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 (upper palate).
- 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 mouth.
- 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 lower teeth. 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.