INTRODUCTION
Crowding is the general term used to describe crooked, turned, or overlapped teeth. Crowding can accompany almost any malocclusion (bad bite), including overbites, underbites, and crossbites. Crowding may involve one or more teeth, and the condition probably affects 90 percent of the general population to some degree.

What Causes Crowding?
In most cases, the main culprit is genetics. If you inherit a relatively small jaw and relatively large teeth, your teeth literally must jostle for position in your mouth. Oral habits, such as nail-biting, finger-sucking, or chewing on clothing, can aggravate crowding, especially among children.

Aside from Aesthetic Concerns, Why Is It Important to Correct Crowding?
Crowding can eventually lead to pain and clicking of the jaw joint-- temporo-mandibular joint disorder (TMJ)--but it is difficult to predict which children will be affected when they get older.

Adults with crowded teeth may experience no problems at all. However, if you cannot thoroughly clean your teeth because they are too close together or overlap, you are at increased risk for decay and periodontal disease, which can lead to tooth loss. Getting your teeth straightened gives you and your dentist better access to cleaning your teeth well.

What Is the Most Effective Way to Correct Crowding?
The key to treating crowding is diagnosing the condition early, when the child still has some baby teeth left. The last two bottom baby teeth--the second primary molars--are actually bigger than the adult bicuspids coming in behind them. If a functional appliance or braces can be put on the adult teeth around age 9, these bottom baby teeth act as "spacers." When they fall out, the appliance or the braces hold back the rest of the molars, which otherwise would likely move forward to fill in the gap.

A functional appliance called an "expander" can help resolve crowding of the upper teeth. By turning a screw in the appliance every night, the expander slowly widens the upper jaw to make room for all the adult teeth. Fixed and removable expanders are available, and it generally takes about four months for the expansion process to be completed. Afterward, the expander remains in the mouth for a total of six to nine months. Then a retainer is worn to ensure that the expansion is permanent.

Adults with crowding receive a full or partial set of braces, depending on the severity of the abnormal tooth positions and how many teeth are involved.

How Long Are Braces Usually Worn to Correct Crowding?
The average length of treatment with braces is about 2 years, but it can take 3 years if the crowding is severe or is accompanied by a significant malocclusion.

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