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By
Dr.dhanyabhiram.k
HYGENIC RAPID
EXPANDER
HISTORYHISTORY
 The narrow maxilla has been recognized for thousands of years by “Hippocrates” 
•  A number of slow expansion techniques were employed by early dental 
practitioners like Fauchard (1728) Bourdet (1757), Fox (1803), Delabarre 
(1819), Robinson (1846), White (1859)
• The first published work originated in United State with Angle in (1860) who 
placed a screw appliance between maxillary premolars of a girl age 14.5 years
and widened her arch one quarter inch in two weeks. 
• Early 1900’s are know as the “maxillary expansion years”
• At this stage in orthodontic history numerous articles pointing to the interrelations of 
orthodontics and Rhinologic treatment procedures appeared in the literature . 
• G.V.I Brown a noted rhinologist was one of vociferous proponents of suture opening 
for purpose of increasing nasal permeability
• Lundstrom and later Brodie and associates also challanged the expansion . 
• IncidenceIncidence
                       The incidence of transverse 
maxillary deficency is estimated to be between 
8-18% of patients presenting for orthodontic 
consultation
INTRODUCTION 
•  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.
• Palatal expansion occupies a unique In dentofacial therapy. 
• By its tooth movements and mechanics it must basically come with in the 
field of orthodontics ,yet its ramifications take it into such other surgical 
disciplines as oral ,ENT and plastic surgery .
• Expansion can be divided into various arbitrary categories including 
ORTHODONTIC,PASSIVE & ORTHOPEDIC EXPANSION 
• Orthodontic ExpansionOrthodontic Expansion: 
               It is well known that expansion of the dental arches can be produced by a                                   
                                  variety of orthodontic treatments, including those that employ fixed 
appliances.
• Passive ExpansionPassive Expansion
When the occlusion is shielded from the forces of the buccal and labial musculature, a 
widening of the dental arches often occurs. 
             This expansion is not produced through the application of extrinsic biomechanical                      
                                   forces, but rather by intrinsic forces such as those produced by the tongue.
•  ExampleExample as passive expansion are the dimensional changes in the dental arches produced               
                                                   by such vestibular shield appliances as the FR-2 of Frankel.
Orthopedic ExpansionOrthopedic Expansion:
                  Rapid maxillary expansion (RME) appliances are the 
best examples of true orthopedic expansion in that changes are 
produced primarily in the underlying skeletal structures rather than 
by the movement of teeth through alveolar bone
CLASSIFICATION
•  According to the rate
 a) rapid 
b) slow 
• According to type of expansion
 a) orthodontic
 b) orthopedic
 c) passive
• According to direction 
a) anterior
 b) posterior
 c) unilateral
 d) bilateral
 e) 3-dimensional
• According to type of appliance
        a) removable 
        b) fixed -- banded or bonded 
1.Tooth borne e.g. HYRAX , Issacson
2. Tooth and tissue borne e.g Hass
• According to the jaw 
          maxillary e.g Transpalatal arch,HYRAX
          mandibular e.g. Active lingual arch
•According to the active element
                     Screws
               Dental expansion e.g Sectional 
screw ,                                           Traction 
screw 
               Skeletal e.g HYRAX
Applied Anatomy:
•  Each maxilla has a body and zygomatic, frontal, alveolar and palatine process.
• Body of the maxilla articulates with the following bones 
•  Cranially - 1) Frontal, 2) Ethmoid
• Facially :-1) Nasal, 2) Lacrimal, 3) Inferior nasal conchae, 4) Vomer, 5) Zygomatic 
and Palatine 
• Most of these bones bind the maxilla posteriorly and superiorly by sutural joints 
leaving the anterior and inferior aspect free 
 In theory this suture is formed by the
junction of the three opposing pairs of bones
namely premaxillae, maxillae and the palatine but
often for practical purposes they will be treated as
single entity called as a Midpalatal suture.Midpalatal suture.
• The morphology of the mid palatal suture has been studied by MELSEN (1975). 
•  Stages of development used by Bjork and Helm
  First stage : 
• Covering the infantile period. 
• The suture is very broad and Y shaped with the vomerine bone placed in a V shaped                  groove 
between the two halves of the maxilla.
 Second stage : Juvenile period, the suture is found to be more wavy. 
Third stage : Adolescent period, the suture is characterized by a more tortuous course with increasing 
inter digitations.
Infancy - Y-shape
Juvenile - T-shape
Adolescence - Jigsaw
puzzle
Two yrs of age 
9yrs of age
 13yrs of age
ETIOLOGY
• The causes of buccolingual discrepancies could be either genetic or 
environmental.
•  According to Graber, and Harvold, Cheirici and Vargervi many 
constricted maxillary dental arches are the result of abnormal function. 
•  Harvold in his experimental work created narrow maxillary dental arches 
in rhesus monkeys by converting them from nasal to obligatory oral 
respiration.
•  All patients considered for RME should be examined for nasal 
obstruction and, if obstruction is found, they should be referred to an 
otolaryngologist before orthodontic treatment
hygenic rapid maxillary expansion in orthodontics
Diagnostic aidsDiagnostic aids
• While Considering RME for young adults, occlusal radiographs can be used for 
analysing the palatal suture status. 
             A radiologically visible midpalatal suture corresponds histologically to a 
predominantly straight running oronasal suture, which projects largely into the 
saggital X – ray path. 
• Only small areas of interdigitation, if any are to be expected and the percentage of 
suture obliteration is low. 
2. Radiological invisible suture corresponds histologically to a relatively large area of 
interdigitation, an oblique running suture course in relation to X ray path or bone 
structures projecting above the suture course.
•  Percentage of suture obliteration to be expected is also low in this group.
Indications for RME Dental indications
1. Posterior Cross bite (unilateral/bilateral)
2.  Elimination of inter arch transverse discrepancies prior to orthopedic intervention in 
class II malocclusions
 3. Activation of the circummaxillary sutural system in treatment protocols / Class III 
4. Cleft palate patients with collapsed maxillary arch.
 5. In cases requiring face mask therapy. 
6. Increase of supplementary arch perimeter to accommodate teeth in patients with tooth 
size – arch size dicrepancies. 
Medical Indications -Gray and BrogansGray and Brogans
• Poor Nasal airway 
•  Septal Deformity 
•  Recurrent ear, nasal (or) sinus infections
• Asthma 
R.M.E and Nasal Airway Resistance 
 RME causes a relative reduction in the nasal airway resistance by disarticulating the 
maxilla from other bone particularly Septal and palatine bone 
 • Nilnimmar et al 1980
 Reduction Of Nasal Airway Resistance 
The extent of which RME will change the mode of respiration is complex owing to wide variations 
in both NAR (nasal airway resistance) reduction and the point at which an individual subject 
will switch from nasal to oronasal breathing.
•  Study by DaleDale -R-Recommendation of RME for purely respiratory reasons can not be advocated 
on a risk/benefit 
Contra - Indications:
Absolute:
1. Single tooth cross bites.
2. In patients who are un co-operative.
3. Skeletal asymmetry of maxilla & mandible & Adult cases with severe
antero posterior skeletal discrepancies.
4. Vertical growers with steep mandibular plane angle.
5. Anterior open bite.
Relative:
1. Patent mid-palatal suture. 2. Normal buccal occlusion.
Source: JCO, Volume 1968 Feb(67 - 70):
A Hygienic Appliance For Rapid Expansion - WILLIAM BIEDERMAN, D
• Rapid palatal expansion as re-introduced by Haas, is a significant advance in maxillary
orthopedics.
• It opens the mid-palatal suture and widens the apical base, thus negating the
conclusion of Lundstrom that the apical base is unchangeable.
• This type of appliance makes use of a special screw called HYRAX (Hygenic Rapid
Expander).
• The Hyrax Expander is essentially a nonspring loaded jackscrew
with an all wire frame.
• The screws have heavy gauge wire extensions that are adapted to follow the
palatal contours and soldered to bands on premolar and molar.
• The main advantage of this expander is that it does not irritate the palatal mucosa
and is easy to keep clean.
• It is capable of providing sutural separation of 11 mm within a very short period of
wear and a maximum of 13 mm can also be achieved.
• Each activation of the screw produces approximately 0.2 mm of lateral expansion
and it is activated from front to back.
HAASHAAS.1961
•The rapid palatal expander as described by Haas is a
rigid appliance designed for maximum dental anchorage
that uses a jackscrew to produce expansion in 10 to 14
days.
•He believed that this will maximize the orthopedic
effects and forces produced by this appliance have been
reported in the range of 3 to 10 pounds.
•States that more bodily movement and less tipping is
produced when acrylic palatal coverage is added to
support the appliance
Haas AJ. The treatment of
maxillary deficiency by opening
the
midpalatal suture. Angle Orthod
1965;35:200-17.
BONDED RAPID PALATAL EXPANDER
• The Bonded RPE were first described by Cohen and Silverman in 1973 .
• It is similar to the banded version with the exception of the method of attachment to the
teeth.
• This appliance is constructed with an acrylic cap over the posterior segments, which is
then bonded directly to the teeth.
• The bonded appliance has become increasingly popular because of its advantages:
It can be easily cemented during the mixed dentition stage, when retention
from other appliances can be poor.
Number of appointments are reduced.
There is reduced posterior teeth tipping and extrusion.
• The buccal capping limits molar extrusion during treatment and,
therefore improves the vertical control,which is particularly useful in
class II conditions, as molar extrusion would cause autorotation of
the mandible backward and downward resulting in increase in facial
convexity and the vertical dimension of the lower face.
• It provides Bite block effect to facilitate the correction of anterior
crossbite (McNamara)
Sarver. Skeletal changes in vertical anterior displacement of
maxilla with bonded rapid palatal expander appliances.
Am J Orthod Dentofacial Orthop 1989;462-66.
BONDED HYRAX
• Several methods have been developed for
RME,such as the bonded Hyrax developed
by McNamara and Brudon(a Hyrax with an
acrylic splint bonded to the occlusal surface
of posterior teeth) to minimize the vertical
effects of conventional expansion appliances
DESCRIPTION OF A TYPICAL EXPANSION SCREWS:-DESCRIPTION OF A TYPICAL EXPANSION SCREWS:-
• Atypical expansion screw consists of body divided into two
halves.
• Each half has threaded inner side that receives one end of a
double ended screw.
• The screw has central bossing with four holes which receives a
key used to turn the screw.
• The pitch of the screw is the extent to which the two halves of the
base plate moves, for each full turn of about the expansion screw,
normally it is about 0.8mm.
ACTIVATION SCHEDULE:-
• The basic principle of the appliance involves the
generation of forces that are capable of splitting the
mid-palatine suture.
• The forces are generated are close to 10 to 20 pounds
an expansion of 0.2 to 0.8mm should be achieved per
day.
• The screw is activated between 0.4 to 1mm per day
and about 1cm of expansion can be expected in 2 to 3
weeks.
The activation schedule tends to vary depending on the age of patient and form of
appliance.
• SCHEDULE BY TIMMS:-SCHEDULE BY TIMMS:-
For patients up to 15 yrs of age, 90* rotation in the morning and evening.
For patients over 15 yrs of age, 45* activation 4 times a day.
• SCHEDULE BY ZIMRING AND ISAACSON:-SCHEDULE BY ZIMRING AND ISAACSON:-
In young growing patients, 2 turns each day for 4-5 days and later 1 turn
per day and in non growing adults 2 turns for 1st
2days and 1 turn per day
for 5-7 days and 1turn every alternate days till the desired expansion is
achieved.
EXPANSION SCREW
KEY USED FOR ACTIVATION
SAME- INDICATIONS FOR SAME
• Brown first described SAME in 1938performly only a midpalatal osteotomy
• Surgically-assisted maxillary expansion can be considered as part of the overall treatment
plan for a mature patient with a constricted maxillary arch for the following.
1.To widen the arch and to correct a posterior crossbit .
2. Necessity for a large amount (>7mm) of expansion, or preference to avoid the potential
increased risk of segmental osteotomies
3. To widen the arch following maxillary collapse associated with a cleft palate
4. Extremely thin, delicate gingival tissue or presence of significant buccal gingival
recession in the caninebicuspid region of the maxilla;
5. significant nasal stenosis
Technique of SAME
• A rigid expansion appliance is usually cemented
to the first premolars and first molars on each side,
but it may also be attached only to the first molars
• The appliance is placed in the mouth a few days before
surgery to allow the patient to accommodate to it.
•Incision made in the depth of the maxillary vestibule from the region of the first molar on one
side to the midline
• The soft tissues are reflected subperiosteally from the lateral aspect of the maxilla, with
dissection to expose the anterior floor of the nose and piriform aperture area, posteriorly to the
pterygomaxillary fissure
•Incision made in the depth of the maxillary vestibule from the region of the first molar on one
side to the midline
• The soft tissues are reflected subperiosteally from the lateral aspect of the maxilla, with
dissection to expose the anterior floor of the nose and piriform aperture area, posteriorly to the
pterygomaxillary fissure
The level of the lateral maxillary osteotomy is
measured to be at least 5 mm above the apices
of the teeth.
• As the anterior portion of the osteotomy is
being performed, a periosteal elevator is
maintained in the piriform rim, lifting the nasal
mucoperiosteum to protect it.
•The lateral wall osteotomy is extended
posteriorly to the pterygo-maxillary fissure.
• This osteotomy cut is designed with a step, as
for a complete maxillary osteotomy
hygenic rapid maxillary expansion in orthodontics
In summary, the SAME technique has the following advantages when
compared with segmented surgical expansion.
1 ) The maxillary arch can be expanded orthopaedically, either unilaterally or bilaterally,
in a mature patient with minimal morbidity.
2) In orthognathic cases, this technique allows the orthodontist to create an ideal
maxillary arch-form which, in turn, simplifies the subsequent orthognathic surgery, even
if the maxilla still needs to be moved in either or both the vertical or the horizontal
planes.
3) The technique minimizes the risks of avascular necrosis and difficulties in positioning
and stabilizing segments, both of which may be associated with segmented maxillary
osteotomies.
Implant-supported expansion
Bone screw-force can be applied directly to maxilla
Jack screw
TREATMENT EVALUATION DURING RME:-TREATMENT EVALUATION DURING RME:-
• Most noticeable feature during RME is appearance of
midline diastema.
• The amount of incisor expansion is roughly half the
amount of jack screw separation.
• Maxillary occlusal radiograph and P.A cephalogram
are more reliable in estimating the amount of maxillary
expansion.
36
BIOLOGIC RESPONSE OF MID-PALATAL SUTURE TO MAXILLARY
EXPANSION
Ten Cate et al studied the biologic response of midpalatal suture to maxillary
expansion. The immediate effect of applying force to the suture results in trauma.
Small, localized tears occurred within the suture from the localized blood vessels.
These small defects were filled with exudate, a few extravasated red blood cells,
scattered filaments of fibrin, and a few fine collagen fibrils.
A transient polymorph response was noted in the region of the defects in the first
12 hours and thereafter was not seen again. Following the polymorph response, an
influx of macrophages and pioneer fibroblasts into the defect occurred by 24
hours.
37
•The pioneer fibroblasts were characterized by long, slender processes
forming a delicate reticulum throughout the defect. Intracellular collagen
profiles were occasionally found within the pioneer fibroblasts.
•Within 3 to 4 days, bone formation had begun at the margins of the suture
achieved by the pre-existing and undamaged osteoblasts. These formed
successive lamellae along the suture margin. In the following time period
(approximately 1 to 2 weeks), during which the force applied to the suture was
progressively decreasing, the fine structural appearance of the suture was one
of overwhelming fibrogenesis and osteogenesis. No evidence of fibroclasia
could be detected during this period.
38
•The collagen fibers and cells were aligned transversely across the suture
corresponding to levels of tension. New bone formation now occurred along the
same axis as trabeculae formed at right angles to the lamellae deposited initially at
the suture margins.
•With diminution and cessation of the expansion force (2 to 3 weeks), remodeling
of both the bone and the suture occurred by the osteocytic and fibrocytic cell
series until normal sutural dimensions were achived.
•During the entire period of expansion, the uniting layers remained intact. The
constituent fibroblasts showed a marked hypertrophy, indicative of increased
synthetic activity, but evidence of fibroclasia was not seen.
Effect of RME on Maxillary and Mandibular ComplexEffect of RME on Maxillary and Mandibular Complex
Maxillary skeletal effect:
• When viewed occlusally, Inoue found that the opening of the midpalatine suture was
nonparallel and triangular with maximum opening at incisor region and gradually
diminishing towards the posterior part of palate.
• Viewed frontally, the maxillary suture separates superoinferiorly in a nonparallel
manner.
• It is pyramidal in shape with the base of pyramid located at the oral side of the bone.
Samir E Bishara. Maxillary expansion: Clinical implication, AJO-DO 1997;1:3-14.
Maxillary halves:
• Haas and Wertz found the maxilla to be frequently displaced downward and forward.
Palatal vault:
Haas reported that the palatine process of maxilla was lowered as a result of outward tilting of maxillary
halves.
Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the
midpalatal suture. Angle Orthod 1961;31:73-90. 19.
Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture
opening. AM J ORTHOD 1970;58:41-66.
Alveolar process:
Because bone is resilient, lateral bending of the alveolar processes occurs early during RME, which
rebounds back after a few days.
Isaacson RJ, Wood JL, Ingram AH. Forces produced by rapid
maxillary expansion. Angle Orthod 1964;34:256-70.
Maxillary anterior teethMaxillary anterior teeth
• From the patient’s point of view, one of the most spectacular changes accompanying
RME is the opening of a diastema between the maxillary central incisors.
• It is estimated that during active suture opening, the incisors separate approximately half
the distance the expansion screw has been opened,but the amount of separation between
the central incisors should not be used as an indication of the amount of suture separation.
• This distema is self-corrective due to elastic recoil of the transseptal fibers
Wertz RA. Skeletal and dental changes accompanying rapid
midpalatal suture opening. AM J ORTHOD 1970;58:41-66.
Maxillary posterior teeth
• There is buccal tipping and extrusion of the maxillary molars.
• The posterior maxilla expands less readily because of the resistance produced by the zygomatic
buttress and pterygoid plates.
RME and nasal airflowRME and nasal airflow
• Anatomically, there is an increase in the width of the nasal cavity immediately following expansion
thereby improves in breathing. The nasal cavity width gain averages of 1.9 mm, but can be as wide as
8 to 10 mm
Gray LP. Results of 310 cases of rapid maxillary expansion selected for medical reasons.
J Laryngol Otol 1975;89:601- 14.
Important for the clinician to remember that the main resistance to
midpalatal suture opening is probably not the suture itself, but in the
surrounding structures particularly the sphenoid and zygomatic bones.
Relation between amount of sutural separation and extent of
molar expansion
Krebs
• studied maxillary expansion with metallic implants.
• He placed implants in the alveolar process lingual to the upper canines and along the
infrazygomatic ridge, buccal to the upper first molars.
• He found that the mean increase in
intermolar distance measured on casts was 66 mm,
infrazygomatic ridge implants was 3.73.7 mm. •
• In 20 of 23 patients examined, the amount of sutural opening was equal to or less than
one half the amount of dental arch expansion.
• He also found that the sutural opening was on average more than twice as large between
the incisors than it was between the molars.
• Changes during fixation and retention. Krebs noted that although
dental arch width was maintained during fixed retention, the
distance between implants in the infrazygomatic ridges decreased
during the 3 months of fixed retention by an average of 10% to
15%.
• This relapse continued during retention with removable
appliances. After an average period of 15 months, approximately
70% of the infrazygomatic maxillary width increase was
maintained
Palatal mucoperiosteum, periodontal tissues, and root
resorption
• Cotton suggested that the postexpansion angular changes of the
maxillary first molars may be related to the stretched fibers of the
attached palatal mucosa.
• Maguerza and Shapiro attempted to relieve the stretch of the
mucoperiosteum after "slow" expansion by making incisions along the
palate down to the cortical bone, 3 mm away from the teeth.
• The incisions did not effectively reduce the relapse tendency.
• Whether such incisions might be effective with RME expansion or
whether the incision wound itself causes contraction is yet to be
determined
Effects of RME on adjacent facial structures
• Kudlick, in a study on a human dry skull that simulated in vivo
response of RME, concluded the following:
(1) All craniofacial bones directly articulating with the maxilla were
displaced except the sphenoid bone
(2) The cranial base angle remained constant
(3) Displacement of the maxillary halves was asymmetric
(4) The sphenoid bone, not the zygomatic arch, was the main
buttress against maxillary expansion
47
RME IN ADDITION OF ARCH LENGTH
• McNamara used the transpalatal width of the patient measured between
the upper molars, as a diagnostic guide to determine whether the patient
might be a candidate for rapid maxillary expansion to correct a transverse
arch-length discrepancy.
•A transpalatal width of 35-39mm is considered ideal for an adult and 33-
34mm for a mixed dentition. Any discrepancy in this measurement
indicates palatal expansion.
Adkins and Nanda (AJO1990) estimate that every 1mm of increase in
posterior arch width produced by RME translates to 0.7mm of
increased arch perimeter. This additional arch length may lead to an
overall reduction in the patient undergoing extraction of permanent
teeth due to tooth-size arch-size problems.
EFFECTS OF AGE & R.M.E
• Growth Ceases first In Transverse dimension
• Growth at the midpalatal suture was thought to cease at the age of 3 years.
• By means of implants, Bjork and Skiellent found that growth at the suture
might be occurring as late as 13 years of age
Wertz
• He divided his sample into 3 age groups:
• under 12, 12 to 18, and over 18 years.
• He found that after expansion and during fixed retention there was little relapse in any of
the three groups (-0.5, -0.6 and 0.5mm, respectively).
• On the other hand, each age group behaved differently from the time of appliance
removal to the end of retention.
• The group under 12 years of age had a further increase of approximately 10%, and the
over 18 years group had a relapse of approximately 63%.
• The optimal age for expansion is, therefore, before 13 to 15 years of age.
HOW MUCH TO EXPAND
• Studies by Kerbs (1964) Stockfisch (1976) and Linder Aronson et al
(1979) show that between one third to one half of the expansion was lost
before stability eventually was reached.
• Out of one thousand patients who were treated by RME there were only
two in whom no relapse occurred, and the extent of this relapse is largely
unpredictable.
• A general guide line about how much to expand
maxillary palatal cusps are level with the buccal cusps of the
mandibular teeth.
• Stalley Rn Peterson Lc (1985)
• Measure the distance between the most gingival
extension of the buccal grooves on the mandibular
first molars or, when the grooves have no distinct
terminus on the buccal surface, between points on the
grooves located at the middle of the buccal surfaces.
• Measure the distance between the tips of the
mesiobuccal cusps of the maxillary 1st molars.
Subtract the mandibular measurement from the
maxillary measurement
• The average differences in Persons with normal
occlusion are 1.6mm for males and 1.2mm for
females
METHOD OF RETENTION AND RELAPSE TENDENCIES
• The aim of retention is to hold the expansion while all the forces generated by
expansion appliance is removed.
• Hicks observed that the amount of relapse is related to the method of retention
after expansion.
• He observed with no retention, the relapse can amount to 45%, as compared with
10% to 23% with fixed retention and 22% to 25% with removable retention.
• Bell concluded that slow expansion is less disruptive to the sutural systems.
• Slow expansion that maintained tissue integrity apparently needs 1 to 3 months of
retention, which is significantly shorter than the 3 to 6 months recommended for
rapid expansion, Mew advocates a total retention period of 1 ½ to 4 years
depending on the extent of expansion.
• Postpone extraction of 1st premolars until palatal expansion is
completed because these teeth, together with the 1st molars are
often used as abutment teeth for anchoring the appliance.
• If premolars have not erupted, second deciduous molars with
adequate root structure can be used.
• However suggested a bonded appliance that would incorporate
deciduous teeth. When possible avoid orthodontic movement of
the maxillary posterior teeth prior to RME.
• Mobile teeth may tip faster during expansion.
• The vertical positioning of the expansion screw is a function of
the width of the palate and the size of the screw
• For patients comfort and for mechanical advantage, position the screws as
superiorly as possible in the palatal vault.
• inserted to allow sufficient setting time for cementing medium. Each turn of
the screw open the appliance 1/4mm.
• Provide the patient with an instruction sheet listing the turn schedule and
possible symptoms that might accompany RME.
• See the patient at regular – intervals during the expansion phase of treatment,
measure the distance between the two halves of the expansion screw to
determine how much the screw has been turned.
• Monitor the midpalatal suture with weekly maxillary occlusal films.
• The suture will open within 7 to 10 days in most patients.
• If the suture does not split within 2 weeks, the lack of the skeletal response may
result in tipping of the teeth and possible fracture of alveolar plates.
• After the expansion is completed and the screw is immobilized, the appliance acts
as a fixed retainer for a period of 3 to 6 months to allow the tissues to reorganize in
their new positions and also allow the forces created by the expanding appliance to
dissipate.
• The greater the magnitude of expansion, the longer the period of fixed retention
• After removing the RME appliance, place a transpalatal arch between the
maxillary first molars to minimize relapse tendencies
• At the end of the expansion stage and during fixation the maxillary posterior
segment are usually over expanded.
• During the orthodontic treatment phase incorporate some expansion in maxillary
arch wire to avoid lingual crown torque of the maxillary molars and/or buccal
crown torque of the mandibular molars because such forces may reintroduce the
crossbite problem
hygenic rapid maxillary expansion in orthodontics
Meta analysis of immediate changes with RME treatment
JADA Jan 2006
Results: Of the 31 selected abstracts, 12 were rejected b coz they
failed to report immediate changes after the activation phase of
RME and instead reported changes only after the retention phase.
• The greatest changes were in the maxillary transverse plane in
which the width gained was caused more by dental expansion
than true skeletal expansion. Few vertical and anteroposterior
changes were statistically significant, and none was clinically
significant.
Am J Orthod Dentofacial Orthop. 2015 Jul;148(1):97-109.
Periodontal, dentoalveolar, and skeletal effects of tooth-borne and tooth-
bone-borne expansion appliances.
Gunyuz Toklu M, Germec-Cakan D, Tozlu M.
• Both tooth-borne and tooth-bone-borne rapid expansion are
effective methods for treating a narrow maxilla.
• However, the hyrax appliance resulted in greater expansion in the
premolar region.
• On the other hand, the hybrid hyrax appliance did not cause
changes in the bony support of the first premolars.
Methods: Treatment of 16 children (mean age 9.5 ± 1.3 years)
was investigated clinically and by means of pre- and post-
treatment cephalograms. Changes in sagittal and vertical, and
dental and skeletal values were evaluated and tested for
statistically significant differences
Results: All mini-implants remained stable during treatment.
Mean treatment duration was 5.8 ± 1.7 months.
There was a significant improvement in skeletal sagittal values:
SNA, +2.0°; SNB, −1.2°; ANB, +3.2°; WITS appraisal, +4.1 mm
and overjet, +2.7 mm. No significant changes were found
concerning vertical skeletal relationships and upper incisor
inclination. In relation to A point, the upper first molars moved
mesially about 0.4 mm (P = 0.134).
hygenic rapid maxillary expansion in orthodontics
Master’s Thesis, U. Mich, 1998 Ralph, S.W., “A comparison of two rapid maxillary
expansion appliances using three-dimensional finite element analysis,”
1) The average tipping effect was 2.5-3 times greater with Hyrax than with Haas
2) The Haas displaces teeth 26% more than the Hyrax in the transverse
dimension
3) Larger sutural displacement occurred with the Haas appliance.
4) The Hyrax deformed more than the Haas, resulting in less energy affecting the
CONCLUSION
• Expansion of the maxilla and the maxillary dentition may be
accomplished in numerous ways.
• The type of skeletal and dental pattern greatly influences the type of
expansion chosen and the type of expansion selected can greatly
facilitate the overall treatment objectives.

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hygenic rapid maxillary expansion in orthodontics

  • 3. • Early 1900’s are know as the “maxillary expansion years” • At this stage in orthodontic history numerous articles pointing to the interrelations of  orthodontics and Rhinologic treatment procedures appeared in the literature .  • G.V.I Brown a noted rhinologist was one of vociferous proponents of suture opening  for purpose of increasing nasal permeability • Lundstrom and later Brodie and associates also challanged the expansion . 
  • 5. INTRODUCTION  •  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.
  • 7. • Orthodontic ExpansionOrthodontic Expansion:                 It is well known that expansion of the dental arches can be produced by a                                                                      variety of orthodontic treatments, including those that employ fixed  appliances. • Passive ExpansionPassive Expansion When the occlusion is shielded from the forces of the buccal and labial musculature, a  widening of the dental arches often occurs.               This expansion is not produced through the application of extrinsic biomechanical                                                          forces, but rather by intrinsic forces such as those produced by the tongue. •  ExampleExample as passive expansion are the dimensional changes in the dental arches produced                                                                   by such vestibular shield appliances as the FR-2 of Frankel.
  • 9. CLASSIFICATION •  According to the rate  a) rapid  b) slow  • According to type of expansion  a) orthodontic  b) orthopedic  c) passive • According to direction  a) anterior  b) posterior  c) unilateral  d) bilateral  e) 3-dimensional • According to type of appliance         a) removable          b) fixed -- banded or bonded  1.Tooth borne e.g. HYRAX , Issacson 2. Tooth and tissue borne e.g Hass • According to the jaw            maxillary e.g Transpalatal arch,HYRAX           mandibular e.g. Active lingual arch •According to the active element                      Screws                Dental expansion e.g Sectional  screw ,                                           Traction  screw                 Skeletal e.g HYRAX
  • 10. Applied Anatomy: •  Each maxilla has a body and zygomatic, frontal, alveolar and palatine process. • Body of the maxilla articulates with the following bones  •  Cranially - 1) Frontal, 2) Ethmoid • Facially :-1) Nasal, 2) Lacrimal, 3) Inferior nasal conchae, 4) Vomer, 5) Zygomatic  and Palatine  • Most of these bones bind the maxilla posteriorly and superiorly by sutural joints  leaving the anterior and inferior aspect free   In theory this suture is formed by the junction of the three opposing pairs of bones namely premaxillae, maxillae and the palatine but often for practical purposes they will be treated as single entity called as a Midpalatal suture.Midpalatal suture.
  • 11. • The morphology of the mid palatal suture has been studied by MELSEN (1975).  •  Stages of development used by Bjork and Helm   First stage :  • Covering the infantile period.  • The suture is very broad and Y shaped with the vomerine bone placed in a V shaped                  groove  between the two halves of the maxilla.  Second stage : Juvenile period, the suture is found to be more wavy.  Third stage : Adolescent period, the suture is characterized by a more tortuous course with increasing  inter digitations. Infancy - Y-shape Juvenile - T-shape Adolescence - Jigsaw puzzle Two yrs of age  9yrs of age  13yrs of age
  • 12. ETIOLOGY • The causes of buccolingual discrepancies could be either genetic or  environmental. •  According to Graber, and Harvold, Cheirici and Vargervi many  constricted maxillary dental arches are the result of abnormal function.  •  Harvold in his experimental work created narrow maxillary dental arches  in rhesus monkeys by converting them from nasal to obligatory oral  respiration. •  All patients considered for RME should be examined for nasal  obstruction and, if obstruction is found, they should be referred to an  otolaryngologist before orthodontic treatment
  • 14. Diagnostic aidsDiagnostic aids • While Considering RME for young adults, occlusal radiographs can be used for  analysing the palatal suture status.               A radiologically visible midpalatal suture corresponds histologically to a  predominantly straight running oronasal suture, which projects largely into the  saggital X – ray path.  • Only small areas of interdigitation, if any are to be expected and the percentage of  suture obliteration is low.  2. Radiological invisible suture corresponds histologically to a relatively large area of  interdigitation, an oblique running suture course in relation to X ray path or bone  structures projecting above the suture course. •  Percentage of suture obliteration to be expected is also low in this group.
  • 15. Indications for RME Dental indications 1. Posterior Cross bite (unilateral/bilateral) 2.  Elimination of inter arch transverse discrepancies prior to orthopedic intervention in  class II malocclusions  3. Activation of the circummaxillary sutural system in treatment protocols / Class III  4. Cleft palate patients with collapsed maxillary arch.  5. In cases requiring face mask therapy.  6. Increase of supplementary arch perimeter to accommodate teeth in patients with tooth  size – arch size dicrepancies. 
  • 16. Medical Indications -Gray and BrogansGray and Brogans • Poor Nasal airway  •  Septal Deformity  •  Recurrent ear, nasal (or) sinus infections • Asthma  R.M.E and Nasal Airway Resistance   RME causes a relative reduction in the nasal airway resistance by disarticulating the  maxilla from other bone particularly Septal and palatine bone   • Nilnimmar et al 1980  Reduction Of Nasal Airway Resistance  The extent of which RME will change the mode of respiration is complex owing to wide variations  in both NAR (nasal airway resistance) reduction and the point at which an individual subject  will switch from nasal to oronasal breathing. •  Study by DaleDale -R-Recommendation of RME for purely respiratory reasons can not be advocated  on a risk/benefit 
  • 17. Contra - Indications: Absolute: 1. Single tooth cross bites. 2. In patients who are un co-operative. 3. Skeletal asymmetry of maxilla & mandible & Adult cases with severe antero posterior skeletal discrepancies. 4. Vertical growers with steep mandibular plane angle. 5. Anterior open bite. Relative: 1. Patent mid-palatal suture. 2. Normal buccal occlusion.
  • 18. Source: JCO, Volume 1968 Feb(67 - 70): A Hygienic Appliance For Rapid Expansion - WILLIAM BIEDERMAN, D • Rapid palatal expansion as re-introduced by Haas, is a significant advance in maxillary orthopedics. • It opens the mid-palatal suture and widens the apical base, thus negating the conclusion of Lundstrom that the apical base is unchangeable. • This type of appliance makes use of a special screw called HYRAX (Hygenic Rapid Expander). • The Hyrax Expander is essentially a nonspring loaded jackscrew with an all wire frame.
  • 19. • The screws have heavy gauge wire extensions that are adapted to follow the palatal contours and soldered to bands on premolar and molar. • The main advantage of this expander is that it does not irritate the palatal mucosa and is easy to keep clean. • It is capable of providing sutural separation of 11 mm within a very short period of wear and a maximum of 13 mm can also be achieved. • Each activation of the screw produces approximately 0.2 mm of lateral expansion and it is activated from front to back.
  • 20. HAASHAAS.1961 •The rapid palatal expander as described by Haas is a rigid appliance designed for maximum dental anchorage that uses a jackscrew to produce expansion in 10 to 14 days. •He believed that this will maximize the orthopedic effects and forces produced by this appliance have been reported in the range of 3 to 10 pounds. •States that more bodily movement and less tipping is produced when acrylic palatal coverage is added to support the appliance Haas AJ. The treatment of maxillary deficiency by opening the midpalatal suture. Angle Orthod 1965;35:200-17.
  • 21. BONDED RAPID PALATAL EXPANDER • The Bonded RPE were first described by Cohen and Silverman in 1973 . • It is similar to the banded version with the exception of the method of attachment to the teeth. • This appliance is constructed with an acrylic cap over the posterior segments, which is then bonded directly to the teeth. • The bonded appliance has become increasingly popular because of its advantages: It can be easily cemented during the mixed dentition stage, when retention from other appliances can be poor. Number of appointments are reduced. There is reduced posterior teeth tipping and extrusion.
  • 22. • The buccal capping limits molar extrusion during treatment and, therefore improves the vertical control,which is particularly useful in class II conditions, as molar extrusion would cause autorotation of the mandible backward and downward resulting in increase in facial convexity and the vertical dimension of the lower face. • It provides Bite block effect to facilitate the correction of anterior crossbite (McNamara) Sarver. Skeletal changes in vertical anterior displacement of maxilla with bonded rapid palatal expander appliances. Am J Orthod Dentofacial Orthop 1989;462-66.
  • 23. BONDED HYRAX • Several methods have been developed for RME,such as the bonded Hyrax developed by McNamara and Brudon(a Hyrax with an acrylic splint bonded to the occlusal surface of posterior teeth) to minimize the vertical effects of conventional expansion appliances
  • 24. DESCRIPTION OF A TYPICAL EXPANSION SCREWS:-DESCRIPTION OF A TYPICAL EXPANSION SCREWS:- • Atypical expansion screw consists of body divided into two halves. • Each half has threaded inner side that receives one end of a double ended screw. • The screw has central bossing with four holes which receives a key used to turn the screw. • The pitch of the screw is the extent to which the two halves of the base plate moves, for each full turn of about the expansion screw, normally it is about 0.8mm.
  • 25. ACTIVATION SCHEDULE:- • The basic principle of the appliance involves the generation of forces that are capable of splitting the mid-palatine suture. • The forces are generated are close to 10 to 20 pounds an expansion of 0.2 to 0.8mm should be achieved per day. • The screw is activated between 0.4 to 1mm per day and about 1cm of expansion can be expected in 2 to 3 weeks.
  • 26. The activation schedule tends to vary depending on the age of patient and form of appliance. • SCHEDULE BY TIMMS:-SCHEDULE BY TIMMS:- For patients up to 15 yrs of age, 90* rotation in the morning and evening. For patients over 15 yrs of age, 45* activation 4 times a day. • SCHEDULE BY ZIMRING AND ISAACSON:-SCHEDULE BY ZIMRING AND ISAACSON:- In young growing patients, 2 turns each day for 4-5 days and later 1 turn per day and in non growing adults 2 turns for 1st 2days and 1 turn per day for 5-7 days and 1turn every alternate days till the desired expansion is achieved.
  • 27. EXPANSION SCREW KEY USED FOR ACTIVATION
  • 28. SAME- INDICATIONS FOR SAME • Brown first described SAME in 1938performly only a midpalatal osteotomy • Surgically-assisted maxillary expansion can be considered as part of the overall treatment plan for a mature patient with a constricted maxillary arch for the following. 1.To widen the arch and to correct a posterior crossbit . 2. Necessity for a large amount (>7mm) of expansion, or preference to avoid the potential increased risk of segmental osteotomies 3. To widen the arch following maxillary collapse associated with a cleft palate 4. Extremely thin, delicate gingival tissue or presence of significant buccal gingival recession in the caninebicuspid region of the maxilla; 5. significant nasal stenosis
  • 29. Technique of SAME • A rigid expansion appliance is usually cemented to the first premolars and first molars on each side, but it may also be attached only to the first molars • The appliance is placed in the mouth a few days before surgery to allow the patient to accommodate to it.
  • 30. •Incision made in the depth of the maxillary vestibule from the region of the first molar on one side to the midline • The soft tissues are reflected subperiosteally from the lateral aspect of the maxilla, with dissection to expose the anterior floor of the nose and piriform aperture area, posteriorly to the pterygomaxillary fissure •Incision made in the depth of the maxillary vestibule from the region of the first molar on one side to the midline • The soft tissues are reflected subperiosteally from the lateral aspect of the maxilla, with dissection to expose the anterior floor of the nose and piriform aperture area, posteriorly to the pterygomaxillary fissure
  • 31. The level of the lateral maxillary osteotomy is measured to be at least 5 mm above the apices of the teeth. • As the anterior portion of the osteotomy is being performed, a periosteal elevator is maintained in the piriform rim, lifting the nasal mucoperiosteum to protect it. •The lateral wall osteotomy is extended posteriorly to the pterygo-maxillary fissure. • This osteotomy cut is designed with a step, as for a complete maxillary osteotomy
  • 33. In summary, the SAME technique has the following advantages when compared with segmented surgical expansion. 1 ) The maxillary arch can be expanded orthopaedically, either unilaterally or bilaterally, in a mature patient with minimal morbidity. 2) In orthognathic cases, this technique allows the orthodontist to create an ideal maxillary arch-form which, in turn, simplifies the subsequent orthognathic surgery, even if the maxilla still needs to be moved in either or both the vertical or the horizontal planes. 3) The technique minimizes the risks of avascular necrosis and difficulties in positioning and stabilizing segments, both of which may be associated with segmented maxillary osteotomies.
  • 34. Implant-supported expansion Bone screw-force can be applied directly to maxilla Jack screw
  • 35. TREATMENT EVALUATION DURING RME:-TREATMENT EVALUATION DURING RME:- • Most noticeable feature during RME is appearance of midline diastema. • The amount of incisor expansion is roughly half the amount of jack screw separation. • Maxillary occlusal radiograph and P.A cephalogram are more reliable in estimating the amount of maxillary expansion.
  • 36. 36 BIOLOGIC RESPONSE OF MID-PALATAL SUTURE TO MAXILLARY EXPANSION Ten Cate et al studied the biologic response of midpalatal suture to maxillary expansion. The immediate effect of applying force to the suture results in trauma. Small, localized tears occurred within the suture from the localized blood vessels. These small defects were filled with exudate, a few extravasated red blood cells, scattered filaments of fibrin, and a few fine collagen fibrils. A transient polymorph response was noted in the region of the defects in the first 12 hours and thereafter was not seen again. Following the polymorph response, an influx of macrophages and pioneer fibroblasts into the defect occurred by 24 hours.
  • 37. 37 •The pioneer fibroblasts were characterized by long, slender processes forming a delicate reticulum throughout the defect. Intracellular collagen profiles were occasionally found within the pioneer fibroblasts. •Within 3 to 4 days, bone formation had begun at the margins of the suture achieved by the pre-existing and undamaged osteoblasts. These formed successive lamellae along the suture margin. In the following time period (approximately 1 to 2 weeks), during which the force applied to the suture was progressively decreasing, the fine structural appearance of the suture was one of overwhelming fibrogenesis and osteogenesis. No evidence of fibroclasia could be detected during this period.
  • 38. 38 •The collagen fibers and cells were aligned transversely across the suture corresponding to levels of tension. New bone formation now occurred along the same axis as trabeculae formed at right angles to the lamellae deposited initially at the suture margins. •With diminution and cessation of the expansion force (2 to 3 weeks), remodeling of both the bone and the suture occurred by the osteocytic and fibrocytic cell series until normal sutural dimensions were achived. •During the entire period of expansion, the uniting layers remained intact. The constituent fibroblasts showed a marked hypertrophy, indicative of increased synthetic activity, but evidence of fibroclasia was not seen.
  • 39. Effect of RME on Maxillary and Mandibular ComplexEffect of RME on Maxillary and Mandibular Complex Maxillary skeletal effect: • When viewed occlusally, Inoue found that the opening of the midpalatine suture was nonparallel and triangular with maximum opening at incisor region and gradually diminishing towards the posterior part of palate. • Viewed frontally, the maxillary suture separates superoinferiorly in a nonparallel manner. • It is pyramidal in shape with the base of pyramid located at the oral side of the bone. Samir E Bishara. Maxillary expansion: Clinical implication, AJO-DO 1997;1:3-14.
  • 40. Maxillary halves: • Haas and Wertz found the maxilla to be frequently displaced downward and forward. Palatal vault: Haas reported that the palatine process of maxilla was lowered as a result of outward tilting of maxillary halves. Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the midpalatal suture. Angle Orthod 1961;31:73-90. 19. Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. AM J ORTHOD 1970;58:41-66. Alveolar process: Because bone is resilient, lateral bending of the alveolar processes occurs early during RME, which rebounds back after a few days. Isaacson RJ, Wood JL, Ingram AH. Forces produced by rapid maxillary expansion. Angle Orthod 1964;34:256-70.
  • 41. Maxillary anterior teethMaxillary anterior teeth • From the patient’s point of view, one of the most spectacular changes accompanying RME is the opening of a diastema between the maxillary central incisors. • It is estimated that during active suture opening, the incisors separate approximately half the distance the expansion screw has been opened,but the amount of separation between the central incisors should not be used as an indication of the amount of suture separation. • This distema is self-corrective due to elastic recoil of the transseptal fibers Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. AM J ORTHOD 1970;58:41-66.
  • 42. Maxillary posterior teeth • There is buccal tipping and extrusion of the maxillary molars. • The posterior maxilla expands less readily because of the resistance produced by the zygomatic buttress and pterygoid plates. RME and nasal airflowRME and nasal airflow • Anatomically, there is an increase in the width of the nasal cavity immediately following expansion thereby improves in breathing. The nasal cavity width gain averages of 1.9 mm, but can be as wide as 8 to 10 mm Gray LP. Results of 310 cases of rapid maxillary expansion selected for medical reasons. J Laryngol Otol 1975;89:601- 14. Important for the clinician to remember that the main resistance to midpalatal suture opening is probably not the suture itself, but in the surrounding structures particularly the sphenoid and zygomatic bones.
  • 43. Relation between amount of sutural separation and extent of molar expansion Krebs • studied maxillary expansion with metallic implants. • He placed implants in the alveolar process lingual to the upper canines and along the infrazygomatic ridge, buccal to the upper first molars. • He found that the mean increase in intermolar distance measured on casts was 66 mm, infrazygomatic ridge implants was 3.73.7 mm. • • In 20 of 23 patients examined, the amount of sutural opening was equal to or less than one half the amount of dental arch expansion. • He also found that the sutural opening was on average more than twice as large between the incisors than it was between the molars.
  • 44. • Changes during fixation and retention. Krebs noted that although dental arch width was maintained during fixed retention, the distance between implants in the infrazygomatic ridges decreased during the 3 months of fixed retention by an average of 10% to 15%. • This relapse continued during retention with removable appliances. After an average period of 15 months, approximately 70% of the infrazygomatic maxillary width increase was maintained
  • 45. Palatal mucoperiosteum, periodontal tissues, and root resorption • Cotton suggested that the postexpansion angular changes of the maxillary first molars may be related to the stretched fibers of the attached palatal mucosa. • Maguerza and Shapiro attempted to relieve the stretch of the mucoperiosteum after "slow" expansion by making incisions along the palate down to the cortical bone, 3 mm away from the teeth. • The incisions did not effectively reduce the relapse tendency. • Whether such incisions might be effective with RME expansion or whether the incision wound itself causes contraction is yet to be determined
  • 46. Effects of RME on adjacent facial structures • Kudlick, in a study on a human dry skull that simulated in vivo response of RME, concluded the following: (1) All craniofacial bones directly articulating with the maxilla were displaced except the sphenoid bone (2) The cranial base angle remained constant (3) Displacement of the maxillary halves was asymmetric (4) The sphenoid bone, not the zygomatic arch, was the main buttress against maxillary expansion
  • 47. 47 RME IN ADDITION OF ARCH LENGTH • McNamara used the transpalatal width of the patient measured between the upper molars, as a diagnostic guide to determine whether the patient might be a candidate for rapid maxillary expansion to correct a transverse arch-length discrepancy. •A transpalatal width of 35-39mm is considered ideal for an adult and 33- 34mm for a mixed dentition. Any discrepancy in this measurement indicates palatal expansion.
  • 48. Adkins and Nanda (AJO1990) estimate that every 1mm of increase in posterior arch width produced by RME translates to 0.7mm of increased arch perimeter. This additional arch length may lead to an overall reduction in the patient undergoing extraction of permanent teeth due to tooth-size arch-size problems.
  • 49. EFFECTS OF AGE & R.M.E • Growth Ceases first In Transverse dimension • Growth at the midpalatal suture was thought to cease at the age of 3 years. • By means of implants, Bjork and Skiellent found that growth at the suture might be occurring as late as 13 years of age Wertz • He divided his sample into 3 age groups: • under 12, 12 to 18, and over 18 years. • He found that after expansion and during fixed retention there was little relapse in any of the three groups (-0.5, -0.6 and 0.5mm, respectively). • On the other hand, each age group behaved differently from the time of appliance removal to the end of retention. • The group under 12 years of age had a further increase of approximately 10%, and the over 18 years group had a relapse of approximately 63%. • The optimal age for expansion is, therefore, before 13 to 15 years of age.
  • 50. HOW MUCH TO EXPAND • Studies by Kerbs (1964) Stockfisch (1976) and Linder Aronson et al (1979) show that between one third to one half of the expansion was lost before stability eventually was reached. • Out of one thousand patients who were treated by RME there were only two in whom no relapse occurred, and the extent of this relapse is largely unpredictable. • A general guide line about how much to expand maxillary palatal cusps are level with the buccal cusps of the mandibular teeth.
  • 51. • Stalley Rn Peterson Lc (1985) • Measure the distance between the most gingival extension of the buccal grooves on the mandibular first molars or, when the grooves have no distinct terminus on the buccal surface, between points on the grooves located at the middle of the buccal surfaces. • Measure the distance between the tips of the mesiobuccal cusps of the maxillary 1st molars. Subtract the mandibular measurement from the maxillary measurement • The average differences in Persons with normal occlusion are 1.6mm for males and 1.2mm for females
  • 52. METHOD OF RETENTION AND RELAPSE TENDENCIES • The aim of retention is to hold the expansion while all the forces generated by expansion appliance is removed. • Hicks observed that the amount of relapse is related to the method of retention after expansion. • He observed with no retention, the relapse can amount to 45%, as compared with 10% to 23% with fixed retention and 22% to 25% with removable retention. • Bell concluded that slow expansion is less disruptive to the sutural systems. • Slow expansion that maintained tissue integrity apparently needs 1 to 3 months of retention, which is significantly shorter than the 3 to 6 months recommended for rapid expansion, Mew advocates a total retention period of 1 ½ to 4 years depending on the extent of expansion.
  • 53. • Postpone extraction of 1st premolars until palatal expansion is completed because these teeth, together with the 1st molars are often used as abutment teeth for anchoring the appliance. • If premolars have not erupted, second deciduous molars with adequate root structure can be used. • However suggested a bonded appliance that would incorporate deciduous teeth. When possible avoid orthodontic movement of the maxillary posterior teeth prior to RME. • Mobile teeth may tip faster during expansion. • The vertical positioning of the expansion screw is a function of the width of the palate and the size of the screw
  • 54. • For patients comfort and for mechanical advantage, position the screws as superiorly as possible in the palatal vault. • inserted to allow sufficient setting time for cementing medium. Each turn of the screw open the appliance 1/4mm. • Provide the patient with an instruction sheet listing the turn schedule and possible symptoms that might accompany RME. • See the patient at regular – intervals during the expansion phase of treatment, measure the distance between the two halves of the expansion screw to determine how much the screw has been turned.
  • 55. • Monitor the midpalatal suture with weekly maxillary occlusal films. • The suture will open within 7 to 10 days in most patients. • If the suture does not split within 2 weeks, the lack of the skeletal response may result in tipping of the teeth and possible fracture of alveolar plates. • After the expansion is completed and the screw is immobilized, the appliance acts as a fixed retainer for a period of 3 to 6 months to allow the tissues to reorganize in their new positions and also allow the forces created by the expanding appliance to dissipate. • The greater the magnitude of expansion, the longer the period of fixed retention
  • 56. • After removing the RME appliance, place a transpalatal arch between the maxillary first molars to minimize relapse tendencies • At the end of the expansion stage and during fixation the maxillary posterior segment are usually over expanded. • During the orthodontic treatment phase incorporate some expansion in maxillary arch wire to avoid lingual crown torque of the maxillary molars and/or buccal crown torque of the mandibular molars because such forces may reintroduce the crossbite problem
  • 58. Meta analysis of immediate changes with RME treatment JADA Jan 2006 Results: Of the 31 selected abstracts, 12 were rejected b coz they failed to report immediate changes after the activation phase of RME and instead reported changes only after the retention phase. • The greatest changes were in the maxillary transverse plane in which the width gained was caused more by dental expansion than true skeletal expansion. Few vertical and anteroposterior changes were statistically significant, and none was clinically significant.
  • 59. Am J Orthod Dentofacial Orthop. 2015 Jul;148(1):97-109. Periodontal, dentoalveolar, and skeletal effects of tooth-borne and tooth- bone-borne expansion appliances. Gunyuz Toklu M, Germec-Cakan D, Tozlu M. • Both tooth-borne and tooth-bone-borne rapid expansion are effective methods for treating a narrow maxilla. • However, the hyrax appliance resulted in greater expansion in the premolar region. • On the other hand, the hybrid hyrax appliance did not cause changes in the bony support of the first premolars.
  • 60. Methods: Treatment of 16 children (mean age 9.5 ± 1.3 years) was investigated clinically and by means of pre- and post- treatment cephalograms. Changes in sagittal and vertical, and dental and skeletal values were evaluated and tested for statistically significant differences Results: All mini-implants remained stable during treatment. Mean treatment duration was 5.8 ± 1.7 months. There was a significant improvement in skeletal sagittal values: SNA, +2.0°; SNB, −1.2°; ANB, +3.2°; WITS appraisal, +4.1 mm and overjet, +2.7 mm. No significant changes were found concerning vertical skeletal relationships and upper incisor inclination. In relation to A point, the upper first molars moved mesially about 0.4 mm (P = 0.134).
  • 62. Master’s Thesis, U. Mich, 1998 Ralph, S.W., “A comparison of two rapid maxillary expansion appliances using three-dimensional finite element analysis,” 1) The average tipping effect was 2.5-3 times greater with Hyrax than with Haas 2) The Haas displaces teeth 26% more than the Hyrax in the transverse dimension 3) Larger sutural displacement occurred with the Haas appliance. 4) The Hyrax deformed more than the Haas, resulting in less energy affecting the
  • 63. CONCLUSION • Expansion of the maxilla and the maxillary dentition may be accomplished in numerous ways. • The type of skeletal and dental pattern greatly influences the type of expansion chosen and the type of expansion selected can greatly facilitate the overall treatment objectives.