Abstract A stereognostic ability test was performed in 60 patients. Forty patients were rehabilitated by means of osseointegrated implants. One group consisted of 20 pa- tients with fixed prostheses on implants in both the upper and lower jaws. The other 20 patients had a maxillary den- ture while in the mandible an overdenture was retained by means of two implants connected by a bar. They were com- pared to a group of 20 subjects (controls) with a non-re- stored natural dentition. For the stereognostic ability test, subjects had to recognise ten different test pieces by ma- nipulating them with two antagonistic incisor teeth, avoid- ing any contact with other oral structures. Both response time and percentage accuracy of recognition were evalu- ated. The present findings indicated that subjects with an overdenture on implants did not score significantly differ- ent from those with an implant-supported fixed prosthesis. In contrast, subjects with teeth had a significantly better stereognostic ability. The percentage of correct responses was 52% for overdentures, 56% for fixed prostheses on im- plants and 75% for natural dentitions. From these results, it could be concluded that the stereognostic ability is im- paired in subjects rehabilitated with osseointegrated im- plants by about one-third to one-quarter compared to sub- jects with natural teeth. Key words Oral · Stereognosis · Tooth · Implant · Prosthesis Introduction To evaluate oral sensorimotor function of a patient, psycho- physical studies can be carried out determining tactile threshold levels [8], oral stereognostic ability (OSA) and oral motor ability [1, 14]. An OSA test provides informa- tion regarding the ability to recognise and discriminate dif- ferent forms. Oral stereognosis is considerably more com- plex than the previously mentioned detection of tactile stim- uli. It consists of a processing of numerous sensory impulses in higher brain centres and, rather, reflects oral sensory func- tion, since it is less dependent on general stereognosis [11]. From a methodological point of view, OSA tests have been performed in different ways with different outcomes. An appropriate psychophysical methodology has some- times been neglected. Furthermore, a variety of materials, forms and sizes has been applied (Table 1). Besides the strictly methodological factors, a number of other variables should also be controlled. Age-related effects are well documented with regard to OSA tests [1, 20]; gender seems less important [22]. Many authors [1, 3, 15, 23] reported a significant influ- ence of dental status on OSA. Garrett et al. [4], however, found no difference in the results between dentate subjects and denture wearers. Others [4, 20] stated no significant difference in OSA scores between good and poor denture retention. Lundqvist [16] was the first to investigate OSA in pa- tients before and after rehabilitation with full fixed pros- theses on osseointegrated implants. Patients seemed to per- form better with fixed prostheses on osseointegrated oral implants than with their previous complete dentures. The purpose of the present study was to investigate the stereognostic ability in patients with oral osseointegrated implants in comparison to dentate subjects. This might con- tribute to a better understanding of the receptor groups in- volved in oral sensorimotor function in patients with en- dosseous implants. Materials and methods Subjects A cross-sectional study was carried out on 60 patients (37 females) without known neurological disorders or craniomandibular dysfunc- Clin Oral Invest (1997) 1: 89–94 © Springer-Verlag 1997 Reinhilde Jacobs · Charbel Bou Serhal Daniel van Steenberghe The stereognostic ability of natural dentitions versus implant-supported fixed prostheses or overdentures ORIGINAL ARTICLE R. Jacobs () · C. Bou Serhal · D. van Steenberghe Laboratory of Oral Physiology, Department of Periodontology, Faculty of Medicine, Catholic University of Leuven, Capucijnenvoer 7, B-3000 Leuven, Belgium Tel.: +32 16 33 24 10 (29.51); Fax: +32 16 33 24 84 e-mail: reinhilde.jacobs@med.kuleuven.ac.be