Which feature is specific to chronic periodontitis and not chronic gingivitis?

Chronic periodontitis is characterized by the presence of true periodontal pockets, which are the result of the destruction of the supporting structures of the teeth, including the bone. This destruction leads to a significant attachment loss and the formation of pockets that extend deeper than the gingival sulcus seen in gingivitis. In chronic gingivitis, inflammation is localized to the gums without any attachment loss or formation of true periodontal pockets. The probing depths in gingivitis may be shallow, with bleeding frequently occurring due to inflammation, but the soft tissue remains intact.

In contrast, the true pockets associated with chronic periodontitis indicate a more severe condition where there is a pathological loss of periodontal attachment, allowing for the depth of the sulcus to exceed 3mm, distinguishing it from non-periodontal diseases like gingivitis. The presence of subgingival calculus, which can overlap between both conditions, and gingival inflammation are not exclusive to chronic periodontitis, but rather can also occur in chronic gingivitis. Thus, the formation of a true pocket is a key feature that differentiates chronic periodontitis from chronic gingivitis.