university of glasgow

Removable orthodontic appliance

Personal note

Dr. Mohammed Almuzian

1/1/2013

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Page 0

Table of ContentsDefinition.............................................................................................................................................2

Advantages..........................................................................................................................................2

Disadvantages......................................................................................................................................2

Indications...........................................................................................................................................2

Mode of action.....................................................................................................................................3

Limitations in the lower arch...............................................................................................................4

Materials used in the construction of RA.............................................................................................4

Wires...................................................................................................................................................4

Stainless steel wire...............................................................................................................................4

Elgiloy wire.........................................................................................................................................4

Acrylic.................................................................................................................................................5

Side effect of monomer........................................................................................................................6

Component of RA................................................................................................................................6

Active Component...............................................................................................................................6

A. Springs.........................................................................................................................................6

B. Bows............................................................................................................................................7

C. Screws.........................................................................................................................................7

D. Elastics.........................................................................................................................................8

Retentive Component..........................................................................................................................8

Advantages of the Adams' clasp..........................................................................................................8

The baseplate.......................................................................................................................................8

Anchorage............................................................................................................................................9

Modified types of removable appliances..............................................................................................9

How components are combined to design an appliance.....................................................................10

The First Fitting of an Appliance.......................................................................................................10

Inspection of RA on recall visits........................................................................................................11

Trouble shooting with RA..................................................................................................................12

A.Teeth doesn’t not move.................................................................................................................12

B. Breakage........................................................................................................................................12

C. Sign of wearing RA...................................................................................................................12

Removable orthodontic appliances

Definition An appliance designed to be easily removed from the mouth by the patient for cleaning and activation where required.

Advantages1. Cleaning.2. Less chair side time.3. Cheaper4. They can transmit forces to blocks of teeth e.g. arch expansion.5. They have good vertical and horizontal anchorage (palatal coverage).

Disadvantages1. Rely very heavily on patient cooperation.

2. They can affect speech.

3. Lower appliances particularly difficult to tolerate.

4. They require a technician.

5. Only tilting movements are possible and thus can generate unwanted tooth movements, particularly rotations when a crown is being translated

6. Poor quality result (Richmond use PAR index in cases treated by RA and found poor result)

7. Inter maxillary traction is difficult.

Indications A.Interceptive treatment

1. active

Correction of anterior crossbites. 2. Correction of posterior crossbites.

3. passive

• Habit breaker4. Space maintenance.

I. Early loss of deciduous teeth. II. Traumatic loss of an incisor.

III. Hold space after extraction of permanent teeth to allow eruption of impacted teeth.

B. Adjunct to Fixed or Functional appliance Therapy.

A.To EOA and functionals1. To procline incisors in a Class II Division 2 case (ELSAA)2. Expand the upper arch.3. Maintain the result of functional appliance (steep and deep)4. Aid distal movement by adding headgear therapy (Enmass) or intrusion of

posterior teeth in Buccal intrusive apliances.

B. To FA1. Overbite correction (in a growing child using an anterior bite plane).2. Open bite correction3. Disengage occlusion with bite planes to enhance tooth movement by removing

occlusal interferences.4. They are very efficient for extruding teeth such as impacted palatal canines.5. Lower RA can provide class II traction in class II malocclusion with straight LA

teeth or a method of attachment during canine extrusion

C.RA as retainer

1. Converted appliance2. 'U' loop labial bow retainer {Hawley)3. Acrylic covered labial bow4. Begg retainer5. Barrer appliance (it look like Inmanligner)6. Vacuum-formed retainers7. Positioner

Mode of action a. Passive actions

1. As space maintainer

2. Spontaneous alignment of teeth after provision of the space for the adjacent crowded or malposed teeth.

b. Active movement

1. Crown tipping 2. Crown rotation (very limited)3. Absolute Intrusion of anterior teeth by anterior bite plate 4. Relative Extrusion of post by ant bite plane

Limitations in the lower arch 1. Bulkiness

2. Poor retention

3. The considerably reduced area available for active components

Materials used in the construction of RA

Wires

Stainless steel wire1. Force directly related to 4 time square of diameter and inversely to three time

square of length2. The composition of austenitic stainless steel wire used for the construction of

removable appliances is:-• Iron 73%• Chromium 18%• Nickel 8%• Carbon and magnesium

This form of stainless steel wire is known as 18/8 stainless steel. It is available in three forms depending on the manufacturing process of cold working or annealing. Heating the wire softens the wire by redistributing the crystal at degree of 450-500 degree but if the wire is heated above 900 it will become permanently soft, a process known as annealing. Stainless steel wire can be obtained in three main forms:-

• Spring hard

• Medium hard

• Soft

For the construction of components of a removable appliance spring hard stainless steel is usually used, but it is possible to use medium hard in some instances.

Elgiloy wireThe composition of elgiloy wire is:-

1. Iron 14%

2. Chromium 20%

3. Cobalt 40%

4. Nickel 16%

5. Molybdenum 7%

6. Manganese 1.5%

Elgiloy wire is available in four grades:-

1. Red : Resilient

2. Green : Semi Resilient

3. Yellow : Ductile

4. Blue : Soft

Elgiloy is used in its blue soft form in general for constructing Southend clasps or other clasp components for removable appliances. Heat treating the wire increases its strength significantly.

NB:

• Bauschinger effect: it is recommended that when the wire is activated from its passive position, the direction should be in the same direction of bending. This is because bending will increase steel hardening which might fracture if un-winded. This why using reverse loop is preferable.

• NB: Flexibility of wire is important to deliver the desired force for tipping movement which is 30-40gm at the same time rigidity of the wire in direction other than desired direction is unwanted. So to increase flexibility, it is recommended to increase the length by incorporating coils or reduce the

diameter. However, this might affect the rigidity, so it is preferable to use guided wire or reinforced wire with tubing sheath.

Acrylic1. A powder or polymer known as poly methyl methacrylate+a peroxide initiator+ pigment

2. A liquid monomer methyl methacrylate+a stabilizer hydroquinone to prevent polymerization on storage and a cross linking agent.

The polymerizing process may be:-

1. Heat cured: advantage of not releasing polymerized monomer which has been reported to cause reactions for technicians, dentists and patients

2. Self-cured, cold cured, auto polymerizing or chemically activated acrylic is similar to the heat cure material except the liquid contains an activator, such as dimethylptoluidine. Disadvantage: Its poor strength is its main disadvantage.

3. Light cured

4. Dual cured

Side effect of monomerA.For Technicians and dentists

1. Contact dermatitis

2. Paraesthesia of the finger tips in the form of a burning sensation, tingling and slight numbness

3. Asthma, drowsiness, headache, anorexia, and decrease in gastric motor activity

B. For the Patients

1. Unpleasant taste

2. Oedematous reaction accompanied by a burning sensation

Component of RA

Active ComponentMeans by which force is applied to bring about the required tooth movement.

A.Springs1. Palatal finger cantilever - boxed and guarded (0.5 mm SS), (0.7 mm for molars)

2. Buccal spring: self-supporting (0.7 mm SS), Supported (0.5 mm in 0.7mm diameter tubing) or it could be soldered to Adam clasp & supported by tubing

3. Reverse Buccal spring, The spring should be activated by not more than 1 mm. This is most readily done by cutting off 1 mm of wire from the free end and re-forming it to engage the mesial surface of the tooth. Alternatively, it can be activated by opening the loop by 1 mm

4. Cranked cantilever spring (0.5mm)

5. Double cantilever or "Z" spring (0.5 mm)

6. Crossed cantilever spring (0.5 mm)

7. "T" spring (0.5 mm)

8. Coffin spring (1.25 mm). Before the spring is adjusted, it is useful to drill marking pits in the appliance. Divider readings are taken of the transverse distance between these pits so that the amount of expansion can be controlled.

9. Soldered auxiliary spring

B. Bows 1. Roberts' retractor (0.5 mm supported with 0.7mm ss tube sheeting)

2. High labial bow with apron spring (Base arch 1 mm and the apron spring is 0.35-0.4 mm).

3. Labial bow with U loops 0.7 mm, used for minor incisor retraction because of its high force level.

4. Split labial bow (reduces stiffness) 0.7 mm

5. Labial bow with reverse loops (mesial to (5|5) 0.8 mm

6. Self-straightening bows (0.4 mm wire on a labial bow), Individual tooth movements cannot be undertaken and there is a tendency for this device to flatten the arch anteriorly, although the use of two wires will minimize this tendency. This is done by closing the 'U' loops of the bow and adjusting its level as necessary.

7. Extended labial bows

C.Screws1. Arch expansion

2. Arch Contraction

3. Space Opening

4. Space Closing

5. Teeth movement buccally or labially

D.Elastics1. Overjet Reduction

2. Traction to impacted teeth

Retentive Component Means by which the appliance resists displacement.

1. Adams Clasps (0.7 mm molars, 0.6 mm premolars and deciduous teeth). It can be used on posterior or anterior teeth.

2. Jackson clasp

3.Southend Clasp (0.7 mm SS, or 0.7 mm elgiloy). This clasp is activated by bending the U-loop towards the baseplate, which carries the clasp back into the labial undercut of the tooth.

4. C Clasp or it called recurved clasp (0.7 mm)

5. Ball Ended Clasp (0.7 mm or 0.8 mm)

6. Fitted Labial Bow (0.7 mm)

7. Acrylated Labial Bow.

8. Plint clasp around molar bands. These clasps are constructed in 0.7-mm stainless steel and engage the undercuts on a maxillary molar bands

Advantages of the Adams' clasp1. Its bridge provides a site to which the patient can apply pressure with the fingertips during removal of the appliance

2. Auxiliary springs, EOT tubes and hooks can be soldered to the bridge of the clasp

The baseplate Constitutes the body of the removable appliance. It has three functions:

1. It acts as connector2. It contributes to anchorage through its contact with the palatal vault and teeth that

are not being moved; 3. It may be built up into bite planes to disengage the occlusion or produce overbite

reduction (ant or post bite plane)4. It provide housing and protection of the URA components.

Anchorage1. Intramaxillary compound anchorage: The greater number of teeth incorporated in

the appliance increases the anchorage component. Teeth with larger root surface areas incorporated within the appliance may increase the anchorage component.

2. Reciprocal anchorage: Reciprocal anchorage where equal and opposite movements of two teeth are required by tipping either by the activation of two finger springs in opposite directions or by means of a screw plate achieving equal and opposite forces.

3. Intermaxillary anchorage:. This does however increase the demand on the retentive part of the appliance and an operator needs to be confident in the retentive component of his or her appliance.

4. Base Plate: A large well fitting base plate provides excellent vertical and lateral anchorage. Where a high vaulted palate is present this will add additionally to the AP anchorage component.

5. Extraoral Anchorage

• HG

• Face Masks

Modified types of removable appliancesBuccal acrylic lower appliances

• To overcome the problem of limited undercut on the buccal aspect of lower molars, appliances have been described with clasping on the lingual aspect of the molars (Bell, 1983).

• Two acrylic baseplates are used, one on each side resting on the buccal mucosa.

• The acrylic is connected across the anterior labial mucosa by a stainless steel bar.

• A modified Jackson clasp is used on the lingual aspect engaging the lingual undercuts of the molars.

• The main use of such an appliance is to retract mesially inclined lower canines.

How components are combined to design an applianceThe stages of appliance design are as follows:

1. A decision must be made on the active components desired to achieve the type and direction of tooth movements required.

2. The retentive components should then be planned to enable the appliance to remain in its desired position within the mouth and not to be displaced when the active components are activated appropriately.

3. The base plate holding active and retentive components together must be designed to hold all these components together. Thought must be given to patient comfort. Additional features that need to be considered at this stage include the addition of any of the following components:-

• Anterior bite plane, this may be flat or inclined

• Posterior bite plane

4. Anchorage requirements - relate the desired tooth movements against the undesirable reactive tooth movements that are likely to occur. An estimate of additional anchorage requirements would be required at this stage as to whether the base plate alone with the retentive clasps are sufficient for the type

of tooth movement that is desired or whether additional anchorage requirements would be required such as:

• The addition of headgear (distal movement, protraction)

• Inter maxillary elastics

The First Fitting of an Appliance1. Check the appliance is the correct appliance for the patient.

2. Check the appliance has been made to the correct appliance design and finished appropriately by picking the appliance up and run your finger over it.

4. Show the appliance to the patient and explain the different components of the appliance

5. Try the appliance in the mouth.

6. Adjust the clasps appropriately to generate sufficient retention

7. Instruct the patient on how to handle the appliance, how to take it out of the mouth, how to put the appliance back in.

8. Activate the appliance and where necessary trim acrylic to enable the appropriate tooth movements to occur.

9. Final try in.

10. Instruction

• Time appliance is to be worn for 23 hours and 50 minutes of every day; five minutes in the morning and evening are for cleaning the appliance and the teeth.

• Appliance hygiene.

• Activating screws or adding elastics as necessary.

• How to handle emergencies.

• Remove in during swimming or contact sport activity.

Inspection of RA on recall visits1. Ask the patient about his or her experience with the firstly fitted RA

2. Ask the patient to remove the RA and watch the experience of the patient in removing the RA which reflect the degree of wearing the appliance

3. Insert the RA and simply check the

• Oral condition in general for oral hygiene,

• Any trauma spots

• Marks of appliance wear.

4. Check that the springs are correctly positioned and noting any degree of activation remaining in the springs,

5. Check the fitting surface of the appliance and the fitting surface within the mouth,

6. Check for relevant tooth movements

7. Check overjet, OB, CR, ML and MR.

8. Activate

9. Reinstruct

Trouble shooting with RA

A.Teeth doesn’t not move1. Check whether the appliance has been worn or not.

2. Check that the teeth are free to move in the correct direction making sure that there are no interferences either by the acrylic base plate or occlusion.

3. Check the activation of the active components of the appliance.

B. Breakage1. Pt eating hard stuff

2. Habit of clicking the appliance

3. Poor design

C. Sign of wearing RA1. Good speech

2. Expert in removal and insertion

3. Evidences of movement

4. Loose appliance

5. RA impression on ST

6. Non-shiny appliance