The topic of retention is a complicated and complex subject and you can read more about this topic, here [ Retention and Retainers ]. The actual study of how to keep teeth from moving after orthodontic treatment is over is still ongoing. Classic studies were performed here in the pacific northwest to determine how much teeth move and where they go once orthodontic treatment has been completed. Other studies compared retainers that cover all of the teeth versus those that simply wrap around the teeth. One study compared patients who wear their retainers both during the day and night to another group of patients who only wore their retainers at night.
From these studies we can draw some generalized conclusions. Conclusion Number One: the human body is under constant influence and subject to change. Most people understand that their body will continue to change over time. Crows feet develop near the eyes, while noses and ears get larger and then lips and other soft-tissue regions tend to droop over time. Orthodontists are well aware that this observation extends to the oral-facial region as we have studies tracking people into their seventies and we can demonstrate that the teeth, bones, and soft-tissues all change over the decades (albeit to a greater or lesser degree). The old adage is true, “the only constant is change”. As an orthodontist or an orthodontic patient, asking teeth to hold their position after treatment is really just asking them to do something that’s against their very nature. We must therefore be vigilant in our efforts and understand that Retention is for Life. Decades ago an orthodontist would hand a patient a retainer and tell them they should wear it every day for 6 months then switch to nights and then discontinue retainer wear after one or two years. We now know this to be an incorrect position. Very few people will end orthodontic treatment with their teeth in such a stable position that no unwanted tooth movement will be observed after the first 1-2 years following treatment. For this reason we will ask our patients to wear their retainers off and on for the rest of their life. An old dentist joke is “only brush and floss the teeth you want to keep”. Another orthodontic joke would sound like, “only wear your retainers for as long as you want your teeth to stay straight!”
Conclusion Number Two: Certain tooth positions are more stable than others but all teeth positions must be retained to expect long-term stability. Whether teeth are extracted or not – whether teeth come from a very crooked or only slightly crooked state – whether a patient has been in treatment longer or shorter period of time doesn’t ultimately matter. If the question is “will teeth move after treatment”? the answer is almost always “Yes” but where will they move and by how much? It may be true that a patient who has only mild crowding at the onset can afford to consider less extensive retainer options but all different orthodontic treatment:types, durations, and complexities will need to be retained. The lower six front teeth tend to be the most important as they support the lower back teeth in position as well as the upper front teeth and both of those groupings support the upper back teeth. For this reason, we highly recommend fixed (aka permanent) retainers on the lower front teeth. These retainers can take some getting used to with respect to brushing and flossing but they are highly recommended for most all patients.
Once the lower front teeth are held in place (ideally with a fixed/permanent retainer) the retention options for upper and lower retainers are numerous and depend on a number of factors. We often will choose clear retainers that wrap or envelop the teeth as a single arch. These clear retainers come in many different thicknesses and wear-resistance factors. Other times we use the “Old School” wire and acrylic retainers that wrap around teeth. The clear retainers tend to look a little nicer but also wear out a bit quicker. I warn patients to expect about 3 to 5 years of life from their clear retainers whereas they may get 20 or 30 years of life with an “Old School” Hawley retainer. Sometimes we can use retainers to continue very minor amounts of tooth movement whether space closure (for small slivers of space) or minor rotations. These scenarios are considered as a patient using a retainer (which is meant to hold teeth in place) as more of an active appliance (in other words moving teeth to their final slightly different position).
Our retention protocol is very similar to the following:
- Wear your retainer every single night for the first 2 years following orthodontic treatment. The first 6 months are hyper-critical as the soft-tissues and bony structures around the teeth are all stabilizing and reorganizing. Certain soft-tissue fibers will want to act like little rubber bands to spin teeth back out of alignment or move them back to where they came from. This unwanted tooth movement is known as “Relapse”. Holding the teeth very stable during this time-period is crucial to achieving long-term stability. If your teeth seem like they’re trying to shift or move back during the day then you should consider wearing your retainers during the day as well.
- Once you’ve made it past the two year mark, you can consider yourself out of the danger zone for immediate relapse. Teeth can still shift back to where they came from at this point but the tooth movements tend to be a bit more slow and manageable. The safest protocol is to still continue to wear your retainers every single night at this point to hold your teeth in their ideal position. Alternatively, after the 2-year anniversary of your treatment finish, you can try in your retainers at night and see if you can feel any “tightness”. That “tightness” may indicate your teeth are trying to shift and you should still wear your retainer that night. If you don’t feel any significant “tightness” and a visual inspection shows that no unwanted tooth movement appears to be occurring you may be able to “take a night off” and try in your retainers the next night. Visual indicators of unwanted tooth movement may be “gaps” that develop between a tooth and its clear plastic retainer enclosure or a space that opens between a tooth and its immediate neighbor. Always remember to insert your retainers each night as a test to see if you can detect any tooth movement.
If you want, you can read more about this topic, here [Retention and Retainers].