Taking insights from the way airplanes pitch, roll, rise and descend, engineers at the University of Bristol (UK) have designed a robot that chews, exerting three dimensional forces not only on the substance being reduced, but on the chewing surfaces.  Britons spend nearly $5 b annually on crowns, bridges and other oral appliances; until this robot debuted at the Royal Society Summer Science Exhibition this summer, there was no way to test the wear and tear on the metal, ceramic and polymers materials in such devices.  So far, the robot does not simulate the bacterial environment of the mouth-though a little acid might do that trick.   MORE