Cementumπ Flashcards
what is the periodontium
supporting tissues of teeth which include cementum, PDL, alveolar bone, part of gingiva facing tooth
what is cementum
thin layer covering radicular dentin ( root dentin)
cementum is vascular true or false
false its avascular
cementum is alympahtic true or false
true
cementum is innervated true or false
false noninnervated
why is cementum not normally resorbed unlike bone
cementum is avascular and has low metabolic rate make it less responsive to resorptive signals
how thick is the cementum
thickest: root apex and interradicular areas of multirooted teeth 50-200
thinnest: CEJ 10-50
list functions of cementum
- provides attachment for PDL collagen fibers
- protects underlying dentin
- maintains PDL space by apposition of new cementum
- repairs root fracture by forming new cementum
list the physical properties of cementum
-pale yellow with dull surface
-softer than dentin and bone
- more permeable than dentin
how does age affect permeability of cementum
the permeability of cementum decreases by age
what is the inorganic and organic composition of cementum
inorganic: 45-50% mostly hydroxyapatite crystals
organic : 50-55% ( collagen Type I, non collagenous proteins , and water)
what types of collagen are present in cementum
type I,III,XII (traces of V, VI,XIV)
what are the noncollagenous proteins in cementum
alkaline phosphatase
bone sialoprotein
fibronectin
other bone proteins
which glycoaminoglycans are found in cementum
chondroitin sulfate
heparan sulfate
what are growth factors are associated with cementum
insulin like growth factors
cementum derived growth factors
what structural components are present in cementum
cells( ex. cementoblast, cementocytes, cementoclast)
Matrix: fibers ( intrinsic , extrinsic, and mixed ) and ground substance ( water , proteins β glycoproteins and proteoglycansβ , minerals β hydroxyapatite which is smaller and shorter than enamel)
where do cementoblasts originate
undifferentiated ectomesenchymal cells of dental sac
when do cementoblasts arise
if dentin exposed to surrounding tissues
what do cementoblasts secrete and where are they located
secrete cementoid ( cementum matrix)
found on the surface of forming cementum
what happens to cementoblasts after they are trapped in matrix
they become cementocytes
how do cementocytes get nutrients
gets nutrition from blood vessels of PDL by their cytoplasmic processes which are called canaliculi
What are odontoclasts and what is their function
resemble osteoclast and originate from monocytes
Resorb dental hard tissues especially during primary tooth replacement
what are the 3 types of fibers in cementum
Intrinsic fibers : secreted by cementoblasts , run parallel to root surface and smaller than extrinsic
Extrinsic fibers : From PDL fibroblast ( sharpeys fibers ) run perpendicular to cementum surface and alveolar bone surface
Mixed fibers : Combination of intrinsic and extrinsic fibers
how is cementum classified based on the presence of cells
Acellular cementum : No cells , slow formation , first deposited at the DCJ
Cellular cementum : cementocytes , rapidly formed in apical third
how is cementum is classified based on time of formation
Primary cementum : acellular , covered root near CEj
Secondary cementum : Cellular , located in apical third of root
Reparative
whats the difference between acellular and cellular
acellular has no cementocytes and its the 1st layer it forms slowly and cellular is last layers which contains cementocytes forms rapidly
what is primary cementum and when is it formed
first cementum to form usually acellular
formed slowly with mineralized fibers during root formation until teeth come into function covering cervical two third of root
what is the new classification name for primary cementum
acellular extrinsic fiber cementum
what is secondary cementum and when is it formed
formed during functioning phase of teeth until exfoliation
compensates for loss of tooth material during mastication
what is the new classification name for secondary cementum
cellular intrinsic fiber cementum
where is secondary cementum found and how is it formed
apical third of root and interradicular areas ad forms rapidly making it cellular with cementoid on outer surface
what are resting lines in secondary cementum
waves or lines seen between new and old cementum due to layered formation
what is reparative cementum and when is it formed
forms as histological repair of cementum due to trauma or fracture and damaged cementum is removed by odontoclasts and new cementum is laid down by cementoblasts
does cementum remodel like bone
no, cementum doesnβt undergo continuous remodeling but can repair itself
what prevents reparative cementum from forming during ortho treatment
excessive orthodontic forces prevent formation of reparative cementum
what is afibrillar cementum and where is it found
no collagen fibers, thin and acellular
composed of well mineralized ground substance and covers cervical enamel or located between cementum and dentin
what is intermediate cementum
separates dentin from cementum to protect dentin.
originates from inner enamel epithelium (IEE), contains enamel proteins, and forms the hyaline layer.
what structures are part of intermediate cementum
Acellular cementum , hyaline layer , Tomβs granular layer , and radicular dentin .
what are the three patterns of the cemento-enamel junction (CEJ), and their percentages
Overlap: Cementum overlaps enamel (60%).
Meet: Cementum meets enamel (30%).
Gap: Gap between cementum and enamel (10%)
what is cementogenesis
Development of cementum from the dental sac after Hertwigβs root sheath disintegration.
Contact between dental sac cells and root dentin induces differentiation into cementoblasts on root surface.
how is cementoid formed and mineralized during cementogenesis
cementoblasts secrete cementoid over root dentin.
cementoid becomes mineralized to form cementum.
cementoblasts may become entrapped and turn into cementocyte
what forms the dentino-cemental junction (DCJ)
Apposition of cementum over dentin
what are the similarities between cementum and bone
Both have a fibrous framework.
Both contain a matrix.
Both have similar crystal shapes.
Developmental processes are alike.
what are the differences in inorganic content between cementum and bone
Cementum: 45% inorganic calcium.
Bone: 65% inorganic calcium
what are the differences in collagen types between cementum and bone
Cementum: Type I and III collagen.
Bone: Type I collagen.
how does cementum receive nutrition compared to bone
Cementum: Avascular, gets nutrition from the periodontal ligament (PDL).
Bone: Vascular, has its own blood supply
does cementum have nerves like bone
Cementum has no nerves.
Bone contains nerves.
what is hypercementosis
Increased thickness of cellular cementum.
Seen as an abnormal thickening near the cemento-dentine junction.
what is hypophosphatasia and how does it affect cementum
A rare genetic disease affecting teeth and bones.
Cementum is sensitive to a lack of Alkaline Phosphatase.
Results in absence of cementum, leading to premature tooth loss.
what are enamel pearls, and how do they form
Form due to remnants of Hertwigβs epithelial root sheath failing to separate from dentin.
Continue secreting enamel, preventing normal root covering by cementum
why are enamel pearls clinically significant
Can cause bone destruction, inflammation, and periodontal pocket development.
Detected through routine X-rays.
Need surgical removal to ensure proper plaque control
