Transposition of mesial and distal aspects of maxillary first molars: case report.

Congenital absence of one or more teeth, hypodontia, is the most common developmental anomaly and is often accompanied by the presence of other tooth anomalies. In this case two Japanese sisters have several congenitally missing primary and permanent teeth and morphological abnormalities of maxillary first molars. One sister has transposition of mesial and distal aspects of a maxillary first molar, whose cusps display a normal shape. Another sister has maxillary first molars, which look like maxillary second molars. Mesio-distally shift of teeth is a very rare anomaly making this particular case important to analyze the teeth formation and development.