A 17-year-old dislikes the appearance of her teeth. Radiographs show obliterated pulp chambers and short, blunted roots. Which cell is primarily affected?

Correct answer: D. Odontoblasts

• A. Cementoblasts produce cementum; their failure is seen in hypophosphatasia with premature tooth loss.
• B. Osteoblast defects appear in osteogenesis imperfecta — which, notably, often co-occurs with dentinogenesis imperfecta because both involve collagen/dentin matrix genes.
• C. Ameloblasts produce ENAMEL; their dysfunction causes amelogenesis imperfecta, where the enamel is thin, pitted, or hypomineralized but the pulp and roots are normal.
• D. CORRECT. Obliterated pulp chambers with short, blunt roots and discolored, translucent teeth describe DENTINOGENESIS IMPERFECTA — a defect of DENTIN produced by ODONTOBLASTS (mutation in the DSPP gene). The abnormal dentin is poorly mineralized and irregular, continues to be deposited until the chamber obliterates, and provides inadequate support for the overlying enamel, which then chips away, leading to rapid attrition.

Note: Enamel appears normal at first in DI, but it fractures away because the underlying dentin cannot support it. That is the key distinguishing point from AI.