Abstract: A system for tooth implantation having an implant part to be set into the jawbone, and an abutment part to which a tooth restoration is attached. The abutment part is screwed onto the implant part by an abutment screw, and a locking screw is disposed to lock the abutment screw to secure the abument part to the implant part to prevent loosening of the abutment. The threading interface between the lock screw and an abutment channel is matched in spiral direction but mismatched in thread timing with an interface between said abutment screw and an implant channel, thereby generating radial and axial locking forces.