Dentists in Taiwan have warned fast food chains to drop over-sized hamburgers from their menus because so many people are suffering with jaw injuries.
They are also calling on the burger bars to label a warning on their kingsize burgers.
Patients have developed sore jaws or had difficulties opening their mouths after biting on the giant burgers.
Fast food joints have been selling burgers that are more than eight centimetres high.
Experts point out that the human mouth is designed to gape over objects measuring only up to four centimetres.
Many diners had to see dentists for jaw-related issues after consuming burgers served by two fast food chains, whose sizes are larger than normal, said Hsu Ming-lun, associate professor of the School of Dentistry of National Yang-Ming University.
Some of them faced sore jaws and some even had difficulties opening their mouths; both are typical symptoms of Temporomandibular dysfunction, an injury related to jaws, added Hsu.