Tweed philosophy

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 Introduction :Introduction :
History and evolution of the edgewise appliance.History and evolution of the edgewise appliance.
Dr.E.H.Angle, Dr. Charles Tweed, Dr.LevernDr.E.H.Angle, Dr. Charles Tweed, Dr.Levern
Merrifield---contributions to the development ofMerrifield---contributions to the development of
edgewise applianceedgewise appliance
 The Tweed philosophyThe Tweed philosophy
 The Tweed techniqueThe Tweed technique
 The Tweed Merrifield philosophyThe Tweed Merrifield philosophy
 The Tweed Merrifield techniqueThe Tweed Merrifield technique
 ConclusionConclusion

Dr.Edward Hartley AngleDr.Edward Hartley Angle
 The edgewise archThe edgewise arch
mechanism was the brainmechanism was the brain
child of this masterchild of this master
technician.technician.
 By the time ofBy the time of
Dr.Tweed,1930,with theDr.Tweed,1930,with the
introduction of milledintroduction of milled
brackets, S.S ligaturebrackets, S.S ligature
wires it had evolved into awires it had evolved into a
precision appliance, thatprecision appliance, that
demanded accurate fittingdemanded accurate fitting
and placement of bandsand placement of bands
and attachments onand attachments on
teeth.teeth.

IntroductionIntroduction
 The edgewise arch mechanism/appliance wasThe edgewise arch mechanism/appliance was
Dr Angle’s last and greatest contribution toDr Angle’s last and greatest contribution to
orthodontics ,after almost a lifetime devoted toorthodontics ,after almost a lifetime devoted to
improvement of orthodontic appliances.improvement of orthodontic appliances.
 Described it to Fedrick Noyes:Described it to Fedrick Noyes:
““all you can do is push, pull or turn a tooth. Thisall you can do is push, pull or turn a tooth. This
appliance is as fine as I can make it. I haveappliance is as fine as I can make it. I have
given you the appliance. Now for God’s sakegiven you the appliance. Now for God’s sake
use it.”use it.”

 Edgewise mech was designed to place teethEdgewise mech was designed to place teeth
into Angle’s concept of line of occlusion:into Angle’s concept of line of occlusion:
““the line with which in form and position accordingthe line with which in form and position according
to type, the teeth must be in harmony if into type, the teeth must be in harmony if in
normal occlusion.”normal occlusion.”
 Angle believed that there could be only one trueAngle believed that there could be only one true
line of occlusion and it must be the same as theline of occlusion and it must be the same as the
architectural line on which the denturearchitectural line on which the denture
apparatus was constructed.apparatus was constructed.
 This ideal line was intended not only to governThis ideal line was intended not only to govern
the length and breadth of the dental arches, butthe length and breadth of the dental arches, but
also the size and pattern of each tooth cusp andalso the size and pattern of each tooth cusp and
inclined plane composing these arches.inclined plane composing these arches.

 Laber : the best the orthodontist can do isLaber : the best the orthodontist can do is
to secure the normal relationship of teethto secure the normal relationship of teeth
and correct general form of the arch,and correct general form of the arch,
leaving the finer adjustments of individualleaving the finer adjustments of individual
typal form to be worked out by naturetypal form to be worked out by nature
through her forces, which must in anythrough her forces, which must in any
event triumph finally.event triumph finally.

 Angle’s theory:Angle’s theory:
At last here was an appliance with which allAt last here was an appliance with which all
necessary tooth movements,necessary tooth movements, such as restorationsuch as restoration
of normal arch form, correction of all rotationsof normal arch form, correction of all rotations
and all en mass movements of teeth necessaryand all en mass movements of teeth necessary
for normal cuspal relationships could befor normal cuspal relationships could be
achieved.achieved.
He was absolutely correct when his treatmentHe was absolutely correct when his treatment
techniques were adhered to closely and notechniques were adhered to closely and no
concern was raised to theconcern was raised to the resultant bimaxillaryresultant bimaxillary
protrusion that was the usual aftermathprotrusion that was the usual aftermath of suchof such
treatment procedures.treatment procedures.

Angle’s philosophy of treatmentAngle’s philosophy of treatment
 Based on the then prevalent assumption thatBased on the then prevalent assumption that,if,if
cuspal interdigitation of teeth were made normal,cuspal interdigitation of teeth were made normal,
stimulation by function would result in growth ofstimulation by function would result in growth of
basal bone structures.basal bone structures.
 Little or no thought was given to the inclinationLittle or no thought was given to the inclination
of the mandibular incisor teeth or to normalof the mandibular incisor teeth or to normal
mesiodistal rel of teeth and their respective jawmesiodistal rel of teeth and their respective jaw
bases and head structures.bases and head structures.
 It was assumed function would take care of suchIt was assumed function would take care of such
matters.matters.
 Extraction of teeth for orthodontic therapy wasn’tExtraction of teeth for orthodontic therapy wasn’t
even an option .even an option .

 Research proved otherwise:Research proved otherwise:
The theory that stimulation by functionThe theory that stimulation by function
could and would result in growth ofcould and would result in growth of
maxillary and mandibular basal bonesmaxillary and mandibular basal bones
discarded. No scientific evidence found todiscarded. No scientific evidence found to
indicate that it was possible to grow bonesindicate that it was possible to grow bones
beyond their genetic potential.beyond their genetic potential.

HHISTORYISTORY : EVOLUTION OF: EVOLUTION OF
EDGEWISEEDGEWISE
APPLIANCEAPPLIANCE

E.H. AngleE.H. Angle – Graduation 1878, experienced– Graduation 1878, experienced
many technical problems and frustrations inmany technical problems and frustrations in
treatment which irritated, motivated and inspiredtreatment which irritated, motivated and inspired
him to develop ahim to develop a standard appliance.standard appliance. HisHis
obsession for order motivated him to create theobsession for order motivated him to create the
Angle System 1887Angle System 1887 : this ultimately resulted in: this ultimately resulted in
the multi banded edgewise appliance 5yrs beforethe multi banded edgewise appliance 5yrs before
his death.his death.
5 properties that appliance must have5 properties that appliance must have
 SIMPLE : must push ,pull and rotate teethSIMPLE : must push ,pull and rotate teeth
 STABLE : must be fixed on the teethSTABLE : must be fixed on the teeth
 EFFICIENT : must be based on NEWTON’S 3EFFICIENT : must be based on NEWTON’S 3RDRD
LAWLAW
and anchorageand anchorage
 DELICATE : must be accepted by the tissues and mustDELICATE : must be accepted by the tissues and must
not cause inflammation and sorenessnot cause inflammation and soreness
 INCONSPICUOUS : esthetically acceptableINCONSPICUOUS : esthetically acceptable

The standard appliance used byThe standard appliance used by
AngleAngle
Basic components ofBasic components of
the standardthe standard
appliance used byappliance used by
Angle:Angle:
Traction screw,Traction screw,
jack screw,jack screw,
attachment tubes,attachment tubes,
band materialband material
lever wire,lever wire,
arch wire,wrencharch wire,wrench

DEVELOPMENT OF EDGEWISEDEVELOPMENT OF EDGEWISE
APPLIANCEAPPLIANCE ::
 ANGLE E-ARCHANGLE E-ARCH
 PIN & TUBEPIN & TUBE
 RIBBON ARCH APPLICANCERIBBON ARCH APPLICANCE
 EDGEWISE APPLIANCE.EDGEWISE APPLIANCE.
 EVOLUTION OF EDGEWISE BRACKETS:EVOLUTION OF EDGEWISE BRACKETS:
1)1) SINGLE WIDTH BRACKETSINGLE WIDTH BRACKET
2)2) SIAMESE BRACKETSIAMESE BRACKET
3)3) LEWIS BRACKETLEWIS BRACKET
4)4) STIENER BRACKETSTIENER BRACKET
5)5) BROUSSARD BRACKETBROUSSARD BRACKET

E-archE-arch
 In the late 1800s the orthodontic appliance wasIn the late 1800s the orthodontic appliance was
some sort of rigid framework to which the teethsome sort of rigid framework to which the teeth
were tied so that they could bewere tied so that they could be expanded to theexpanded to the
arch form dictated by the appliance.arch form dictated by the appliance.
 E-arch was an improvement on this basicE-arch was an improvement on this basic
design.design.
 It employed crown movement of teeth withIt employed crown movement of teeth with
simple anchorage.simple anchorage.
 Brass wire ligature and stationary anchorageBrass wire ligature and stationary anchorage
in the molar area were used to expand all thein the molar area were used to expand all the
teeth into normal occlusionteeth into normal occlusion

 Bands were placed on molar teeth andBands were placed on molar teeth and
heavy labial arch wire extended aroundheavy labial arch wire extended around
the arch. The end of the wire wasthe arch. The end of the wire was
threaded and a small nut placed on thethreaded and a small nut placed on the
threaded portion of the arch allowed thethreaded portion of the arch allowed the
archwire to be advanced so that the archarchwire to be advanced so that the arch
perimeter increased.perimeter increased.
 Individual teeth were simply ligated to thisIndividual teeth were simply ligated to this
E-arch.E-arch.

E-arch applianceE-arch appliance

Basic E-archBasic E-arch

 The heavy archwire was supplied in 4 designs:The heavy archwire was supplied in 4 designs:
1.1. Basic E-arch used with baker’s anchorageBasic E-arch used with baker’s anchorage
2.2. Ribbed E-arch used in expansion by tyingRibbed E-arch used in expansion by tying
brass ligatures to arch wirebrass ligatures to arch wire
3.3. E-arch without threaded ends that fit into theE-arch without threaded ends that fit into the
molar sheaths, used with attachment for highmolar sheaths, used with attachment for high
pull headgear.pull headgear.
4.4. E-arch with hooks in maxillary wire ,used toE-arch with hooks in maxillary wire ,used to
move entire maxillary dentition distally.move entire maxillary dentition distally.

Ribbed E-archRibbed E-arch

E-arch with headgearE-arch with headgear

 Advantage:Advantage:
SimplicitySimplicity
 Disadvantge:Disadvantge:
Can deliver only heavy intermittent forcesCan deliver only heavy intermittent forces
Capable of only tipping teeth to newCapable of only tipping teeth to new
position, no precise tooth positioningposition, no precise tooth positioning
possible.possible.
Correction of axial inclination of teeth cant beCorrection of axial inclination of teeth cant be
accomplished.accomplished.

 Angle concluded from his failures that itAngle concluded from his failures that it
was necessary to bodily move teeth.was necessary to bodily move teeth.

Pin and tube appliancePin and tube appliance
 To overcome the inability of E-arch toTo overcome the inability of E-arch to
perform precise tooth positioning, Angleperform precise tooth positioning, Angle
placed bandsplaced bands on other teeth and usedon other teeth and used
vertical tubes on each tooth into whichvertical tubes on each tooth into which
soldered pins from a smaller arch wiresoldered pins from a smaller arch wire
was placed .was placed .
 With this appliance tooth movement wasWith this appliance tooth movement was
accomplished by repositioning theaccomplished by repositioning the
individual pins at each appointment.individual pins at each appointment.

 Orthodontist had toOrthodontist had to
expertly solder pins, fitexpertly solder pins, fit
pins perfectly into tubespins perfectly into tubes
on the bands, remove theon the bands, remove the
pins, move the pins alongpins, move the pins along
the archwire, solder pinsthe archwire, solder pins
again and fit pins onceagain and fit pins once
again into tubes onagain into tubes on
bands..to bring aboutbands..to bring about
tooth movement.tooth movement.

 Disadvantage:Disadvantage:
1.1. Relatively heavy base arch wire used, soRelatively heavy base arch wire used, so
spring quality poor and small adjustments werespring quality poor and small adjustments were
needed which were difficult to makeneeded which were difficult to make
2.2. Construction and adjustment very difficultConstruction and adjustment very difficult
3.3. Though theoretically great precision in toothThough theoretically great precision in tooth
movement is possible, impractical for clinicalmovement is possible, impractical for clinical
use.use.
Neverthless it was the first appliance withNeverthless it was the first appliance with
mechanism for root movement.mechanism for root movement.

Ribbon arch appliance(1915)Ribbon arch appliance(1915)
 Angle modified the tube on each tooth to provideAngle modified the tube on each tooth to provide
a vertically positioned rectangular slot behinda vertically positioned rectangular slot behind
the tube…i.e,brackets with vertical slot.the tube…i.e,brackets with vertical slot.
 Thus brackets were introduced with this newThus brackets were introduced with this new
appliance.appliance.
 Gold ribbon arch wire was placed into the slotGold ribbon arch wire was placed into the slot
and held with brass pins.and held with brass pins.
 Had good spring qualities and efficient inHad good spring qualities and efficient in
aligning malposed teeth.aligning malposed teeth.

Ribbon arch applianceRibbon arch appliance

Disadvantage:Disadvantage:
 not suitable for enmass tooth movement.not suitable for enmass tooth movement.
 Mesial and distal tipping bends could notMesial and distal tipping bends could not
be incorporated into the archwire.be incorporated into the archwire.
 Poor root positioning controlPoor root positioning control
 Resiliency of the arch wire did not allowResiliency of the arch wire did not allow
generation of the moments necessary togeneration of the moments necessary to
torque roots to a new position.torque roots to a new position.

Edgewise applianceEdgewise appliance
(introduced 1928)(introduced 1928)
 To overcome the deficiencies of hisTo overcome the deficiencies of his
previous appliances, Angle changed theprevious appliances, Angle changed the
form of the bracket in the ribbon archform of the bracket in the ribbon arch
appliance. He placed the slot in theappliance. He placed the slot in the
centre and oriented the slot from verticalcentre and oriented the slot from vertical
to horizontal and inserted a rectangularto horizontal and inserted a rectangular
wire rotated 90wire rotated 9000
to the orientation the wireto the orientation the wire
had with the ribbon arch brackethad with the ribbon arch bracket
(hence the name edgewise)(hence the name edgewise)

Edgewise applianceEdgewise appliance

 Edgewise bracketEdgewise bracket
when formedwhen formed
consisted of 3 wallsconsisted of 3 walls
within the bracket.within the bracket.
 0.022 x0.028..0.022 x0.028..
 Soft gold originallySoft gold originally
which tended towhich tended to
deform easilydeform easily
 Slot orientedSlot oriented
horizontally.horizontally.

 EDGEWISE APPLIANCEEDGEWISE APPLIANCE
metal bracket …. slot in center, placed inmetal bracket …. slot in center, placed in
horizontal plane 0.022 x 0.028” rectangularhorizontal plane 0.022 x 0.028” rectangular
wire in narrow/ edgewise positionwire in narrow/ edgewise position
Unique featureUnique feature  rectangular wire inrectangular wire in
rectangular slotrectangular slot  twisting / torquing forcestwisting / torquing forces
could be imparted to control the axialcould be imparted to control the axial
inclination of teethinclination of teeth
So possible to move teeth in all 3 planes ofSo possible to move teeth in all 3 planes of
space with a single arch wire.space with a single arch wire.

Evolution of edgewise bracketsEvolution of edgewise brackets
 Single width brackets:Single width brackets:
0.050 inch wide and soldered to gold0.050 inch wide and soldered to gold
band material.band material.
because of the narrow width, the bracketbecause of the narrow width, the bracket
by itself was ineffective for tooth rotation.by itself was ineffective for tooth rotation.
so gold eyelets were soldered at appropriateso gold eyelets were soldered at appropriate
positions on the band..ligature tied from eyeletpositions on the band..ligature tied from eyelet
to archwire to effect rotations…needed repeatedto archwire to effect rotations…needed repeated
tying.tying.
time consuming and inefficient.time consuming and inefficient.

 Two brackets on a single tooth.Two brackets on a single tooth.
the two brackets were placed so as tothe two brackets were placed so as to
effect rotation of tooth.effect rotation of tooth.

 TWIN BRACKET: (siamese twin brackets)TWIN BRACKET: (siamese twin brackets)
Swain..originator of the idea.Swain..originator of the idea.
two edgewise brackets joined together ontwo edgewise brackets joined together on
common base.common base.
0.05 inch distance b/t the two.0.05 inch distance b/t the two.
initially used only on centrals and molars.initially used only on centrals and molars.
later narrower width brackets for otherlater narrower width brackets for other
teeth.:4 types:teeth.:4 types:
extra wide, standard, intermediate and junior.extra wide, standard, intermediate and junior.

 Advantage of twin bracket:Advantage of twin bracket:
1.1. effective for rotation correction.effective for rotation correction.
2.2. greater axial controlgreater axial control
3.3. incorporates positive control:once toothincorporates positive control:once tooth
has been derotated mere tying of wirehas been derotated mere tying of wire
to bracket with ligature maintains theto bracket with ligature maintains the
tooth in its corrected position.tooth in its corrected position.

 Disadvantage:Disadvantage:
because of the increased width of the twinbecause of the increased width of the twin
bracket, the amount of wire available b/tbracket, the amount of wire available b/t
brackets on the arch decreased.brackets on the arch decreased.
Adverse effect on inherent resiliency of archwire.Adverse effect on inherent resiliency of archwire.
also in closing loop arch wires and second orderalso in closing loop arch wires and second order
bends,decreased interbracket span interferesbends,decreased interbracket span interferes
with amt of closing action that can be attained.with amt of closing action that can be attained.

 Lewis bracketLewis bracket::
another approach to address problem ofanother approach to address problem of
rotation correctionrotation correction
soldered auxilary rotation arms thatsoldered auxilary rotation arms that
abutted against the bracket,thus offeringabutted against the bracket,thus offering
lever arm to deflect archwire and derotatelever arm to deflect archwire and derotate
the tooth.the tooth.

 Steiner bracketsSteiner brackets::
Flexible rotation arms incorporated…so didFlexible rotation arms incorporated…so did
not depend entirely on resiliency ofnot depend entirely on resiliency of
archwire for tooth rotation.archwire for tooth rotation.
 Broussard bracketBroussard bracket::
addition of 0.0185 x0.046 vertical slot toaddition of 0.0185 x0.046 vertical slot to
accept a doubled 0.018 auxillary wire.accept a doubled 0.018 auxillary wire.

Dr.Charles.H.TweedDr.Charles.H.Tweed

CHARLES H.TWEED :CHARLES H.TWEED : Graduated from anGraduated from an
improved Angle course in 1928 at the age of 33yr.improved Angle course in 1928 at the age of 33yr.
Helped Dr.Angle in publishingHelped Dr.Angle in publishing an article in the dentalan article in the dental
Cosmos.Cosmos.
Returned to Arizona and in Pheonix established the FirstReturned to Arizona and in Pheonix established the First
pure edgewise speciality practice in U.S. For the next 2yr withpure edgewise speciality practice in U.S. For the next 2yr with
Dr.Angle’s advise followed edgewise technique .Dr.Angle’s advise followed edgewise technique .
Dr.Angle urged his dear student to :Dr.Angle urged his dear student to :
1.1. Dedicate his life to the development of the edgewise applianceDedicate his life to the development of the edgewise appliance
2.2. To make every effort to make orthodontics as an specialty within theTo make every effort to make orthodontics as an specialty within the
dental profession.dental profession.
Following advise Dr.Tweed instigated the first orthodontic specialtyFollowing advise Dr.Tweed instigated the first orthodontic specialty
law in the U.S.. In 1929 first law limiting the practice of orthodontics tolaw in the U.S.. In 1929 first law limiting the practice of orthodontics to
specialists was passed ; Dr.Tweed received certificate no1. in Arizonaspecialists was passed ; Dr.Tweed received certificate no1. in Arizona
to become the first certified specialist in orthodontics in the U.S.to become the first certified specialist in orthodontics in the U.S.

 Aug 11, 1930, Angle died at age of 75yr.Aug 11, 1930, Angle died at age of 75yr.
 Tweed held to Angle’s conviction that one must neverTweed held to Angle’s conviction that one must never
extract teeth, but this lasted for only 4yrs.In 1932 publishedextract teeth, but this lasted for only 4yrs.In 1932 published
article in Angle orthodontist “reports of cases treated witharticle in Angle orthodontist “reports of cases treated with
Edgewise Arch mechanism.”Edgewise Arch mechanism.”
 What he observed in his patients during retention was soWhat he observed in his patients during retention was so
discouraging for him that he almost gave up practice. Hediscouraging for him that he almost gave up practice. He
devoted the next 4yrdevoted the next 4yr studying his successes and failures.hestudying his successes and failures.he
made a most important observation:made a most important observation:
 Lack of harmony in facial contour was in direct proportion toLack of harmony in facial contour was in direct proportion to
the extent to which the denture had been displaced mesiallythe extent to which the denture had been displaced mesially
into protrusion.into protrusion.
 Upright mandibular incisors frequently were related to postUpright mandibular incisors frequently were related to post
treatment facial balance and succesful treatment.treatment facial balance and succesful treatment.
ToTo position mandibular incisors upright ,he concluded oneposition mandibular incisors upright ,he concluded one
must prepare anchorage and extract teeth.must prepare anchorage and extract teeth.

 He selected failed cases and treated themHe selected failed cases and treated them
with premolar extractions.with premolar extractions.
 Was called a traitor ,faced critisism.Was called a traitor ,faced critisism.
 In 1940 he produced case reports of theIn 1940 he produced case reports of the
retreated cases.retreated cases.

 Tweed made considerable effort to placeTweed made considerable effort to place
mandibular incisors at 90 +/- 5 deg to MPmandibular incisors at 90 +/- 5 deg to MP
without resorting to removal of teeth. Inwithout resorting to removal of teeth. In
some cases this was achieved by oversome cases this was achieved by over
expansion of dental arches , but too oftenexpansion of dental arches , but too often
at the expense of impacting bothat the expense of impacting both
Unerupted 2Unerupted 2ndnd
and 3and 3rdrd
molars. Themolars. The
aftermath of such treatment was relapseaftermath of such treatment was relapse
and damage to investing tissue.and damage to investing tissue.

Importance of identifying growthImportance of identifying growth
trends of patientstrends of patients
1.Type A growth trends :1.Type A growth trends :
middle and lower face are growing forward andmiddle and lower face are growing forward and
downward in unision with no change in the ANB angle.downward in unision with no change in the ANB angle.
growth is aprroximately equal in both vertical andgrowth is aprroximately equal in both vertical and
horizontal dimensions.horizontal dimensions.
if molar relationship is class II and the ANB exceedsif molar relationship is class II and the ANB exceeds
4.5deg its4.5deg its type A subdiv growth trendtype A subdiv growth trend. It is better to place. It is better to place
the patient on Kloehn cervical Headgear to restrainthe patient on Kloehn cervical Headgear to restrain
maxillary growth.maxillary growth.
Prognosis is good because the point B is movingPrognosis is good because the point B is moving
forwards as the maxillary denture is moved posteriorly.forwards as the maxillary denture is moved posteriorly.

 Type B growth trend :Type B growth trend :
the middle face is growing forward more rapidlythe middle face is growing forward more rapidly
than the lower, ANB increases in size withthan the lower, ANB increases in size with
growth.growth.
if ANB is <4 deg prognosis is fair,one mayif ANB is <4 deg prognosis is fair,one may
expect reasonably good facial changes andexpect reasonably good facial changes and
good occlusion.good occlusion.
if ANB 7-12 deg prognosis poor.if ANB 7-12 deg prognosis poor.
Growth of the middle and lower face isGrowth of the middle and lower face is
predominantly in the vertical dimension.predominantly in the vertical dimension.

 Type C growth trend:Type C growth trend:
the lower face is growing forward and downwardthe lower face is growing forward and downward
more rapidly than the middle face, with amore rapidly than the middle face, with a
decrease in the size of the ANB.decrease in the size of the ANB.
prognosis very good from the point of view ofprognosis very good from the point of view of
facial esthetics.facial esthetics.
But during retention one has to observe for anyBut during retention one has to observe for any
lingual tipping of mandibular incisors or labiallingual tipping of mandibular incisors or labial
tipping of maxillary incisors. Prolonged retentiontipping of maxillary incisors. Prolonged retention
may be required depending on the type ofmay be required depending on the type of
perioral musculature.perioral musculature.
Regardless of the size of the FMA , when theRegardless of the size of the FMA , when the
growth is mostly in the horizontal direction thegrowth is mostly in the horizontal direction the
growth trend isgrowth trend is type C subdivisiontype C subdivision

TWEEDS CONTRIBUTIONS:TWEEDS CONTRIBUTIONS:
a)a) Emphasized theEmphasized the 4 objectives of orthodontic treatment4 objectives of orthodontic treatment
with emphasis & concern for facial esthetics.with emphasis & concern for facial esthetics.
1.the best balance and harmony of facial lines1.the best balance and harmony of facial lines
2.Stability of dentures after treatment2.Stability of dentures after treatment
3.Healthy mouth tissues3.Healthy mouth tissues
4.An efficient chewing mechanism4.An efficient chewing mechanism
b)b) Developed the concept ofDeveloped the concept of uprighting teeth over basaluprighting teeth over basal
bone with emphasis on the mandibular incisorsbone with emphasis on the mandibular incisors
c)c) Made theMade the extraction of teeth for orthodontic correctionextraction of teeth for orthodontic correction
acceptable & popularized extraction of 1acceptable & popularized extraction of 1stst
pre molar.pre molar.
d) Enhanced thed) Enhanced the clinical application of cephalometrics.clinical application of cephalometrics.

e.e. Developed diagnostic facial triangle to makeDeveloped diagnostic facial triangle to make
cephalometrics a diagnostic tool as well as a guide incephalometrics a diagnostic tool as well as a guide in
treatment & evaluation of treatment results.treatment & evaluation of treatment results.
1. the normal range of inclination of the mandibular1. the normal range of inclination of the mandibular
incisors to MP was 90+/- 5deg.incisors to MP was 90+/- 5deg. (IMPA)(IMPA)
2. when he was working on why he could not make his2. when he was working on why he could not make his
unfavorable patiens beautiful like his favorables evenunfavorable patiens beautiful like his favorables even
with identical treatment,with identical treatment,
he found out that thehe found out that the FMAFMA was the differencewas the difference
(recognised the importance of different growth trends)(recognised the importance of different growth trends)
norm=25 deg, range=16-35deg; extraction ofnorm=25 deg, range=16-35deg; extraction of
teeth was more necessary in patients withteeth was more necessary in patients with
FMA >30deg.FMA >30deg.
3. 33. 3rdrd
angleangle FMIA was 65 deg.FMIA was 65 deg. the size of the FMIA wasthe size of the FMIA was
found crucial in creating satisfactory facial estheticsfound crucial in creating satisfactory facial esthetics
with orthodontic treatment.with orthodontic treatment.

Tweed’s diagnostic facial triangleTweed’s diagnostic facial triangle

f. Developed concepts off. Developed concepts of orderly treatmentorderly treatment
procedures & introduced anchorageprocedures & introduced anchorage
preparation as a major step in treatmentpreparation as a major step in treatment
g.Developed a fundamentally soundg.Developed a fundamentally sound
consistent pre orthodontic guidanceconsistent pre orthodontic guidance
programprogram using & popularizing serialusing & popularizing serial
extraction of primary & permanent teeth.extraction of primary & permanent teeth.

 Angle gave orthodontics the EdgewiseAngle gave orthodontics the Edgewise
bracket ,but Tweed gave the speciality thebracket ,but Tweed gave the speciality the
 The TWEED PHILOSOPHY was born.The TWEED PHILOSOPHY was born.
 He devoted 42yrs of his life from 1928 tillHe devoted 42yrs of his life from 1928 till
his death on Jan 11,1970 to thehis death on Jan 11,1970 to the
advancement of edgewise appliance.advancement of edgewise appliance.

Levern MerrifieldLevern Merrifield
LEVERN MERRIFIELDLEVERN MERRIFIELD
1953 :1953 : took TWEED coursetook TWEED course
1960 :1960 : selected byselected by
Dr.Tweed to be codirectorDr.Tweed to be codirector
and continue his work onand continue his work on
edgewise appliance.edgewise appliance.
1970 : Director1970 : Director  study ofstudy of
orthodontic dentistry &orthodontic dentistry &
development ofdevelopment of
edgewise applianceedgewise appliance

Merrifield’s contributionsMerrifield’s contributions
A.Diagnostic concepts:A.Diagnostic concepts:
Introduced diagnostic analyses which allowIntroduced diagnostic analyses which allow
clinicians to determine whether and whenclinicians to determine whether and when
extractions are necessary, if indicated which teethextractions are necessary, if indicated which teeth
to be extracted.to be extracted.
1.1. The dimensions of the dentitionThe dimensions of the dentition :anterior:anterior
limit ,posterior limit ,lateral limit and verticallimit ,posterior limit ,lateral limit and vertical
limit exists..these limitations must belimit exists..these limitations must be
recognised and treatment designed to conformrecognised and treatment designed to conform
to these limitations when normal muscleto these limitations when normal muscle
balance exists.balance exists.

Merrifield’s diagnostic conceptsMerrifield’s diagnostic concepts
2.Recognise the dimensions of the dentition and2.Recognise the dimensions of the dentition and treat fortreat for
maximum facial harmony and balancemaximum facial harmony and balance ::
essentiallyessentially 3 factors affect facial balance:3 factors affect facial balance:
 Position of teethPosition of teeth
 Skeletal patternSkeletal pattern
 Soft tissue thicknessSoft tissue thickness : total chin thickness and upper: total chin thickness and upper
lip thickness must be equallip thickness must be equal
Careful consideration of these factors will enableCareful consideration of these factors will enable
the clinician to determine whether dentalthe clinician to determine whether dental
compensation will improve facial balance.compensation will improve facial balance.

Upper lip thickness and total chinUpper lip thickness and total chin
thicknessthickness
If the total chinIf the total chin
thickness is lesser thanthickness is lesser than
upper lip thickness, theupper lip thickness, the
anterior teeth must beanterior teeth must be
positioned uprightpositioned upright
further to facilitate afurther to facilitate a
more balanced facialmore balanced facial
profile because lip retractionprofile because lip retraction
follows tooth retractionfollows tooth retraction

SomeSome measurements to judge facial balance:measurements to judge facial balance:
1.1. Profile lineProfile line
2.2. On frontal view vermilion border of the lower lip should bisect the distanceOn frontal view vermilion border of the lower lip should bisect the distance
between the bottom of the chin and the ala of the nose.between the bottom of the chin and the ala of the nose.
3.3. FMIA : Tweed believed this angle was significant in establishing balanceFMIA : Tweed believed this angle was significant in establishing balance
and harmony of the lower face. Related to FMA.and harmony of the lower face. Related to FMA.
ForFor FMA 22-28 deg, FMIA 68degFMA 22-28 deg, FMIA 68deg
Standard : FMA 30 deg ; FMIA 65deg.Standard : FMA 30 deg ; FMIA 65deg.
dental compensation for a high FMA requires additional uprighting ofdental compensation for a high FMA requires additional uprighting of
flared mandibular incisors..visa versa.flared mandibular incisors..visa versa.
4.4. Z – angleZ – angle : indicative of soft tissue profile and more responsive to maxillary: indicative of soft tissue profile and more responsive to maxillary
incisor retraction than FMIAincisor retraction than FMIA
70-80 deg normal range70-80 deg normal range
75-78 deg ideal, depending on age and gender.75-78 deg ideal, depending on age and gender.

Profile line in a balanced faceProfile line in a balanced face
 When facial balanceWhen facial balance
is present, the idealis present, the ideal
relationship of profilerelationship of profile
line is to beline is to be tangent totangent to
the chin and thethe chin and the
vermillion border ofvermillion border of
both the lips andboth the lips and
should lie in theshould lie in the
anterior 1/3anterior 1/3rdrd
of theof the
nose.nose.

Profile line in a face not in balanceProfile line in a face not in balance

Merrifield’s Z-angle and FMIAMerrifield’s Z-angle and FMIA
Z- angle :Z- angle :
70-80 deg range70-80 deg range
75 -78 deg ideal75 -78 deg ideal
Maxillary incisorMaxillary incisor
retraction of 4mmretraction of 4mm
allows 4mm of lower lipallows 4mm of lower lip
retraction and 3mm ofretraction and 3mm of
upper lip responseupper lip response

Merrifield’s diagnostics conceptsMerrifield’s diagnostics concepts
5.Skeletal factors5.Skeletal factors in facial balance: (cranial disharmony )in facial balance: (cranial disharmony )
FMA,IMPA,SNA,SNB,ANB,FMA,IMPA,SNA,SNB,ANB,
Ao-Bo,Occlusal plane angle,Ao-Bo,Occlusal plane angle,
PFH,AFH,facial height index (0.69),facial heightPFH,AFH,facial height index (0.69),facial height
change ratiochange ratio
Merrifield and Gebeck reported a 2:1 increase in PFHMerrifield and Gebeck reported a 2:1 increase in PFH
compared to AFH in successfully treated class II patients.compared to AFH in successfully treated class II patients.
6.Jim Gramling’s probability index:6.Jim Gramling’s probability index:
observed that in successfully treated class II patientsobserved that in successfully treated class II patients
FMA was controlled , FMIA increased,FMA was controlled , FMIA increased,
IMPA reduced , Z-angle increased , AO-BO reducedIMPA reduced , Z-angle increased , AO-BO reduced
mandibular incisor position was corrected.mandibular incisor position was corrected.

Probability index suggests that theProbability index suggests that the
followingfollowing pre treatment conditions might bepre treatment conditions might be
necessary for Class II treatment success :necessary for Class II treatment success :
FMA should be 22-28 deg .FMA should be 22-28 deg .
ANB should be 6 deg or less .ANB should be 6 deg or less .
FMIA should be greater than 60 deg .FMIA should be greater than 60 deg .
Occlusal plane should be 7 deg or less .Occlusal plane should be 7 deg or less .
SNB should be 80 deg or more .SNB should be 80 deg or more .

Differential diagnosis analysis systemDifferential diagnosis analysis system
Cranio facial Analysis :Cranio facial Analysis :
Vertical component :Vertical component :
FMA :22-28 degFMA :22-28 deg
AFH/PFH ratio : 0.65 to 0.75AFH/PFH ratio : 0.65 to 0.75
Occlusal Plane to FHOcclusal Plane to FH
Horizontal componentHorizontal component::
SNBSNB
ANBANB
Z-angleZ-angle

Differential diagnosis analysis systemDifferential diagnosis analysis system
3.3. Total space analysis:Total space analysis: 3 parts:3 parts:
a. Anterior space discrepancy analysis:a. Anterior space discrepancy analysis:
anterior tooth arch surplus/deficitanterior tooth arch surplus/deficit :space available in mandiular arch:space available in mandiular arch
from canine to canine and sum of mesiodistal dimension of sixfrom canine to canine and sum of mesiodistal dimension of six
anterior teeth….+…anterior teeth….+…
cephalometric discrepancycephalometric discrepancy (the amount of space required to upright(the amount of space required to upright
the mandibular incisors for optimum facial balance)the mandibular incisors for optimum facial balance)
b.b. Mid arch discrepancyMid arch discrepancy ::
mid arch tooth discrepancymid arch tooth discrepancy = diff b/t= diff b/t
available midarch space and mesio distal width of 1available midarch space and mesio distal width of 1stst
premolar, 2premolar, 2ndnd
premolar,1premolar,1stst
molar, space required to level curve ofmolar, space required to level curve of
spee.spee.
++
occlusal disharmony :occlusal disharmony : measure distance b/t maxillary premolarmeasure distance b/t maxillary premolar
buccal cusp to embrasure b/t mandibular 1buccal cusp to embrasure b/t mandibular 1stst
and 2and 2ndnd
premolar.premolar.
(difficulty factor of 2)(difficulty factor of 2)

Merrifield’s differential diagnosticMerrifield’s differential diagnostic
analysis systemanalysis system
c.c. Posterior space analysis:Posterior space analysis:
Posterior tooth arch discrepancy:Posterior tooth arch discrepancy:
space availablespace available = distal of mandibular first= distal of mandibular first
molar to ant border of ramus along occlusalmolar to ant border of ramus along occlusal
plane.plane.
required spacerequired space = sum of mesio distal width of= sum of mesio distal width of
2nd molar and 32nd molar and 3rdrd
molars.molars.
Most easily recognisable sign of post spaceMost easily recognisable sign of post space
deficit is late 2deficit is late 2ndnd
molar eruption.molar eruption.

Merrifield’s treatment conceptsMerrifield’s treatment concepts
1.Directional control during treatment1.Directional control during treatment
2.Sequential tooth movement2.Sequential tooth movement
3.Sequential mandibular anchorage3.Sequential mandibular anchorage
preparationpreparation
4.Organisation of treatment into four orderly4.Organisation of treatment into four orderly
steps that have specific objectives.steps that have specific objectives.

Seventh objective of treatmentSeventh objective of treatment
1.1. Clinician must position and arrange teeth for maximumClinician must position and arrange teeth for maximum
facial and dental esthetics.facial and dental esthetics.
2.2. Functional efficiencyFunctional efficiency
3.3. Health of teeth,jaws,joints and surrounding tissue.Health of teeth,jaws,joints and surrounding tissue.
4.4. Stability.Stability.
5.5. Harmonize correction with growth in growing patients.Harmonize correction with growth in growing patients.
6.6. Position the dentition so that it is in state of continualPosition the dentition so that it is in state of continual
harmony with its environment.harmony with its environment.
7.7. The clinical objectives must be pursued in an ethical,The clinical objectives must be pursued in an ethical,
moral and compassionate manner with overridingmoral and compassionate manner with overriding
concern for public welfare.concern for public welfare.

The TWEED philosophy andThe TWEED philosophy and
techniquetechnique

Tweed philosophyTweed philosophy
1.That practically all malocclusions are1.That practically all malocclusions are
characterized by a forward placement ofcharacterized by a forward placement of
teeth in relation to their basal bones.teeth in relation to their basal bones.
Malocclusion is but a symptom of failure inMalocclusion is but a symptom of failure in
growth of the bones upon which thegrowth of the bones upon which the
alveolar processes which form the bonyalveolar processes which form the bony
support of the teeth is built.support of the teeth is built.

Under normal conditionsUnder normal conditions ,i.e normal growth,i.e normal growth
of the basal bones have occurredof the basal bones have occurred
Erupting teethErupting teeth
under influence of muscular forces and antunder influence of muscular forces and ant
component of occlusal forcescomponent of occlusal forces
Teeth are located in proper position onTeeth are located in proper position on
basal bonesbasal bones that the predetermined planthat the predetermined plan
of occlusion called for.of occlusion called for.www.indiandentalacademy.comwww.indiandentalacademy.com

If there isIf there is retardation in forward growth of the jawsretardation in forward growth of the jaws
during growth periodduring growth period
Erupting teethErupting teeth
Under the influenceUnder the influence
of muscular forcesof muscular forces
and ant componentand ant component
areare guided to locations where there is a balance ofguided to locations where there is a balance of
force play up on them.force play up on them.
But the basal bone has failed to grow forward toBut the basal bone has failed to grow forward to
harmonize with this planharmonize with this plan
SoSo teeth get placed too far forward in relation to theteeth get placed too far forward in relation to the
basal structuresbasal structures.( noticed in incisors).( noticed in incisors)

Tweed philosophy contd.Tweed philosophy contd.
2)That the establishment and maintenance of2)That the establishment and maintenance of
stable anchorage is the fundamental factor instable anchorage is the fundamental factor in
successful orthodontic treatment and should besuccessful orthodontic treatment and should be
the initial concern of the operator.the initial concern of the operator.
 This is the outstanding feature of Dr.Tweed’sThis is the outstanding feature of Dr.Tweed’s
philosophy and all other features are built aroundphilosophy and all other features are built around
it.it.
 HisHis first efforts in treatmentfirst efforts in treatment were always directedwere always directed
towardtoward establishing a firm anchorage from whichestablishing a firm anchorage from which
to work.to work.
 This anchorage is not visualized in terms ofThis anchorage is not visualized in terms of
passive stabilization but rather in the form ofpassive stabilization but rather in the form of
dynamic resistancedynamic resistance..

 He believed any clinical orthodontist whoHe believed any clinical orthodontist who
wantswants to routinely create excellent facialto routinely create excellent facial
changeschanges for their patients, willfor their patients, will recognise therecognise the
importanceimportance of and willof and will prepare anchorageprepare anchorage
routinely in their practices.routinely in their practices.

 The degree to which anchorage should beThe degree to which anchorage should be
prepared will vary considerably.prepared will vary considerably.
 Unless one is purposely wanting to move theUnless one is purposely wanting to move the
mandibular buccal segments forward or to movemandibular buccal segments forward or to move
point B downward and backward for somepoint B downward and backward for some
specific reason,specific reason, the terminal mandibular molarsthe terminal mandibular molars
must always be upright to prevent their beingmust always be upright to prevent their being
elongated when class II intermaxillary force iselongated when class II intermaxillary force is
used.used.

 Classified anchorage preparation into THREEClassified anchorage preparation into THREE
categoriescategories ::
1. First degree anchorage preparation:1. First degree anchorage preparation:
minimal anchorageminimal anchorage preparation reqiured.preparation reqiured.
applicable in : malocclusions with ANB 0-4deg ,facialapplicable in : malocclusions with ANB 0-4deg ,facial
esthetics are good, total discrepancy does not exceedesthetics are good, total discrepancy does not exceed
10mm. True class III or Psuedo class III cases.10mm. True class III or Psuedo class III cases.
mandibular anchor molars uprighted /maintained in theirmandibular anchor molars uprighted /maintained in their
upright positions to prevent being elongated by Class IIupright positions to prevent being elongated by Class II
elastics.elastics.
The direction of pull of the elastics in function, will notThe direction of pull of the elastics in function, will not
exceedexceed
90 deg when related to the long axis of the terminal90 deg when related to the long axis of the terminal
molars.molars. www.indiandentalacademy.comwww.indiandentalacademy.com

2.Second degree anchorage preparation:2.Second degree anchorage preparation:
necessary for malocclusions in which ANB > 4.5 degnecessary for malocclusions in which ANB > 4.5 deg
facial esthetics demand that point Bfacial esthetics demand that point B
moved anteriorly and point A posteriorly.moved anteriorly and point A posteriorly.
class II cases, accompanied by type A, type A subdivisionclass II cases, accompanied by type A, type A subdivision
type B, type B subdiv growth trends.type B, type B subdiv growth trends.
anchor prep:anchor prep:
When 2nd molars erupted they are always banded.When 2nd molars erupted they are always banded.
Mandibular terminal molars tipped more distally so thatMandibular terminal molars tipped more distally so that
their distal marginal ridges are at gum level.their distal marginal ridges are at gum level.
the direction of pull of class II elastics rel to long axis ofthe direction of pull of class II elastics rel to long axis of
terminal molars should be greater than 90 deg during function, so thatterminal molars should be greater than 90 deg during function, so that
terminal molars will be further depressed rather than elongated.terminal molars will be further depressed rather than elongated.

3.Third degree anchorage preparation :3.Third degree anchorage preparation :
total anchorage preparation necessary in severetotal anchorage preparation necessary in severe
malocclusions where total discrepancy 14- 20mm ,ANBmalocclusions where total discrepancy 14- 20mm ,ANB
doesn’t exceed 5 deg.doesn’t exceed 5 deg.
class I cases with exceedingly irregular teeth, bimaxclass I cases with exceedingly irregular teeth, bimax
case with mesially inclined teeth.case with mesially inclined teeth.
anchor prep:anchor prep:
Jigs requiredJigs required
all 3 posterior teeth- 2all 3 posterior teeth- 2ndnd
molar, 1molar, 1stst
molar ,2molar ,2ndnd
premolarpremolar
tipped to distoaxial inclinaiton to such a degree thattipped to distoaxial inclinaiton to such a degree that
distal marginal ridges of the terminal molar below gumdistal marginal ridges of the terminal molar below gum
levellevel

3)That the teeth, like inanimate objects, best resist3)That the teeth, like inanimate objects, best resist
the force of displacement whenthe force of displacement when tipped to thetipped to the
angulation that offers the most advantageousangulation that offers the most advantageous
mechanical resistance against the pull ofmechanical resistance against the pull of
dislodging forcesdislodging forces..
They areThey are ultimately best stabilizedultimately best stabilized when theywhen they
overlie the basal ridge of boneoverlie the basal ridge of bone comprising thatcomprising that
portion of the body of the mandible and maxillaeportion of the body of the mandible and maxillae
from which the alveolar processes take theirfrom which the alveolar processes take their
origin.origin.

 It was believed at that time that-“An undisturbedIt was believed at that time that-“An undisturbed
tooth affords the best resistance to movement.”tooth affords the best resistance to movement.”
 Tweed-It is impossible to band a tooth that’s inTweed-It is impossible to band a tooth that’s in
tight contact with a neighbor and have ittight contact with a neighbor and have it
undisturbed.undisturbed.
 ReatinReatin –when teeth are tipped distally as during–when teeth are tipped distally as during
Anchor prep, osteoid tissue is laid down adjacentAnchor prep, osteoid tissue is laid down adjacent
to mesial surface of the tooth being movedto mesial surface of the tooth being moved
distally. This new calcified bundle bone doesntdistally. This new calcified bundle bone doesnt
enhance the resistance to tooth movement whenenhance the resistance to tooth movement when
force is applied ;eg. Class II elastics.force is applied ;eg. Class II elastics.

 Why are the stakes of the tent slanted such thatWhy are the stakes of the tent slanted such that
the pull of the tent ropes against the stake wouldthe pull of the tent ropes against the stake would
not exceed 90deg?not exceed 90deg?
Ans: If the stakes are positioned too vertically intoAns: If the stakes are positioned too vertically into
the ground, when a strong wind blows, thethe ground, when a strong wind blows, the
stakes will be pulled upward and toward the tentstakes will be pulled upward and toward the tent
and the tent will be uprooted.The stakes shouldand the tent will be uprooted.The stakes should
be positioned at an angle which will draw thembe positioned at an angle which will draw them
deeper in to the ground by the pull of the tentdeeper in to the ground by the pull of the tent
ropesropes

 Using this simple mechanical principle, Dr.TweedUsing this simple mechanical principle, Dr.Tweed
said anchorage preparation is mechanical insaid anchorage preparation is mechanical in
nature.(he saw it from a mechanical point of viewnature.(he saw it from a mechanical point of view
than physiological)than physiological)
 If the teeth in the buccal segments of theIf the teeth in the buccal segments of the
mandibular denture are positioned upright, andmandibular denture are positioned upright, and
terminal molars tipped back like tent stakes, soterminal molars tipped back like tent stakes, so
that the pull of the intermaxillary elastics, whenthat the pull of the intermaxillary elastics, when
related to the long axes of terminal molars ,doesrelated to the long axes of terminal molars ,does
not exceed 90deg when the mouth is functioning,not exceed 90deg when the mouth is functioning,
the entire mandibular denture will be more stablethe entire mandibular denture will be more stable
and better able to resist forward displacement.and better able to resist forward displacement.www.indiandentalacademy.comwww.indiandentalacademy.com

 But if we leave the anchor molars in theirBut if we leave the anchor molars in their
undisturbed mesially inclined positions,theundisturbed mesially inclined positions,the
action of class II elastics being upwardaction of class II elastics being upward
and forward, the terminal molars will beand forward, the terminal molars will be
elevated and uprooted.elevated and uprooted.

 If this is allowed to occur, it will beIf this is allowed to occur, it will be
followed by excessive depression of thefollowed by excessive depression of the
mandibular incisors, with a drastic andmandibular incisors, with a drastic and
unecessary alteration of the occlusalunecessary alteration of the occlusal
plane…the FMA will open up and point Bplane…the FMA will open up and point B
will drop downward and backward as thewill drop downward and backward as the
entire mandibular denture is tipped andentire mandibular denture is tipped and
displaced forward into protrusion.displaced forward into protrusion.

 In the use of intermaxillary force, it wasIn the use of intermaxillary force, it was
Dr.Tweed’s contention that theDr.Tweed’s contention that the teeth in theteeth in the
anchorage denture must be placed in distalanchorage denture must be placed in distal
axial inclination if they are to be expected toaxial inclination if they are to be expected to
resist forward and occlusal strain of elastics.resist forward and occlusal strain of elastics.

 The incisors in the anchor denture mustThe incisors in the anchor denture must
be adjusted in lingual axial inclinationbe adjusted in lingual axial inclination toto
give their added support against forwardgive their added support against forward
movement of the entire anchorage base.movement of the entire anchorage base.
 This is aptly termedThis is aptly termed
DYNAMIC ANCHORAGEDYNAMIC ANCHORAGE..

 AlsoAlso teeth must also haveteeth must also have adequate foundationaladequate foundational
support.support.
 TheThe mandibular incisorsmandibular incisors are the most difficult toare the most difficult to
retain permanently in perfect alignment.retain permanently in perfect alignment.
 Dr.Tweed carried these teeth lingualy and placedDr.Tweed carried these teeth lingualy and placed
them such that their roots are overlying the bonythem such that their roots are overlying the bony
ridge arising from the mental area of the body ofridge arising from the mental area of the body of
the mandible.the mandible.
““placing the incisors on the ridge”placing the incisors on the ridge”
 When so relocated incisors showed no tendencyWhen so relocated incisors showed no tendency
of returning to positions of malocclusion than doof returning to positions of malocclusion than do
buccal teeth.buccal teeth.

 So important did Dr.Tweed consider this factorSo important did Dr.Tweed consider this factor
to be that itto be that it became his primary objectivebecame his primary objective inin
treatment and all other dental units in bothtreatment and all other dental units in both
dentures are subsequently adjusted todentures are subsequently adjusted to
harmonize with suchharmonize with such repositioned incisors.repositioned incisors.
 TheThe 11stst
molarsmolars which were looked upon as thewhich were looked upon as the
key teeth in treatment became factors ofkey teeth in treatment became factors of
secondary importancesecondary importance in routine correctivein routine corrective
treatment!!!!treatment!!!!

4)That teeth are most readily moved when4)That teeth are most readily moved when
their property and power of mechanicaltheir property and power of mechanical
resistance has been primarily reduced.resistance has been primarily reduced.

 When teeth that are to be moved areWhen teeth that are to be moved are
found to be at an angulation that they offerfound to be at an angulation that they offer
mechanical resistance to movement, it ismechanical resistance to movement, it is
best to change their angulation to suchbest to change their angulation to such
form that this mechanical resistance toform that this mechanical resistance to
movement is reduced to a minimum.movement is reduced to a minimum.
 This way anchorage is conserved andThis way anchorage is conserved and
tooth movement favoredtooth movement favored

5)That all forces emanating from an5)That all forces emanating from an
orthodontic appliance must beorthodontic appliance must be
synchronized if they are to be mostsynchronized if they are to be most
effective in the mass stabilization or theeffective in the mass stabilization or the
mass movement of teeth.mass movement of teeth.

 Usually one forgets that the denture hasUsually one forgets that the denture has
its component parts arranged on twoits component parts arranged on two
planes of space. The incisors are placedplanes of space. The incisors are placed
in transverse or coronal plane while thein transverse or coronal plane while the
buccal segments are on thebuccal segments are on the
anteroposterior or sagittal plane.anteroposterior or sagittal plane.

 So when using tip-back bends in theSo when using tip-back bends in the
buccal segments and lingual torque in thebuccal segments and lingual torque in the
incisor segment, the purpose of whichincisor segment, the purpose of which
modification is to effect distal crownmodification is to effect distal crown
tippingtipping
the degree of tip-back force mustthe degree of tip-back force must
harmonize with the degree of lingualharmonize with the degree of lingual
torque in incisor region ,else one force willtorque in incisor region ,else one force will
work against the other.work against the other.

6) When teeth are placed in positions of6) When teeth are placed in positions of
mechanical advantage to resist forcesmechanical advantage to resist forces
acting on them… Nature being an expertacting on them… Nature being an expert
mechanic herself….offers biologicalmechanic herself….offers biological
compensations and adjustments…thatcompensations and adjustments…that
more than counterbalance the loss ofmore than counterbalance the loss of
bone stability that results from the initialbone stability that results from the initial
tooth movement made for the purpose oftooth movement made for the purpose of
establishing these adjustments ofestablishing these adjustments of
mechanical advantage.mechanical advantage.

 Biologist’s studies on the effect of toothBiologist’s studies on the effect of tooth
movement on the bony walls of the alveolarmovement on the bony walls of the alveolar
process: (process: (physiological viewpointphysiological viewpoint) :) :
Anchorage was best conserved byAnchorage was best conserved by thethe leastleast
amount of tooth movement possible in the areasamount of tooth movement possible in the areas
desired for resistance of force application.desired for resistance of force application.
It was expected to preserve the original bonyIt was expected to preserve the original bony
trabeculae of alv process, on belief thattrabeculae of alv process, on belief that
undisturbed formation was most resistant toundisturbed formation was most resistant to
subsequent attack upon it by appliancesubsequent attack upon it by appliance
adjustment.adjustment.

 In the Tweed technique, teeth are shifted forIn the Tweed technique, teeth are shifted for
establishing distal and lingual axial inclinationestablishing distal and lingual axial inclination
and to move the mandibular incisors onto theand to move the mandibular incisors onto the
ridge.ridge.
 When properly prepared and bound together byWhen properly prepared and bound together by
proper edgewise archwire adjustments, thisproper edgewise archwire adjustments, this
anchorage unit is far more stable than theanchorage unit is far more stable than the
anchorage arranged according to the idea ofanchorage arranged according to the idea of
biologists.biologists.

 ThisThis is both mechanical and biologicalis both mechanical and biological (the new bone(the new bone
formation taking place coincidental to the tooth changes)formation taking place coincidental to the tooth changes)
in action.in action.
 When the molar and premolar teeth are in distal axialWhen the molar and premolar teeth are in distal axial
inclination and archwire tied into the brackets, forwardinclination and archwire tied into the brackets, forward
tipping of any of these units, that may subsequently taketipping of any of these units, that may subsequently take
place ,will exert a downward pressure on the tooth next inplace ,will exert a downward pressure on the tooth next in
line mesially.line mesially.
 Resistance to downward pressure on a tooth is believedResistance to downward pressure on a tooth is believed
to be the greatest of all resisting power becauseto be the greatest of all resisting power because
functional demands requirefunctional demands require this to be so.this to be so.
 Hence by adjusting the teeth like in tweed technique thisHence by adjusting the teeth like in tweed technique this
power will be called into action for anchorage purposes.power will be called into action for anchorage purposes.

7) If malocclusion is a manifestation of7) If malocclusion is a manifestation of
forward positioning of the teeth in relationforward positioning of the teeth in relation
to their basal bones, then the dental unitsto their basal bones, then the dental units
will best resist such forward displacementwill best resist such forward displacement
when the buccal teeth are in distal axialwhen the buccal teeth are in distal axial
position and incisor teeth in lingual axialposition and incisor teeth in lingual axial
position.position.

 The natural forces acting on the dentition have aThe natural forces acting on the dentition have a
constant propelling force acting upon the dentureconstant propelling force acting upon the denture
and this tends to forwardly tip the crowns.and this tends to forwardly tip the crowns.
 Such action is made more easy and effective ifSuch action is made more easy and effective if
buccal teeth are in exaggerated mesial axialbuccal teeth are in exaggerated mesial axial
inclination and incisors in labial inclination.inclination and incisors in labial inclination.
 ThereforeTherefore this force will be best resisted bythis force will be best resisted by
placing the buccal teeth in distal axial inclinationplacing the buccal teeth in distal axial inclination
and the incisor teeth in lingual axial inclinationand the incisor teeth in lingual axial inclination..
 In this Tweed technique we place teeth in suchIn this Tweed technique we place teeth in such
strategic positions.strategic positions.

8) by Robert H.W.Strang ,Will M.Thompson8) by Robert H.W.Strang ,Will M.Thompson
Every malocclusion exemplifies a dentureEvery malocclusion exemplifies a denture
that is stabilized by balanced muscularthat is stabilized by balanced muscular
forces and thisforces and this muscular balance must bemuscular balance must be
preserved in treatment if stability in thepreserved in treatment if stability in the
end result is to be attained .end result is to be attained .

 A deformed denture is maintained in its state byA deformed denture is maintained in its state by
balancing forces emanating from itsbalancing forces emanating from its
environmental muscles.environmental muscles.
 There is a muscular balance inherent to eachThere is a muscular balance inherent to each
particular denture/dentition.particular denture/dentition.
 To have a stable result in addition to placingTo have a stable result in addition to placing
teeth over their osseous foundation, one mustteeth over their osseous foundation, one must
aim to preserve muscular balance present inaim to preserve muscular balance present in
original malocclusion.original malocclusion.

1.That practically all malocclusions are1.That practically all malocclusions are
characterized by a forward placement ofcharacterized by a forward placement of
teeth in relation to their basal bonesteeth in relation to their basal bones
2)That the establishment and maintenance2)That the establishment and maintenance
of stable anchorage is the fundamentalof stable anchorage is the fundamental
factor in successful orthodontic treatmentfactor in successful orthodontic treatment
and should be the initial concern of theand should be the initial concern of the
operator.operator.

3)That the teeth, like inanimate objects, best3)That the teeth, like inanimate objects, best
resist the force of displacement whenresist the force of displacement when
tipped to the angulation that offers thetipped to the angulation that offers the
most advantageous mechanicalmost advantageous mechanical
resistance against the pull of dislodgingresistance against the pull of dislodging
forcesforces..
4)That teeth are most readily moved when4)That teeth are most readily moved when
their property and power of mechanicaltheir property and power of mechanical
resistance has been primarily reduced.resistance has been primarily reduced.

5)That all forces emanating from an5)That all forces emanating from an
orthodontic appliance must beorthodontic appliance must be
synchronized if they are to be mostsynchronized if they are to be most
effective in the mass stabilization or theeffective in the mass stabilization or the
mass movement of teeth.mass movement of teeth.

6) When teeth are placed in positions of6) When teeth are placed in positions of
mechanical advantage to resist forcesmechanical advantage to resist forces
acting on them… Nature being an expertacting on them… Nature being an expert
mechanic herself….offers biologicalmechanic herself….offers biological
compensations and adjustments…thatcompensations and adjustments…that
more than counterbalance the loss ofmore than counterbalance the loss of
bone stability that results from the initialbone stability that results from the initial
tooth movement made for the purpose oftooth movement made for the purpose of
establishing these adjustments ofestablishing these adjustments of
mechanical advantage.mechanical advantage.

7) If malocclusion is a manifestation of7) If malocclusion is a manifestation of
forward positioning of the teeth in relationforward positioning of the teeth in relation
to their basal bones, then the dental unitsto their basal bones, then the dental units
will best resist such forward displacementwill best resist such forward displacement
when the buccal teeth are in distal axialwhen the buccal teeth are in distal axial
position and incisor teeth in lingual axialposition and incisor teeth in lingual axial
position.position.

8. Every malocclusion exemplifies a denture8. Every malocclusion exemplifies a denture
that is stabilized by balanced muscularthat is stabilized by balanced muscular
forces and thisforces and this muscular balance must bemuscular balance must be
preserved in treatment if stability in thepreserved in treatment if stability in the
end result is to be attained .end result is to be attained .

 Dr.Tweed did not make major changesDr.Tweed did not make major changes
from how Dr.Angle used edgewisefrom how Dr.Angle used edgewise
 He moved the teeth using the same archHe moved the teeth using the same arch
wire modifications that were taught to himwire modifications that were taught to him
by Dr.Angle, however he used certainby Dr.Angle, however he used certain
modifications/bends in a much moremodifications/bends in a much more
exaggerated form and much moreexaggerated form and much more
frequently.frequently.

 He used round arch wires more often.He used round arch wires more often.
 He used newly adjusted archwires b/tHe used newly adjusted archwires b/t
appointments during treatment thanappointments during treatment than
maintaining the original archwire from startmaintaining the original archwire from start
to finish.This allowed accurate control ofto finish.This allowed accurate control of
tooth movementtooth movement

THE TWEED TECHNIQUETHE TWEED TECHNIQUE

Tweed techniqueTweed technique
Dr.Tweed divides his treatment routine into three phases :Dr.Tweed divides his treatment routine into three phases :
1.Anchorage preparation1.Anchorage preparation : consists of 2 procedures: consists of 2 procedures
a)a) placing the mandibular incisors over their basal boneplacing the mandibular incisors over their basal bone
and giving them a lingual axial inclination by virtue ofand giving them a lingual axial inclination by virtue of
lingual tipping ANDlingual tipping AND
rearranging the axial positions of the buccal teeth,rearranging the axial positions of the buccal teeth,
including the second molars, if possible to best resist anyincluding the second molars, if possible to best resist any
forward displacement ,. This is done by giving aforward displacement ,. This is done by giving a distinctdistinct
distal axial inclination ,gaining complete bracket seatingdistal axial inclination ,gaining complete bracket seating inin
every tooth and then finallyevery tooth and then finally binding all the componentbinding all the component
elements of the denture into one unitelements of the denture into one unit by firmly tying backby firmly tying back
the arch wire to the molar sheath.the arch wire to the molar sheath.

TWEED TECHNIQUETWEED TECHNIQUE
step 1:ANCHORAGE PREP contd.step 1:ANCHORAGE PREP contd.
b) Changing the axial inclination of theb) Changing the axial inclination of the
maxillary teeth especially the incisors, tomaxillary teeth especially the incisors, to
render their resistance to distal movementrender their resistance to distal movement
less effective ,particularly in class II div I.less effective ,particularly in class II div I.

TWEED TECHNIQUE:STEP 2TWEED TECHNIQUE:STEP 2
2. Enmass movement whereby2. Enmass movement whereby
malrelationship of the two dentures ismalrelationship of the two dentures is
corrected and normal inclined planecorrected and normal inclined plane
adjustment gained.adjustment gained.

Tweed technique : step 3Tweed technique : step 3
3. Establishing correct denture form and3. Establishing correct denture form and
completing treatment objectives.completing treatment objectives.

 Knowledge of action and interaction andKnowledge of action and interaction and
reaction of teeth to bends crucial.reaction of teeth to bends crucial.
 First order bends are used to effectFirst order bends are used to effect
expansion and contractionexpansion and contraction of teeth,arch.of teeth,arch.
 The interaction of these 1The interaction of these 1stst
order bendsorder bends
affect 3affect 3rdrd
order position of teeth iforder position of teeth if
expansion forces are used.expansion forces are used.

22ndnd
In mandibular arch:In mandibular arch:
 These used in the posterior segment ofThese used in the posterior segment of
mandibular arch are antagonistic to teeth inmandibular arch are antagonistic to teeth in
anterior segmentanterior segment..
 If proper directional control not used, and careIf proper directional control not used, and care
not taken in application of these bends in anot taken in application of these bends in a
sequential manner…vertical control of anteriorsequential manner…vertical control of anterior
teeth will be lost.teeth will be lost.
 These apply labial crown torque on theThese apply labial crown torque on the
incisors..which is not desirable. Tincisors..which is not desirable. This fact musthis fact must
be given careful consideration during archwirebe given careful consideration during archwire
fabrication.fabrication.

22ndnd
 In maxillary archwire:In maxillary archwire:
 Second order bends in the posteriorSecond order bends in the posterior
segment are complementary to teeth insegment are complementary to teeth in
the anterior segmentthe anterior segment……
 The reaction of the tipping forcesThe reaction of the tipping forces
produced by these 2produced by these 2ndnd
intrudes the maxillary incisors and gives aintrudes the maxillary incisors and gives a
lingual root torque effect to these teeth.lingual root torque effect to these teeth.

33rdrd
 Mandibular arch:Mandibular arch:
 Idea is to place some degree of lingual crownIdea is to place some degree of lingual crown
torque on all teeth.torque on all teeth.
 Posterior and anterior segment work together inPosterior and anterior segment work together in
action, reaction and interactionaction, reaction and interaction..
 Ideal bends :Ideal bends :
 Incisor : -7degIncisor : -7deg
 Canines : -12 degCanines : -12 deg
 22ndnd
premolars and molars : -20 degpremolars and molars : -20 deg

 Maxillary arch:Maxillary arch:
 Conversely 3Conversely 3rdrd
order bends here areorder bends here are
antagonistic.antagonistic.
 Anterior segment needs no torque (0 deg) orAnterior segment needs no torque (0 deg) or
slight lingual root torque.slight lingual root torque.
 Posterior segment needs lingual crown torque:Posterior segment needs lingual crown torque:
 Canines and 1Canines and 1stst
premolar : -7 degpremolar : -7 deg
 Second premolars : -12 degSecond premolars : -12 deg
 In the maxillary arch it is best to apply active 3In the maxillary arch it is best to apply active 3rdrd
order bends sequentially and in only oneorder bends sequentially and in only one
direction at a time.direction at a time.

1.All teeth banded with bracket bands (staples)1.All teeth banded with bracket bands (staples)
Light round wireLight round wire 0.0160.016 used for gaining universal bracketused for gaining universal bracket
engagementengagement
((levelling =teeth brought to common horizontal level)levelling =teeth brought to common horizontal level)
any faulty bracket placement correctedany faulty bracket placement corrected

2. Upper and lower2. Upper and lower 0.018 s.s adjusted0.018 s.s adjusted to engage all brackets.to engage all brackets.
archwire formation:archwire formation:
req length of wire…arch formreq length of wire…arch form given…circular molar loop stopgiven…circular molar loop stop
made…wire place in molar sheaths,canine markings,centralmade…wire place in molar sheaths,canine markings,central
and midline markings made.and midline markings made.
canine curves given,incisors segment curved to confirmcanine curves given,incisors segment curved to confirm
curvature of the denture.curvature of the denture.
passive adjustment to buccal teeth;no bendspassive adjustment to buccal teeth;no bends
molar tipping bends 45 degmolar tipping bends 45 deg placed.placed.
no attempt made to gain space for blocked out teeth tillno attempt made to gain space for blocked out teeth till
resilient 0.021x0.025 wire and class III elastics can be used toresilient 0.021x0.025 wire and class III elastics can be used to
avoid forward movement of teeth crowns.avoid forward movement of teeth crowns.
space should always be gained by distal movemet of toothspace should always be gained by distal movemet of tooth
crowns.crowns.
Archwire tied to all brackets (2-3weeks)Archwire tied to all brackets (2-3weeks)
Retied till bracket engagement gainedRetied till bracket engagement gainedwww.indiandentalacademy.comwww.indiandentalacademy.com

3.3. 0.02 round wire0.02 round wire formed and bracket engagement gained.(6weeks)formed and bracket engagement gained.(6weeks)
4 .4 .Resilient edgewise archwire 0.021x0.025Resilient edgewise archwire 0.021x0.025
used for bringing about tooth movementsused for bringing about tooth movements
fabricaiton:fabricaiton:
markings made…bent to ideal arch formmarkings made…bent to ideal arch form
no bayonet bends given nowno bayonet bends given now
in maxillary wire- moderate lingual torque given in canine and buccalin maxillary wire- moderate lingual torque given in canine and buccal
segment;segment; in the mandibular strong lingual torque given in the buccalin the mandibular strong lingual torque given in the buccal
segment.segment.
in the incisor segment of both either lingual or labial crown torquein the incisor segment of both either lingual or labial crown torque
depending on what will gain passive bracket engagementdepending on what will gain passive bracket engagement..
wire placed in mouth andwire placed in mouth and checkecheckedd if torque that is incorporated isif torque that is incorporated is
harmonious both in incisor and buccal segement.harmonious both in incisor and buccal segement.
proper deg of tip back bend given in anchor molar.proper deg of tip back bend given in anchor molar.
Wire shaped in incisor and canine region; again torque checked forWire shaped in incisor and canine region; again torque checked for
harmony.harmony.
markings for bayonet bends made,bends palcedmarkings for bayonet bends made,bends palced
15 deg distal tip + lingual bend15 deg distal tip + lingual bend( to prevent rotaiton due to lingual( to prevent rotaiton due to lingual
torque in buccal segment)torque in buccal segment) placed at anchor molar.placed at anchor molar.
thus universal bracket engagement is gained.thus universal bracket engagement is gained.

5. No more tooth movement tried till class III elastics can be used, for this5. No more tooth movement tried till class III elastics can be used, for this
anchorage must be prepared in the maxiallry denture first.anchorage must be prepared in the maxiallry denture first.
maxillary denture anchor preparation:maxillary denture anchor preparation:
All teeth banded…0.018 adjusted (6week)All teeth banded…0.018 adjusted (6week)
0.020 adjusted..20deg distal tiping bend at anchor molar (6-9weeks)..0.020 adjusted..20deg distal tiping bend at anchor molar (6-9weeks)..
0.021x0.025 wire…marked lingual torque in buccal segments placed,0.021x0.025 wire…marked lingual torque in buccal segments placed,
slight lingual torque in anterior segment placed,20 deg distal tip bendslight lingual torque in anterior segment placed,20 deg distal tip bend
(anchor molar)…very mild distal tip bends at canine, premolar and 1(anchor molar)…very mild distal tip bends at canine, premolar and 1stst
molar area.molar area.
hooks placed on archwire for occipital anchoragehooks placed on archwire for occipital anchorage
(to avoid forward root movement due to distal tip bend and lingual(to avoid forward root movement due to distal tip bend and lingual
torque)….torque)….6-9 weeks6-9 weeks
0.025x0.028 stabilizing wire ….first passive bracket engagement0.025x0.028 stabilizing wire ….first passive bracket engagement
gained by placing the same deg if tip back bends and lingual torque asgained by placing the same deg if tip back bends and lingual torque as
in the previous wire..in the previous wire..strong tip back bend + lingual bend in anchorstrong tip back bend + lingual bend in anchor
molar area…molar area…
next appointmentnext appointment tip back bends stepped up…anchor tip back bendstip back bends stepped up…anchor tip back bends
stepped up…torque in incisor segment increased…torque in buccalstepped up…torque in incisor segment increased…torque in buccal
segmetns increased to be in harmony with anterior torque..headgear tosegmetns increased to be in harmony with anterior torque..headgear to
be worn atleast 10hr in night.be worn atleast 10hr in night.
MAXILLARY ANCHORAGE PREP complete .MAXILLARY ANCHORAGE PREP complete .

 Mandibular archwire:Mandibular archwire: mandibular anchor preparationmandibular anchor preparation::
0.021x0.025 ….10 deg tip back canine ,premolar and molar area0.021x0.025 ….10 deg tip back canine ,premolar and molar area
placed…greater tip back placed at anchor molar….lingual torqueplaced…greater tip back placed at anchor molar….lingual torque
increased in incisor area…balance b/t distal tip in buccal segment andincreased in incisor area…balance b/t distal tip in buccal segment and
lingual torque in anterior segment maintained.lingual torque in anterior segment maintained.
keeping in mind the fact that movement of incisor roots ,under thekeeping in mind the fact that movement of incisor roots ,under the
influence of lingual torque is more easily and quickly effected than isinfluence of lingual torque is more easily and quickly effected than is
the distal and lingual tipping of tooth crowns in the denture under thethe distal and lingual tipping of tooth crowns in the denture under the
influence of the intermaxiallry elastics…it is considered good toinfluence of the intermaxiallry elastics…it is considered good to
maintain incisor lingual torque at a lesser degree than distal tipingmaintain incisor lingual torque at a lesser degree than distal tiping
bends. if required the torque can later be stepped up.bends. if required the torque can later be stepped up.
class III elastic hooks soldered on archwire (occlusal surface)class III elastic hooks soldered on archwire (occlusal surface)
two kind sof class III elastics given-light and heavy..day time and nighttwo kind sof class III elastics given-light and heavy..day time and night
time wear.(patient warned about the chinless expression that may betime wear.(patient warned about the chinless expression that may be
observed…transient and will disappear when class II elastics areobserved…transient and will disappear when class II elastics are
subsequently used to move maxillayr teeth distally)subsequently used to move maxillayr teeth distally)
Unless the class III elastics are worn steadily the mandibualr teethUnless the class III elastics are worn steadily the mandibualr teeth
roots will move forward instead of their crowns moving distally….ifroots will move forward instead of their crowns moving distally….if
head gear not worn, the maxillary anchorage will be weakened andhead gear not worn, the maxillary anchorage will be weakened and
forward displacement of teeth will take place…soforward displacement of teeth will take place…so patient co-operationpatient co-operation
very important.very important.

 Mandibualr anchor prep continued: Distal tippingMandibualr anchor prep continued: Distal tipping
bends stepped up once in 6weeks…lingual torquebends stepped up once in 6weeks…lingual torque
proportionately stepped up…new wire used ifproportionately stepped up…new wire used if
deformed.deformed.
 Mandibular anchorage and correct denture locaitonMandibular anchorage and correct denture locaiton
may be considered satisfactorily established whenmay be considered satisfactorily established when
the incisor roots overlie the basal ridge and theirthe incisor roots overlie the basal ridge and their
crowns exhibit a distinct lingual axial inclinaitoncrowns exhibit a distinct lingual axial inclinaiton
and when the canine, premolar and molar teeth areand when the canine, premolar and molar teeth are
in distinct distal axial inclination .the distal axialin distinct distal axial inclination .the distal axial
inclination of anchor molars should be greater thaninclination of anchor molars should be greater than
other buccal teeth.other buccal teeth.

Step IIStep II
6.6. Enmass movement to produce normal inclined plane relationship:Enmass movement to produce normal inclined plane relationship:
0.0215x0.028 that is in use in the maxiallry arch when class III elastics0.0215x0.028 that is in use in the maxiallry arch when class III elastics
were worn are replaced bywere worn are replaced by 0.021x0.025 resilient wire…harmonious tip0.021x0.025 resilient wire…harmonious tip
back bends given. lingual torque and lingual molar bends duplicating theback bends given. lingual torque and lingual molar bends duplicating the
ones in previous heavy wire given..ones in previous heavy wire given.. molar stops and intermaxiallry elasticmolar stops and intermaxiallry elastic
hooks soldered…tied to brackets to remainhooks soldered…tied to brackets to remain passive for 3 weekspassive for 3 weeks........activeactive
tip back bends are now given...lingual torque increased slightly in incisortip back bends are now given...lingual torque increased slightly in incisor
area…class II elastics applied…occipital anchorage discontinued.area…class II elastics applied…occipital anchorage discontinued.
mandibular anchorage watched carefully…molar tie ligatures retied atmandibular anchorage watched carefully…molar tie ligatures retied at
every appointment…at any sign of anchorage giving away...tip abckevery appointment…at any sign of anchorage giving away...tip abck
bends, lingual torque, lingual bend increased in anchor molar…inbends, lingual torque, lingual bend increased in anchor molar…in
other teeth proportionately tip back bens and torque increased….still ifother teeth proportionately tip back bens and torque increased….still if
anchor loss occurs…occipital anchorage applied to mandibular denture.anchor loss occurs…occipital anchorage applied to mandibular denture.

TWEED – MERRIFIELDTWEED – MERRIFIELD
PHILOSOPHYPHILOSOPHY

TWEED MERRIFIELDTWEED MERRIFIELD
PHILOSOPHYPHILOSOPHY
1)1) Sequential banding/bondingSequential banding/bonding
2)2) Sequential/individual tooth movementSequential/individual tooth movement
3)3) Sequential mandibular anchorageSequential mandibular anchorage
preparationpreparation
4)4) Directional force including control ofDirectional force including control of
vertical dimension which will enhancevertical dimension which will enhance
mandibular responsemandibular response
5)5) Proper timing of treatmentProper timing of treatment

1)1) Sequential applaince placement :Sequential applaince placement :
 22ndnd
molars, 2molars, 2ndnd
premolars, canines banded, centralspremolars, canines banded, centrals
banded/bondedbanded/bonded
AdvantageAdvantage :: Less traumaticLess traumatic
EasierEasier
Less time consumingLess time consuming
Allows greater efficiency in arch wireAllows greater efficiency in arch wire
action (longer inter bracket span in posterioraction (longer inter bracket span in posterior
seg)seg)
Larger dimension wire can be applied that isLarger dimension wire can be applied that is
less subject to distorsion.less subject to distorsion.
 Once banded teeth respond to the force of arch wireOnce banded teeth respond to the force of arch wire
additional teeth banded , sequence :additional teeth banded , sequence :
After 1After 1stst
appointmentappointment  maxillary 1maxillary 1stst
molars bandedmolars banded
After 2After 2ndnd
appointmentappointment  mandibular 1mandibular 1stst
molars bandedmolars banded

2)2) Sequential tooth movement:Sequential tooth movement:
Tweed had advocated enmass toothTweed had advocated enmass tooth
movementmovement
Advantage : Rapid and precise toothAdvantage : Rapid and precise tooth
movement because theymovement because they
are moved individually/inare moved individually/in
small unitssmall units

3)3) Sequential mandibular anchorageSequential mandibular anchorage
preparation:developed by MERRIFIELDpreparation:developed by MERRIFIELD
““10 – 2” system.10 – 2” system.
Tweed : Enmass anchor preparation;allTweed : Enmass anchor preparation;all
compensation bends placed at onecompensation bends placed at one
time in the archwire and class III elasticstime in the archwire and class III elastics
used for support ----result :used for support ----result :
Labially flared and intrudedLabially flared and intruded
mandibular incisorsmandibular incisors

Merrifield technique –Merrifield technique –
`10 – 2’ Force systems(10 ten teeth used as`10 – 2’ Force systems(10 ten teeth used as
anchor units to tip 2 teeth)anchor units to tip 2 teeth)
++
High pull head gear for support ratherHigh pull head gear for support rather
than class-III elasticsthan class-III elastics
Tooth movement is controlled, sequential andTooth movement is controlled, sequential and
precise….mandibular anchorage can beprecise….mandibular anchorage can be
prepared quickly and easily by tipping only twoprepared quickly and easily by tipping only two
teeth at a time to their anchor prepared position.teeth at a time to their anchor prepared position.

 Initial step of SMAP : IInd molar is tipped to itsInitial step of SMAP : IInd molar is tipped to its
desired anchorage prepared position.desired anchorage prepared position.
 Space closed b/t Ist and IInd molarsSpace closed b/t Ist and IInd molars
 Compensating bend placed mesial to the IIndCompensating bend placed mesial to the IInd
molar to maintain its tipmolar to maintain its tip
 Ist molar is tipped to anchor prepared position.Ist molar is tipped to anchor prepared position.
 Compensating bend placed mesial to molar toCompensating bend placed mesial to molar to
maintian tipmaintian tip
 IInd premolar tipped distally to APP.IInd premolar tipped distally to APP.

Tweed philosophy

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Tweed philosophy