Periodontium Flashcards
periodontium is composed of?
all the tissues that surround and support the tooth:
1) gingiva
2) periodontal ligament
3) cementum of root
4) alveolar bone
Define cementum
- mineralized CT covering the root
- attachment point for gingiva and PDL fibers
- protect dentin from pain
- compensates for occlusal wear
- NOT vascular and exhibits little turnover
growth of cementum
GROWS SLOWLY
1) prefunctional stage
- -throughout root formation
2) functional stage
- -starts with tooth in occlusion
where is cememtum located?
begins at the cervical portion of the tooth at the cemento-enamel juntion and continues to the apex. continuous deposition of cementum in the apical region compensates for rapid wear at the occlusal surface
cementum based on time of formation
- primary cementim= formed before eruption
* secondary cementum= formed after eruption
cementum by location
- radicular cementum= fond on root surface
* coronal cementum= enamel covering the crown
cementum based on cellularity
- cellular= contains cementocytes in LACUNAE within the cementum matrix (apical third)
- acellular= NO CELLS, cervical third
cementum based on collagen fibrils
- fibrillar= well defined fibrils of type ONE collagen
* afibrillar= devoid of detectable type 1. fine and granular; no fibers
extrinsic fiber cementum
originally produced by PDL fibroblasts*
- SHARPEY’s fibers that are continuous with principle fibers of PDL
- major role in tooth ANCHORAGE
intrinsic fiber cementum
produced by cementoblasts
- PARALLEL to the cementum
- sites undergoing REPAIR and adaptation; no anchorage!
how is cementum classified into cellular or acellular?
by inclusion or non-inclusion of cementocytes
acellular cementum
thin
- covers cervical root
- (possible coronal and middle 3rd of root)
cellular cementum
thick
-covers apical root
what are the 3 major types of distinguishable cementum?
1) acellular extrinsic fiber cementum (AEFC)
2) cellular intrinsic fiber cementum (CIFC)
3) cellular mixed stratified cementum (CIFC)
acellular extrinsic fiber cementum (AEFC)
- primary cementim
- coronal 2/3 of rrot
- extrinsic fibers
- no cementocytes
- acellular cementum
- produced by fibroblasts of PDL; aka Sharpey’s fibers
- horizontal fiber structure
cellular intrinsic fiber cementum (CIFC)
- secondary cementum
- produced by cementoblasts in LACUNAE
- canaliculi oriented toward PDL
- apical 1/3 of root
- mostly intrinsic fibers
- cementoblasts
cellular mixed stratified cementum (CMSC)
both AEFC and CIFC
- both intrinsic and extrinsic
- both cellular and acellular
Sharpey’s fibers
- embedded in alveolar one
- less distinct in cementum
- pass between cementoblasts to enter dementum
is aceullar or cellular portion of dentin more thick?
cellular
how much of cementum is organic or inorganic?
- inorganic= 45-50%; calcium phosphate in the form of hydroxyapatite crytals
- organic= 50-55%; collagen fibers, protein, polysaccharides
4 mineralized tissues are found in the oral cavity and 3 of them are components of the tooth. what are they?
cementim
dentin
enamel
90% of cementum is what type of collagen?
type 1
cementum formation takse place along the entire root, however its initiation is limited to?
the advancing root edge which Hertwig’s epithelial root sheath
what does Hertwigs epithelial root sheath do?
sends an inductive message, possibly by secreting some enamel proteins or other epithelial product to pulp cells;which differentiate into odontoblasts and produce a layer of predentin
what is ‘epithelial cell rests of Malassez’?
cells from fragmented root sheath form discrete masses surrounded by a basal lamina, which persist in mature PDL
the principle fibers of the periodontal ligament are continuous with the?
Sharpey’s fibers of the cementum
enamel organ-derived cells are capapble of producing mesenchymal products such as ?
collagen type 1
bone sialoprotein
osteopontin
what are genes that control extracellular pyrophosphate?
ank and PC-1
*mutations in these genes lead to formation of cellular cementum even at early stages of root development
what is phosphate important for?
contorlling rate of cementum formation
define periodontal ligament
soft CT between alveolar bone proper and cementum. tooth attachment; support and cushion; sensory organ
define alveolar bone
mineralized CT lining socket. Serves as attachment for PDL fiber (embedded in alveolar bone)
