A mechanized dental instrument includes an active part (2) and a sleeve (3) arranged on an end of the dental instrument which opposes the active part. The sleeve (3) is provided with a rotary drive means (4) that can, when assembled with the head of a handpiece, directly engage with a rotary drive means located upstream of the head of the handpiece. The drive means (4) is produced from a flat metallic piece which is fixed to the active part (2) by being slid over the axle (2a) of the active part (2), and which is provided with at least one opening (5) that is shaped to enable the circulation of plastic material forming the sleeve (3) when the sleeve (3) is molded over the axle (2a) to ensure the connection of the rotary drive means (4) on the axle (2a).