Periodontium

Question 1

What is the role of the periodontium?

Answer 1

• retain tooth in socket
• resist masticatory loads
• defensive barrier, protecting tissues against threats from oral environment

Question 2

What is the periodontium composed of?

Answer 2

Cementum
Gingiva
Alveolar bone
Periodontal ligament

Question 3

What is unique about the periodontium?

Answer 3

The only breach in the body’s surface is where the teeth pass through the oral epithelium

Question 4

What is the junctional epithelium?

Answer 4

A physical barrier separating the body tissues from the oral environment

Question 5

What are periodontal diseases divided into?

Answer 5

Diseases of the gingiva alone
Diseases of all the periodontal tissues

Question 6

What are periodontal diseases divided into?

Answer 6

Diseases of the gingiva alone
Diseases of all the periodontal tissues

Question 7

What are properties of cementum?

Answer 7

Covers root dentine
Similar in structure to bone
-Collagen matrix
-Lamellar arrangement
Provides attachment for some periodontal fibres
Laid down by cementocytes

Question 8

What are the two types of cementum?

Answer 8

Acellular
Cellular

Question 9

What are the properties of acellular cementum/extrinsic fibre?

Answer 9

No cells
Usually adjacent to dentine
First formed (primary cementum)
Contain collagen fibres from PDL (sharpeys fibres)
Present on cervical 2/3 of root

Question 10

What are the properties of cellular cementum/intrinsic fibre?

Answer 10

Contains cementocytes
Later formed (secondary cementum)
Present in the apical part of the root and in furcation regions
Normal collagen fibres present
No role in tooth attachment
May represent a transitional form

Question 11

What are the properties of the alveolar bone?

Answer 11

Similar to bone elsewhere in the body
Cortical (compact) plate forms inner lining of tooth socket
Inner cancellous bone containing marrow
Provides attachment for PDL fibres (sharpeys)
Has nutrient canals (volkmanns)
Supports the tooth

Question 12

What happens to alveolar bone when teeth are lost?

Answer 12

Alveolar process is resorbed leaving a residual ridge

Question 13

What part of the alveolar bone shows in radiographs?

Answer 13

Lamina dura

Question 14

What perforates the inner cortical bone?

Answer 14

Nutrient Formina

Question 15

What type of tissue is the PDL?

Answer 15

Fibrous connective tissue (derived from dental follicle)

Question 16

What does the PDL contain?

Answer 16

Cells
Extracellular Matrix
Fibres
Nerves
Blood vessels

Question 17

What is the ground substance of PDL made of and how does it behave?

Answer 17

Hyaluronate GAGs
Glycoproteins (fibronectin)
Proteoglycans (proteodermatan sulphate, dermatan sulphate, chondritin sulphate)

Behaves as a viscoelastic gel

Question 18

What cells are present in PDL?

Answer 18

Fibroblasts
Cementoblasts
Osteoclasts and cementoclasts
Immune cells
Debris of malassez (epithelial cells)

Question 19

What sensory nerves are present in the PDL?

Answer 19

Mechanoreceptors (a- beta, a- delta fibres)
Nociceptors (a-delta, C fibres)

Question 20

What are the qualities of the mechanoreceptors?

Answer 20

Rapidly or slowly adapting
Proprioception; chewing control

Question 21

What are the qualities of the nociceptors?

Answer 21

Protective reflexes; inhibit jaw elevator motor neurones

Question 22

What are the autonomic nerves of the PDL

Answer 22

Sympathetic
For blood vessel control -vasoconstriction

Question 23

What is the blood supply of the PDL?

Answer 23

Inferior/ superior alveolar arteries passing into PDL from alveolar bone
Lingual and palatine arteries supplying gingivae

Question 24

What are the two types of PDL fibres?

Answer 24

True PDL fibres
Gingival ligament fibres

Question 25

What are the true fibres?

Answer 25

Fibres connecting tooth to bone at or apical to alveolar crest

Question 26

What are the gingival fibres?

Answer 26

Fibres mainly above the alveolar crest including free gingival fibres

Question 27

What is the role of the PDL?

Answer 27

Attaches tooth to jaw Transmits biting forces to alveolar bone Organised regular connected tissue

Question 28

What is the width of the PDL?

Answer 28

0.2mm

Question 29

What are the fibres present in PDL

Answer 29

Collagen (types 1 and 3) Oxytalan

Question 30

What is the role of each fibres?

Answer 30

Collagen = principal fibres found in true periodontal ligament, support tooth in load bearing Oxytalan = present in human PDL, function is uncertain

Question 31

What are the fibre groups found in the alveolo-dental ligament? (In the tooth)

Answer 31

Alveolar crest Horizontal Oblique Apical Inter radicular (between roots of tooth)

Question 32

What are fibres found in the interdental ligament (between teeth)?

Answer 32

Transseptal

Question 33

What are the fibres found in the gingiva and where are the present?

Answer 33

Support the free gingiva Present in lamina propria in marginal gingiva -dento-gingival -alveolo-gingival -dentó-periosteal -circular

Question 34

What is the crevicular epithelium (oral sulcular epithelium)?

Answer 34

Epithelium that covers the sulcus. It is not attached to enamel (between the junctional epithelium and the gingival epithelium)

Question 35

What is the junctional epithelium?

Answer 35

Epithelium that is attached to the enamel/tooth

Question 36

What is the enamel cuticle?

Answer 36

Demineralised coating of enamel. Covers tooth once it has erupted by is worn away by mastication and cleaning

Question 37

What are the histológicas features of the junctional epithelium?

Answer 37

Has gap junctions, hemidesmosomes, desmosomes Has two basal laminas - one near the enamel, one near the lamina propria

Question 38

What is the inter-dental col?

Answer 38

Non keratinised epithelium that in the Inter proximal valley between two teeth

Question 39

What forces is the PDL subjected to?

Answer 39

Mastication Swallowing Speech Para function (clenching, grinding)

Question 40

What are horizontal, extrusive forces that the PDL is rarely subjected to?

Answer 40

Sticky foods Orthodontic forces

Question 41

What happens to a tooth when a load is applied initially?

Answer 41

Displaced initially into the socket

Question 42

What happens to loading after a bit?

Answer 42

After the initial elastic component, viscous creep happens due to the viscoelastic properties of PDL

Question 43

What happens in PDL during loading?

Answer 43

Tension in PDL fibres Compression of ECF

Question 44

In a displacement graph, what happens under disease conditions for the PDL?

Answer 44

Movement becomes linear

Question 45

In which direction do the principal oblique fibres lie, relative to the alveolar bone and cementum?

Answer 45

They attach to the cementum apically and to the bone cervically This arrangement facilitates the transfer of forces, applied to the tooth, to be absorbed to the bone.

Question 46

What is the main protein in the principal (Sharpey's) fibres?

Answer 46

Collagen, types I and III

Question 47

What types of cementum can you see in the root of the tooth?

Answer 47

Acellular extrinsic Cellular intrinsic

Question 48

In which part of the root the cementum is thicker?

Answer 48

Apical part of the root

Question 49

The shape of principal oblique fibres are?

Answer 49

Wavy

Question 50

What cells lie in the cementum surface?

Answer 50

Cementocytes

Question 51

What is the main cell type at the centre of the periodontal ligament ?

Answer 51

Fibroblasts

Question 52

On which side of the periodontal ligament are the Sharpey fibres bundled more closely?

Answer 52

At the cementum

Question 53

What is the name of these clusters of epithelial cells found near cementum?

Answer 53

Rests of malassez

Question 54

What are the epithelial cells found in periodontal ligament responsible for?

Answer 54

Periaapical cyst