The invention relates to a process for controlling the degree of attrition or wear of a sealing screw (8) conveying a plasticized material, in particular synthetic plastic material, against an resistance, wherein the sealing screw (8) is bearingly supported within a screw housing (4). For this, the pressure of the conveyed material is measured at two locations spaced apart from each other, when seen in direction of conveyance. These two locations are disposed on both sides of a resistance body (12) towards which the sealing screw (8) conveys. The difference of the two measured values is used for indicating the degree of wear of the screw (5) or its housing, respectively. An apparatus suitable for performing this process is provided with an opening (18) which intersects the wall (20) of the housing (4) of the screw (5) in the region of its screw threads or in a region immediately neighboring thereto. A further opening (19) intersects the wall of the housing (4), the two openings (18, 19) being axially spaced apart from each other. To each one of the two openings (18, 19) a pressure sensor (22, 23) is connected.