Myofunctional Appliance Therapy: Principles And Practical Steps
Describe the philosophies of action of myofunctional appliances and fabrication of FR2 in detail.
Answer.
Frankel Philosophy of Action of Appliance
vestibular Area of Operation
According to the Frankel, dentition is influenced by perioral muscle function.
- Abnormal perioral muscle function creates a barrier for the optimal growth of dentoalveolar complex.
- Thus, when an appliance is designed to hold away the muscles from dentition, so that the dentoalveolar structures are free to develop.
Sagittal Correction via Tooth Borne Maxillary Anchorage
- Appliance is fixed on the upper arch by grooves mesial to first permanent molar and distal to the canine in the mixed dentition period.
- Presence of the lingual pad acts as postoperative stimulus and helps in the forward posturing of the mandible.
Differential Eruption Guidance
- The Frankel appliance is free of the mandibular teeth
- This allow, selective eruption of the lower posterior teeth in upward and forward directions which contributes to both vertical as well as horizontal correction of malocclusion.
Minimal Maxillary Basal Effect
Downward and forward growth of maxilla seems to be restricted even though lateral maxillary expansion is seen.
Periosteal Pull by Buccal Shield and Lip Pad
Presence of buccal shield and lip pads exert the periosteal pull which helps in bone formation and lateral expansion of the maxillary apical base.
Fabrication of FR2
FR-2 is used for treatment of class 2, division 1 and division 2.
Parts of the Appliance
Acrylic Component
- Buccal shields
- Lip pads
- Lower lingual pads.
Wire Parts
- Palatal bow
- Labial bow
- Canine extensions
- Upper lingual wire
- Lingual cross over wire
- Support wire for lip pads
- Lower lingual springs.
Fabrication Steps
Impression
- Impression should produce the whole alveolar process to the depth of the sulci, including maxillary tuberosities.
- The soft tissues and muscle attachment should be recorded carefully.
Working Model Pouring and Trimming
- Model base must extend away from alveolar process by at least 5 mm.
- Correct model trimming is necessary before appliance fabrication.
- Care must be taken not to disturb the muscle attachments.
Trimming for Lip Pads
- 5 mm from greatest curvature of alveolar base to ensure optimum extension.
- Lower relief should be 12 mm below gingival margin.
Trimming for Buccal Shield
Sulcus depth must be 10 to 12 mm above the gingival margin of posterior teeth.
Construction Bite
For minor sagittl problems, the construction bite is taken at end-to-end incisor relationship, with the mandible position forward not more than 2.5 to 3 mm.
- A clearance of at least 2.5 to 3.5 mm in the buccal segment is necessary to allow the crossover wires to pass through in Frankel appliance.
Wax Relief
- Relief is placed such that the buccal shields and lip pads stay away from teeth and tissues to achieve the desired expansion.
- Thickness of wax depends on the expansion required but should not exceed 4–5 mm in the tooth area and 2.5–3 mm in the alveolar area in the maxilla.
- In mandible only 0.5 mm of relief is given.
Wire Components
Wire components are fabricated and adapted as well as secured in place with sticky wax.
Lower lingual support wire
- Made of 1.25 mm wire.
- Horizontal reinforcing wire element contour to the lingual apical base 1-2 mm away from the mucosa and 3-4 mm below the gingival margin so as to permit adding acrylic to the pad.
Lower lingual springs
Made of 0.8 mm wire.
Lower labial wires
- Made of 0.9 mm wire.
- Act as a skeleton for lower lip pads.
Palatal bow
- Made of 1 mm wire.
- Should have a curve in the center for lateral expansion.
Labial bow
- Made of 0.9 mm wire.
- Should be 2 mm away from mucosa.
- Originate in buccal shield.
Canine loops
- Made of 0.8 mm wire.
- Embedded in buccal shield at occlusal plane level.
Upper lingual wire
- Made of 0.8 mm wire.
- It is used if the centrals are retroclined.
Acrylic Parts
- The lip pad, buccal shields, lower lingual pads are fabricated in cold cure acrylic.
- Total thickness of the acrylic should not exceed 2.5 mm.
- Lip pads should be 5 mm from the gingival margin.
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