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1. REMOVABLE APPLIANCES:
DESIGN AND USE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. Removable appliances
- can be taken out of the mouth for cleaning
by the patient and adjustment by the
orthodontist
- apply their forces by means of springs,
screws, and bows of various types
- can tip teeth only

3. REMOVABLE APPLIANCE
COMPONENTS
A
ACTIVE COMPONENTS
R
RETENTIVE COMPONENTS
A
ANCHORAGE
B
BASEPLATE

4. ANCHORAGE - DEFINITION
“For every action there is an equal and
opposite reaction” (Newton’s 3rd law)
“Resistance to unwanted tooth movement”
- Proffit, 1993
The area from which the force is applied
to move the teeth.

5. HOW TO CONSERVE / INCREASE
ANCHORAGE
1. Clasp more teeth
2. Move only one or two teeth at a time
3. Use lighter forces
4. Occlusal capping
5. Add headgear

6. FORCES TO MOVE TEETH
Single tooth movement: no more than 25 - 40
grams per tooth
Apply to the cervical margin of the tooth
to reduce the tipping tendency to minimum

7. RETENTION
- Achieved by clasps of various types
- Adams’ cribs - molars and premolars
- Southend clasps - incisors
- ball hooks - interdental embrasure

8. CLASP CONSTRUCTION
Adams’ cribs
- molar clasps in 0.7mm stainless
steel round wire
- premolar / deciduous clasps in
0.6mm wire
Southend
- 0.6 mm wire
Ball hooks
- 0.7 or 0.6 mm wire with soldered
ball on end

9. ACTIVE COMPONENTS
SPRINGS
- 0.5mm or 0.7mm wire to move
single teeth or groups of teeth
Constructed in 18/8 austenitic stainless steel
The more wire incorporated, the greater the
range of the spring and the lighter the force
exerted

10. FORCE AND DEFLECTION OF
STAINLESS STEEL SPRINGS
F = k .d .r4
l3
where
r = radius of the wire
d = deflection of the wire
l = length of the spring
k = stiffness of the wire (Young’s Modulus)

11. FORCE AND DEFLECTION OF
STAINLESS STEEL SPRINGS
Increasing the radius of the wire by 2 will result in
the force applied increasing by 16 times;
Increasing the length of the spring by 2 will reduce
the force applied by 8 times

12. FITTING A REMOVABLE APPLIANCE
1. Check that the appliance is the one for the patient!
2. Check acrylic for sharp edges (esp. in palatal rugae
area)
3. Fit appliance in patients mouth. Note any rocking,
or areas that do not fit and adjust if necessary
4. Tighten clasps and check retention
5. Activate springs and check that teeth are free to
move (trim acrylic if necessary)

13. FITTING A REMOVABLE APPLIANCE (cont’d)
6. Chat to the patient with appliance in place. Ask
about any discomfort
7. Give written and verbal instruction to patient and
parent. Normally removable appliances are worn
24 hours/day. Warn of initial discomfort, etc.
8. Dismiss patient and arrange next appointment

14. AT THE FIRST REVIEW VISIT:
1. Chat to patient and note speech with appliance in
place. Ask about any problems.
2. Check appliance out of mouth. Note loss of surface
lustre, tooth impressions on bite planes etc.
3. Check condition of mouth - palatal mucosa should
have indentation or redness if good URA wear. Note
any trauma from springs etc
4. Check position of teeth that are being moved and
the anchor teeth from the original study models

15. AT THE FIRST REVIEW VISIT (cont’d):
5. Teeth should be slightly mobile if movement is
occurring. If teeth are not moving, look for a cause
(acrylic in the way, insufficient activation of springs,
unerupted teeth, retained roots, etc)
6. Reactivate springs 1-2mm and tighten cribs.
7. Congratulate patient if appropriate and reappoint
* approx. 1mm of tooth movement should occur each
month

16. Clinical scenarios
•
•
•
•
1. Upper incisor behind bite
2. Class III incisors & deep bite
3. Increased OJ - extract 1st premolars
4. Palatal displacement of upper
premolar
• 5. Upper canine displaced buccally
• 6. Class 2 div 1 & compromised 6’s
• 7. Lower 2nd premolar impeded

17. PROBLEM 1: UPPER INCISOR INSIDE BITE

18. RETENTION: Adams cribs 6/6 and 4/4

19. Active component: Z-spring to 1/

20. BITE OPENING: Posterior bite capping to
654 / 456 (more comfortable
for patient)

21. BASEPLATE: to connect everything together, also
some anchorage

22. ACTIVATE THE Z-SPRING....

24. ...VOILA!

25. PROBLEM 2: All four incisors inside bite, with
deep reverse overbite

26. RETENTION: Adams cribs 6/6 and 4/4

27. ANTERIOR RETENTION: Southend clasp 1/1

28. ACTIVE COMPONENT: Expansion screw to
section 21/12

29. BITE OPENING: occlusal capping posteriorly

30. Screw is opened by one quarter turn twice a week
and pushes upper incisors forward over the bite

33. PROBLEM 3: Increased overjet, proclined incisors

34. Extract 4/4 to allow overjet reduction

35. RETENTION: Adams cribs on 6/6 ,
Southend clasp 1/1

36. ACTIVE COMPONENTS: Palatal finger springs 3/3
with wire guards for
stability

37. Trim acrylic
BITE OPENING: flat anterior bite plane

41. 3/3 at end of canine retraction

42. Canines retracted. Now the incisors
must be retracted

43. RETENTION: Adams cribs 6/6 with arrowhead
extensions to 5/5

44. Metal stops mesial to 3/3 to prevent these
teeth from moving forward

45. ACTIVE COMPONENT: Labial bow in 0.7 mm wire
with large U-loops to allow
activation

46. BITE OPENING: flat anterior bite plane

47. Labial bow activated 1-2 mm at each visit by
squeezing vertical legs of U-loops together.
Palatal acrylic must be trimmed away by the
same amount.

49. End of incisor retraction

50. Where canines are bucally placed, use buccal
canine retractors, made in either 0.7mm wire
or 0.5mm wire supported by 0.5mm internal
diameter tubing where it emerges from the acrylic

54. Canines can be pushed palatally into the
line of the arch as they move distally

55. The labial segment can be retracted also with a
0.5mm labial bow with tubing support.

56. ACTIVATION OF LABIAL BOW: Press the
vertical leg towards the tubing

60. Position of helix is very important - it must be
placed half-way between the starting position
of the tooth and the desired finishing position

61. Helix too far anteriorly - tooth will move palatally

66. Helix too far distally - tooth will move buccally

74. WHY IS IT NECESSARY TO REDUCE THE OVERBITE
BEFORE REDUCING THE OVERJET?
As incisors tip, the lower incisors prevent further
overjet reduction due to increasing overbite

75. By incorporating an anterior bite plane, the overjet
can be successfully reduced without increasing the
overbite as the incisors tip palatally

76. Trimming to allow the incisors to retrocline: trim on
palatal aspect, with bur parallel to palatal surface.
Don’t trim from the occlusal surface - reduces width
of bite plane excessively.

77. Bite opening - posterior teeth erupt into the space

78. PROBLEM 4: /5 deflected palatally,
/6 has drifted mesially

79. RETENTION: Adams cribs 6 / 46 ,
southend clasp 1/1

80. ACTIVE COMPONENT: Screw section to /6 ,
Z-spring to /5

89. PROBLEM 5: Buccally placed canine /3

90. Retention: Adams cribs 6/6 and 4/4

91. ANCHORAGE REINFORCEMENT:
Headgear tubes on 6/6

92. ACTIVE COMPONENT: Screw section to distalise
/456

93. ANCHORAGE REINFORCEMENT:
headgear to tubes on 6/6

101. Problem 6: Class II div 1, and both upper first permanent
molars are carious

102. Adams cribs on 73/37, finger springs 5/5 and
4/4, fitted labial bow 21/12

103. Extract 6/6

104. Retract 5/5 (with or without headgear support)

105. Retract 4/4

106. Adams cribs 74/47, finger springs 3/3,
Southend clasp 1/1

107. Upper 3/3 retracted

108. URA with labial bow to retract 21/12

113. Problem 7: an unerupted 5/ where extraction of
the 4/ would give too much space

118. FIN
...as they say at the end of all French films

119. Thank you
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