W hile there are several descriptions of func-tional orthodontic appli-ances, there is no official consensus on the definition of a functional orthodontic appliance. Moreover, there is a dearth of evidence on the developmental mechanism(s) by which functional orthodontic appliances achieve their effects. This article explores the concept of epigenetic orthodon-tics, which involves osteogenesis, a physiologic process of bone devel-opment during tooth correction. The molecular-morphologic basis of epigenetic orthodontics can be explained by the Spatial Matrix Hypothesis. Clinically, this hypoth-esis is implemented by foundational (skeleto-dental) correction using the DNA appliance TM system, with direct or indirect functional (myo-spatial) correction. These clinical protocols rely upon the natural process of sutural homeostasis, which is encoded by genes, and through which an enhanced level of cranio-facial homeostasis can be achieved. This improvement includes not only better tooth alignment but also dentoalveolar bone develop-ment, as well as facial cosmesis, and optimization of the upper airway dorsal to the craniofacial complex. It is posited that epigenetic orthodontics encompasses the developmental mechanisms by which functional orthodontic appli-ances, perhaps better called forma-tional appliances, achieve their clin-ical outcomes. (BOS), a functional appliance is a removable appliance that works on the upper and lower teeth at the same time. The BOS further states that functional appliances help correct skeletal problems, while the dental problems are corrected with fixed orthodontic appliances. 1 This notion supports to the idea that foundational correction could proceed orthodontic correction with removable appliances such as align-ers. But, other definitions of func-tional appliances can also be found. Some suggest that functional appli-ances are special removable appli-ances, which change the way the teeth and jaws bite together. Note that this definition varies from others 2 they propose that functional “It is posited that epigenetic orthodontics encompasses the developmental mechanisms by which functional orthodontic appliances, perhaps better called formational appliances, achieve their clinical outcomes.” appliances are removable or cemented appliances used to correct excess overjet problems. Yet others 3 believe that functional appliances are a class of removable appliances that utilize the muscle action of the patient to produce orthodontic or orthopedic forces. Indeed, the British Dental Health Foundation 4 suggests that it is sometimes possi-ble to change the way the jaws grow, using functional appliances, and that these appliances use the power of jaw muscles to help with certain types of problems. Kalaf and Mattick 5 also suggest that functional appliances are removable or fixed orthodontic appliances that use forces generated by the stretching of muscles, fascia and/or the periodon-Introduction Functional orthopedics is a term that has been use widely in the orthodontic literature. However, the definition of ‘functional orthope-dics’ varies widely. Thus, it would be wise to examine the terminology associated with this discipline before proceeding to its detailed applica-tions. In addition, many different ‘functional appliances’ are available e.g. Activators, Monoblocs, Twin-blocks, Bioblocks, Bionators, Frankel’s etc. Therefore, one of the first questions to arise is: What is a functional appliance? According to the British Orthodontic Society tium to alter skeletal and dental relationships. Therefore, ostensibly, the effects of stretch during growth and development may be the mode through which functional appli-ances attain their treatment effects, and this idea has been extended to the use of aligners. Although this notion has been referred to as soft tissue stretch 6 , results from perma-nently implanted electromyographic sensors 7 demonstrated that lateral pterygoid muscle hyperactivity is not associated with functional appli-ances. Thus, other factors might play a more significant role in new bone formation. The American Association of Orthodontists 8 suggests that func-tional appliances are used to normalize growth discrepancies between the upper and lower jaw, and that removable orthopedic functional appliances can help correct growth discrepancies. Indeed, Gen 9 suggests that func-tional appliances all have a similar purpose; to help jaws develop normally and achieve facial balance. According to the Canadian Orthodontic Association (COA) 10 functional appliances can be used in growing patients to put the jaws in balance, achieve good facial muscle function and create natural facial proportions. However, the COA asserts that it is essential that orthodontic screening be done at 7 or 8 years of age to ensure that the patient is not too old for functional appliance therapy. However, data is now available that suggests that similar effects can be achieved in so-called ‘non-growing’ adults. 11 The COA further suggests that these appliances can be designed to not only move teeth but also correct the alignment of the jaws, and that the most common objective is to correct an underdeveloped lower jaw. In a similar fashion, the Australian Soci-ety of Orthodontists (ASO) 12 suggests that functional appliances are devices used to correct a signifi-cant disharmony in the relationship between the upper and lower jaws. The ASO further suggests that func-tional appliances work by influenc-ing the growth and development of a growing patient. They suggest that www.orthodontics.com November/December 2010 17
Journal of the American Orthodontic Society November-December 2010: Page 17
