The unlikely link between a painful earache and a blocked nose paved the way for the discovery of a group of patients who had previously gone unclassified.
Dentist David Tay and Dr Kenny Pang, a ear, nose and throat consultant, found that people with upper airway resistance syndrome - a breathing disorder that involves severe snoring - are likely to also suffer from pain around the jaw joint.
The latter is known as temporomandibular disorders (TMD) and they involve the muscles that control the joint that connects the jaw to the sides of the skull.
Dr Tay and Dr Pang established the link in a study of 86 TMD patients aged 25 to 60, of which two in three are Singaporeans.
More than 90 per cent of them were likely to also have upper airway resistance syndrome. Nine in 10 had a nasal blockage, while a similar number grinded their teeth while sleeping, the doctors found.
The findings were published in the Journal Of Oral Rehabilitation in August. It is the first time this link has been established worldwide.
The problem affects people like healthcare executive Veronica Lee.
BREATH OF LIFE
It is tedious to wear the appliances and not easy to relearn how to breathe correctly. But I'm now breathing and sleeping better, and I've not had any jaw aches since.
Healthcare executive Veronica Lee, on having to wear splints and mouth guards during sleep to correct the position of her jaw to alleviate pressure on the joint.
Two years ago, the 27-year-old woke up with a painful earache every few weeks. "The pain would radiate down my neck. I'd find it hard to speak, eat or keep my head upright," she said.
She initially thought the problem stemmed from her ear, but visits to doctors and specialists did not turn up an answer.
Last August, she consulted Dr Tay, who is with the T32 Dental Group. He found that the culprit was her blocked nose. She would breathe through her mouth during sleep, but this caused her jaw to slacken and press on the jaw joint, triggering earaches.
People with TMD may have problems opening their jaw, hear clicking sounds when they open and close their mouth, and suffer from headaches.
These issues are typically treated using an oral splint. They are seldom checked for associated nose problems, said Dr Tay.
Dr Pang, who is with the Asia Sleep Centre, said: "This study raises awareness that joint aches are not to be treated only with oral splints. It shows that there could be an underlying nose sinus issue causing the teeth grinding and jaw ache."
Women are more likely than men to have TMD, although the exact reason is not known.
Dr Pang said: "It is believed to be due to some hormonal issues in the estrogen receptors in the jaw joint."
As a result, the link between TMD and upper airway resistance syndrome is also more likely to be found in women.
Only patients from South-east Asian countries were involved in the study, as people from this region have a similar jaw structure, said Dr Tay, who is also the clinical director of T32's specialist division.
Last September, Ms Lee underwent surgery to remove the nasal blockage and to correct a misalignment in her nasal cavity that makes it hard for her to breathe.
She has to continue wearing splints and mouth guards during sleep to correct the position of her jaw in a way that alleviates pressure on the joint.
"It is tedious to wear the appliances and not easy to relearn how to breathe correctly. But I'm now breathing and sleeping better, and I have not experienced any aches since," she said.