Dr. David Hornbrook
interviews Dr. James Boyd
Dental Practice Report, November 2001
Quick links to question topics:
Q: The NTI appliance has gained much notoriety
recently with your appearance
Morning America, however, this device been around for a couple of years.
Still, many dentists arenít yet familiar with it. What is the NTI and what does
it stand for?
NTI is a tension suppression system that uses the bodyís natural reflex protection
when being used during waking hours. At night it prevents and reduces
the muscular component of migraine, chronic headache and jaw disorders by preventing
parafunctional contacting of the canine and molar teeth. It represents a major
improvement over splints and night guards in treating and preventing clenching,
grinding, bruxing, stiff neck,
tooth sensitivity, tension headaches and TMD.
The device is a small, clear, taco shell-shaped appliance that fits over the
upper two front teeth. Attached on the incisal edges of the taco shell is a bump
or a bar that extends anteriorally and posteriorally to provide
the point stop.
NTI stands for Nociceptive Trigeminal Inhibition. This is a technical way of
saying the jaw opening is a reflex, and this device provides a way to suppress
the elevating muscles of mastication.
Clinicians are familiar with this concept. This is what an anterior deprogrammer
or a Lucia jig is all about, however, the reason why the concept of the Lucia
jig canít be used in a therapeutic, night-after-night modality is that if the
mandible moves around, that is, it will ďdefeatĒ the jig by allowing fro a canine
contact on the jig. The NTI is the adaptation of the Lucia jig to provide
for mandibular movements while still suppressing clenching
The NTI provides for lower incisor contact to just prior to posterior occluding.
This provides for ideal condylar seating or the best condyle location during
relatively simple concept. To be successful with the NTI, you donít have to take
a lot of courses or learn a lot of theory. Itís based on established medical,
Q: Who fabricates the NTI, the dentist
or a laboratory?
Boyd: The NTI is a pre-fabricated matrix that eliminates all of
the laboratory work and most of the chairside procedures involved with splint
fabrication and delivery.. Althought a dentist can make an NTI
type device from scratch, the prefabricated matrix gets you 75% of the
way to producing the final device.
Thereís no need to take an impression or create models. A dentist could make
this in his or her office without an NTI matrix and wouldnít be infringing
upon NTI patents. For those occlusal schemes that donít allow for the
easy use of the NTI device, the website describes ow to easily make a custom
NTI-type device in the office.
Q: What was your incentive to come up with the
Boyd: It really was for my own use. I was a typical TMD patient who had a headache
every day, all day long and I would occasionally have migraine headaches. Part
of my symptoms involved a loud clicking joint, difficulty with opening and
sometimes my jaw would get sore from chewing. I went through traditional TMD
splint therapy and I was one of those people who seemed to get worse from the
splint. Iíd wear it a few nights and then take it out for a night or two and
then put it back in.
Q: The concepts of bruxism, TMD and clenching tend
to have various definitions, and many practitioners relate parafunctional
habits to the Pandoraís box of bruxism. How do you define bruxism and how
do you get outside the box of splint therapy?
Boyd: Physicians, dentists and the general public tend to think that bruxism
means grinding of the teeth, but thatís just the ďsecond halfĒ of the
conditionís acutual activity. You can have your jaw in a rest position
and move it excursively back and forth and protrude and retrude. Thatís not
bruxism, although the lateral pterygoids are functioning. You have to elevate
the mandible first, which weíll define as clenching. Once those teeth come
into contact or are occluding, due to the continual elevation of the mandible,
onlyh then is grinding possible.
At that moment, the lateral pterygoids are supposed to contract and reopen
the mandible. Thatís a normal chewing or swallowing stroke. However, in bruxism, the
temporalis refuses to release and keeps these teeth occluding, or, ďin occlusionĒ as
we say in dentistry. The intensity of the elevation or the intensity
of the perpetual clenching in the presence of the lateral pterygoid attempts
at re-opening the mandible will dictate the grinding severity that results.
As the temporalis contracts more intensely, the teeth are occluded more tightly,
thereby providing more resistance the lateral pterygoids. In other words, the
grinding activity might become more severe. At the maximum degree of clenching,
the jaw cantí move at all and the lateral pterygoids donít have a chance of
any excursive activity. So, I look at bruxism as a function of clenching. The
intensity of clenching dictates the severity of the grinding .
Dentistry seems to enter in mid-stream. Once the mandible has been elevated,
the teeth are in contact. As the lateral pterygoids naturally attempt to reopen
the mandible, they are met with opposing resistance provided by the temporalis,
often resulting in the signs of symptoms of TMD, and we address them.
My approach to bruxism is to suppress the clenching intensity first, instead
of trying to treat the results of lateral pterygoid activity.
Q: In the past, I had used a full occlusal
splint, mounted in centric relation, to try to treat bruxism. Some clinicians
feel this approach adds to the clenching. Do you believe thatís correct?
Boyd: The temporalisí maximum contraction ability is with the teeth slightly
apart. With some patients, when you provide a full-coverage splint thatís 2
mm thick and is mounted in centric relation, you may be providing the optimal
ability for clenching intensity. And if the patient does this, he or she will
have ideally stabilized jaw joints. Youíll address the TMJ condition and youíll
The patient may still have headache or migraine pain or that may intensify.
It wouldnít be apparent to the dentist, however. We tend to look below the
cheekbone, and weíll have some success with those symptoms and never consider
that perhaps the patientís increased temporal headache or migraine might be
from the new ability to clench with more efficient intensity.
Q: Some clinicians feel the NTI device is
essentially a deprogrammer. Is that a fair analogy? Also, how does it differ
from the deprogrammer device used at the Pankey Institute or the Lucia
Boyd: The Pankey device is a prefabricated deprogrammer. A Lucia jig is a device
you fabricate yourself. There isnít any disagreement over what these devices
do. Theyíre designed to create ideal condylar seating and relaxation of musculature.
However, the reason why theyíve never been incorporated into therapeutic practice,
meaning letting the patient wear it every night, is that the mandible moves
Letís look at one example of how this movement can affect the patient. If the
mandible moves to the left, the lower right canine would have the ability to
contact the deprogramming device. Canine contact allows for near maximum temporalis
clenching. If the mandible demonstrates a left excursive movement with the
right canine in contact, significant joint strain results. Thus, you may see
a patient after four or five nights of using a deprogrammer who will say that
the device works great, but then a week later they may be saying their joint
is killing them.
Dentists reflexively would say, ďWe canít use that device long term because
there could be joint strain.Ē No consideration is given to how that joint strain
was created. The NTI is the response to that potential mandibular movement
to prevent those joint strains.
Q: Are there any contraindications on
using the NTI?
Boyd: The primary contraindication of the NTI is in the presence of some degree
of internal joint derangement that is not related to muscular parafunction.
In fact, itís quite rare, but in those cases youíve got some degree of arthritic
condition. An NTI device might be contraindicated even though the patientís
muscular intensity is decreased. They still have the ability to move excursively,
which might be straining for the joint. In those cases, a full-coverage splint
is going to be a better option.
Other than that type of condition, there really arenít any contraindications
for the NTI device. Unless, of course, the patient doesnít have incisors or
if the dentist misuses the device by increasing the vertical dimension more
than is required, which could create joint strain. Obviously, if doctors donít
follow the protocol, they can do harm.
Q: So the NTI could be used as an alternative
to long-term splint therapy?
Boyd: Exactly. Iíve worn mine every night for 12 years now. Some clinicians
might say, ďWhat about the possibility of posterior supra eruption?Ē A posterior
tooth that receives regular alveolar stimulation, which comes if the person
chews food once or twice a day, has no opportunity for supra eruption.
In my case, none of my teeth has supra erupted since I began wearing the NTI.
In fact, weíve never seen a true case of a posterior supra eruption with this
device. However, clinicians sometimes mistakenly identify posterior supra eruption
when a patientís mandible seats itself; that is, the condyle has seated into
its musculo-skeletally stable position when it hadnít been before. If condyles move
posteriorally and superiorly, that reseating creates more posterior and
less anterior occluding, thus giving the illusion of posterior supraeruption. However,
both planes of occlusion have remained unchanged and it is a mandibular shift
you are seeing.
Q: As youíre well aware, there is a
lot of interest in and controversy surrounding occlusion today. Whatís
your occlusal background and your philosophy regarding how these patients
should be restored?
Boyd: I look at the three components: musculature, bone and teeth. To me, the
teeth, which are embedded in the bone, are along for the ride that the musculature
I believe all dentists are trained in sound occlusal restorations in the musculo-skeletally
stable condylar position. I like the term Dr. Jeff Okeson uses ďmusculo-skeletally
stable.Ē We want the musculature to be in a normal, not a parafunctional or
a dysfunctional, state. .
The way to achieve this state is to not give the musculature the opportunity
to perform parafunctionally, with hypercontractions. Musculature can only do that
after the posterior or canine teeth are occluding.
Prior to initiating occlusal therapy, the NTI can provides for a normalized musculature,
thereby allowing for the optimal musculo-skeletally stable condylar position. Centric
relation happens during a dynamic activity, while the condyle is being
seated during active closure against resistance, which is the food between
the teeth. Itís not something that a dentist can dictate, but what normal
musculature creates. Dentistry can provide for normal musculature,
thereby allowing for optimal condylar seating. The dentist will
then be presented with an occlusal scheme that may or may not require restoration.
Once the jaw closes and the teeth are coming into contact, normally the jaw
would start to reopen. Thatís what the lateral pterygoids are supposed to do.
But when the muscles of elevation refuse to relax,the lateral pterygoids encounter
resistance. The presense of occlusal interferences causes an imbalance
in the lateral pterygoids thereby causing changes in condylar position. So
it makes sense to address the interferences to create a non-interfering occlusal
Once those interferences are removed, the patient may have an optimally seated
condyle and an optimal occlusal scheme. This doesnít mean that the parafunctional
muscular activity is going to stop. You see that when you put in the ideal
full-coverage splint mounted in centric relation. Patients still clench on
those appliances. Iím not convinced that ideal occlusal schemes and ideally
seated condyles will eliminate muscular hyperactivity. In fact, sometimes it
just allows it to perpetuate.
Q: It seemed suddenly that the FDA approved the
NTI for the prevention of medically diagnosed migraine pain. Does this
mean that there is a relationship between clenching and migraine pain?
Should dentists be treating migraines?
Boyd: There is a relationship between migraine pain and clenching. For example,
all migraine patients and tension-type headaches patients exhibit pericranial
In dentistry, we instinctively know what that means. In medicine, physicians
donít routinely perform muscular palpation and typically donít inquire about
or investigate pericranial tenderness. When the tension-type headache patients
and migraine sufferers describe their pain, the physician interrogates and
makes the diagnosis and referral. What they donít recognize is that pericranial
tenderness is most likely the result of hyperactivity of the musculature. These
patients, who are clenching nocturnally, have hyper-temporalis activity. This
is an ingredient in what neurological scientists call kindling for migraine
The relationship to migraines is that these patients have high degrees of clenching
while theyíre asleep. Dentists donít see this because many times the migraine
patientís teeth look perfect. After all, they never grind their teeth because
theyíre too busy clenching. Their jaw joints are fine because theyíre well
supported during clenching and may even be in an ideal relationship.
All of this is not to suggest dentists should be diagnosing migraines. Thereís
a huge difference between the diagnosis of migraines and the prevention of
migraine pain. The diagnosis of a migraine requires that a physician perform
a CAT scan, MRI, X-rays and examine blood work.
Once a patient has been diagnosed with migraine pain, meaning thereís nothing
wrong with the patient objectively, the dentist can easily perform palpation
to determine pericranial tenderness. Thatís when the NTI is used, as part of
the protocol to prevent migraine pain.
Q: What are the success rates with the NTI
in terms of eliminating bruxing, clenching and migraine pain?
Boyd: In the clinical trial data submitted to the FDA, 82% of medically diagnosed
migraineurs (whom Iíll call ďprimary clenchersĒ) reported on average, a 77%
reduction in their migraine frequency within the first eight weeks of wearing
On the other hand, when we look at TMD or excursive activitiesóBruxismódentists
have an even greater success rate because the patients theyíre treating with
this device donít have as much clenching intensity. Dentists are a little surprised
by the NTIís effectiveness. By the same token, they also see how quickly a
patient can get worse if they donít adhere to proper protocol.
I tell doctors: Donít think this is an easy, no-brainer thing to do and that
all you have to do is pop it in the patientís mouth and they get better. You
could make somebody a lot worse with this device, which is really one of the
indications that itís effective. If used properly, though, itís quite effective.
Q: What are some of the critical factors
that determine success with the NTI?
Boyd: The most significant factor in achieving success with the NTI is the
degree of vertical dimension of freeway space the device creates.
As that vertical dimension increases we have to ask whether the condyle
been significantly translated due to the presence of the device. I think of
translation as leaving home base. During Parafunction, you want the condyle
as close to home base as possible at all times. If you have too much vertical
dimension, that is, translation, you risk straining the jaw joint. If you donít
have sufficient freeway space, you may be providing for canine of posterior
occluding in excursive movement, thereby allowing for an increase in clenching
intensity and/or joint strain.
Letís say the patient has a 1 mm or 2 mm posterior disclusion or free way space
with the NTI in place, but the moment they move excursively you get a posterior
contact or a canine contact, therefore providing for the ability for clenching
intensity while this joint has been translated to a degree.
Itís the vertical dimension of freeway space created by the NTI that is fine-tuned.
For example, as the patient moves excursively and you see a posterior contact
with the NTI in place, it will be the most obvious presentation of an interference
that you could ever get. That would be instant grounds for occlusal equilibration.