Bluegrass appliances are used to aid in the cessation of a thumb sucking habit. The wire of the appliance contains a small roller that prevents placement of the thumb against the retroincisal area of the palate (Figure 13).37 Crib appliances are made of metal wire and contain a gate-like piece that is used to prevent pressure of the tongue against the anterior teeth during swallowing, while training a correct swallowing pattern (Figure 14).38 A crib appliance can also be used to prevent thumb or finger sucking. Both the bluegrass and crib appliances are non-removable wire appliances that are worn until the habit has stopped or behavior is modified. These devices are typically reserved for difficult-to-correct behaviors, particularly before initiating orthodontics. Patient willingness to change the behavior will be crucial to continued success.