Removable Appliances Orthodontics Question And Answers

Removable Appliances

Question 1. Briefly describe advantages and disadvantages of removable appliances.
Or
Write short note on disadvantages of removable appliances.
Answer.

Removable Orthodontic Appliances

Orthodontic appliances are the devices that can be inserted into and removed from oral cavity by the patient at will.

Advantages of Removable Appliances

• Removable nature of appliance makes it possible to maintain good oral hygiene during orthodontic therapy.
• Appliance can be kept clean by patient.
• Fabricated in lab so less chair side time is required.
• It bring about tipping tooth movement so it require less force and employs less strain on the anchor teeth.
• Removable appliance can be used by general dental practitioners so specialist can concentrate on more difficult cases, the orthodontist can handle more number of patients.

Read And Learn More: Orthodontics Question And Answers

• Fabrication of removable appliances need less inventory.
• They are relatively less expensive than fied appliances.
• They are less conspicuous as compared to multibanded fixed appliance.
• Damaged appliances that applied undesirable forces can be removed by the patient.

Disadvantages of Removable Appliances

• Patient cooperation is very important for the success of the treatment.
• Capable of only tipping tooth movement. So cases which are already tipped are not treated by removable appliances.
• When multiple tooth movement required each movement should carried out at one time. So treatment time is prolonged.
• Multiple rotation are diffilt to treat.
• Difficult to close extraction space by removable appliance by forward movement of posterior teeth.
• Patient may misplace or damage the appliance.
• Patient should learn to remove and replace the appliance without distorting them.
• It can’t be used for treating severe class 3 and 3 malocclusion
• Ectopic teeth are very diffilt to correct by removable appliances.
• Tight proximal contact is diffilt to obtain between the teeth and removable appliance.
• Patients having complex problems cannot be treated.

Question 2. Define an appliance. Name the components of removable appliance. What are the principles of a spring fabrication?
Answer.

Appliance

Devices by means of which mild pressure may be applied to a tooth or group of teeth and their supporting structures so as to bring about necessary changes within the bone which will allow tooth movement.

Removable Appliances

Appliances which can be removed and reinserted into the oral cavity by the patient.

Components of Removable Appliances

Following are the components of removable appliances:

• Active components
  • Springs
  • Labial bows
  • Screws
  • Elastics.
• Retentive components
  • Clasps
  • Bows.
• Anchorage
  • Clasps
  • Base plate contacted with non-moving part
  • Headgears
  • Intermaxillary elastic.
• Base plate: Form the framework.

Spring

Springs are the active components of removable orthodontic appliances that are used to effect various tooth movements.

Principles of Spring Fabrication

• Diameter of wire: Spring should be flexible. The flexibility of the spring to a large extent depends upon the diameter of wire used.
  • The force generated is:
    • F = D4/L3
    • F = Force
    • D = Diameter of wire
    • L = Length of wire
  • Thicker wires when used, decrease the flexibility of the spring and apply a greater force on the tooth.
  • Thus by decreasing the diameter the force applied is lesser and therefore the spring remains more flexible and active over a longer period of time.
• Length of wire: Force can be decreased by increasing the length of the wire.
  • Thus the springs that are longer are more flxible and remain active for a long duration of time.
  • Helices and loops can be incorporated in the springs to make them more active.
  • By doubling the length the force can be reduced by 8 times.
• Force to be applied: Force that should be generated by the springs is calculated based on the number of teeth to be moved, root surface area and patient comfort.
  • On an average force of about 20 gm/cm2 of root area is recommended.
• Patient comfort: The spring should not offer any patient discomfort by its design, size, position or the force it generates.
• Direction of tooth movement:
  • The direction of tooth movement is an important consideration in designing a spring.
  • The direction and tooth movement is determined by the point of contact between the spring and the tooth.

Question 3. Write short note on Adam’s clasp.
Or
Briefly describe Adam’s clasp.
Or
Write short note on Adam’s clasp and modification.
Answer. It was fist described by Professor Phillip Adams.

• It is also known as Liverpool clasp, universal clasp and modified arrowhead clasp.
• The clasp is constructed using 0.7 mm or 21 gauge hard round stainless steel wire. In canines 0.6 mm wire is used.

Design of Adam’s Clasp

It consists of three parts, i.e. arrowhead, bridge and retentive part.

• Arrowhead
  • Tip of arrowhead is placed both mesially and distally to the tooth below greatest area of circumference.
  • It slopes with contour of gingival margin in interdental area.
  • Both the arrowheads should be parallel to each other.
• Bridge
  • It connects both the arrowheads.
  • Bridge should always be straight.
  • Angle between bridge and tooth surface is 45°
  • Gap of 1 to 2 mm should be present between bridge and tooth surface.
  • Fitting of bridge is done against the buccal surface.
  • Placement of bridge is done halfway between cervical as well as occlusal margins of buccal surface.
• Retentive part
  • Fits close to contact point.
  • Adaptation should be done interdentally.

Adam’s clasp Advantages

• It is rigid and offer excellent retention.
• Can be fabricated on deciduous and permanent teeth.
• Can be fabricated on fully or partially erupted teeth.
• Can be used on any teeth.
• Can be modified in many ways.
• Does not cause tooth separation.
• Hooks can be formed over the clasp.
• Soldering of tubes can be done.
• No requirement of any special plier to fabricate Adam’s clasp.

Adam’s clasp Disadvantages

• Adam’s clasp can go fracture under fatigue.
• In pedodontic cases if used for very long time, it interfere with the lateral growth of mandibular arch.

Question 4. Write short note on labial bows.
Or
Write short note on types of labial bows with uses.
Answer.

Bows

Bows are the active component of orthodontic appliance which exert forces mostly on incisors to bring about the necessary tooth movement.

Type of Used Labial Bows

Labial bows with U loop

• Short labial bow
• Long labial bow
• Split labial bow
• Reverse labial bow
• Fitted labial bow

Labial bows without U loop

• Robert’s retractor
• Mills retractor
• High labial bow with apron spring.

Short Labial Bow

• This bow is constructed using 0.7 mm hard round stainless steel wire
• The labial bow consists of a bow that makes contact with the most prominent labial teeth and two U loops that end as retentive arm distal to the canines.
• They are indicated in case of minor overjet reduction and anterior space closure.
• This can also be used for retention at the termination of fixed orthodontic therapy.

Long Labial Bow

• It extends from fist premolar to the opposite fist premolar.
• Used in actively growing patient.
• Used in—minor anterior space closure, minor overjet reduction, closure of space distal to canine as retentive device.

Split Labial Bow

• The bow is split in the middle to increase flexibility.
• Used for anterior retraction midline diastema closure.

Reverse Labial Bow

• Also called reverse loop labial bow.
• U loops are placed distal to canine.
• Because of increase length of wire the flexibility is more.

Robert’s Retractor

• Made by thin 0.5 mm diameter wire along with increased wire length due to the incorporation of coil.
• This labial bow having a coil of 3 mm internal diameter mesial to the canine.
• This labial bow is highly flexible.
• Indicated in patients having severe anterior proclination with overjet of over 4mm.

Mill’s Retractor

• This labial bow having extensive looping of the wire so as to increase the flexibility.
• Indicated in patients with a large overjet.
• Difficult in fabrication.
• Poor patient acceptance.

High Labial Bow with Apron Springs

• It consists of a heavy wire bow of 0.9 mm thickness that extends into the buccal vestibule.
• Apron spring made of 0.4 mm wire attached to the high labial bow.
• This type of labial bow is highly flexible.
• Used in case of large overjet.

Fitted Labial Bow

• In this type the wire is adapted to confirm the contours of labial surface.
• The U loop is usually small.
• They are used as retainers at the completion of fixed orthodontic therapy.

Question 5. Write short note on canine retractor.
Answer. Canine retractors are the springs that are used to move canines in the direction.

Canine Retractors Classification

• Based on their location.
  • Buccal-buccally placed.
  • Palatal-palatally placed.
• Based on the presence of helix or loop.
  • Canine retractor with helix.
  • Canine retractor with loop.
• Based on their mode of action.
  • Push type.
  • Pull type.

Types of Canine Retractors

U Loop Canine Retractor

• Spring design: It is made of 0.6 mm or 0.7 mm stainless steel wire. It Consists of a U loop, an active arm and a retentive arm which lies distally. Base of U loop is 2–3 mm below cervical margin. Mesial arm of U loop is bent at right angle and adapted around the canine below its mesial contact point.
• Activation: This is activated by closing the loops by 1–2mm or cuttng the free end of the active arm by 2 mm and readapting it.
• Indication: Mechanically this is least effective and is indicated as minimum distal retraction of 1 to 2 mm of canine is required.
• Advantage: It is easy to fabricate, simple in design and is less bulky.
• Disadvantage: This is least efficient of all the canine retractors.

Helical Canine Retractor

• Spring design: It is also known as reverse loop canine retractor and is made up of 0.6 mm wire. It consists of a helical loop or coil of 3 mm diameter, an active arm and a retentive arm. Mesial arm is adapted between the premolars. Distal arm is active and is bent at right angle to engage the canine below height of contour. Coil is placed 3–4 mm below the gingival margin. Height of the coil is adjusted based on the vestibular height.
• Activation: By opening the helix by 1 mm or by cuttng 1mm of the free end and readpting it around canine.
• Indications: It is given in patients with shallow sulcus mainly with mandibular arch.
• Drawbacks: This is stiff in the horizontal plane and is unstable vertically.

Palatal Canine Retractor

• Spring design: It is made up of 0.6 mm stainless steel wire. This consists of a coil of 3 mm diameter, an active arm and a guide arm. Active arm is placed mesial to canine. Helix is placed along the long axis of canine. And as far as possible to have retractor a good range of action. Retentive tag is embedded in acrylic plate.
• Activation: It is done by
  • Opening the helix 2 mm at a time.
  • By pulling the free arm of spring slightly away from point of emergence from the coil.
  • Tension is given to the spring by squeezing the coil with the tip of pliers.
• Indication: It is used in retraction or distalization of palatally placed canines.

Buccal Canine Retractor

• Fabrication: It consists of a coil of 3 mm diameter, an active arm and a retentive arm. Coil is placed distal to long axis of canine. End of the spring is bent at right angle to canine to be moved and then it is shaped to tooth. The tag should cross over mesial side of second premolar.
• Modifications: They can be of two types, i.e. supported and self-supported.
  • Supported or sleeved: These canine retractors are made by 0.5 mm stainless steel wire. They are more flxible and mechanically effient. As they lack stability, they are enclosed in stainless steel tubing.
  • Self supported: These canine retractors are made by 0.7 mm stainless steel wire so that spring can support itself.
• Activation: Self-supported canine retractors are activated by closing the helix 1 mm at a time while the supported canine retractors can be activated up to 2 mm at a time. Activation is carried out by using ‘hollow chop’ pliers such as Mathews or Andresen’s.
• Indications: In patients where there are buccally placed canines and canines are placed high in the vestibule. They help in movement of canine both buccally and palatally.

Question 6. Discuss in brief the modifications of Adam’s clasp.
Or
Write short note on modifications of Adam’s clasp.
Answer. Adam’s clasp can be modifid in number of ways. These modifications permit additional uses or enhanced retention.

Modifications of Adam’s clasp

• Adam’s with single arrowhead: The Adams clasp can be modified to have a single arrowhead. This type of clasp is indicated in a partially erupted teeth which usually is the last erupted molar. The single arrowhead is made to engage the mesio-proximal undercut at the last erupted molar. The bridge is modified to encircle the teeth distally and ends on the palatal aspect as a retentive arm.

• Adam’s clasp with J hook: A J hook can be soldered on the bridge of the Adam’s clasp. These hooks are useful in engaging elastics.

• Adam’s with incorporated helix: A helix can be incorporated into the bridge of the Adam’s clasp. This also helps in engaging elastics.

• Adam’s with additional arrowhead: Adam’s clasp can be constructed with an additional arrowhead. The additional arrowhead engages the proximal undercut of the adjacent teeth and is soldered on the bridge of the Adam’s clasp. This type of clasp offers additional retention.

• Adam’s clasp with soldered buccal tube: A buccal tube can be soldered on the bridge of the Adams clasp. This modification permits use of extraoral anchorage using face bowhead gear assembly.

• Adam’s clasp with distal extension: The Adam’s clasp can be modified so that the distal arrowhead has a small extension incorporated distally. This distal extension helps in engaging elastics.

• Adam’s clasp on incisors and premolars: Adam’s clasp can be fabricated on the incisors and premolars when retention in those areas are required. They can be constructed to span a single tooth or two teeth.

Question 7. Write short note on cantilever springs.
Answer. Spring is the active component of removable orthodontic appliance.

Question 8. Compare anterior bite plate to posterior bite plate.
Or
Differentiate anterior bite plates vs posterior bite plates.
Answer.

Question 9. Write short note on Hawley’s appliance.
Answer. Charles Hawley in 1920 designed Hawley’s appliance which is the most frequently used retainer.

• Hawley’s appliance is also known as dental crutch.
• This is a passive appliance which can be removed and inserted by the patient at his/her own will.
• A classic Hawley’s retainer consists of clasp on the molars and a short labial bow from canine to canine having adjustment loops.

Modifications of Hawley’s Appliance to Suit Specific Requirements are:

• Labial bow in Hawley’s appliance can be extended from fist premolar of one side to fist premolar of another side. This design closes the space distal to canine.
• Soldering of bow to bridge of Adam’s clasp: This design avoids the risk of space opening up between canine and premolar because of cross over wires. Fitted labial bow can also be used to offer the excellent retention.
• Anterior bite planes can be incorporated to retain or correct the deep bite cases.

Advantages of Hawley’s Appliance

• It is easy to fabricate as it has simple design.
• There is minimum patient discomfort because of decreased bulk.
• Since it is relatively inconspicuous it is acceptable to patient.

Indications

• It is used to close the space in anterior region.
• It is used in retracting the minor proclination.
• It is used as a retainer appliance.
• Hawley’s appliance with bite plane is used to correct the deep bite.
• It is used to treat TMJ problems.
• It is used as a habit breaking appliance
• Hawley’s appliance along with bite plate removes the restraining effct in mandible and allows the further growth.