Cells of PDL | Periodontal ligament | Dental Lectures

Summary

This video provides an in-depth explanation of the cells found in the periodontal ligament (PDL). It covers five main cell types: synthetic cells (fibroblasts, osteoblasts, cementoblasts), resorptive cells (osteoclasts, cemento clasts), progenitor cells, resting cells (rests of Malassez), and defense cells (mast cells, macrophages, eosinophils). The video highlights the roles of these cells in maintaining, remodeling, and defending the periodontal ligament, and discusses their morphology, function, and significance in dental health. The detailed exploration also includes cellular interactions, structural properties, and their contribution to tooth eruption and repair.

Takeaways

• 😀 Synthetic cells in the periodontal ligament (PDL) include fibroblasts, osteoblasts, and cementoblasts, which are responsible for forming collagen fibers, bone, and cementum, respectively.
• 😀 Fibroblasts are the most predominant cells in the PDL and are responsible for the formation and resorption of collagen fibers, which helps in tooth eruption.
• 😀 Osteoblasts, found on the bone surface of the PDL, are involved in bone formation, remodeling, and mineralization of osteoid proteins.
• 😀 Cementoblasts, located on the cementum, are responsible for forming cementum and anchoring the tooth to the bone.
• 😀 Resorptive cells include osteoclasts (for bone resorption) and cemento clasts (for cementum resorption), both of which play key roles in maintaining tooth integrity.
• 😀 Progenitor cells in the PDL have the ability to divide and replace dying cells, aiding in tissue repair, especially near blood vessels.
• 😀 Resting cells, known as epithelial cell rests of Malassez, are remnants from Hertwig's epithelial root sheath and can proliferate to form cysts or tumors under certain conditions.
• 😀 Defense cells in the PDL include mast cells, macrophages, and eosinophils, which help with inflammation and immune response by releasing histamines and performing phagocytosis.
• 😀 Fibroblasts exhibit contractile properties due to actin filaments, which allow them to generate forces and facilitate tooth movement during eruption.
• 😀 The PDL plays an essential role in periodontal ligament remodeling and maintaining tooth position through cellular interactions and extracellular matrix formation.

Q & A

What are the five main types of cells found in the periodontal ligament (PDL)?

The five types of cells in the periodontal ligament are synthetic cells, resorptive cells, progenitor cells, epithelial cell rests of Malassez, and defense cells.

What are the main functions of synthetic cells in the PDL?

Synthetic cells form different structural components. Fibroblasts form collagen fibers, osteoblasts form bone, and cementoblasts form cementum. These cells are responsible for protein synthesis, tissue formation, and maintenance of the PDL.

How do fibroblasts contribute to both the formation and degradation of collagen fibers in the PDL?

Fibroblasts form collagen fibers during tissue synthesis and also secrete enzymes that degrade old or damaged collagen, enabling continuous remodeling of the periodontal ligament.

What special features make PDL fibroblasts different from gingival fibroblasts?

PDL fibroblasts originate from ectomesenchyme, have higher proliferative capacity, express high alkaline phosphatase and cyclic AMP levels, and contain actin microfilaments and fibronectin, which allow them to generate contractile forces aiding in tooth eruption.

What are the distinguishing structural characteristics of osteoblasts and cementoblasts?

Osteoblasts are cuboidal-shaped cells with a prominent basal nucleus and abundant organelles, responsible for bone formation and mineralization. Cementoblasts are also cuboidal but have fewer rough endoplasmic reticula and are mainly involved in cementum formation and tooth attachment.

What are resorptive cells, and what roles do they play in the PDL?

Resorptive cells are responsible for breaking down tissues. Fibroblasts resorb collagen fibers, osteoclasts resorb bone, and cementoclasts resorb cementum, allowing for continuous remodeling of the periodontal structures.

Where are progenitor cells located in the PDL, and what is their function?

Progenitor cells are mainly located adjacent to blood vessels. They have stem cell-like properties, can divide and replace dying cells, and migrate to repair sites to generate new cells during tissue repair and regeneration.

What are epithelial cell rests of Malassez, and what is their significance?

Epithelial cell rests of Malassez are remnants of Hertwig’s epithelial root sheath found in the PDL, usually near cementum. Though normally inactive, they can proliferate to form cysts or calcified bodies known as cementicles.

What are the main types and functions of defense cells found in the PDL?

The defense cells include mast cells, macrophages, and eosinophils. Mast cells release histamine to influence vascular and immune responses, macrophages perform phagocytosis and secrete growth factors, and eosinophils help in immune defense and debris clearance.

How do fibroblasts in the PDL contribute to tooth eruption according to the periodontal ligament traction theory?

Fibroblasts have actin filaments that contract in response to signals from the extracellular matrix. Their cytoplasmic processes wrap around collagen fibers and pull them during contraction, generating forces that help move the tooth, supporting the traction theory of eruption.

What happens to the epithelial cell rests of Malassez with age?

These cells are more numerous in children but decrease with age. Their distribution also changes, becoming more cervical in location near the gingiva as individuals grow older.