A malocclusion is an incorrect relationship between the maxilla (upper arch) and the mandible (lower arch), or a general misalignment of the teeth.  Malocclusions are so common that most individuals experience one, to some degree.  The poor alignment of the teeth is thought to be a result of genetic factors combined with poor oral habits, or other factors in the early years.
Moderate malocclusion commonly requires treatment by an orthodontist.  Orthodontists are dentists who specialize in the treatment of malocclusions and other facial irregularities.
The following are three main classifications of malocclusion:
Class I – The occlusion is typical, but there are spacing or overcrowding problems with the other teeth.
Class II – The malocclusion is an overbite (the upper teeth are positioned further forward than the lower teeth).  This can be caused by the protrusion of anterior teeth or the overlapping of the central teeth by the lateral teeth.
Class III – Prognathism (also known as “underbite”) is a malocclusion caused by the lower teeth being positioned further forward than the upper teeth.  An underbite usually occurs when the jawbone is large or the maxillary bone is short.