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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

2. Sequential appliance
placement
Advantages :
a)less traumatic to the patient
b)Easier ,less time consuming
c)Greater efficiency,increased
interbracket span

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

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

5. Steps of treatment
denture preparation
denture correction
denture completion
denture recovery

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
.

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

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

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

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

11. After 1 mon 5° to 8° distal inclination of 1st molar
Next 5° distal tip 1 mm mesial to 2nd premolar
bracket

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

13. 1)ANB more than 10°
2)max. 3rd molars present
3)patient motivation questionable
remove 1st molars ,consider surgical correction

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 fabricated

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

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

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.

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

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

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

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

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