The active portion of an osseous compression tool for use particularly in dentistry for the preparation of an osseous seat has a cross-section whose perimeter, e.g. of polygonal shape, is defined such that a rotational actuation of the tool around its axis, at least in one direction, preceded or accompanied by its actuation in an axial direction inside the seat, has the effect that the osseous matter is compressed and that the seat is imparted a perimeter of a predetermined shape. In a variant embodiment, a rotation of the tool in the opposite direction allows a scraping or cutting of osseous matter. A tool holder includes a percussion system and allows the translational and rotational actuation of the tool manually or automatically.