Around the age of 8 yrs, midline diastema is commonly seen in the upper arch, which
is usually misinterpreted as a malocclusion. This variation of normal development
is not very esthetic and is referred to as "Ugly duckling stage".
This phenomenon occurs due to a lateral pressure applied by the erupting canines
on the developing roots of lateral incisors which in turn press the roots of centrals
causing a lateral flaring of their crowns, and producing a midline diastema. As
the canines erupt, the pressure is transferred from the apical region of the maxillary
incisors toward their crown, improving their inclination and usually closing the
midline diastema.
