An implantable constriction device for treating an incontinent patient comprises an elongate composite structure adapted to constrict the urethra, urine bladder, anus, colon or rectum of the patient. The elongate composite structure is composed of a base material, such as hard silicone, making the composite structure self-supporting. Property improving material is provided for improving at least one physical property of the composite structure other than self-supporting properties, such as fatigue resistance, liquid impermeability, aggressive body cells resistance, anti-friction properties and lifetime.