Malocclusion (often called crooked teeth or a "poor bite") is the improper fit and alignment of the teeth and jaws. A common cause of malocclusion is teeth that have too much or too little room in the jaw.

Inherited traits, such as tooth and jaw size, mostly determine how well your teeth fit together. The most obvious sign of malocclusion is crooked or protruding teeth.

During the childhood and early teen years, orthodontists may straighten the teeth by changing the formation of the jaw, removing (extracting) selected teeth, or using fixed braces or removable appliances.

In adults, treatment with braces can straighten crooked teeth caused by a jaw problem, but any restructuring of the jawbone must be done with surgery, sometimes in combination with orthodontic treatment.