Introduction
- History
- Brief Introduction of Growth of Dentofacial Complex
Assessment/Application of Knowledge of Growth
Timing of Treatment
Bite Registration
General Mechanism of Action of FOA
Classification
Components of Functional Appliance
Clinical Considerations/Applications in Making a Choice
- Acceptability
Advantages/Limitations
Appliance Wear/Patients Review and Follow-up
Conclusion
Introduction
Malocclusion is associated with adverse physical, psychological, and social effects, which include reduced longevity of dentition and compromised oral health. Consequently, it adversely affects the overall quality of life (QOL). Many malocclusions are of skeletal origin. Unfortunately, traditional fixed appliance therapy and conventional removable appliances may have limited efficacy in these cases.
Functional Orthodontic Appliances (FOA) utilize muscle function, tooth eruption, and growth to correct malocclusions. They are distinct from other orthodontic treatments as they can modify skeletal malocclusions effectively.
History
Functional appliances can trace their origins back over a century. In 1902, Pierre Robin described a simple monobloc appliance aimed at treating mandibular retrognathia. Later, Viggo Andresen modified this design while working in Oslo, notably using a retainer to guide the mandible into an ideal inter-arch relationship during his daughter's fixed appliance therapy.
Understanding the Growth of the Dento-Facial Complex
To effectively intervene orthodontically, it is crucial to understand the growth and development of the dentofacial complex. The major systems involved in malocclusion include:
- Skeletal System (Bone)
- Muscular System (Muscle)
- Dental System (Tooth)
About two-thirds of individuals seeking orthodontic treatment have skeletal and dental dysplasia. Timely intervention can prevent these dysplasias.
Growth Patterns
The significant increments in growth occur during specific periods:
- Girls:
- First Peak: 3 years
- Second Peak: 6-7 years
- Third Peak (Pubertal): 10-14 years
- Boys:
- First Peak: 3 years
- Second Peak: 7-9 years
- Third Peak (Pubertal): 12-16 years
To achieve maximum changes in skeletal configurations, treatment must occur during these peak growth periods.
Patient Assessment/Application of Knowledge of Growth – Skeletal
Functional appliances are most effective in growing patients, modifying jaw dimensions. Key markers to confirm optimal timing for treatment include:
- Patient's history indicating they are yet to reach peak height velocity (PHV).
- Clinical examination should show a good prognosis based on visual treatment objectives.
Assessing Skeletal Maturation:
Hand-Wrist Radiograph:
- Pre-pubertal Stage: Epiphysis and diaphysis are not fused.
- Puberty: Sesamoid bone appears in the thumb, culminating in the fusion of epiphysis and diaphysis.
Cephalogram:
- Cervical Vertebra Maturation Index (CVMI) aids in analyzing remaining skeletal growth. A good prognosis is associated with normal cephalometric parameters.
Case Selection: The Best Age for Functional Appliance Therapy
While a universal age for FOA treatment is not established, guidelines exist:
- Start either before adolescence in early permanent dentition, followed by fixed appliances.
- Alternatively, initiate two-phase treatment during early mixed dentition with a maintenance phase until the eruption of all permanent teeth.
Though early treatment can mitigate risks such as dental trauma, it may lead to patient burnout.
Bite Registration
The philosophy of FOA centers around positioning the mandible forward (jumping the bite). Parameters for determining the extent of mandibular advancement involve:
- Overjet: Horizontal registration aligned with expected tooth movements.
- Layering of Wax: Accurate impressions, aligned maxillary and mandibular assemblies.
General Mechanism of Action of FOA
Research illustrates how condylar displacement activates surrounding tissues, promoting growth modification via connections to relevant genes. FOA operates through three main methods:
- Tipping Movements
- Eruption Guidance
- Mandibular Reposturing
Each mechanism contributes to optimizing skeletal and dental relationships.
Classification
Functional appliances encompass three categories, as outlined by Proffit (1986):
- Passive Tooth-Borne Appliances – E.g., Andresen appliance.
- Active Tooth-Borne Appliances – Modification of original designs for tooth movement.
- Tissue-Borne Appliances – E.g., Frankel appliance.
Further classification includes:
- Removable: Most functional appliances.
- Fixed: Herbst and Mara appliances.
Components of Functional Appliance
The design of functional appliances involves several components:
- Components for Mandibular Advancement
- Arch Expansion Components
- Vertical Control Components
- Stabilizing Components
Examples of various functional appliances include:
- Andresen Appliance
- Harvold Activator
- Bionator
- Twin Block
- Herbst Appliance
- Frankel Appliance
Clinical Considerations in Making a Choice – Acceptability
The extent of speech interference significantly impacts compliance with wear. Appliances are designed to minimize speech disruption while ensuring effective treatment. Regular checks and adjustments remain vital for monitoring progress and adaptation.
Advantages and Limitations
Advantages:
- Utilizes growth potential for effective skeletal changes.
- Minimal chair-side time and less frequent adjustments required.
- Economical compared to conventional options.
Limitations:
- Precise tooth position control is not achievable.
- Ineffective in adults or those with significant dental crowding.
- Dependence on patient compliance for effectiveness.
Appliance Wear/Patients Review and Follow-Up
Effective wear protocols generally recommend a minimum of 12 hours, primarily in the evening to coincide with peak skeletal growth periods.
Effects of FOA Treatment
Skeletal Effects:
- Forward mandibular growth.
- Restriction of maxillary growth.
Dental Effects:
- Retrusion of maxillary incisors.
- Protrusion of mandibular incisors.
Completion of FOA Therapy
Options include retention with existing appliances or transitioning to fixed appliance therapy for further adjustments.
Conclusion
Functional Orthodontic Appliances play a crucial role in orthodontics, but success hinges upon a thorough understanding of growth patterns and meticulous patient selection.
Bibliography
- Kharbanda OP, Chaurasia S. Functional jaw orthopedics for Class II malocclusion: Where do we stand today?*. J Indian Orthod Soc 2015;49:33-41.
- Dibiase, AT, Cobourne MT, Lee RT. “The Use of Functional Appliances in Contemporary Orthodontic Practice.” British Dental Journal 2015; 3: 123–28.
- Contemporary Orthodontics; Fifth Edition by William R Proffit, Henry W Fields and David M, Sarver.
- DR. O. O. Dacosta. Update of WACS lecture note: "The Title is Functional Orthodontic Appliances."
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