Types of orthodontic retainers: Removable - Essix, Hawley, Vivera®  |  Permanent - bonded, fixed, lingual wire -

Applications | Advantages & Disadvantages | Pictures | Which makes the best choice? - Removable vs. Fixed, Hawley vs. Essix

Once your dentist has finished straightening your teeth, the retention phase of your treatment will need to begin.

During this phase (which at least in theory may last the remainder of your life), you will be required to wear some type of dental retainers. This is true no matter what kind of braces or orthodontic system was used.

Without proper retention, orthodontic relapse (the return of features of your original malocclusion) is likely to occur.


 

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Types of orthodontic retainers.

There are generally two kinds of dental retainers, Removable and Fixed.

And just as their names imply, they differ by way of the fact that one type is permanently attached (bonded) to your teeth whereas the other is just worn according to your dentist's instructions.

There's no single best type for everyone.

You'll need to quiz your dentist about which of these types of appliances they'll consider for use with your case. And then the specific advantages and disadvantages each one offers your situation.

Listen seriously to what your orthodontist has to say in regard to their recommendations. Remember, they've just completed providing you with months to years of treatment. And as a result they'll no doubt have a founded opinion about how suited each type of appliance is to your situation. And also about which type you'll be most likely to comply with (wear as instructed).

This latter point is an astoundingly important one because after all, it's only the wear of your retainers that can insure the successful outcome of your orthodontic work over the remainder of your life.

You may wear more than one kind of appliance.

It's quite common that a different type of retainer is used with each individual arch. The most common configurations are: 1) Hawley upper, Permanent (fixed) lower. 2) Essix upper, Permanent (fixed) lower.

A) Permanent orthodontic retainers.

Other terms used to refer to "permanent" appliances are "bonded" or "fixed" retainers. That's because they're attached directly to your teeth. They cannot be removed.

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

A permanent (bonded) orthodontic retainer.

Construction.
  • The simplest form of this type of retainer is one where it consists of a single strand of solid or braided wire.
  • The wire is bent so it fits passively up against the backside (tongue or palate side) of the straightened teeth.
  • It's then bonded in place using dental composite (standard dental bonding material).

Fixed retainers were first introduced in the 1970's. This was an era when many new applications for the science of dental bonding were introduced.

Examples.
  • The most common type of fixed dental retainer is a small wire that has been positioned on the backside of a patient's lower front teeth (it's sometimes referred to as a "lingual wire"). Valiathan (2008) states that this is the most frequently used retainer for lower teeth. [page references]
  • While less common, bonded retainers can also be utilized with upper teeth. Although, the patient's "bite" sometimes makes this configuration awkward or impossible.
How long is a fixed retainer left in place?

Unless there are reasons why it should be removed (see below), bonded retainers are typically left in place indefinitely. One study (Booth 2008) found that this type of appliance is capable of providing acceptable service in excess of 20 years.

Advantages and disadvantages of permanent retainers.

1) Fixed retainers work better in some applications.

Research suggests that a fixed retainer is better able to hold a patient's lower front teeth (incisors) in position during the first months immediately following the completion of their active orthodontic treatment (Meade 2013, O'Rourke 2016).

  • In cases where the potential for teeth shifting in this region is a concern, the treating orthodontist may feel strongly about placing a bonded retainer.
  • With some cases a combined approach is used, where the patient wears both a bonded retainer (full time of course) and a removable one (full or part-time).
2) Fixed retainers make it harder to clean your teeth.

The biggest disadvantage of bonded retainers is that they make it more difficult for the patient to brush and especially floss.

Study - Cleaning difficulty. - Sawhney (2013) polled subjects who wore different types of orthodontic retainers. One question asked was how difficult it was to maintain oral hygiene.

  • In regard to upper retainers, bonded ones were considered the most difficult to clean (24%) vs. Hawley (8%) and Essix (4%).
  • Similar findings were found with lower appliances (the most frequent application for fixed retainers) at a rate of 33% vs. Essix (9%) and Hawley (6%).

Study - Gum inflammation. - In situations where proper maintenance isn't performed, dental plaque and tartar will tend to accumulate in the region of the retainer and this may place the person at greater risk for complications such as gum disease.

  • A study by Heier (1997) evaluated orthodontic patients that either wore removable or bonded retainers at 1, 3 and 6 month intervals.
  • It determined that while there was more plaque and tartar build up on the teeth of subjects having fixed retainers, the gum health of the groups did not vary significantly.

But don't interpret this study as suggesting that this issue is never a problem, it just shows that it isn't always. For people for whom it is, their appliance should be removed and another form of retention used.

Floss threaders. - Effective flossing around a bonded retainer typically requires the use of a floss "threader." This device allows the user to work the floss underneath their wire, so they can floss the portion of their teeth in that region. (More details about how to clean around fixed retainers.)

3) With permanent appliances, compliance is never a concern.

The great advantage of bonded retainers is that the dentist does not have to rely on patient cooperation. Unlike removable retainers that may be misplaced or simply not worn, fixed appliances are always in place to perform their duty.

4) The retainer can't be seen.

Another nice advantage of permanent retainers is that due to their location on the backside of the teeth it's very difficult for others to detect them.

In most cases they can be consider to be the most esthetic type of retainer.

5) Speech is usually unaffected.

Unlike removable retainers that may, bonded appliances usually don't affect a person's speech.

 

B) Removable orthodontic retainers.

There are two basic categories of removable dental retainers. They are the Essix and Hawley appliances. As discussed below, each type offers its own specific advantages and disadvantages.

In terms of usage, a study by Pratt (2011) found that 47% of orthodontists (USA) tend to place Essix retainers and 43% Hawley. Possibly more revealing is that nearly half of the respondents reported reducing their use of Hawley retainers over the past 5 years (only 6% reported increasing).

1) Essix retainers.

Essix style orthodontic appliances are also sometimes referred to as "invisible" retainers because they're made using clear plastic. They may also be referred to as "overlay" retainers because they fully cover over the teeth (and even some of the surrounding gum tissue). They were first introduced in the early 1970's.

Construction.

These are vacuum-formed appliances that are relatively simple to make. Many dentists fabricate them right in their own office.

Picture of an Essix orthodontic retainer.

A vacuum-formed (Essix-style) orthodontic retainer.

  • An impression of the patient's teeth is taken and transformed into a plaster cast.
  • A thin sheet of plastic (around 0.030 inch, which is on the order of thickness as a credit card) is then heated and using a vacuum unit is sucked down over the cast (thus creating the needed shape for the retainer).
  • The excess plastic is trimmed away. The finished appliance may cover all of the patient's teeth on the arch (upper or lower jaw) or else just some grouping of them.
Appearance.

These retainers look very similar to Invisalign® aligners. But instead of being changed every few weeks, they are worn indefinitely (per your dentist's instructions).

For Invisalign® patients, the use of Essix retainers may seem the logical choice since they are already familiar with wearing this type of appliance. And in fact, Align Technology, Inc. (the maker of the Invisalign® system), manufactures its own version of the Essix appliance called Vivera® retainers.

Advantages and disadvantages unique to Essix retainers.

Advantages.
  • When they're worn, they are fairly unnoticeable. However, similar to Invisalign® aligners there can be tip-offs that you're wearing them. And, in fact, Sawhney (2013) found that only 77% of patients who wore upper Essix retainers considered their appearance "good."
  • This same study also reported that wearers felt that Essix-style retainers interfered with maintaining oral hygiene the least.

    [This point doesn't really make sense unless some people try to brush their teeth with their (fully removable) Hawley retainer in place, which seems a sad commentary about the level of effort some expend when performing oral hygiene.]

  • Polling of orthodontists by Pratt (2011) determined that over half of respondents felt that patient compliance (appliances were worn as directed) was higher with Essix vs. Hawley retainers. Only 6% felt that the reverse was true.

    However, a second study by Pratt (2011) that evaluated long-term patient compliance found that while initially higher, Essix retainer use decreased at a faster rate than for Hawley appliances. And at 2 years out, patient compliance was greater with Hawley retainers overall.

Disadvantages.
  • While usually less so than with Hawley retainers, Essix appliances can interfere with speech. (In the same way as Invisalign® aligners.)
  • Essix retainers are non-adjustable. Your dentist can't use them to make further alignment corrections or refinements. (They can with a Hawley.)

A damaged Essix retainer.

Picture of a cracked Essix retainer.
  • Essix retainers should be inspected regularly to look for cracks, holes, tears or breakage. Also, the plastic from which they're made may warp if exposed to (wet or dry) heat. Generally speaking, a damaged Essix appliance cannot be repaired and instead must be remade.

    Despite having a relatively flimsy appearance, studies suggest that Essix retainers have a similar survival rate as Hawley appliances (Keenan 2012, Sun 2011). Sawhney (2013) found that upper Hawley and Essix retainers experience similar rates of breakage (25% vs. 23%).


2) Hawley orthodontic retainers.

Hawley appliances are the granddaddy of retainers. They were first introduced in the 1920's. And even today they are the most used type of retainer for upper teeth. (Valiathan 2010)

Picture of a Hawley orthodontic retainer.

A Hawley orthodontic retainer.

Construction.

Hawley retainers have a design that involves wires and clasps anchored in a relatively thick plastic body. The plastic aspect covers over the roof of the patient's mouth or else lies along the tongue side of their lower teeth.

The clasps grasp around selected teeth so the retainer is anchored securely. The retaining "bow" wire runs across the front side of the teeth and maintains their alignment.

Appearance.

The most noticeable feature of a Hawley retainer is the bow wire that runs across the front side the the patient's teeth. The plastic body remains well hidden. Sometimes it's constructed using plastic that has bold colors or a personalized design.

Advantages and disadvantages unique to Hawley retainers.

Advantages.
  • A Hawley retainer is adjustable. That means it can be used to further refine the alignment of your teeth. Or, if you've failed to wear your retainer faithfully, it can be adjusted so to guide your teeth back into place.
  • Hawley's appear to have a more rugged construction than Essix-style retainers. But as we mention above, recent studies have suggested that patient's experience similar survival rates for both types of appliances.
  • Where as an Essix must be replaced if damaged, a Hawley can be repaired (either it's wire or plastic components).
Picture showing the bow wires on upper and lower Hawley orthodontic retainers.

The bow wires of Hawley appliances are quite obvious.

Disadvantages.
  • One of the biggest disadvantages of wearing a Hawley is its appearance. It has a bow wire that runs across the front side of the wearers teeth and it's quite obvious to others when the retainer is worn.

    However, Sawhney (2013) found only about half of Hawley wearers found its appearance objectionable (59% for upper appliances, 53% for lowers).

  • The thickness of the retainer's plastic body (especially in the area behind your upper front teeth) can interfere with speech. If you have this difficulty, however, your dentist should be able to at least minimize this problem by trimming the plastic so it's as thin as possible.

    When polling patients who wore upper retainers, Sawhney (2013) found that 82% of Hawley wearers felt that their appliance affected their speech (as opposed to 62% with Essix and 8% fixed).

    With lower retainers, these numbers were: 60% Essix and Hawley, 6% fixed.

    Following an evaluation of this subject, Wan (2017) simply states that while distortion in speech could be identified in subjects wearing either Hawley or vacuum-formed retainers (Essix), changes in articulation were more obvious in the group wearing Hawley appliances.


General advantages and disadvantages of removable retainers.

Besides the specific factors outlined above for each individual type of appliance, there are some general issues associated with removable retainers that should be considered.

a) Their biggest advantage is also a disadvantage.

Just as their name implies, removable retainers can be taken out. You can remove them when you eat, brush and floss, or during those times when wearing them is not required.

The problem is this also means that they can be lost, or simply not worn (dentists call this "poor patient compliance"). And no retainer can perform its intended function if it's not in place.

However when they are worn as directed, studies have shown that the part-time wear of removable retainers is as effective as full-time wear (of removable or fixed appliances). (Meade 2013)

b) Removable appliances may cause excessive salivation.

Wearing anything in your mouth may trick it into producing extra saliva.

That's because, to our bodies, having something in our mouth is usually a sign that a meal is coming. So in response to wearing your retainer, it will start to produce the extra saliva it thinks it will need for the upcoming "meal."

This isn't much of a problem for most people. And over time, your body should return to normal as it realizes that the extra saliva isn't required.


Hawley vs. Essix retainers- Which do most patients prefer?

To give you an idea of how patients seem to feel about wearing these types of appliances, we'll report the findings of a study by Hichens (2007). This investigation evaluated subjects' use of Hawley and Essix (vacuum-formed) retainers during the first 6 months following the completion of their orthodontic treatment.

330 patients were involved, broken into roughly equal groups (Hawley vs. Essix). One specific goal of the study was to measure patient satisfaction with the appliance they wore (via the use of a questionnaire). The study's findings were:

  • Patients wearing Essix retainers were somewhat more likely to wear their appliances as instructed (85% Hawley vs. 95% Essix). (The assumption here is that Essix retainers were worn more regularly because they were found to be less objectionable.)
  • Wearing a Hawley retainer tended to cause more embarrassment for subjects (17% vs. 7% for Essix), particularly in terms of esthetics (Hawley appliances have a wire that shows) and speech interference (caused by the thickness of the portion of the appliance that covers the palate).

    However, despite these difficulties both groups complied similarly in wearing their appliances "away from home" (in public). Nor was there a difference in number of lost appliances (which might be more likely to occur if taken out when "away from home").

  • Comfort levels associated with retainer wear was found to be similar for both groups (around 35% reported never experiencing discomfort, 52% reported occasional discomfort).
  • Subjects in the Essix group tended to give a substantially higher rating for their overall experience in wearing retainers (as compared to Hawley wearers) in most measured categories. (Much Better- 33% vs. 9% | Better- 48% vs. 34% | Same- 16% vs. 31% | Worse- 2% vs. 19% | Much Worse- 1% vs. 7%).

    In regard to this measurement however, it needs to be pointed out that this study's participants only wore one type of retainer. And the rating of their experience was based on a comparison to wearing braces.

    So in regard to the statistics above, 33% of subjects thought wearing an Essix retainer was "Much Better" than having braces, while only 9% of Hawley appliance wearers thought so, etc...

Based on all of these findings, it seems reasonable enough to suggest that patients tend to prefer having Essix-style (vacuum-formed) retainers.

 

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