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26 Cards in this Set
- Front
- Back
The area of gingival cuff is critical in doing what
There are a number of what in this region What do they do |
The area of the gingival cuff is critical in maintaining
the correct relationship between the gingiva and the tooth, thereby protecting the deeper tissues of the periodontal ligament and alveolar bone. There are a number of cell types in this region which, in normal healthy conditions, act together in a coordinated fashion to maintain the status quo in terms of connective tissue and alveolar bone integrity. |
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Cells usually involved in the bone loss process
Explain their appearance and presence |
The major cells involved in this ‘homeostatic’ process
are: the osteoclast – the bone resorbing cell which is characteristically very large and multinucleated and has a brush border adjacent to the bone surface where active resorption is taking place. The osteoclasts are usually situated in resorption pits called Howship’s lacunae. |
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What is the osteoblast
What are the periodontal and and gingival fibroblasts |
The osteoblast – the bone
forming cell which is characteristically found as a single cell layer lining the bone surface. It is an active protein producing cell. The periodontal and gingival fibroblast – the cell responsible for forming and maintaining the collagenous matrix of the ligament and lamina propria |
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What is the osteoblast
What are the periodontal and and gingival fibroblasts |
The osteoblast – the bone
forming cell which is characteristically found as a single cell layer lining the bone surface. It is an active protein producing cell. The periodontal and gingival fibroblast – the cell responsible for forming and maintaining the collagenous matrix of the ligament and lamina propria |
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Why is the cell very active
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It is a very active cell as the turnover time for the matrix in periodontal tissues is rapid.
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What is a macrophage
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The macrophage – a cell of the monocyte
lineage which an active member of the tissue’s defensive armoury. |
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The connective tissue of the periodontium is very cellular so what does this mean
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The connectivetissue of the periodontium is very cellular so there arelots of these cells which are turning over the matrix very rapidly with high rates of collagen production
and degradation, the latter by a process of phagocytosis of individual fibril fragments. |
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What 2 processes work together and why
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lots of these cells which are turning over the matrix
very rapidly with high rates of collagen production and degradation, the latter by a process of phagocytosis of individual fibril fragments. These two processes are basically in synchrony so that the overall level of matrix is constant |
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The tissue is also highly ....
From which..... |
This tissue is also highly vascularised from which circulating monocytes are recruited
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Under the control of a particular growth factor ( name it ) what happens
Where does this growth factor originate What does it do |
Under the control of a growth factor
called RANKL, originating from adjacent osteoblasts, they fuse and form osteoclasts. RANKL may be free within the matrix or bound to the osteoblast cell membrane and it binds to a specific receptor on th emonocyte membrane |
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By modulating the production of RANKL what happens
Once the osteolcalst is fully differentiated what does it do |
By modulating the production
of RANKL the osteoblast controls the rate of osteoclast formation. Once the osteoclast is fully differentiated it degrades bone by first pumping protons into the adjacent bone to dissolve mineral and then potent enzymes, mainly Cathepsin K, to breakdown the bone matrix. |
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Bone however does what
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Bone, however, is a dynamic tissue that responds to changes in loading such that the ratio of bone formation to removal in any one area will vary depending on the applied stress on the bone but is always in an ordered fashion so that one does not permanently predominate over the other
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The control of this bone balance is mediated largely through what? Via what
What is the modulation in RANKL production influenced by (2) |
The control of this balance is mediated largely through the osteoblast via the its production of growth factors such as RANKL.
The modulation in RANKL production is inturn influenced by the applied loading on the bone,either directly by the osteocytes and osteoblasts detecting the mechanical stresses within the bone itself or indirectly via macrophages which respond to loading by the production of cytokines such as interleukin-1 (IL-1). The production of RANKL by osteoblasts is increased by the action of IL-1. |
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Maintenance of alveolar bone dependent upon? Explain
How else can this balance between formation and degradation be disrupted |
The maintenance of the alveolar bone is very much
dependant on sufficient load derived from the presence of functioning teeth. If teeth are lost or extracted (as in this case) then the alveolar bone will be resorbed as the balance is upset and bone degradation outstrips formation. However, this balance between formation and destruction can also be tipped in the direction of bone resorption by the intervention of certain exogenous plaque bacterial derivedmaterial e.g lipo-polysaccharide (LPS) and bacterial enzymes which directly or indirectly affect the cells and matrix in the gingival cuff region. The next slide shows the dramatic effects of periodontal disease on alveolar bone. |
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What do sheep suffer from
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Sheep suffer from a rapidly progressing form of periodontal disease, known colloquially as ‘broken mouth’.
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If we go back to our original ‘status quo’ situation but
now add in a bacterial plaque adjacent to the epithelium what will happen |
If we go back to our original ‘status quo’ situation but
now add in a bacterial plaque adjacent to the epithelium, LPS derived from this plaque will pass through the epithelium and interact with the cell populations in the connective tissue and on the bone surface. |
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There is some evidence that lps can do what
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There is some evidence that LPS can act
directly on osteoblasts to upregulate RANKL production and on monocytes to accelerate their fusion to osteoclasts but the main effect is on macrophages. In these cells it stimulates an increase in, amongst other things, IL-1 production |
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What are the targets for increased il1
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One of the targets for the increased IL-1 are osteoblasts where RANKL production is upregulated which in turn leads to further recruitment of monocytes and the formation of more osteoclasts. Another target for IL-1 are the numerous fibroblasts throughout the tissue.
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These cells are triggered to produce what...
What acts upon what |
Thesecells are triggered to produce their own IL-1, some of which again acts upon the osteoblast population and
some acts in a paracrine fashion to stimulate yet more IL-1 from neighbouring cells. The IL-1 also stimulates the fibroblasts to produce extracellular collagenases – something they would not normally do. |
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This in part leads to...
First it does what |
This in part leads to a net loss of matrix and is
aided further by the presence of bacterial-derived collagenases. The IL-1 has two further effects. First it also stimulates the fibroblasts to produce another cytokine, interleukin 6 (IL-6). This cytokine increases the effectiveness of RANKL in stimulating osteoclast formation |
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Secondly what can IL-1 do
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Secondly, IL-1 can directly act on the
osteoclast to upregulate cathepsin K production and thereby increase the effectiveness of individual cells in degrading the bone matrix |
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What will happen finally
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Finally, of course, the extensive matrix degradation will in turn lead to major changes in loading on the bone and macrophages thereby adding another impetus to the bone loss process.
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What does the diagram provide
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provides a simplified picture of tissue
interactions in this region as many other cytokines and growth factors may be involved. Nevertheless it does give an indication of the complex interplay between the cells and how there is an inevitable rise in the rate of bone degradation, triggered by the presence of plaque bacteria. |
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Summarise the actions of lps
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LPS:
Acts on osteoblasts to upregulate RANKL production Acts on monocytes to increase osteoclast formation Acts on macrophages to upregulate IL-1 production |
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Summarise the actions of IL-1
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IL-1:
Acts on osteoblasts to upregulate RANKL production Acts on fibroblasts to upregulate IL-1 production Acts on fibroblasts to upregulate IL-6 production (which in turn potentiates RANKL) Acts on fibroblasts to induce collagenase production Acts on osteoclasts to upregulate cathepsin K production |
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The presence of bacteria (and their constituents and by-products) within
the gingival sulcus can trigger an inevitable, and ultimately catastrophic, alveolar bone loss in 3 interlinked ways: |
1. A direct stimulation of osteoclast formation
2. The production of an inflammatory response, including the production of numerous cytokines (notably IL-1), which directly or indirectly increases osteoclast formation and activity. There is also extensive connective tissue breakdown which in turn leads to: 3. A loss of loading on the bone which can of itself result in further bone loss. |