Which of the following is a common sign of periodontal disease?

Bleeding gums and tooth mobility are indeed common signs of periodontal disease. Periodontal disease, which includes gingivitis and periodontitis, is characterized by the inflammation of the gums and the supporting structures of the teeth. As the condition progresses, it leads to the breakdown of the gum tissue and bone that support the teeth, resulting in these specific signs.

When periodontal disease is present, the body's immune response to the bacteria in plaque leads to inflammation, which can cause the gums to bleed during brushing or flossing. In addition, the loss of bone and attachment due to the disease can result in the teeth feeling loosened or mobile. Recognizing these signs early can be crucial for effective management and treatment to prevent further progression of the disease.

The other options, while they may indicate different dental issues, do not specifically align with the hallmark signs of periodontal disease. Pain while chewing and sensitivity to hot and cold are more commonly associated with dental caries or pulpitis, and discoloration of the tooth surface could be due to a variety of factors, such as staining, but does not directly indicate periodontal disease. Thus, bleeding gums and tooth mobility are key indicators that suggest the presence of periodontal issues.