. The middle zone between these two was on average 1 mm wide.

Access to subgingival plaque by disclosing agents using mouthrinsing and direct irrigation.

Teeth destined for extraction and exhibiting periodontal pockets had reference grooves cut on the proximal surfaces at the level of the gingival margin. A disclosing agent was then applied either as a mouthrinse or by direct irrigation at the entrance of the pocket. After extraction, the extent of apical penetration of the solution was measured from the reference point. Subsequently, the tooth was stained enabling similar measurements from the reference point to the level of the apical plaque border and the coronal level of the residual periodontal ligament. Analysis of these measurements indicated that neither mouthrinsing nor direct irrigation routinely achieved penetration of the solution to the apical plaque border. While mouthrinsing failed to achieve any significant penetration of pockets, the direct irrigation technique was partially effective. It was concluded that direct irrigation offers promise as a mode of application of chemical agents to subgingival plaque.

The host-organism interface in natural human dental plaque

This study concerns the adhesion of natural apical border plaque to approximal surfaces of children's posterior teeth. The predominant intact cells were poly saccharidecontaining cocci linked to the cuticle by means of mainly fibrillar or globular polysaccharide. Correlation of the features observed with those from studies of plaque formation and microbial adhesion in other habitats suggests that approximation of bacteria to enamel cuticle (and salivary pellicle) may be due to cross-linking and salt bridging of polysaccharide until mutually repulsive net negative surface charges are overcome. Low radius of curvature of bacterial processes and low pH, the latter to be expected at the subcontact area apical border in children, would favour reduction in bacterial surface potential. The final stages in bacterial adhesion in plaque seem to involve strong forces producing flattening of the cell wall at the site of the closest contact.

Immunoglobulins in human dental plaque

Immunoglobulins have been found previously in human gingiva, gingival fluid, serum and smeas of dental plaque. In the present study their presence and distribution in situ have been studied by immunofluorescence on the approximal surfaces of childen's teeth extracted due to caries or for orthodontic reasons. There wee also preliminary investigations of S. mutans distribution and of plaque immunoglobulins in grossly carious adult teeth. Positive fluorescence was in the order total Ig > IgG > IgA > IgM. S mutans (serotype c) was found in two of seven samples. Fluorescence was most marked at the apical plaque border, especially in relation to the contact area. This may relate to the prevalence of lysed organisms in this region. The topography and distribution of the different immunoglobulins correlate with previous studies suggesting gingival fluid (via plasma and gingival plasma cells) as the main source of the plaque immunoglobulin at the site of onset of approximal caries and chronic inflammatory periodontal disease.