Dental Adhesion and Bacterial Attachment

Adhesion in Oral Bacteria

• Adhesion: The attachment of microorganisms to a host
• Adherence: The ability of microorganisms to adhere to a host

Adhesive Surfaces in the Mouth

• Keratinized epithelial cells
• Non-keratinized epithelial cells
• Hydroxyl apatite surfaces (tooth hard tissues and ceramic restorations)
• Metal and acrylic surfaces of prosthesis

Bacterial Attachment Organelles

• Fimbria (Pili)
  • Tip 1: Inactivated when there is mannose in the environment
  • Tip 2: Not inactivated with mannose found in the environment
• Capsule
• Flagella

Fimbria

• Proteus, Escherichia, and Neisseria gonorrhoeae attach to urinary system multi-layer epithelial cells with fimbria
• Enteric rods attach to intestinal villi and colon mucosa
• A group beta hemolytic streptococci and Corynebacterium attach to tonsillar mucosa with host receptors
• Fimbria can bind to receptors and/or attach to surfaces without receptors

Capsule

• S.pneumoniae, K.pneumoniae, H.influenzae, N.meningitidis, L.pneumophila: encapsulated bacteria
• Attach to single layer cilial epithelial cells in the respiratory tract system
• Capsule-mediated adhesion does not need specific receptors
• pH, temperature, ion balance is essential for adhesion

Flagella

• Enhance invasion and spread within tissues
• Flagellum protein also enhances adhesion to host tissue
• Ex: Motile Spirochetes

Adherence

• Bacterial adherence is selective
• Ex: Streptococcus salivarius cannot attach to tooth hard tissues, while Streptococcus mutans can attach to tooth hard tissues
• Veillonella parvum is isolated mainly from tongue papillas
• Leptothrischia is isolated from cheek mucosas

Important Factors

• No bacteria are found by chance in any flora
• Bacterial adhesion determines not only bacterial virulence but also which tissue will be infected
• Ex: Brucella, Salmonella, P.aeruginosa, Proteus, and other enteric cannot attach to mouth tissues

Porphyromonas gingivalis

• Attaches to keratin binding receptor of gingival epithelium in a short time
• This makes bacteria an important oral pathogen

Other Factors Affecting Adhesion

• Desquamation of oral mucosa: hundreds of cells lost every day from the surface layers of the epithelium
• Bacterial loss with these cells
• Bacteria float within saliva (10^8 CFUs)
• Generally, the number of bacteria bind to each gingival epithelial cell (10-15), and the number of bacteria on the tongue surface is 100

Oral Pathogens and Adhesion

• Specific attachment: Attachment of oral pathogens to oral tissues using specific receptors
• Non-specific attachment: Attachment of oral pathogens to oral tissues without specific receptors
• Direct and indirect attachment types
• Ex: Attachment of Leptotrichia buccalis to cheek mucosa and attachment of M protein of A group Streptocci to pharynx and tonsils mucosas