Which of the following is NOT a characteristic of gingivitis?

The characteristic that does not align with gingivitis is the presence of hard tooth calculus. Gingivitis is primarily an inflammation of the gum tissues caused by the accumulation of plaque, leading to symptoms such as redness of the gums, swelling, and sometimes discomfort or mild pain. In contrast, hard tooth calculus refers to mineralized plaque that has hardened on the teeth, which typically occurs in more advanced stages of periodontal disease and is not a direct symptom of gingivitis.

The other options, including redness of the gums, swollen gums, and potential pain during chewing, are all common signs that indicate the presence of gingivitis. Redness and swelling occur due to inflammation, which is a key feature of the condition. Pain during chewing may also arise as a result of inflamed and sensitive gum tissues during the early stages of gum disease. Therefore, recognizing that hard tooth calculus is associated with more advanced periodontal issues, rather than gingivitis itself, highlights why it is the characteristic that does not apply.