How long do orthodontic retainers last? -

Longevity / Replacement intervals by type - Essix (Vivera®/Invisalign®/clear vacuum-formed plastic), Hawley, fixed (bonded). | Inspecting for damage - What to look for. | Survival statistics from research. | What to do if you can't wear your retainer.

How often do retainers need to be replaced?

Once you've completed your orthodontic treatment and have begun to wear retainers, you may wonder how long they're expected to last and when they should be replaced.

To find an answer ...

We've searched through published research studies to find out what's been documented about the usual lifespan of different types of orthodontic retainers.

And while collecting that information, we also made note of what's mentioned about what occurred, so you'll know what kind of damage to look for when evaluating your appliances.

How this page is organized ...

Since what you need to know varies according to the specific type of appliance(s) you wear, we've divided our coverage up into the following categories.

 


1) Essix retainers.

Picture of an Essix orthodontic retainer.

An Essix-style retainer.

An Essix (Vivera®) retainer is a clear-plastic, vacuum-formed appliance. In appearance, it looks very similar to an Invisalign® aligner.
As a point of clarification, "Essix retainer" is the generic name for this type of appliance. Vivera® is a brand name and subscription replacement service owned and operated by the makers of the Invisalign® system.

Length of service - What can you expect?

When evaluating the flimsy nature of an Essix (vacuum-formed) retainer, it's easy enough to have concerns about how long it will last.

a) What do research studies suggest?

While the amount of available research on the subject of retainer longevity is somewhat limited, it seems that the dental community currently interprets what's been published as suggesting that Essix retainers can be expected to provide a statistically similar "survival outcome" as Hawley appliances (the other most commonly used type of removable orthodontic retainer, discussed next).

b) Number of days of service.

When looking at the raw data from studies, one might have the first impression that Essix retainers have a shorter lifespan than Hawleys.

But as it turns out, there tends to be such a wide range in how long any particular person's appliances last, that in terms of statistical significance, neither type can be proven to provide a statistical advantage. Here's what we mean ...

Example #1 -

The conclusions of a study authored by Sun were that "no significant differences were observed in survival times between the 2 groups" (meaning clear-plastic vacuum-formed retainers vs. Hawleys).

But at first glance, this study's data seems to suggest differently.

The study's raw data showed that on average, upper and lower Hawley retainers lasted for 344 and 140 days respectively, as compared to 175 and 83 days for upper and lower Essix retainers respectively. (Numbers that suggest that Hawleys tend to last almost twice as long.)

But the standard deviation associated with these averages (the range of individual experiences) were substantial enough that no statistical difference could be shown.

For example, the lifespan of lower Hawleys was determined to be 140 days plus or minus 58 days vs. 83 days plus or minus 36 days for lower Essix appliances. So while different, there was enough overlap in what was experienced that neither type showed a statistical advantage in longevity.

Example #2 -

In contrast to Sun's conclusions, a study by Jin did find a statistically significant difference in the length of service provided by these types of appliances.

The median survival of Hawley retainers was 1529 days (4 years) as compared to only 105 days for plastic vacuum-formed retainers.

Example #3 -
As another estimate of the type of longevity you might experience, a study conducted by Zhu (discussed in our next section) found that Essix retainers provided service in the range of 261 to 307 days (plus or minus 100 days, more or less).

Section references - Sun, Jin

Common types of damage - What to look for.

Background - Appliance thickness.

Evidently, there's no accepted standard about how thick a vacuum-formed retainer should be.

We've seen 0.75, 1.0, 1.5, and 2.0 mm mentioned in research studies. (A credit card is usually .76 mm.) We're under the impression that 0.75 and 1.0 mm are the ones most commonly used. (You might keep that in mind if shopping for a DIY replacement retainer kit.)

Thick vs. thin survival rates.

One would think that using a thicker plastic would promote appliance longevity but research doesn't entirely confirm this.

A study by Zhu did find that breakage rates were higher for patients wearing 0.75 mm appliances vs. 1.0 mm ones. But overall, differences in survival times were not found to be statistically significant between the groups (with an average lifetime of 261 vs. 307 days for the thin and thicker plastics respectively).

Pictures of orthodontic retainers and accessories.

Our affiliate link can be used to learn about   replacement orthodontic retainers and accessories  on  Amazon.com.


Reasons for failure of clear-plastic/vacuum-formed retainers.

Here are the different types of damage we've seen mentioned in research studies.

a) Fracture / Breakage

This is the most-cited cause of failure of plastic vacuum-formed retainers. (43% of failures in the Jin and 59% in the Sun studies mentioned above.)

Breakage is an especially problematic event because no type of repair is possible. Instead, the appliance must be replaced.

Minute cracks.

We will mention that both the Sun and Zhu studies specifically stated that the formation of "slight cracks" in a retainer's plastic was not categorized as breakage and did not constitute a failure if they did not affect wearing the appliance.

(Despite this, if you see this kind of damage, it would be a good idea to let your dentist evaluate what's occurred.)

Where breakage tends to occur.

As might be expected, an Essix retainer is most likely to break at its narrowest point, because this region offers the least amount of stiffness/rigidity.

Due to this factor, there seems to be a tendency for lower appliances to break more often than upper ones, frequently at the appliance's midline (left-right center).

Another point of failure, for both uppers and lowers, is in the area of the eyeteeth. That's because stress tends to focus in this area when a retainer is removed. Especially in cases where one side is removed first and then the other.

c) Non-fitting

This reason refers to the situation where a retainer has lost its original shape and therefore no longer fits properly.

The shape of an Essix appliance might be distorted by a high-heat event (like being placed in hot water) or being crushed (when not in your mouth or being cleaned, your retainers should be kept in their hard retainer case).

b) Abrasion / Wear

Related to the thin nature of vacuum-formed appliances, it's easy enough to imagine how over time areas might show signs of wear. Most of the studies we read phrased this type of damage as "serious abrasion causing penetration," meaning the plastic had been completely worn through.

Small penetrations are probably of little concern (but go ahead and let your dentist decide). Large areas of wear could easily affect the rigidity of an appliance, and therefore inhibit it's ability to hold your teeth in place.

As compared to the other types of damage discussed above, this seems to be the least common cause of Essix retainer failure.

What to do if your Essix (vacuum-formed) retainer has failed.

If your retainer has sustained damaged or has been lost, obviously, it will need to be replaced.
How soon?

You should get in touch with your dentist's office promptly so they can make plans with you. Fabricating the replacement may take several days. (Cost estimates for replacement orthodontic retainers.)

Precautions.

Your teeth have the potential to shift during any period when your retainer isn't worn, so be prompt about contacting your dentist.

An ill-fitting appliance should not be worn because it may promote tooth movement to occur.

Makeshift solutions.

A boil-and-bite type of athletic mouthguard can be used as a retainer substitute. If it doesn't feel especially comfortable or secure in your mouth, rather than overnight wear, just wearing it multiple hours per day during waking hours can usually provide an effective compromise.


2) Hawley retainers.

Picture of a Hawley orthodontic retainer.

A Hawley orthodontic retainer.

A Hawley appliance is composed of a rigid plastic baseplate (acrylic, 2 mm thick) and embedded wires (a bow wire that holds the alignment of your teeth, and assorted clasps to hold the appliance in place).

As opposed to vacuum-formed Essix retainers that typically require replacement, if not damaged too extensively, a Hawley can often be repaired.

Hawley and Essix appliances are the most-used types of removable orthodontic retainers.

Length of service - What can you expect?

Number of days.

A study by Jin found a median survival time of 1529 days (4 years) for Hawley retainers. A period roughly 15 times longer than what they determined for Essix retainers.

In contrast, however, other studies have concluded that Hawleys and Essix retainers provide a statistically similar duration of service.

An example.

In its raw data, a study by Sun calculated an average survival duration of 344 and 140 days for upper and lower Hawley retainers respectively. And 175 and 83 days for upper and lower vacuum-formed retainers. And that data seemingly suggests that Hawleys last around twice as long.

But when the standard deviation of the individual measurements was taken into consideration, no statistical difference could be shown. (For example, lower Hawleys lasted for 140 days plus or minus 58 days vs. 83 days plus or minus 38 days for lower Essix retainers. With those ranges taken into consideration, what any one person from each group actually experiences may be quite similar.)

In practice ...

It would be our impression that the general consensus of the dental community is that based on the issue of longevity, both types of appliances make a reasonable choice.

Other considerations.

Lower Hawley retainers may be more prone to breakage than upper ones. For example, the data from the Sun study just mentioned shows this tendency (344 vs. 140 days respectively).

In part based on this reason, your dentist may feel that a Hawley appliance makes the right choice for your upper teeth, and a fixed (bonded/lingual) retainer (discussed below) makes a better choice for your lower ones.

Section references - Jin, Sun

Common types of damage - What to look for.

a) Fracture / Breakage

A study by Sun found appliance fracture to be the most frequent cause of Hawley retainer failure (over 60% of failure events).

Where breakage tends to occur.

It's simple enough to state that the acrylic baseplate of a Hawley appliance is most likely to crack or break in those regions where forces become most focused.

Of course, this includes the thinnest portion of the appliance. (For example, the left-right center of a lower Hawley is usually its narrowest, and therefore most fragile, area.) Forces also tend to become focused where the ends of the appliance's bow wire are embedded in the baseplate.

As opposed to while wearing your retainers, it's quite likely that it's removing them that strains them the most. Appliances that have an especially tight fit may experience stress because the baseplate must flex as it is removed. Removing an appliance one side at a time may amplify the amount of stress that's created.

Cracks - Early treatment is important.

The Sun study mentioned above stated that "retainers which had slight cracks on the surface were not considered as a breakage unless the retainers could not be worn because of crack expansion." However, in light of that statement, we do want to point out the following.

  • It's usually quite simple for a dentist to repair any cracks that have formed in the plastic baseplate of a Hawley, if the repair is made soon enough.
  • If instead the crack is allowed to expand to a point where it is visibly open, or worse yet, the appliance has broken into separate parts, repair may still be possible, but it's no longer as simple of an affair.

 

So if you notice any cracks developing, it's best to bring them to your dentist's attention sooner rather than later.

Section references - Sun

b) Non-fitting.

A Hawley retainer may no longer fit because of the damage it has sustained.

Drying out.

The acrylic baseplate of a Hawley retainer contains water content. And if the appliance is allowed to dry out, it may warp and therefore no longer fit properly.

Wire distortion.

The wires of your appliance have contours specifically crafted to match the alignment of your teeth.

If an event bends or distorts these wires, the retainer will at minimum need adjustment, and possibly even replacement.

The solution.
  • Generally, if your Hawley is not in your mouth, it should be kept wet or moist. And if you're away from home, placed in its hard case for protection.
  • Wetting your appliance and then placing it in a baggie before putting it in its case, can meet both of the above requirements.

 

What to do if your Hawley retainer has failed.

If your retainer has sustained damage or has been lost, obviously, it will need to be repaired or replaced.
How soon?

You should get in touch with your dentist's office promptly so they can make plans with you. If your appliance can be repaired, that process might be completed at the time of your appointment, or may possibly require a day or two of turn-around time.

Fabricating a replacement appliance may take several days. (Cost estimates for replacement orthodontic retainers.)

Precautions.

Your teeth have the potential to shift during any period when your retainer isn't worn, so be prompt about contacting your dentist.

An ill-fitting appliance should not be worn because it may promote tooth movement to occur.

Makeshift solutions.

A boil-and-bite type of athletic mouthguard can be used as a retainer substitute. If it doesn't feel especially comfortable or secure in your mouth, rather than overnight wear, just wearing it multiple hours per day during waking hours can usually provide an effective compromise.


3) Fixed / bonded / permanent retainers.

Picture of a permanent (bonded lingual wire) orthodontic retainer.

A fixed (bonded) retainer.

Like its name suggests, a fixed retainer is an appliance that's "permanently" bonded onto the backside of your teeth.

The device itself is usually some type of wire whose ends are embedded in small mounds of dental bonding (dental composite) that anchor it in place.

Longevity - What can you expect?

Findings from research.

In an overview of the subject of retainers, Alassiry states that bonded retainers typically provide predictable long-term service. It cites sources that suggest that the survival rate for this type of appliance ranges between 90% to 30% over 3 to 10-year periods.

A study by Jin found a median survival time of 1604 days (over 4 years). In comparison, the same study found survival times of 1529 and 105 days for Hawley and Essix/vacuum-formed retainers respectively.

Case selection.

Alassiry suggests that lower fixed retainers tend to provide longer service than upper ones by a factor of two. However, we'll point out that the Jin study did not confirm this opinion.

If a factor, this issue may primarily depend on issues associated with the patient's "bite." (Like the way the person's lower teeth direct forces onto the upper retainer.)

Alassiry also cites a source that suggests that most appliance bonding failures tend to occur in the first year, after which the survival of the retainer increases dramatically. (The Jin study also found a declining failure rate over time.)

So evidently, problematic cases and placement deficiencies tend to identify themselves early on, which is convenient.

Section references - Alassiry, Jin

Common types of damage - What to look for.

Bonding failures.

Jin found appliance debonding the most common cause of fixed retainer failure. (For example, it determined 64% of lower fixed retainer failures were due to this reason.)

The failure can take place at the enamel-to-bonding (dental composite) interface (meaning the composite has come loose from the tooth's surface). Or more commonly, one end of the wire has come free from its mound of composite (such as due to wear and/or breakage).

Wire breakage.

It's possible for the wire component of a bonded retainer to break (stress fracture).

Distortion.

Forces directed onto the wire component of a bonded retainer may distort it, thus leading to unwanted tooth movement.

Section references - Alassiry, Jin

What to do if your bonded retainer has failed.

If your retainer has sustained damage or has been lost, obviously, it will need to be repaired or replaced.

How soon?

You should get in touch with your dentist's office promptly so they can make plans with you. If repair is possible, that can be accomplished at the time of your appointment. Otherwise, fabricating a replacement may take several days. (Cost estimates for replacement orthodontic retainers.)

Precautions.

Your teeth have the potential to shift during any period when your retainer isn't in place. An ill-fitting fixed retainer may cause tooth movement. A loose fixed retainer may cause soft tissue irritation or damage, or be lost entirely and inadvertently swallowed.

Makeshift solutions.

If the retainer is entirely missing, a boil-and-bite type of athletic mouthguard can be used as a retainer substitute. If it doesn't feel especially comfortable or secure in your mouth, rather than overnight wear, just wearing it multiple hours per day during waking hours can usually provide an effective compromise.

Place the dislodged retainer in a hard container (like a pill bottle) so it doesn't get damaged any further.

If the retainer is still partially attached, possibly placing white orthodontic wax (readily available at most pharmacies) over its loose end may help to keep it from poking or scratching your tongue.

 

Update log -

03/18/2020 - Page created.

 
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 Page references sources: 

Alassiry AM. Orthodontic Retainers: A Contemporary Overview.

Jin C, et al. Survival analysis of orthodontic retainers.

Sun J, et al. Survival time comparison between Hawley and clear overlay retainers: A randomized trial.

Zhu Y, et al. Comparison of survival time and comfort between 2 clear overlay retainers with different thicknesses: A pilot randomized controlled trial.

All reference sources for topic Orthodontic Retainers.

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