Periodontium Flashcards
periodontium is defined as
those tissues supporting and investing the tooth which are PDL, cementum, bone lining and the gingiva facing the tooth.
periodontium has what origin
ectomesenchymal except gingiva
define cementum
cementum is a vascular hard tissue that surrounds the root of the tooth. it either has cell or no cell and is has collagen fibers in its matrix
stages of development of cementum
it has 2 stages
prefunctional stage that occurs throughout root formation
and functional stage that occurs after the tooth is in occlusion and continues throughout life
function of acellular and cellular cementum
acellular has the role of anchorage and cellular has the adaptative response to tooth wear and movement and repair of periodontal tissues.
composition of cementum
45-50% hydroxy and 50% organic collagen and non collagenous proteins
predominant collagen if cementum and its function
is type I collagen and is found in pdl and it structures the fiber bundles that attach the tooth to the bone and distribute masticatory force
type III in cementum is found when
during repair, development and regeneration of mineralization and is reduced as the the cementum matures
another type of collagen except I and III and its found where and does what?
its XII type collagen and its found is association with type I . its present in ligamentous tissues including pdl and it maintains a mature and functional pdl to withstand the occlusion of the force of occlusion
trace amount of other collagen found are
V VI AND XIV
non collagenous proteins found in cementum are
alkaline phosphate, bone sialoprotein, dentine sialoprotein, dentine matrix protein 1, osteonectin, ostepontin, tenascin, oesteocalcin, proteoglycans, fibronectin and BRIL
cementum formation initiation is limited to
root edge
describe what happens before cementum on roof surface is made
HERS at the coronoapical extension of inner and outer enamel epithelium send induction message to produce some enamel or other epithelium proteins to the facing ectomesenchymal pulp cells, that form odontoblast and make the predentin.
current theories
- after dentine has been deposited, the hers become interrupted and ectomesenchymal cells from the inner portion of dentinal follicle comes in contact with the predentin
- dental follicle receive reciprocal inductive signals from dentine or hers surrounding the cells and differentiate into cementoblast.
- the hers trasnform into cementoblast
cell rest of malassez
the fragments of sheath make up a mass of cells in pdl know as the cell rest of malassez which function as maintained and regeneration of periodontal tissues
enamel pearls and made where (ALSO CALLED AS RADICULAR CYST)
if HERS remain attached to the forming root, they form focal deposition of enamel like material on the furcation of the root,
Precursors cells of cementum and pdl are what and what origin
the origin is dental follicle and the cells are cementoblast and fibroblast
what leads to the formation of cementodentinal junction
cementoblast producing acellular extrinsic fiber differentiate at the proximity of the root edge
in the developing root, cementoblast align against the un mineralized mantle dentine
they extend their processes inside the mantle dentin and starts depositing collagen fibers so the cementum and dentine intermingle.
mineralization then spreads from mantle dentine to the cementum under the influence on non collagenous matrix proteins and that’s how CEJ is made
initial acellular extrinsic fiber cementum has
a layer on mineralization with collagen fiber fringe implanted perpendicular to the root surface
how acellular extrinsic fiber cementum thickens
the cells on the surface move away depositing more collagen so that the fine fiber bundle thickens, it also secrete non collagenous matrix protein that are present between the collagen.
the activity of surface cells moving away and depositing collagen goes on for how long and what happens after that
this activity goes on till 15 to 20 micrometer of cementum has been formed and then pdl comes and gets stitched with the fibrous fringe
stirations seen on acellular extrinsic fiber cementum
one stiaration is parralel to the rooth
initial acellular extrinsic fiber cementum has
a layer on mineralization with collagen fiber fringe implanted perpendicular to the root surface
how acellular extrinsic fiber cementum thickens
the cells on the surface move away depositing more collagen so that the fine fiber bundle thickens, it also secrete non collagenous matrix protein that are present between the collagen.
the activity of surface cells moving away and depositing collagen goes on for how long and what happens after that
this activity goes on till 15 to 20 micrometer of cementum has been formed and then pdl comes and gets stitched with the fibrous fringe
stirations seen on acellular extrinsic fiber cementum
one striation is parallels to the root and is the incremental deposition and the other striation is perpendicular to the root surface and those are mineralized PDL collagen fiber bundles