The periodontal ligament (PDL) is a specialized connective tissue that connects the tooth to the alveolar bone, providing support and shock absorption during mastication. The thickness of the PDL is an important anatomical consideration because it reflects the functional state of the periodontium.

The typical range of thickness for the PDL is between 0.15 to 0.38 mm. This size allows for adequate cushioning and sensory feedback while maintaining the structural integrity necessary to anchor the tooth securely. The thickness can vary slightly depending on factors such as the stage of tooth development, occlusal forces, and age, but typically remains within this range in healthy adults.

The other options provided are either too thin to accommodate the necessary fiber bundles or too thick, which is not consistent with normal anatomical findings.

Key Points:
- The PDL thickness typically ranges from 0.15 to 0.38 mm.
- It serves as a shock absorber and stabilizer between the tooth and bone.
- Thickness can vary slightly but remains within this range in healthy individuals.

Reference: Orban’s Oral Histology, 14th Edition, Volume 1, Chapter 9, Page 130