Mechanism regulates tooth shape

HELSINKI, Finland, Sep 23, 2005 (United Press International via COMTEX) -- University of Helsinki and University of Kyoto researchers say the "balance of induction" mechanism directs the placement of tooth shape features.

The developmental initiation of the tooth shape features, known as cuss, is known to involve several developmental genes at the places of future cusps, but it was unknown how cusps form at the right places, according to the researchers.

Computer simulations on tooth development have suggested there should be a gene inhibiting induction of cusps, the researchers say.

The research team has identified this inhibitor to be a recently identified gene called ectodin.

The team generated a mouse that has no functional ectodin. The mice appear fairly normal but the areas forming cusps were much broader, resulting in cheek teeth whose shape resembles rhinoceros teeth more than mouse teeth.

Furthermore, the mice have extra teeth and sometimes adjacent teeth are fused. These results indicate there is a delicate balance of induction and inhibition in determining tooth cusps -- and that ectodin is a key gene in this developmental control.