Ch. 14 Flashcards
virulence factor
- refers to all of the mechanisms that enable biofilm bacteria to colonize and damage the tissues of the periodontium
- may be either structural characteristics of bacteria themselves or substances that are produced by the bacteria
- these factors can enhance damage to the periodontium: 1. presence of LPS
2. ability to invade tissues
3. ability to produce enzymes
presence of lipopolysaccharide (LPS)
- gram negative bacteria are a component of mature biofilm
- LPS is an endotoxin that is present on the outer membrane of gram negative bacteria
- LPS can be responsible for initiating inflammation in periodontal tissues
the ability to invade tissues
- some perio bacteria like Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans can invade host tissues
- penetration of tissues can to some degree allow the bacteria to escape host defense mechanisms
the ability to produce enzymes
- several perio bacteria can produce enzymes such as collagenases and proteases that can directly degrade host proteins that are a basic part of the structure of the peridontium
biochemical mediators
- active compounds that host immune cells secrete
- are the “middlemen” sent by host cells to activate the inflammatory response
- ex: cytokines, prostaglandins, MMPs
cytokines
- powerful regulatory proteins that influence behavior of other cells
- transmits info or signals from one cell to another
- functions: increase vascular permeability, recruit cells such as PMNs and macrophages to the infection site, have potential to initiate tissue destruction and bone loss in chronic inflammatory diseases like perio, cytokines that play important role in perio include interleukin 1 (IL-1), 6, and 8, and tumor necrosis factor-a (TNF-a)
prostaglandins
group of powerful biochemical mediators derived from fatty acids. biologically important ones are D, E, F, G, H, and I. prostaglandins of the E-series (PGE) play important role in bone destruction seen in perio. Can increase permeability and dilation of the blood vessels, leading to redness and edema of the connective tissue.
Matrix metalloproteinases (MMPs)
family of at least 12 different enzymes produced by various cells of the body. These enzymes can act together to break down the connective tissue matrix. PMNs, macrophages, gingival fibroblasts, and junctional epithelial cells can produce MPPs. In the absence of disease, MMPs facilitate the normal turnover of the perio connective tissue matrix. In presence of chronic bacterial infection, large amounts of MMPs are released in what appears to be an attempt to kill invading bacteria. Extensive collagen destruction occurs in presence of increased MMPs.
factors affecting the host immune response
genetic factors, environmental factors (tobacco), acquired factors (DM, stress)
initial lesion (bacterial accumulation)
- develops 2-4 days following biofilm acculumation
- characterized by bacterial colonization near gingival margin, increased vascular dilation, and PMN migration to gingival sulcus. although host immune and inflammatory responses are activate, the gingival tissue looks clinically healthy in this phase.
- if bacterial pathogens are not controlled, early gingivitis develops
early lesion (early gingivitis)
- develops 4-7 days following plaque biofilm accumulation-
- observed clinically as redness and swelling of marginal gingiva
- characterized by subgingival plaque biofilm formation and intensified immune and inflammatory response
established lesion (established gingivitis)
- generally observed 21 days following plaque biofilm accumulation
- subgingival plaque biofilm extend to je
- increased cellular infiltrate and collagen breakdown in connective tissue is observed
- all clinical characteristics are evident in this phase
advanced lesion (periodontitis)
-characterized by periodontal pocket formation, bop, alveolar bone loss, furcation involvement, and tooth mobility
mechanism for alveolar bone destruction
- macrophages produce high concentrations of cytokines
- the biochemical mediators produced by macrophages stimulate the resident fibroblasts to secrete both PGE2 and MMP. gingival fibroblasts shift to a state that favors the destruction of the gingival connective tissue and pdl fibers.
- biochemical mediators produced by the macrophages and fibroblasts result in destruction of:
- extracellular matrix of the gingival connective tissue
- gingival fibers at the apical edge of the je
- the pdl fibers - PGE2 mediates bone destruction by stimulating large numbers of osteoclasts to resorb the crest of the alveolar bone
