Abstract: The invention relates to an interdental wedge for use with a matrix band when preparing a filling on a tooth to be restored and/or for use with a rubber dam, by inserting the interdental wedge into an area near the gingiva between the tooth to be restored or to be treated and an adjacent tooth, with an insertion area having a cross section delimited by a lower face, by an inner face and by an outer face, wherein, in the state inserted near the gingiva, the lower face is directed towards the gum, the inner face is directed towards the tooth to be restored or to be treated, and the outer face is directed towards the adjacent tooth, wherein the inner face and the lower face run together in an edge, which is designed such that, in the state inserted near the gingiva, it bears on the tooth to be restored or to be treated, in order to provide a sealing action against passage of material.