Cementum𐙚 Flashcards by dalia ahmed

what is the periodontium

supporting tissues of teeth which include cementum, PDL, alveolar bone, part of gingiva facing tooth

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what is cementum

thin layer covering radicular dentin ( root dentin)

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cementum is vascular true or false

false its avascular

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cementum is alympahtic true or false

true

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cementum is innervated true or false

false noninnervated

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why is cementum not normally resorbed unlike bone

cementum is avascular and has low metabolic rate make it less responsive to resorptive signals

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how thick is the cementum

thickest: root apex and interradicular areas of multirooted teeth 50-200
thinnest: CEJ 10-50

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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

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list the physical properties of cementum

-pale yellow with dull surface
-softer than dentin and bone
- more permeable than dentin

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how does age affect permeability of cementum

the permeability of cementum decreases by age

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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)

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what types of collagen are present in cementum

type I,III,XII (traces of V, VI,XIV)

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what are the noncollagenous proteins in cementum

alkaline phosphatase
bone sialoprotein
fibronectin
other bone proteins

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which glycoaminoglycans are found in cementum

chondroitin sulfate

heparan sulfate

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what are growth factors are associated with cementum

insulin like growth factors

cementum derived growth factors

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what structural components are present in cementum

cells( ex. cementoblast, cementocytes, cementoclast)

Matrix: fibers ( intrinsic , extrinsic, and mixed ) and ground substance ( water , proteins “ glycoproteins and proteoglycans” , minerals “ hydroxyapatite which is smaller and shorter than enamel)

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where do cementoblasts originate

undifferentiated ectomesenchymal cells of dental sac

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when do cementoblasts arise

if dentin exposed to surrounding tissues

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what do cementoblasts secrete and where are they located

secrete cementoid ( cementum matrix)

found on the surface of forming cementum

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what happens to cementoblasts after they are trapped in matrix

they become cementocytes

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how do cementocytes get nutrients

cementocytes get their nutrition from blood vessels in the periodontal ligament (PDL) through their cytoplasmic processes, which extend into tiny channels 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 (collagen type 1) , 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 n absence 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 doesn't 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 hyaline layer.

what structures are part of intermediate cementum

Acellular cementum , hyaline layer , Tom’s 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 Hertwig's 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 Hertwig's 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