The apical border plaque in severe periodontitis. An ultrastructural study

Area of Science:

• Microbiology
• Periodontology
• Oral Pathology

Background:

• Severe periodontitis (SP) encompasses aggressive forms like juvenile, post-juvenile, and rapidly progressing periodontitis.
• The apical border (AB) plaque's composition and role in SP are not fully elucidated.
• Understanding plaque characteristics is crucial for diagnosing and managing periodontitis progression.

Purpose of the Study:

• To investigate the ultrastructure and composition of the apical border (AB) plaque in severe periodontitis (SP).
• To identify bacterial morphotypes and matrix components, including intracellular polysaccharides (IPS), within the AB plaque.
• To compare the findings with plaque characteristics in other periodontal conditions.

Main Methods:

• Transmission electron microscopy (TEM) was used to examine 24 teeth from 16 SP patients.
• Specialized stains (Ruthenium red, alcian blue-lanthanum nitrate, safranin O, periodic acid-thiosemicarbazide silver proteinate) were employed to visualize matrix macromolecules and IPS.
• Analysis focused on the plaque-free zone (PFZ) and the established plaque coronal to the AB.

Main Results:

• The AB plaque was not discrete, featuring bacterial islands within the PFZ.
• The established plaque had distinct layers: Gram-positive cocci/ghost cells coronally and Gram-negative morphotypes apically.
• Intact bacteria, even at the apical extent, contained cytoplasmic IPS granules, and matrix components were fibrillar.

Conclusions:

• IPS and matrix features in SP apical border plaque share similarities with plaque in children's teeth and adult periodontitis.
• Acidic microenvironments may develop at the base of periodontal pockets in various forms of periodontitis.
• Severe periodontitis apical border plaque exhibits a limited range of intact bacterial morphotypes, akin to chronic adult periodontitis.