Periodontal Ligament (PDL) Fibers

Study Notes

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.

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.

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.

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.

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.