N.T.I. Tension Suppression System
Technical AnalysisWes Shankland, DDS, MS, PhD , president of the American Academy of Head, Neck and Facial Pain (1998-2000), submitted this report in response to the request for an impartial and independent scientific analysis of the N.T.I. Tension Suppression System .
The following treatise is an attempt to answer four main questions concerning the NTItss appliance.
Specifically, the following questions and concerns will be addressed:1. The question of aspiration of the NTItss.
2. What about supra-eruption of the teeth?
3. What about tooth movement, or intrusion of teeth with the use of the NTItss, especially in the periodontally
compromised patient?In preparing to address each of these valid concerns, the following data banks were searched:
1. Paper Chase: The data base of the Harvard Medical School Library which contains over 11 million
biomedical references, which range from 1966 through the present
2. Grateful Med: A data bank search which includes 16 separate searches with over 9 million biomedical
citations
3. The National Library of Medicine (United States)
4. Medscape: An Internet search engine which includes Medline, the broadest based biomedical data bank in
the world
5. PubMed: A project developed by the National Center for Biotechnology Information (NCBI) at the
National Library of Medicine (NLM), located at the National Institutes of Health (NIH). It has been
developed in conjunction with publishers of biomedical literature as a search tool for accessing literature
citations and linking to full-text journals at Web sites of participating publishers.
6. Recognized authoritative texts
7. In addition, over 40 professors and department chairmen of orthodontics were contacted directly and polled
with the following question:I’m the lead investigator in an FDA study concerning an intra-oral appliance which reportedly reduces
or eliminates migraine headache pain in 65% of those taking Imitrex. The appliance has been given
approval by the FDA as an anti-bruxing device. My charge is to gather information through a 12 week
research study to see if this device does, statistically, reduce migraine pain.The appliance typically fits on the maxillary central incisors and has contact with the mandibular central
incisors (#'s 24 and 25). It’s worn only sleeping (generally) and the teeth are permitted to function
normally during waking hours. Here’s my question for you: Do you know of any published studies which
conclude that such anterior tooth contact causes posterior tooth eruption or anterior tooth intrusion? We
both know what is taught in school and from lecture podiums, but what does the actual research
demonstrate? We also know how in the past, Gelb’s appliance has been attacked for this problem but
then, it’s worn at all times.Can you give me an information or advice about this problem?
To date, I have not receive one response or opinion stating that: (1) teeth will be intruded with the NTItss; (2) posterior teeth will supra-erupt; or, (3) teeth will permanently move with the use of the NTItss.
Introduction I. Danger of Aspiration and Swallowing
of Dental Foreign ObjectsAs 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.
ExperimentTo 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 1090A: 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.
A reasonable consideration about the use of the NTItss appliance is supra-eruption of posterior teeth. Dental students, interns and residents world-wide are all taught that eruption of the posterior teeth will be stimulated if these teeth don’t remain in occlusal contact. However, has this historical maxim actually been demonstrated?
In an attempt to discover any validity of the assertion that posterior teeth will erupt if the posterior teeth don’t remain in contact, the following excerpt of a letter was sent to more than 40 board-certified orthodontist and professors of orthodontics in schools of dentistry:
Do you know of any published studies which conclude that such anterior tooth contact causes posterior tooth eruption or anterior tooth intrusion? We both know what is taught in school and from lecture podiums, but what does the actual research demonstrate? We also know how in the past, Gelb’s appliance has been attacked for this problem but then, it’s worn at all times.
One doctor responded as follows:
I have constructed several of them [NTItss], and have been pleased with the results. I have seen and heard many unsubstantiated references to passive eruption, but I have tried to achieve passive eruption with functional appliances for many years and have almost never succeeded. Some local “authorities” even accuse full-coverage appliances of causing posterior intrusion, but cephalometric evaluation has always shown this to be anterior repositioning in disguise.
Another prominent doctor, engineer, and biomechanic replied: “Since the appliance [NTItss] is a part-time one (less than 10 hours), it would theoretically not permit eruption of posterior teeth.”
A well-known TMD doctor in Florida wrote:
I have been using a night appliance that has contact only on the anterior teeth and hypo-occlusion of the posterior teeth. If any posterior tooth eruption or lower anterior intrusion occurs during sleep, it is so minimal that the patient is unaware of any occlusal changes; but, if there are some minimal occlusal changes in the 8+ hours of sleep, this easily readapts to the previous condition of occlusion during eating and normal daily swallowing, etc.”
A Seattle orthodontist wrote: “I feel the intrusion of posterior teeth is a function of pathological muscle activity of the masseter and temporalis muscles.” In other words, the posterior teeth would have to contact, with the appliance in place, while the masseter and temporalis muscles exhibited heightened muscular activity.
An orthodontist and professor of orthodontics added this comment about the NTItss:
From my orthodontic and research background, it is my opinion there will be minimal or no movement of the maxillary or mandibular incisors with the appliance if worn as described above [while sleeping]. If any minor movement takes place during the sleep period, I believe it would reverse during the waking period.
Probably the most revealing answer received was from William Proffit, D.D.S., Ph.D., Chairman, Department of Orthodontics, University of North Carolina. Dr. Proffit opined:
I'm sure there's nothing published concerning your question. Two thoughts: (1) Some posterior eruption might occur, but it is unlikely that significant, or even measurable, changes in the vertical position of teeth would occur with only part-time wear of this appliance in a 12-week period; but (2) recent research in our lab suggests that active tooth eruption occurs almost totally in the evening, during a 4-6 hour block of time between 6 or 7 PM and midnight. The fact that the patients wear your appliance during this time period, and its apparent effectiveness if it is worn primarily during that time, might be significant. We think that eruption is linked to the levels of growth hormone or related endocrine components. We are just getting tooth eruption data in the first growth-hormone-deficient patients, so that we can relate eruption to hormone levels. It's an interesting thought that the time of day when the appliance is worn to be effective, could be related to endocrine or metabolic cycles rather than just to bruxing patterns.
Similar letters have been received from many other orthodontists and professors. No one as of yet has expressed any concern for intrusion of anterior teeth or supra-eruption of the posterior while using the NTItss.
Compagnon and Woda reported that in the first years following extraction of the opposing antagonist tooth, supraeruption of maxillary first molars occurred due to growth of the periodontium because of a lack of stimulation. In other words, if opposing teeth are separated only intermittently, as with the use of the NTItss, supraeruption does not occur as long as the teeth are permitted to function from time to time.
Tooth eruption, after puberty, is not common. Ono reported as an erupting tooth reaches the occlusal plane, the rate of eruption movement decreases and usually, tooth eruption of unopposed teeth occurs only in young persons.
Probably the most revealing (and supportive) research pertaining to the NTItss appliance was conducted by Kinoshita et al. In an eloquent study, these researchers demonstrated that it took at least 8 days of hypofunction (i.e., no occlusal contact at all) of the molars before eruption of the unopposed molars occurred. Although the specimens in this study were rats and not human beings, the results still demonstrate that a long period of time is required before unopposed molars begin to erupt. Fortunately, use of the NTItss only requires a few hours of no posterior occlusal contact, not days.
In the human being, perceivable tooth eruption of unopposed teeth proceeds at a rate of 1.43 millimeters in 16 months to 1 millimeter per two months. Compagnon demonstrated that, “. . . in the early years after the tooth loss, supra-eruption is due mainly to periodontal growth.” Such periodontal growth does not occur when a tooth is in frequent function, such as the posterior teeth when the NTItss is removed during daytime hours.
Conclusion
Based upon the information presented here, especially in light of the comments by many of the leaders in orthodontics, it seems more probable than not that use of the NTItss appliance with subsequent normal dental functioning will not induce or permit tooth supra-eruption.
In addition to supra-eruption, another reasonable concern with use of the NTItss appliance is the thought of intrusion of the anterior teeth, especially the mandibular teeth.
Intrusion of the mandibular anterior teeth due to intense clenching of the teeth is very difficult if not impossible simply because of the jaw opening reflex controlled by the trigeminal nerve. During active sleep, the jaw opening reflex is post-synaptically inhibited. However, during REM sleep and clenching on the NTItss appliance is at its height, this inhibition ceases due to proprioceptive stimulation of the periodontal ligaments and stimulation of the tooth pulps of the mandibular anterior teeth. Since the NTItss theoretically contacts the mandibular anterior teeth in only one spot, clenching is focused at that point, thus intensifying the stimulation of the periodontal ligament fibers, which in turn, stimulates the jaw-opening reflex.
Woods demonstrated, using adult baboons, that high forces placed on mandibular anterior teeth for a period of 5 months were only effective in moving and/or intruding teeth if the forces applied were forward of the center of gravity. The NTItss applies forces directly down the long axis of the mandibular anterior teeth, thus greatly minimizing any forces forward to the center of gravity.
Dr. David Tay, a prominent Singaporean prosthodontist and professor, wrote the following in a personal communiqué:
Sometimes in full mouth rehabilitation when we want to purposely intrude mandibular anterior teeth and yet preserve the occlusal vertical dimension, a Dahl appliance is used. It is almost like the NTItss as it wraps around the palatial surfaces of the opposing teeth we want to intrude. Curiously, if the appliance was made from acrylic or any dampening/shock absorbing material, no intrusion is effected. However, if this Dahl appliance was cast in chrome cobalt, the intrusion could be observed usually in a few weeks if the patient wears the appliance 24 hours per day.
Dr. Tay makes the point that intentional intrusion, even after several weeks of appliance wear for 24 hours per day, is difficult at best. The Dahl appliance rests only on the mandibular anterior teeth and it must be made of a cast metal material and not a softer acrylic like the NTItss.