Gemination, fusion and confusion – unravelling a developmental dental anomaly

Abstract

Specimens of a tooth and soft tissue were submitted from a 4-year-old boy with a large radiolucency in the left anterior maxilla associated with apex of malformed deciduous left central incisor and the crown of the unerupted permanent maxillary left central incisor tooth. Macroscopically the tooth submitted had a broad crown composed of three fused crowns and a single root mass with three distinct longitudinally-orientated components. The soft tissue was consistent with an inflamed dentigerous cyst associated with the permanent central incisor. Decalcified sections of the hard tissue showed a small amount of enamel matrix remaining after decalcification. The dentine was normal and contiguous across the width of the tooth with a single (widened) pulp space containing vital pulp. Correlation with the radiographs demonstrated that the teeth submitted were of the deciduous series. Taking into account the number of identifiable deciduous teeth present, the specimen submitted must have represented fusion of the deciduous maxillary left central and lateral incisor tooth germs with an attempt at separation (gemination or twinning) of one of these tooth germs to form two separate teeth. Anomalies of the permanent teeth were also identified radiographically. The crowns of the maxillary left permanent central and lateral incisor teeth were aligned horizontally. There also appeared to be gemination of the unerupted mandibular left permanent lateral incisor tooth to give a crown wider than the contralateral tooth. This case appears to represent a rare (and possibly unique) example of fusion and gemination of the same tooth as well as other developmental dental anomalies elsewhere in the jaws.