To qualify the contribution of the periodontal-ligament receptors to trigeminal inhibitory reflex responses, 20 subjects with maxillary implant-supported fixed prostheses opposing mandibular teeth or implants were compared to 10 subjects with removable dentures in the maxilla opposing implant-supported prostheses and 10 subjects with natural teeth in both jaws. Standardized mechanical taps were delivered to an implant, a denture tooth, or a natural tooth in the central incisor region of the maxilla. Bilateral surface electromyographic recordings of the masseter muscles were obtained while subjects maintained a constant myoelectric activity by clenching. Stimulation of an implant in partially edentulous subjects elicited a reflex response in 7 of 10 subjects. Likewise, stimulation of a tooth of a maxillary removable denture resulted in a clear reflex response in 5 of 10 totally edentulous subjects. On the other hand, a reflex response did only occur in 1 of 10 totally edentulous subjects with implant-supported prostheses in both jaws. It was concluded that the presence of some natural teeth in either the maxilla or mandible allowed the occurrence of a reflex response. In totally edentulous subjects, mucosal or periosteal mechanoreceptors, triggered by stimulation of the denture bearing area or by transmission of vibrations through the jaw bone, could be responsible for the remaining reflex responses. Keywords: masseteric reflex, oral implants, osseointegration, silent period