Removable appliances are orthodontic appliances that can apply pressure to teeth and are removable by the patient. They have a resin base plate with attachments like springs or screws that exert forces. Removable appliances are useful for simple tooth movements and as retainers. They have advantages like easy adjustment but disadvantages like inability to correct complex malocclusions. Key components are active components to move teeth, retention to hold the appliance, anchorage to resist forces, and the base plate.

1. REMOVABLE
APPLIANCE:PRINCIPLE AND
COMPONENT
Dr.Norma Ab Rahman

2. DEFINITION
 ORTHODONTIC APPLIANCE
 Orthodontic appliances are appliances by means of
which pressure can be applied to a tooth or group of
teeth in a predetermined direction.

3. DEFINITION
 REMOVABLE APPLIANCE
 A removable appliance is a base plate usually acrylic
resin to which attached various claps, spring etc and the
appliance can be inserted and removed by the patient.
(BSI,1969)

4. INDICATIONS
 Indications for the use of removable appliances:
 When tipping movement is required
 For rotational movement of teeth which are broad
mesio-distally
 For overbite reduction with the use of anterior bite
plane
 For space maintenance
 For retention at the end of active treatment

5. ADVANTAGES
 The advantages of removable appliances:
 Can be removed for tooth brushing, socially sensitive
occasion or if any damage or problem
 Palatal coverage increases anchorage
 Easy to adjust
 Arcylic can be thickened to form either anterior or
posterior bite plane (bite plane can be incorporated)

6.  Useful as a passive retainer or space maintainer
 Can be used to transmit forces to blocks of teeth
 Control is less complex because only simple tooth
movements are affected
 Less expensive

7. DISADVANTAGES
 Disadvantages of removable appliances:
 Appliance can be removed by non-complying patients
 Only simple malocclusion can be corrected (Only
tipping movement possible)
 Inefficient for multiple individual tooth movements
 Lower removable appliance are difficult to tolerate
 Affects speech

8. DESIGNING REMOVABLE APPLIANCES
 Four components need to be considered for every
removable appliances:
 Active component
 Retaining the appliance
 Anchorage
 Baseplate
(ARAB)

9. ACTIVE COMPONENTS
 The component which exert the force which moves the
teeth
 Includes:
 Springs (commonly used)
◼ Z-spring and double cantilever
◼ Finger spring
◼ T-spring
◼ Buccal canine retractor
◼ Coffin spring
 Screws
 Labial bow (can be active or passive component)

10. Z-spring & double cantilever
 These springs are used for rotational movement
and/or labial movement of teeth.
 Constructed from 0.5mm stainless steel wire (SS)
 2 coils (2-3mm in diameter)
 Seated 90° to palatal surface of the incisor
 Activation : open the coil by 2-3mm

13. Finger spring
 To move tooth along dental arch, distal or mesial.
 Constructed from 0.5mm stainless steel wire (SS)
 Coil- 3mm diameter, midway between gingival
margin and the midline of palate.
 Activation: hold the coil with plier and push with
finger the free-end half a tooth width.

16.  Guard wire
 Function is to support springs
 0.5mmSS
 Longer on the side where the tooth is moved

17. T-spring
 For buccal movement of a single premolar or molar
tooth
 Constructed from 0.6mm stainless steel wire (SS)
 Spring position at the palatal side of the teeth to
be moved.
 Activation: the vertical arm of the T-spring should be
bend to displace the horizontal arm towards the
tooth.

19. Buccal canine retractor
 To retract or distalized the canine when canine is
placed labially or high in sulcus
 When requires the movement of canine both distally
and palatally.
 Can be given only in the upper arch.
 Made up of 0.7mm SS or 0.5mm SS (requires tube
sleeve to prevent distortion.)

20.  Activation:
 To bring about distal movement, the free end is cut
short by 1mm and is readapted to engage the mesial
side of the canine
 To bring about palatal movement, the active arm is
bent at a point where it emerges out from the coil.

22. Coffin spring
 To expand upper arch transversely
 Constructed from 1.25mm SS
 Activation: the central curved portion is flattened
using finger pressure or plier so that the two halves
of the appliance move apart

24. Expansion screws
 To move more than one tooth
 To expand arch transversely/ anterior-posteriorly
 Activation: patient turning the screw by the screw’s
key

27. Labial bow
 Functions are to retract upper labial segment and
also for retention
 To reduce OJ<4mm
 Constructed from 0.7mm stainless steel wire (SS)
 Split labial bow used to increase flexibility for
reducing OJ
 Activation: closing U-loop

29. Retentive Component
 Means by which the appliance is retained in the
mouth
 Orthodontic removable appliance should have 3
points retention to be sufficiently retentive
 Retentive component include:
 Adam’s clasp
 Southend clasp
 Ball-hook clasp

30. Adam’s clasp
 Constructed from 0.7mm stainless steel wire (SS) for
molars and incisors and 0.6mm SS for premolars
and canines
 Adjustment with Adam’s plier

31. Southend Clasp
 Constructed from 0.7mm stainless steel wire (SS)
 For anterior teeth
 Adjustment with Adam’s plier

32. Ball end clasp
 It is use for retention purpose
 Normally used for anterior teeth
 Preformed ball end claps are available
 Adjustment with Adam’s plier

33. Anchorage
 The manner in which the applied force is resisted.
 When the active components of RA are activated,
the reaction for the appliance to move in the
opposite direction
 The ability to resist this adverse movement is call
anchorage.

34.  Provided mainly by:
 the base plate moving against the palatal vault or the
anterior portion of the mandible.
 the teeth, the more teeth the base plate embraces the
greater the anchorage
 the retention of the clasp

35. Base plate
 Means whereby the various components of a
removable appliance are attached to.
 Normally made up of arcylic resin, should be thin
and smooth but thicker in the lower to increase
strength.
 Can be modified to include:
 Anterior bite plane (ABP)
 Posterior bite plane (PBP)

36. Anterior bite plane
 Raised platform in the anterior part of the URA
 Function:
 To reduce OB
 To relieve posterior occlusion when correcting buccal
CB/ Scissors bite

40. Posterior bite plane
 Raised base plate over the occlusal surfaces of
posterior teeth
 To allow correction of anterior crossbite