From NTI: http://www.nti-tss.com/analysis.htm

I.  Danger of Aspiration and Swallowing
of Dental Foreign Objects

Introduction
As with all dental devices and materials, swallowing and aspiration of
dental foreign objects is a great concern to both the manufacturer and the
clinician.  Swallowing is far more common than aspiration, and neither are
highly reported in the medical literature.  Trauma is the most common cause
of aspiration or swallowing of  fractured or avulsed teeth, and dislodged
fixed and unilateral removable prostheses.

There are no reports in the literature of aspiration or swallowing of dental
devices during sleep.  This includes removable anterior jig appliances
sometimes used as muscle deprogramming devices or specific orthodontic
removable appliances.

Specifically considering the NTItss appliance, it is imperative that the
mean average pressure to dislodge the appliance from the maxillary anterior
teeth be known.  The maximum tongue-tip pressure against the maxillary
lingual surfaces of the anterior teeth in the human being has not been
reported.  However, several studies, have reported tongue tip pressure in
adults during swallowing as 68 gm/cm2 (+/-14 gm/cm2) to 445 gm/cm2 (+/- 220
gm/cm2).

The geometric shapes of the maxillary anterior teeth most important in the
retention of an appliance such as the NTItss.  To dislodge the NTItss, both
horizontal and vertical tongue pressure is required.  In theory, if the
vertical force required to dislodge the appliance is consistently greater
than the maximum tongue-tip pressure against the appliance, then the
clinician may confidently, with certainty, place the NTItss appliance.
Experiment

To test this theory, 12 patients wearing NTItss appliances were chosen in
sequence.  Using an algometer (dolorimeter, palpameter, or pressure
threshold meter), two different sets of measurements were obtained.  An
alogometer is essentially a very sensitive force gauge designed to measure
forces applied to very specific locations on a patient.  It is generally
used to measure pain threshold and pain tolerance, but it may also be used
to measure total forces generated or required to produce a desired effect.

In a method described by Steinbroker, two different sets of data were
obtained from each participant in these studies concerning (1) maximum
tongue-tip force and force required to dislodge the NTItss appliance.  Then
these data were analyzed and compared to determine if a patient could,
theoretically, generate enough tongue-tip force to dislodge his or her own
NTItss appliance.

Methods and Materials

Using an algometer with a 1 square centimeter tip, the instrument was held
horizontally between in subject's anterior teeth, facing the tongue.  The
instructions given to each subject were to push as hard as possible with his
or her tongue tip against the the algometer, hold that pressure point for a
second, relax, and repeat the procedure two more times.  The data, in pounds
per square centimeter were recorded.

Then, using the algometer, pressure was applied at the top edge of the NTI
in an inferior direction.  Pressure was applied until the NTItss was
dislodged.  This maneuver was performed three times and the data recorded.

Results

The age range of subjects in this study was 15 years old to 52 years old
(mean average age was 38.43; standard deviation was 10.06).  There were 14
females and one male.  Table 1 lists these data.

The range of tongue-tip pressure was 726 gm/cm2 to 1762 gm/cm2 (the mean
average was 1120.1 gm/cm2; standard deviation was 290.74 gm/cm2).
Table 1: Raw Data
Sub No  Age/Sex  D1(lbs)  D2 (lbs)  D3 (lbs)  Ave (lbs)  Ave (gm/cm2)  T1
(lbs)  T2 (lbs)  T3 (lbs)  Ave (lbs)  Ave (gm/cm2)
1  44/F  8.0  7.1  7.7  7.6  3450  2.4  2.6  2.2  2.4  1090
2  52/F  8.2  8  7.8  8  3632  3.3  1.7  1.8  2.7  1212
3  15/F  7.8  9  7.9  8.23  3736  3  3.4  2.6  3  1362
4  46/M  6.4  6.6  6.5  6.5  2951  3.4  2.9  3  3.1  1407
5  44/F  6.6  7  7.8  7.13  3237  1.8  1.7  1.7  1.73  785.4
6  39/F  3.4  3.3  3.2  3  1362  1.4  1.8  1.6  1.6  726
7  44/F  7  6.8  6.6  6.8  3087  2.3  2.7  3.2  2.73  1239
8  26/F  4.2  3.6  4.8  4.2  1907  2.5  2.4  2.4  2.43  1103
9  41/F  10.1  10.8  8.9  9.93  4508  3.4  2.8  2.8  3  1762
10  32/F  4.8  5.7  6.6  5.7  2588  2.3  1.8  1.7  1.9  863
11  43/F  4.3  4.8  4.6  4.6  2088  2.3  1.8  2.1  2.1  953
12  31/F  3.7  4.1  4.1  3.9  1771  1.3  1.3  2.1  1.7  772
13  49/F  7.5  8.3  7.6  7.8  3541  3.0  2.6  3.1  2.9  1317
14  32/F  6.2  6.0  7.6  6.6  2996 3.0  2.4  1.8  2.4  1090

A: Algometer pressure required to dislodge NTItss appliance
T: Tongue-tip pressure
The range of pressure required to dislodge the NTItss appliance ranged from
1362 gm/cm2 to 4508 gm/cm2 (mean average: 2918.14 gm/cm2; standard
deviation: 880.22 gm/cm2).

Discussion

With every participant, the tongue-tip pressure he or she generated did not
even approximate the force required to dislodge the NTItss appliance (Table
2).  Every subject except two had to exert more than twice his or hers
tongue-tip pressure in order to dislodge the NTItss appliance.

Only vertical forces could be used to attempt to dislodge the NTItss
appliance in this experiment.

Although this is a small, unscientific study, the data still prove the
assertion that the NTItss appliance can not, if fabricated properly as
recommended by the manufacturer, be dislodged by even the maximum amount of
tongue pressure.  Except for two individuals, each subject had to exert over
two times his or hers maximum tongue-tip pressure to remove the NTItss
appliance from the anterior teeth.  No subject could come close to exerting
enough pressure to dislodge the appliance.

In practicality, dislodgment of the NTItss appliance is more difficult than
these results demonstrate.  Only a vertical force could be applied to the
NTItss due to the fact that the maxillary anterior teeth are basically
perpendicular to the anterior thrust of the tongue and no right-angled
algometer was available.

Profitt et al. reported that children and young adults tend to reproduce his
or hers tongue pressure against the anterior palate with both groups
exerting greater lateral pressure (against the canines) than anterior or
tongue-tip pressure.  They also reported that adults could exert only a
slight amount of anterior palatal pressure.

For patients who exert prolonged tongue protrusion against the lingual
surface of the maxillary anterior teeth, most persons, except brass
instrument players (specifically, trumpet players), can produce maximum
pressure for only a short time due to fatigue of the tongue musculature.
Further, as one ages, it appears that one's maximum tongue pressure against
the maxillary anterior teeth diminishes.

Important consideration needs to be given to the thought of aspiration of
the NTItss appliance in the event of its very unlikely dislodgment.  The
literature has little to say about aspiration of foreign dental objects or
devices except that swallowing is more common than aspiration.  However,
those which have been reported are unusual cases occurring after some type
of orofacial trauma.,,,, It is important to note that in all these
citations, all aspirated dental appliances were dislodged due to trauma to
the face and/or dentition and not due to normal orofunctional activities.

Also, there may be a question concerning dislodgment of the NTItss while the
patient is exhibiting parafunctional activities (i.e., clenching and/or
grinding) while sleeping.  In all probability, the forces generated when
performing parafunctional activities would actually aid in retention of the
NTItss appliance.  The act of clenching arouses one from deep sleep, and
that is when a subject clenches, not during deep sleep.  So, when one
becomes active with mandibular movements and possibly with protrusion of the
tongue, arousal and clenching also occur, thus aiding in maintaining the
NTItss appliance in its proper position.  This period of arousal and light
sleep, termed REM (Rapid Eye Movement) sleep is the period where most
parafunctional activities occur.  During REM sleep in those who clench, the
tonus of the antigravity muscles (e.g., the anterior temporalis, the
masseter, and the zygomandibularis muscles) is increased as are spinal
reflexes.

Bader et al.have hypothesized that clenching is a minor alarm and arousal
response to endogenous and/or exogenous stimuli, producing motor activation
of the mandibular closure muscles (i.e., temporalis, masseter,
zygomandibularis, and the medial pterygoid).  This activation produces a
burst of clenching followed by an increase in heart activity.  This burst of
motor activity is primarily in the anterior temporalis muscle with the
masseter basically stabilizing the mandible, thus clenching on the anterior
teeth occur, which further aids in maintaining the proper position of the
NTItss appliance.

Neuroanatomically, it's been shown that dopamine-containing neurons in the
nigrostriatal system of the brain are responsible for arousal from sleep.
It appears that human beings prone to noctural parafunctional activities
have an increase in dopamine concentration, thus producing a burst in motor
activity of the elevator muscles of the mandible.  In other words,
parafunctional noctural activities arouse one from deep sleep, producing
clenching and grinding in many persons.  These parafunctional activities
cannot be avoided in some persons.  If allowed to strongly contact the
posterior teeth, the motor activity of the mandibular elevator muscles will
be heightened, thus producing mechanical and biochemical environments for
the development of headache pain.

Conclusions

Based upon the data gathered in this small but significant study, it can be
concluded that:

   1. The mean average maximum tongue-tip pressure in the human being is
1136.58 gm/cm2;

   2. The mean average pressure required to dislodge an NTItss appliance
was 2958.73 gm/cm2;

   3. The mean average pressure to dislodge the NTItss appliance never came
close to the maximum tongue-tip
       pressure generated by any of the subjects in this study;

   4. Actual appliance dislodgement would require more force measured in
this study because in vivo, a horizontal
       vector of force in addition to a vertical vector of force would be
required.  Only the vertical force could be
       measured in this study;

   5. In all human beings except for those rare individuals who have
trained their tongue musculature to perform
       precise tasks (e.g., trumpet playing), maximum tongue pressure
against the lingual surfaces of the maxillary
       anterior teeth can not be sustained for any length of time.

   6. Maximum tongue pressure decreases with age;

Therefore, given that an NTItss appliance is fabricated properly as
described by the manufacturer and as demonstrated in the video tape provided
with NTItss kits, and based upon the results and conclusions of this study,
it seems totally inconceivable, within reasonable certainty, that an NTItss
appliance could be dislodged by a patient while sleeping.  This is
especially true for patients who are middle-aged and older.