The Roc-B-Tween toothbrush
Between 1932 and 1988, over 500 different toothbrush designs were patented in the United States, each professing to provide significant improvements in tooth cleansing. Among these, the Roc-B-Tween toothbrush, patented in Oakland in 1938, offered oscillatory movement with a “rack and pinion-like effect” occurring between the bristles of the toothbrush and the spaces between the teeth, effectively cleansing a “vital spot.”
Mattick, BE 2010 A Guide to Bone Toothbrushes of the 19th and Early 20th Centuries. Bloomington, IN: Xlibris Corp; McMath, JF Dental Instrument. Patent 2122619. 5 July 1938. Print.