A screw joint is the junction of two parts held together by a screw (e.g., implant-abutment screw joint). In implant dentistry, the screw joint is an essential part of the implant or prosthesis, however, it is also susceptible to loosening over time. This can cause implant failure at the screw joint. A screw at the screw joint may become loose for several reasons which include incorrect fit of the prosthesis, excessive loading, poor screw design, improper placement, inadequate torque on placement, poorly made prosthesis components, and improper design of the restoration. For those factors which can be controlled by the dental professional, exact adherence to protocols should be maintained to ensure screw joint failure isn’t caused by an error on placement. A basic understanding of the physical forces that act on the screw joint in a prosthesis is extremely helpful for the dental professional as it provides information on how screw joint loosening can occur.