Masseter muscle fatigue during sustained clenching in subjects with complete dentures, implant-supported prostheses,...

A sustained submaximal (50%) clenching effort was performed in four patient groups to establish whether implant-supported prosthetic reconstructions influence myoelectrical signal parameters. The first group consisted of patients with natural teeth in both jaws. The other three groups consisted of patients who were edentulous in both jaws: one group had complete dentures; one had an overdenture in the mandible on two implants connected by a bar; and the third had an implant-supported fixed prosthesis in either the maxilla or the mandible. Surface electromyography indicated an increased myoelectrical output level that paralleled a higher bite force level for implant-supported reconstructions compared with complete dentures. Power spectrum analysis revealed a downward shift of the mean power frequency during sustained clenching in all groups except the implant-supported fixed prosthesis. The absence of a spectral shift in the latter group probably reflected a fear of biting too hard and fracturing the prosthesis.