An occlusal system that does not function well, has a negative impact on the functional level of the oral system and the orofacial system. In purely mechanical terms, a limited anatomical reduction of the occlusal system has limited implications for the functional level since the occlusal system has several forms of adaptation, reserve, and compensation. However, following the loss of (parts of) teeth, an occlusal system may be anatomically reduced to such an extent that restoration of the functional level is required, for instance by the use of implant-supported single- and multiple-unit fixed dental prostheses. The mechanical strength of a tooth and a single-tooth fixed dental prosthesis on a similar tooth type is not essentially different. But the same cannot be said of the mechanical strength of a multiple-unit fixed dental prosthesis, because the strength is controlled by the mechanoreceptors in the periodontal ligaments of the abutment teeth. This control system is disturbed by the insufficiency of or, when oral implants are involved, the absence of mechanoreceptors. It is unknown whether this is causing noticeable problems.