One or both upper permanent lateral incisors are congenitally
missing 1.5% of the time, which causes the upper permanent central incisors to
spread apart. If only one permanent lateral is missing, usually the midline
will shift to that side after the baby lateral is lost. The permanent laterals
usually grow in by age 8, so after that if no permanent laterals are present, you
might be suspicious and request an x-ray.
Once it is known that a lateral is missing, an orthodontist
should help with the decision of whether to open the space for an implant or
bridge, or to close it and reshape the cuspid to look like a lateral.
Upper permanent laterals often erupt backward
(behind the central incisors) if they are too crowded. The same is true of
lower laterals, but in the lower jaw, the tongue then pushes the laterals forward. Not so in the upper jaw.
However, in the upper jaw, if an incisor is
too far backward, it may incorrectly bite behind the lower incisors, and
tend to push the lower incisors too forward, even causing recession of
the outside gums of the lower incisors.
Treatment of this dangerous crossbite is often urgent, by moving the
upper incisor forward to in front of the lower incisors.
The
most frequently impacted permanent tooth (other than the lower third molar) is
the upper cuspid. If it is correctly positioned you can usually feel it before
it grows in by pressing your finger on the gums high above the baby cuspids. The most frequent problem is for a
semi-impacted cuspid to be mis-positioned too close to the midline and to push on the
root tips of the permanent lateral incisors, causing the lateral incisor crowns
to tip toward the lips and away from the midline, and occasionally it damages
the lateral incisor’s root by eroding it.
