3. The retraction of upper
canines , with all the
available teeth involved in
the appliance. An equal and
opposite force to that being
generated by retracting
canines will also be acting on
the remaining upper arch
teeth to move them
anteriorly, which can
comprise the anchorage unit
causing unwanted tooth
movement of the rest of the
dentition.
5. Self supported buccal canine
retractor with helix located distal
to the long axis of the canine
Incorporating as many teeth as
possible in the appliance design
and covering the anterior palatal
vault will increase the anchorage
6. Mesially inclined canine being aligned using the helical canine retractor
Helical canine retractor
7. A clinical scenario is the retraction of upper canines using a fixed
appliance, with all the available teeth involved in the appliance.
An equal and opposite force to that being generated by retracting
canines will also be acting on the remaining upper arch teeth
to move them anteriorly, which can comprise the anchorage unit
causing unwanted tooth movement of the rest of the dentition
8. The effects of different force values during canine retraction. (a) The
correct force produces maximum canine movement and minimum
movement of the other teeth. (b) An excessive force may give reduced
canine movement and will result in undesirable movement of the
other teeth in the arch. An increase in overjet is a sign of this.
9. Assessment of anchorage during canine retraction.
(a) Initial occlusion
(b) Correct forces have been used
and the appliance worn as
instructed . Upper 3 has been
retracted into a satisfactory class
I relationship with lower 3 with
little increase in overjet.
(c) Anchorage loss is demonstrated.
No further retraction of upper 3 is
possible as the posterior teeth have
moved forwards and the overjet
has increased. It will not now be
possible to reduce the overjet fully
10. RESISTANCE TO TOOTH MOVEMENT (ANCHORAGE). Retraction of labial segment
If, following extraction of first
premolars, an attempt is made to
retract the entire labial segment at
once, the only teeth resisting this
movement are the four remaining
posterior teeth. It may be expected,
therefore, that the forward
movement of these teeth will
exceed the backward movement of
the incisors and canines
When the canines alone are
retracted the incisors take part
in the anchorage. Only two
teeth are being moved against
an anchorage of eight teeth.
Although these will inevitably
undergo some slight forward
movement, this will be small
compared with the distal
movement of the canines
The canines now being in the
fully corrected positions, an
appliance designed to retract
only the four incisors can
utilize all the six remaining
teeth as anchorage, so
producing a major movement
of the incisors with little
further forward movement of
these teeth.
11. An upper removable appliance
used to expand the upper arch
and procline retroclined upper
incisors.
Traction applied to an
exposed canine using a
removable appliance
12. Anchorage may be conserved in two main ways:
1. Keeping Forces Light
Removable appliances conserve anchorage well because they
allow simple tipping movements of the teeth which require
the lightest pressures. The reactionary force can be reduced by
limiting the number of teeth moved.
(a) Upper lateral incisor in cross-bite. (b)Upper removable appliance used to procline the lateral
incisor over the bite. (c)Corrected cross-bite
13. The force necessary to carry out a simple tipping move-
ment on a single rooted tooth is usually said to be in the
region of 30 to 50 g. There is a threshold of perhaps about
20 g below which movement does not occur.
1. Keeping Forces Light
(a) Unilateral cross-bite left side with an associated displacement of the mandible
to the left. (b) Upper removable appliance with midline screw. (c) Corrected
cross-bite (note correction of centre-line).
14. When a tooth is tipped with a
removable appliance, the fulcrum of
rotation is approximately 40 percent
of the length of the root from the
apex
Diagram showing the effect of
a tipping force applied to the
crown of a tooth (+ = pressure;
- = tension)
Tipping
movement
15. The intra-oral gauge is being used to measure the force applied by an activated
palatal finger spring
Examples of spring gauges. Both (a) extra-oral and (b) intra-oral
versions exist. The intra-oral gauge is being used to measure the
force applied by an activated palatal finger spring.
16. Our problem is to deliver sufficient force to move
the required teeth while ensuring that the
reactionary force, when divided among the anchor
teeth, is insufficient to cause movement.
1. Keeping Forces Light
20. Only one buccal tooth per quadrant should be moved
in the same direction at any one time and when an
overjet is to be reduced the incisors should not be
moved palatally while other teeth are being retracted.
1. Keeping Forces Light
21. Example of a labial bow with U-loops (a) from the front
and (b) occlusally. (c) .
22. Removable appliance with labial bow is
indicated for management of Protruded and
spaced occlusion with shallow overbite and
increased overjet due to thumb-sucking habit
Before Appliance for breaking
tongue thrusting habit
Placed in the mouth
23. Tightening the labial bow
across the U-loops results
in the anterior section of
the labial bow being
moved incisally; it must
therefore now be pushed
gingivally (arrowed; a) so it
once more rests in the
middle third of the labial
surface of the incisors.
Before the appliance is
fully inserted, the labial
bow should lie more or less
along the incisal edges (b);
so it has to be lifted over
the labial surface to sit
appropriately (c;
24. (A–C) The ACCO appliance is used for uprighting maxillary permanent
molars to regain space. To maximize anchorage, acrylic is flowed over the
labial arch wire and this limits the proclination of incisors as the molars
are distalized.
• Removable appliances – Acrylic cervical
occipital appliance (ACCO appliance)
25. T-springs drawn on the laboratory card (a) and an example of a
T-spring (b; arrowed) on this appliance (which also shows an
Adams’ clasp).
26. Z-springs drawn on the laboratory card (a) and an example
of Z-springs (b; arrowed) on this appliance (which also
shows C-clasps and Adams’ clasps)
27. Nevertheless it is unwise to assume that
anchorage loss will be completely
avoided merely by the use of light forces
1. Keeping Forces Light
28. 2. Increasing the Resistance of the Anchor Teeth
The Base Plate
The resistance offered by the fit of the base plate against the teeth and mucosa
contributes to the good anchorage offered by removable appliances. This may be
maximized by keeping the acrylic fitted around as many teeth as possible.
29. Correction of an anterior crossbite with a
n upper removable appliance
2. Increasing the Resistance of the Anchor Teeth
A-The Base Plate
30. Caspal Interlock
It seems likely that good cuspal interlock with the teeth of the
opposing arch will offer added resistance to any anchorage loss.
A problem, however, is that extractions in the opposing arch
may allow the interlocked teeth to move mesially together..
Tongue thrusting:
(a and b)
Removable plate
with palatal crib
which were bent
posteriorly to
avoid lower
interference.
31. The helpful effects of cuspal interlock may be eliminated by lower extractions or the use
of bite planes.
Further, when bite planes of any sort are used,
cuspal interlock ceases to be effective
Caspal Interlock
33. A. When the mandible is brought
into centric occlusion, the lower
incisor is slided over the guide
plane to bring the mandible
forward. This may be act as
mandibular repositioning splint; B.
Upper anterior inclined plane
34. ANTERIOR INCLINED BITE
PLANE Instead of being flat,
the bite plane is inclined it
faces downwards and
forwards at an angle of 60°
to the occlusal plane and
engages the lower incisors
and canines when the jaws
are approximated guiding
the mandible forward. The
inclined bite plane reinforces
the anchorage and proclines
the lower anterior teeth in
addition to the correction of
anterior deep bite
37. Anterior bite
plane with
capped maxillary
incisor to give an
additional
anchorage to the
maxillary plate
A clearance of 1.5 to 2 mm should exist
between the upper and lower posterior
teeth
41. The traditional
textbook view
claims that the
significant vertical
separation between
the palatal acrylic
and the labial wire
increases the
anchorage value of
the incisor teeth by
establishing a
rotational force
couple.
The sagittal
section of a
model
demonstrates
the minimal
vertical
separation of
wire and
acrylic
42. Long labial bow is a modification
of short labial bow where in the
bow extends from left first
premolar to right first premolar .
Thus, greater length of the wire
used allows greater anterior
retractoin as compared to short
43. Fitted labial bow A short fitted labial bow on upper central incisors
(0.7 mm wire). This design permits some drifting
of the lateral incisors as the canines are retracted.
44. A removable appliance with a
finger spring can be used to regain
space by tipping a permanent first
molar
distally. A, The appliance
incorporates multiple Adams'
clasps and a helical spring that is
activated 1 to 2 mm per month. B,
Premature loss of the primary
second molar has led to mesial
drift and rotation of the
permanent first molar. C, This
removable appliance can be used
to regain up to 3mm of space. D,
After space regaining, the space
should be maintained with a band
and loop or lingual arch if the
permanent incisors have erupted
tipping the permanent first molar
distally
45. Palatal finger springs to distalize maxillary first
molars to recreate space following early loss of
primary molars
46. A removable appliance can be used in the mixed dentition to retract
spaced and protruding anterior teeth. A, The labial bow is activated
1.5 to 2 mm and will achieve approximately 1 mm of retraction per
month as the maxillary anterior teeth tip lingually. At each
appointment, the labial bow should be adjusted and lingual acrylic
removed to provide space for the tooth movement. B, A near normal
occlusion in the late mixed dentition
49. Retraction headgear fitted to a
removable appliance. Locking facebow (a) closed (b) attached to
clasp of upper removable appliance
50. Children with a long face pattern generally have a maxilla rotated
down posteriorly with short mandibular ramus. The ideal treatment
in these patients will be to control all posterior vertical growth. This
can be accomplished by high pull headgear attached to molars or
maxillary splint
Max. splint with headgear
51. Orthodontic headgear consisting of
the facebow and black nylon straps
that fit around the patients head to
keep the device in place
55. a) Mixed dentition patient with maxillary midline diastema. (b, c) A removable appliance
with finger springs was used to close the median diastema. (d) Note the close proximity
of the erupting right maxillary canine with the root of the lateral incisor. Because of the
risk of root resorption, mesial tipping of the lateral incisor was avoided
56. Forward movement of the buccal
teeth produces prominence of the
second premolars unless the arch
width is reduced.
58. Anchorage planning is about resisting unwanted tooth movement. Whenever
teeth are moved there is always an equal and opposite reaction. This means
that when teeth are moved there is often a side-eff ect of unwanted tooth
movement of other teeth in the arch. When planning a case it is therefore
important to decide how to limit the movement of teeth that do not need to
move. It is vital that anchorage is planned correctly for a treatment plan to
work .
59. References
1- An Introduction to orthodontics- Laura Mitchel
2-Tooth Movement with Removable Appliances - Muir And
Reed 1979
3-The design, construction and use of removable Orthodontic
Appliances – Adams
4-Removable Orthodontic Appliances - Vijayalakshmi – 2010
5-Orthodontic Retainers and Removable Appliances – 2013
6-Orthodontic Removable Appliances - Talmale