Lecture 4 Flashcards
Dental biofilm is a major etiology factor in the development of
Dental caries
Initiation and progression of periodontal disease
Materal alba
• Loosely adherent
• Cellular debris: Epithelial cells, White blood cells (PMNS), Red blood cells
• Mass of bacteria, viruses and yeasts
• Non-specific location
Biofilm definition
Polymicrobial ( mostly bacteria (several hundred species of bacteria) and other organism) ecosystem
• Well-organized complex community of bacteria
• Not evenly distributed
Where does biofilm develop? How is that relevant to us?
On any wet surface
Develops on:
• Dentition: Adheres tenaciously to tooth surfaces restorations and prosthetic appliances
• Soft tissue surfaces
• Thrive in dental water and suction lines: Primary source of delivery of contaminated water
The bacterial micro colonies in biofilm cluster to form
mushroom shaped micro colonies attached to tooth surface at a narrow base
The bacteria in biofilm are embedded in ______.
Extracellular slime layer
What is the extracellular slime layer made out of?
Glucose polymer glucan - produced by bacteria
Function of extracellular slime layer
- Sticky protective barrier surrounding micro colonies. Protection from physical or chemical destruction
A. Protection from other bacteria
B. Prevents deep penetration of antimicrobial drugs and antiseptic rinses. Thickened by drug-resistant antimicrobial bacteria
C. Protects bacteria against leukocytes. In fact, the substances released by leukocytes (inflammatory response) to bacteria damage surrounding tissue more than bacteria
- Adherence and Aggregation
- Maintains integrity of biofilm
Fluid channel
Series of fluid channels penetrate slime layer to provide nutrients and oxygen to bacteria, as well as allow movement of bacterial metabolites, waste products, and enzymes
Microcolonies use _____to communicate with each other
Chemical signals (this is called the communication system)
Symbiosis Versus Dysbiosis
Symbiosis
• Harmony; mutually beneficial relationship between host and commensal (normal flora) bacteria
Dysbiosis
• Imbalance of relationship between microbial colonies and host
Biofilm provides bacteria with an advantage permitting long-term survival within
sulcus or pocket environment
Subgingival biofilm remarkably resistant to
• Antibiotics administered systemically
• Antimicrobials administered locally
• Body’s defense system
Since biofilm is so resistant to antimicrobial agents, they are best when used in conjunction with:
mechanical cleaning that removes or disrupts the dental plaque biofilm
The dose of antimicrobial agents need to kill free floating bacteria not in biofilm
HOWEVER……
• Dose needed to kill free floating bacteria
• Increased approx. 1500 times →
• Kill patient before the biofilm bacteria
Biofilms can be destroyed by
wiping them off → disrupting attachment. Most successful means for biofilm infection control is physical (mechanical)
removal
Brushing, flossing, and periodontal instrumentation (scaling, cavitron) (for subgingival biofilm)
Mechanical cleaning forces bacteria to start over with attachment
If areas cleaned regularly and biofilm is left for more than 24 hours, ___unable to develop
mature and complex biofilm
Essential component in treatment of periodontitis with regard to subgingival biofilm
Frequent periodontal instrumentation of subgingival root surfaces
Five phases of Dental biofilm formation
Divided into five phases
1. Initial Attachment of Bacteria to Pellicle
2. Initial colonization
3. Secondary colonization
4. Extracellular slime layer and microcolony formation
5. Formation of mature subgingival plaque biofilms
First phase of dental biofilm formation: Initial Attachment of Bacteria to Pellicle
Few hours after pellicle formation
• Bacteria attach to outer surface of pellicle
• Connect to pellicle and each other with hundreds of hairlike structures - Fimbriae
Pellicle
• Thin coating composed of salivary glycoproteins
• Protect from acidic activity
• Attaches to tooth surface within minutes of a cleaning
• Acts like double-sided adhesive tape
• Provides a sticky surface for attachment by bacteria
• Nutrient source for bacteria
Second phase of dental biofilm formation: Initial Colonization of the Tooth Surface:
New Bacteria Join In
• Bacteria stick tooth surface
• Within first 2 days (no further cleaning is undertaken) tooth’s supragingival surface is colonized predominantly by gram-positive bacteria
Third phase of dental biofilm formation: Secondary Colonization
• Produce substances which stimulate other free-floating bacteria to join community
Fourth phase of dental biofilm formation: Production of Extracellular Slime Layer and Microcolonies formation
Production of Extracellular Slime Layer
• Attachment to tooth stimulates bacteria to excrete slimy glue-like substance - glucan
• Anchors bacteria to tooth
• Provides protection for attached bacteria
Microcolony Formation
•Once tooth surface covered with attached bacteria, biofilm grows by cell division of adherent bacteria primarily and attachment of new bacteria
• Proliferating bacteria begin to grow away from tooth; called Bacterial blooms
• There are periods when specific species or groups of species grow at rapidly accelerated rates
Fifth phase of dental biofilm formation: Formation of Formation of mature subgingival plaque biofilms
• Bacteria cluster together to form mushroom-shaped microcolonies
• Attached at narrow base
• Formation of complex collections of different bacteria linked to one another
Types of organisms in biofilm vary
• Individuals
• Sites
Dental biofilms identified based on surface of tooth in relation to gingival margin
• Supragingival
• Subgingival
Presence of supragingival plaque biofilm influences subgingival plaque biofilm:
• Growth
• Accumulation
• Pathogenicity
How does bacteria get subgingivally?
Inflammation and edema alter anatomic relationship of gingival margin and tooth
• Allows Bacterial invasion
• Further bacterial multiplication
Subgingival Plaque Biofilm bacterial description and how they injury periodontal tissues
• Anaerobic
• Motile
• Gram negative
• Asaccharolytic: Uses proteins for nutrients
Cause direct injury to periodontium
• Toxins
• Enzymes
• Metabolic products
Indirect injury via inflammatory response
3 zones of subgingival plaque
Tooth attached
Epithelial attached
Unattached
Tooth attached plaque biofilm
• Densely packed
• Adherent to tooth from gingival margin to junctional epithelium
• Inner layers Gram+
• Gram - cocci and filaments
• Anaerobes and aerobes
• Less virulent
• Removed by scaling and root planing
Epithelial Attached Plaque Biofilm
• Loosely packed
• Adherent to epithelium (tissue) of pocket
• Gram -, motile and anaerobes
• Spirochetes
• Can invade CT and be found on surface of alveolar bone
• Most virulent and detrimental to periodontal tissues
• Surgically removed
Unattached Plaque
• Free floating in pocket
• Protected from mechanical forces
• Gram - rods and spirochetes, motile, anaerobes
• Removed by flushing
Bacteria Associated with Health
Range of bacteria that can be cultured from a individual’s healthy sulci
Gram positive and/or gram negative? What %?
Two specific bacteria names
Motile or non-motile?
Can pathogenic pathogens be in a healthy sulcus?
• 100 to 1,000 bacteria can be cultured from an individual healthy sulci
• 75 to 80% gram +
• Most of remaining bacteria are gram -
• Streptococci and Actinomyces
• Non motile
• Periodontal pathogens can inhabit healthy sulci in small proportions
General bacterial characteristics in health and disease
Health
• Gram Positive
• Aerobic
• Nonmotile
• Saccharolytic
Disease
• Gram Negative
• Anaerobic
• Motile
• Asaccharolytic
Bacteria Associated with Periodontitis
Range if cultured from an individual site
Gram negative or gram positive?
Aerobic or anaerobic?
Mobile or nonmobile?
As the disease progresses what happens the flora?
• 100,000 to 100,000,000 bacteria can be cultured from individual site
• Large number of gram -, anaerobes and motile bacteria
• Disease progresses → more complex flora
• REMEMBER: Bacterial composition of periodontitis differs significantly from patient to patient and from site to site
All periodontal infections are associated with or caused by
multiple bacteria
• Polymicrobial nature / mixed infections
Presence of beneficial organisms and how it affects periodontal pathogens
can modify effects of pathogens and reduce likelihood of disease progression
Fusobacterium nucleatum
Characteristics
What it is associated with
Prominent component of
Virulence factors
Porphyromonas gingivalis
Importance in periodontitis
Characteristics
What cell it invades
Tannerella forsythia virulence factors (4)
Porphyromonas gingivitis virulence factors (6)
Treponema denticola
Aggregatibacter actinomycetemcomitans
Aggregatibacter actinomycetemcomitans virulence factors (7)
Are periodontal disease contagious?
No, transmission doesn’t equal disease
How are periodontal pathogens spread or transmitted?
Vertical (different generations)
• Risk of contracting disease from family members
• Living in close contact
• Passed directly through saliva
• Requires long-term exposure
Horizontal (same generation)
• Kissing primary means
What is virulence?
Bacteria must have these characteristics to be virulent (3)
Definition: ability to cause disease
- Proximity to tissue
• Withstand mechanical forces of oral cavity and able to adhere
• Cell surface characteristics for survival - Ability to evade host defenses
- Ability to destroy tissue
Bacterial Invasion
• Penetrate epithelium lining and invade CT
• Both Gram + and - bacteria been ID in CT and near alveolar bone
• A.a., P. gingivalis, T denticola, T forsythia directly invade host tissue cells
• Presence of bacteria within the tissues makes periodontitis more resistant to treatment
Tissue Destruction:
Mechanisms of Bacterial Action
Direct
• Endotoxic
• Exotoxic
• Enzymes
Indirect
• Immunopathologic
Bacterial Endotoxic
• Lipopolisaccharide - LPS
• Released from cell walls of gram - bacteria
• Cytotoxic - agent kills living cells
• Initiate inflammation
• Cause soft tissue destruction
• Stimulate bone resorption
Bacterial Exotoxins
• Harmful proteins released from bacterial cell
• Act on host cells at a distance
• A.a. produces leukotoxin that enable bacteria to destroy leukocytes in the sulcus or pocket
Bacterial Enzymes
What does it assist bacteria to do?
How does it affect the epithelial lining?
Which periodontal pathogens commonly seen periodontitis have enzymes?
Bacterial enzymes contribute contribute to the breakdown of what in connective tissue?
Bacterial enzymes promote migration of what ?
Bacterial enzymes diminish the ability of what to defend the host?
• Assist bacteria in invading tissue
• Increase permeability of the epithelial lining
• Easier penetration of sulcular epithelium
• A. a., P. gingivalis
• Contribute to the breakdown of collagen fibers and ground substance in CT
• Promote apical migration of the JE along the root surface
• Diminish the ability of immunoglobulins and other body proteins to defend the host
Enzymes which Breakdown
Periodontal Tissues
What are Host Derived Enzymes?
Host Derived Enzymes
• matrix metalloproteinases
• Degrade collagen and proteoglycans
• Cause osteoclastic bone resorption
Indirect Effect
Immunopathologic Mechanism
• Dual host immune response
• Protective
• Contributes to periodontal breakdown
• Bacterial antigens stimulate the immune response
• Cell mediated and Humoral
