Lab pdf - عملي - Muhadharaty

considered  as  an  interceptive  orthodontic  treatment  and
is  mostly  used  in  mix  dentition  period.  Basically,  they
either  resolve  the  treated  dental  problem  or  diminish  its
severity.  Either  way,  this  is  definitely  beneficial  to  the
patient.  However,  this  is  a  patient-dependent  protocol
and  stability  of  the  appliance  in  place  is  vital.  The
stability is accomplished mainly by retentive components
(clasps)  attached  to  the  appliance.  Fulfillment  of  the
treatment  objectives  requires  a  substantial  mechanical
concept and designing.

Biomechanics of Tooth movement

When a force is applied to the crown of a tooth, it

will  displace  slightly  within  the  confines  of  the
periodontal  ligament.  This  small  change  in  position  will
set  up  areas  of  tension  and  compression  within  the
periodontal  ligament.  Provided  that  the  force  is  applied
over a sufficient period of time, remodeling of the socket
will allow the tooth to move farther.

Types of tooth movements:

1. Spontaneous tooth movement: include tooth

movements that occurs spontaneously without
orthodontic force application, An example of this is

tipping toward an extraction space or over eruption
of teeth opposite to an extracted tooth.

2. Active tooth movement: these movements which

occur due to application of orthodontic force to the
crown of the tooth. Active tooth movement could be
sub-categorized into the following:

a. Tipping Tooth Movement: When a force is

applied  at  a  single  point  on  the  crown  trying  to
move  the  tooth,  the  alveolar    bone  will  resist  that
movement  which  will  result  in  tipping  of  the  tooth
around  its  center  of  rotation  (about  40%  of  root
length  apically).  This  means  that  while  the  crown
moves  in  one  direction  the  root  apex  will  move  in
the opposite direction.

b. Translation (Bodily) Tooth Movement: When all

parts of the tooth move in the same direction for the
same  distance.  If  a  tooth  is  to  be  moved  bodily,  a
force  couple  must  be  applied  to  the  crown  in
conjunction  to  the  original  force.  This  is  not
practically  applicable  with  removable  appliance
since it is difficult to control the M/F ratio along the
course of tooth movement.

c. Intrusion and Extrusion tooth movement: Is a

translational movement parallel to the long axis of
the tooth.

d. Rotational movements: Rotation of the tooth

around  its  long  axis.  To  achieve  this  type  of  tooth
movement,  the  application  of  couple  force  is
required.

Construction of removable appliance

Removable  appliances  are  made  in  dental  laboratories.
However,  learning  the  basic  construction  techniques  is
essential to master the various applications and mode of
action of each of the components.

Components of removable appliance:

1. Active components: The active components are used

for  the  application  of  orthodontic  force  to  the  teeth
and  are  made  mainly  from  stainless  steel  wires  and
Screws  and  elastics  are  also  used  in  removable
appliance  but  less  frequent.  An  example  is  the  Z
spring.

2. Retentive components: Those components that are

used  to  provide resistance  of  the  dislodgement  of  the
appliance  from  the  mouth.  For  example  of  that  are
different types of clasps labial bows.

3. Acrylic base plate: Is the basic frame to which all

active  and  retentive  components  are  attached  directly
or  indirectly.  In  addition  to  its  function  as  the  main
frame  it  also  plays  an  impotent  role  as  an  active
component. for example when modified as an anterior
bite  plate  to  treat  deep  bite  cases,  also  considered  as
an  impotent  retentive  component  as  its  adaptation  to
the palate and the engagement to the palatal undercuts
of the molars and premolars will increase the retention
of the appliance.

Essential construction tools

For the vast majority of removable appliances the

usual set of instruments and materials are composed of:

1. Orthodontic pliers and cutters



Orthodontic pliers

These are used for all wire bending. The ends are

firm,  tapered,  with  one  round  end  and  the  other
pyramidal  or  2  rounded  in  section,  and  meet  only at  the
tips.  The  beaks  meet  only  at  the  tips  so  that  they  are
separated  about  O.6  mm  at  the  base  when  the  pliers  are
closed.  This  makes  the  beaks  of  the  Universal  pliers
parallel when gripping the wire.
Tow famous pliers of this type are:

a) Angle pliers (coil forming pliers): with one cone-

shaped beak and one pyramidal beak.

b) Adams pliers (universal pliers): with two

pyramidal beaks.



Orthodontic wire cutters

The diagonal type of wire cutter is used and must have
hardened blades.

2.  Stainless steel wire;
These  are  used  to  make  the  active  and  retentive
components.  they  can  be  classified  according  to  its
hardness to:



Extra-hard



Hard (used in removable appliances)



Soft

The  wires  gauge  range  between  0.3-1.5  mm;  in
removable appliances we use 0.5 - 0.7 mm hard stainless
steel wire.

3.  Acrylic:
This is used for construction of the frame or the body of
removable  appliance  that  carry  the  active  and  passive
springs.  Chemical  cure,  light  cure  or  hot  cure  acrylic
could be used. Colures and additives are preferable.

4.  Patient’s dental cast model:
A pair of dental cast model (upper and lower arches) for
the  patient  should  be  present  when  constructing  the
removable  appliance.  These  are  necessary  for  treatment
plan and construction of the appliance.

Manual training:

The students are instructed to make the following shapes
(Figure:  1)  using  0.6  or  0.7  stainless  steel  wire.
Meanwhile instructions about the correct pliers grasping,
wire bending and cutting are being given.
Those  shapes  will  introduce  the  student  to  the  manual
skill of wire bending and help him/her to manage  future
wire works accurately.

Figure

1 the students are

instructed to make the shapes
of : A. Straight wire piece;
B. 90 degree angle; C.
Straight wire with coil; D. 90
degree angle with coil; E.
Full turn coil; F. three well
aligned vertical loops on the
same wire.

Lab:2.

The palatal finger spring

Description and design

The simplest form of this spring is a strait piece of

wire embedded at one end in the acrylic base plate. The
usual wire diameter is 0.5 mm or occasionally 0.6 mm. a
coil  is  incorporated  near  the  point    of  insertion  into  the
acrylic,  this  increase  the  length  of  the  wire  and  stores
activation  energy,  thus,  it  will  help  delivering  a  light
force over a longer range of action (figure:2A). The coil
should be made as large as possible 3- 4mm . It is placed
so  that  when  activated  it  is  tightened  (the  coil  is  placed
on the side away from the desired tooth movement).

A coil spring of this design will usually be about 2

cm in length from the point of force application to the
insertion into the acrylic. The position of the coil
(distance from the tooth) is most important as it influence
course of action in which the spring works.

Indications:

It is commonly used to move any tooth mesially or

distally along the dental arch

Advantages:

1. Simple design
2. Provide light pressure
3. Well tolerated by the patient
4. Several springs can be added if required

Disadvantages:

- The palatal finger spring can not move teeth in

labial or palatal directions.

Step by step construction of finger spring

1. With a sharp pencil, sketch the design of the wire on

the cast model according to the (description and
design) mentioned above.

2. Cut a (5cm) of ( 0.5mm) round stainless steel wire
3. straighten off the wire piece
4. Make a very small loop ( as small as possible) at one

end  of  the  wire  and  then  bend  it  to  be  (  90°  )to  the
spring  long  axes.  This  will  be  the  tooth  end  of  the
spring  and  will  help  tooth  engagement  and  prevent
injury from sharp wire terminal.

5. Adapt the wire on the cast model so that the tooth end

is  fit  on  the  tooth  side  opposite  to  the  direction of  the
desired  tooth  movement  and  the  spring  long  axes  is
perpendicular  on  the  direction  of  tooth  movement.
Then  measure  about  (*15  mm)  from  the  tooth  end  of
the wire and put a mark on the wire.

6. Hold the wire on the mark. The round beak of the plier

should  be  held  away  from  the  operator  and  from  the
first  bend  made  on  the  wire,(  keep  in  mined  that  the
coil  will  always  be  away  from  the  direction  of  the
desired  tooth  movement).  Start  rolling  over  the  wire
around  the  round  beak  of  the  pliers  until  forming  a
complete  coil,  and  the  wire  continues  in  the  same
direction.

7. Make sure that the coil will be above the tooth end

(active arm) of the spring. This is a critical point of the
wire design since it will keep the active arm close to
the palate.

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

8. Re-adapt the spring on the cast model and check the

following points:

a) The spring fits on the side of the tooth away from

the direction of tooth movement

b) The coil is on the side away from the direction of

tooth movement

c) The coil is above the active arm

9. Leave about (4mm) from the coil end and mark the

wire. This is the point where the wire will start to be
embedded in the acrylic.

10. About (2mm) after this point, make a (45°) bend on

the round beak of the pliers and start a 2 to 3 ( zigzag )
bends  that  is  the  retentive  part  of  the  wire  which  will
provide  the  mechanical  retention  of  the  spring  in  the
acrylic base-plate.

11. Cut the excess of the wire and adapt it on the cast

model with piece of soft wax. and check the fallowing
points:

a) The length of the spring is about 2 cm from the

tooth end to the point of insertion into the acrylic.

b) The retentive zigzag does not cross the midline to

the opposite side.

Boxing, Open spring and Wire guard:

These are three designs of the acrylic base plate

around the finger spring.  Boxing (figure:2B) is designed
to  provide  the  freedom  of  movement  of  the  active  arm
and coil inside an acrylic chamber built in the base-plate.
Open  spring  (figure:2C)  is  designed  to  completely
remove the acrylic of the base-plate from the path of the
movement  and  leave  the  active  arm  and  the  coil  free
without  protection.  Wire  guard  is  the  addition  of  a
stainless  steel  wire  be  incorporate  in  the  open  spring
design to prevent distortion of the spring during wearing
and  activation.  This  could  be  from  the  tongue  side  or
occasionally from  palatal  side  too.  It  could  also  be  used
with  the  boxing  design  palatally  for  the  same  reason.
Those three designs will be discussed thoroughly in base
plate construction labs.

Activation

It is widely believed that for a single rooted tooth a

force  of  30  to  50  g  is  enough  to  produce  orthodontic
tooth  movement  with  minimal  tipping.  A  tension  gauge
could  be  used  to  measure  the  force;  however  the  usual
activation  is  roughly  one  third  to  one  half  of  a  unit  (the
mesio-distal  dimension  of  the  tooth).  This  is  about  3-5
mm. Over activated springs may be harmful to the tooth
producing pain and discomfort to the patient (figure:2).

The palatal finger spring is activated by gentile

opining  of    the coil  with  the  use  of angle  pliers  the  old
position of the tooth end of the spring (before activation)
is  marked  on  the  base  plate  to  be  compared  to  the  new
position (after activation).

A B

C D

Figure

2 the palatal finger spring. A: palatal figure spring design ; B: boxing with wire guard ;

C: open spring ; D: activated finger spring.

Lab:3.

Modified finger spring

One of the modifications to the palatal finger spring

is the modified finger spring. it differs from the original
one  in  four  main  points:  Its    action  is  applied  labially
rather than palatally; It crosses the occlusal surface; The
direction  of  force  is  vertical  and  it  needs  an  attachment
(usually orthodontic bracket ) on the labial surface of the
tooth in order to apply its action ( figure 3).

The gauge of the wire is 0.5mm or 0.6mm, a loop is

incorporate in the wire design to increase the length of
the wire and its range of action.

Indications:

For extrusion for ectopic or high buccally erupted teeth

Advantages:

1. Simple design
2. Suitable range of action

Disadvantages:

3. Can not be boxed or guarded.
4. Subjected to distortion.
5. Trauma to the vestibular soft tissues.

Step by step construction

1. On the plaster model, sketch the wire design on the

labial gingiva (figure 3). The end of the active arm

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

usually  located  at  the    mesial  margin  of  the  target
tooth and extended distally passing over the tooth to
be  moved  in  addition  to  two  teeth  behind.  This  will
be  about  3  mm  above  the  gingival  margin.  At  that
point a small loop 3-4mm in diameter is  constructed
by  which  the  wire  will  change  its  direction
occlusally,  crossing  the  occlusal  surface  at  the
embrasure  between  the  teeth  and  rolling  over  to  the
palatal  side  of  the  arch  where  the  spring  ends  by  a
retentive zigzag form.

2. Cut about 7 cm of 0.5 mm round stainless steel wire
3. Straighten the wire piece
4. Start to form a very small loop at one end of the wire,

this will be the end of the active arm of the spring
and will prevent injury to the adjacent soft tissue

5. Adapt the wire to the curvature of the alveolar arch.

Fit  the  wire  in  position  and  put  a  mark  on  the  distal
margin  of  the  third  tooth    (according  to  the  design
drawing).

6. Hold the wire with the pliers 2 mm behind the mark

point  and  start  to  form  a  3-4mm  loop.  The  direction
of  the  loop  is  always  away  from  the  tooth  to  be
moved (that’s mean the coil will try to open while it
is in action).

7. The coil will not take a complete turn and the wire

leaves the coil at aright angle to the direction of the
active arm and will be directed occlusally.

8. Fit the wire in position and check the following

points:

a. The length of the active arm is appropriate.
b. The lop is above the active arm.

c. The wire is adapted to the alveolar mucosa (

1mm away from mucosal surface).

d. The active arm runs 2-3 mm above the gingival

margin.

9. After the necessary correction have been made, Fit

the wire in  position  and  put  a  mark on the occclusal
end of the embrasure where the wire will pass above
the  occlusal  surface  of  the  teeth.  And  use  the  round
beak  of  the  angle  pliers  to  make  a  sharp  turn  to  the
palatal side of the dental arch.

10. Adapt the wire on the palatal surface of the teeth

and mucosa

11. Start to make a retentive zigzag bends starting at

the point about 2mm after the lingual gingival margin
where the acrylic base plate will be located, and then
cut the excess wire.

12. Fit the wire in position and check the fallowing:

a. The wire does not interfere occlusally with the

opposing arch.

b. The spring does not cross the midline
c. The loop does not interfere with the vestibular

tissues.

13. Now to finish the spring a small bend is made on

the active arm
(about 10 degrees) at the distal margin of the targeted
tooth  gingivally.  This  bend  will  ensure  correct
direction  of  the  applied  force  during  the  course  of
action.

Activation:

Activation of the modified finger spring is made by

opining the coil so that the active arm will be about 3

mm occlusally to the passive position (figure: 3B). This
will deliver force of about 20-30g which is enough for
extrusion movement.

. A

3-4 mm

2-3 mm

3 mm

Figure

3 The modified finger spring( Basic design .A:basic design; B: Activation

Lab:4 . Z-Spring ( double cantilever)

This is a variant of the palatal finger spring and the

commonest type in this group.

Description:

The spring is bent into the shape of the letter ' Z '

with two coils each is (2 mm) in diameter. It should be
constructed with the spring compressed. The presence
of two coils makes it possible for the active end of the
spring to be activated in a straight line perpendicular
to the dental arch.

Indications

1. Correction of single palatally Positioned anterior

tooth.

2. Correction of simple rotation ( not more than 45° )

when combined with active labial arch to produce a
couple force.

Advantages

1. The spring is compact and may be narrowed to

small teeth such as lateral incisors.

2. The force is delivered in a straight line due to the

presence of two coils.

3. The spring could be boxed and distortion is not

common.

Disadvantages:

1. Not suitable for posterior teeth.
2. If the spring is made very small it can produce an

excessive force during activation.

3. The reactionary force from the cingulum tends to

displace the anterior part of the appliance, good
anterior retention is therefore essential.

4. May produce some intrusive force.

Step by step construction procedure:

1. Start sketching the design of the spring on the

palatal  surface  of  the  cast  model.  The  spring  name  is
self explanatory as it will take the shape of the letter (
Z  )  (figure:  4A).  The  spring  is  confined  to  the  mesio-
distal  dimension  of  the  tooth  to  be  moved.  starting  at
the mesial border of the tooth, draw a straight line 2-3
mm  above  the  palatal  gingival  margin  crossing  the
tooth to the distal side, at that point a coil of 2 mm in
diameter is placed, make sure it will be confined to the
tooth  borders,  then  continue  the  line  in  reverse
direction gingival to the coil till the mesial side of the
tooth, at that point another coil of the same dimension
is placed, also make sure that the spring is confined to
the  mesio-distal  dimension  of  the  tooth,  now  continue
the  line  back  in  reverse  direction  gingival  to  the  coil
passing about 2 mm ( nearly at the middle of the tooth
dimension  where  a  sharp  turn  is  made  to  change  the
direction  posteriorly  ,  the  line  then  continues  straight
about 6 mm then start 2 to 3 zigzag retention form.

2. Take a (5 cm) piece of a (0.5mm) stainless steel wire

and straighten it.

3. Start by making a small loop ( as small as possible) at

one of the wires ends, this will be the active end of the
wire.

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

4. assuming that the z-spring is mad for the upper left

permanent incisor, put the wire on the palatal surface
of the tooth with the small loop is pointing mesially
and mark the point at the distal margin of the tooth.

5. Hold the wire about (1 mm ) before the mark point and

start  forming  the  loop.  The  size  of  the  loop  is  very
small  in  that  the  wire  must  be  held  at  the  very  end  of
the  pliers  beaks,  makes  sure  that  the  coil  is  above  the
active arm ( the wire end) this will facilitate the correct
direction  of  the  applied  force,  make  a  complete  turn
heading backward mesially.

6. Re-fit the wire in position and mark the mesial end of

the tooth (the mesial and distal end represents the
largest mesio-distal dimension of the tooth).

7. Repeat the coil just the same as the previous one except

that the coil here is above the remaining wire, this will
facilitate  easier  adaptation  of  the  spring  to  the
curvature  of  the  palate.  Complete  the  turn  so  that  the
remaining  wire  is  pointed  distally  again.  Make  sure
that the two coils are at the same plain.

8. Re-fit the wire in position according to the sketching

and mark the wire about (2 mm) away from the second
coil (nearly at the meddle of the mesio-distal
dimension of the tooth).

9. Hold the wire just before the mark point and make a

90° bend (on the round beak) at the same plain with the
coils. This will leave the remaining wire pointing
backward.

10. Leave about (6 mm) and start a retentive zigzag

bends, then cut the remaining wire.

11. If the coils are loose and were opened during

construction, squeeze the spring i.e. close the coils to

the maximum is mandatory since it will increase the
range of action during the active treatment.

12. Now the spring is completed in shape but is parallel

on the tooth surface and not useful. The active part of
the  spring  must  apply  the  force  perpendicular  to  the
tooth long axes (figure 4B). This is made by a rounded
bend  at  the  start  of  the  (6mm)  straight  area  of  the
spring wire just after the 90 degrees bend; the direction
of  the  bend  is  toward  the  palatal  surface  which  will
elevate  the  coils  to  be  perpendicular  to  the  tooth  long
axes. This bend could be combined with the 90 degree
bend to produce the desired orientation.

13. Be aware that the tooth long axes is not the palatal

surface of the tooth, it is represented on the cast model
by an imaginary line passing between the labial and the
palatal tooth surface.

14. the spring is then boxed with wax ( same as in

finger spring ) and ready for the construction of the
acrylic base plate

Activation:

There are two methods for the activation of Z-spring

a. By opining the first coil or the second coil alone, it will

produce force at one side of the tooth which will try to
rotate it.

b. By opining both of the coils which is practically done

by  gentile  pulling  of  the  active  arm  to  produce
elongation of the spring about (2-3 mm). This is quite
enough  for  tipping  movement  and  keeping  the  active
arm  parallel  to  the  tooth  surface  which  will  produce
equal force on both sides of the tooth.

                             A                                        B

Figure

4 The Z spring A:Z- spring positioned on the lateral incisor ; B: the z-spring is

positioned perpendicular to the tooth long axes.

Lab:5 Double Z-Spring

This spring is simply tow Z-springs joined by their

active arms.

Description:

The spring is bent into the shape of two ' Z '

facing each other (figure:5) with four coils each one is
(2 mm) in diameter. It should be constructed with the
spring compressed and the presence of two coils on
each side of the spring makes it possible for the active
end of the spring to deliver the force in a straight
perpendicular to the dental arch.

Indications

1. Correction of up to four palatally Positioned anterior

teeth.

2. Correction of simple rotation ( not more than 45° )

when combined with active labial arch to produce a
couple force.

Advantages

1. The force is delivered in a straight line due to the

presence of four coils.

2. The spring could be boxed and distortion is not

common.

3. Used for correction of more than one tooth, (2-4)

anterior teeth at the same time.

Disadvantages:

1. Not suitable for posterior teeth,

2. If the spring is made very small it can produce an

excessive force during activation.

3. The reactionary force from the cingulum tends to

displace the anterior part of the appliance, good
anterior retention is therefore essential.

4. May produce some intrusive force.

Step by step construction procedure:

1. Assuming that the double Z-spring is made for the two

upper  permanent  central  incisors,  sketch  the  design  of
the  spring  on  the  palatal  surface  of  the  cast  model  as
shown in (figure:5) . The spring will take the shape of
two  (Z)  facing  each  other  and  joining  by  their  active
arms with four coils of 2mm in diameter.

2. Take a (15 cm) piece of a (0.5mm) stainless steel wire

and straighten it.

3. Put the wire on the palatal surface of the teeth with and

mark two points one on each side at the distal margins
of the teeth.

4. Hold the wire about (1 mm) before the mark points and

start  forming  the  loop  from  each  side.  The  size  of  the
loop  is  very  small  (2mm)  so  the  wire  must  be  held  at
the  very  end  of  the  pliers  beaks,  make  sure  that  the
coils are above the active arm as this will facilitate the
correct direction of the applied force, make a complete
turn heading backward mesially from both sides.

5. Re-fit the wire in position, the active arm (which is the

segment of the wire between the two coils) must have a
slight curvature representing the normal arch form.

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.
.

6. Mark the mid-point between the two centrals, let the

mark appear on both the right and the left ends of the
wire.

7. Repeat the coil from each side just the same as the

previous one except that the coil here is under the wire
(the  short  piece  of  wire  between  the  first  and  second
coil  from  each  side),  this  will  facilitate  easier
adaptation of the spring to  the curvature of the palate.
Complete  the  turn  so  that  the  remaining  wire  is
pointing distally from each coil and heading away from
each  other.  Make  sure  that  the  four  coils  are  at  the
same plain.

8. Re-fit the wire in position according to the drawing and

mark the wire about (2 mm) away from the coils at
each of the two ends (nearly at the middle of the
mesio-distal dimension of the tooth).

9. Hold the wire just before the mark point and make a

90° bend (on the round beak) at the same plain with the
coils. This will leave the remaining wire pointing
backward to the palate.

10. Now leave about (6 mm) and start a retentive zigzag

bends then cut the remaining wire.

11. I case the coils are loose and opened during

construction,  squeezing  of  the  spring  i.e.  closing  the
coils  to  the  maximum  is  mandatory  since  it  will
increase the range of action during the active treatment.

12. Now the spring is completed in shape but is adapted

on the tooth surface and not useful. The active part of
the  spring  must  apply  the  force  perpendicular  to  the
tooth long axes. This is made by a rounded bend at the
(6mm) straight area of the spring wire just after the 90
degrees  bend,  the  direction  of  the  bend  is  toward  the
palatal  surface  which  will  elevate  the  coils  to  be

perpendicular  to  the  tooth  long  axes.  This  bend  could
be  combined  with  the  90  degree  bend  to  produce  the
desired orientation.

13. The spring is then boxed with wax ( same as in Z-

spring spring ) and ready for the construction of the
acrylic base plate

Activation:

Activation of the double Z-spring is made By

opining  both  of  the  coils  on  each  side  which  is
practically  done  by  gently  pulling  of  the  active  arm
from  the  right  and  left  side  to  produce  elongation  of
the  spring  about  (  2-3  mm  ).  This  amount  is  quite
enough  for  tipping  movement.  Pulling  the  same
amount from the right and left side will keep the active
arm parallel to teeth surface which will produce equal
force on both sides.

Figure

5 Double Z- spring positioned on the central incisors, note that the

active arm has a slight curvature representing the normal dental arch curve.

Lab:6. T- Spring .

Description:

The name is self explanatory as the spring take

the  shape  of  the  letter  (T).  Both  ends  embedded  into
the base plate and the T shape span rests on the palatal
surface  of  the  tooth  to  be  moved  (figure:6).  The
addition of extra u shape loops half way up the spring
increase  its  flexibility  and  provides  spare  wire  for  its
extension during tooth movement.

Indications

1. Suitable to provide buccal movement of posterior

teeth.

2. Occasionally used on the anterior teeth since it will

produce an inevitable intrusive force during action.

Advantages

1. Highly unlikely to catch on the buccal surface of

posterior teeth during insertion.

2. It occupies only a small space and can be used on a

premolar concurrently with other movements such as
canine retraction.

3. Could be boxed or guarded.

Disadvantages:

1. When used for anterior teeth, a considerable amount

of intrusive force is delivered.

2. It has a small range of activation.

Step by step construction procedure:

1. Two important points must be kept in mined during

the construction of this spring:

a. All the bends and loops must be at the SAME

PLANE

b. SYMETRY between the right and left side is

of a primary importance.

2. Sketch the design of the wire on the palatal surface as

shown in (figure 6)

3. Take a (5 cm) piece of 0.5mm stainless steel wire

(0.6mm for molars) and start straighten it.

4. Put the wire on the palatal surface of the tooth and

mark two points one on each side at the mesial and
distal embrasure around the tooth.

5. Hold the wire about (1 mm ) before the mark points

and  start  forming  the  U  shape  loop  from  each  side.
The size of the loop is very small (2mm) so the wire
must  be  held  at  the  very  end  of  the  pliers  beaks,  the
loops  are  incomplete  (  U  shape)  and  the  wire  only
turn  to  the  opposite  side  from  each  end  heading
backward toward each other from both sides.

6. Put the spring on the occlusal surface of the tooth, the

active arm (which is the piece of the wire including
the two loops must have the same mesio-distal width
of the tooth.

7. Now mark the mid point between the two loops , let

the mark appear on both the right and the left ends of
the wire

8. Then make a sharp turn (on the round beak of the

pliers) about (1mm) ahead to the mark point from

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

each side so that the two wire ends will extend
parallel to each other heading away from the T span
with (0.5 to 1 mm) between them ( figure 6).

9. Now the spring resembles the desired T shape and

you can make the retentive zigzag form about 6 mm
away from the loops. If additional loops is to be
added then the following additional steps are taken.

10. Mark a point about 3-4mm down the first loop and

let the mark appear on both sides of the wire.

11. Hold the wire with the ends of the beaks and make a

90  degree  bend  on  each  of  the  two  sides  of  the  wire
ends so  that  the  two  ends  run  apart  from  each  other.
Make  sure  that  all  the  bends  and  loops  used  in  the
construction of this loop must be at the same plain.

12. Hold the wire at the ends of the pliers beaks and

start making another (U) shape loops on each side
then follow the same steps of the first loop.

13. Unlike previous springs, this one lie parallel to the

palatal tooth surface. The active arm touches the
tooth on the gingival third of the palatal surface and
the spring has a slight curvature keeping it away from
the palatal soft tissue.

14. The spring is then boxed with wax ( same as in Z-

spring spring ) and ready for the construction of the
acrylic base plate

Activation:

Activation of the T-spring is made by gentile

pulling of the spring away from the base-plate toward
the  tooth  about  2-3mm  Which  is  quite  enough  for
tipping  movement.  To  compensate  for  the  positional
change  during  the  progress  of  the  treatment,  opening
the coils by gentile pulling of the active arm from the
right  and  left  side  to  will  produce  elongation  of  the
spring about (1-2 mm ) and

Figure

6 T- spring positioned on the second

premolar (occlusal view)

Lab:7. The Buccal Canine Retractor

Description:

The buccal canine retractor is composed of a

posterior  arm  which  emerges  palatally  from  the  acrylic
base  plate  and  crosses  the  occlusal  line  up  into  the
vestibule  to  support  a  coil  from  which  the  (L)  shaped
active arm (Singh 2007) is extended on the middle of the
crown  (mesio-distally)  and  curved  to  engage  the  crown
mesially  (figure:7),  It  is  usually  made  of  0.7mm  wire.
The  coil  must  be  3-5  mm  in  diameter  and  situated
roughly  on  the  line  representing  the  centre  of  the
extracted first premolar space. Care must be taken for the
coil  not  to  interfere  with  the  vestibular  tissues,  for  that
reason  the  coil  must  be  in  position  no  less  than  2  mm
short from the sulcus depth. The end of the active arm is
preferred  to  have  a  small  loop  to  prevent  injury  during
insertion.

Figure

7 The buccal canine retractor.

Indications:

It is typically indicated in situation where the canine

overlaps the lateral incisor labially.

Advantages:
1- Offers good control on the canine during distal

movement.

2- Prevent unwanted buccal movement.
4- It generally displaces the appliance less than palatal

spring does.

5- Well accepted by adults because it is unnecessary to

use clasping or labial bow on the anterior teeth.

Disadvantages:
1- Because of the heavy gauge of the wire, excessive

force can be easily exerted on the canine during
retraction.

2- It can cause trauma to the vestibular tissues.

Step by step construction procedure:

1- Sketch the design on the cast according to the

description.

2- Cut about 8cm of 0.7mm stainless steel wire and

straighten it.

3- Place the wire on the buccal surface of the canine

and horizontally at a mid-point of the crown
(occluso-gingivally) and construct a rounded curve

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

that extends mesially adapted to the tooth surface
ending at the farthest point that could be reached on
the mesial surface of the canine.

4- On the point at the buccal midline of the crown

(mesio-distally)  mark  a  point  where  a  (90)  degrees
bend  will  be  placed  to  redirect  the  wire  apically.
This  will  form  the  (L)  shape  feature  of  the  active
arm.  The  active  arm  will  extend  up  to  the  vestibule
along the tooth long access.

5- With a permanent marker, put a mark on the wire at

the position about 2 mm shorter to the sulcus depth.

6- Hold the wire 2 mm shorter that the mark point and

start to make a loop of about 3-5 mm in diameter,
note that the active arm should always be under the
coil.

7- Complete the turn of the coil so that the remaining

wire is directed back downward.

8- Now put the wire in position and adjust the

remaining wire to point to the embrasure between
the first and the second premolar while the active
arm still fitted on the mesial border of the canine.

9- Mark the point at the interdental space near the

gingival margin on the remaining wire piece where a
light bend is made to direct the wire piece vertically
at the mesial occlusal margin of the second
premolar.

10-

Mark the wire at the occlusal level. Hold the

wire from the marked point and make a sharp bend
palatally.

11-

Now put the wire in position again and mark

the palatal occlusal margin of the premolar where
another bend is to be made to adapt the wire on the
palatal surface

12-

While the wire passes on the palate, a zigzag or

a  hook  form  is  made  for  retention.  This  retention
form  is  very  important  since the  spring  in  its  action
tends  to  rotate  in  the  acrylic  which  might  cause
loosening of the spring attachment and loss of.

13-

Cut the remaining wire and put the spring in

position then start to adapt the spring so that it will
be about 1mm away from the buccal and palatal soft
tissue.

14-

Now check for the fallowing points while the

spring in position:
a) The coil is 2mm away from the vestibule
b) The spring is 1mm away from the soft tissue.
c) If the first premolar already extracted, make sure

that the wire passes mesial to the second premolar
and with the occlusal level to avoid interference
with the retracted canine.

d) Check if there is interference with the opposite

arch in occlusion.

Activation:
Activation of the canine retractor is made by closing

the coil so that the active arm move about 3mm
posteriorly.

Lab:8. The Modified Buccal Canine

Retractor

Many modifications have been made on the buccal

canine retractor to enhance the control over the retracted
canine. One important modification to the canine
retractor is that made to the end of the active arm in order
to increase the control during retraction, facilitate light
extrusion force and to enable the palatal movement of the
canine at the end of the retraction using the same spring.

Description:

Generally, the spring has the same form and shape

of  the  buccal  canine  retractor  also  the  active  arm  is
situated at the middle of the crown (mesio-distally). The
head  (the  end  of  the  active  arm)  which  is  modified  to
have an extension mesially and distally, which is adapted
on the labial surface of the canine and curved to partially
cover  the  mesial  surface  and  extended  to  engage  the
distal surface so as to make an excellent control over the
canine (figure 8:A and B).

Figure

8 Modified Buccal Canine Retractor. A:Side view ; B: Anterior view

Indications:

1. Where the canine overlaps the lateral incisor labially.
2. Buccally erupted canine which is situated out of the

dental arch and need to be moved palatally

3. Partially erupted and high positioned canine.

Advantages:

1. Offers an excellent control on the canine during distal

movement.

2. Enables extrusion and palatal movement of the canine

at the end of the treatment with out the need for
modification that might cause corruption of the spring.

3. It generally displaces the appliance less than palatal

spring does.

4. Well accepted by adults because it is quite unnecessary

to use clasping and labial bow on the anterior teeth

Disadvantages:

1- Because of the heavy gauge of the wire, excessive

force can be easily exerted on the canine during
retraction.

2- It can cause trauma to the vestibular tissues.

Step by step construction procedure:

1- Sketch the design n the cast according to the

description.

2- Cut about 10cm of 0.7mm stainless steel wire and

straighten it

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

3- put the wire on the labial surface of the canine so that

the tip of the wire fit at the distal border of the canine
just under the distal contact point and put a mark about
2mm anterior to the mesial border of the canines.

4- Hold the wire at the mark point and form a loop which

leaves  the  remaining  wire  pointing  distally.  Now  hold
the wire from the bottom of the U shape loop and bend
it to a right angle to make a small ledge that will adapt
to and catch the mesial surface of the canine when the
spring  is  in  position.  The  horizontal  part  at  the  end  of
the wire must also be adapted on the labial surface.

5- Put the wire in position and mark the point at the

centre of the crown where a sharp bend is to be made
upward to the vestibule parallel to the long axes of the
tooth.

5- With a permanent marker, put a mark on the wire at

the position about 2 mm shorter to the sulcus depth.

6- Hold the wire 2 mm shorter that the mark point and

start to make a loop of about 3-5 mm in diameter, note
that the active arm should always be under the coil.

7- Complete the turn of the coil so that the remaining

wire is directed back downward.

8- Now put the wire in position and adjust the remaining

wire to point to the embrasure between the first and
the second premolar while the active arm is still fitted
on the mesial border of the canine.

9- Mark the point at the interdental space near the

gingival margin on the remaining wire piece where a
light bend is made to direct the wire piece vertically at
the mesial occlusal margin of the second premolar.

10- Mark the wire at the occlusal surface. Hold the wire

from the marked point and make a sharp bend
palatally.

11- Re-position the wire and mark the palatal occlusal

margin of the premolar where another bend is to be
made to adapt the wire on the palatal surface

12- While the wire passes on the palate, a zigzag or a

hook form is made for retention. This retention form is
very  important  since  the  spring  in  its  action  tends  to
rotate  in  the  acrylic  which  might  cause  loosening  of
the  spring  attachment  and  loss  of  action  if  it  is  not
properly made.

13- Cut the remaining wire and put the spring in position

then start to adapt the spring so that it will be about
1mm away from the buccal and palatal soft tissue.

14- Now check for the fallowing points while the spring

in position:

  a- The coil is 2mm away from the vestibule.
  b- The spring is 1mm away from the soft tissue.
  c-  If  the  first  premolar  already extracted,  check  if  the

wire passes mesial to the second premolar with the
occlusal level to avoid interference with the retracted
canine
d- Check if there is interference with the opposite arch

in occlusion.

Activation:
Activation of the canine retractor is made by closing

the coil so that the active arm moved about 3mm
posteriorly.

Lab:9.

Adam's Clasp .

Also named as the arrowhead clasp. It was designed

By  Adam's  in  1970  and  since  then  it  is  the  most
commonly used clasp to provide retention for removable
appliances.  The  clasp  is  constructed  in  0.7mm  wire  and
most  commonly  used  on  permanent  first  molars  but  can
be used for almost any tooth.
A  partially  erupted  molar  which  has  less  than  4  mm  of
crown  generally  gives  poor  retention.  However,  Adam's
clasp  needs  only  0.25mm  of  undercut  to  provide  an
acceptable  retention  which  is  usually  available  at  the
mesio-buccal and the disto-buccal undercuts. In case the
crown  was  not  fully  erupted,  the  clasp's  arrowhead  will
push the gingival margin aside and engage the undercuts
when  inserted  in  patient's  mouth;  a  gentle  trimming  of
the gingival line on the cast model is feasible. When the
molar is not available for retention, Adam's clasp can be
modified  to  involve  two  adjacent  premolars  or  two
centrals; In this case 0.6mm wire is preferred.

Components:

1- The active parts

a. The arrow heads: Two small U shape loops act as

two fingers engaging the mesial and distal
undercuts.

b. The bridge: A horizontal piece of wire joining the

two arrow heads and about 2-3mm away form the
buccal tooth surface making roughly 45 degree
angle with the long axes of the crown.

c. The tags: The extension of the arrow heads on each

side which crosses the occlusal surface to the
lingual side.

2- The retentive part

Extends  from  the  ends  of  the  tags  down  to  the
gingival margin and continue on both sides passing
about 10 mm  along the palatal or lingual soft tissue
(  must  be  1mm  away  from  the  surface).  This  ends
by a small hook shape loops to increase retention of
the clasp.

Advantages:

1- A relatively shallow undercut is sufficient for

providing an acceptable retention.

2- The bridge of Adam's clasp provides an excellent grip

used for insertion and removal of the appliance.

3- Auxiliary springs, hooks and tubes for extra oral

extensions could be soldered to the bridge.

The design has no sharp edges that may injure the soft
tissues

5- The original design can be modified to suit anterior

teeth.

Disadvantages:

1- The labially inclined anterior teeth make it difficult

for the arrow heads to engage the undercut at the
labial surface.

2- The point where hooks or tubes are soldered on the

bridge will be weakened and fracture is common at
that point.

3- Adam’s clasp needs pair of undercuts (at the

mesiobuccal and distobuccal embrasures of the tooth),
if one of them is occupied by a spring, it will be

difficult to incorporate two wires at the same
embrasure.

4- Crossing the occlusal surface at two places increases

the chance for occlusal interference.

Indications:

1- Most common for retention of removable

appliance.

2- Shallow undercuts.
3- Partially erupted molars.
4- Premolars and anterior teeth (after modification).

Step by step construction of Adam's clasp:

1- Sketch the design on the permanent molar. Starting

buccally  by  a  descending  vertical    lines  from  the
tips of the mesiobuccal and distobuccal cusps down
to  the  gingival  margin  then  join  the  two  lines  by  a
transverse line  at the junction between the gingival
and middle third of the crown. The drawing is now
is similar to the  English letter ( H ) (figure: 9 )

2- If the tooth is partially erupted, carve a small piece

of the gingival margin about 1-2 mm at the mesial
and distal corners of the crown just behind the lines
sketched on the crown.

3- Now cut about 10cm of 0.7 mm wire and straighten

it.

4- Hold the wire by hands and adapt it on the

horizontal line of the (H) shape figure on the crown
and keep the tooth at the centre of the wire piece,

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

mark two points on the wire at the positions of the
vertical lines.

5- Start wire bending by making a 90 degree bend at

both  points  resulting  into  an  angled  U  shape.  The
small  wire  span  between  the  two  bends  will  be  the
bridge.

6- Mark the wire at 2mm away from the first bend on

both  side,  hold  the  wire  with  the  pliers  from  the
marked  point  and  make  a  small    U  shape  loop
(around  1mm  internal  diameter)  at  the  tip  of  the
round  beak  of  the  pliers.  This  will  result  in  a  two
small  U  shape  loops  each  of  them  heading  away
from the other, those are the clasp’s arrowhead.

7- Using the pliers hold the U shape loop on each side

and twist it to be at 45 degree angle to the bridge in
the horizontal plane and adapt it on the under cuts
of the molar, make any necessary adjustments so
that the arrowheads fits onto the undercuts.

8- From each side, and roughly at the same level of the

bridge  hold  the  wire  with  the  pliers  and  make  a
sharp  bent 70-90 degrees  toward the tooth  contacts
(Sandhya  2008).  This  will  push  the  bridge  away
from the malar crown. Then another bent bend must
be made at about 2mm away from the first bend that
will  direct  the  wire  toward  the  occlusal  surface.
NOTE  that  these  two  bends  could  be  combined  in
one bend based on tooth anatomy and position.

9- Now fit the wire in position and check the

extensions of the wire on the occlusal surface, make
the necessary adjustment to adapt the two wire
pieces at the embrasure interdentally.

10-

While the clasp is in position, mark the wire at

the lingual margins of the crown and make a sharp

bend  down  gingivally.  Let  the  wire  extend  about
10mm  on  the  gingival  surface  then  a  small  hook
shape  bend  may  be  made for  retention  of  the  clasp
in the acrylic.

11-

Now fit the upper and lower arches together in

occlusion and check for occlusal interference, any
error must be corrected.

12-

For the finished Adam's clasp the following

points must be checked

a. The arrowheads engage the undercuts
b. The bridge is about 2 mm away from the tooth

surface

c. No occlusal interference with the opposite arch

Tube soldered to
the bridge

Adam's

clasp

arrowh

eads

The

bridge

Adam's clasp on

premolar

Adam's clasp on

centrals

Figure

9 Adam’s Clasp

Lab:10.

The Labial Arch

Since it was first designed by Charles Hawley in the

1920s the labial arch has been widely used in
construction of removable appliances for both active and
passive purposes despite its relatively deficient aesthetic
appearance.

Description:

Howley labial arch is constructed with 0.7mm wire

gauge  and  that  rigid  wire  give  it  the  chance  to  share  in
retentive  and  active  treatment  and  resist  distortion  that
might  be  resulted  from  the  relatively  long  and
complicated design

The basic design is composed of a horizontal wire

piece extended on the labial surface of the four incisors,
joined by vertical loops from both sides and extended to
about  3mm  short  than  the  labial  vestibular  depth,  then
crossed  the  occlusal  surface  distal  to  the  canine  and
extended  on  the  palatal  soft  tissue,  ended  by  hooks  for
retention.

Indications:

1- As an active component

a. Retraction of the anterior segment (four incisors)

and treatment of minor anterior irregularities.

b. Share with the Z and Double Z springs to produce

couple forces for correction of simple anterior teeth
rotations.

2. As passive component

a. Stabilization of the corrected malocclusions when

used as a retainer after active orthodontic treatment.

b. Provide anterior retention and stability of the

removable appliance.

c. Act as a splint for the anterior segment to increase

the anchorage of the removable appliance during
active treatment.

Advantages:

1. It is useful to produce force on single or group of teeth

and at the same time give retention of the appliance.

2. The same appliance used to correct malalignment of

teeth will continue to retain their corrected positions.

Disadvantages:

1. It has relatively poor aesthetic appearance as it appears

on the labial surface of the incisors makes it
unacceptable by some patients.

2. Skill is required for adaptation of the bow and in the

same time to prevent the wire from traumatizing the
soft tissues.

3. Care must be taken during activation of the labial arch

as a small activation might produce a very large force.

4. Subjected to distortion when it mistakenly used by

patient to insert and dislodge the appliance.

Step By Step construction:

Sketch the design on the cast as shown in (figure:10).

Take about 15 cm of 0.7mm wire. DO NOT straighten
it as the curve of the wire is useful to produce a
uniform anterior bow.

Put  the  wire  on  the  labial  surface  of  the  anterior
segment so that the centre of the wire piece fits against
the  midline  between  the  central  incisors  and
horizontally  at  the  junction  between  the  middle  and
gingival third of the crown.

Mark two points one on each side of the anterior
segment at the distal border of the lateral incisor.

Using the pliers, hold the wire from one of the marked
points and make a sharp 90 degree angle bend, repeat
the procedure for both points so that the curved arch
form span between the two bends fits to the dental ach
while the wire pieces from both sides head toward the
vestibule.

Now  re  adapt  the  wire  in  position  and  put  a  mark  at
both sides bout 7mm shorter than the vestibule depth,
this  will  leave  roughly  3mm  of  vestibular  clearance
after  forming  the  loops.  Grab  the  wire  from  the
marked point and start to form a U shape loop directed
away from the bow, the diameter of the U shape loops
must be no less than 5mm.

Put  the  wire  in  position.  Make  any  necessary
adjustments  to  maintain  the  U  shape  loops  in  the
buccal  vestibule  vertically  and  horizontally  so  as  to
have 1-2mm clearance from the soft tissue.

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

After that, mark the wire at the embrasure between the
canine and the first premolar and bend the wire from
that point palatally.

Palatally,  the  wire  pass  about  10mm  ending  with  a
small  hook  to  provide  retention  in  the  acrylic,  make
sure that the wire must be 1-2mm away from the soft
tissue.

Activation:

The flexibility of the labial arch is highly dependent

on the length of the U shape loops, while it is relatively
resilient in the vertical direction; it is very hard in the
horizontal direction, only 1mm activation is quite enough
to produce movement of the four incisors.

Activation of the labial arch during retraction of

anterior teeth is done from the U shape loops by  closing
the  loops  so  that  the  arch  will  move  1mm  palatally,  the
activation  must  not  exceed  that  because  it  will  produce
excessive force on the centrals. Care must be taken not to
distort the bow or traumatize the soft vestibular tissue

Figure

10 Labial Arch , Anterior view

Lab:11.

The Fitted Labial arch

When the anterior teeth are proclined so that neither

the Adam's clasp nor the labial arch was suitable, anterior
retention is provided by a modification that combines
both. This was named fitted labial arch.

The basic design is composed of a horizontal wire

span fitted on labial surface at the junction between the
incisal and middle third of the incisors and extended over
two or four incisors ending from both sides by a small 2-
3mm U shape loops directed gingivally. The wire then
passes from both sides to cross the occlusal surface to the
lingual side ending by a hook-like bends for retention in
the acrylic.

Indications:

1. Proclined anterior teeth.
2. Anterior retention is required where labial arch is

not suitable. An example for that is the use of
unilateral canine retractor.

Advantages:

1. Simple in construction and adaptation.
2. Provide good retention of the appliance anteriorly

Disadvantages:

1. Poor aesthetic as it approaches the incisal margin.
2. May interfere with the opposite arch during

occlusion.

Step by step construction:

1. Sketch the design on the cast according to the

description above.

2. Make the necessary wire bending to adapt the wire

horizontally  on  the  labial  surface  so  that  it  will
fallow  the  curvature  of  the  incisors  and  mark  it
about  4mm  short  to  the  distal  end  of  the  incisors
from both sides.

3. Now hold the wire from the marked point and make

a sharp 90 degree angle bend, repeat the bend for
the other side.

4. Hold the wire with the pliers beaks near the first

bend and start forming a U shape loop and repeat
the procedure for the other side. The diameter of the
loops should be about 2-3mm so that the resulted
wire will fit to the dimensions of the involved teeth.

5. Re position the wire and make any necessary

adjustment  so  that  the  wire  fits  against  the  labial
surface of the incisors, place marks on the wire from
both sides at the incisal margin where a sharp bend
will  turn  the  wire  direction  down  to  the  palatal  or
lingual surface.

The wire from both sides must be extended about
one cm on the palatal soft tissue ending by retentive
hooks

Activation or tightening of the wire:

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

The fitted labial arch provide retention through the

horizontal  bow  which  is  fitted  exactly  on  the  labial
surface  of the incisors, tightening  of the bow is  made
through  the  adjustment  of  the  U  shape  loops  that
makes the bow tighter on the labial surface.

A:
Occlusal view of the fitted
labial wire, note the closely
fitted addaptation of the
wire on the labial surface of
the incisos.

B:
Short Fitted labial wire
involves the two central
incisors only.

C 3:
Long fitted wire involves
the four incisors

Figure

11 Fitted labial arch

Lab: 12. Robert's retractor .

This is a flexible bow constructed with 0.5 mm

stainless  steel  wire.  It  is  composed  of  a  bow  which
extended  on  the  labial  surface  of  the  four  incisors.  The
bow  takes  the  shape  of  an  ideal  arch  form  despite  the
irregularities of the anterior teeth as they will be gathered
when retracted. At both ends a sharp bend will direct the
wire gingivally where it will form a 3-5 mm coil not less
than  3mm  shorter  than  the  full  depth  of  the  vestibule.
The  coil  Then  changes  the  redirected  of  the  wire
occlusally  where  it  will  cross  the  occlusal  surface  distal
to the canine and turn onto the palatal surface.

Robert's retractor is highly flexible in all its parts

except at the part from the coil to the acrylic base plate
where it will be shielded by a 0.5mm stainless steel tube
to support the structure of the flexible bow.

In this lab and only for training purpose the full

design  will  be  constructed  with  0.7mm  wire  which  is
believed  to  be  much  easier  in  construction  and
adaptation.

Indications:

1. Retraction of anterior segment
2. correction of spacing or minor irregularities

Advantages:

1. This spring produces a light force and easily

adjustable.

2. Because it swings backward and downward it will

not slide gingivally on the anterior teeth when
retracted.

Disadvantages:

1. If the supporting arms are not correctly positioned

the sulcus may be traumatized

2. In case of breakage major re construction will be

required.

Step by Step construction:

1. Sketch the design on the cast model as shown in

(figure 12).

Take about 15 cm of 0.5mm (0.7mm for training
only). Don’t straighten it as the curve of the wire is
useful to produce a uniform anterior bow.

Place  the  wire  on  the  labial  surface  of  the  anterior
segment  so  that  the  centre  of  the  wire  piece  fit
against the midline between the central incisors and
vertically  at  the  junction  between  the  middle  and
gingival third of the crown.

Adjust  the  wire  by  your  hands  to  make  an  anterior
bow  that  simulate  the  normal  arch  form  of  the
patient.  Despite  the  irregularities  of  the  anterior
teeth, the bow must be a uniform arch.

Mark two points one on each side of the anterior
segment at the distal border of the lateral incisor.

Please note that this section is for training purpose only and the
construction steps are not required in any written or verbal exam.

6. Hold the wire with the pliers from one of the

marked  points  and  make  a  sharp  90  degree  angle
bend,  repeat  the  procedure  for  both  points  so  that
the bow extends horizontally on the labial surface of
the  incisors  while  the  wire  pieces  from  both  sides
head toward the vestibule.

7. Now re adapt the wire in position and place a mark

at both sides bout 7mm shorter than the vestibule
depth, grab the wire from the marked point and start
to form a 3-5mm coil, note that the active arm (near
to the bow) must be under the coil.

8. Re-position the wire and make any necessary

adjustment to maintain the coils in the curvature of
the dental arch vertically and horizontally.

9. Inset the wire from both sides into a stainless steel

tube which will extend from the coil to the acrylic
Base plate in the finished appliance (this step will
not be done with 0.7 wire only for training).

10.

After that, mark the wire (the tube) at the

embrasure between the canine and the first premolar
and bend it from that point Palatally.

11.

On the palate, the wire pass about 10mm ended

with a small hook to provide retention in the acrylic,
make sure that the wire in must be 1-2mm away
from the soft tissue.

Activation:

This

bow is light and flexible. An adjustment of

about 3mm is  suitable but  the site of  adjustment is  very
important  because  if  the  wire  is  activated  at  the  point
where  it  emerges  from  the  supporting  tube  (a  sight  of
stress  concentration)  it  will  often  fracture.  The  bow  is

adjusted  by  bending  in  the  vertical  limb  below  the  coil.
As the incisors retracted  the bow swings downward  and
backwards and the level of the horizontal  part will need
adjustment.

Figure

12 Robert Retractor, Front view

Lab: 13 .

Acrylic base plate .

The acrylic base plate constitutes the body of the

removable appliance. It has thee functions:

1. Act as the foundation into which the retaining clasps

and active components of the appliance are
embedded, such as springs and screws.

2. Contribute to the anchorage during the course of

active tooth movement. This might be achieved
though the close fit of the acrylic to the palatal
surface of the teeth and palate.

It could be extended to form bite planes to
disengage the occlusion or produce overbite
reduction

Design:

The design of the acrylic base plate depend on the

case  to  be  treated,  each  case  may  have  deferent
modifications  according  to  the  components  to  be
incorporated into the design. But there are general points
that  must  be  considered  during  the  construction  of  the
acrylic base plate:

1. Several types of acrylic materials could be used for

construction  of  the  base  plate,  but  chemical  cured
acrylic  resin  is  commonly  used  since  it  is  economic
and less labor intensive.

2. The base plate needs to be thick enough to carry the

retentive  and  the  active  components,  but  should  be  as
thin  as  possible  to  avoid  discomfort  to  the  patient,
ideally,  this  should  be  as  thick  as  a  sheet  of  modeling
wax (2-3)mm.

3. The base plate should normally cover most of the hard

palate, finishing just distal to the first molars.

4. It should fit closely to the palate and around the teeth

that are not to be moved, extends up to one third of the
crown length. Whereas the teeth being moved should
have enough clearance around to move freely.

5. The clasps or springs retentive parts should be

embedded in the acrylic, exposure of the wire may
cause future dislodgement or malfunction of the
springs and clasps.

Modifications to the Acrylic base plate:

The design of the base plate may be modified to

accommodate  springs  as  in  boxing  ,    add  an  active
extensions  as  in  Bite  planes  ,  or  to  accommodate
expansion screws to  the basic design.

1- bite planes

The acrylic may be thickened palatal to upper

incisors to form the anterior bite plane or may be
extended on the occlusal surface of the posterior teeth
to form a posterior bite plane.

a- Anterior bite plane

The principal use of the anterior bite plane is for the

reduction of the overbite. This occurs primarily by
alteration of the rate of eruption of the posterior teeth
relative to the lower anterior. Several points must be
considered during the construction of the anterior bite
plane:

1. Vertically, the acrylic should be as high as that

when the lower anterior teeth are in contact with the
acrylic bite plane the premolars are separated by 2-
3mm.

2. The posterior limit of the anterior bite plane should

extend just sufficiently to engage the lower incisors.

3. The anterior bite plane should be made with the

occlusal surface parallel to the occlusal plane.
Inclined

bite

planes

may

cause

unwanted

movements. However this may be required in some
cases.

4. Adjustment of the bite plane may be done by

addition of acrylic which may be lost due to
occlusal wear between visits.

5. If the lower incisors are irregular, adjustment of the

bite plane surface is needed to provide contact with
at least 3 lower incisors, then few visits later
leveling of the occlusal plane is possible to lower
anterior level.

b- Posterior bite plane

It is occasionally necessary to extend the base plate to
cover  the  occlusal  surfaces  of  the  posterior  teeth
bilaterally to open the bite and so relief the incisal or
cuspal  lock  while  an  anterior  cross  bite  or  a  bucco-
lingual abnormality is being corrected.
Few  points  must  be  considered  during  the
construction of posterior bite plane:

The posterior bite plane should be thick

enough just to disengage the interlocking of the
anterior teeth and permit correction of cross bite.

The posterior bite plane should extend on the

first molar and premolars and should be faceted to
accommodate the cusps of the opposing teeth.

It must be simultaneously in contact in both

sides, any correction must be made using articulating
paper.

The mandible must be at a centric relation, this

is achieved by putting a piece of modeling wax on the
occlusal surface of the molars and premolars and
instruct the patient to close in centric relation to the
desired height. Then transfer the wax records with the
upper and lower cast to the articulator.

It is important that the (tags) which is the parts

of  the  clasp  that  crosses  the  occlusal  surface  must  be
free from acrylic of the bite plane, presence of acrylic
surrounding  the  wire  may  cause  limitation  of  the
flexibility  of  the  wire.  This  achieved  by  covering  the
wires with wax before applying acrylic.

2 Boxing, Open spring and Wire guard:

  Those  are  three  designs  of  the  acrylic  base  plate
around  the  palatal  springs.  Boxing  (Figure  14)  is  to
make  the active arm  and  the  coil  free  to  move  inside
an  acrylic  chamber  built  into  the  base-plate,  while
open spring  (Figure  13)  is to  completely remove  the
acrylic  of  the  base-plate  from  the  path  of  the
movement  and  leave  the  active  arm  and  the  coil  free
without  protection,  the  guard  wire  (figure  14)    may
be  incorporate  in  the  open  spring  design  to  prevent
distortion of the spring during wearing and activation,
it could be added from the tongue side or occasionally
from  both  sides,  it  may  also  be  used  with  the  boxing
design palatally for the same reason.
Boxing  is  made  by  covering  the  entire  spring  with
wax  except  at  the  retentive  part.  The  wax  must  also
cover  the  area  at  which  future  activations  may  occur
so  that  the  spring  will  move  freely  along  its  range  of
action.  The  acrylic  base  plate  material  should  then
cover  the  palatal  surface  including  the  boxed  spring
with  the  same  thickness  which  will  form  a  bulge  or
elevation at the area of boxing.  Then after the acrylic
is set, a hot water bath will eliminate the wax leaving
the  spring  to  move  in  an  acrylic  chamber  attached
only at its retentive part with the acrylic.

Open  spring  and  guard  wire  are  made  in  the  same
manner  except  that  the  acrylic  will  not  cover  the
boxed  area  but  leave  it  opened  with  out  acrylic  or
crossed  by  a  piece  of  wire  to  protect  the  spring    in
case of guard wire (Figure:13) .

Figure

13 Open spring

Figure

14 Combined Boxing and Wire guard

Lab:14.

Orthodontic Screws

3 Orthodontic Screws

An alternative method of providing orthodontic

force  is  to  use  expansion  screw  as  an  integral  part  of
the  removable  appliance  (Figure  15).    The  screw
normally  transmits  its  force  by  means  of  acrylic,
which comes in contact with the teeth. Many types of
screw are commercially available for use in removable
appliance (one dimension, two dimensions , fan shape,
etc…), the type of the screw is specific for each case
and  have  to  meat  the  requirements  of  an  Adequate
travel, Stability and minimal bulk.

Description:

Screws are produce by a number of manufacturers and
a wide range of sizes and shapes are available.
  Typically,  the  design  has  a  central  threaded  screw,
each  end  of  which  engages  into  a  small  metal  or
plastic  block.  One  of  this  blocks  caries  two  guide
wires which lie parallel to the screw and pass through
holes in the opposing block. The centre of the screw is
enlarged  into  a  small  boss  into  which  four  radially
positioned  holes  are  visible.  A  small  wire  key  is
supplied and activation is made by insertion of the key

Figure

15 Orthodontic Screws. A: 2sides; B: One Side.

into  one  of  these  holes  and  turned  like  a  capstan
through  90  degree  until  it  touches  the  guide.  For
further  activations  the  procedure  must  be  repeated
with the key inserted into the next hole.

Uses:

Screws are recommended only in those few

situations where spring will be unsatisfactory.
Nevertheless, there are certain situations in which
screws are very useful, for example

1. Expansion

It is some times necessary to increase the width

of the upper dental arch or to correct a unilateral cross
bite .Symmetrical widening of the upper arch could be
achieved by removable appliance with suitable design
containing four Adam's clasps on permanent molars
and premolars. In this case the screw should be placed
horizontally on the midline of the palate. In addition
to a shallow posterior bite planes to prevent secondary
lower arch widening (Figure 16).

Figure

16 Orthodontic Screw at the midline used for expansion

2. Distal movement:

Distal movement of molars could be achieved by a

removable  appliance  carrying  bilateral  screws  which
will  deliver  distally  directed  force  to  the  molars.
Careful positioning of the screws will be necessary in
accordance  with  the  three  dimensional  orientations  of
the arch. A version  with  a  screw only one  side  of the
appliance  is  also  useful  in  a  situation  for  example  if
unilateral distalization of molar (Figure 17).

Positioning:

Although  clasps  and  springs  accept  minor
adjustment to correct faulty positioning, screws can
only be corrected by cutting out the screw from the
acrylic  and  re-fabricate  it.  It  is  therefore  very
important  to  accurately  position  the  screw  in  the
three dimensions during construction.

Figure

17 Orthodontic Screw at one side of the arch used

for distal movement.

Disadvantages

1. Most important is the bulky appliance that will

cause discomfort to the patient.

2. over activation may cause difficulties in appliance

incretion and will gradually lose its fitness

3. Full cooperation of the patient is required since

relapse is quick and may elongate treatment time.

Adjustments:

Activation  of  the  screw  is  done  by  inserting  the  key
wire into one of the activation holes and turn the screw
to  the  direction  that  will  open  the  screw  until  the  key
touches  the  guide  bars  (  the  direction  is  usually
marked  by  an  arrow  on  the  screw),  this  will  make
quarter  turn.  Farther  activation  means  to  repeat  the
previous  work.  Activations  are  done  by  the  patient
once or twice a week, each quarter turn will provide a
0.25mm opining that means about 1.5-2mm per month
which  is  considered  a  reasonable  amount  of  tooth
movement.

References:

Sandhya, S.L., 2008. Orthodontic Removable Appliance

2nd ed., Jaypee.

Singh, G., 2007. Textbook of Orthodontics 2nd ed.,

Jaypee.