**Core Concept**
When periodontal pocket is probed and granulation tissue is removed, the underlying hard structure can be visualized. This structure is crucial in maintaining the attachment between the tooth and the surrounding alveolar bone. The presence or absence of this structure can indicate the extent of periodontal disease progression.

**Why the Correct Answer is Right**
Transseptal fibers are a type of periodontal ligament fiber that runs between the teeth, attaching them to the alveolar bone. After removal of granulation tissue from the periodontal pocket, the transseptal fibers can be observed as a hard, fibrous structure. This is because transseptal fibers are located deeper within the periodontal ligament and are not affected by the inflammation and granulation tissue formation in the periodontal pocket. They play a crucial role in maintaining the integrity of the tooth and alveolar bone interface.

**Why Each Wrong Option is Incorrect**
**Option A:** Periosteum is a layer of connective tissue that covers the bone and is involved in bone repair and regeneration. It is not a hard structure seen after removal of granulation tissue from the periodontal pocket.

**Option C:** Sharpey's fibers are remnants of the periodontal ligament fibers that have inserted into the bone. They can be seen on the surface of the bone, but are not the hard structure seen after removal of granulation tissue from the periodontal pocket.

**Option D:** Organized granulation tissue is the type of tissue seen in the periodontal pocket, characterized by an abundance of fibroblasts, collagen, and other inflammatory cells. It is not a hard structure and is not seen after removal of granulation tissue.

**Clinical Pearl / High-Yield Fact**
In periodontal disease, the loss of transseptal fibers can lead to tooth mobility and eventual tooth loss. Therefore, preserving and maintaining the integrity of the transseptal fibers is crucial in the management of periodontal disease.

**✓ Correct Answer: B. Transseptal fibres**