Which of the following structures is NOT part of the periodontium?

The muscles of mastication are not part of the periodontium. The periodontium comprises the tissues that support and surround the teeth, specifically including the alveolar bone, cementum, and gingiva. These structures work together to anchor the teeth in the jaw and provide stability during functions like chewing.

Alveolar bone serves as the bony socket for the roots of the teeth, while cementum is the hard tissue covering the roots, helping to anchor the teeth to the bone via the periodontal ligament. The gingiva is the soft tissue surrounding the teeth, protecting the underlying structures and playing a vital role in maintaining oral health.

In contrast, the muscles of mastication are involved in the mechanics of chewing and jaw movement; they do not perform a supportive role within the structure of the periodontium. Thus, the identification of the muscles of mastication as not belonging to the periodontium highlights the distinction between supportive dental structures and the musculature associated with dental function.