The scope of fixed appliances

The scope of
fixed appliances
By
Prof. Dr. Maher Fouda

Justification for orthodontic
treatment
 There are two clear justifications for
orthodontic treatment: aesthetics and
function. Orthodontic treatment can
not only improve dental alignment
but, in certain cases, can also have a
profound effect upon the facial
appearance of the individual.

 An unattractive dental or facial
appearance has been shown to
have an adverse effect upon an
individual’s psychological
development. It also can affect the
individual’s acceptance by his or
her peers and even influence
career prospects. There is,
therefore, an increasing demand for
orthodontic treatment.

 There is some evidence that
improved dental alignment can
result in an improved standard of
oral hygiene, but there is little
support for the claim that
orthodontic treatment will lead to
an increased longevity of the
dentition through a reduction in
periodontal disease or caries.

 Certain features of malocclusion, such
as an anterior open bite or Class III
incisor relationship, are associated with
a speech abnormality and correction of
the malocclusion may be justified on
these grounds. There is also evidence
to show that individuals, especially
boys, with prominent upper incisors are
more prone to trauma of the upper
anterior teeth than those with a normal
overjet.

It would appear that adequate
mastication is possible with
most irregularities of the teeth,
although the inability to chew
certain foods may be a major
reason for patients with an
anterior open bite seeking
treatment.

Occasionally a traumatic
relationship of the teeth may
exist whereby the patient’s
dental health may suffer if
orthodontic treatment is not
undertaken, and here there is
a clear justification for
orthodontic treatment.

 The relationship between malocclusion
and the symptoms associated with the
temporomandibular joint (TMJ) and its
related musculature is less clear. While
there is increasing evidence that
orthodontic treatment may be beneficial
rather than detrimental in this respect,
the relationship is unclear and it is not
considered advisable to attempt to
correct a malocclusion with the sole aim
of alleviating or preventing TMJ
symptoms.

 However, if orthodontic treatment is
undertaken, the operator should
aim to produce an intercuspal
position with as many teeth in
contact as possible and an
occlusion free of occlusal
interferences in function. It is a
matter of fundamental importance
for the operator to identify the
potential benefits of treatment.

 Unless there is a clear benefit avail
able to the patient, treatment should
not be commenced. Orthodontic
treatment is not with out risk. Such
problems as enamel decalcification,
root resorption and traumatic facial
injury with headgear are well
documented and must be balanced
against the benefits to be gained
from treatment.

This becomes even more
important when the guarantee
of a stable end result cannot be
given. The risk/benefit analysis
of each individual case should
be discussed fully with the
patient and parents before
embarking on treatment.

Benefits
 The orthodontic treatment that has
been suggested for you may have
overall benefits in the appearance of
your face and teeth and in maintaining
good oral health.
 Well aligned teeth are easier to keep
clean and many patients will find their
self esteem is enhanced by an
attractive smile and dental appearance.

It is important to appreciate that
not all these benefits may be
appropriate to every individual
patient. There is also great
variation in each individual’s
response to treatment and this
can, on occasions, affect the
final result.

Risks
 As with any form of treatment
there are some risks associated
with orthodontic treatment. While
every effort is taken to minimize
these risks, you, the patient, can
help to minimize them by
following treatment advice
carefully and fully.

1. Tooth decay and enamel
damage
 Tooth decay and enamel damage
can occur if sugary or acid foods
are eaten and tooth brushing is not
maintained at a high standard. This
damage can occur at any time but
is more likely when fixed
appliances are attached to the
teeth.

2. Root resorption
 Orthodontic tooth movement involves
light pressure being placed on the teeth
and roots. In some patients changes
such as root shortening may occur. The
causes of this are not well understood
and it is not always possible to identify
susceptible patients in advance. In the
majority of cases where this occurs
there are no significant consequences

3. Headgear
If not worn correctly,
headgear may cause injury.
It is imperative that the
written instructions are
followed when using a
headgear appliance.

4. Joint discomfort
Some individuals may
experience jaw joint discomfort
during orthodontic treatment.
This is usually a transitory phase
and indeed such symptoms also
occur in patients who are not
wearing orthodontic appliances.

5. Post-treatment changes
Throughout life the position of
teeth alters regardless of
orthodontic treatment. Some
aspects of orthodontic
treatment are particularly
prone to post-treatment
changes.

Following fixed appliance
treatment retainers will need
to be worn. There are other
changes, particularly the
degree of crowding of the
lower incisors, that may
progressively alter
throughout life.

6. Medical history
General medical problems
may influence an individual’s
response to orthodontic
treatment. It is important to
inform your orthodontist of any
changes in your medical
health.

Aims of orthodontic treatment
 The goal of orthodontic treatment has been
defined by Proffit (1993) as ‘the creation of
the best possible occlusal relationships,
within the framework of acceptable facial
aesthetics and stability of the end result’.
Indeed, the prime aim of orthodontic
treatment is to produce a dentofacial
appearance that is aesthetically pleasing,
with good function and with the teeth in a
stable position .

 A conflict of interest arises when
an improvement in the alignment
can only be achieved by moving
teeth into an unstable position. A
‘risk/benefit analysis’ must be
made and a treatment plan
formulated which meets the
perceived requirements of both
patient and operator.

Orthodontic treatment should
not be undertaken unless a
significant and lasting
improvement can be offered
and, for this reason, many of
the milder malocclusions are
probably better left untreated.

The aims of orthodontic treatment may be
summarized as follows:
 relief of crowding;
 correction of the rotational and apical
displacement of teeth;
 correction of the interincisal relationship;
 establishment of a satisfactory buccal inter-
cuspation;
 a pleasing facial appearance;
 a stable end result.

Stability
 It must be stated at the outset that it is
simply hopeless merely to move teeth into
good alignment and expect them to remain
there. The factors which determine the
‘stable’ position of the teeth are not certain,
but a good starting point is to regard the
teeth as being in a zone of muscular
balance between the soft tissues, and
movement away from this zone may
increase the risk of an unstable result .

 The collagenous matrix of the periodontal
ligament tends to act as a ‘buffer’ and
moderates small degrees of force
imbalance within this zone of stability.
Further movement from the zone or a
reduction in the health of the periodontal
support may ‘tip the balance’ and result in
instability of tooth position. Certain
environmental factors such as aberrant
soft tissue behaviour, the presence of a
digit- sucking habit, or loss of periodontal
bone support may have an influence on
the position of stability.

 The factors determining the positions of
stability are impossible to identify with
precision and would appear to change
throughout the patient’s life. We consider it
is wrong to believe, and indeed to advise
the patient, that orthodontic treatment will
move the teeth into a new position into
which they will stay forever more. This is
simply not the case. Teeth have been
shown to move throughout life, whether
orthodontic treatment has been
undertaken or not .

 The general tendency with age is for a
reduction in both the arch-length and
arch-width dimensions and for an
increase in crowding. An awareness by
patients of this fact may help an
acceptance of some of the smaller tooth
movements that may occur following the
completion of a course of orthodontic
treatment.
 Certain tooth movements are associated
with a greater risk of relapse.

Labial segments
 A major consideration in the stability
of orthodontic treatment is the
labiolingual position of the lower
incisor crowns. There are certain
situations in which alteration of the
lower incisor position is desirable and
a stable result may be achieved, but
considerable experience is required
to recognize and treat these cases.

The authors (Williams et al.,
1995) advise that during
treatment the pre-existing
labiolingual position of the
lower incisor crowns is
maintained, and that alignment
of the lower labial segment is
achieved by the adequate
relief of crowding .

Movement of the teeth in the
labial segment out of the zone
of soft tissue balance is
unlikely to be stable and,
following removal of
appliances, crowding is likely
to recur in the lower arch as
the incisors return to their
initial axial inclination.

 This may result in a relapse of a
previously reduced overjet and
overbite, or secondary upper arch
crowding may occur as both upper and
lower labial segments move palatally,
so reducing arch length. Alignment of
the lower incisors must therefore be
achieved by the appropriate
extractions to relieve crowding and the
distal movement of the lower canines.

Interincisal angulation
 The interincisal angulation in a
Class I incisor relationship is
normally between 130° and 135°. It
may not always be possible, or
indeed desirable, to achieve this
angulation, yet the larger the
interincisal angulation, the greater
is the chance of an increased
overbite becoming established.

In extreme cases, where
overjet reduction has been
carried out by an inappropriate
degree of retroclination of the
upper incisors, a potentially
traumatic overbite can
develop.

An increased overjet reduced by excessive incisor
tipping may result in a traumatic overbite

Buccal intercuspation
 It is also desirable at the end of
treatment to have a good buccal
intercuspation. If the cusps of the
premolars and molars are not
satisfactorily interdigitating at the
completion of treatment, then occlusal
forces may predispose to movement of
the teeth in either arch. This can lead
to the relapse of an increased overjet
or the development of crowding .

 Treatment plans which involve symmetrical
extractions in both arches will normally
necessitate a Class I buccal segment
relationship at the end of treatment. In some
Class II division 1 malocclusions with
uncrowded lower arches, it is possible to
limit the extractions to upper premolars only,
in which case the molar relationship will be
Class II at the end of treatment. Provided
there is a good intercuspation, a Class II
molar relationship is acceptable as a
treatment goal.

Soft tissues
 The position of the teeth is related to the
morphology and action of the soft tissues.
Certain abnormalities of tongue or lip
behaviour are liable to cause relapse of a
treated mal occlusion. Many Class II division 1
cases have an adaptive tongue thrust, which is
secondary to the increased overjet. Once the
overjet has been corrected the tongue thrust
ceases. There are a few individuals who exhibit
a so-called ‘endogenous’ or ‘primary tongue
thrust’ which will persist after treatment .

 Such tongue thrusts are frequently
associated with an anterior open bite
extending into the buccal segments and
an anterior sigmatism. The practitioner
should be able to recognize these and be
aware of the doubtful prognosis for
treatment.
 A persistent digit-sucking habit will also
affect tooth position, often producing an
anterior open bite, an increased overjet
and a posterior crossbite.

The aim of treatment,
particularly in Class II division 1
malocclusion, is to alter the
position of the upper incisors
relative to the lower lip and to
move them from a position of
stability outside the lower lip
into a new position of stability
inside the lower lip.

 This is achieved when the lower
lip rests in front of the upper
incisors and covers at least a third
of their labial surface. It is also
important to ensure that the
overjet is adequately reduced, so
that the lower lip cannot become
‘trapped’ behind the upper
incisors and cause relapse .

A treatment plan that aims for
partial reduction of the overjet
is in danger of producing an
unstable result. A small
number of patients exhibit a
particularly tight lower lip, the
excessive action of which is
often seen during talking or
smiling.

This has become known as an
‘expressive’ or ‘strap-like’ lower
lip. The treatment of patients
with this type of lip pattern
associated with a Class II
division I occlusion is quite
likely to relapse if overjet
reduction is attempted .

Tooth movement with fixed
appliances
The movements that are to
be considered are tipping,
uprighting and torqueing,
bodily movement and
rotation.

Tipping
Tipping is the easiest form of
tooth movement to achieve
and is produced by the
application of a single force to
the crown of tooth. The tooth
moves under the influence of
the force in the direction of
least resistance.

It is important to note that the
tooth does not tip about the
apex but rather about a
fulcrum which is established
within the root of the tooth. The
crown moves in the direction
of the applied force and the
root apex moves in the
opposite direction.

Tooth tipping by applying a single force to the
crown of a tooth

 Many malocclusions cannot be
satisfactorily treated by means of
simply tipping teeth. Fixed
appliances are capable of
producing tipping movements, but
by applying a force couple to the
crown of the tooth it is also
possible to achieve control of the
apical position.

Uprighting and torqueing
 If a force is applied to a tooth, it will move
by tipping, unless it is prevented from
doing so. When either uprighting or
torqueing forces are applied to a tooth,
tipping is prevented and some degree of
controlled movement of the apex occurs.
We define uprighting as the intentional-
mesial or distal movement of apices and
torqueing as the labial or lingual
movement of the root apices .

 Both uprighting and torqueing require
the application of a force couple to the
crown of the tooth in such a way that
the fulcrum lies within the crown. It is
here that the management of tooth
movement becomes more difficult
because these movements aim to
control the apex of the tooth by
applying a force to the crown of the
tooth, some distance away.

Bodily movement
 Bodily movement of the teeth
implies an equal movement of the
crown and apex in the same
direction. It is not possible to
move a tooth bodily by the
application of a force to the crown
of the tooth unless the tooth is
prevented from tipping.

 Although difficult, this type of tooth
movement can be achieved using a
fixed appliance designed in such a way
that a force couple is applied to the
crown of the tooth so that the apex
moves in the same direction as the
crown. Pure bodily movement is
relatively easy to visualize but in reality
rarely occurs. In clinical practice there is
almost always a degree of tooth tipping
and usually a separate stage of apical
positioning is required.

Rotation
 Rotation of teeth around their long
axis again requires the application of
a force couple to the crown. There is
considerable mechanical difficulty in
applying an efficient force couple with
a removable appliance. However, with
a fixed attachment on the tooth to be
rotated, precise rotational control can
be obtained, especially if a wide
bracket is used.

A further advantage of using
fixed appliances for rotational
correction is that any
abnormality of apical position,
so frequently associated with
rotated teeth, can be corrected
simultaneously.

A force couple is created when the archwire is
engaged in the bracket of a rotated tooth

Specific indications for the use of
fixed appliances
Grossly misplaced teeth
 When the crown or apex of a tooth is markedly
displaced from the arch, particularly when
movement in an occlusal direction is required,
fixed appliances are essential. In such
instances the crown of the tooth will be
inaccessible to a removable appliance spring.
If an attachment is placed on the displaced
tooth, a site is thereby provided for the
application of an appropriate force.

Brackets bonded to palatally placed canines, allowing the
application of orthodontic forces to the teeth

Lower arch treatment
 Removable appliances are rarely
used to move teeth in the lower
arch. They tend to be bulky, have
poor retention and the springs are
often inefficient. Fixed appliances
offer a much more efficient means
of moving lower teeth.

Alignment of a lower labial segment with a fixed
appliance, following extraction of a displaced incisor

Space closure
 When a fixed appliance is used, apical as
well as coronal correction can be
achieved. Such space closure is advisable
for the treatment of mal occlusions where
extractions provide more space than is
required for the relief of crowding, or
where teeth are congenitally absent.
Space closure is best undertaken in this
manner so that the roots of the teeth are
parallel at the end of treatment.

Incisor relationship
 In a Class II division 1 malocclusion
the reduction of overjet is often
required. Tipping the incisors
palatally may often be acceptable
but where there is an antero-
posterior skeletal discrepancy,
palatal movement of the upper
incisor apices is usually required.

Fixed appliances, by virtue of
the fact that they have some
control over apical movement,
can be used to reduce an
overjet without excessive
tipping, thereby producing a
satisfactory incisor relationship.

Overjet reduction. Fixed appliances have been
used to retract the incisors bodily

 Many Class II division 2 incisor
relationships and bimaxillary
incisor proclination can only be
corrected using fixed appliances,
because of the necessity of
altering the apical position of both
upper and lower incisors in order
to achieve a stable change in the
interincisal angle.

Multiple tooth movement
 Fixed appliances allow for control of
the position of several teeth or
groups of teeth in both arches.
Simultaneous tipping, rotation and
apical movements are possible and
intramaxillary, inter- maxillary and
extra-oral forces can be effectively
applied.

 You are now wearing a fixed
appliance. You must take great
care of it.
 You must:
1. Clean your teeth with a brush,
immediately after every meal and
before going to bed. If your teeth
are not kept clean damage will
occur.
Patient’s instructions

2. Avoid eating hard foods (such
as crusty bread), and sticky
food, (such as toffee and
nougat).
3. Since it will be necessary to
use a toothbrush after eating,
most patients find it best to
avoid snacks taken between
main meals.

4. Contact the orthodontist if the appliance
hurts, becomes loose, or if any part
however small is broken.
5. Continue with your routine dental visits.
 Initially there will be some difficulty in
eating and speaking but this will soon
pass.
 You may experience some discomfort for
a few hours following the placement of
new archwires. This may be eased with a
mild analgesic.

Instructions for patients wearing
Headgear
 You have been given headgear. You
must take great care of it.
 Extreme care should be used at all times
when it is worn. You must:
1. wear it for an average of hours a day;
2. wear it exactly as instructed, including
any safety mechanism; failure to do so
may cause damage;

3. ensure no one touches the
headgear when it is being
worn; if the bow is pulled
forward out of the attachment
it may spring back causing
facial damage;
4. keep a record of the hours
worn on the sheet provided;

5. bring your headgear and record of
wear at each visit; the appliance will
need to be adjusted and checked;
6. contact the orthodontist if the
appliance hurts, becomes loose, or if
any part however small is damaged;
7. stop wearing the headgear, and
contact the orthodontist if the bow
comes out at night.

You must not
1. wear the headgear if any part
becomes loose, broken or
uncomfortable;
2. wear the headgear during sports
or other activities where you may
be in close contact with other
people.

Instructions for patients wearing
elastic bands
 You now need to wear small elastic
bands to help tooth movement.
 You must
1. wear the elastics exactly as you have
been shown;
2. carry a supply of elastic bands in
order that any broken ones can be
replaced immediately;

3. replace the elastics with new
ones every day;
4. contact the surgery if you run
out of elastics.
Remember that failure to
follow these instructions will
prolong your orthodontic
treatment.

Mandibular advancement using
distraction
A dry mandible showing the ‘conticotomy’ cut indicated with red wax.
The Medicon intra-oral distractor is placed parallel to the occlusal
plane. The screw is accessed from the mesial aspect of the assembly.

(A) (B)
Mandibular advancement using distraction

(C)

(D)

Patient JS (A) Extra-oral lateral pre- and post-treatment views. (B) Extra oral
facial pre- and post treatment views. (C) Intra-oral pre-treatment views. (D)
Intra-oral post-treatment views. (E) 1 year into retention.
(E)

Patient MB. (A) Extra-oral lateral pre- and post-treatment views (B) Extra-oral
facial pre- and post-treatment views. (C) Intra-oral pre-treatment views. (D)
Intra-oral views during distraction. (E) Intra-oral post-treatment views. (F)
Smiling with distractors in place.
(F)

Patient SH. (A) Extra-oral lateral pre- and post-treatment views. (B) Extra-
oral facial pre- and post-treatment views. (C) Intra-oral pre-treatment views.
(D) Intra-oral post-treatment views.
(D)

Burton approach for indirect bonding

Functional & fixed appliances
Occlusal blocks with buccal tube attachments.
Block inserted into buccal to be ready to be rotated to seat lingual inserts

Occlusal blocks with lingual tube
attachments.
Seated occlusal block.
Occlusal blocks with palatal tube
attachments.

Fixed functional appliance in place.

Pretreatment

In-treatment records

Post treatment

Treatment goal.
Interdisciplinary

(a-c) Upper incisors retracted and intruded by two cantilevers with a curved
configuration as described by Dalstra and Meken (1999). (d-e) Simultancously buccal
segment teeth approximation with Sentalloy springs in the palate, the force system
generated is indicated on the drawing.
Interdisciplinary

(a-c) Second phase of treatment during which the lower incisors were
translated labially by intrusion and buccal torque generated by a
0.017x0.25 inch arch. The horizontal force component was delivered by a
0.020 continuous arch above the incisal brackets and light Sentalloy
springs between the premolars and the anterior segment.
Interdisciplinary

(a) Final stage of treatment where all four incisors are being
intruded and retracted. (b) finishing of the lower arch.
Interdisciplinary

Treatment analysis. This is a good result when compared to the original
treatment goal.
Interdisciplinary

(a-c) Extra-oral view following treatment. Harmonious facial expression
with muscle balance. (d-h) Intra-oral view following treatment. A neutral
occlusion was established. In the right side a bonded bridge was inserted
and the patient is waiting for an implant.
Interdisciplinary

The scope of fixed appliances

More Related Content

What's hot (20)

Similar to The scope of fixed appliances (20)

Recently uploaded (20)

The scope of fixed appliances