Fixed retainer success is reported to increase with passive adaptation of the retainer wire to the tooth surface. Flexible wires minimize bond failures by reducing stress concentration inside the bonding compound; therefore, to maintain natural tooth mobility, the ideal fixed orthodontic retainer should be passive and semi-rigid. The number of strands of wire, the location of the wires, the diameter of the wire, its flexibility, as well as the bonding strength with composite, are the key determinants of the success of these fixed retainer
