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SWAMI DEVI DAYAL DENTAL COLLEGE AND HOSPITAL
BARWALA,PANCHKULA.
DEPARTMENT OF ORTHODONTICS AND DENTOFACIAL
ORTHOPAEDICS
SEMINAR
ON
LABIAL BOWS
SUBMITTED BY:-
GURINDER SINGH
MDS 1ST YEAR
LABIAL BOWSBows may be active or passive and will span a number
of teeth.Both ends of bow are incorporated in acrylic
plate.These are components that are used for both
overjet reduction and for providing anterior fixation.
Indications
bows are capable of:
1.Overjet reduction
2.Active bows for incisor retraction
3.Elimination of minor incisor interference
4.retention
5.Flexible bows such as Roberts are suitable for
large overjet reduction
6. Minor derotations of incisor teeth
Parts of labial bow
1 .horizontal part
2.vertical loop
3 retentive arms
LABIAL BOW FABRICATIONThe Labial Bow fabricated in 0.8mm S.S wire.
The upper model.
A light pencil line is marked on the upper model as a guide to show the position of the Labial Bow and 'U' loops. N.B. The Labial Bow should be mid crown height and level with the occlusal plane.
The following 'spacer technique is not commonly used by experienced dental technicians.A light (1mm) wax spacer may be placed in the 'U' loop area
to create an instant space between the gingival soft tissues / model and the 0.8mm S.S wire. (When forming the 'U' loop, the in 0.8mm S.S wire must contact the wax spacer. Failure to ensure this will result in a greater space between wire and soft tissues, which is undesirable).
A suitable length of 0.8mm S.S wire is cut and an 'ideal arch' is formed using the fingers and thumbs.
The Labial Bow arch is checked on the model and should rest against each anterior tooth passively.
A pencil mark is placed on the 0.8mm S.S wire at the point of the canine eminence, usually at the mid point of the canine and a 90 degree bend is formed.
The 'U' loop is then formed using 'flat round' pliers / 'spring former' pliers. N.B. The length of the 'U' loop should curve just beyond the gingival margin as shown in the image.
As mentioned above, a 1mm space between soft tissues and the 0.8mm S.S wire is ensured for patient comfort. The distal tag wire of the 'U' loop / Labial Box is then formed over the interstitial area of the teeth.
The finished Labial Bow: -
* Contacting all anterior teeth passively and tag arms ending at approximately two thirds into the palate.* 1mm spacing between 'U' loop / tag arm and soft tissues.* The 'U' loop should curve just beyond the gingival margin.* Labial Bow at mid crown height and level with the occlusal plane.
Ref: - Isaacson, Muir, Reed - Removable Orthodontic Appliances 2002. ISBN 0723610533.
A wide variety of labial bows are available for use in
orthodontics. They are as follows:
1. Short Labial Bow
2. LONG LABIAL BOW
3. Split Labial Bow
4. Robert's Retractor
5. Reverse Labial Bow
6. Mill's Retractor
7. High Labial Bow with
Apron Springs
8. Fitted Labial Bow
Short Labial BowThe short labial bows are made from 0.7 mm round SS
wire. The labial bow is constructed in such a way that
can also bring about minor overjet reduction and
anterior space closure. Their range of action is limited
because of stiffness and low flexibility. For space
closure, the bow is activated by compressing the loops
of the bow by 1-2 mm.
LONG LABIAL BOW
It is a modification of the short labial bow design, in
that it extends from the first premolar of one side to
that of the contralateral side. The distal arm of the U-
loop extends between the two premolars and ends as
the retentive arm. It can be used as an active and
retentive component of the removable appliance. It is
indicated in minor overjet reduction, small amounts of
anterior space closure, closure of space distal to canine
and also for guidance of canine during canine
retraction. It is also activated by compressing the loop
1-2mm so that the bow is displaced palatally by 1 mm.
Modification Labial bow soldered to Adams' clasp. In
extraction cases following orthodontic treatment,
closed spaces can be retained with a Hawley's retainer
in which a long labial bow is soldered to the bridge of
the Adams' clasp. A short labial bow is not feasible in
such cases as the distal arm can cause opening of the
extraction space between canine and premolar.
Split Labial Bow
This is a modification of the conventional short labial
bow in that it is split in the middle. This is done to
increase the flexibility of the otherwise stiff short
labial bow. The bow is made up of 0.7 mm round SS
wire and has 2 separate short buccal arms, each with a
V-loop ending distal to canine. This labial bow is
effective in anterior retraction. It has also found use in
closure of midline diastema, for which it has been
modified such that the 2 buccal arms extend across the
opposite centra1incisor and engage onto its distal
surface. Activation is done by compressing the 'V' loop
by 1-2 mm.
Robert's Retractor
This labial bow is made of 0.5 mm round SS wire,
which is of a much thinner gauge than the
conventional labial bows. It extends over the labial
surfaces from canine to canine and instead of a regular
loop it incorporates a 3mm internal diameter helix at
the base of the loop. The combination of a thin gauge
wire and a helix makes this labial bow highly flexible
and susceptible to distortion as it lacks stability in the
vertical plane. To overcome this, the distal arms of the
loops are supported in softened stainless steel tubes of
0.5 mm internal diameter.
Along with Adams' clasp on the buccal teeth for
retention, this retractor can be used in patients with
severe anterior proclination as it produces lighter
forces over a longer span of activation. It can also be
used in adult patients for the same reason.
Reverse Labial Bow
This type of labial bow is so called because, activation
of the bow is done by opening the V-loop, instead of
compressing as is seen in the conventional labial bows.
The loop is placed distal to the canine and the distal
arm is bent at right angles to extend anteriorly as the
labial part of the bow.The free end of mesial arm is
adapted between the canine and first premolar and
eventually gets embedded in the acrylic base plate.
Activation is done by opening the loop which results in
lowering of the labial bow in the incisor region. To
maintain the proper
level of the bow, a compensatory bend is then given at
the base of the V-loop.
Mill's Retractor
This is a complexly designed labial bow made of 0.7
mm SSwire which has extensive looping in its design
to increase the flexibility and range of action of the
retractor . The anterior part of the bow extends till
mesial of the canine and then forms a complex loop
gingivally before ending in a retentive arm distal to the
canine. This type of a labial bow is indicated in
patients with increased overjet. However, due to
difficulty in construction and poor patient compliance,
it is not widely used.
High Labial Bow with Apron
Springs
As the name suggests, this type of labial bow extends
high into the labial vestibule. It is made up of a thicker
gauge SS wire (0.9-1 mm). The labial bow acts as a
support onto which apron springs (made from 0.4mm
wire) are attached wound. Apron springs help in
retraction of one or more upper anteriors. This type of
bow is made highly flexible because of the springs and
is therefore used for retraction in cases with large
overjet.
Apron spring is activated by bending it towards the
teeth, up to 3 mm at a time. Since it generates light
forces, it is also useful in adult patients. However, it is
difficult to construct and can cause soft tissue injury. It
may also lack patient compliance as too much wire is
visible.
Fitted Labial Bow
This type of labial bow is so called, as it is adapted to
the contours of the labial surface of anteriors. It is
mainly for retention after completion of fixed
orthodontic treatment. The U-Ioop is smaller compared
to the conventional labial bows.
References
1.Contemporary orthodontics by proffit
2.Textbook of orthodontics by foster
3. Design, construction and use of removable
orthodontic appliances by C. PHILIP ADAMS
4.Textbook of orthodontics by GRABER and
NEUMANN