A patient has had a draining sinus tract associated with a non-vital tooth for more than TWO YEARS. Which inflammatory cell predominates in the lesion?

Correct answer: D. Lymphocytes

• A. BASOPHILS mediate immediate hypersensitivity through histamine release and play no role here.
• B. NEUTROPHILS dominate ACUTE inflammation and form the purulent exudate of an acute abscess. They are present in the tract lumen but are not the predominant cell of a two-year-old lesion.
• C. EOSINOPHILS are recruited in parasitic infections and type I allergic reactions, not in chronic bacterial periapical disease.
• D. CORRECT. Duration determines the cell population. A lesion present for more than two years is by definition CHRONIC, and chronic inflammation is dominated by MONONUCLEAR cells — LYMPHOCYTES, plasma cells and macrophages. This is the histological picture of a chronic apical abscess or periapical granuloma: a lymphoplasmacytic infiltrate in granulation tissue, with the sinus tract acting as a decompression pathway that prevents pressure building and keeps the lesion asymptomatic.

Note: ⚠️ Read the TIME CUE carefully — the series contains the ACUTE counterpart of this item, where a newly draining fistula is correctly keyed to NEUTROPHILS. Same anatomy, opposite answer. Acute = neutrophils; chronic = lymphocytes, plasma cells and macrophages. Note also that the presence of a sinus tract does not change the treatment: the tooth needs root canal treatment or extraction, and the tract resolves once the source is removed.