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1. REMOVABLE APPLIANCES:
DESIGN AND USE
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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3. 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

4. REMOVABLE APPLIANCE
COMPONENTS
•ACTIVE COMPONENTS
•RETENTIVE COMPONENTS
•ANCHORAGE
•BASEPLATE

5. 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.

6. 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

7. 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

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

9. 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

10. 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

11. 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)

12. 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

13. 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)

14. 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

15. 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

16. 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

17. Clinical Scenarios
•These are designed to facilitate the understanding
of which components carry out which functions
during removable appliance therapy; and also to
provide diagramatic illustrations of the various
components to facilitate the instructions to the
orthodontic laboratory technician.

18. 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

19. PROBLEM 1: UPPER INCISOR INSIDE BITE

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

21. Active component: Z-spring to 1/

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

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

24. ACTIVATE THE Z-SPRING....

26. ...VOILA!

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

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

29. ANTERIOR RETENTION: Southend clasp 1/1

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

31. BITE OPENING: occlusal capping posteriorly

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

35. PROBLEM 3: Increased overjet, proclined incisors

36. Extract 4/4 to allow overjet reduction

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

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

39. Trim acrylic
BITE OPENING: flat anterior bite plane

43. 3/3 at end of canine retraction

44. Canines retracted. Now the incisors
must be retracted

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

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

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

48. BITE OPENING: flat anterior bite plane

49. 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.

51. End of incisor retraction

52. 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

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

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

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

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

63. Helix too far anteriorly - tooth will move palatally

68. Helix too far distally - tooth will move buccally

76. 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

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

78. 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.

79. Bite opening - posterior teeth erupt into the space

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

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

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

91. PROBLEM 5: Buccally placed canine /3

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

93. ANCHORAGE REINFORCEMENT:
Headgear tubes on 6/6

94. ACTIVE COMPONENT: Screw section to distalise
/456

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

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

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

105. Extract 6/6

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

107. Retract 4/4

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

109. Upper 3/3 retracted

110. URA with labial bow to retract 21/12

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

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

147. SMILE
HAVE A GOOD DAY