Modified Hyrex Expander for Correction of Upper Mid Line Deviation / orthodontic courses by Indian dental academy

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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 EXPANSIONGrowth 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


Rate of Expansio

n

Form of Applian

ce

Age of Patient


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.


Effect of expansion on dental arch and on maxillary bases increases as the rigidity of the appliance(anchorage) is increased.

Form of Appliance(Donald j. Timms -pg 15)


Maxillary dental arch is widened partly by tilting the teeth bucally and partly by moving the maxillae apart, opening the midpalatal suture.

Changes of RME(Donald j. Timms )


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 applianceBandelette


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 EXPANSIONStory 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 typeA.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, low ering 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 mid-palatal 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 14-15 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 mesio-distal 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 cor rected 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 max illary arch dimensions and correct the midline asymmetry.

Molar bands were placed in the mouth, and an alginate impression was taken.

The impres sion and molar bands were then sent to the labora tory 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 con striction should be treated as early as possible to promote normal function and proper tongue posi tion; 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 likeli hood 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 inci sors 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 appli ances. The protocol can be adapted for each individual case. For patients allergic to nickel, the appliance can be fabricated with a pure tita nium 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 expan sion 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 six-year-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 clock wise 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 Fan-Type 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 fan-type 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 poste rior dentoalveolar structures after rapid maxillary expansion: A new method, Dentomaxillofac. Radiol. 36:356-359, 2007.


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Modified Hyrex Expander for Correction of Upper Mid Line Deviation / orthodontic courses by Indian dental academy

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