2. INTRODUCTION
Arch expansion is a method of gaining space.
An apparently complex yet relatively simple
procedure in orthodontics is palatal expansion.
The correction of transverse maxillary deficiency
can be an important component of an orthodontic
treatment plan.
Expansion of palate was first achieved by Emerson
C.Angell in 1860.Ever since numerous expansion
appliance have been described with varying force
levels & duration of treatment.
3. CLASSFICATION
Expansion of the dental arches can be classified
as:
1. Dento-alveolar expansion
2. Skeletal expansion
They can also be classified broadly as:
1. Slow expansion
2. Rapid expansion
5. Slow Expansion
Slow expansion has traditionally been termed as
dento-alveolar expansion ,although some skeletal
changes can be observed.
The slower expansion have also been associated
with a more physiologic adjustment to the
maxillary expansion,producing greater stability &
less relapse potential than in rapid expansion
procedures
The force generated by such procedures are 2-4
pounds.
Expanded slowly at a rate of 0.5-1mm per week.
6. Pure dento-alveolar expansion should always be
slow
Normal width of PDL is approx 0.25 mm.For
orthodontic tooth movement to take place an
expansion device should not be activated
>0.25mm at a time.
Pitch of a jackscrew is 1mm,i.e. a 360⁰ rotation
separates two halves of expansion appliance by
1mm.
Rule for slow expansion :
Two ¼th turn per week,that means 8 turns a month
7. Indication & contraindication of slow
expansion
INDICATIONS :
1. PMBAW (premolar basal arch width)>PMD
(premolar diameter)- Ashley Howe’s Analysis
2. Any age
3. PMBAW × 100 ≥ 44% = PMBAW% -Ashley
Howe’s Analysis
TTM
CONTRAINDICATIONS :
1. Buccal or labial inclination of teeth
2. Bone loss on buccal aspect of teeth
3. Mandibular inter-canine width
8. Appliance used for slow
expansion
Fixed
W arch
Quad helix
Ni-Ti arch wires
Removable
Coffin spring
Expansion screws
Functional appliances
Active
Passive
9. W arch
0.9mm stainless steel wire soldered to molar
bands
Patient cooperation not required
Preferred in deciduous and mixed dentition where
mild to moderate expansion is required
Activation : outside mouth,3mm wider than
passive width
10. Quad helix
Four helices:more flexibility
Helices in the anterior component impart
bulkiness which can be useful in preventing digit
sucking
Activaton :either inside or outside mouth,4mm
wider than passive width
Retained for 3-4 months,after overcome is
achieved
11. Ni-Ti expanders
It has capacity to rotate,upright,distalize & expand
the anterior & posterior arch with gentle
biocompatible force.
It is capable of a uniform,slow,continuous force
Depends on shape memory and super elasticity of
NiTi
Transition temperature is 84°F
Continuous force levels between 230gms to 300 gms.
Available in 8 intermolar widths; ranging from 26-47
mm
Freeze gel packs can be used to make appliance
flexible for insertion
12. Coffin spring
It is a removable appliance capable of slow
dento-alveolar expansion
The appliance consists of an omega shaped
wire of 1.25 mm thickness,placed in mid-
palatal region
Activation : the spring is activated by pulling
the two sides apart manually.It can also be
activated by using three prong pliers
13. Expansion screws
The expansion screw is a very small metallic
appliance which may be designed to move a
single tooth or a group of teeth or the skeletal
bases as required. This screw as a source of
force together with the acrylic segment of the
plate effect the teeth and the alveolar process.
Different type of screws may be used
advantageously for certain procedure during
treatment with removable appliance .
14. Functional appliances
This expansion is not produced through the
application of extrinsic bio-mechanical but
rather than by intrinsic forces in the dental
arch such as those produced by the
tongue.(passive expansion)
When the forces of the buccal and labial
musculature are
shielded from the occlusion, a widening of
the dental arches often occurs.
15. Rapid expansion
Rapid maxillary expansion is also known by the
terms rapid palatal expansion or split palate.It is
skeletal type of expansion that involves the
separation of mid-palatal suture & movement of
the maxillary shelves away from each other.
16. Indications of rapid maxillary
expansion
1. Posterior crossbite
2. Class II malocclusion
3. Cleft palate patients
4. Face mask therapy
5. Medical indications : nasal stenosis,septal
deformities,recurrent ear & nasal
infection,allergic rhinitis
17. Contraindications of R.M.E
1. Single tooth crossbites
2. Un-cooperative patients
3. After ossification of mid-palatal suture unless it
is accompanied by adjunctive surgical
procedures
4. Skeletal asymmetry of maxilla & mandible &
adult cases with severe antero-posterior
skeletal discrepancies
18. Diagnostic aids
The routine diagnostic aids such as :
Case history
Clinical examination & study models
Maxillary occlusal view radiograph – to see mid-
palatal suture
P.A cephalogram – to estimate the amount of
expansion that has taken place
Occliusal radiograph
19. Rapid maxillary expansion appliances
Numerous appliances have been used for rapid
maxillary expansion.Broadly they can be
classified as :
a. Tooth borne
b. Tooth & tissue borne
These are fixed appliance & appliance that
are fixed onto the teeth are more reliable &
found to produce consistent skeletal effects.
Examples of tooth borne appliances include:
i. Isaacson type
ii. Hyrax type
Two of commonly used tooth & tissue borne
appliances are :
i. Derichsweiler type
20. Isaacson type
This appliance has a special spring loaded screw
called a MINNE expander,consists of a coil spring
having a nut that can compress the spring
It is soldered directly to the bands
No acrylic is used
Easy to fabricate
Expander is activated by closing the nut so that the
spring gets compressed.
21. Hyrax type
This type of appliance makes use of a special
type of screw called HYRAX (Hygiene Rapid
Expander)
The screws have heavy gauge wire
extensions that are adapted to follow the
palatal contour & are soldered to bands on
premolars & molars.
22. Derichsweiler type
The first premolars & first molars are banded
Wire tags are soldered onto the palatal aspect of
the bands
These wire tags get inserted into a split palatal
acrylic plate incorporating a screw at its centre.
23. Hass type
The first premolar & molar of either side are
banded
A thick stainless steel wire of 1.2mm diameter is
soldered on the buccal & lingual aspects
connecting the premolar & molar bands
Lingual wire is kept longer so as to extend past
the bands both anteriorly & posteriorly
Free ends turned back and embedded in acrylic.
A screw is incorporated.
24. BONDED R.M.E
Most of the RME appliances described earlier are
banded appliances .They incorporate bands on
the first premolars & molars.
An alternative design of the appliance would be to
have a splint covering variable number of teeth
on either side to which the jackscrew is attached.
Raymond Howe in 1982 developed this appliance
Clears the palate from acrylic
No banding needed- can be used on malposed teeth
where parallel path of insertion is not possible
Less error prone as bands don’t have to be placed in
impression
Easy to make on deciduous teeth.
26. Instruction on how to expand
(activation schedule)
Schedule by Timms :
Upto age of 15 years : the turn 180⁰ is given as 90⁰ in
the morning & 90⁰ in the evening.
Zimring & Isaacson in 1965 :
Young growing patients : two turns each day for the
first 4-5 days & later one turn each day for remainder
of RME treatment.
Non growing adult patients : two turns each day for
the first two days & one turn each day for the next 5-7
days & one turn every alternate day till desired
expansion is achieved.
27. Effects of RME
Effect on maxilla
Opening of the mid-palatal suture
Downwards & forward maxillary movement
Effect on maxillary teeth
Midline spacing between the two maxillary central incisors
Maxillary posterior teeth show buccal tipping & extrusion
Effect on mandible
Downward & backward rotation of the mandible
Increase in face height
Reduction in overbite
Effect on nasal cavity
Reduced resistance to nasal air flow
Increase in intra-nasal space
28. Hazards of RME
Oral hygiene
Length of fixation
Dislodgement & breakage
Tissue damage
Infection
Pain or discomfort,dizziness,pressure at the
bridge of nose etc
29. Comparison between slow & rapid
expansion
Slow expansion Rapid expansion
1. Type of expansion –
both skeletal & dental
changes seen from
beginning
2. Rate of expansion - slow
3. Type of tissue retraction
- more physiologic
4. Force used –milder force
(2-4 lbs)
5. Frequency of activation-
less frequent (0.5-
1mm/week)
6. Duration of treatment-
long
7. Type of appliance-either
fixed or removable
8. Age-any age
9. Retention-lesser chance
of relapse
1. Predominantly skeletal
changes initially,later
dental changes take
place with skeletal
relapse
2. Rapid
3. More traumatic
4. Greater force (10-20 lbs )
5. More frequent (0.5-
1mm/day)
6. Short
7. Mostly fixed appliance
8. Before fusion of mid-
palatal suture
9. More chance of relapse
30. EXPANSION OF CLEFT PALATE
CASES
Excessive anterior collapse coupled to little or no
posterior collapse
More fan wise expansion needed to restrict
posterior expansion.Screws of longer thread of
upto 18mm expansion
More difficult to retain due to clinical crowns not
developed properly
Unilateral expansion both cap splints & bands
can be used
Formation of fistula could be a complication
31. Expansion of mandibular arch
Stable expansion is difficult to attain in the lower
arch
Present studies state that expanding the upper
arch allows for spontaneous expansion of the
lower arch to some extent.
32. Other methods of expansion
Surgically assisted RME
Transpalatal arch
Magnets
Ultra rapid expansion
Though these methods are not used
frequently.
34. Reference
1. Contemporary Orthodontics,5th edition by
William R.Proffit,Henry W.Fields,David M.Sarver
2. Graber Orthodontics text book,5th edition
3. Kharbanda Orthodontics text book,5th edition
4. Orthodontics text book by S.I. Bhalaji,6th edition
