Modified hyrex expander for correction of upper mid line deviation /certified fixed orthodontic courses by Indian dental academy

MODIFIED HYRAX EXPANDER
FOR CORRECTION OF
UPPER MIDLINE DEVIATION

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Normal Anatomy

Morphology of the mid palatal suture has
been studied by MELSEN
(1975).

MAXILLARY EXPANSION
 Growth ceases first in the transverse

dimension. The constricted maxilla dentally
or skeletally always poses a problem for an
orthodontist . So diagnosing and treating
this problem first is an integral part in
orthodontics .

 The maxilla and upper teeth positions are

governed by the musculature surrounding
them, in patients showing constricted
maxillary arch it is mandatory to deal with
by applying an orthopedic forces across the
maxilla to expanding it.

Rapid maxillary expansion or
Palatal expansion through
dentofacial orthopedic
appliances not only
applicable by orthodontists
but also used in the field of
oral surgery and ENT


Stages of development used
by Bjork and Helm
1st stage

2nd Stage

3rd Stage


1) Human autopsy study –Persson
(1973,76,77) observed, earliest closure of
suture in girls at 15yrs and oldest unossified

suture was seen in women aged 27yrs .
2) 5% of sutural closure together with
mechanical interlocking can be broken
without surgical assistance than the average
of 25 yrs may be used as a general guide.
3) Davida (1926) – suture starts to ossify
posteriorly, and always shows a greater
degree of obliteration posteriorly than
anteriorly.
Age of The Patient
(Donald j. Timms )


Rate of Expansion
(Donald j. Timms -pg 15)
 By expanding at the rates of 0.3-0.5mm per

day, Orthopedic type of active expansion is
completed in 2 to 4 weeks, leaving little time
for the cellular response of the osteoclasts and
osteoblasts seen in slow expansion.


Form of Appliance
(Donald j. Timms -pg 15)
 Effect of expansion on dental arch and on

maxillary bases increases as the rigidity of
the appliance(anchorage) is increased.


Changes of RME
(Donald j. Timms )
 Maxillary dental arch is widened partly by tilting

the teeth bucally and partly by moving the
maxillae apart, opening the midpalatal suture.


 Is the activation of the
screw painful?
 The procedure is usually pain free. If pain

develops during procedure it indicates that the
suture is not opening or usually the appliance is
embedding in the palatal tissue or It might be
due to faulty appliance design.


HISTORICAL BACKGROUND
 Narrow maxilla has been recognized for

thousands of years by “Hippocrates”
 Number of slow expansion techniques were
employed by early dental practitioners like
Fauchard (1728) Bourdet (1757), Fox (1803),
Delabarre (1819), Robinson (1846), White
(1859).


Pierre Fauchard (1723)
First orthodontic appliance
Bandelette


Appliance Classification


According to the rate of expansion
 Slow [W arch, Quad helix, Coffin spring]
 Rapid [Hyrax, Minn, Isaacson]
 Ultra rapid [Surgically assisted]


According to appliance attachment
 Removable [Active plate and Functional appliances]
 Fixed:

 Tooth borne [Biedeiman appliance, Minn expander]
 Tooth/Tissue borne [Derichsweiler type, Haas type]

According to modality employed
 Orthodontic expansion
 Passive expansion
 Orthopedic expansion

SLOW MAXILLARY EXPANSION
 Story and Ekstrom: Slow expansion allows
physiologic adjustments and reconstitution of
sutural elements over a period of about 30 days.
 2-4 lbs of force, a little higher for older patients.
 1 mm expansion per week.
 S. E. has also been associated with more
physiologic stability and less potential for relapse
than with R. M.E.
Appliances used for S. M. E.
 Jackscrews
 Quad helix
 W arch

Banded type of appliances
 Hass type

 Hyrax type
 Derichsweiler type
 Isaacson type


Hass type
A.O. 1961;31: 73-90.
The RME expander as described by Haas is a tissue-borne fixed
split acrylic maxillary expansion appliance. Because the
appliance commonly produces orthopedic forces in the range
of 3 to 10 pounds, the expansion was deemed to be skeletal
and, therefore, more stable.


Derichsweiler type
[Derichsweiler; 1956]

Derichsweiler claimed an increase in nasal width, lowering of the
palatal vault, and straightening of the nasal septum due to the RME
allowing many mouth breathers to adapt to the use of the nasal
passages for respiration. The maxilla comprises the external walls of
the nasal cavity laterally, and expansion results in an increase in the
inter-nasal capacity.


Isaacson type
A.O. 1964;34: 256-270.

 Isaacson's Minne expander appliance is a special
spring-loaded appliance adapted to the first permanent
molar bands.
 It could be reduced in length to adapt narrow maxilla
by shortening the spring, tube, and rod.


Hyrax type [Biederman]
Hygienic appliance for rapid expansion.
J. Pract Orthod.1968;2:67-70.

Hyrax or Biederman RME appliance is a commonly used type of RME
appliance.5
It is tooth borne and consists of a screw with heavy wire extensions that
are soldered to the palatal aspects of the bands on the first molars and
pre-molars.


Bonded type Mundro et al 1977


Instructions on how to expand
Zeibe in 1930 : 180 degree rotations per day
 Upto age of 15 years : the turn 180 degree
is given as 90 degree in the morning and 90
degree in the evening.
 15-20 years : overall rotation of 180 is
possible by splitting the rotation into 4
turns of 45 degree each with approx equal
time lapse between them.
 Age over 20 years : 45 degree turn in the
morning and 45 in the night initially

Zimring and Isaacson in 1965 :
 Young or growing patients: two turns

each day for the first 4-5 days and one
turn each day for remainder of RME
treatment.
 Adult patients: two turns each day for
the first two days and one turn each day
for the next 5-7 days and one turn each
other day for the remainder of the RME
treatment.

Wertz RA. Skeletal and dental changes
accompanying rapid mid-palatal suture opening.
A.J.O. 1970;58:41-66.

 During expansion, bending of the alveolar

structures and buccal tipping of the posterior
maxillary teeth lead to posterior rotation of
the mandible, open bite, and an increased
vertical face dimension.


Examination of the skull in its lateral
aspects shows some interesting
changes with RME. There is a slight
downward & forward movement of
the Maxillae reported by Wertz-1977
& Hass-1970 . Actually showed an
increase in the opening of the
pterygomaxillary fissure.
Biederman-1973 explained this
forward movement as being caused
by the lateral buttressing of the
zygoma providing point of rotation.
One effect of the downward
maxillary rotation is to rotate the
mandible downward & backward.

INDICATIONS
 Marked narrowing of the arches
 Unilateral or bilateral cross bite
 Mandibular prognathism with reduced
anterior development of the maxillary base
 Steep palate with septal deviation and
mouth breathing due to enlarged adenoids
 Cleft lip and palate
 Mild arch length to tooth material
deficiency.(1mm of expansion in post = 0.7
mm increase in arch perimeter)

CONTRAINDICATIONS
 Uncooperative patients
 Pts with anterior open bites, and
 Steep mandibular plane angles


 Which teeth are used for anchorage of the rapid
palatal expansion appliance?
 Usually permanent first molars and either the first
bicuspids or the deciduous first molars. Four
teeth

 Are more than four teeth ever banded?
 No. Four teeth are enough for a parallelism
problem on insertion. A properly made appliance
with four bands offers adequate support.


 How late can deciduous first molars be used
for anchorage?
 If half the root length remains and the teeth
are not loose, the deciduous first molars can
be used.
 What do you do if these teeth have less than
half their root length or are loose?
 Wait for the eruption of the first bicuspids.


 What's wrong with the banding cuspids?
 Cuspids and second molars do not make good
abutments. They present a greater problem of
parallelism. They carry the appliance to a gingival
area that is more susceptible to irritation and
inflammation.
 What is the tissue-bearing area of the appliance?
 The initial outline of the acrylic palate portion runs
3-4 mm from the gingival margins of the teeth.
 It ascends the palate mesial to the first bicuspids
or deciduous first molars, and distal to me
permanent first molars. It ends in the mid-palatal
suture line. 3 mm of acrylic are ground off me midpalatal crest flattening the appliance and making
room for the palate to descend.
 The acrylic is bevelled about 3 mm all around the
periphery of the two sections. What remains is
tissue-bearing and is not adjusted or relieved.

 What about the all-wire framework appliance
with no acrylic button?
 This appliance works all right for young
patients. It is not usually recommended in 1415 year olds because the wire appliance pushes
against just the teeth and buccal plate.
 This is not enough resistance for the high
forces used (10-20 lbs.). In the deciduous
dentition the bones are much less resistant to
expansion.
 Are removable appliances effective?
 No. They cause movement of the teeth and
alveolar process but do not open the suture.
Occasionally it might work. More often the
forces are so great that they dislodge the
appliance. Removable appliances usually only
tip the teeth with a kind of orthodontic action.

What are the steps in palatal
expansion procedure?
 Stage I— Active expansion.

 Stage II -Stabilization.
 Stage III— Continued orthopedic influence.
 Stage IV— Routine orthodontic treatment.


How is the appliance activated?
 The appliance is activated with ¼-turns of the expansion

screw using an .036 wire key.
 It is important that a piece of string or dental floss be tied
to the key on one end and to a finger on the other because
the turns are always made toward the back of the throat.
 A good procedure after cementing is to wait 15 minutes
and give the appliance a ¼-turn; take photos; give the
appliance another ¼-turn; demonstrate the method to the
patient and parent taking a third ¼-turn; after a short
interval have the patient or parent make the fourth ¼-turn.
After that, the patient is instructed to make one ¼-turn
twice each day, morning and night. The patient is seen at
approximately weekly intervals.
 At these visits take 2-6 additional turns being guided by
how well the patient tolerates this. Usually there is no
problem.

Why the four turns after
cementation?
 This will initiate the opening of the suture and

minimize the tipping of the teeth. If the
patient is over 15 years of age only two turns
are given at the time of cementation, but
otherwise the adjustment is the same.


What do you do if you suspect
that the suture is not opening
and/or if pain develops?
 Usually this would be in an older patient

and what you do is to slacken off on the
screw adjustment; let the tissue recover;
and then re-start RME procedure but on a
much slower basis— taking two or three
months to expand instead of a few weeks.
You are guided by the patient, going at a
rate consistent with his comfort.

What is the reason for the
speed in the first place?
 The faster the movement, the more

orthopedic response and the less dental
response; the more palatal widening and the
less dental tipping.


How do you know when you are
through?
 The aim is to overcorrect the crossbite. You

just about reverse the crossbite. Check the
suture opening with an occlusal x-ray.


What is done after the
expansion appliance is removed?
 After the expansion appliance is removed, it

is replaced by a loose-fitting acrylic plate with
no wires.
 It is retained in place by the tongue. This may
train the tongue to a higher position which is
good because the tongue in these cases
usually has a low posture.
 The acrylic is trimmed in such a way to allow
the teeth to relapse to the extent that they
were tipped out in treatment.

What do you do about the
diastoma?
 It corrects itself. Within a month after

stabilization the centrals come back together
again. However, there will have been an
increase in arch width and length and the
roots of the centrals will be in a better mesiodistal axial inclination.


HAZARDS OF RME









Oral hygiene
Length of fixation
Dislodgement and breakage
Tissue damage
Infection
Failure of suture to open


INTRODUCTION THROUGH ARTICLE
 Mixed-dentition patient with maxillary trans-

verse deficiency, when a deciduous canine is
lost prematurely, the permanent incisors may
migrate toward the affected side, reducing or
closing the space available for eruption of the
permanent canine.


 Lateral displacement of the incisors also

results in maxillary asymmetry and significant
midline deviation. These problems can be
corrected by adding a buccal arm to a Hyrax*
rapid palatal expander.
 The present article describes the use of such a
modified Hyrax appliance.


CASE REPORT
 An 8-year-old female presented with a Class I

malocclusion, a maxillary transverse
deficiency, and a midline discrepancy due to
the premature loss of the maxillary left
deciduous canine


 Rapid palatal expansion was planned to

increase the maxillary arch dimensions and
correct the midline asymmetry.
 Molar bands were placed in the mouth, and
an alginate impression was taken.
 The impression and molar bands were then
sent to the laboratory for assembly of a
modified Hyrax appliance.

The appliance was fabricated
with the following components:
 A stainless steel frame,
 Two molar bands,

 Two palatal arms welded to the bands and
extending to the mesial surfaces of the canines,
 A 9mm central jackscrew, and

 A buccal arm with a terminal loop extending
from the molar band to the labial surface of the
central incisor on the side opposite the maxillary
midline deviation

The finished appliance was
delivered as follows
 Separators were placed three days before

appliance insertion.
 The appliance was tested in the mouth for
proper fit.
 The labial surface of the incisor to be bonded
to the buccal arm of the appliance was etched
and primed.


 The appliance was cemented in place.
 The terminal loop of the buccal arm was bonded

to the incisor with composite.
 The palatal and buccal arms of the appliance
were correctly positioned and inclined.


 The appliance was activated with a quarter-turn
twice a day for 15 days. This generated about 2-3kg

of force, producing .5mm of expansion per day.
Thus, the total amount of expansion was about
7.5mm.
 The patient was seen once a week for two weeks.
After the palatal expansion was complete, a
stainless steel ligature wire was tied in to deactivate
the appliance.
 The expander was left passively in place to allow the
results to stabilize and the contra lateral incisors to
drift into the space that had been opened

 a process that was expected to last four to six

months . The patient was scheduled for
bonding of full fixed appliances to complete
treatment.


DISCUSSION
 The midline discrepancy created by lateral
displacement of maxillary incisors after

premature loss of a deciduous canine may cause
anterior crowding, which can lead to secondary
crowding in the mandibular arch.
 Maxillary deficiency may restrict mandibular
development in the sagittal or transverse
dimension. Arch constriction should be treated
as early as possible to promote normal function
and proper tongue position; a narrow palate is
associated with a low tongue position, which
often leads to mouth-breathing.

 Symmetry of the dental arches is critical to
achieve maximum intercuspation, a functional

occlusion, and stability, and to reduce the likelihood of TMJ dysfunction.
 The modified Hyrax expander described here can
facilitate the correction of these problems
without the need for extractions.
 Increasing the arch length and improving the
archform create extra space that can be
concentrated in the canine area.

 The consolidation of the half-arch contra

lateral to the maxillary midline deviation
allows optimal distribution of the space
produced by the palatal expansion,
permitting the displaced incisors to move into
the available space and, in turn, allowing
proper eruption of the permanent canine.


 Such a procedure can gain 7-9mm of space,

enough to avoid problems with canine
eruption that would require more complex
treatment procedures. Moreover, a midline
deviation of as much as 5-6mm can be
resolved.


 Use of the modified Hyrax expander with a
buccal arm is an effective intervention that can
reduce the duration of treatment with fixed

appliances. The protocol can be adapted for each
individual case. For patients allergic to nickel, the
appliance can be fabricated with a pure titanium
frame.


Schellino E, Modica R, Benech A, Modaro E. REM: la vite ragno
secondo Schellino e Modica. Boll Interm Orthod. Leone 1996;55:
36-39.

 In 1996, Schellino et al designed a spider screw
named "Ragno," which works asymmetrically

and allows ''fan opening.'‘
 The development of a rapid-expansion
appliance, which only affects the anterior region
of the maxilla, certainly represents a significant
improvement in conventional RME appliances.
 It avoids undesired expansion of the maxilla in
the region of the upper first and second
premolars, which creates an advantage in the
future treatment of the case.

 Levrini and Filippi used a Ragno appliance to

expand the maxilla in a study involving a sixyear-old male with bilateral cleft lip and
palate that required RME only at the anterior
region. Posttreatment plaster models
revealed that the intercanine width increased
more than intermolar width, which was
different from previous studies.


 Sadeddin evaluated the effect of a fan-type

RME on anteriorly constricted cases. He
found significantly greater expansion in the
intercanine width than in the intermolar
width, increase in upper arch parameter, and
downward and forward movement of the
upper arch in addition to clockwise
movement of the mandible.


AJO-DO Volume 1987 Feb (111 - 116):
Nasal airway following maxillary expansion Warren, Hershey, Turvey, Hinton, and Hairfield

 The present study assessed the effects of rapid
maxillary expansion and surgical expansion on

nasal airway size to determine how useful these
techniques are for breathing purposes.
 The results demonstrate that both procedures
generally improve the nasal airway. However,
approximately one third of the subjects in both
groups did not achieve enough improvement to
eliminate the probability of obligatory mouth
breathing.
 These findings suggest that maxillary expansion
for airway purposes alone is not justified.

AJO-DO Volume 1998 Dec (638 - 645): Stability of
orthopedic and surgically assisted rapid palatal expansion
over time Jeffrey L. Berger, BDS, Dip.Ortho,...

 This study was designed to examine and
compare the dental and skeletal changes over
time for both orthopedic maxillary expansion
and surgically assisted palatal expansion. The
study was divided into two groups.

 The surgical and nonsurgical techniques
displayed similar trends over time although the
surgical group contained a greater quantity of
expansion. Both the orthopedic and the surgical
groups showed stable results.

A Comparison of the Effects of Rapid Maxillary Expansion and FanType Rapid Maxillary Expansion on Dentofacial Structures
[Cenk Doruk, Ali Altug B,; Faruk Ayhan Basciftci]
 The aim of this study was to evaluate and compare the sagittal,








transverse, and vertical effects of rapid maxillary expansion (RME)
and fan-type RME on dentofacial structures.
The study group consisted of 34 patients, 14 boys and 20 girls
(average age 12.5 years), selected without considering their skeletal
class and sex.
The fan-type RME group comprised 17 subjects, who had an
anterior constricted maxilla with a normal intermolar width. The
RME group comprised 17 other subjects, who had a maxillary
transverse discrepancy with a posterior crossbite.
The records obtained for each patient included a lateral and a
frontal cephalometric film, upper plaster models, and occlusal
radiograph obtained before treatment (T1), after expansion (T2),
and immediately after a three-month retention period (T3).
The data obtained from the evaluation of the records before and
after treatment, after treatment and after retention, and before
treatment and after retention were compared using paired /-test.

 Further comparisons between the groups were

made using Student's /-test.
 There was significantly greater expansion in the
intercanine than in the intermolar width in the fantype RME group as compared with the RME group.
 Downward and forward movement of the maxilla
was observed in both groups. The upper incisors
were tipped palatally in the RME group, but they
were tipped labially in the fan-type RME group.
 There was significantly greater expansion in the
nasal cavity and maxillary width in the RME group
as opposed to the fan-type RME group.
(Angle Orthod 2004;74:184-194.)


REFERNCES
 Van Limborgh J. The role of genetic and local environmental factors

in the control of postnatal craniofacial morphogenesis. Acta Morphol
Neerl Scand 1972;10:37-47.
 AJO-DO Volume 1997 Mar (321 - 327): Skeletal and dental changes
after maxillary expansion in the mixed dentition Müge
Sandikçioglu,and Serpil .
 AJO-DO Volume 1998 Dec (638 - 645): Stability of orthopedic and
surgically assisted rapid palatal expansion over time Jeffrey L.
Berger, BDS, Dip.Ortho,...
 AJO-DO Volume 1987 Feb (111 - 116):
Nasal airway following maxillary expansion - Warren, Hershey,
Turvey, Hinton, and Hairfield
 Oktay, H. and Kilic, N.: Evaluation of the inclination in posterior

dentoalveolar structures after rapid maxillary expansion: A new
method, Dentomaxillofac. Radiol. 36:356-359, 2007.


Modified hyrex expander for correction of upper mid line deviation /certified fixed orthodontic courses by Indian dental academy

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