Week 5 - Cementum

Question 1

What is cementum made of?

Answer 1

Nearly 50/50 organic/inorganic split

Question 2

What are the organic components of cementum?

Answer 2

• Type I collagen (intrinsic and Sharpey’s fibers)
• Proteoglycans
• Glycosaminoglycans
• Phosphoproteins

Question 3

What does cementum provide an attachment for?

Answer 3

The PDL through sharpey’s fibers

Question 4

How does cementum provide compensation for occlusal wear?

Answer 4

Through continuous apical apposition
- as the tooth wears down, reparative dentin lays down to stabilize

Question 5

What may cementum participate in?

Answer 5

Repair of root fracture

Question 6

What is the origin of cementum?

Answer 6

Ectomesenchymal

Question 7

What is the quantity of mineral comparison of cementum, bone and dentin?

Answer 7

Cementum contains less mineral than both bone and dentin

Question 8

Is cementum vascular?

Answer 8

Avascular, not innervated, and contains no haversion or volkmann’s canals

Question 9

Where is cementum the thinnest?

Answer 9

At the CEJ (30-50 µm)
and progressively increases in thickness to 90-150 µm at mid-root to 150-300 µm at the apex

Question 10

What are cementoblasts responsible for?

Answer 10

secretion of the organic matrix of cementum

Question 11

What are cementoblasts derived from?

Answer 11

undifferentiate mesenchymal cells that originate in the proximal (inner) zone of the dental follicle

Question 12

What are all cells in the dental follicle derived from?

Answer 12

Ectomesenchyme (neural crest cells)

Question 13

How is differentiation initiated with?

Answer 13

disruption of Hertwig’s
epithelial root sheath, allowing the undifferentiated mesenchymal cells to make contact with the adjacent dentin

Question 14

What induces differentiation process?

Answer 14

Dentin matrix growth factors (BMP, FGF, DMP)

Question 15

What does hertwig’s root sheath contain for the mesenchymal cells to enter?

Answer 15

Perforations that make contact with growth factors and come from pulp through holes

Question 16

What are histological features of cementum?

Answer 16

• Depositional lines
• Reversal lines
• Cementoblasts
• Cementocytes
• Lacunae
• Canaliculi
• Sharpey’s fibers (PDL)

Question 17

What do depositional and reversal lines indicate?

Answer 17

Incremental growth, and run longitudinally within the cementum

Question 18

What are the types of cementocytes?

Answer 18

Lacunae and canaliculi

Question 19

What are lacunae?

Answer 19

Space occupied by cell

Question 20

What are canaliculi?

Answer 20

Space occupied by cytoplasmic projections
- fingerlike projections; may help with intercellular communications

Question 21

What are insertion points that suspend the tooth in space?

Answer 21

Sharpey’s fibers

Question 22

What are the different ways cementum can meet enamel at the CEJ?

Answer 22

Overlap
End to end
Gap

Question 23

What is abfraction?

Answer 23

Loss of tooth surface at the cervical areas of teeth

Question 24

What is abfraction caused by?

Answer 24

Tensile and compressive forces during tooth flexure

Question 25

What does abfraction affect?

Answer 25

Buccal/labial cervical areas of teeth

Question 26

What does abfraction look like?

Answer 26

Deep, narrow V=shaped notch

Question 27

What teeth does abfraction affect?

Answer 27

Single teeth with excursive interferences or eccentric occlusal loads

Question 28

What is abrasion?

Answer 28

Loss by wear of dental tissue caused by abrasion by foreign substance (e.g. toothbrush)

Question 29

Where is abrasion usually located?

Answer 29

at cervical areas of teeth

Question 30

What do abrasion lesions look like?

Answer 30

More wide than deep

Question 31

What teeth are commonly affected with abrasion?

Answer 31

Premolars and cuspids

Question 32

What are cementicles?

Answer 32

Calcified bodies appearing on or in the cementum and in the PDL

Question 33

What are cementicles classified as?

Answer 33

free, attached or embedded

Question 34

What are cementicles a response to?

Answer 34

local trauma or hyperactive occlusion and appear in increasing numbers with increasing age

Question 35

What are cemental spurs?

Answer 35

Projections of cementum (trauma response)

Question 36

What does exposed cementum prevent and why?

Answer 36

It is hypermineralized which prevents reattachment of collagen - not as poreous so collagen and sharpey's fibers have trouble reattaching

Question 37

What does exposed cementum facilitate attachment of?

Answer 37

Plaque and calculus

Question 38

What absorption does exposed cementumf acilitate?

Answer 38

Endotoxin absorption into cementum

Question 39

What is this?

Answer 39

Calculus attachment to cementum

Question 40

How does scaling and root planing benefit cementum?

Answer 40

Removes biofilm and cementum deposits

Question 41

What is hypercementosis?

Answer 41

The excessive production of cellular cementum that generally involves the apical 1/3 of the root

Question 42

What is the etiology of hypercementosis?

Answer 42

variable involving such factors as trauma from occlusion, periapical inflammation, or compensation for occlusal attrition

Question 43

What are accessory canals beneficial for?

Answer 43

Vasculature to reach tissues which helps if there is a crack in the tooth so cementocytes can move via accessory canals

Question 44

Where are accessory canals located?

Answer 44

More in the apex of the tooth (apical fracture has more help with healing) - in multirooted teeth, the canal is in furications