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orthodontic waves 69 (2010) 33–38
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Mixed separator appliance: A new option for maxillary
expansion
Matheus Melo Pithon *
Faculty of Dentistry, Federal University of Rio de Janeiro – UFRJ, Brazil
article info
abstract
Article history:
The aim of this article was to describe the fabrication and clinical application of a new
Received 16 September 2009
separator appliance that allies the favorable characteristics of the Haas and Hyrax types of
Received in revised form
separators. With this appliance separation of the median palatine suture was achieved with
4 November 2009
greater support with the acrylic component in the active period and better hygiene without
Accepted 10 November 2009
the acrylic component in the period of containment. Therefore it could be concluded that
Published on line 9 December 2009
the mixed separator appliance is a good option for performing rapid maxillary expansion.
# 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved.
Keywords:
Rapid maxillary expansion
Maxillary expansion
1.
Introduction
One of the most recognized clinical procedures in orthodontic
practice, due to its efficiency and predictability, is rapid
maxillary expansion (RME) [1]. RME or separation corrects the
transverse atresia of the maxilla, an extremely frequent type
of malocclusion that is established early and is not selfcorrecting [2]. The literature mentions an infinite number of
appliances used for this purpose [3–9], nevertheless, the most
used and disseminated appliances up to today are the
appliances of the Haas [10] and Hyrax type [11,12].
The Haas separator appliance idealized by this author in
1961 [10] is composed of orthodontic bands fabricated for the
first molar and first premolar on each side, which are united by
a structure made of stainless steel wire by the vestibular and
palatine ends of the bands, and a central screw. All these
elements are incorporated into an acrylic mass that stays in
contact with the palatine mucosa. The Haas appliance uses a
dento-mucosal supported anchorage system. The magnitude
of force released by this appliance, associated with its
anchorage system, provide excellent orthopedic movement
(movement of the bone bas) with minimal orthodontic
movement response (tooth movement). However, when this
appliance is removed, thick biofilm accumulation is noted
under the acrylic component.
In an endeavor to make the separator more hygienic,
Biederman [11,12] developed the Hyrax appliance which, in
the same way as the Haas appliance is fabricated with
bands on the first molars and first premolars, which are
united by the vestibular and palatine faces, by means of a
stainless steel wire and an expansion screw that has four
cast steel wire rods, and each of these rods is welded to the
four bands of the molars and premolars. It is differentiated
from the Haas by the anchorage, which in this model
anchorage is purely dental. It presents a certain amount of
orthodontic movement (tooth movement), in addition to
orthopedic movement (bone movement), which would be its
limitation [13].
* Correspondence address: At Av. Otávio Santos, 395, sala 705, Centro Odontomédico Dr. Altamirando da Costa Lima, Vitória da Conquista,
CEP: 45020-750, Bahia, Brazil. Tel.: +55 7730842020.
E-mail address: [email protected].
1344-0241/$ – see front matter # 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved.
doi:10.1016/j.odw.2009.11.001
34
orthodontic waves 69 (2010) 33–38
In an endeavor to reduce the limitations of these two
appliances, the aim of the present article was to describe the
fabrication of a new separator appliance that allies the favorable
characteristics of the Haas and Hyrax types of separators.
2.
Case report
The patient with 13-year-old leukoderma boy, came to the
orthodontic consulting rooms with the chief complaint of
crooked teeth. In the intraoral clinical exam, maxillary atresia
was noted, with lack of space for eruption of the maxillary left
canine (23) (Fig. 1). As complementary exams, periapical,
panoramic, teleradiographic and superior occlusal radiographs of the maxilla were requested (Fig. 1f). From the
preceding evaluations, the option was to perform orthopedic–
orthodontic treatment, beginning with the placement of a
maxillary suture separating orthodontic appliance, followed
by correcting the position of the teeth by means of a fixed
orthodontic appliance.
Fig. 1 – (a–e) Initial intraoral photographs and (f) initial occlusal radiograph.
orthodontic waves 69 (2010) 33–38
35
Fig. 2 – (a) Screw adaptation, (b) welding the screw to the orthodontic bands, (c) isolation of the screw orifices and making the
dyke with radiographic film, (d) concluded appliance and (e) intraoral photographs after placement of the separator.
3.
Description of the separator appliance used
The appliance was fabricated on bands adapted to the
maxillary first premolars (14 and 24) and maxillary first
molars (16 and 26). Once the transfer model with the bands in
place was obtained, an expansion screw with long rods was
contoured. After contouring, the rods were welded to the
bands, and the weld was polished.
After this, the screw was covered with wax to prevent the
resin from obliterating the orifices for the purpose of
activating it during acrylization. In order to separate the
acrylic components of the left and right sides, a piece of used
radiographic film served as a dyke, and was placed exactly
over the median palatine suture. After the preparatory stage,
the acrylic component was applied by the powder/liquid
technique. Once it was polymerized, it was finished and
polished (Fig. 2).
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orthodontic waves 69 (2010) 33–38
Fig. 3 – (a–d) Intraoral photographs at the end of 21 of activation and (e) occlusal radiograph after separation.
4.
Activation of the appliance
After cementation (Fig. 2e), a period of 30 min was
waited before performing the first activations. Initially it
was activated 4 (1 mm), and the patient was instructed
to activate it 2 a day for 7 days, and then return to
the consulting room. At the end of 21 days of activation,
the necessary separation of 11.5 mm was obtained
(Fig. 3).
orthodontic waves 69 (2010) 33–38
37
Fig. 4 – (a) Acrylic surface wear, (b) acrylic displacement with the sharp pointed instrument; (c) acrylic removal with forceps,
(d) polishing the metal structure, (e) appliance after removal of the acrylic component and (f) acrylic component removed.
5.
Stabilization and removal of the acrylic
component
After obtaining the desired separation, the screw was
stabilized with a braided ligature wire. In the same session,
the acrylic component was removed with the aid of a bur for
resin removal mounted in a high speed handpiece. Removal
began with wear on the top part of the acrylic component,
followed by displacement of the acrylic component with a
sharp tipped instrument, and when it was loose, the resin was
removed with clinical forceps. Now without the acrylic
component, the appliance was kept in place for a further 6
months, until there was bone formation in the separated area
(Fig. 4).
6.
Discussion
The purpose of the present article was to describe a new
option to use in the rapid maxillary expansion procedure. The
goal of the described appliance is to present the favorable
characteristics of the Haas and Hyrax appliances.
The Haas type of appliance has an acrylic resin component
that helps during separation, by providing mucosal and dental
support, resulting in more anchorage and reducing the effects
on the teeth. Whereas this acrylic component helps separation
in the initial phases, it leads to food and bacteria accumulation
in the containment phase.
In an endeavor to make the Haas appliance more hygienic,
Biederman developed the Hyrax appliance that has the same
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orthodontic waves 69 (2010) 33–38
indications as those of the Haas unit, however, with support
only on the teeth, without the acrylic component. If, on the
one hand, removal of the acrylic made it more hygienic, on the
other, it reduced anchorage, providing a greater effect on the
teeth during the attempt to open the suture, particularly in
patients at an advanced age.
In the search for a compromise between the two,
it was decided to place the acrylic component in the
initial stage of activation, and remove it in the containment
stage.
The metal structure of the appliance is similar to that of
the Hyrax appliance, but the acrylic component has been
added to it. The acrylic is inserted in such a way that its postactivation removal is facilitated. A smaller quantity of acrylic
was placed, making it easy to remove without compromising
anchorage.
After having achieved the desired separation, the screw
was stabilized with a braided ligature wire, and this method
was chosen because it is hygienic and it is easy for the patient
to clean. In the same stabilization session, the acrylic
component was removed. The removal procedure was
performed by weakening the top surface of the acrylic block
with a high speed bur for resin removal, and once weakened, it
was easy to remove.
With the treatment performed in this clinical case, the
appliance here described demonstrated its effectiveness when
compared with the Haas separator.
The disadvantage with regard to the use of this
new separator arises from the need to add a clinical stage,
which would be to remove the acrylic. The stage is
unnecessary when separators of the Hass and Hyrax types
are used.
7.
Conclusion
The described appliance was shown to be effective for palatine
suture separation, and more hygienic in the containment
stage, preventing the accumulation of microorganisms and
biofilm formation.
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