The presence of bacteria in a fractured tooth primarily affects which structure?

The presence of bacteria in a fractured tooth primarily affects the pulp. The pulp is the innermost part of the tooth, containing nerves and blood vessels that are essential for the health of the tooth. When a tooth is fractured, especially if the fracture penetrates through the enamel and dentin layers, it creates an opening that allows bacteria from the oral environment to enter. This invasion can lead to pulpitis, an inflammation of the pulp, and if untreated, can result in pulp necrosis or death of the pulp tissue.

In contrast, while cementum, enamel, and the periodontal ligament play important roles in dental health, they are less directly impacted by bacterial presence in the case of a fracture. Cementum is a hard tissue covering the root's surface and is primarily protective; enamel is the outer layer that protects against wear and decay; the periodontal ligament connects the tooth to the surrounding bone and helps with support. However, these structures do not house nerves or blood supply, making them less affected by bacterial invasion compared to the pulp.