removable orthodontic appliance

1. Removable orthodontic
appliance

2. Definition
Removable orthodontics appliances refers to those devices that
can be inserted into and removed from the oral cavity by the
patient will .

3. History
• First fixed appliance prototype, 1728. Historically, the
development of the fixed appliances preceded that of
removable appliances. Pierre Fauchard, father of modem
dentistry, in his 2-volume opus entitled, ‘The Surgeon Dentist’
published in 1728 described the bandeau, an expansion arch
consisting of a horseshoe-shaped strip of precious metal to
which the teeth were ligated. This fixed appliance tied to the
teeth became the basis for Angle’s E-arch.

4. • Removable appliance, 1836. A German dentist “Friedrich
Christoph Kneisel (1797-1847) was first to use plaster
models to record malocclusion in 1836 and use chin strap
for his prognathic patients which perhaps was the first
removable orthodontic appliance. He also used a
removable plate quite similar to the one used nowadays .
Further evolution of the removable appliances was linked
to the development of the process of rubber
vulcanization.

5. Advantages of removable orthodontic
appliance
• Removable nature of appliance make it possible for the patient to
maintain good oral hygiene during treatment
• take less chair side time for orthodontics , as they are fibricated in
labrotary
• Damaged appliances can be removed by patients .
• Apparently simple to fabricate, use and adjust. Hence require
minimal chair time
• Less orthodontic scars compared to fixed appliances such as
decalcification, caries under molar bands and white spots around
bonded brackets and gingivitis.

6. • Cost-effective
• Efficient to use for certain type of tooth movements
• Removable appliances are the appliances of choice in
the first stage of the correction of a posterior crossbite
• They are used commonly during mixed dentition for
treatment of a variety of interceptive procedures. If one
considers the factors of risk and the relationship between
work volume and effect, removable appliances deserve
preference.

7. Disadvantages
• Not effective with uncooperative patient
• Only treat the minor cases of malocclusion
• Only capable of tipping tooth movement
• Limited control over tooth movement
• Only certain types of malocclusion can be corrected.
• Tooth movement in three dimensions is not possible.
• May hinder with speech and eating
• Appliances may be lost or broken
• Residual monomer of acrylic resin may cause allergy and/or
irritation.

8. Components of removable
appliances

9. Retentive component
They are the component that help in keeping the appliance in
place and resist displacement . Adequate retention of a
removable appliance is achieved by incorporating certain wire
component that engage undercuts on the teeth . These wire
components that aid in retention of a removable appliance are
called clasp .
Mode of action of clasp
clasps act by engaging certain constricted areas of the teeth
that are called undercuts. When clasps are fibricated the wire is
made to engage these undercuts so that there displacement is
prevented .

10. Requirement of ideal clasp
1. It should offer adequate retention .
2. It should permit usage in both fully erupted as well as partially
erupted teeth .
3. They should not themselves apply any active force that would bring
about undesired tooth movement of the anchorage teeth .
4. It should be easy to fabricate .
5. It should not impinge on the soft tissues .
6. It should not interfere with normal occlusion .

11. Guidelines of appliance activation
1) The path of tooth movement should be free of any obstructions
2) The retraction/tipping of maxillary incisors should not be initiated till
sufficient bite opening has been achieved . Early retraction of
maxillary anterior tooth will further cause extrusion and relapse
3) Activated labial bow appliance without sufficient relief of acrylic
base plate for incisor retraction is a common mistake . The palatal
acrylic is so trimmed that it would allow greater movement of
incisors at the cingulum , thereby minimising tipping at incisal edge
4) The conventional labial bow should uniformly touches labial surface
of all the teeth being retracted . To retract the single malpositioned
incisor , labial bow activation should be minimal and gentle . heavy
force can produce pain , pulpitis and non-vital tooth .

12. 5) For distal canine retraction , enough acrylic should be removed in the
alvelous are to accommodate large buccolingual dimension of the
distally moving maxillary canine .
6)To minimize tipping and rotation during canine retraction , the
point of contact of activated spring arm should be as gingival as possible
without damaging the gingiva .
7) The free end of retraction spring should gently touch the mesial
surface of the canine at its neck on its entire labiolingual thickness . It is
slightly extended to passively turn around on labial surface for palatal
canine retractor and palatal surface for labial canine retraction
8) The premolar should be prevented from mesial tipping and
anchorage loss with the ‘c’ clasp on its mesial proximal surface . It may
require to be gently activated in a distal direction if the anchorage loss is
anticipated.

13. Circumferential clasp
It is also known as three-quarter clasp or `C’ clasp . They are simple
clasp that are designed to engage the bucco-cervical undercut
This clasp cannot be used in partially erupted teeth where the
cervical undercut is not avilable for clasp fabrication .

14. • Adaptation
A wire is engaged from one proximal undercut along the cervical
margin then carried over the occlusal embrasure to end as a single
retentive arm on the lingual aspect that gets embedded in the acrylic
base plate .
Advantages :-
Simple design and fabrication
Disadvantage :-
It cannot be used in partially erupted teeth wherein cervical undercut is
not avilable fo clasp fabrication

15. Jackson’s clasp
• It is also called full clasp or ‘U’ clasp . The clasp engage the bucco-
cervical undercut and also the mesial as well as distal proximal
undrecuts.

16. • Adaptation
Wire is adapted along the buccocervical margin and both the
proximal undercuts ,and carried over both the occlusal embrasures to
end as retentive arms on both side of the molar
• Advantages : simple to construct and offers adequate retention .
• Disadvantage : it offers inadequate retention in partially erupted
tooth.

17. Adams clasp
• Adams clasp was first descried by professor phillip Adams .
it is also known as liverpool clasp ,universal clasp and modified
arrowhead clasp .
The clasp is constructed using 0.7mm hard round stainles steel wire .
Adams clasp is made up of three parts
(a) two arrowheads
(b)bridge
(c)two retentive arms
Two arrow heads engage the mesial and the distal proximal
undercuts . The arrow heads are connected to each other by a bridge
that is at 45 degree to the long axis of the root

18. •
• :-:
• fig :- adams clasp

19. Advantages of adams clasp
• It is rigid and offers excellent retention
• It can be fibricated on decidious as well as permanent teeth.
• They can be used in partially or fully erupted teeth.
• It can e used on molars ,premolars and on incisors .
• No special instrument is needed .
• It is small and occupies minimum space .
• The clasp can be modified in a number of ways .

20. Steps in fabrication of adams clasp

23. Modifications in adams clasp
a) Adams with single arrowhead : This type are indicated in partially
erupted tooth ,which usually is last erupted molar . The single arrow
head is made to engage the mesio-proximal undercut of the last
erupted molar . The bridge is modified to encircle the tooth distally
and ends on the palatal aspect as a retentive arms .
b)Adams with J hook : J hook can be soldered on the bridge of the
adams clasp . These hooks are useful in engaging elastics .

24. c) Adams with incorporated helix : A helix can be
incorporated into a bridge of the adams clasp . It also help in
engaging elastics .
d) Adams with additional arrow head : Adams with additional
arrow head can e constructed to engage the proximal
undercuts of the adjacent tooth and is soldered on the
bridge of the adams

25. e) Adams with soldered buccal tube :For extra oral anchorage
using face bow and headgears , a buccal tube can be soldered on the
bridge of adams clasp.
f)Adams with distal extension : The adams can be modified so that he
distal arrow head has a small extension incorporated distally .They can
be used in engaging elastic .
f) Adams on incisor and premolars : Adams clasp can be fabricated on
the incisor and premolar areas when the retention in these area is
required .

26. Southend clasp
Southend clasp is used when retention in the anterior region
is required .The wire is adapted along the cervical margin of both the
central incisors . The distal ends are carried over the occlusal
embrasures to end as retentive arms on the palatal side .
Traingular clasp
They are small traingular shaped clasp that are used
between two adjacent posterior teeth . Thus they engage the
proximal undercuts of two adjacent teeth . These clasp are indicated
when additional retention is required .

27. Schwarz clasp
Schwarz clasp or arowhead clasp can be said to be the predecessor
of the adam clasp . The clasp is designed in such a way that a number
of arrowhead engage the interproximal undercuts between the
molar and between the premolars and molars . This clasp is not used
routenly due to numbers of drawbacks .
Crozat clasp
This clasp resemble a full clasp but has but has an additional piece
of wire soldered which engages into the mesial and distal proximal
undercuts .thus it offers better retention than the full clasp .

28. Active component of removable
orthodontic appliances
• They are components of the appliances that exert forces to
bring about the necessary tooth movements .
The active component includes :
(a) bows
(b)springs
(c)screws
(d)elastics

29. • Bows
Bows are active components that are mostly used for incisor
retraction .
Types of the bows :
(a) Short labial bows :
They are constructed using 0.7mm hard round stainless steel
wire . It consist of bow that make contact with the most prominent
labial teeth and two U loops that ends as retentive arms distal to the
canine . The short labial bow is activated by compressing the U loop .
Indication : Minor overjet reduction and anterior space closure .

30. (b) Long labial bows
This labial bow is similar to the short labial bow except that it extends
from one first premolar to opposite first premolar . The distal arms of
the U loops are adapted over the occlusal embrasure between the
two premolars to get embedded in the acrylic plate .
Indications :
• minor anterior space closure
• minor overjet reduction
• closure of space distal to canine
• guidance of canine during canine retraction using palatal retractor
• as a retaining device at the end of fixed orthodontic treatment

31. (c) Split labial bow
This is a labial bow that is split in the middle . This result in two
seprate buccal arms having a U loop each . This type of labial bow
show the increase flexiblity as compared to the conventional short
labial bows .
This type of labial bow is used for anterior retraction .
The split bow is activated by compressing the U loop 1-2mm at a
time .

32. (d) Reverse labial bow
This is also called reverse loop labial bows . Here the U loop is
placed distal to the canine and the free end of the U loop are adapted
occlusally between the first premolar and canine .indication are
similar to that of short labial bow . Activation is done in two step .
First the U-loop is opened resulting in lowering of the labial bow in
incisor region . The compensatory bend is then made at the base of U
loop to maintain proper level of the bow .

33. (e) High labial bow with apron springs
It consist of heavy wire bow of 0.9 mm thickness that extends
into the buccal vestibule . Apron spring made of 0.4mm wire is attached
to high labial bow . The apron spring can be designed for retraction of
one or more teeth . This type of labial bow is highly flexible and is thus
used in cases of large overjet . The apron spring is the active component
that is activated by bending it towards the teeth , activation of upto
3mm can be done .

34. (e) Robert’s retractor
This is a labial bow made of thin guage stainless steel wire having a
coil of 3mm internal diameter mesial to the canine . As very thin wire
is used for its fabrication ,the bow is highly flexible and lacks
adequate stability in the vertical plane . Thus the distal part of the
retractor is supported in a stainless steel tubing of 0.5 mm internal
diameter .
Indications :-
Patient having severe anterior proclination with over jet of over
4mm .

35. (f) Mills retractor
This is a labial bow having extensive looping of the wire so
as to increase the flexibility and range of action . Mills retractor are
indicated in patient with a large overjet .
Disadvantage :-
• difficult in construction
• poor patient acceptance

36. • Springs
Springs are the active component of removable
orthodontic appliance that are used to effect various tooth
movements .
Classification of springs –
(1) Based on the presence or absence of helix they can be classified as
simple –without helix
compound –with helix
(2) Based on the presence of loop or helix they can be classified as
helical springs – have a helix
looped springs – have a loop
(3) Based on the nature of stability of the springs they can be classified as :
self –supported spring = made of thicker gauge wire ,can support themselves
supported springs = made of thinner gauge wire and thus lack adequate
stability , springs are encased in metallic tube to give adequate support .

37. Ideal requisites of a spring :-
a) the spring should be simple to fabricate .
b) it should be easily adjustable .
c) It should fit into the avilable space with out discomfort to the
patient .
d) It should be easy to clean .
e) It should apply force of required magnitude and direction .
f) It should not slip or dislodge when placed over a sloping tooth
surface .
g) It should be roust .
h) It should remain active over a long period of time .

38. • Factor to be considered in designing a spring .
a) Diameter of wire :- flexibility of the spring to a large extent depends upon diameter of wire
F = D4/l3
where
F= force applied by spring
D=diameter of wire
L= length of wire
b) Length of wire :- force can be decreased by increasing the length of wire . Thus springs that
are longer are more flexible and remains active for long duration of time . By doubling the
length of wire force can be reduced by eight times .
c) Patient comfort :- spring should be comfortable to patient in design , shape , size or force
generation . The patient should be able to insert the appliance with spring in proper
position.
d) Direction of tooth movement :- the direction of tooth movement is determined by the point
of contact between the spring and the tooth . Palatally placed spring are used for labial and
mesio – distal tooth movement .buccally placed spring are used when the tooth is to be
moved palatally and in a mesio-distal direction .

39. Finger spring
Finger spring is also called single cantilever spring as one end is fixed
in acrylic and the other end is free . It is constructed using 0.6mm
wire . It consist of active arm of 12-15mm length ,a helix of 3mm
internal diameter and retentive arm of 4-5 mm length . It is used for
mesio distal tooth movement when teeth are located correctly in
bucco lingual direction .it is activated by moving active arm toward
the teeth intended to be moved .

40. • Cranked single cantilever spring
It is constructed with 0.5mm wire . The spring consist of coil , close to
its emergence from base plate . The spring is cranked to keep it clear
of the other teeth .it is used to move teeth labially .

41. Z spring
The ‘z’ spring is also called double cantilever spring . It is made up of
0.5mm wire . The spring consist of two coil of very small internal
diameter .it should be placed perpendicular to palatal surface of
tooth . The spring can be made for movement of single incisor or two
incisor . It is activated by opening helices by about 2-3 mm at a time .

42. • T spring
It is made of 0.5 mm wire . The spring consist of t shaped arm whose
arm are embedded in acrylic. It is used for buccal movement of
premolar and some canine . It is activated by pulling the free end of
the t toward the intended direction of tooth movement.

43. Coffin spring
It is made of 1.2mm wire . It consist of a u or omega shaped wire
placed in the midpalatal region with retentive arm incorporated in
base plates .it is retended by adams clasp in molar .it is used in slow
dentoalveolar arch expansion in patient with upper arch constriction
or in unilateral crossbite.

44. Canine retractors
Canine retractors are springs that are used to move canine in a distal
direction .
classification of canine retractors
a) Based on their location
buccal canine retractor
palatal canine retractor
b) Based on the presence of helix or loop
canine retractor with helix
canine retractor with loop
c) Based on their mode of action
push type
pull type

45. • U loop canine retractor
It is made up of 0.6 or 0.7 mm wire . It consist of u loop , an active arm
and a retentive arm that is distal . It is used when minimum retraction
of 1-2mm is required . It is activated by closing loop by 1-2mm or
cutting the free end of active arm by 2mm and readapting.

46. • Helical canine retractor
It is also called reverse loop canine retractor and is made of 0.6 mm
wire . It consist of a coil of 3mm diameter , an active arm and a
retentive arm . It is activated by opening helix by 1mm or by cutting
1mm of free end and readapting it around the canine .

47. Buccal canine retractor
It is indicated in bucally placed canine and canines placed high in the
vestibule . They are used to move canine in distal as well as palatal
direction . It consist of a coil of 3mm diameter , an active arm and a
retentive arm .Buccal canine retractor are of two types
supported
self supported
Self supported are made of thicker gauge wire(0.7mm) so that the
spring can support itself and supported are made of thinner gauge wire
(0.5mm) thus they are more flexible and mechanically efficient

48. • Palatal canine retractoin
It is made up of 0.6mm wire . It consist of coil of 3mm diameter , an
active arm and a guide arm . It is indicated in canine that are
palatally placed . Activation is done by opening the helix 2mm at a
time .

49. • Screws
Screw are active component that can be incorporated in a
removable appliance . Screw can be activated by the patient at
regular intervals using a key .
Removable appliances having a screw usually consist of split
acrylic plate and adams clasps on the posterior teeth. The screw is
placed connecting the split acrylic plate .
screw key

50. Screw can bring about three types of movement :-
(a) expansion of arch .
(b) movement of one or a group of teeth in a buccal or labial
direction .
(c) movement of one or more teeth in a distal or mesial
direction

51. • Elastics
Elastics as active components are seldom used along with
removable appliances . They are mostly used in conjunction with
fixed appliances .

52. Base plate
The bulk of removable appliance is made of the acrylic base
plate . The prime function of the base plate is to incorporate all
the components together into the single function unit .

53. Uses of base plates in removable appliances :
(a) The base plate unites all the components of the appliance into one
unit .
(b) Helps in anchoring the appliance in place .
(c) It provides support for the wire components .
(d) Helps in distrubting the forces over a larger area .
(e) Bite planes can be incorporated into the plate to treat specific
orthodontic problems .
(f) Baseplate of 1.5 to 2mm thickness offers adequate strength.

54. • Avoidable complications of Removable appliance
1. Pain in teeth due to over activation o f the wire components. The
activation should be gentle and should not produce force of more
than 20-40 gm/ tooth.
2. Appliance activated, but tooth has no freedom to move. This might
result in severe pain, non-vitality and tooth extrusion.
3. Ulcers in the palate. Check for acrylic pimples on tissue surfaces of the
appliance. Acrylic pimples can be avoided by filling up air bubbles on
the working dental cast prior to acrylization.
4. Ulcers in oral cavity due to sharp ends o f wires. Check prior to
delivery outside the mouth. Check on delivery in patient’s mouth.
5. Gagging is usually due to over extended base plate, or a thick rough
appliance. Base plate should not compromise volume of the oral
cavity.

55. Summary
Removable appliances need a careful use and thoughtful
design by the clinician with regards to anchorage and type
of tooth movement required and therefore clear
instructions to the laboratory technician are a must. The
spring designs should be preferably drawn on the
laboratory requisition form with specified size of the wire
to be used for each of the components and modifications
from conventional design if any desired for individual
patients need.
Removable appliances do have a significant role in an
orthodontic armamentarium, particularly during
interceptive orthodontics, in conjunction with fixed
appliance therapy and during the retention phase.