Periodontium 1 Cementogenesis & Cementum

Front 1

What is Cementum ?

Back 1

• A mineralized dental tissue which covers the root dentine and is simultaneously part of the periodontium.

Front 2

What is the mineral content of Cementum?

Back 2

• It is about 65%mineralized/inorganic material (most significantly, crystalline Ca hydroxyapatite), 23% organic material and 12% water by weight.
• By volume: 45% inorganic, 33% organic and 22% water.

Front 3

What is the thickets part of cementum?
What is the thinnest part of cementum?

Back 3

• Thickest around the apices and furcations (50 – 200 microns)
• Thinnest about the CEJ (10 – 50 microns).

Front 4

What is Cementogenesis?

Back 4

• The apposition and maturation of cementum

Front 5

What begins root development?

Back 5

The cervical loop (IEE and OEE, but no stratum intermedium or stellate reticulum) grows further down (“apically”) to slightly encompass the dental papilla and forms Hertwig’s root sheath.

Front 6

What does Hertwig’s root sheath induce?

Back 6

Differentiation of underlying mesenchymal cells to form odontoblasts in much the same way as is done coronally,

Front 7

Hertwig’s root sheath extends apically, why?

Back 7

Produce anatomy of the root and development of the root dentine.

Front 8

What happens to the underlying basement membrane and root sheath as each stage of dentine is completed?

Back 8

The underlying basement membrane and the root sheath disintegrates.

Note - Root sheath remnants remain as islands of cells known as Epithelial rests of Malassez.

Front 9

How are cementoblasts produced?

Back 9

The contact of the root dentine with the undifferentiated mesenchymal cells of the dental sac induces differentiation of these cells to become cementoblasts.

Front 10

What induces to cementoblasts?

Back 10

• Undifferentiated mesenchymal dental sac cells induced to cementoblasts.

Front 11

What do Cementoblasts secrete?

Back 11

• A matrix called cementoid.

Front 12

What are Cementocytes?

Back 12

• Some cementoblasts become entrapped within lacunae in this matrix and are referred to as cementocytes.

Front 13

How is cementum produced?

Back 13

• Maturation of this matrix occurs and the mineralized end product is cementum.

Front 14

The two classifications of Cementum?

Back 14

• Cellular (cells) or Acellular (no cells).

• Intrinsic or Extrinsic.

Front 15

Acellular cementum is the first layer deposited at the
DCJ. It is also referred to as...

Back 15

Primary cementum.

Note - One layer at least will cover all of the root.

Front 16

Characteristics of acellular cementum -

Back 16

• There are no entrapped cementocytes.
• Relatively slow deposition.
• There may be many layers in the cervical one third.
• The width of this primary layer never changes

Front 17

Another name for Cellular Cementum

Back 17

Also called secondary cementum.

Front 18

Characteristics of cellular cementum -

Back 18

• Cementocytes entrapped in lacunae.
• More rapidly deposited.
• Most often seen in the apical two thirds, especially in
teeth in function.
• Cementoblasts at junction of cementum and PDL can
continue deposition of cellular cementum (increases width over lifetime).

Front 19

Cementum Distribution -

Back 19

Front 20

Types of Cementum

Back 20

Front 21

3 Types of Cementum Fibres -

Back 21

• EXTRINSIC - the PDL (Sharpey’s fibres).
• INTRINSIC - the cementoblasts.
• MIXED FIBRES - both extrinsic and intrinsic.

Front 22

Direction of the fibres?

Back 22

• Intrinsic fibres - run parallel to the root surface.

• Extrinsic fibres - run comparatively perpendicular to the root.

Front 23

Clinical considerations -
• Cementum is more resistant to resorption than bone. What does this allow?

Back 23

• The application of an orthodontic force to move a tooth through alveolar bone.

Front 24

Clinical considerations -
• What does the permeability of cementum allow?

Back 24

• The surface layer to become infected in the presence of periodontal disease.

Front 25

Clinical considerations -
• When dealing with an avulsed tooth, it is crucial to maintain the vitality of the cementum and attached fibres. Why?

Back 25

• This means that minimising the length
of time that the tooth is outside of the periodontium is critical to the success of the reimplantation.

Front 26

Clinical considerations -
What give cementum the capability to repair?

Back 26

• Cementum, being a vital tissue with ongoing growth throughout the life of the tooth.

Front 27

Clinical considerations -
Why must the extraction of teeth must always be preceded with a radiograph.?

Back 27

• Hypercementosis

Front 28

Clinical considerations -
What are Cementicles?

Back 28

• Cementicles are additional “blobs” of cementum that may be attached to the root surface, or found free in the PDL.

•Thought to result from micro trauma which increases the loading on Sharpey’s fibres which in turn, tears the cementum creating debris which acts as a nucleus of calcification.

Front 29

Clinical considerations -
Where are Cementicles found?

Back 29

Most commonly found in the apical and
middle thirds of the root, or in the
furcation.