What is the best diagnostic test to distinguish AMELOGENESIS IMPERFECTA from DENTINOGENESIS IMPERFECTA?

Correct answer: B. Radiographic examination

• A. Family history establishes an inheritance pattern, and both conditions are usually autosomal dominant. It helps in counselling but does not distinguish the two.
• B. CORRECT. The RADIOGRAPH is decisive because the two conditions affect different tissues and therefore produce opposite radiographic pictures. In AMELOGENESIS IMPERFECTA the defect is confined to ENAMEL, so the roots, pulp chambers and dentin appear NORMAL — only the enamel is thin, absent, or of reduced radiodensity so that it fails to contrast with dentin. In DENTINOGENESIS IMPERFECTA the dentin is defective, giving the pathognomonic picture of BULBOUS crowns with cervical constriction, SHORT, thin, blunted roots, and progressive OBLITERATION of the pulp chambers and canals.
• C. Hair abnormalities point toward the ectodermal dysplasias, not toward either of these conditions.
• D. BLUE SCLERAE are a feature of osteogenesis imperfecta, which accompanies Shields type I DI — a genuinely useful clue, but it is present only when DI occurs as part of OI, not in the isolated (Shields type II) form. It is therefore a supportive sign rather than the definitive test.

Note: Colour is another useful discriminator, though less definitive: DI gives an OPALESCENT blue-grey to amber-brown tooth with enamel that chips away from the defective DEJ, exposing dentin that then wears rapidly. AI produces enamel that is pitted, grooved, thin, or soft and yellow-brown depending on subtype (hypoplastic, hypomaturation, or hypocalcified).