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1. Merrifield’s modification
Based on five concepts:-
1) Sequential appliance placement
2)Sequential&/ individual tooth movement
3) Sequential mandibular anchorage preparation
4) Directional forces including control of the
vertical dimension to enhance mand.response
5) Proper timing of treatment
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2. Sequential appliance
placement
Advantages :
a)less traumatic to the patient
b)Easier ,less time consuming
c)Greater efficiency,increased
interbracket span
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3. Sequential anchorage preparation
Tipping two teeth at a time
Use of high pull headgear instead of cl.III
elastics
Controlled ,sequential & precise anchorage
preparation-
Merrifield’s 10-2 system
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4. Directional force concept
Hallmark of modern Tweed –
Merrifield system
-controlled forces that place
the teeth in the most
harmonious relationship with
their environment
- resultant of all the forces
should be upward &
forward for a favourable
skeletal change
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5. Steps of treatment
denture preparation
denture correction
denture completion
denture recovery
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6. Denture preparation
objectives:-
-leveling
-individual tooth movement
&rotation correction
-retraction of both maxillary &
mandibular canine
-preparation of terminal molars
for stress resistance
time: approx. 6 mon.
wires : 0.018X .025 in. mand.
0.017x .022 in. max with
loop stops flush with the second
molar tubes
.
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7.  Mandibular second molar -
effective distal tip 15°
 Maxillary second molar -5°
 2nd premolar offset bends -to
keep canines from expanding
out of alveolar trough
 passive third order bends
 high pull J hook headgear
used to retract max. & mand.
Canines
 1st molars are banded
 canine retraction continued
using powerchains &
headgear force
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8. Denture correction
objectives: -complete space
closure in both the arches
-sequential anchorage
preparation in the mand. Arch
-enhanced curve of occlusion in
the maxillary arch
-cl.I intercuspation of canines &
premolars
wires: .019 X .025 in.mand.
.020X .025 in.max. With
vertical loops distal to lateral
incisors
both the arches are coordinated
each mon. until all max. space is
closed
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9. At the end of space
closure-
-the curve of
occlusion should be
maintained
-mandibular arch
should be
completely level
-dentition is ready for
mand.arch prep
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10.  .019X .025 in. wire loop stops
flush against molar tubes
 ideal 1st & 2nd order bends
 hooks for high pull headgear
distal to central incisors
 10° distal tip1mm mesial to 1st
molar bracket ,compensating
bend which maintains 15°
terminal molar tip
Sequential mandibular anchorage preparation
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11. After 1 mon 5° to 8° distal inclination of 1st molar
Next 5° distal tip 1 mm mesial to 2nd premolar
bracket
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12. It should be based on
-ANB relationship
-maxillary posterior space analysis
-patient cooperation
The following guidelines to be followed:-
1)ANB 5° or less
2) max. 3rd molars missing
3) patient is cooperative ,distalisation best
option
A)mild cl.II (ANB =5°to 8° )
B)average skeletal pattern (FMA =28° /less)
C)normally erupting max. 3rd molars---- extract 2nd
molar ,distalise
Cl. II force system
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13. 1)ANB more than 10°
2)max. 3rd molars present
3)patient motivation questionable
remove 1st molars ,consider surgical correction
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14. Correction of cl. II
relation
-mandibular .021X .028
stabilization wires with
0---ideal 1st ,2nd ,3rd
order bends
-loop stops should be
placed slightly short of
molar tube & wire
passive in all brackets
-gingival spurs distal to
mand, lateral incisors
-max. .020 X .025 in. wire
with closed helical
bulbous arch loops
bent flush against 2nd
molar tube is fabricatedwww.indiandentalacademy.com

15. -progressive 7 °
lingual crown torque
in molar segment
-gingival spur
attached to wire
distal to max. 2nd
premolar bracket
-gingival hooks for
headgear distal to
central incisors
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16. -Closed loops are activated
1mm /side till cl. I molar
relation is achieved
-8oz cl.II elastics
-anterior vertical elastics &
high pull headgear
-closed coil spring placed in
the space b/w 2nd premolar &
1st molar
-elastic chain from 2nd molar
to 1st molar-------
spring & elastic force
distalize the molar
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17. -Cl.II elastic is worn
-anterior vertical elastic--
12 hrs /day
-high pull headgear
--14hrs/day
-distalisation of 2nd
premolars & canines
with E-chains &
headgear
-total time-4 mon.
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18. -closing loops distal
to the lateral incisors
-ideal 1st ,2nd , 3rd
order bends
-closing loops are
opened 1mm /visit
-cl. II --4 to 8 oz
-anterior vertical
elastics & maxillary
high pull headgear
are used along with
cl.II
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19. Denture completion
 finishing archwires
-.021x.028 U/L
 mand.archwire with
same tip back bends
as used previously
 max.arch with artistic
positioning bends &
hooks for elastics &
headgear
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20. At the end of this stage
1) incisors aligned
2) occlusion overcorrected to a
cl.I relation
3) anteriors in an edge-edge
4) max.canines &2nd premolars in a cl.I
relation
5) distal cusp of 1st &2nd molars- out of
occlusion
6) all spaces must be closed tightly from
the 2nd premolar forward
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21. Denture recovery
-When all appliances are removed ,retainers
in place
-Most crucial phase --muscular forces &
periodontal forces are involved
-Recovery based on the concept of
overcorrection
-Posterior disclusion --Tweed occlusion or
transitional occlusion
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22. -Edge -edge relation of incisors develop into
normal overjet & overbite as occlusion settles
down
-muscles of swallowing ,expression &
mastication are actively involved in
determinig the final stable ,esthetic
relationship of teeth referred to as Functional
occlusion
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