By Dr. John White

I wish I didn’t have to temper my patients’ enthusiasm the day they get their braces off by reminding them that straightening the teeth is only half the battle—the other is keeping them straight.

The simple truth is tissue has memory, and some of the forces that created a bad bite and crooked teeth are still in existence after treatment. When we rotate a tooth, the gum and fibers around the tooth have a memory and there is always a tendency for teeth to move back to where they were before braces. As a result, the rotation correction has to be maintained long enough for those cells to be replaced by new cells, which can take a couple of years.

We accomplish this by having patients wear retainers. These passive appliances hold teeth in the properly aligned position until they are stabilized.

Unfortunately, there is no simple answer to how long patients need to wear retainers. It is evaluated on a case-by-case basis. Depending on the nature of the orthodontic correction made, some teeth are more stable while others are not.

For example, when widening a patient’s arch, teeth will be relatively stable in younger patients but in older patients less so. Some patients have jaw musculature that is so strong, it tends to push the back teeth in, which makes the deep bite come back and requires a retainer that works against this tendency. Most cases have combinations of factors, so there are different types of retainers worn for different periods of time.

I also factor in whether traditional braces or clear aligners were used, since the retention period right after Invisalign is more critical because of the way the treatment is staged. With traditional braces, aligning the teeth and correcting the rotations are done early in the treatment process, followed by making the bite fit. With Invisalign, both are done simultaneously so the last bit of rotation correction may be during the last stage, which means the tooth may be more likely to twist back.

I take all of these considerations into account to determine which type of retainer to use, how many hours in the day it should be worn and how many months or years the retainer is required.