Smiles Orthodontic Practice recommends the teeth be permanently retained once the orthodontic treatment is complete. This is achieved by bonding permanent retaining wires (small metal wires) behind the upper and lower six front teeth and wearing clear upper and lower removable retainer plates at nights.
Retention is a life time requirement to ensure your teeth do not move, so ideally the wires should remain bonded behind the upper and lower six front teeth permanently and the plates should be worn every nightly for the rest of your life.
Below are photos of the retaining wires and clear removable plates.