|Year : 2015 | Volume
| Issue : 5 | Page : 33-41
Functional jaw orthopedics for Class II malocclusion: Where do we stand today?*
OP Kharbanda1, S Chaurasia2
1 Professor and Head, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India
2 Former Postgraduate Student, Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||21-Nov-2015|
|Date of Acceptance||22-Nov-2015|
|Date of Web Publication||10-Dec-2015|
O P Kharbanda
Division of Orthodontics and Dentofacial Deformities, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
Class II malocclusion may present with skeletal features of mandibular retrognathism, midface protrusion, and dental features of distal step molar relation, an unusually large overjet and/or variable combination these features. With a variety of craniofacial morphology associated with Class II malocclusion, the type of functional appliance (FA) to choose and the timings of treatment are fundamental to treatment outcome and prognosis. Mandibular retrognathism has befallen to be the most universal rationale for availing orthodontic treatment. Europeans have traditionally tried to grow locked mandible in young children efficiently by jaw propulsors, collectively termed as FAs. FAs have come a long way since the introduction of "bite-jumping" appliance by Norman Kingsley with gradual evolution of these appliances through monobloc, activator, Frankel, bionator, twin block appliance and fixed functional appliances which can now be attached to facial skeleton with implant anchorage. Although timing of treatment, mode of their action, treatment benefits and mechanism of craniofacial adaptation have been researched extensively, the subject of FA has always been a matter of discussion with conflicting views. This paper provides an up to date gist of functional jaw orthopedics for Class II malocclusion.
Keywords: Class II malocclusions, functional jaw orthopedics, skeletal malocclusions, TMJ remodeling, twin block
|How to cite this article:|
Kharbanda O P, Chaurasia S. Functional jaw orthopedics for Class II malocclusion: Where do we stand today?*. J Indian Orthod Soc 2015;49, Suppl S1:33-41
|How to cite this URL:|
Kharbanda O P, Chaurasia S. Functional jaw orthopedics for Class II malocclusion: Where do we stand today?*. J Indian Orthod Soc [serial online] 2015 [cited 2019 Apr 26];49, Suppl S1:33-41. Available from: http://www.jios.in/text.asp?2015/49/5/33/171198
| Introduction|| |
This manuscript is aimed to address the following controversies supported with current evidence on,
Malocclusion is seen to be associated with adverse physical, psychological, and social effects including longevity of dentition and oral health and therefore adversely affects the quality of life (QOL). Direct effects of malocclusion include unesthetic dental and facial appearance leading to poor social image and psychological disturbances. Other indirect effects of malocclusion are proneness to periodontal diseases and increased susceptibility to dental caries and trauma to protruding incisors.
- Which cases are most suitable for FA therapy
- What are the best timings for FA therapy?
- Is there any advantage with early treatment?
- What are the indications of FA?
- When not to give an FA?
- What is the mechanism of craniofacial adaptation?
- Can condyle glenoid fossa (CGF) be altered with FA?
- Obstructive sleep apnea (OSA) and FA.
When the esthetics is compromised, a person may develop a negative body image and psychological disturbances, which could manifest as poor performance in school, poor interpersonal and workplace relationship, lost job opportunities, poor matrimonial alliance, and so on. The adverse effects of poor facial esthetics, motivating a person to seek orthodontic treatment can be broadly divided into low self-esteem and maladjustment, restriction of social activities, and adverse occupational outcomes.
A person's oral health-related QOL can be further affected due to compromised functions of the oral cavity such as mastication, respiration, and speech.
| Nature and Variants of Class II Malocclusion|| |
Class II malocclusion comprises a group of specific skeletal, dental, and facial features exhibiting mandibular retrognathia. In general, Class II malocclusion is synonymous with distal position of the lower molar/mandible or protrusion of the maxilla and maxillary teeth or a variable combination. Moyers classified Class II malocclusion into six horizontal types and five vertical types describing possible dental and skeletal features of Class II malocclusion out of which two such interesting types being associated with retrognathic maxilla.  The Class II malocclusion is the second in frequency, distribution, and prevalence among Angle's malocclusion classes. However, it is the most frequently encountered and treated malocclusion in orthodontic practice.  [Table 1] lists some studies on prevalence of Class II malocclusion.
A study identified 5 distinct clusters depicting the most common phenotypic characteristics found in the Class II malocclusion and had produced seven components that help to explain the most important features of Class II malocclusion. 
Class II Division 1 malocclusion has several forms of presentation the one close to Class I and other of extreme type of maxilla-mandibular dysplasia. In between the two extremes, a large variety of Class II pattern exists which has sagittal, vertical, and transverse deviations of skeletal forms and dental variations.
Class II malocclusion may present as familial tendency or as a consequence of adverse environmental influences or both. Literature shows that airway obstruction during early years of life is associated with mouth breathing that may lead to abnormal craniofacial development, jaw deformation, and malocclusion while nasal respiration promotes normal craniofacial growth. Dentists who get the opportunity to encounter children at early ages should evaluate both craniofacial form and function and if found anything abnormal, should seek consultation with ENT surgeon and an orthodontist. Research has shown that early orthodontic and orthopedic treatment do positively affect airway and promote normal breathing for a healthier life. In addition to obstructive breathing, thumb sucking, lip biting, and other functional causes have been linked to restrain normal growth of the mandible. Such Class II patients also have aberrant behavior of the muscles of the face and stomatognathic system, which requires timely interventions.
| What is Functional Jaw Orthopedics?|| |
The forward growing maxilla can be intercepted during mixed dentition utilizing orthopedic forces in the right direction. Kloehn headgear with face bow was once very popular appliance in North America for restraining the forward growth of the maxillary skeletal base.
Young growing patients who have skeletal and dental Class II relations are considered for early treatment for improvement in sagittal jaw relations and harmonization through a process of growth modulation of dentofacial structures. Though the process appears to be simple, it requires a detailed clinical evaluation, case selection, designing of a comprehensive treatment plan and forecast of remaining growth for prediction of prognosis. This field of orthodontic therapy has emerged as the science of functional jaw orthopedics.
An essential approach to interception of Class II malocclusion involves redirection of the growth to a favorable pattern and elimination of aberrant muscle behavior and/or deleterious habits, thereby allowing the face, jaws and occlusion to grow in normal occlusion. Other modes of treatment for Class II patients are orthodontic therapy, camouflage, and surgery.
Dentofacial orthopedics helps in creating harmony and balance of the teeth-bearing facial skeleton through growth enhancement of the mandible, growth restraint on the maxilla, or a combination of both. Such treatment in growing children can produce significant changes compared to orthodontics alone. Its capability to enhance sagittal repositioning of the mandible brings about changes in oral cavity volume and skeletal bases, besides dentoalveolar structures. In general, overjet up to 12-15 mm is correctable with orthopedic appliance during the growing stage.
FA envelopes an assortment of removable appliances designed to influence the function and position of the mandible by amending the arrangement of various muscle groups so as to redirect forces to the dentition and the basal bone. Therefore, by altering the mandibular position sagittally and vertically, muscular forces are engendered resulting in orthodontic and/or orthopedic changes. 
The original concept of functional jaw orthopedics essentially encompasses growth modulation for the correction of mandibular retrognathia, i.e., skeletal Class II malocclusion not only by active forces of appliance but also by the forces generated from the muscles when the mandible is held forward. The functional forces indirectly produce growth modulation and bring about changes in jaw bones and hence the term "functional jaw orthopedics." The term has now been applied for any device that is used to displace and hold the mandible, which includes a variety of removable functional (FA) and fixed functional appliances (FFA).
Dentofacial orthopedics involves a variety of treatment modalities that are adapted to create a harmony and balance of occlusion and facial skeleton through growth enhancement of the mandible, growth restraint of the maxilla, or a combination of both. These therapeutic modalities such as Kloehn face bow, activator-headgear combination include use of orthopedic forces (≥450 g) in combination with functional growth stimulation and orthodontic forces to affect skeletal and dental alterations.
FAs help in furthering the growth of jaw bones and thereby correct malocclusion when the mandible is small or retrognathic or positioned backward. They stimulate and regulate perioral muscles and muscles of stomatognathic system thereby creating favorable environment for the growth of facial bones and dentition. Enhanced function of the stomatognathic system brings about orthopedic changes, the philosophy which was founded by Adresen and Haupel. , The use of FA or an orthopedic approach is only a device to achieve growth modification, which in most of the instances is a part of a comprehensive treatment plan.
In modern day, clinical practice, any appliance or device that is used to restrain or enhance growth of the maxilla-mandibular skeleton is grouped as FA. A variety of devices are now used in conjunction with fixed appliance or attached to miniscrew or miniplates are called fixed functional appliances (FFAs).
| Case Selection|| |
FA selection is governed by a number of factors, which include skeletal and dental age of the patient, severity and location of dysplasia, craniofacial pattern, presence of aberrant muscle pattern, traits of malocclusion, and planned sequence of treatment besides operator's choice and experience in handling the appliance. The outcome of the FA phase of treatment may vary from case to case.
A comprehensive planning for FA therapy includes pretreatment records such as study models, intra- and extra-oral photographs, lateral cephalogram, and a panoramic radiograph. Additional X-rays may be required: These include, intraoral periapical/occlusal X-ray and a posteroanterior cephalogram.
FA treatment is indicated in growing patients with Class II Division 1 malocclusion or less often for Class II Division 2 malocclusion. FAs are also considered for correction of Class III malocclusion, especially those due to functional forward shift of the mandible.
Growing children having a normal maxilla with convex profile due to small, retropositioned mandible, and an average or a horizontal type of growth pattern of the face are suitable cases for FA therapy. They may show narrow maxilla and large overjet, which could be the outcome of severe thumb sucking, abnormal pattern of breathing, or lip sucking habit.
Removable FAs are indicated in young patients who are yet to reach peak height velocity (PHV) or pubertal growth spurt. In general, pubertal growth spurt in girls is seen around 10-14 years and about 12-16 years in boys. Class II correction with FA is expected to produce more favorable skeletal effects in children treated just before peak compared to those during or slightly after the onset of the pubertal peak in growth velocity. 
Skeletal maturation can be assessed with hand-wrist radiograph or a cephalogram. Cervical vertebra maturation index (CVMI) is now being increasingly used to assess remaining skeletal growth using a lateral cephalogram. The CVMI method is simple, reliable and omits need for additional hand-wrist radiograph.
Children with good prognosis show a positive visual treatment objective i.e., improvement in facial profile when asked to bring the lower jaw forward.
Lateral cephalogram should be visually evaluated prior to comprehensive cephalometric analysis. Children who have small and retropositioned mandible, have cephalometric parameters suggestive of horizontal or normal growth pattern, and are associated with normal inclination of the lower incisors are considered cases with good prognosis. Some patients need prefunctional phase of treatment. These are patients with retroclined upper incisors or severe crowding that hinders forward positioning of mandible. [Table 2] gives a summary of significant features for case selection for FA therapy.
One important parameter to keep in consideration is the age of starting the FA therapy. There is still a controversy regarding the suitable age for the management of Class II malocclusion. Most orthodontists worldwide consider that early treatment done during the beginning of mixed dentition is far more efficacious than treatment done afterward in the permanent dentition.
|Table 2: Case selection and treatment planning in Class II Division 1 cases for functional appliance treatment |
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| What is the Best Age for Functional Appliance Therapy?|| |
There is no universal agreement on exact age and physical growth status on the FA therapy. Based on research and clinical experience, certain guidelines are available for the age of starting the FA treatment.
In general, there is a consensus that FA treatment should be started before adolescence in the early permanent dentition followed by a phase of fixed appliance therapy (one-phase treatment in continuation though split into a phase of functional therapy followed by fixed appliance therapy) or two-phase treatment which is started during early mixed dentition which follows a maintenance phase until eruption of all permanent teeth. A fixed appliance therapy is then instituted to finish and detail the occlusion. The clinical efficacy of one-phase treatment started during adolescence in the early permanent dentition might be nearly equivalent to that of a two-phase treatment started much before adolescence in the early mixed dentition. Since early treatment produces no reduction in the average time, a child is in fixed appliances during the second stage of treatment, and it does not decrease the proportion of complex treatments involving extractions or orthognathic surgery; therefore, efficacy of early treatment remains questionable. 
Early treatment can benefit by helping the children to get rid of teasing in school, by reducing proneness of maxillary anterior teeth to trauma and control of aberrant oral habits. However, in other situations, it may be seen as undue prolonged treatment, which in many instances causes premature termination of treatment. This can be attributed to patient/parent "burn out."  The orthodontist has to weigh the real benefits of early treatment and logistics of finances and administration of the therapy.
There are no apparent identifiable differences in the final treatment outcome between one phase and two phase treatment therapies. Subjects who receive treatment in two phases, with the first aimed at orthopedic correction in the mixed dentition and the second detailing the permanent dentition, as compared to those who receive one-phase of treatment in the early permanent dentition do not show significant skeletal or dental differences. By the conclusion of full orthodontic treatment, there is momentary skeletal change as a result of phase I treatment with both appliances, but no detectable skeletal difference were seen between one phase and two phase treatment of Class II malocclusion. 
| Bite Registration|| |
The philosophy of FA is based on jumping the bite by holding the mandible in a forward position. Extent to which mandible should be brought forward and how much it should be brought downward in vertical direction is still a matter of debate.
Horizontal extent of the bite registration is largely governed by the amount of overjet and the degree of the upper incisor proclination and their possible retraction during treatment. The maximum forward movement of the mandible up to 10 mm can be managed with single activation. The activation must not exceed 70% of the total protrusive path to remain within physiological limits of movement of the mandible. However, if overjet is very large such as 14 mm or more, the mandible is advanced in a stepwise manner more often in two stages. 
The extent of vertical opening is dependent upon the nature of malocclusion and craniofacial growth trend. If the forward positioning of the mandible is 10 mm or 7-8 mm, the vertical opening must be slight to moderate, i.e., 2-4 mm so as not to overstretch the muscles. If the forward positioning is not more than 3-5 mm, the vertical opening could be more up to 4-6 mm. Greater vertical and less sagittal activation is done in vertical growth type while normal/horizontal growers receive more activation that is horizontal.
Noncoincident midlines may have varied etiology that need to be ascertained to determine its possible impact on recording the bite. Midline shift can occur due to pure dental causes such as asymmetrical loss of deciduous canines or functional shifts. Dental midline shift should not be corrected during bite registration.
A case with a Class II malocclusion due to retrognathic mandible treated with removable FA (twin block appliance) followed by fixed mechanotherapy is illustrated in [Figure 1] [Figure 2] [Figure 3] [Figure 4] [Figure 5] [Figure 6] [Figure 7] [Figure 8] [Figure 9], and cephalometric measurements are shown in [Table 3]. Sequence of events and protocol of treatment used at AIIMS is given in [Table 4].
|Table 4: AIIMS protocol for records and treatment follow up with functional appliance |
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| How Effective are Functional Appliance and How Do They Work|| |
The temporomandibular joint (TMJ) of young individuals can adapt to positions acquired by mandible when it is held by the bite jumping appliance. An FA induces skeletal growth modifications when used during periods of active growth of a child before or during occurrence of puberty or PHV. ,
To understand mechanism of adaptation and behavior of muscles of stomatognathic system, electromyography (EMG) studies have been carried, out mostly to record activity of lateral pterygoid, anterior temporalis, masseter and digastric muscle. Some of the studies are supported with serial cephalometric and EMG recordings.
Current thinking on effectiveness of FA is not only limited to the measurement of the enhanced length of the mandible alone on two-dimensional cephalograms but also includes improvement in overall volume of the oral cavity, that is, housing the dentition, oral structures such as position of tongue and soft-tissue drape around face as assessed from three-dimensional images. Forward mandible placement is also being seen as an improvement in the lip seal and improved pattern of breathing. Following insertion of sagittal repositioning appliance, mandible is postured forward and lowered to allow maintenance of airway by altering tongue position and this is beneficial in patients with mild to moderate sleep apnea.
Magnetic resonance imaging illustrated the changes in and around the CGF complex as forward relocation of the CGF complex after FA therapy while the internal anatomic arrangement within the TMJ complex normalized to pretreatment stage. 
Histological and histochemical studies on condyle and CGF have been conducted following forced mandibular propulsion by experimental studies in rats,  rabbits,  sheep, , pigs,  and nonhuman primates. ,,, In growing animals, forward displacement of the mandible initiates compensatory adaptive changes at the condylar head marked by its enhanced growth and change in the direction of growth. The facial skeletal adaptations occur through a composite of adaptations in the mandible, CGF, and nasomaxillary complex to new altered position of the mandible. The extent and direction of growth of the mandible are altered while horizontal and vertical displacement of the maxillary complex is affected.
CGF complex has been extensively studied with cephalograms, orthopantomograms, tomograms, bone scintigraphy using radiologic markers such as 99mTc-methy diphosphonate, and computed tomography scanning in patients undergoing FA therapy. ,,,,,,,, Experimental studies by Voudouris et al. have reported CGF remodeling at the condyle and the glenoid fossa which correlated with decreased postural EMG activity during the experimental period. 
Voudouris and Kuftinec showed that displaced condyle from condylar fossa leads to extrinsic signals from tissues surrounding it which serve as stimulus to the fibrocartilage on the head of the condyle to undergo growth modification following growth of soft tissues.  His hypothesis laid the foundation for "growth relativity theory."
Cellular and molecular alterations in condyle
Newer research at the molecular level has provided some insight on the process of enhanced cellular growth and genetic alterations in the cells in condylar cartilage. These cells respond to strain, viscoelasticity, or such unknown stimuli that send signals to mesenchymal cells differentiation in the articular layer in chondrocytes, which proliferate and mature into hypertrophic cells.
Contemporary research has shown that insulin-like growth factor 1 (IGF-1), fibroblast growth factor 2 (FGF-2), and their receptors (IGF-1r, FGFr1, 2, 3) show enhanced expression, which after alteration in mandibular posture, might to a certain extent contribute to changes in proliferative activity of condylar cartilage.  New bone formation was preceded by increased neovascularization indicated by increased expression of vascular endothelial growth factor.  Higher levels of parathyroid hormone-related peptide (PTHrP) expression have been seen to coincide with the reduction in the rate of chondrocyte hypertrophy. It was therefore concluded that advancement of mandible promotes mesenchymal cell differentiation and trigger PTHrP expression, which lead to slowing of their further maturation to allow for more growth. 
A significantly increased expression of type X collagen,  Sox9,  Ihh  were also observed during mandibular protrusion. However, much more information is awaited on precise control of growth alterations, which once known could prove useful to the clinicians in the manipulation of jaw growth to the best of advantage for the patients with smaller jaw.
Although research studies have questioned the efficiency of FA treatment, their clinical performance has been the reason for their continued and expanding popularity in the treatment of developing Class II malocclusion. The case selection, appliance design, rigorous follow-up and favorable growth are key factors that determine the success of FA therapy.
| Growth Modification with Functional Appliances Anchored with Skeletal Anchorage System|| |
FFAs are now being modified in design to be used in conjunction with skeletal anchorage system and temporary anchorage devices. Clinical reports have shown significant skeletal benefits with untoward dental movements since no anchorage is required from dental units in this form of therapy. , The cost and surgical intervention seem to be the major deterring factor in their use.
| Summary|| |
Declaration of patient consent
- Class II malocclusion is one of the most common reason for seeking orthodontic treatment
- Developing Class II malocclusion of skeletal origin can be intercepted and treated with functional jaw orthopedics
- In favorable cases, institution of FA therapy can bring about positive benefits
- FA therapy brings about change in oral volume and volume of the upper airway thereby improving OSA
- Serious research using advanced techniques of molecular biology can unfold the mechanism of CGF complex adaptation.
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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| Authors|| |
Professor OP Kharbanda is CHIEF, Centre for Dental Education and Research and Head, Division of Orthodontics and Dentofacial Deformities, at All India Institute of Medical Sciences, New Delhi. He is also CHIEF of the Centre for Medical Education and Technology at AIIMS. Dr. Kharbanda earned his BDS (1976) with several awards and honours from King George's Medical College, Lucknow followed by MDS Orthodontics from the same university. Later he completed his M Orth RCS (Edinburgh) and Masters in Medical Education (M MEd) from University of Dundee, UK. He received training in Cleft Lip and Palate as a British Commonwealth Fellow at Manchester in 1995-96 and later as a Visiting Scholar of American Cleft Lip, Palate and Craniofacial Association. Dr. Kharbanda is renowned for his teaching and research skills and as an outstanding clinician. He has published extensively in peer reviewed journals of repute, including a text book entitled 'Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities' (Elsevier). Dr. Kharbanda is a former Chief Editor of Journal of Indian Orthodontic Society and served/es International Editorial Board/Peer Review of American Journal of Orthodontics and Dentofacial Orthopedics, Journal of Orthodontics, Australian Orthodontic Journal, Journal of Clinical Pediatric Dentistry, The Angle Orthodontist, Orthodontics & Craniofacial Research and Orthodontic Journal of Nepal besides several Dental speciality journals in India. His main research interests are: Non-extraction treatment, outcome of Functional Appliances more so muscle dimensions, 3D Imaging modalities, and treatment outcome in Cleft Patients. Since 2004 he has been aggressively involved in clinical and fundamental research on host and implant related factors contributing to the success of orthodontic miniscrew implants. Currently he is supervising PhD thesis on surface modification of titanium with biomolecules to achieve better gingival adaptation at neck of orthodontic miniscrews and two collaborative PhDs on automation in 3D volumetric imaging.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2], [Table 3], [Table 4]