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
overall degree of mineralization of acellular extrinsic fiber cementum is
45-60%
cellular intrinsic fiber cementum
after half the root has been formed a less mineralized cementum is formed against the unmirezalllied dentine at the advancing root
cementoid
a layer of un mineralized matrix present on the surface of mineralized matrix is present called cementoid
cementocytes
as cementum deposition progress the cementoblast gets entrapped in the ecm secreted by cementoblast and now are called cementocytes.
they reside in lacuna and have canaliculi which does not form syncytium
cellular mixed fiber cementum
as PDL becomes organized, cementum keeps depositing around the ligament fiber bundles and that’s how they are in cooperated into the cementum and are partially mineralized so are called cellular mixed fiber cementum
sec0ndayr cementum is identifiable in microscope how
it has cementocytes lying in lacuna and have canaliculi directed towards the tooth surface
intrinsic fibers are uniformly mineralized where as extrinsic are not
the presence of cementoid on the surface
secondary cementum is not present in what teeth and is confined to
canine and incisor
apical and interradicular regions of the tooth
acellular afribrillar cementum
cementum has no collagen and its deposited on enamel and dentine in proximity to DEJ (does not take part in tooth anchoring)
2 ways that believed to form then acellular afribrillar cementum
caused by a developmental anomaly due to local disruption in the reduced enamel epithelium that permit follicular cells to come in contact with enamel and differentiate into cementoblast
HERS may form epithelial products that accumulate on the root surface and form this intermediate cementum
acellular afibril cementum is found
cervical enamel
extrinsic acellular fiber cementum found
cervical margin (50 micrometer) to two thirds of the root and in canine and incisor (only one found in this teeth) present till apical foramen (200 micrometer)
intrinsic cellular fiber cementum is found
apical third till interradicular regions of molar and pre molar till furcation
CEJ %
30% enamel and cementum meets at butt joint
10% have gap junction between them exposing root dentine
60% cementum overlaps enamel
exposure of root dentine can casue what issues
sensitivity
root caries
and idiopathic osteoclast mediated root resorption
alveolar process consist of
outer (buccal and lingual) cortical plate, central spongiosa and bone lining the alveolar (alveolar bone) n
the cortical plate and alveolar bone meet at
the alveolar crest
cribriform plate
the alveolar bone has inner and outer compartment that has many foramina that has vessels and nerves so thats why its called as cribriform plate
lamina dura
alevolar bone has increase radiopacity
bundle bone
the bone lining the sockets are called as the bundle bone
it has extrinsic collagen fiber bundles of pdl and less intrinsic collagen fibers than lamellar bone
it provides a site for attachment for PDL
cortical plate consist of
has an surface layer of lamellar layer with compact Haversian system
it is thinner in maxilla and thickest in buccal aspect of premolar and molars of mandible
central part consist
trabecular or spongy bone which also has a Haversian system with trabeculae
trabecular bone is absent in
anterior teeth and the cortical plate and alveolar bone is fused together
PDL CELL differentation
heterogenous population of mesenchymal cells and have cells that differentiate into osteoblast or cementoblast
also the perivascular and endosteal fibroblast that makes pdl cementum and bone
pdl is found where and its thinnest at what part
its a soft connective tissue present between the cementum of the root and the alveolar bone
thinnest in the middle third of the root
pdl width
0.15 to 0.38 mm
pdl width in diff age
- 21 mm from 11 to 16
- 18 mm from 32 to 52
- 15 mm from 51 to 67
PDL main cells
osteoblast, osteoclast, macrophages, fibroblast, undifferentiated mesenchymal cells, stem cells, cementoblast
PDL ground substances contains
glycosaminoglycans, glycoproteins and glycolipids
fibroblast and their ability
fibroblast are the principal cells of pdl and have the ability to achevive high rate or protein turn over the ecm specially collagen
fibroblast contains what as in organelles
they have extensive amount of cytoplasm with organelles involved in protein synthesis and secretions they also have a cytoskeleton mainly actin which allows the migration and change in shape of fibroblast
epithelial cells
they are ruminant of HERS, ERM WHICH are found near cementum. they maintain pdl and have a stem cell compartment that can give rise to various periodontium cells.
epithelial cells can be activated to make
epithelial and mesenchymal matrix proteins that take part in mineralization of tooth and bone
undifferentiated mesenchymal cells
they are a source of new PDL CELLS, fibroblast osteoblast and cementoblast.
stem cells
more easily available stem cells in pdl than in pulp
they differentiate into adipogenic, cemetogenic, osteogenic, and chondrogenic cells.
dentogingival group
attached from cervical cementum to the lamina propria of attached and free gingiva
alveologingival group
attached from the alveolar crest of bone to the lamina propria of attached and free gingiva
circular group
small groups of fibers, forms a band around the neck of the tooth and interlacing with other group of fibers and attached free gingiva to the tooth
dentoperiosteal group
run apically from cementum into the periosteum of the outer cortical plate and insert into alveolar process or vestibular muscle and floor of the mouth
transseptal fiber
run from the cemetum of one tooth apical to the base of epithelium junction over the alveolar crest and insert into the cemetum of another tooth
transseptal fiber system are a major cause of
postretention relapse of orthodontically positioned teeth
