= odontogenic developmental hamartomatous malformation → obstruction of tooth eruption

Prevalence: most common odontogenic tumor (67%)

Age: 2^nd decade; before or after tooth eruption

Histo: various tooth components including dentin + enamel

Associated with: impacted tooth (in 50%); dentigerous / calcifying odontogenic cyst (occasionally)

Location: between roots of teeth

Site: pericoronal

• sharply marginated lesion
• initially purely radiolucent ± small calcifications
• later radiopaque mass with a lucent halo
• 1–3 cm in diameter
• may be surrounded by lucent follicle

Types:

1. simple
   • supernumerary tooth
2. compound odontoma (more common)
   • multiple small toothlike structures (abortive teeth = denticles)
     Site: anterior maxilla
3. complex odontoma
   = conglomerate mass of enamel + dentin
   Site: molar region (most common)
   • well-defined lesion with amorphous calcifications
   • low-attenuation halo surrounds odontoma
     DDx: osteoma (NO halo)

Cx: impaction, malpositioning, resorption of adjacent teeth

DDx: focal cemento-osseous dysplasia, osteoma, ameloblastic fibroodontoma, adenomatoid odontogenic tumor