Improper overlap of the front teeth can be in a number of forms:

Excess Overjet:

 

 

  • This is when the upper front teeth are too far ahead of the lower front teeth to fit properly.
  • The upper front teeth are usually around 1 to 2mm ahead of the lower front teeth.
  • Excess overjet can be due to a mismatch in the growth of the upper and lower jaws, typically where the lower jaw has not grown forward as much as the upper jaw and this can be due to an orofacial myofunctional disorder.
  • Excess overjet can also be from a poor oral habit such as sucking on a thumb or fingers or other objects like clothing or blankets. Such a habit will push the upper front teeth forward and the lower front teeth backwards.

Anterior Crossbite (underbite):

 

 

 

  • This is when the lower front teeth are ahead of the upper front teeth.
  • This can be due to a mismatch in the growth of the upper and lower jaws, typically where the upper jaw has not grown forward as much as the lower jaw and this can be due to an orofacial myofunctional disorder.
  • It can also be due to the front teeth growing into the mouth in an unusual angle and once the upper front teeth are caught behind the lower front teeth they will remain that way unless orthodontic treatment is done.

Deep Overbite:

 

 

 

  • This is when the upper and lower front teeth overlap vertically more than normal.
  • The biting edges of the upper and lower front teeth usually overlap vertically approximately 1- 2mm.
  • When the overbite is deeper than this it can cause problems with the overall fit of the bite and it often results in excessive wear of the edges of the lower front teeth.
  • A deep overbite often occurs when the lower jaw has not grown forward as much as the upper jaw and this can be due to an orofacial myofunctional disorder.

Anterior Open Bite:

 

 

 

  • This is when there is a vertical gap between edges of the upper and lower front teeth.
  • The upper and lower front teeth cannot touch together and it is not possible to bite things with the front teeth.
  • An anterior open bite can occur when there is an anterior tongue thrust swallow, a type of orofacial myofunctional disorder. In this situation the tongue typically rests low and forward against the front teeth and this light continuous pressure pushes the teeth apart.
  • An anterior open bite can also occur when the jaws grow in a more vertical pattern than normal. This can happen with chronic mouth breathing where the tongue rests low in the mouth instead of in the palate. This abnormal tongue rest position is a type of orofacial myofunctional disorder.