The invention relates to a dental preparation instrument (1), comprising a tool (6) that rotates in an alternately reversible manner, wherein the preparation instrument (1) has a drive (2) for the tool (6). The drive (2) provides a continuous fully rotational motion (7), and a gearing (43) is arranged before the tool (6). Said gearing converts the continuous fully rotational motion (7) of the drive (2) into an alternately reversing rotational motion (8), which is continuous as viewed over several reversals.
