To study the oral function of partially edentulous patients treated with fixed prostheses on osseointegrated implants, recordings of the masticatory efficiency and occlusal perception of thickness were performed. The retrievable fixed partial prostheses were used to study the immediate impact of reduced fixed occlusal support on masticatory efficiency. The masticatory efficiency was subjectively satisfactory but objectively lower when compared to naturally complete dentate persons. Furthermore, the immediate impact of reduced fixed occlusal support was compromised masticatory efficiency, which was more pronounced when the occlusal support was removed on either side. Schlagwörter: masticatory efficiency, oral function, osseointegrated implants, tactile sensibility