[High frequency cinematographic investigations of the mode of operation of common grinding instruments on bone and cartilage (author's transl)].

The mode of operation of grinding faces, rod diamonds and diamond grinding heads which are expecially employed in oto-surgery was investigated in slow motion pictures with the aid of high frequency cinematography. The R.P.M. ranged between 5,000-80,000, the picture frequency was usually 6,000 pictures per second. Full efficiency of the diamond grinding heads (DS) is only guaranteed by adequate flushing. Water stream flushing and drop flushing (drop sequence depending on R.P.M.) must be centered on the grinding head, as increased soiling due to filling of the diamond surface occurs otherwise. Because of the fixed mounting of the spray tube in the direction of the shaft, spray flushing is most useful, although not unsable for diamond faces. Due to its very fine-rough surface, the DS produces grinding dust by abrasion from the bone or cartilage which is readily distributed in the airspace over the whole working area. The same does also apply to finely atomized fluid sprays. Cutting is performed tangentially. The percussing DS touches the bone only with a small part of its surface and easily gets soiled. Depending on the R.P.M., the cutting speed was 10,000-80,000 R.P.M. These values also apply for the fluid dropping rate. Contrary to the rose bit or the surgical fraises, the DS got soiled more easily and produced definitely finer cuts.