The Whitehead gag --invented in 1877 by Walter Whitehead (1840-1913), a surgeon in Manchester, England -- consists of two hinged metal frames that wrap around the front of the patient's head and which have sections bent to fit between the front teeth. When spread apart, the frames separate the jaws, holding the mouth open.
Don't think Whitehead ever thought about slave/sub, bondage and punishment uses for his invention! This is the 4.5" Locking Whitehead Dental Gag. Professional Grade. Made of stainless steel, can be autoclaved.