Periodontium tutorial

Question 1

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

Answer 1

The principal PDL fibres run obliquely from the alveolar bone to the cementum. The bone attachment of a given fibre bundle is more cervically placed than the cementum attachment, which is more apical.

Question 2

What is the advantage of the orientation of the principal (oblique) periodontal fibre

Answer 2

Only with this arrangement can the biting forces be transmitted and dissipated to bone.

Question 3

What is the main protein in the principal fibres

Answer 3

collagen - types 1 and 3

Question 4

What types of cementum can you see on the root of the tooth? Where are they located?

Answer 4

Acellular cementum is found on all parts of the root. Cellular cementum is usually found in the apical half of the root and in furcation regions (not seen in this slide).

Question 5

in which part of the root is the cementum layer thickest

Answer 5

apex

Question 6

what structures pass through gaps in the inner cortical plate of alveolar bone

Answer 6

Blood vessels pass through nutrient canals (Volkmann’s canals). These can be seen in a dried skull penetrating the bone lining the tooth socket.

Question 7

How does cementum differ from bone?

Answer 7

Cementum is avascular and has no innervation. It is also less readily resorbed. All these aspects are relevant during orthodontic tooth movement, when bone must be remodelled without damaging cementum.

Question 8

What is the usual relationship between cellular and acellular cementum? What type of variations from this relationship can occur?

Answer 8

Usually, cellular cementum overlies acellular cementum. However, the reverse can occur. An also common feature is to have a sequence of various alternating layers of cellular and acellular cementum. This is especially true at the apex.

Question 9

The periodontal space is frequently described as of an hourglass shape. Can you explain why?

Answer 9

Lateral occlusal forces are transmitted and dissipated by a lever mechanism where the fulcrum or hinge is located at the mid third of the root. Therefore, the periodontal space is wider at the force source (cervical region of the root) and the dissipation area (apex) while being narrower at the fulcrum (the median portion).

Question 10

are collagen fibres straight or wavy and why

Answer 10

wavy

This allows a small amount of tooth movement before the tissue is placed under tension (in association to crimping).

Question 11

In view of Sharpey’s fibres contribution to the cementum, what other name is used for these embedded fibres?

Answer 11

Extrinsic fibres of cementum.

Question 12

What cells lie on the cementum surface, and what is their function?

Answer 12

Cementoblasts. These form cementum. Some cementoblasts become trapped in the cementum; they are then called cementocytes. They are equivalent to osteocytes in bone.

Question 13

In the centre of the periodontal ligament, what is the main cell type?

Answer 13

Fibroblasts.

Question 14

what is the main function of the fibroblasts

Answer 14

Fibroblasts are involved in formation and degradation of collagen fibres and in forming ground substance of the PDL.

Question 15

On which side of the PDL are the fibre bundles larger/thicker?

Answer 15

They are larger/thicker on the bone side.

Question 16

On which side of the PDL are the fibre bundles closer together?

Answer 16

They are closer together on the cementum side.

Question 17

What is the advantage of this fibre bundle arrangement?

Answer 17

Forces from the tooth are spread and dissipated into a larger bone area. 12.

Question 18

Describe collagen crimping and what the proposed function of it is.

Answer 18

Collagen fibres have an alternate wavy pattern under polarised light. This is further to the already mentioned wavy pattern of the periodontal fibres. Crimping is involved on the early dissipation of tooth movement before the tissues are placed under stress.

Question 19

fibre groups pass from cementum to bone in different directions in a vertical plane but also in a horizontal plane - what is the advantage of this arrangement

Answer 19

Allows the tooth to resist rotational forces.

Question 20

Which group of fibres can be seen in the interdental region that isn’t present on the labial and lingual aspects of the periodontium?

Answer 20

Transseptal fibres

Question 21

Which group of fibres can be seen on the labial and lingual aspects of the periodontium that isn’t present in the interdental region?

Answer 21

Alveolar crest fibres.

Question 22

Which fibres are not attached to bone?

Answer 22

Transseptal fibres and gingival fibres.

Question 23

Which fibres are not attached to bone or tooth?

Answer 23

Circular free gingival fibres.

Question 24

what is the dental gingival function

Answer 24

The dento-gingival junction is clinically a very important area. It is the boundary between the oral cavity and the underlying connective tissue of the tooth-supporting tissues

Question 25

what type of epithelium is the oral gingival epithelium

Answer 25

It is a stratified squamous, keratinised epithelium

Question 26

What are the major differences between the oral gingival epithelium and the sulcular epithelium?

Answer 26

The sulcular epithelium is thinner and has no keratinised layer. In addition, the rete ridges are fewer, or absent, and project less deeply into the connective tissue.

Question 27

On the root surface, what tissue lies apical to the junctional epithelium?

Answer 27

Cementum. You should be able to see the alveolar crest fibres of the periodontal ligament attached to it.

Question 28

What influence might periodontal disease have on the position of the junctional epithelium?

Answer 28

The junctional epithelium attachment will move apically, creating an enlarged (deepened) gingival sulcus. This enlarged space is now called a true periodontal pocket, which patients can find difficult to clean. (How does this differ from a ‘false pocket’?)

Question 29

Of what type(s) of epithelium(a) are the junctional and sulcular epithelia?

Answer 29

junctional epithelium consists of a single layer of cuboidal cells overlying several layers of flattened cells.

Question 30

What is the major structural difference between the two epithelia?

Answer 30

Junctional epithelium is considerably thinner than sulcular epithelium and in life was attached to enamel.

Question 31

What unusual feature does the junctional epithelium exhibit?

Answer 31

The junctional epithelium has two basal laminae – one which joins with the underlying connective tissue, and the other on the superficial aspect which joins to enamel. The latter junction involves hemidesmosomes.

Question 32

What shape is the interface between the junctional epithelium and the underlying connective tissue?

Answer 32

There are no rete ridges present and, therefore, the junction between the two tissues is smooth. 5.
In health, the interface between the sulcular epithelium and the connective tissue should exhibit considerably fewer rete ridges than the oral gingival epithelium. In this section, however, as in most sections of this area, chronic inflammation has modified the structure. In the connective tissue immediately below the epithelium there is an inflammatory cell infiltrate. The sulcular epithelium shows some hyperplasia in response to this irritation.

Question 33

how does the oral gingival epithelium compare in thickness with the sulcular epithelium

Answer 33

The oral gingival epithelium is thicker.

Question 34

What shape is its (oral gingival epithelium) junction with the underlying connective tissue

Answer 34

Similar to oral gingival epithelium elsewhere, there are numerous rete ridges.

Question 35

what is the free gingival groove

Answer 35

demarcates the free gingiva and the attached gingivae

Question 36

The majority of the tooth tissue present is an unerupted permanent tooth below a portion of interdental gingivae (of a primary tooth) that extends from the buccal to the lingual aspects. Also present are the resorbing roots of the primary molar. Look at the layer of cells on the outer aspect of the enamel space around the crown of the permanent tooth. what is this layer and what cells contribute to it

Answer 36

Reduced enamel epithelium, formed from amelolasts, stratum intermedium and outer enamel epithelium.

Question 37

What name is given to the area between the approximal (interproximal) surfaces of teeth where these peaks lie?

Answer 37

The embrasure 4

Question 38

In life, what lies coronal to the col?

Answer 38

The contact point between the teeth.

Question 39

What shape is its (col) junction with the lamina propria?

Answer 39

It is smooth centrally and irregular at the periphery due to the inflammatory reaction. 7.
Deep to the interdental gingival tissues are fibres of the periodontal ligament.

Question 40

what group of fibres do the interdental gingival fibres belong to

Answer 40

transeptal group

Question 41

what tissue lies deep to the transeptal fibres

Answer 41

Alveolar bone (crest).The main venous plexuses are in the apical region.