The Periodontium: Periodontal Ligament

Review: What structures compose the periodontium?

Gingiva, PDL, Cementum, Bone

What structure occupies the space between the root surface and alveolar bone?

Periodontal ligament

What is the radiological presentation of the PDL?

Thin, dark (radiolucent) line between alveolus and root

What is the thickness of the PDL?

0.1 - 0.25 mm

What comprises the PDL?

• CT fibers

• Cells

• Vasculature

• Nerves

• Ground substance

What are the functions of the PDL?

• Formative

• Supportive

• Nutritive

• Sensory

• Protective

What specific cells compose the PDL?

• Undifferentiated mesenchymal cells

• Fibroblasts

• Osteoblasts

• Cementoblasts

• Odontoclasts

• Epithelial cells

• Immune cells

What are remnants of Hertwig’s epithelial root sheath (islands of squamous epithelium near root surface)?

Epithelial Rests of Malassez

What is labeled CB?

Cementoblasts

What is labeled M?

Rests of Malassez

What is labeled BV?

Blood vessels

What is the supportive function of the PDL?

Anchor tooth to bone

What is the nutritive function of the PDL?

Contains blood supply and lymphatics

What region is labeled 1?

Periodontal ligament branch

What region is labeled 2?

Interradicular

What region is labeled 3?

Periosteal

What are the three types of vessels of the PDL?

• Alveolar artery branches

• Interradicular arteries

• Gingival vessels

What is the structure labeled 1?

Periodontal membrane branch

What is the structure labeled 2?

Interdental septal arteriole

What is the structure labeled 3?

Dental arteriole

What is the structure labeled 4?

Inferior alveolar artery

What is the sensory function of the PDL?

Transmitting tactile pressure and pain sensations

What is the protective function of the PDL?

Cushions occlusal forces

(T/F) The PDL is static tissue, restricting all movement.

False. It is dynamic, allowing the tooth to move and adapt to functional states.

How are PDL fiber groups identified?

Location and orientation (direction)

What are the different PDL fiber groups?

• Alveolar crest group

• Horizontal group

• Oblique group

• Apical group

• Interradicular group

What are the fibers labeled 1?

Alveolar crest

What are the fibers labeled 2?

Horizontal

What are the fibers labeled 3?

Oblique

What are the fibers labeled 4?

Apical

What are the fibers labeled 5?

Interradicular

Which PDL fiber group is only found on teeth with furcated roots?

Interradicular

What are the mineralized ends of principal collagen fibers embedded in cementum and bone?

Sharpey’s Fibers

Where would you find the largest amount of Sharpey’s Fibers?

Cemental surface

Just a diagram that might be helpful to know. She really likes it.

[ FLIP CARD ]

What is the mineralized CT that covers the roots?

Cementum

What is the main function of the cementum?

Anchor PDL fibers to the tooth