Cementum

Question 1

What’s the role of the root cementum?

Answer 1

• attachment of PDL
• supports the tooth

Question 2

What’s cementum defined as… (type of tissue + where is is located)

Answer 2

Mineralised connective tissue that lines the root of the tooth
-between dentine and PDL

Question 3

What’s the composition of the 2 main types of cementum?

Answer 3

CELLULAR:
- cementocytes embedded in extracellular matrix
ACELLULAR:
- lacks cementocytes

Question 4

which type of cementum is formed first?

Answer 4

Acellular (covers most of root surface)

Question 5

Which type of cementum is formed fastest? And what can this mean for the incremental lines?

Answer 5

Cellular cementum
- incremental lines are further apart (more deposited per day)

Question 6

What’s the importance of cementum

Answer 6

• maintain and repair root surface
• connect dentine to PDL

Question 7

Where is cellular cementum deposited

Answer 7

Apical 1/3
Overlaying cementum

Question 8

What are the physical properties of cementum.
(colour, hardness, porosity?)

Answer 8

PHYSICAL:
- light yellow colour
- not as hard as enamel but harder than dentine
- porosity, allows for fluid exchange

Question 9

What’s the difference between primary and secondary cementum?

Answer 9

PRIMARY/ACELLULAR:
-formed first
-coronal region

SECONDARY/ACELLULAR:
-contains cementocytes embedded in extracellular matrix
-radicular region

Question 10

Where are cellular and acellular cementum distributed?

Answer 10

Cellular = apical 1/3 = radicular
Acellular = coronal

Question 11

What’s the meaning of intrinsic and extrinsic fibres in cementum?

Answer 11

Intrinsic = fibres only present within the cementum
Extrinsic = fibres inserted from the periodontal ligament into cementum

Question 12

What’s the meaning of AEFC, CIDC and CMSC in terms of fibres in cementum.

Answer 12

AEFC = acellular extrinsic fibre cementum
- Sharpey’s fibres
CIFC = cellular intrinsic fibre cementum
- no role in tooth attachment
CMSC = cellular mixed stratified cementum
- AEFC and CIDC both present in alternating layers

Question 13

What classifies as a Sharpey’s Fibre?

Answer 13

An extrinsic fibre that is produced from alveolar bone and passes through cementum also. (Comes into contact with both)

Question 14

What is special about the incremental lines in cementum and what are they called?

Answer 14

• unevenly spaced
• lines of salter

Question 15

What are the long term incremental lines called in cementum?

Answer 15

Striae of Retzius

Question 16

Outline the process of cementum resorption.

Answer 16

1. Stimulus = trauma
2. Activation of cells = odonto/cementoclasts (involved in resorption of mineralised bone)
3. Attachment = odontoblasts attach to surface of cementum and secrete enzymes
4. Resorption = enzymes break down the mineralised matrix.
5. Small cavities are left

Question 17

What’s the structure of the cementum-PDL interface?

Answer 17

• intrinsic + extrinsic fibres
• Sharpey’s fibres

Question 18

What’s the composition of cementum?

Answer 18

Hydroxyapatite
Extracellular matrix (Collagen type 1 & non-collagenous proteins)
Non-crystalline forms of calcium (demineralises easier)

Question 19

What triggers cementum resorption?

Answer 19

Masticatory forces cause micro-trauma = small areas of resorption.

Question 20

Outline cementum repair after resorption.

Answer 20

1. Mesenchymal stem cells from PDL or pulp to site of resorption
2. Stem cells differentiate into cementoblast-like-cells + deposit cementum
3. Mineralisation of newly formed matrix

Question 21

What’s the name of the line separating repair tissue and normal tissue in cementum?

Answer 21

Reversal line

Question 22

If there is resorption causing trauma is it likely to move into dentine or remain just in the cementum?

Answer 22

Remain in cementum