Periodontal Ligament (PDL) Fibers

Periodontal Fibers

• There are five groups of principal fibers of the PDL.
• Inter-radicular fibers prevent tooth tipping, resist luxation, and protect the blood, lymph, and nerve supply of the tooth.

Development of Principal Fibers of PDL

• Small, fine brush-like fibrils are detected arising from the root cementum and projecting into the PDL space.
• Small fibers are seen on the surface of the bone but only in thin, small numbers.
• The number and thickness of fibers originating from the bone increase and elongate, radiating towards the loose connective tissue in the mid portion of the periodontal ligament.
• The fibers originating from the cementum also increase in length and thickness and fuse with the fibers originating from the alveolar bone in the periodontal ligament space.
• Following tooth eruption, the principal fibers become organized in bundles and run continuously from bone to cementum.

Connective Tissue

• The periodontal ligament is supplied by branches derived from three sources: dental, inter-radicular, and interdental arteries.
• Lymphatic vessels follow the path of blood vessels in the periodontal ligament.
• The periodontal ligament is mainly supplied by dental branches of the alveolar nerve.
• The periodontal ligament has mechanoreceptors providing sense of touch, pressure, pain, and proprioception during mastication.

Functions of the PDL

• Physical functions:
  • Provide soft tissue “casing” to protect the vessels and nerves from injury by mechanical forces.
  • Transmit occlusal forces to the bone.
  • Attach the teeth to the bone.
  • Maintain the gingival tissues in their proper relationship to the teeth.
  • Resist the impact of occlusal forces (shock absorption).
• Formative and remodeling functions:
  • Cells of the periodontal ligament have the capacity to control the synthesis and resorption of the cementum, ligament, and alveolar bone.
  • Periodontal ligament undergoes constant remodeling; old cells and fibers are broken down and replaced by new ones.
• Nutritive and sensory functions:
  • Since PDL has a rich vascular supply, it provides nutrition to the cementum, bone, and gingiva.
  • The PDL is supplied with sensory nerve fibers which transmit the sensation of touch, pressure, and pain to higher centers.

Clinical Consideration

• The width of PDL space varies with age, location of the tooth, and degree of stress to which the tooth was subjected.
• The width of PDL space is about 0.25mm in normal functions.
• It is widest at the cervical and apical portions of the root and narrowest at the middle.
• The PDL has adaptability to rapidly changing applied force and its capacity to maintain its width at constant dimensions throughout its lifetime.