Dental Plaque and Biofilm Characteristics

Microbiology of Periodontal Diseases

• The microbiology of periodontal diseases is complex, affecting the host, oral environment, and treatment.
• Understanding the formation, composition, and characteristics of dental plaque is crucial for its control.
• Different tooth deposits include dental plaque, materia alba, and calculus.

Learning Objectives

• Understand different tooth deposits, their formation, and disease implications.
• Recognize the different bacterial complexes and families involved in periodontal disease.
• Comprehend bacterial interactions during various periodontal diseases.
• Correlate periodontal treatment modalities to microbial reasons.

Bacterial Types

• Gram-negative bacteria such as Veillonella and Prevotella are present early.
• Gram-positive bacteria, such as Streptococcus and Actinomyces, are common initial colonizers of the pellicle.
• Haemophilus, Neisseria, Capnocytophaga, and Fusobacterium are present.
• Other species, such as Porphyromonas gingivalis can be part of the late colonizers.

Plaque Formation

• Plaque forms on hard tissues within 1-2 days without oral hygiene.
• It can form in cracks, pits, fissures, under overhangs, and around malaligned teeth.
• Plaque is comprised of bacteria, organic materials (glycoproteins, polysaccharides, albumin, lipids), and inorganic materials (calcium, phosphorus, sodium, potassium, fluoride).
• Plaque starts with the formation of a pellicle, followed by initial colonization, secondary colonization, and finally plaque maturation.
• The process starts with bacteria interacting with the surface, and then through physical/physiological interactions.

Dental Plaque = Dental Biofilm

• Dental plaque is a complex biofilm with a well-organized community of bacteria.
• More than 99% of bacteria live as attached bacteria.

Biofilm Significance

• Biofilms make bacteria resistant to antimicrobial agents. Mechanisms include, limited diffusion into the matrix, slow growth rate, and altered properties as a result of growth on a surface.

Six Major Ecosystems

• Intraoral and supragingival hard surfaces of teeth, implants, restorations, and prostheses
• Subgingival regions adjacent to teeth and implants.
• Epithelium of the buccal/palatal surface and floor of the mouth.
• Dorsum of the tongue.
• Tonsils.
• Saliva.

Human Oral Microbiota

• Includes commensal, symbiotic, and pathogenic species, and their resulting biofilms.

Different Plaque Regions and Associated Diseases

• Supragingival plaque leads to calculus and caries.
• Marginal plaque leads to gingivitis
• Subgingival plaque leads to calculus, and soft tissue destruction.
• Tooth-associated plaque can be problematic depending on exact location
• Tissue-associated plaque, can cause problems if not addressed properly

Microbiological Specificity of Periodontal Diseases

• Nonspecific Plaque Hypothesis
• Specific Plaque Hypothesis
• Ecological Plaque Hypothesis

Examples of Interactions between Periodontal Pathogens

• Cooperation exists through coaggregation.
• Competition occurs when multiple species compete for binding sites.
• Different microbial complexes such as yellow-purple, green, orange, and red.

Plaque Index

• A way to quantify dental plaque as a simplified method for clinical assessment.

Microorganisms Associated with Specific Periodontal Diseases

• Periodontal health - many gram-positive species.
• Gingivitis - almost equal proportions of gram-positive and gram-negative flora.
• Pregnancy-associated gingivitis - Prevotella intermedia, which uses steroids as growth factors.
• Chronic periodontitis - elevated percentages of anaerobic gram-negative species.
• Aggressive periodontitis - heightened counts of Aggregatibacter actinomycetemcomitans.
• Abscesses of the periodontium - Fusobacterium nucleatum, P. intermedia, P. gingivalis and B. forsythus.

Conclusion

• Mechanical removal is the most effective treatment to control dental plaque biofilms.