Multilevel Oral Appliance Treatment for Sleep Apnea

SUMMARY

Obstructive sleep apnea (OSA) occurs when people repeatedly choke on their tongues and surrounding soft tissues during sleep.  It affects millions of people, but current treatment for it is problemmatic.  Surgery is only predictably effective if it is performed at multiple levels of the pharynx, because most people with OSA have multiple sites of obstruction at different levels of the pharynx.  CPAP is usually effective because it balloons out all levels of the pharynx and makes it too large to obstruct, but compliance is poor. Oral appliances that protrude the mandible make room for the tongue to shift anteriorly, but they can't actually shift the tongue anteriorly, so their effectiveness is never more than about 50%. An oral appliance that uses a rubber suction bulb to grasp the body of the tongue and hold it out between the lips directly shifts the tongue anteriorly, but it still can't prevent the soft palate from getting sucked down and back into the space between the tongue rear and the posterior wall of the upper (retropalatal) pharynx.  An oral appliance which holds down the tongue rear increases the space which must be filled in between the tongue rear and the posterior wall of the pharynx to obstruct the airway, but it still can't prevent the distal end of the soft palate from following the tongue rear down and obstructing airway passage a little further inferiorly.  Soft palate elevators make it more difficult for the soft palate to get sucked in between the rear portion of the tongue and the back wall of the upper pharynx, but are rarely effective when used alone.  

These diverse oral appliance modalities, which all have some effectiveness, are synergistic in many ways, but they have never been combined, because the hardware they require has previously been incompatible.  A new tongue holding device (THD), which is made of dental acrylic, enables combining all these treatment modalities in a single oral appliance.  The modalities are added one at a time followed by home sleep testing to ensure that the patients receive only the modalities they need.  Such multi-level treatment is likely to be the key to predictable success with oral appliances for OSA, just as multi-level treatment has proved the key to predictable success with surgery for OSA.   

PATHOPHYSIOLOGY OF SLEEP APNEA

Obstructive Sleep Apnea (OSA) is a process of repeatedly choking on the tongue during sleep.  Surrounding soft tissues such as the distal end of the soft palate and the peri-tonsillar tissues can play a role by filling in around the tongue to help create a seal, but the tongue is the only object in the area large enough to obstruct the airway.  When it gets sucked back into the pharynx during an inspiration, it can create a plug that prevents all airflow until the resultant decrease of oxygen levels and increase of carbon dioxide levels trigger an adrenalin release that causes a gasp that relieves the blockage and temporarily restores the airway. In millions of people, these recurrent intermittent airway obstructions last long enough and occur frequently enough to become a serious health problem.

Studies using imaging to locate the obstruction have found it too variable to provide a basis for targeted treatment.  It occurs most frequently in the upper pharynx (velopharynx or retro-palatal pharynx) where the soft palate and adjacent soft tissues get sucked into the space between the dorsum of the rear portion of the tongue and the rear pharyngeal wall. It occurs slightly less frequently in the lower pharynx (retro-glossal pharynx or oropharynx) where the dorsum of the rear portion of the tongue directly contacts the rear pharyngeal wall. In people with moderate or severe OSA, the obstruction usually occurs in both areas, and it frequently extends down to the hypopharynx behind the tongue base. One study found multiple sites of obstruction in 72% of the subjects. Another reported seesawing obstructions and varying obstructions within the same individual. Apparently pharyngeal airway collapse in OSA is rarely the result of one clearly identifiable obstruction. 

MEDICAL TREATMENT

CPAP (continuous positive airway pressure) keeps the whole pharynx ballooned out and therefore makes it too large to get plugged by the body of the tongue at any level.  CPAP is almost always effective if the pressure is high enough. However long term compliance is poor. Nearly half of those who have been prescribed CPAP do not use it on a regular basis. 

Surgery for OSA is not predictably effective unless it is performed at multiple levels of the pharynx (multi-level surgery), such as combining maxillary and mandibular advancement with UPPP.  However compounding surgeries also compounds costs and morbidities, therefore surgical remedies remain problemmatic.

ORAL APPLIANCE TREATMENT

Oral appliance treatment for OSA also has not been predictably effective as a single level therapy. The vast majority of the oral appliances made by dentists to treat OSA use only mandibular protrusion. Because the mandible surrounds the airway in front and on both sides, protruding it creates a space for the tongue to rest more anteriorly. However, the mandible and the tongue are only attached by muscles, which lose tonus during sleep. Thus even extreme mandibular protrusion cannot always prevent the tongue from falling back and obstructing the pharynx - it just has further to fall.  For that reason, the hundreds of studies of mandibular protrusion that have been performed in the last two decades all show that the treatment is never effective in more than about half of OSA patients.  Some studies defining success as a 50% reduction in AHI show a slightly higher success rate, but almost all of those "successes" will still need further treatment as the tissues continue to stretch out due to age and continued apnea events. 

Three very similar devices, (the tongue retaining device (TRD), the Avea tongue stabilizing device (TSD), and the MPowRX) use a silicone rubber suction bulb to grasp the tongue and hold it out between the lips.  These devices were introduced in the 1980's, and they are often employed when the patient's dentition is compromised and may not be able to tolerate the pressure required to protrude the mandible significantly.  However the extreme increase in vertical dimension required to hold a balled up tongue between the anterior teeth is difficult to tolerate. In the only prospective study of one of these devices (the TRD), 60% of the patients dropped out because of tongue pain. In addition, these devices can increase the severity and frequency of blockage in the lower pharynx by pulling a larger portion of the tongue up into the area of obstruction. In one study, a TSD caused large increases in the AHI of two of the subjects.

A tongue rear depressing appliance has also shown some success in protecting the upper pharynx. The Full Breath Solution (FBS) appliance employs a rigid transpalatal bar to support a smooth tail-like bulb that holds down the rear portion of the tongue.  Holding down the rear portion of the tongue probably helps prevent obstruction in the upper pharynx, but it cannot prevent the soft palate from following the rear portion of the tongue down and recreatin the obstruction at a slightly inferior location. 

Soft palate elevators can help prevent the distal end of the soft palate from following the tongue rear inferiorly.  They contact the soft palate in its midportion, where there are no gag reflexes.  Pushing the very mobile tissue there superiorly has the effect of tenting the whole soft palate and thereby drawing its distal end anteriorly and superiorly away from the obstruction.   Soft palate elevators have been sometimes effective for snoring, but rarely for OSA.  

COMBINATION TREATMENT

Combining all these oral appliance treatment modalities offers obvious advantages in both comfort and effectiveness, because their actions are highly synergistic. The mandible provides the base of operation for the tongue (which has no bone of its own), therefore mandibular protrusion and tongue protrusion are mutually supporting modalities.  Mandibular protrusion facilitates mechanics that push down and forward on the tongue rear by creating space into which the body of the tongue can shift in that direction.  Depressing the rear portion of the tongue to prevent it from contacting the distal end of the soft palate opens the upper pharyngeal airway more effectively if used together with a force drawing the distal end of the soft palate superiorly. 

However previously it has not been possible to combine these oral appliance treatment modalities, because the hardware required for each of them has been incompatible.  For example, the silicone rubber used by the TRD is difficult to attach to the acrylic used in mandibular protrusion appliances.

We have developed a new tongue holding device (THD) that enables combining all these treatment modalities to create the first multi-level oral appliance.  The THD is is entirely made of dental acrylic so it can be added to a variety of oral appliances.  The other modalities can then be added one at a time only if they are needed as determined by multiple night home sleep testing after the addition of each modality.  

TELESCOPIC MANDIBULAR PROTRUSION

We normally begin treatment with a telescopic mandibular protrusion appliance that has been modified for use in adults. Telescopic appliances have long proven effective in treatment for OSA, but the telescopic hardware in the commonly used Herbst and SUAD appliances was designed more than half a century ago for orthodontic bite jumping in children.  When used in adults, it is unnecessarily bulky, and it can impair TMJ health by preventing lateral mandibular movements.  We have flattened the telescopic components to better fit the buccal vestibule, we attach them flexibly in order to allow a free range of motion laterally for TMJ health, and we make them micro-adjustable by the patient over a range of ½” without tools. The ability of patients to easily adjust the length of each telescopic assembly allows them to titrate mandibular position gradually and to immediately “walk back” one or both sides if TMJ disorder symptoms or dental problems arise during titration.

 

There are also a number of other jaw protrusion appliances that can be used as the base for multi-level treatment.  For example, Somnomed, EMA, and Herbst appliances can be used.  Monoblocs, which some dentists are making to reduce their costs, cannot be used.  

After titrating the jaw protrusion, we use a home sleep test to evaluate the effectiveness of the appliance.  We use five nights of consecutive testing, because normal internight variability of testing results is about 15%, and people rarely sleep normally the first night or two when wearing any new oral appliance.

THE TONGUE HOLDING DEVICE (THD)

If the OSA persists after titration of the mandibular protrusion appliance, we add a tongue holding device (THD), which holds the tongue forward with the mandible.  The tongue is held between upper and lower tongue gripping surfaces, each containing thousands of miniature forward-slanted bristles that act like directional velcro. The 4,000 bristles on the upper tongue gripping surface (shown below) are sized to fit between the filiform papillae that cover the dorsal surface of the front of the tongue. The 11,000 miniature bristles on the lower tongue gripping surface engage the more sensitive unkeratinized mucous membrane on the underside of the tongue like a bed of nails.  Because of the 45 degree angle of the bristles, the tongue can easily slide forward into the space between upper and lower tongue gripping surfaces, but it cannot be pulled backward out of that space (shown below right) without opening the mouth widely enough to release the tongue.

 

With the tongue fixed to the mandible, the mechanics that protrude the mandible also protrude the body of the tongue, as pictured below.

new thd illustration.jpg 

The resilient mounting of the upper tongue gripping surface enables it to maintain its grip on the tongue throughout the night despite the rhythmic masticatory muscle activity (RMMA) that occurs during normal sleep.  The constant bias of the upper tongue gripping surface into the tongue is produced by a trans-palatal orthodontic elastic (dashed lines) as shown in the top figure.  The bias continues until the mouth opens wide enough to bring the middle of the elastic into the same plane as the ends of the elastic as shown in the middle figure. Any further opening separates the tongue from the tongue gripping surfaces as shown in the bottom figure.  In this manner, wide opening serves as the tongue release mechanism.  If the THD fits correctly, the user cannot remove the tongue without opening the mouth widely. 

RESILIENT SUSPENSION OF TONGUE GRIPPING SURFACES

A preliminary study of the THD conducted for the FDA with before and after full night PSG on 13 subjects showed that the THD used as a single modality was safe and about as effective as other oral appliance modalities.

TREATMENT OF THE UPPER PHARYNX

If follow-up home sleep testing still shows OSA, the remaining airway blockage occurs where the distal end of the soft palate gets sucked into the space between the dorsal surface of the tongue rear and the back wall of the upper pharynx, as illustrated below.

trd_2.jpg

To relieve this blockage, we employ two additional modalities that move the tissues bordering the upper pharynx in opposite directions.  Holding the tongue rear inferiorly and anteriorly while drawing the distal end of the soft palate superiorly and anteriorly maintains airway passage between them, as illustrated below. 

trd_1.jpgThe tongue rear is held downward and forward by a sturdy arm that extends distally from the back of the hard palate to push downward and forward on the rear portion of the tongue.  The arm terminates in two hemispheres that maintain an airway passage between them.  It depresses the tongue rear much like the FBS appliance does, but it also has an anterior component of force that helps keep the tongue from contacting the posterior pharyngeal wall.  The arm has enough flexibility to allow normal tongue movement during swallowing.  

At the same time, the distal end of the soft palate is drawn superiorly and anteriorly by a more delicate arm that tents the soft palate by elevating its central area, where there are no gag reflexes. The very flexible tissue of the soft palate can be elevated surprisingly far without discomfort.  The distal end of the soft palate moves only a fraction of that distance, but any movement of that critical structure in the right direction can be very helpful.

MOUTHBREATHING

Mouthbreathers are obligate or habitual.  Obligate mouthbreathers have a nasal airway that is too small to allow adequate airway flow, and their lips are always slightly parted to allow an oral airway. Habitual mouthbreathers have developed a habit of holding the mouth open and breathing through it in spite of an adequate nasal airway passage.  Many people are occasional mouthbreathers due to rhinitis or allergies.  The THD permits mouthbreathing, because its upper tongue gripping surface descends with the mandible when the mouth is part way open and thereby creates an oral airway passage just under the hard palate.

For habitual mouthbreathers, any dual arch appliance can include buttons for attaching interarch elastics that prevent the mandible from dropping open during sleep.  In such cases, the upper and lower bases must be made to fit more tightly on the teeth than the force from gravity pulling the mandible inferiorly. 

Some obligate mouthbreathers can be converted to nasal breathers by expanding the palate.  The process can be performed gradually in adults without significant discomfort, and a change from oral to nasal breathing yields major health benefits.  However any effect of palatal expansion on OSA in adults is likely to be minimal, because the airway obstruction in OSA occurs in the pharynx, not in the nasal cavity.1 

OCCLUSAL DISRUPTION

One common sequelae of jaw protrusion is an inability to return to the patient's normal habitual occlusion in the morning.  Some dentists prescribe a series of exercises to force the mandible back retrusively every morning, because they don't understand that the patient's mandible has outgrown the occlusion.  Exercises that force the mandible posteriorly may be able to trigger remodeling that enables the joints to accept a more posterior condylar position, but the mandibular growth cannot just be reversed.  The occlusion needs to be adjusted to fit the slightly more anterior position of the mandibular corpus.

COSTS OF MULTILEVEL TREATMENT

Normally the full cost of the treatment protocol, $3800, includes all modalities that are necessary as well as home sleep testing after each modality is added.  However, during 2017, while we are collecting data for a study, we will offer the treatment protocol for $1900 to anyone who is willing to carefully follow the study protocol, including the 5 nights of home sleep testing.   

 1.Ribero AN, de Paiva JB, Rino-Neto J, Illiponti-Filho E, et al. Upper airway expansion after rapid maxillary expansion evaluated with cone beam computed tomography. Angle Orthod 2012;82(3):458-463.