Download A New Appliance for Molar Distalization

A New Appliance
for Molar Distalization
Tiziano Baccetti, DDS, PhD, and Lorenzo Franchi, DDS, PhD
Department of Orthodontics
(Chair: I. Tollaro)
University of Florence, Italy
CLINICAL INDICATIONS FOR THE DISTALIZATION
APPLIANCES FOR MOLAR DISTALIZATION
OF MAXILLARY FIRST MOLARS
The appliances for molar distalization can be classified as
Molar distalization at the maxillary arch is an important part
extra-oral appliances and intra-oral appliances (Table). One of
of the therapeutical armaments in the everyday orthodontic
the fundamental requirements of any orthodontic appliance,
practice. Clinical indications for this type of dental movement
APPLIANCES FOR MOLAR DISTALIZATION
EXTRA-ORAL
INTRA-ORAL
are represented by the majority of disharmonies with Class II
molar relationships. In particular, the technique is efficient in
Headgears
the correction of distal molar relationships associated with
maxillary skeletal protrusion. Other targets for molar distalization therapy are the mesial position of upper first molars
due to different causes and tooth-size/arch-size discrepancies
at the maxillary arch.
In greater detail, clinical indications to distalization of maxil-
Distalizing arch by Wilson
Plate with distalizing springs (Cetlin)
Magnets
NiTi springs
Locasystem
Jones Jig
Pendulum
Distal Jet
First Class
Distalizer according to Veltri
lary first molars can be classified as follows:
a) skeletal problems:
those for molar distalization included, is the need for a mini-
- maxillary protrusion
mal amount of patient’s compliance. This is why intra-oral
- maxillary protrusion associated with mandibular
devices have become progressively more popular as an alter-
retrusion
native to headgears starting from the 1980s. Several intra-
b) dento-alveolar problems:
oral appliances for molar distalization, however, necessitate
- mesial position of the upper dental arch
patient’s cooperation as they require the use of either extra-
- tooth-size/arch-size discrepancy at the upper arch
oral tractions (Cetlin’s technique) or intermaxillary Class II
c) dental problems:
elastics
(distalizing arch by Wilson, Locasystem, NiTi
- mesial position of maxillary first molars (due to caries,
springs). Esthetics has been a major goal in the creation of
early resorption, or severe infraocclusion of second decidu-
new intra-oral appliances to be positioned on the palatal side
ous molars).
of the upper arch. Best choices in this regard are the
The anatomical features of maxillary first molars, the role of
Pendulum, the Distal Jet, the First Class, and the Distalizer
these teeth within the occlusion, and the biomechanic require-
according to Veltri. Further, biomechanical considerations
ments concerning their orthodontic movement make molar
concerning the possibility to achieve a bodily movement of
distalization a complex chapter of contemporary orthodontics.
maxillary first molars associated with the least amount of
This is witnessed by the great variety of appliances that have
anchorage loss in the anterior part of the upper arch have a
been proposed for molar distalization during the two last
direct influence in the selection of appliances for molar distal-
decades.
ization. While waiting for data regarding anchorage loss for
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other intra-oral devices, the literature indicates a significant
anchorage loss of about 20-25% for the Jones Jig (Haydar and
Uner, 2000) and for the Pendulum (Bussick and McNamara,
2000).
THE NEW DISTALIZER
The new appliance for molar distalization that we present here
Fig. 2 - Customized key for screw activation
originates from a former idea by Dr. Nicola Veltri (Veltri, 1999)
with our subsequent personal modifications. This is the reason why we will refer to the appliance with the generic name
of “New Distalizer”. The appliance consists of a palatal sagittal screw for bilateral molar distalization according to Veltri
(Leone A0629-08 or Leone A0629-11) which is connected to
bands on maxillary first molars and on maxillary second premolars (or maxillary second deciduous molars). Auxiliary
device for anchorage is represented by a Nance button which
is soldered to the body of the screw (fig. 1).
Fig. 3 - Diagrammatic representation of biomechanic aspects of
the New Distalizer (see text for explanation)
the molar bands, is cemented once again as a retention appliance.
In presence of mesial rotation of the maxillary first molars it
is recommended to correct this anomaly by means of a
transpalatal arch before molar distalization.
The advantages of the New Distalizer with respect to other
intra-oral devices for molar distalization include:
1) From a biomechanical point of view, the New Distalizer is
Fig. 1 - The New Distalizer
able to induce a bodily movement of the maxillary first
As for the clinical management of the appliance, the screw is
molars. The point of force application is situated at the level
activated by means of a customized key (fig. 2) at the rate of
of the body of the screw, due to the extreme rigidity of the
two quarters of a turn every week (e.g., one quarter of a turn
system comprising the screw, the connecting arms, and the
every Tuesday and another quarter of a turn every Friday). If
bands. Therefore, the force vector passes through the cen-
we consider that every quarter of a turn corresponds to an
ter of resistance of maxillary first molars (fig. 3).
2) The activation of the appliance is very easy for the patient
activation of the appliance of 0.2 mm, the amount of molar
due to the use of the customized key (fig. 2).
distalization in one month is about 1.5 mm. The correction of
3) Esthetics is warranted by the palatal location of the appli-
a full Class II molar relationship (about 5 mm) requires an
ance.
average 3-month-and-a-half period of active therapy. At the
4) The laboratory cost for the appliance is lower when com-
end of the active phase of therapy, the appliance is removed,
pared to other palatal devices for molar distalization.
the screw may be blocked, and the arms connecting the screw
to the bands on the second premolars are cut off. The appli-
5) The clinical management of the appliance is extremely sim-
ance, which now consists of the screw, the Nance button and
plified by the fact that, at the end of the active period of
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therapy, the appliance can be transformed directly into a
retention appliance during a single appointment, without
any other additional laboratory phases.
6) The evaluation of a few clinical cases treated with the New
Distalizer suggest that the amount of anchorage loss in the
anterior part of the upper arch is smaller than in cases
treated with either the Jones Jig or the Pendulum.
CLINICAL CASE
Fig. 5a, b, c - M. B., intraoral views before treatment
immediately after cementation of the New Distalizer
The clinical effects of the New Distalizer are better illustrated
when we describe the dento-skeletal modifications that
occurred in a young patient.
M.B., 12 years old, presents with the following features before
treatment:
- Class I molar relationship on the right side and end-toend molar relationship on the left side.
- Tooth-size/arch-size discrepancy with crowding, especially at the upper arch (upper canines are blocked out of
occlusion).
- Skeletal retrusion of both the maxilla and the mandible
(fig. 4).
Fig. 5b
- Normal vertical relationships (fig. 4).
- Flat facial profile (fig. 4).
Due to unfavorable characteristics of both skeletal sagittal
relationships and facial profile, treatment of tooth-size/archsize discrepancy with extractions appeared contraindicated.
Treatment plan, therefore, included molar distalization at the
upper arch by means of the New Distalizer.
Fig. 5c
After application of elastic separators for three days, bands
are adapted to maxillary first molars and second premolars.
The appliance is then cemented at the upper arch (fig. 5a, b,
c). Once obtained a molar distalization of about 4.5 mm (after
3 months from start of therapy, i.e. 24 activations of the
screw), the appliance is removed, the arms and bands connected to the second premolars are cut off, and the appliance
Fig. 4 - M. B.,
cephalometric tracing
at the start of
treatment
is cemented again as a retention appliance. The retention
appliance then consists of the bands on the maxillary first
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Fig. 7a, b - M. B., radiographic evaluation of distalization sites
Fig. 6a, b, c - M. B., intraoral views at the end of active phase
of molar distalization (about three months). The active appliance has
been transformed into a retention appliance
Fig. 7b
Fig. 6b
Distalization
of the upper first molar:
mesial movement of the cuspid = 4.3 mm
mesial movement of the apex = 4.1 mm
----- = before treatment
= after distalization
Fig. 6c
Fig. 8 - M. B., structural superimposition on the stable structures
of the maxilla according to Björk
molars, the corresponding arms, the palatal screw, and the
Nance button for anchorage (fig. 6a, b, c). Radiographic
Skieller) before and after active phase of therapy with the dis-
examination shows the bodily distalization of the maxillary
talizer reveals the amount of distal movement of maxillary
first molars, with normal appearance of both the alveolar bone
first molars and of anchorage loss measured as mesial move-
and the periodontal ligament of both molars and second pre-
ment of the maxillary incisors (fig. 8).
molars (fig. 7a, b).
The superimposition shows a net distalization of maxillary
A superimposition evaluation of patient’s cephalometric trac-
first molars of 4.3 mm and 4.1 mm when measured at the
ings (according to the structural method by Björk and
mesial cusp and at the mesial apex respectively. The minimal
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difference between these two measurements indicates that a
bodily dental movement has occurred with a minimal amount
of distal tipping. The amount of anchorage loss as measured
as mesial movement of the maxillary incisors at the end of the
active phase of molar distalization is approximately zero.
After about two months, premolars spontaneously migrate
posteriorly due to the traction exerted by transeptal fibers (fig.
9a, b, c).
The left maxillary canine accommodates in the
upper arch. The patient is now ready for final therapeutical
Fig. 9c
strategies to gain further space in the upper arch (stripping
and proclination of maxillary incisors) in order to also accom-
REFERENCES
1) Björk A, Skieller V. Postnatal growth and development
of the maxillary complex. In: McNamara JA Jr., ed. Factors
affecting the growth of the midface. Monograph 6,
Craniofacial Growth Series. Ann Arbor: Center for Human
Growth and Development, The University of Michigan,
1976; 61-99.
2) Haydar S, Uner O. Comparison of Jones Jig molar distalization appliance with extraoral traction. Am J Orthod
Dentofac Orthop 2000; 117: 49-53.
Fig. 9a, b, c - M. B., intraoral views after spontaneous posterior
drifting of premolars
3) Bussick TJ, McNamara JA Jr. Dentoalveolar and skeletal
changes associated with the Pendulum appliance. Am J
Orthod Dentofac Orthop 2000; 117: 333-43.
4) Fortini A, Lupoli M, Parri M. The First Class Appliance
for rapid molar distalization. J Clin Orthod 1999; 33: 32228.
5) Veltri N. Espansione mascellare a 360 gradi.
Sistematica dell’utilizzo di apparecchi fissi con vite per la
correzione delle anomalie del mascellare superiore.
Bollettino di Informazioni Ortodontiche Leone 1999; 63:
25-28.
Fig. 9b
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for the complete line of Veltri Expansors™.
modate the right maxillary canine in the arch. The occlusion
will ultimately be finished by means of fixed appliance
therapy.
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