Comparisons of Oral Devices for Snoring
Nineteen types of oral appliances for snoring/obstructive sleep apnea are reviewed.By James E. Eckhart, DDS
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A study was performed on 19 types of oral appliances for snoring/obstructive sleep apnea. The appliances were categorized into two groups, mandibular advancers and tongue advancers. A set of limited criteria was developed by which an appliance could be evaluated, and the criteria were weighted. Evaluations were then performed on the appliances, and they were rated according to satisfaction of criteria. The rating table should help a dentist in selecting an appliance that will be accepted by the patient and effective in treating snoring/obstructive sleep apnea. |
Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.
A dentist considering treating a patient for snoring might not be aware of the broad variety of oral devices available. Even if aware, he or she might still be perplexed at which appliances might be best in different circumstances. This paper is intended to familiarize the dentist with the choices and to help in the selection of snoring treatment devices. The patient should be provided with an appliance that is comfortable and does its job. If this is done, the field of medicine may more quickly increase its acceptance of dentistry's helpful role in sleep medicine. However, for medicine to accept dentistry's role, dentistry must understand enough sleep medicine to meet the standards of care set by medicine.1 A dentist entering this field must be aware that snoring itself has certain morbidities2-8 and that it may be a sign of upper airway resistance syndrome or obstructive sleep apnea, whose symptoms, associated morbidities, and diagnostic protocols the dentist must also know. This paper does not directly address the question of efficacy at treating obstructive sleep apnea with oral devices, which can best be evaluated by polysomnography after delivery of an oral device. No polysomnographies were performed as part of this study. However, this paper does offer guidance regarding which appliances are most favorable from both the dentist's and patient's viewpoints relative to comfort, convenience, and the stopping of snoring. The more highly rated devices might be considered preferable for treating snoring and perhaps as logical starting places for selection of appliances to treat obstructive sleep apnea.
For this study, it was decided to exclude oral devices that depend on contact with the soft palate or dorsal surface of the posterior tongue, because they produce gagging responses and do not compete in any important way with the devices studied herein. It was also decided to exclude appliances that are not offered commercially and to exclude a few commercially available appliances that are relatively ineffective or require too much effort compared to the benefit to be gained. Further, this study may have examined an appliance from one vendor that is available from more than one vendor, and might therefore present only a partial view of the truth about an appliance.
Categories of Appliances
Effective, readily accepted oral appliances for snoring/obstructive sleep apnea work by moving either the mandible or the tongue forward. The following classification of appliances fit the existing commercially available appliances.
Mandibular Advancers
One-Piece
* Boil-and-bite -- Snore Guard (Figures 1a and b) and Snore Free (Figures 2a and b).
Figure 1a. (above) Snore Guard, front view.
Figure 1b. (below) Snore Guard, side view.
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Figure 2a. Snore Free, front view.
|  Figure 2b. Snore Free, side view. |
* Lab-fabricated -- MIRS (Figures 3a and b), SNOAR (Figures 4a and b), Mandibular Repositioner (Figures 5a and b), Elastomeric (Figure 6a and b), and NAPA (Figures 7a, b, and c).
Figure 3a. MIRS, front view.
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Figure 3b. MIRS, side view.
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Figure 4a. SNOAR, front view.
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Figure 4b. SNOAR, side view.
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Figure 5a. Mandibular Repositioner, front view.
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Figure 5b. Mandibular Repositioner, side view.
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Figure 6a. Elastomeric, front view.
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Figure 6b. Elastomeric, side view.
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Figure 7a. NAPA, front view.
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Figure 7b. NAPA, side view.
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Figure 7c. NAPA, top view.
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Two-Piece
* Boil-and-bite -- Thera Snore (Figures 8a, b, and c).
Figure 8a. Thera Snore, front view.
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Figure 8b. Thera Snore, side view.
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Figure 8c. Thera Snore, front view (disarticulated).
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* Lab-fabricated -- Silent Nite (Figures 9a and b), Herbst (Figures 10a and b), Restore (Figures 11a, b, c, and d), TAP (Figures 12a, b, c, and d), PM Positioner (Figures 13a and b), Silencer (Figures 14a and b), EMA (Figures 15a and b), Klearway (Figures 16a, b, anc d), and Hilsen (Figures 17a, b, and c).
Figure 9a. Silent Nite, front view.
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Figure 9b. Silent Nite, side view.
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Figure 10a. Herbst, front view.
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Figure 10b. Herbst, side view.
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Figure 11a. Restore, front view. |
Figure 11b. Restore, side view. |
Figure 11c. Restore, top view (disarticulated). |
Figure 11d. Restore, front view (closeup). |
Figure 12a. TAP, front view. |
Figure 12b. TAP, side view.
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Figure 12c. TAP, rear view.
(disarticulated). |
Figure 12d. TAP, top view (disarticulated). |
Figure 13a. PM Positioner, front view. |
Figure 13b. PM Positioner, side view.
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Figure 14a. Silencer, front view.
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Figure 14b. Silencer, side view.
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Figure 15a. EMA, front view.
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Figure 15b. EMA, side view.
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Figure 16a. Klearway, front view.
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Figure 16b. Klearway, side view.
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Figure 16c. Klearway, inferior view.
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Figure 17a. Hilsen, front view.
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Figure 17b. Hilsen, side view.
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Figure 17c. Hilsen, top view (disarticulated).
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Tongue Advancers
* Off-the-shelf -- Snore X (Figures 18a, b, and c).
Figure 18a. Snore X, front view.
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Figure 18b. Snore X, side view.
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Figure 18c. Snore X, inferior view.
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* Lab-fabricated -- Tongue Retainer Device (Figures 19a and b).
Figure 19a. Tongue Retaining Device, front view. |
Figure 19b. Tongue Retaining Device, side view.
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Description of Categories
Mandibular Advancers
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In most cases, these devices are secured in the mouth by being teeth-borne to the upper teeth. Most also attach snugly to the lower teeth; however, three of the boil-and-bite types do not secure snugly to the lower teeth but rely instead on an inclined plane behind the lower anterior alveolar process to hold the mandible forward (Figure 20). The amount of forward repositioning varies with the appliance and the clinician. Also, the amount of vertical opening of the mandible varies with the appliance. The rationale behind these appliances is that since the tongue attaches to the back of the mandibular symphysis, moving the mandible forward also pulls the tongue forward, thereby moving the backside of the tongue away from the posterior wall of the throat (Figure 21). Further, because the palatoglossus muscle attaches from the side of the tongue to the soft palate, pulling the mandible and tongue forward also pulls the soft palate forward, separating it from the back of the throat (Figure 22).
Figure 21. Anatomy of tongue and throat.
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Figure 22. Palatoglossus muscle.
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The mandibular advancers may be made of elastomer material or hard acrylic, or thermoplastic. They may create their retention on the teeth by friction fit of plastic in undercuts, which is most common, or by clasps.
They may use many different mechanisms to create and adjust the mandibular advancement, and the amount of advancement varies from a little to more than the patient can actively produce, depending on the patient's severity of snoring and ability to tolerate jaw joint stretch. Frequently an advancement begins at about 70 percent of a patient's maximum active protrusive ability.
Tongue Advancers
These devices are secured in the mouth by forming a suction on the tip of the tongue via a suction bulb that is braced against either the teeth or the lips. The size of the suction bulb is selected by measuring the thickness and width of the anterior quarter of the tongue when protruded past the teeth.
The rationale for these appliances is similar to the mandibular advancers in that the tongue and soft palate are advanced away from the back wall of the throat. These tongue advancers can be used when the jaw joints do not tolerate stretching or when there are insufficient teeth to support a mandibular advancer. These devices tend to take longer to become accustomed to than mandibular advancers.
Criteria of Evaluation of Oral Appliances
Substantial experience in treating patients with oral snore devices and comparison of the features of more than 20 devices were used to develop a set of criteria to help dentists in selecting an appliance.
Those criteria are presented here for both the experienced and novice snore clinician to consider.
Reliability at Stopping Snoring
This is the most important criteria. If it is not met, the patient is not satisfied, the dentist has wasted his or her time and lost the patient's confidence, and the profession has lost credibility in the eyes of medicine. Medicine has additional criteria, which include reduction of obstructive sleep apnea, reduced oxygen desaturation, and decrease in daytime sleepiness; but these were not evaluated in the present study. A dentist must keep in mind that these medical criteria must be considered in the care of some patients, in addition to the criteria discussed in this paper. The evaluation of the medical criteria are discussed elsewhere.9,10
In general, the adjustable two-piece mandibular advancers are most reliable. They can be adjusted easily to increase the mandibular advancement until airway patency is sufficient.
Many of the one-piece lab-fabricated mandibular advancers are reliable, because even if the bite needs further advancing, they are easily cut apart and luted back together. An exception to this is the Elastomeric device, which is not easily cut apart nor re-luted.
Titratability
This term describes the easy ability to fine-tune the amount of mandibular advancement to keep the airway open without excessively stretching the temporomandibular joint. This criterion has some similarity with the first criterion of reliability, but this criterion specifically monitors the ease and the gradiency of adjustments. A high score here means fewer remakes and easier delivery.
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None of the one-piece mandibular advancers, nor the tongue advancers, are easily titratable. Some clinicians may point out that the boil-and-bite devices could be reheated and advanced, but with the exception of the two-piece Thera Snore, this is not particularly easy.
Simplicity of Delivery
To be considered simple to deliver in this study, an appliance should not require more than 30 minutes of chairtime, including initial impressions, whether delivered at the first appointment, such as boil-and-bite devices or Snore X, or at the second appointment, like the other devices.
For most of the one-appointment deliveries, the boil-and-bite devices require a source of very hot water and considerable trimming and polishing of the soft material once molded. The simplicity of the single appointment delivery is offset by the amount of chairtime fitting and adjusting of the appliance, compared to the ease of trying in a completed lab-fabricated appliance at a second appointment.
Most of the commercially available devices scored highly in simplicity of delivery; and, as the practitioner gains experience, even those that might not be easy for a novice to deliver would become fairly easy.
Low Bulk
The absence of bulk makes an appliance more comfortable and therefore more likely to be worn. The feeling of excess bulk can be from the size of the appliance, the extent of its flanges, or the protuberance of its working parts. The perception of bulkiness may be experienced in the lips, cheeks, or tongue. This criterion is more subjective than the first ones and depends on variations in individual appliances as well as tolerance from the individuals wearing them. Others evaluating similar appliances might report different findings than presented here.
The low-bulk appliances are evenly divided among the one-piece and two-piece mandibular advancers.
Lip Seal
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Tongue Space
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Non-interference With Sleep
Some devices can be worn and easily accommodated, without initially disturbing sleep. This criterion is similar to the low-bulk criterion but sufficiently different to warrant being a distinct criterion. These findings are very subjective and not necessarily generalizable to a large population; but some appliances, by their presence, cause many awakenings during the night and tended either to be bulky or to violate lip seal or tongue space. Most of these problems could be overcome by repetitive nights of wearing, but the investigation was intended to discover which appliances were easy to adapt to.
Temporomandibular Joint or Tongue Symptoms Easily Adjusted
This criterion is similar to the reliability of stopping snoring criterion and to the titratability criterion. If the TMJ gets sore from being stretched, the appliance needs to be easily adjustable and adjustable unilaterally if necessary.
The developer of the TAP appliance states that unilateral adjustability of TMJ stretch has not been necessary in more than 1,000 cases treated, provided that posterior occlusion is not allowed on the appliance. However in the author's experience, in some cases the ability to adjust the bite did help the TMJ.
The two tongue advancing devices, since they do not stretch the mandible, are exempt from the TMJ criterion, as TMJ symptoms would not be expected from these two devices. However, these two devices can cause soreness to the tongue tip due to the suction, and this can also cause difficulty in accommodation.
Low Cost
Low purchase price is also a factor that influences a practitioner's thinking. Appliance cost varies from $60 to $500. Most fall between $100 and $200. If an appliance costs less than $100, it was arbitrarily considered low-cost. The cost of chairtime to deliver these appliances should also be considered, and that is discussed under simplicity of delivery.
Lateral Freedom
A frequently mentioned criterion, but a poorly studied one, perhaps less necessary than commonly believed, is lateral freedom. It is argued that bruxers need lateral freedom. The author has provided lateral freedom to many patients but found they were happier when the appliance was converted to a one-piece by luting the two splints together. This property needs to be considered for some patients but probably not most.
Weighting of Criteria
The criteria discussed above are not all of equal value or importance. It is probable they are of decreasing importance in the order they were discussed, but this opinion could vary for some patients and for other clinicians. The weighting of the criteria might be as shown in Table 1.
Other criteria that were not studied but which might deserve consideration include reliability at stopping obstructive sleep apnea, durability, and avoidance of bite changes or teeth movement.
Circumstances can change the hierarchy of criteria. An edentulous patient would probably need a TRD. A TMJ patient might move criterion 8 higher on the list. A bruxer might move No. 10 higher. If the doctor wants to try a patient's tolerance to a type of device without great expense, criterion 9 might move higher. If a dentist wants to advance the mandible extremely far, as in a severe obstructive sleep apnea case, then reliable retention to the teeth and absence of TMJ symptoms would both be the most important goals, and the TAP appliance would be more likely to be considered.
Table 1.
Weighting of Criteria.
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Evaluation of Appliances
Nearly all the vendors of the appliances included in this study provided an appliance at no charge in order to facilitate this study. This study is a report of the author's evaluation of each appliance on himself. The author was considerably experienced in treating snoring, with experience in using several devices prior to this study.
Those who object to these findings on the basis that it is not a randomized clinical trial of sufficient magnitude are welcome to perform such a study, but in the meantime these findings are offered.
Also, these findings may be disputed by some clinicians who prefer to use devices not highly rated here. In some cases (TRD, Snore Guard, TAP, Klearway, Mandibular Repositioner, Silencer, TheraSnore, EMA), there is data and published literature elsewhere showing efficacy of appliances not highly rated here.11-18 It is to be hoped that interested individuals will use this evaluation to choose from among the better appliances and provide even better treatment to more patients in order to continue improving dentists' confidence and medicine's respect.
Table 2 lists the appliances along with their evaluations.
The Hilsen appliance was extremely easy to deliver and very comfortable and effective. The edge of the Velcro was bothersome to the tongue until it was trimmed with an acrylic bur.
The SML Herbst was well-designed. The buccal hooks and Herbst axle positions were carefully chosen to be maximally comfortable to the lips. It lacked posterior bite blocks, so the vertical dimension was small. Its retention and advanceability probably would make it good for obstructive sleep apnea.
The EMA appliance had great lateral freedom. The rubber straps came off too easily. They are interchangeable with straps of different length and tension.
The Silent Nite appliance also had excellent lateral freedom. It was of very low bulk but probably had insufficient tooth retention for severe mandibular advancement in obstructive sleep apnea cases. The spare nylon straps could probably be more useful if shorter ones were available (the lab only provides one shorter replacement pair than the pair they install, and this only allows one protrusive adjustment). The absence of posterior bite blocks makes this appliance unsuitable for bruxers.
The PM Positioner was comparatively bulky and extremely tight-fitting on the teeth initially. It would probably be a good choice for obstructive sleep apnea cases requiring firm retention during greater mandibular advancement.
The MIRS appliance was of low bulk and pleasant to wear. Its mandibular ramp seemed unnecessary because the mandible was held forward by friction fit on the lower teeth.
The GLO Herbst had an unnecessary transpalatal arch and uncomfortable position of the hooks and axles but was a good appliance, with sufficient retention and advanceability to probably be good for obstructive sleep apnea.
The Specialty Herbst was effective but had its hooks and axles in uncomfortable positions. It also would probably be effective for obstructive sleep apnea.
The Mandibular Repositioner was an excellent appliance, but because it is one-piece, it requires great accuracy with the wax bite and lab procedure. It was quite comfortable. It was made with clasps that were probably unnecessary because of the tightness of the acrylic.
The Silencer required fairly complex procedures at the impression appointment and was by far the most expensive. It was a very well-made appliance.
The Klearway was comfortable on the teeth with good lateral freedom, but the transpalatal advancement screw was quite bothersome to the tongue.
The Thera Snore had no firm retention on the lower teeth but relied on a lingual ramp to nudge the mandible forward. This was quite uncomfortable and ineffective compared to other devices.
The TAP fit the teeth extremely well and was capable of great advanceability and retention, probably making it good for obstructive sleep apnea. Its lingual hook mechanism was bothersome to the tongue, and its titration knob protruded out the lips.
The Restore fit the teeth very well and would probably be good for obstructive sleep apnea. Its anterior hook mechanism sometimes pinched the lips.
The Snore Free was soft and comfortable but also had a lingual ramp instead of lower teeth retention and was therefore less effective at holding the mandible forward. Its price is low.
The NAPA was quite similar to the Mandibular Repositioner, except that it had a beak-like flat tube protruding through the lips. The beak seemed unnecessary.
The Elastomeric appliance could have benefited from a larger air hole (which the tongue could protrude into). It was comfortable and effective but very difficult to grind, which was necessary because the flanges rubbed the gums.
The TRD was comfortable but much more difficult to get used to than the mandibular advancers.
The Snore Guard seemed too small to be effective and relied on a lingual ramp to hold the mandible forward, instead of retention on the lower teeth.
The Snore X was simple to wear but produced a very sore tongue tip the next day.
The SNOAR appliance was made at a very large vertical opening, making lip seal impossible and making the appliance difficult to wear.
Discussion
The criteria for evaluating oral devices presented in this paper do not include efficacy in reducing obstructive sleep apnea or daytime sleepiness, and certainly the field of medicine would be interested in such results if available. This paper focuses more on snoring.
The criteria for selection presented here also do not include durability of the appliances, primarily because durability has not been studied yet. However, the following comments reflect the author's experience.
To keep the appliances closed, the Herbst appliances need vertical elastics that must be changed occasionally. The vendors did not supply elastics. Nor did the Herbst vendors supply advancing shims unless requested. The EMA appliance needs its elastic straps changed occasionally (frequency unknown). The Hilsen seems to fit more loosely over time, and the Velcro strips seem to partly tear loose but they are secured with monofilament thread. The PM Positioner is somewhat subject to breakage where the jackscrews are attached to the splints, especially if the appliance is removed improperly. Silent Nite splints are somewhat thin and have a history of some breakage, which may be resolved by now. The Silent Nite nylon straps are also thicker than they were previously, and they are now adjustable by the dentist in that straps of different lengths are provided along with instructions on how to change them. Also, the Silent Nite can be made of different (thicker and softer) material if the doctor notifies the lab that the patient is a bruxer. The Restore jackscrew broke off once when the appliance was assembled incorrectly but it was easily repaired with self-cure acrylic. The NAPA sometimes produced a whistling sound through its beak. The TAP is very much improved and simpler to deliver.
Another factor that has not been studied here is the tendency for appliances to move teeth or to change the bite permanently. It has been suggested at Sleep Disorders Dental Society meetings that the thermoplastic appliances may be more likely to move teeth than their rigid plastic cousins. It has also been said that shallow bites or open bites are more likely to change from wearing these devices than deep bites.
There is a wide range of behavior of the thermoplastics used in these devices, from the very soft boil-and-bite devices to the medium-soft acrylic in the Hilsen, to the very firm material in the PM Positioner. Devices using thermoplastic include PM Positioner, Hilsen, Silencer, Klearway, Thera Snore, Restore, Snore Free, TAP, and Snore Guard.
There have been people who have advocated using the less expensive devices as trial devices to see if the patient can tolerate a dental appliance, and then replacing the trial device with a more permanent long-term device. For example, it is often suggested that a Snore Free be used to see if a patient can tolerate and benefit from mandibular advancement. Also, the Snore X was developed to see if a patient can tolerate and benefit from a tongue advancing device. In reviewing the table of ratings, one can re-evaluate those suggestions. The Snore Free appliance is so inferior to the best mandibular advancers, particularly in reliability at stopping snoring and in not disturbing sleep, that a patient who did not do well with the Snore Free still might do fine with a better appliance, and the trial appliance therefore served no purpose.
However, in the case of the Snore X, which is a trial device preceding a TRD, the ratings are so close that there is no reason not to do the Snore X first. If a person could not tolerate nor benefit from a Snore X, there is some likelihood that that might be true of a TRD too.
Table 3 is a list of snore appliance vendors. There are probably additional vendors for the Herbst, Mandibular Repositioner, and PM Positioner, but this is a listing of vendors who were kind enough to provide appliances to be studied. No deliberate exclusion of other vendors was intended.
Author
James E. Eckhart, DDS, is an orthodontist who also treats TMJ and snoring.
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To request a printed copy of this article, please contact/James E. Eckhart, DDS, 321-12th St.
Manhattan Beach, CA 90266.
