The term "malocclusion" (poor bite) refers to a number of possible
conditions. The most common are:
Upper protrusion (overjet). In an upper protrusion, the upper
front teeth are pushed outward (buck teeth). A small lower jaw may be the
cause. Pacifier use or thumb-sucking can also create this condition by pushing
the teeth outward, sometimes causing the roof of the mouth to change shape
Spacing or crowding problems. Too much or too little
room for the teeth can cause spacing or crowding problems. Crowding can prevent
permanent teeth from coming in properly or at all (impaction).
Misplaced midline. In people who have a misplaced
midline, the front center line between the upper front teeth doesn't match up
with the center line of the lower front teeth.
Open bite. Although the molars fit together in a
person who has an open bite, the upper and lower front teeth don't overlap.
This creates an opening straight into the mouth. An open bite can also be
present on one or both sides of the mouth.
Overbite. In a person who has an excessive overbite,
the upper front teeth reach too far down over the lower front teeth and, in
severe cases, can cause the lower teeth to bite into the roof of the
Underbite. An underbite is present when the lower
front teeth are farther forward than the upper front teeth.
Cross bite. A cross bite occurs when any or all of the
upper teeth fit into the wrong side of the lower teeth.
Rotation. Rotation is present when a tooth turns or
tips out of its normal position.
Transposition. Transposition occurs when teeth grow
(erupt) in one another's place.
A normal fit is when the upper teeth are slightly forward of the
Malocclusion, when there isn't a normal fit, is
classified by how the upper and lower teeth fit together. The bones of the jaw
are also checked for proper position in relation to the teeth.
Class I. Although the upper and lower molars are
properly positioned, the teeth are crowding together or have too much space.
Cross bites, rotations, and overlapping can also occur in severe cases.
Class II. The lower molars fit the upper molars but
are positioned toward the throat, drawing the chin back.
Class III. The lower molars are far forward and do
not fit into their corresponding upper molars. This arrangement creates a
jutting jaw and jutting lower front teeth, which are in a
cross bite with the upper teeth.
A jaw structure problem that children are born with can cause
malocclusion. Malocclusion can also cause the jaw joint to move out of place.
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