Temporomandibular joints are among the physical characteristics that differentiate mammals from other vertebrates.
These joints—one on each side of the jaw—help connect the mandible to the skull and provide the range of motion necessary for biting, chewing and (in humans) speaking. The joints also lend their name to temporomandibular joint disorder (TMJ), a common condition that can inhibit jaw movement and lead to uncomfortable symptoms including chronic headaches. Although temporomandibular joints differ among species, looking at these components in other mammals helps us better understand their function and the effects of TMJ.
I am the Walrus (with TMJ)
A Sept. 28 article in Hakai Magazine discusses the prevalence of dental problems in marine mammals. The article focuses on the work of veterinary scientist Frank Verstraete and his team, who are conducting an ongoing study of marine-mammal skulls.
The researchers recently completed an analysis of 76 walrus skulls and mandibles. More than 60 percent of the specimens showed evidence of temporomandibular joint erosion. The cause of deterioration in most cases is believed to be arthritis, a frequent contributing factor in TMJ.
The findings of the walrus study were published in the August-October 2016 edition of the Journal of Comparative Pathology. Prior research has indicated similar jaw joint problems, including arthritis, in sea lions, a close relative of the walrus.
TMJ: Key Differences
As with people, the cause of TMJ in other mammals varies and is not always clear. In humans, for example, TMJ can sometimes result from the erosion or displacement of the articular discs, which facilitate jaw movement.
But walruses lack articular discs, and neither walruses nor sea lions chew their food. Walruses use their tusks—which are extended canine teeth—to forage, but they swallow their food whole. Sea lions likewise swallow chunks of food whole, though they do use their teeth to clamp onto and tear food.
As Verstraete observes in the Hakai article, “oral pathology can provide insights into the natural history of species, including a better understanding of feeding, behavior, and causes of death.” The examination of shared characteristics, such as the temporomandibular joints, and deviations, such as the articular discs, in other mammals also expands our knowledge of TMJ’s causes and effects in people.
TMJ and the Animal Kingdom
Animals have played important roles in our ability to diagnose and treat TMJ in people. As we noted in a previous post, sheep in particular have been instrumental in advancing our understanding of and ability to treat TMJ.
Last month, the British Journal of Oral and Maxillofacial Surgery published the findings of research that examined the effects of using chitosan membrane—a viscous polysaccharide with biomedical applications—to prevent articular disc adhesion following TMJ surgery in goats. Researchers found the material inhibited adhesions and promoted cartilage repair.
The need for surgery to correct TMJ is rare, but the study could prove useful for future treatment methods. In people, TMJ can often be treated comfortably and effectively with custom-made oral devices that hold the jaw in proper position. Many patients also find success with BOTOX® or occasional TENS therapy sessions, both of which relax the jaw muscles and allow the jaw to settle into natural alignment.
Denver neuromuscular dentist Dr. Kevin Berry has helped many patients find lasting relief from TMJ pain. If you suffer from recurring headaches or jaw and facial discomfort, please call the TMJ Therapy & Sleep Center of Colorado at (303) 691-0267 to schedule your appointment.