Semi-adjustable articulator with mounted casts. An articulator is a mechanical device used in dentistry to which casts of the maxillary (upper) and mandibular (lower) teeth are fixed, reproducing recorded positions of the mandible in relation to the maxilla.
The Greek scholar Heron of Alexandria created the earliest known automatic door in the 1st century AD during the era of Roman Egypt. The first foot-sensor-activated automatic door was made in China during the reign of Emperor Yang of Sui (r. 604â618), who had one installed for his royal library.
Friday, October 17, 2014. Osbourn Dorsey Invented the Doorknob and Doorstopper. Ever since the first door was created, it is likely that human beings have understood how to use an object or device to keep it open. Heavy stones or bricks or metal cans or chunks of wood all work to prevent a door from closing. Mr. O. Dorsey was a 19th century African-American inventor.