Abstract: This invention takes advantages of color characteristics of medical devices for the cosmetic and indication purposes. For example, the appearances of the metallic brackets used in orthodontics are improved with colors other than the original metallic color by surface treatment using plasma techniques. For example, orthodontic brackets are made with piezochromic materials. When the archwire's torsion and bending forces are fading due to the movement of the teeth, the color of the pressure sensitive brackets will be changed, and the need of archwire's readjustment to have proper torsion and bending forces is signalized. For example, rehabilitation equipments are made with piezochromic materials. When the pressures exerting on the rehabilitation equipments are different, different colors of the equipments are displayed, and the therapists can then act accordingly.