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.
The first documented invention of the doorknob appears in U.S. Patent entries for the year 1878 when a patent for improvements on a door-closing device was issued to a man named Osbourn Dorsey. Very little has been found out about Mr. Dorsey except that he was black.