Are extractions needed for orthodontic treatment?

Most often, patients present to my office hoping for a quick simple solution to fix their bite, smile, and appearance. They want faster treatment times, they want all their teeth to be “straighten”, and they want a beautiful smile. While these are treatment goals that every orthodontist considers, there are various anatomical factors that influence the treatment outcome.

First, there needs to be adequate space to even move teeth. Any case that has mild crowding (≤4mm) can typically be treated nonextraction with interproximal reduction. The term, interproximal reduction, is a supplemental procedure used frequently in orthodontics where teeth are “manicured” to gain space needed. HOWEVER, there is a maximum amount of 0.5mm per contact. In layperson terms, if more than 0.5mm of manicuring is performed, the patient could exhibit a high amount of tooth sensitivity.

What does this mean? It means that any amount of crowding above 5mm may require teeth extracted. The analogy that I like to use to describe this clinical scenario is the parking garage analogy. Your mouth typically has 28 teeth (excluding 3rd molars). The amount of space in the parking garage is pre-determined (since jaws cannot grow after a certain age). Teeth are also analogous to the cars since all teeth come in different shapes and sizes. For all the cars to fit, some cars need to leave the parking garage to make all the cars fit into the parking garage (mouth). See Fig 1.

Fig 1: An example of how teeth in the mouth are like cars in a parking garage. There are only so many parking spots, so if too many cars are present, some need to leave for the cars to all fit.

Another interesting question I receive, can expansion eliminate the need for extractions? The answer is no since we only gain only a fraction of space for every millimeter of expansion (approximately 0.7mm of arch perimeter for every 1mm of expansion). This basically means that there will be approximately a maximum of 2-8mm space gained with expansion, but careful observation must be warranted to prevent teeth from coming out of the bone, even with TAD expanders. There is also no way to do this on the lower arch since the lower arch cannot be expanded.

Here are some of my own cases to show where extractions were done in order to achieve a great clinical outcome:
Example Case: