Basically one distinguishes between hereditary and acquired malocclusions of the jaw, whereby there is usually a combination of acquired malocclusions and genetic dispositions. When it comes to innate malocclusions, the size of the upper and lower jaw are disproportionate to each other, or there are missing teeth, which can frequently lead to asymmetrical positioning of the teeth.
 

At this patient the upper midline moved to the left, caused by a missing left lateral. (see "sample cases")

The acquired malocclusions are caused by bad habits such as thumb-sucking, prolonged use of the pacifier or compressing of the tongue. The sucking of the thumb, pacifiers and other objects, which continues after the child is three years old, can lead to severe deformations of the jaw and to malocclusions, especially of the front teeth. When it comes to the so called open sucking bite, the incisors of the upper and lower jaw gape apart, which makes it impossible to bite anything off. 
 

Pacifier-abusus of a child 4 years of age.

The importance of baby teeth is shown after their premature loss. If these "place-keepers" are lost too early e.g. as a result of cavities, the first permanent teeth are filling in these gaps and block the later teeth from coming through. The consequences can be positioning of the teeth that is too tight or teeth that are crooked.
 

Blocked out cuspits because of crowding and maybe also because of early loss of milk teeth. (see "sample cases")

milk-tooth decay and consequences (see "sample cases")