Intrusion phenomena in implant therapy

This article reviews the literature dealing with the combination implant-to-natural-tooth supported fixed partial denture and various theories of intrusion phenomena. The restoration of masticatory function with a combination implant-to-naturaltooth fixed partial denture is associated with a variety of undesirable clinical sequelae, mainly intrusion. One of the first theories was based on the idea that a lack of normal stimulation of the periodontal ligament produces atrophy of the periodontal ligament and intrusion of the tooth. The remaining theories relate to excessive forces being placed on the natural tooth, resulting in movement of the tooth to a less stressful position.