Removable functional appliances are normally very large in size, have unstable fixation, cause discomfort, lack tactile sensibility, exert pressure on the mucous (encouraging gingivitis), reduce space for the tongue, cause difficulties in deglutition and speech and very often affect aesthetic appearance. The alteration in the mandibular posture creates added difficulties. These adverse effects make the adaptation and acceptance of these appliances more difficult.
Fixed functional systems have some advantages over removable systems. They are designed to be used 24 hours a day, which means that there is a continuous stimulus for mandibular growth.
They are smaller in size permitting better adaptation to functions such as a mastication, swallowing, speech and breathing.
Fixed functional appliances are usually described as non-compliance Class II devices, which are able to treat Class II malocclusions successfully, while reducing the need for patient co-operation and overall treatment time. It is possible to treat this type of malocclusion with minimal effort.