The first powered dentist's drill was made by George washing-ton's dentist, john greenwood, who adapted his mother's spinning wheel with its foot treadle to rotate his instrument. Earlier dentists had operated their drills by means of bowstrings, a method which must have required skill, determination and physical stamina on the part of the dentist, as will as a great deal of courage from the patient. Later drills were operated by turning a handle at the side. In 1829 James nasmyth, the Scottish inventor of the steam hammer, used rotary power to improve the efficiency of the drill. A hand-operated drill with a flexible cable was patented by Charles merry, an American dentist in 1858; and George Harrington in 1864 a drill driven by a clockwork motor.
المصدر: منتديات الوزير التعليمية Arabic Minister Forums, Educational and Networking - Alwazer - من قسم: Ministry of General English
Who first uesd a powered dental drill?
via منتديات الوزير التعليمية Arabic Minister Forums, Educational and Networking - Alwazer http://vb1.alwazer.com/t92062.html
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