When periodontal disease advances, which of the following is commonly observed?

As periodontal disease progresses, one of the hallmark characteristics is the increase in probing depths. This occurs because the disease leads to inflammation and destruction of the supportive structures around the teeth, including the periodontal ligament and alveolar bone. Consequently, the attachment of the gums to the tooth surface deteriorates, causing the sulcus or pocket around the tooth to deepen.

This change in probing depths is an essential indicator for clinicians, as it reflects the severity of the periodontal condition and assists in diagnosing the extent of the disease. An increase in probing depth is often accompanied by clinical signs of disease, such as swelling, bleeding on probing, and possibly mobility of the teeth, making it a vital aspect of periodontal assessments.

The other options either describe static conditions or improvements that are not typically seen in advanced periodontal disease. For instance, no change in attachment levels would suggest a stable condition, which is generally not the case as the disease progresses, while decreased sensitivity to pain may occur in some cases due to compromised nerve endings or severe tissue damage. Lastly, a reduction in plaque biofilm is contrary to what is expected since periodontal disease often leads to increased accumulation of biofilm and other contributing factors.