The intermediate cementum layer is a distinct zone found in the root structure of a tooth. It is located between the dentin and the primary cementum.

To explain further:

- Dentin forms the bulk of the tooth structure beneath the enamel and cementum.
- Primary cementum, also known as acellular cementum, is the first layer of cementum deposited on the root dentin during tooth development.
- The intermediate cementum is a thin, less mineralized layer that acts as a transitional zone, exhibiting features that are somewhat similar to both dentin and cementum.
- This layer plays a crucial role in the attachment of the cementum to the underlying dentin and contributes to the overall integrity and function of the tooth root.

Therefore, the intermediate cementum layer is located between the dentin and the primary cementum.

Incorrect options:

- Option 1 (Enamel and dentin) is incorrect because intermediate cementum pertains to the root structure, whereas enamel covers the crown.
- Option 3 (Primary cementum and secondary cementum) is incorrect because these two layers overlay one another on the root surface but are not separated by intermediate cementum.
- Option 4 (Secondary cementum and alveolar bone) is incorrect as alveolar bone lies external to the periodontal ligament, not directly adjacent to any cementum layers.

Reference:
*Orban’s Oral Histology, 13th Edition, Chapter 6: Cementum and Periodontal Ligament / Page 85*