15 - Morphology of dental cementum

Question 1

Cementum

Answer 1

Hard avascular CT that covers roots of tooth

CEJ ⇢ located at cervical margin

• 30% edge - edge
• 60% cementum overlaps enamel
• 10% gap between enamel + teeth

Question 2

Classifications of cementum: By location

Answer 2

• Radicular cementum ⇢ Found on root surface
• Coronal cementum ⇢ Forms on enamel covering crown

Question 3

By cellularity

Answer 3

• Cellular ⇢ cementum containing cementocytes within matrix
• Acellular ⇢ Cementum without cells in matrix

Question 4

By presence of collagen fibrils in matrix

Answer 4

• Fibrillar ⇢ cementum w/2 matrix that contains well defines collagen I fibres
• Afribrillar ⇢ Matrix without collagen fibrils but has granular consistency

Question 5

By origin of matrix fibres

Answer 5

• Extrinsic (role in tooth anchorage) ⇢ Cementum that contains extrinsic fibres ⇢ Sharpey’s fibres
• Intrinsic ⇢ Cementum that contains mainly intrinsic fibres ⇢ Cementocytes
• Mixed

Question 6

Cementum varieties - Acellular Afibrillar cementum

Answer 6

• Mostly mineralised matrix
• No fibrils + No cementocytes
• Produced by cementoblasts
• Typically found as Coronal epithelium - close to DEJ

Question 7

Acellular extrinsic fibre cementum

Answer 7

• Matrix has well defined collagen I fibrils
• Contains Sharpey’s fibres
• Located at cervical ⅔ of root
• anchors tooth to periodontal ligament

Question 8

Cellular intrinsic fibre cementum

Answer 8

• contains cementocytes in a matrix of almost only intrinsic fibres
• Located at sites of cementum repair
• Plays no role in tooth anchorage
• Deposited once tooth is in occlusion:
• As deposition progresses ⇢ cementoBLASTS trapped in matrix that they secrete ⇢ become cementoCYTES
• They have processes that lodge in canaliculi ⇢ never extend all the way to the surface

Question 9

Cellular mixed fibres cementum

Answer 9

• Found on apical ⅓ of root
• Formation of cementum more rapid here
• Sharpey’s fibres run more irregularly + more distinguishable than in AEFC
• Cementoblasts are trapped in lacunae ⇢ become cementocytes here

Question 10

Intermediate cementum

Answer 10

• thin + amorphous non-cellular layer of hard tissue
• Deposited by follicular cells of root sheath
• After deposition ⇢ follicular cells disintegrate + migrate into periodontal tissue

Question 10

Intermediate cementum

Answer 10

• thin + amorphous non-cellular layer of hard tissue
• Deposited by follicular cells of root sheath
• After deposition ⇢ follicular cells disintegrate + migrate into periodontal tissue