Crowding Teeth may be aligned poorly because the dental arch is small and/or the
teeth are large. The bone and gums over the roots of extremely crowded
teeth may become thin and recede as a result of severe crowding. Impacted
teeth (teeth that should have come in, but have not), poor biting relationships
and undesirable appearance may all result from crowding.
Overjet
or protruding upper teeth Upper front teeth that protrude beyond
normal contact with the lower front teeth are prone to injury, often indicate
a poor bite of the back teeth (molars), and may indicate an unevenness
in jaw growth. Commonly, protruded upper teeth are associated with a lower
jaw that is short in proportion to the upper jaw. Thumb and finger sucking
habits can also cause a protrusion of the upper incisor teeth.
Deep
overbite A deep overbite or deep bite occurs when the lower incisor
(front) teeth bite too close or into the gum tissue behind the upper teeth.
When the lower front teeth bite into the palate or gum tissue behind the
upper front teeth, significant bone damage and discomfort can occur. A
deep bite can also contribute to excessive wear of the incisor teeth.
Spacing If teeth are missing or small, or the dental arch is very wide, space
between the teeth can occur. The most common complaint from those with
excessive space is poor appearance.
Crossbite The most common type of a crossbite is when the upper teeth bite inside
the lower teeth (toward the tongue). Crossbites of both back teeth and
front teeth are commonly corrected early due to biting and chewing difficulties.
Underbite
or lower jaw protrusion About 3 to 5 percent of the population has
a lower jaw that is to some degree longer than the upper jaw. This can
cause the lower front teeth to protrude ahead of the upper front teeth
creating a crossbite. Careful monitoring of jaw growth and tooth development
is indicated for these patients.
Teeth may be aligned poorly because the dental arch is small and/or the
teeth are large. The bone and gums over the roots of extremely crowded
teeth may become thin and recede as a result of severe crowding. Impacted
teeth (teeth that should have come in, but have not), poor biting relationships
and undesirable appearance may all result from crowding. 
Upper front teeth that protrude beyond
normal contact with the lower front teeth are prone to injury, often indicate
a poor bite of the back teeth (molars), and may indicate an unevenness
in jaw growth. Commonly, protruded upper teeth are associated with a lower
jaw that is short in proportion to the upper jaw. Thumb and finger sucking
habits can also cause a protrusion of the upper incisor teeth.
A deep overbite or deep bite occurs when the lower incisor
(front) teeth bite too close or into the gum tissue behind the upper teeth.
When the lower front teeth bite into the palate or gum tissue behind the
upper front teeth, significant bone damage and discomfort can occur. A
deep bite can also contribute to excessive wear of the incisor teeth. 
If teeth are missing or small, or the dental arch is very wide, space
between the teeth can occur. The most common complaint from those with
excessive space is poor appearance. 
The most common type of a crossbite is when the upper teeth bite inside
the lower teeth (toward the tongue). Crossbites of both back teeth and
front teeth are commonly corrected early due to biting and chewing difficulties. 
About 3 to 5 percent of the population has
a lower jaw that is to some degree longer than the upper jaw. This can
cause the lower front teeth to protrude ahead of the upper front teeth
creating a crossbite. Careful monitoring of jaw growth and tooth development
is indicated for these patients.