Dental Device Reduces Clenching and Headache Pain

Daniel M. Keller, PhD

September 18, 2009

September 18, 2009 (Philadelphia, Pennsylvania) — A small intraoral dental device augments the efficacy of valproic acid (VPA; Depakote, Abbott, and others) for the treatment of migraine or tension-type headache without adding any adverse effects, a new study shows.

The nociceptive trigeminal inhibition (NTI) device is a custom splint fitted by a dentist that spans the upper or lower anterior teeth and provides a spacer to allow only incisor edge contact while keeping the rest of the upper and lower teeth from meeting. Jaw opening is only a few millimeters.

The device reduces the maximum nocturnal trigeminal motor activity leading to jaw clenching by the temporalis and lateral pterygoid muscles, with resultant sensory nociception of muscle and joint strain, facial and sinus tension, and periodontal ligament compaction. The device has been approved by the Food and Drug Administration for the prophylactic treatment of medically diagnosed migraine pain.

Investigator Andrew Blumenfeld, MD, director of the Headache Center of Southern California in Encinitas, coauthored a randomized study testing VPA alone, the NTI splint alone, or the splint plus VPA in 60 patients (18 years or older) who had migraine or tension-type headaches by International Headache Society criteria. VPA dosages were 200 mg twice daily. He presented his study results here at the 14th International Headache Congress.

Significant Pain Reduction

Patients reported pain on a visual analog scale (VAS) before treatment and then weekly during treatment for 8 weeks. Baseline pain scores for the 3 groups were equivalent and ranged from about 7.5 to 8.1 on a scale of 0 to 9 (least to most pain).

Pain reduction with the combination of VPA plus the NTI splint (76%) was statistically significantly superior to either VPA alone (61% reduction) or the splint alone (62% reduction; P <.0001 for the combination vs either alone). The VAS pain score for the combination group was 1.8 vs 3.1 for each of the other groups. All treatments produced significant pain reduction compared with the baseline pain scores for each group.

Dr. Blumenfeld reported that there were no systemic adverse effects with the splint alone, and it did not exacerbate the adverse effects of VPA when used in combination.

He concluded that the known efficacy of VPA for headache prevention could be enhanced by using the NTI splint while avoiding worsening of adverse effects that may arise if the VPA dose were to be increased, as VPA adverse effects are dose-related. Dr. Blumenfeld cited weight gain, fatigue, alopecia, hirsutism, tremor, and liver function abnormalities as potential adverse effects of VPA.

In his poster presentation, Dr. Blumenfeld summarized the results of an earlier trial involving 20 consecutive patients with treatment-refractory chronic daily headache. All patients scored in the "severe and disabling" range on the Headache Impact Test, despite maximal oral prophylactic medication. They were fitted with an NTI splint, which they wore nightly for 9 months. By 2 months, half of the patients had significant improvement, which persisted for the rest of the 9 months. Interestingly, 25% of patients reported that chronic headache no longer had any effect on their lives.

Enlisting Dental Help

The Headache Center of Southern California consists of 11 neurologists, and Dr. Blumenfeld has now brought in a dentist. "We believe that you can do a lot with medications, but adding in additional treatments like dental splints makes a huge difference to the outcome," he told Medscape Neurology. "We can add in a dental device without any [adverse effects] being added to, as opposed to adding a second medicine." He has also used the splint in combination with medications other than VPA, including botulinum toxin injections into the temporalis or masseter muscles, with a synergistic effect documented by electromyography.

Unlike other dental splints that cover all the teeth, the NTI splint keeps the teeth apart. Full-coverage splints allow the teeth to bite down on them, activating the muscles, and therefore do not prevent clenching. Dr. Blumenfeld explained that the NTI splint actually relaxes the musculature by not allowing clenching. "These muscles are supplied by the trigeminal nerve, which is the main nerve that is involved in migraine," he said. By relaxing the muscles at night and not stimulating the nerve, patients have a higher threshold for triggering a migraine the next day.

He explained that the splint prevents clenching because when incisors meet, there is an inhibitory reflex to prevent further pressure, but this reflex does not operate for the molars. The splint actually enhances the inhibitory reflex.

The splint is good for patients who want to avoid medications as much as possible. "It's also useful in pregnant patients," Dr. Blumenfeld said. VPA is absolutely contraindicated for these patients, "but this is our mainstay of treatment in pregnancy because it's perfectly safe," he said. For adolescents who may forget to take their medication or who become fatigued on it, a splint may be a reasonable alternative.

He noted that dentists are aware of the NTI splint, but in general, it is not well known in the medical community, and "there is not a good communication between the 2 specialties."

Introduced To More Neurologists

Steven Bender, DDS, of the North Texas Center for Head, Face, and TMJ Pain, Plano, Texas, agrees and hopes that the device will be introduced more to neurologist-driven headache centers, institutions, and private practices. However, he also thinks dentists should be trained better in neurology and that headache residencies should expose trainees to what a dentist can do for facial pain.

Dr. Bender said he has used the NTI splint for 5 years with great success among thousands of patients. He said Dr. Blumenfeld's data correlate well with what he sees clinically and what his patients report on the VAS at each visit.

"We see even without the medication a dramatic decrease in the number of headache days and the headache severity," Dr. Bender told Medscape Neurology. "When patients come in on medications, we see an increase in the efficacy of what they're using as well as sometimes the ability to withdraw them from the preventive medications." He said he prefers patients use the device for 6 to 12 months, but most patients do not want to give it up once they have achieved pain reduction.

His typical patient has seen 6 to 9 specialists before coming to him, and Dr. Bender estimated that his center's success rate with this or other dental appliances may reach as high as the mid- to high 90% range, based on quality-of-life measures, VAS scores, and subjective reports.

In choosing appropriate patients for a dental appliance, he said he looks for signs of sleep time bruxism or clenching of the teeth and tells neurologists to look in patients' mouths, "not only at the teeth but looking at the lateral borders of the tongue for indentations or impressions of the teeth, [and] sometimes ridging of the buccal mucosa will be indicative." Radiography also may reveal changes in the bone.

The study was investigator-initiated and received no commercial support. Dr. Blumenfeld has disclosed that he is a consultant and speaker for Allergan and has intellectual property relationships with Allergan. He has had research funding from Allergan and from Keller Laboratories, which makes and fashions the NTI splints. Dr. Bender has disclosed that he has received complimentary product from Keller Laboratories.

14th International Headache Congress: Abstract PO348. Presented September 11 and 12, 2009.


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