Parkinson disease, which affects nearly one million people in the United States, leads to tremors, slow movement, postural instability, and other motor function issues. However, mouthpieces such as the one recently designed and tested by student researchers at the University of New England (UNE) could improve these symptoms and the quality of life of those who have the disease.
Previous studies have suggested that mouthpieces may be able to improve the gait, balance, and grip strength of patients with Parkinson disease, though the mechanisms behind these benefits remain unknown. The researchers hypothesize that restoring the proper vertical dimension of the maxillary-mandibular relationship may reduce the irritation of the auriculotemporal nerve arising from entrapment or compression.
The reduced irritation, the researchers hypothesize, may normalize sensory impulses traveling along the auriculotemporal nerve and its influence on postural reflexes and limb motor control mechanisms arising in the reticular formation. Assisted by faculty, the students then designed a mouthpiece that increased vertical bite dimension by 3 mm for a 73-year-old man with mid-stage Parkinson disease. The mouthpiece was fabricated by a local dental laboratory.
Using equipment from the UNE Motion Analysis Lab, the students examined the patient’s gait, balance, and strength using the Four Square Step Test, serpentine walk, and tandem walk tasks as well as a dynamometer. Next, the patient completed several tasks both while wearing and not wearing the mouthpiece. He then wore it for a month while going about his usual activities, with no interference with his daily routines.
While wearing the mouthpiece, the patient exhibited subtle improvements in walking, balance, and strength, both during the observed tests and the at-home trial. Also, the patient completed the Parkinson Disease Questionnaire-39, which revealed significant improvements in his quality of life, primarily related to emotional well-being, decreased stigma, and increased communication.
The study provided preliminary support for the idea that a custom-made mouthpiece might reduce some of the movement problems experienced by people with Parkinson disease. However, the students note that more rigorous and extensive research is needed to better understand the mouthpiece’s effect and the extent to which it might serve as a useful and practical intervention for those with Parkinson disease.
“We don’t yet know why the device might have an effect,” said Jim Cavanaugh, PhD, neurologic clinical specialist emeritus, associate professor with the UNE Department of Physical Therapy, and supervisor of the study. “More importantly, we don’t yet know how meaningful the effect really is—it seemed relatively subtle in the one participant we tested—which or how many people with Parkinson disease might benefit, and what the best device design might be—that is, which design, if any, will provide the greatest benefit.”
Cavanaugh also said that the research could explore a variety of next steps. For example, would the thickness of the mouthpiece have any effect? Would off-the-shelf mouthguards produce the same results? Are there differential effects between people at different stages of the disease? And, how does medication influence physical performance?
“The best way to generate solid evidence in support of the appliance as a true clinical intervention would be to conduct randomized control trials—the gold standard of clinical research,” Cavanaugh said. “These types of studies are expensive to run, and so a much larger, more persuasive body of preliminary evidence needs to be generated first.”
Assuming that the accumulated body of evidence supports the effectiveness of the device in patients with the disease who match the description of the study participants, Cavanaugh added, dentists might play a future role in the intervention. For instance, he suggests, dentists could partner with physical therapists to develop a plan of care that combines an oral appliance with physical rehabilitation. Yet even that is far away.
“There is so much we don’t know about this intervention,” Cavanaugh said. “In fact, I would say that the existing research is so preliminary, we shouldn’t include the use of an oral appliance in the list of Parkinson disease interventions.”
The study, “Exploring the Effects of Using an Oral Appliance to Reduce Movement Dysfunction in an Individual With Parkinson Disease: A Single-Subject Design Study,” was published by the Journal of Neurologic Physical Therapy. It was funded by the Westbrook College of Health Professions.