|
Oral Appliances.
Currently there
are in excess of 200 different types of appliances available.
Universally they all have similar effect of repositioning and
holding the mandibular (lower jaw) in a protruded position during
sleep. This concept was first published and reported back in the
early 1980's ( Pancherez et al , Clarke et al, Halstrom et al,
Lowe et al ). Earlier patents and published evidence
confirmed the efficacy of this.
By holding the
lower jaw forward tends to also bring the tongue forward and exert
tension on the muscles of the tongue making it more rigid and less
floppy overcoming obstruction of the throat.
Of these 200
appliances they tend to fall into 5 categories, defined by their
individual design application.
The real
question is which is best for each patient and which have medical
evidence to support their claims.
Unfortunately as
most research studies define the appliance used in the generic of
MAS or MAD all appliances tend to reference any study published as
applicable to their product.
Why? It’s essential to
select the right oral appliance for each patient to ensure
compliance and improved patient outcomes.
Studies have
shown that changes occur in the upper airway at several levels when
the mandible is pulled forward.
A study by Isono et al (1)
used video endoscopy to examine the effects of advancing the
mandible on the pharyngeal airway of 13 patients with OSA who were
under general anesthesia with total muscle paralysis. They found
that advancing the mandible widened the retropalatal airway as well
as that at the base of the tongue. They applied negative pressures
to the airway and showed that a more negative pressure was required
to cause collapse of the airway when the mandible has been
advanced. In their discussion, they postulated that one of the
mechanisms by which mandibular advancement stabilizes the soft
palate and retropalatal airway is through tension transmitted along
the palatoglossus muscles to the soft palate.
A study by Schwab et al (2)
using MRI on snorers while they were awake showed that advancing
the mandible resulted in a greater increase in the lateral than the
A-P dimension of the airway. CPAP produces a similar change
(3).
Wearing an appliance will
also prevent the mouth from falling open during sleep. A study by
Meurice et al (4) showed that upper airway collapsibility was
increased in normal subjects while awake when their mouths were
opened.
Therefore, wearing a dental
appliance that advances the mandible stabilizes the upper airway
by:
1. pulling the base of the
tongue forward,
2. pulling
the soft palate forward and putting the walls of the upper airway
under tension
3. keeping the
mouth from falling open during sleep.
These are
primarily passive mechanical effects that can be explained by
applying simple physical principles to what is known about the
anatomy of the upper airway.
The critical anatomic
relationships in terms of improving the sleeping airway with
mandibular advancement are as follows:
It is important to keep the
mouth closed. If the mouth is opened more than 10mm
tensile forces that are produced by advancing the mandible are
directed partly downwards towards the feet. This increases the
longitudinal tension in the pharynx and promotes
collapse.
However, there
are situations in which combining advancement of the mandible with
a slight increase in the opening of the jaw will help to further
stabilize the soft palate without promoting collapse of other
portions of the upper airway.
It is tension that stabilises
the structures in the upper airway. When you are awake, upper
airway muscles are activated to produce this tension.
When you are asleep, these
muscles become less active and tension is lost.
CPAP restores this tension by
applying an intraluminal pressure. When the anatomy is favorable,
mandibular advancement can be as effective as CPAP in tensing and
stabilizing the structures of the upper airway.
Study by Oshima et al (5) demonstrates that mandibular
advancement in properly selected patients with OSA results in a
decrease in genioglossal EMG activity during sleep as has been
observed in patients with OSA who use CPAP (6).
CPAP applies pressure to the
inside of the upper airway that stretches the tissues and prevents
their collapse.
This pressure also acts as a
counter-pressure to the pressure exerted by the tissues surrounding
the upper airway. Advancing the mandible decompresses these same
tissues. Either way, the net pressure in the tissues surrounding
the upper airway is lowered resulting in widening of the upper
airway.
CPAP accomplishes these goals by applying pressure to the
inside of the upper airway.
When the anatomy is favorable,
mandibular advancement with a dental appliance can achieve the same
goals.
References
1.Isono S,
Tanaka A, Sho Y, Konn A, Nishino T: Advancement of the Mandible
Improves Velopharyngeal Airway Patency. J Appl Physiol 1995;
79:2132-2138
2.Schwab RJ, Gupta KB,
Duong D, Schmidt-Nowara WW, Pack AI, Gefter WB: Upper Airway Soft
Tissue Structural Changes with Dental Appliances in Apneics. Am J
Respir Crit Care Med 1996; 153 (part 2 of 2 parts):
A719
3.Schwab RJ, Pack AI,
Gupta KB, Metzger LJ, Oh E, Getsy JE, Hoffman EA, Gefter WB: Upper
Airway and Soft Tissue Structural Changes Induced by CPAP in Normal
Subjects. Am J Respir Crit Care Med 1996;
154:1106-1116
4.Meurice J, Marc I,
Carrier G, Series F: Effects of Mouth Opening on Upper Airway
Collapsibility in Normal Sleeping Subjects. Am J Respir Crit Care
Med 1996; 153:255-259
5.Oshima T, Tsai WH,
Hadjuk EA, Remmers JE: Mandibular Protrusion Decreases Genioglossal
EMG. Am J Crit Care Med 1998; 157(3):A655
6.Strohl KP, Redline S:
Nasal CPAP Therapy, Upper Airway Muscle Activation and Obstructive
Sleep Apnea. Am Rev Resp Dis 1986; 134:555-558
(1) Tongue
retainer.
There are not many available, however they
have been well researched and shown to be effective in selective
patients. Patient compliance and acceptance is a problem for long
term use. Useful for patients with limited or no
teeth.
(2) MonoBlocks or
Fixed Devices.
These are by far the most common available.
Can be useful as a trial splint or where economics dictate what a
patient should have.
However TMJ problem's are universally
reported with them because they lock the jaw and mouth into a fixed
position. Total disaster for bruxers.
They offer no adjustment, therefore they
have to be remade if further protrusion is needed (which is common
after a patient has worn a splint for a few months). The common
complaint is "it worked ok at the start but I have started to
snore again".
While they are cheap, the complications from
side effects and costs associated with having to remake, make it
expensive therapy.
Tend now only to be sold by mail order or
advertised over the air or in papers. Not used often by Dental
Sleep Dentists.
(3) Flimsy Trial
Splints.
There are not
many of these available. Traditionally made from all plastic with
plastic side hinges. Can be useful as a trial splint.
Most supply with
a repair kit to replace hinges when they break. The real question
is if they break when wearing them which is while you are asleep
where do the broken bits go?
(4) Adjustable
Mandibular Repositioning Appliances.
These are by far the largest group and the
first of the adjustable, based on traditional orthodontic
principals, devices or components.
They have a variety of different
configurations but all have the one major problem, lack of lateral
movement.
Those that have metal hinges on the side
have been reported to caused teeth movement and
eruptions.
Often to make further adjustments during
treatment can be very difficult and complicated leading to extended
periods to acclimatize patients with this type of
device.
This was reported in a study using this
style of appliance published in the Am.J, respir.crit.care med
Volume 163, number 6, May 2001.(page 6 - results-study
population)
A Randomized, Controlled Study of a
Mandibular Advancement Splint for Obstructive Sleep Apnea. by MEHTA
et al AJRCCM Vol 163 2001.....The mean acclimatization period (wash
in period) was 19.7± 8.8 weeks ( range, 5 to 40 wks
)...
Oral appliance
Therapy Improves Symptoms in OSA by Helen Gotsopoulos etal
AJRCCM Vol 166 2002 ...The acclimatization to the MAS was 8±4
wks ( range, 2-22wks )
They are also very expensive to make and
tend to be made only by large commercial orthodontic
labs.
 
 
 
One of these " Somnomed " makes claims
that it has the advantage that patients can talk and drink and also
fully open their mouths?.
(5) Titratable Mandibular
Repositioning Appliances.
(A) The first of these was
the TAP which allowed full lateral movement and titration while in
situ.
The downside of the appliance
is
(a) Only made by commercial
labs
(b) uses a combined acrylic plate with boil
and bite filler for retention. Filler breaks down and not very
durable.
Very rigid and hard on teeth causing tooth
soreness and ache
(c) Large lingual bar in the bottom plate
impedes the tongue coming forward.
(d) an external winder has to be used till
the right advancement is obtained (can be for some weeks) once the
winder is cut off no post adjustment can be
obtained.
 
(B) The MDSA® Component concept
Appliance.
The most versatile and clinically proven to be
an effective alternative to CPAP for the treatment of Snoring and
Mild to Moderate Sleep Apnea.
Efficacy of Positive Airways Pressure and
Oral Appliance in Mild to Moderate Obstructive Sleep Apnea. M
Barnes et al. Am Jnl Resp Cr C M June 2004.
...In the wash-in period it was advanced
weekly by the study dentist as tolerated by subjects, until the
maximum comfortable protrusion was reached, taking up to 3
weeks.
Clinically tested
to overcome the problems, limitations and side effects associated
with all other oral appliances.
For
full details on the MDSA® refer to opening page of website.
| 