FLIPPER: A "Flipper" retainer typically has 1 or more teeth added as well as 1 set of ball clasps for retention. Although a labial bow or more clasps can be added if needed. This appliance is more esthetically pleasing as now wires show while still maintaining retention.
ESSIX RETAINER: Formed with clear acrylic either heat molded or pressure cooked onto the model and given a horseshoe fit with the arch being cut well below the gingival margin for comfort. Typically there is little to no adjusting on this appliance.