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Oral Biology > The Anatomy & Physiology of the Periodontium > Flashcards

The Anatomy & Physiology of the Periodontium Flashcards

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1
Q

What are the 4 components of the Peridontium?

A

Cementum
Periodontal Ligament
Alveolar Bone
Gingiva

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2
Q

What are the type types of Histological sectioning that you will encounter?

A

Ground Sectioning
Decalcification
Cryomicrotomy

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3
Q

What is Ground section? give an example of a useful application to the process and a negative aspect.

A

Ground sectioning is used on non-decalicifed teeth. Useful for observing the hard tissue (enamel, dentin and cementum).

The teeth are literally ground down with a diamond saw/abrasive material.

The downside is that soft tissue is disrupted and can not be analysed.

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4
Q

What is decalcification? give an example of a useful application and a negative aspect.

A

Decalcification is the process of removing mineral from calcified tissue so that good quality paraffin sections can be prepared. It allows for the observation of soft tooth tissue such as the pulp and connective tissue.

Unfortunately you cannot see any of the calcified material (enamel etc).

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5
Q

What does the Periodontium do?

A

It supports the tooth in the jaw

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6
Q

Whats the cementum?

A

A pale yellow calcified tissue providing protective covering for the root surface to which the periodontal ligament fibres are secured.

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7
Q

What does the cementum adhere to?

A

It adheres to the roots dentine by a glue-like substance known as the hyaline layer.

It adheres to the periodontal ligament fibres. The embedded ends of the periodontal collagen fibres are called Sharpey’s fibres and are histologically different to the other collagen fibres.

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8
Q

How does the thinkness of the cementum vary along the tooth?

A

Cervically (the neck between the crown and root) it is only 10-15μm thick.

As you move apically (towards the apex) it is 50-200μm thick.

At the root apex it can be 600μm thick.

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9
Q

What is the risk to Cementum if a patient has gingivitis/periodontitis?

A

Apical migration of the attached gingiva can expose the cementum cervically causing it to be abrasively removed when brushing.

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10
Q

What are the two main types of Cementum?

A

Acellular (Primary) & Cellular (Secondary)

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11
Q

Whats the composition of Cementum?

A

65% inorganic hydroxyapatite, 23% organic collagen and 12% water

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12
Q

Does the Cementum have nerves?

A

No

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13
Q

What are the type types of Cementum?

A

Acellular (Primary) & Cellular (Secondary)

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14
Q

What are the main differences between Cementum subtypes and whats the significance of them both?

A

When the cementum 1st forms from the dental follicle it is acellular and covers the dental dentine.

Cellular cementum has a similar structure to bone with cementocytes embedded in a lacunae (small cavity) which have cytoplasmic processes linking each other via canaliculi (channels).

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15
Q

Is Cementum formation continuous throughout adulthood?

A

Yes. Cementum formation (cementogenesis) continues throughout life and is dependent upon the functional needs of the tooth and any tooth movement which may occur.

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16
Q

Can resorption of the cementum occur?

A

Yes. Resorption occurs in response to excessive occlusal stress or orthodontic loading.

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17
Q

Where is cellular cementum normally located?

A

It is located mainly in the apical area and intra-radicular areas of overlying acellular cementum.

It often covers apical 2/3 of the roots.

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18
Q

How is the Cementum attached to the Periodontal Ligament?

A

Collagen fibres in the periodontal ligament run into the organic matrix of the precementum. This precementum is unmineralised and thin; can also be called cementoid on Acellular extrinsic fibre cementum (AEFC).

When the precementum becomes mineralised it leads to the fibres being incorporated. Once this happens they are known as Sharpey’s fibres.

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19
Q

The is the Periodontal Ligament?

A

The periodontal ligament is a dense connection tissue layer enveloping the roots of teeth; occupying the space between the root (and cementum) and alveolar bone.

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20
Q

What are the 4 key functions of periodontal ligaments?

A
  1. Provision of the tissue attachment between the tooth and alveolar bone. This is responsible for tooth support and protection.
  2. Responsible for the mechanism by which the tooth attains and maintains its function position.
  3. Maintenance and repair of the cementum and alveolar bone.
  4. Neurological control of mastication by its mechanoreceptors.
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21
Q

What is the Periodontal ligament composed of?

A
  1. Fibres: Collagen (desmodontium) & Oxytalan
  2. Ground Substance
  3. Cells: Fibroblasts, cementoblasts, osteoblasts, osteoclasts, cementoclasts, epithelial cells
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22
Q

Which type of collagen is the most abundant in periodontal ligaments?

A

70% of the collagen is type I fibrils & 20% is type II. There are traces of IV and VII with the rests of malassez and blood vessels.

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23
Q

What are the Rests of Malassez and what are their relevance to the periodontium?

A

Their origin is with the Hertwig’s root sheath. This is a layer of epithelial cells formed from the downward growth of the inner and outer enamel epithelium of the developing tooth germ.

The Hertwig’s root sheat maps out the shape of the root. It atrophies once the root is formed and any residual cells are known as the rest cells of Malassez. They are found near the cementum of most teeth, around the apical and cervical area.

Believe that it might:

  • maintain periodontal ligament homeostasis to prevent ankylosis (fusion of cementum or dentin to the alveolar bone)
  • potentially harbour epithelial stem-cell populations that have similar properties to mmesenchymal stromal/stem cells (aid periodontal regeneration)
24
Q

How is a large proportion of collagen arranged?

A

It is gathered into bundles known are the PRINCIPLE FIBRES; these are around 5μm in diameter.

25
Q

What are Principle fibres?

A

Bundles of collagen fibrils. They are more numerous but smaller at their attachment with Cementum in comparison to alveolar bone.

They unravel into smaller fibres which join up with those of adjacent fibres to produce a meshwork of interconnected fibres oriented between bone and cementum.

26
Q

A principle fibre is made of?

A

Collagen fibril subunits. 3 fibrils are wound together to make a collagen fibre.

27
Q

Principle fibres (Dentoalveolar fibre group) have multiple orientations, what are they?

A
  1. Dentoaveolar crest fibres (fibres from the roots to alveolar bone proper
  2. Horizontal fibres ( Mid-root to adjacent alveolar bone proper)
  3. Oblique fibres (apical one thrid of root to adjacent alveolar bone proper)
  4. Apical fibres (apex of the root to alveolar bone proper)
  5. Interradicular fibres (vertical inbetween the roots)
28
Q

The Gingival fibre group has multiple orientations, what are they?

A
  1. Dentogingival fibres: Insert into the supracrestal root cementum and fan out into the adjacent connective tissue.
  2. Dentoperiosteal fibres: insert into the supracrestal root cementum and blend with the periosteal covering of the adjacent alveolar process.
  3. Alveologingival fibres: insert into the alveolar crest ad fan out into the adjacent gingival connective tissue.
  4. Circumferential fibres: Follow a circular course around individual dental units.
  5. Semicircular fibres insert into the approximal surfaces of a tooth and follow a semicircular course to insert on the opposite side of the same tooth.
  6. Transgingival fibres: insert into the approximal surface of a tooth and fan out towards the oral or vestibular surface.
  7. Intergingival fibres: course along the oral or vestibular surfaces of the dental arch
  8. Transseptal fibres: course from one approximal tooth surface to the approximal surface of the adjacent tooth
29
Q

What is Col?

A

A valley like depression which connects the gingival papillae situated in the interproximal space between the two teeth. It lies below, and conforms to the shape of the interproximal contact between teeth.

30
Q

Do tooth related and bone related collagen fibres meet?

A

They intercalate in an intermediate pluxus in the middle (plexus = a network)

31
Q

Is collagen more numerous at the cemental or bone attachment?

A

Cemental

32
Q

Is there a fast turnover of collagen in the Periodontal ligament?

A

Yes

33
Q

Whats Oxytalan?

A

Oxytalan is immature elastin fibres (pre-elastin) which are bound to the cementum and leave parallel and oblique to the root surface. Their function is to maintain the patency (open/unobstructed) of blood vessels during occlusal loading.

34
Q

What is ground Substance?

A

It is a complex biochemical matrix which is secreted by fibroblasts which surround the collagen fibres, oxytalan and the other cells of the periodontal ligament.

35
Q

What is the composition of the ground substance?

A

Hyaluronate glycosaminoglycans, Proteoglycans (Proteodermatan sulphate & PG1), Glycoproteins (Fibronectin & Tenascin)

36
Q

What cells are present in the Periodontal Ligament?

A
  1. Fibroblasts
  2. Cementoblasts
  3. Osteoblasts
  4. Osteoclasts & Cementoclasts
  5. Epithelial cells
  6. Immune cells
37
Q

What are the roles and features of Fibroblasts?

A
  1. They are responsible for the regeneration of the peridontal ligament and aid in adaptive responses to mechanical loading.
    1b. They degrade collagen (collagenase) (technically they are fibroclastic)
    1c. Secretion of matrix metalloproteinases (degrade matrix in periodontitis)
  2. They have many cytoplasmic processes indicating they are very active, they have a low nuclear/cytoplasmic ratio (small nucleus, indicates mature cells) & they are protein synthesizing organelles
38
Q

What are the role and feature of Cementoblasts?

A

They line the surface of the cementum. Their function is cementogenesis which is the formation of new cementum.

They resemble osteoclasts but differ functionally and histologically. When they become trapped in the cementum they are known as Cementocytes.

39
Q

What are the roles and features of Osteoblasts?

A

Osteoblasts line the tooth socket and resemble Cementoblasts. They are prominent when there is active bone formation as they secrete: collagen and specialised proteins such as osteocalcin and osteopontin. Furthermore they produce hydroylapatite

40
Q

Whats the relation between Epithelial cells in and cysts?

A

Epithelial cell stimulated in the Rest of Malassez causes cellular proliferation/division. the centre of the growing masses is void of oxygen so the cells die. Changes in water concentration and an increasing mass causes a cyst to form.

41
Q

What the roles and features of immune cells?

A

There are 3 prominent immune cells in the Periodontal ligament:

  1. Macrophages: 4% of cell population and are derivates of monocytes and phagocytosis. They are attacking organisms which increase the immune response in the area.
  2. Mast Cells: These cells degranulate when stimulated. Secreting histamine, heparin and anaphylactic factors. Causes inflammation, blood thinning and edema.
  3. Eosinophils: White blood cell associated with allergies
42
Q

Detail some features of the Blood Supply to the Periodontal Ligament.

A

There is the superior and inferior alveolar arteries and these are perforating the alveolar bone.

Major vessels are intertwined between the principle fibres with a capillary plexus around the teeth.

43
Q

Is there a nerve supply in the periodontal ligament?

A

There are sensory nerve fibres with both nociception and mechanoreception. They detect pain and mechanical load.

44
Q

What is Alveolar bone?

A

Alveolar bone is part of the jaw that supports and protects teeth.

45
Q

What is the composition of the Alveolar bone?

A

The bone is composed of 60% inorganic material (calcium hydroxyapatite and mainly carbonated hydroxyapatite in the form of needle like crystallites or thin plates.

25% organic material.

Type I Collagen forms 90% of the extracellular matrix, there are also some proteoglycans (may regulate collagen fbril diameter and mineralisation) and glycoproteins (osteonectin which canbind calcium; making it involved in mineralisation + synthesised by osteoblasts).

15% is water

46
Q

What are the bone cells?

A

Osteoblasts: secrete organic extracellular matrix of now bone osteoid which undergoes rapid mineralisation to form bone. When they become trapped they are known as Osteocytes.

Osteoclasts: Multinuclear cells involved in bone remodelling

Osteoprogenitor cells: Stem cells beneath the osteoblast layer.

47
Q

What are the two main forms of bone? forms of bone

A

Woven: Immature bone with random organisation of its collagen

Lamellar: Composed of successive layers (Lamellae). It can either be formed as a solid mass (COMPACT BONE) or in an open sponge-like manner (CANCELLOUS BONE)

48
Q

What is compact bone?

A

Is is made of parallel bone collumns which are disposed parallel to the long axis of the long bone. They are made of concentric (rings) bony layers (lamellae) arranged around a central channel with blood vessels, lymphatics and nerves (Haversain canals)

49
Q

How do the osteocyte communicate to one-another?

A

The Haversain canals with their lamella form the haversain systems (osteon). Neurovascular bundles interact with each other via Volkmann’s canals that pierce the columns at right angles. Osteocytes in their lacunar communcate via the central canals cytoplasmic extensions called canaliculi.

50
Q

What is the relationship between compact bone and cortical bone?

A

The outermost layer of compact bone gives way to dense cortical bone in the centre. The compact bone acts as weight bearing pillars and are able to withstand high levels of mechanical stress.

The innermost aspect of the compact bone, the lamellae erge with spongy bone.

51
Q

What is Cancellous bone?

A

Aka Spongy bone

It is made of a network of bone trabiculae seperated by interconnected spaces containing BONE MARROW.

Trabiculae are thin and composed of irregular bone lamellae. They dont contain haversain canals. The spongy nature is due to the marrow spaces, giving the bone flexibility.

52
Q

Alveolar bone features

A
  1. Out and inner parellel alveolar plates
  2. Sockets are separated by interdental septa
  3. Roots are separated by interradicular septa
53
Q

How does bone remodelling change over time?

A

During childhood, bone deposition exceeds resorption.

Equilibrium between deposition and resorption occurs n adult life.

Resorption exceeds deposition in old age which leads to osteoporosis.

54
Q

What is the role of Osteoblasts in bone remodelling?

A

Osteoblasts can stimulate the production of osteoclasts by cytokine and growth factor release.

Osteoblasts can produce osteoidase’s which will expose the bone for osteoclast re-sorption.

55
Q

What are the hallmarks of bone remodelling?

A

Reversal lines make the change in bone activity; its a dynamic process as the bone is adapting to pressure.

25% of spongy bone mass is remodelled and 3% of compact bone every year.

56
Q

The Gingiva: What is the interdental Papilla?

A

The interdental gingiva occupying the area between adjacent teeth. Its size and shape depends ont he shape and contact between the teeth.

Wedge shaped appearance on the buccal and lingual sides whilst pointed between anterior teeth.

Oral Biology (33 decks)

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