Periodontal Ligament

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Questions and Answers

What is the primary function of the periodontal ligament?

To provide sensory perception of the tooth

To connect the tooth root to the surrounding bone (correct)

To secrete enamel for tooth protection

To produce saliva for digestion

How does the periodontal ligament develop during tooth formation?

From the embryonic dental sac (correct)

From the dental pulp tissue

From the connective tissue of the gingiva

From the outer enamel layer

Which structure merges with the periodontal ligament at the root apex?

Dental pulp (correct)

Gingiva

Alveolar bone

Cementum

What type of tissue primarily composes the periodontal ligament?

Connective tissue Signup and view all the answers

What is the significance of the principal fibres in the periodontal ligament?

They connect the tooth to the alveolar bone and help absorb forces during chewing Signup and view all the answers

What is the primary function of principal fibres in the periodontal ligament?

To distribute forces of mastication and speech Signup and view all the answers

Which arteries contribute significantly to the blood supply of the periodontal ligament?

Superior and inferior alveolar arteries Signup and view all the answers

What type of fibres primarily compose the periodontal ligament?

Collagen fibres Signup and view all the answers

What role do the epithelial rests of Malassez play in the periodontal ligament?

Acting as progenitor cells for tissue regeneration Signup and view all the answers

What is the significance of Sharpey's fibres in the periodontal ligament?

They connect the periodontal ligament to the tooth root and alveolar bone Signup and view all the answers

Which type of nerve supply is NOT associated with the periodontal ligament?

Motor nerves Signup and view all the answers

In which area is the periodontal ligament typically wider?

Near the apex and cervical margin Signup and view all the answers

Which structure provides the principal blood supply that anastomoses freely within the periodontal ligament?

Penetrating vessels from alveolar bone Signup and view all the answers

What is the primary function of the alveolar crest group fibres?

Prevent extrusion of the tooth from the socket Signup and view all the answers

Where do the horizontal group fibres primarily insert?

Into the bone apical to the alveolar crest Signup and view all the answers

What significant masticatory forces do the oblique group fibres primarily resist?

Vertical masticatory forces Signup and view all the answers

What is a key characteristic of apical group fibres concerning root development?

They are absent in incompletely formed roots Signup and view all the answers

The interradicular group fibres are significant because they:

Resist vertical and lateral movements of multi-rooted teeth Signup and view all the answers

What are interdental ligaments primarily responsible for?

Maintaining the alignment of adjacent teeth Signup and view all the answers

What changes occur in the periodontal ligament (PDL) with age?

Narrowing of the PDL width Signup and view all the answers

Which group of fibres resists rotational forces and helps in maintaining teeth alignment?

Interdental or transseptal fibres Signup and view all the answers

What is a significant clinical consideration regarding the periodontal ligament?

Loss of fibres can lead to periodontal disease. Signup and view all the answers

Which component contributes significantly to the cushioning effect of the periodontal ligament?

Water content Signup and view all the answers

Which group of fibres is found limited to the coronal portion of the periodontal ligament?

Horizontal group Signup and view all the answers

What is the major function of gingival fibre groups?

Connect adjacent teeth and maintain alignment Signup and view all the answers

The primary location of the oblique group fibres is:

Two-thirds the length of the periodontal ligament Signup and view all the answers

Study Notes

Histology of the Periodontal Ligament

The periodontal ligament (PDL) is connective tissue surrounding the tooth root, connecting it to the bone.
It's continuous with the gingiva and communicates with bone marrow through vascular channels.
At the root apex, the PDL merges with the dental pulp.

Intended Learning Outcomes

Define the periodontal ligament and its functions.
Explain periodontal ligament development and its role in tooth development.
Discuss the cellular and extracellular components of the PDL.
Explain the nerve and blood supply to the PDL.
Discuss the location, origin, insertion, and significance of principal fibres in the PDL.

What is the Periodontal Ligament?

The PDL is the connective tissue surrounding the tooth root, connecting it to the bone
It's continuous with the connective tissue of the gingiva and communicates with the marrow spaces through vascular channels in the bone.
At the root apex, the PDL merges with the dental pulp.

Functions of Periodontal Ligament

Sensory: The PDL detects pressure, pain, and touch.
Nutritive: The PDL provides nutrients to the tooth.
Physical: The PDL helps resist forces of mastication, preventing tooth movement and damage.
Formative & Remodelling/ Resorptive (i.e., adaptation): The PDL helps in shaping and adapting to changing demands.

Width of PDL in Different Loading Conditions

The width of the PDL varies depending on the loading conditions.
Heavy loaded: 0.35mm (near crest), 0.28mm (middle), 0.30mm (near fundus).
Normally loaded: 0.14mm (near crest), 0.10mm (middle), 0.12mm (near fundus).
Functionless: 0.10mm (near crest), 0.06mm (middle), 0.06mm (near fundus).

PDL on a Radiograph

The radiograph shows the PDL as a periodontal space (radiolucent).
This space is between the lamina dura and the cementum.
The width of the space is narrower in permanent teeth than in deciduous (baby) teeth.

Development of PDL

The PDL forms from the dental follicle shortly after root development begins.
Fibroblasts in the follicle become active and produce fibres that gradually become oblique and attach to the tooth, cementum, and bone.
As the tooth erupts, more fibres develop and attach to new cementum and bone.

Structural Elements of PDL

Cells: Resorptive, Synthetic, Progenitor, Defence
Extracellular Substance: Ground substance, Fibres

Blood Supply to Periodontal Ligament

The principal blood supply comes from superior and inferior alveolar arteries.
Vessels from the alveolar bone, apical vessels, and anastomosing vessels from the gingiva also contribute.
Vessels freely anastomose within the ligament and occupy the interstitial spaces.

Nerve Supply to Periodontal Ligament

The PDL contains sensory and autonomic nerves.
Sensory nerves detect pressure, pain, and touch.
Autonomic nerves are thought to regulate blood flow.
Branches of the trigeminal nerve (cranial nerve V) supply sensation and movement to the area.

Fibres of Periodontal Ligament

PDL fibres are made from collagen.
They are organized into groups based on orientation and function (resembling spliced ropes).
Principal fibres are embedded in cementum and bone, called Sharpey's fibres.

Principal Fibre Groups

Alveolar crest: Located just beneath the junctional epithelium, preventing tooth extrusion.
Horizontal: Runs parallel to alveolar crest fibres, resisting horizontal forces.
Oblique: Located at an angle to tooth axis (from apex toward the cervical region) resisting masticatory forces.
Apical: Runs from the tooth apex and is inserted into the socket, resisting vertical, luxative, and twisting forces, while protecting delicate nerves and vessels.
Interradicular (transseptal): Runs through the gingival mucosa to connect neighbouring teeth, resisting rotational forces.

Gingival Fibre Group

Separate set of fibres found within the lamina propria of marginal gingiva.
This group is associated with the gingiva proper (gingival tissue).

Ground Substance

Ground substance consists of collagen fibres and water (approximately 70%).
It functions in exchanging metabolites, binding ions and water, orientating fibres, and aiding in tooth support and binding mechanisms.
Tissue fluid pressure is important, and it's around 10 mm Hg above atmospheric pressure.

Age Changes

Age-related changes in the PDL include a decrease in cells, increased fibrous tissue, reduced vascularity, and narrowing of the periodontal space (with occasional scalloping of tissues).

Clinical Considerations

Clinicians should consider the age-related changes, effects of different loading conditions, blood and nerve supply, and the function of all the fibres during patient evaluations.

Further Learning

Review diagrams and illustrations for clarity.
Further research into specific terms (e.g., fibroblasts, vascularity) could reinforce learning.
Refer to any relevant textbook materials for additional details and clarity.

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