If you have crooked teeth and/or a misaligned bite (an underbite or overbite), there are a variety of treatments that can help straighten teeth, including braces and retainers.
Many general dentists are doing basic alignment and orthodontics, but orthodontists specialize in correcting irregularities of the teeth.
In some cases, a removable retainer will be all that's necessary. In other rare cases (especially when there is an extreme overbite or underbite), surgery may be necessary. In most cases, however, braces will be needed.
Newer "mini-braces" which are much smaller than traditional braces, may be an option for some. There is another method of straightening teeth that uses removable plastic retainers that may also work when crowding of the teeth is not too severe. Your orthodontist will discuss the various types of braces with you and determine which might be the best option for your situation