Aching jaw? UD scientist works to unlock mystery

If you have ever experienced a sore jaw from grinding your teeth, too much chewing gum or a long session in the dentist chair, it's likely you know where the temporomandibular jaw joint is located.

For the rest of us, this tiny little joint is situated just under the ear, and it acts like a sliding hinge that enables our ability to talk, laugh, chew, swallow and yawn. Made up of tissue, muscle and tendons, it is considered one of the most used joints in the human body, opening and closing over 2,000 times per day.

It's not something we think about, of course, unless we run into trouble.

For those living with temporomandibular joint (TMJ) disorders, however, this hinge can cause immense pain when the disc that enables its sliding action gets caught between the top and bottom of the jaw. With no cure and few treatment options, these joint disorders can substantially affect quality of life.

Joohyun (Jason) Lim, a developmental biologist at the University of Delaware with an interest in human genetics, hopes to change this by advancing understanding of the disease process at the molecular level. Armed with an R01 grant from the National Institutes of Health, Lim is particularly interested in osteoarthritis of the temporomandibular joint (TMJ-OA), a degenerative disease that contributes to jaw problems affecting over 11 million people in the United States annually, including TMJ.

"It's a tissue that's been largely ignored, and there isn't really a standard of care," said Lim, assistant professor of biological sciences. "You either take general pain medication, rest, don't chew in an area, and that's about it. And yet TMJ is so common, but it's not really discussed."

Leveraging genetics to better understand osteoarthritis

Osteoarthritis (OA) typically occurs due to trauma or genetic consequences that emerge later in life. For people with OA in the knee, which is also a hinge joint, the solution is often a joint replacement as they age. Timed appropriately, it's a solution that can last many years.

But for those with TMJ-OA, disease onset often occurs in younger individuals, particularly women ages 20 to 40 years old. Here, non-invasive therapies are considered best, since jaw joint replacement early in life would require regular updating every 10 to 20 years.