Periapical infection from a necrotic primary molar spreads toward the developing permanent successor. What is the most likely consequence for the permanent tooth?

Correct answer: B. Disruption of the ameloblastic layer causing enamel hypoplasia or hypomineralisation

• A. Eruption may be accelerated OR delayed depending on the timing of the infection, but the enamel defect is the defining and examinable consequence.
• B. CORRECT. The developing crown sits directly beneath the furcation of the primary molar, so inflammatory exudate reaches the follicle readily. AMELOBLASTS are exquisitely sensitive to inflammation and to the associated pH change. Damage during the secretory stage produces enamel HYPOPLASIA (deficient quantity — pits and grooves); damage during maturation produces HYPOMINERALISATION (deficient quality — opaque or discoloured enamel). The classic result is a TURNER TOOTH.
• C. Root formation may occasionally be disturbed, but the crown is forming at the age when primary molar infections occur, so enamel is the tissue at risk.
• D. Apical closure is governed by Hertwig epithelial root sheath and is not accelerated by overlying infection.

Note: Turner tooth = localised enamel defect on a single permanent tooth from infection or trauma to its primary predecessor. Compare with generalised defects from systemic causes such as fluorosis or childhood illness.