LEAD: Leonard Lorch, an entrepreneur in Stanford, Calif., has invented a dental floss that has toothpaste encased between two thin ribbons of Teflon fiber. The floss offers a way to get toothpaste between teeth. In addition, the Teflon coating is smoother and less likely to cut gums, the inventor said....

LEAD: Fifty years ago today, in the aftermath of a failed experiment on refrigerator gases, Roy Plunkett, a Du Pont researcher, discovered a white powder that had to be handled like a metal. Polytetrafluoroethylene came to be known as Teflon. It helped build the atom bomb and introduced the world to no-stick frying....

LEAD: IT might seem too soon, according to the memories of some people, but 1988 marks the 50th anniversary of the introduction of two synthetic materials that ushered in the golden age of polymer chemistry: nylon and Teflon. A half-century later, both materials are still widely used staples in the industrial world and continue to generate innovative new uses....