For Class II treatment there exist “1001” functional appliances on the market. Their mode of action is, however, a mystery. There are “1001” opinions”.

Of the many open questions in functional appliance therapy that have been discussed over the years, the following should be mentioned: What is actually a functional appliance? Is it an appliance that works by muscle function or does it change muscle function? Are only removable loose fitting appliances functional appliances? Can a fixed bite jumping device be denoted a functional appliance? What about the construction bite? Shall it be high or low? Should the mandible be advanced in one large step or in several small steps?

Furthermore, clinicians and researchers disagree on the effects of functional appliances. Can functional appliances stimulate mandibular growth or are their effects restricted to the dentoalveolar area? Do they work in subjects with an unfavourable growth pattern? Can the basic growth pattern be altered by functional appliances?

Finally, controversies exist about the efficiency of functional appliances and their long-term outcome. When is the best time for treatment? Is the treatment result stable or is it prone to relapse?

The paper aims to uncover the mystery of functional appliances by referring to the existing scientific evidence that can be accepted as valid.

CURRICULUM VITAE: Hanz Pancherz

Hans Pancherz , DDS, Odont. Dr. received his dental and orthodontic education at the University of Lund, Sweden. From 1975 to 1985 he was Associate Professor at the Orthodontic Department in Malmö. From 1985 to 2005 he was Professor and Chairman of Orthodontics at the University of Giessen, Germany. He is honorary member of the Orthodontic Societies of Hong-Kong, South Africa and Columbia and has served as Visiting Professor in Hong Kong 1996 and 2007. Professor Hans Pancherz is particularly interested in clinical-experimental research. His main contribution has been in the field of electromyography, cephalometric roentgenography and magnetic resonance imaging, analysing the short- and long-term effects of removable and fixed functional appliances on the skeletofacial structures. He is an internationally recognized lecturer and has published more than 140 papers and a number of book chapters.