Abstract: A non-destructive method for determination of twist angle of an outlet product during rolling of an inlet product into said outlet product, comprising the steps of measuring a rotational inlet speed of the inlet product during said rolling, measuring a rotational outlet speed of the corresponding outlet product during said rolling in order to determine a delta rotation, measuring a longitudinal speed and determining a twist angle from said delta rotation and said longitudinal outlet and/or inlet speed.

Abstract: In a dental preparation instrument consisting of a shaft part and an adjacent operating part of a configuration with cutting areas for the preparation of a tooth, wherein the front end area of the operating part comprises a surface areas of non-cutting configuration in the form which, at least in a front view, is a center circle with a diameter of a fraction of the diameter of the operating part at the transition area thereof to the front end area, the non-cutting surface area and the adjacent area of cutting configuration are steplessly fading into one another.