**Core Concept**
Periodontitis is a chronic inflammatory disease affecting the periodontal tissues, including the periodontal ligament, cementum, and alveolar bone. The disease process involves the destruction of these tissues, leading to tooth loss if left untreated.

**Why the Correct Answer is Right**
The disease process in periodontitis begins with the accumulation of dental plaque and the subsequent activation of the host immune response. The first fibers to be affected are the **bundle bone fibers**, which are the thickest and most numerous fibers in the periodontal ligament. These fibers are attached to the surface of the alveolar bone and are in close proximity to the gingival crevice, making them susceptible to destruction by inflammatory mediators and bacterial toxins. The destruction of these fibers leads to the loss of attachment and the progression of periodontal disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the **dental lamina** is not directly involved in the disease process of periodontitis. It is a remnant of the embryonic dental lamina and is not a component of the periodontal ligament.

**Option B:** This option is incorrect because the **Sharpey's fibers** are actually a type of bone fiber that is involved in the attachment of the periodontal ligament to the alveolar bone. However, they are not the first fibers to be destroyed in periodontitis.

**Option C:** This option is incorrect because the **cementum** is a hard, calcified substance covering the root surface of the tooth. While it is affected by periodontitis, it is not the first fibers to be destroyed in the disease process.

**Clinical Pearl / High-Yield Fact**
The destruction of the bundle bone fibers in periodontitis is often accompanied by the loss of the periodontal ligament space, which can be visualized on radiographs as a widening of the periodontal ligament space.

**Correct Answer: C. Cementum**