Tweed-Merrifield Appliance: A Historical Perspective

TWEED- MERRIFIELD
APPLIANCE
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INTRODUCTION

HISTORICAL PERSPECTIVE
DR.EDWARD HARTLY ANGLE –
FATHER OFORTHODONTICS
ANGLE SYSTEM-1887
ANGLE SCHOOL OF ORTHODONTIA-
1900

EVOLUTION OF ORTHODONTIC
APPLIANCES
•DR,PIERRE FAUCHARD-A FRENCH PHYSICIAN,1728
USED FLAT METAL STRIP PIERCED WITH HOLES
•SCHANGE-FRENCHMAN,1841,INVENTED ADJUSTABLE
CLAMP BONDWITH INTRODUCTION OF LINGUAL SCREW
•DWINNELE-NEW YORK,1849 INVENTED THE REGULATING
JACK SCREW
•MAGILL OF ERIC, PENNSYLVANIA,1870,
•THUS BY 1875,THE ORTHODONTIC APPLIANCES HAD AN ARCH
WIRE,

•KINGSLEY.(1829-1913)-1861 –HEADGEAR
•COFFIN-1861-FLEXIBLE PIANO WIRE BRACKET ATTACHMENT
•TUCKER- BOSTON-1846-RUBBER ELASTICS
•CASE AND BAKER –POPULARISED IT TO PROVIDE INTERMAXILARY
FORCE INTERMAXILARY ANCHORAGE
EDWARD ANGLE –
A STANDARD ORTHODONTIC APPLIANCE MUST POCESSES 5BASIC
PROPERTIES
1. SIMPLE
2. STABLE
3. EFFICIENT
4. DELICATE
5. INCONSPICUOUS
FINALLY IN 1907 HE DEVELOPED THE “E-ARCH”

THUS ANGLE CONCLUDED THAT BODILY MOVEMENT
OF TEETH WAS ESSENTIAL FOR STABLE RESULTS
DEVELOPED PIN AND TUBE APPLIANCE IN 1909
-THIS WAS DIFFICULT TO MANIPULATE THUS ANGLE DEVELOPED
-RIBBON ARCHAPPLIANCE IN 1915
-THE EDGEWISE APPLIANCE
ANGLE DESIGNEDTHE EDGEWISE BRACKETWIYH A HORIZONTAL
SLOT OF 0.022”x 0.028”-THIS NEW DESIGN PROVIDED MORE
ACCURACY AND EFFICIENT TORQUING HE DESIGNED THIS SYSTEM
IN 1928- 2 YEARS BEFORE HIS DEATH
.

DR.CHARLES TWEED
GRADUATED IN 1928-GEORGE HAHN -IMPROVISED EDGEWISE
HIS CONTRIBUTIONS TO ORTHODONTICS –SUMMARIESED AS –
•EMPHASISED THE 4 OBJECTIVESOF ORTHODONTIC TREATMENT WITH
EMPHASIS AND CONCERN FOR FACIAL ESTHETICS
•DEVELOPED THE CONCEPT O F UPRIGHTING TEETH OVER THE BASAL
BONE WITH EMPHASIS ON MANDIBULAR INCISORS
•MADE EXTRACTION OF TEETH FOR ORTHODONTIC CORRECTION
ACCEPTABLE AND POPULARISED 1ST
PREMOLAR EXTRACTIONS
•ENHANCED THECLINICAL APPLICATION OF CEPHALOMETRICS
•DEVELOPED THE DIAGNOSTIC FACIAL TRIANGLE
•DEVELOPED THE CONCEPT OF ORDERLY TREATMENT AND
INTRODUCED ANCHORAGE PREPARATION
•DEVELOPED A PREORTHODONTIC PROGRAMME-SERIAL
EXTRACTION
.

DR.LEVERN MERRIFIELD
-1952- STUDENT OF DR. TWEED CONTINUE WORK ON EDGEWISE
CONTRIBUTIONS-
1. FUNDAMENTAL CONCEPTS OF “DIMENTIONS OF THEDENTURE”
2. THE DIFFERENSIAL DIAGNOSIS CONCEPTS OF-
• DIMENTIONS OF THE LOWER FACE
• TOTAL SPACE ANALYSIS GUIDLINES FOR SPACE MANAGEMENT-
-FACILITATE MAX. ORTHODONTIC CORRECTION
-DEFINE AREAS OF SKELETAL ,FACIAL AND DENTAL DISHARMONY
3 . THE TREATMENT CONCEPTS OF:
• -DIRECTIONAL CONTROL DURING TREATMENT
• SEQUENTIAL TEEETH MOVEMENT
• SEQUENTIAL MANDIBULAR ANCHORAGE PREPRARATIONS
• ORGANISATION OF TREATMENT INTO 4ORDERLY STEPS, WHICH HAVE SPECIFIC
OBJECTIVES
.

DIMENTIONS OF THE DENTURE-
• MESIAL
• DISTAL
• FACIAL
• LINGUAL
• INTRUSIVE
• EXTRUSIVE
ALLTHESE MOVEMENTSARE RESTRISTED BY BONE ,MUSCLE AND SOFT TISSUE WHICH EXERT
INFLUENCE ON THE TEETH AND JAWS
THERE ARE 4 BASIC DIMENTIONS IN THE PREMISES OF A DENTURE
PREMISE 1
PREMISE II
PREMISE III
PREMISE IV
.

DIFFERENTIAL DIAGNOSIS
THE DETERMINATION OF A DISEASE FROM ITS SYMPTOMS, DATA OR TESTS
AND THE DECISIONS AND JUDGEMENTS MADE PRIORTO TREATMENT
MERRIFIELD’S DIAGNOSTIC PHILOSOPHY IS
• RECOGNISE AND TREAT THE DIMENSION OF THE DENTURE
• RECOGNISE THE DIMENSION S OF THE LOWER FACE AND TREAT h TO ACHIEVE
• MAX FACIAL HARMONY AND BALANCE
• RECOGNISE AND UNDERSTAND THE SKELETAL PATTERN
• THE FACE
.

THE SKELETAL PATTERN
1. ANGLE FMIA
2. ANGLE FMA
3. ANGLE IMPA
4. ANGLE SNA
5. ANGLE SNB
6. ANGLE ANB
7. AO-BO
8. OCCLUSAL PLANE
9. ‘Z’ANGLE
10. POSTERIOR FACIAL HEIGHT
11. ANTERIOR FACIAL HEIGHT
12. FACIAL HEIGHTINDEX
13. FACIAL HEIGHT CHANGE RATIO
.

• RADZIMNSKI (1987), GEBECK AND MERRIFIELD (1989), ISSACSON
1981(1981),PEARSON(1978,1986) AND SCUDY(1973) DESCRIBED THE IMPORTANCE OF THE
RELATIONSHIP BETWEEN CONTROL OFVERTICAL DIMENTION AND SUCCESSFUL
TREATMENT OF CLASS II MALOCCLUSIONS
• UNSUCCESSFUL TREATMENT RESULTS – INCREASE IN AFH
• SUCCESSFUL TREATMENT RESULTS -2:1 RATIO OF INCREASE IN PFH TO AFH
THE DENTITION:
TOTAL SPACE ANALYSIS –
• ANTERIOR
• MID-ARCH
• POSTERIOR
ADVANTAGES OF THIS DIVISION
• SIMPLICITY IN IDENTIFICATION OF SPACE DEFICIT / SURPLUS
• ACCURACY IN DIFFERENTIAL DIAGNOSIS
1. ANTERIOR SPACE ANALYSIS-
2. MID-ARCH ANALYSIS – INVOLVES MANDIBULAR PREMOLARS AND 1ST
MOLAR-
3. IMPORTANT AREA OF THE DENTURE – SHOWS INCLINED 1 ST MOLAR, ROTATIONS
4. SPACINGS, DEEP CURVE OF SPEE, CROSSBITES , MISSING TEETH,HABIT
.

• POSTERIOR SPACE ANALYSIS
THE VARIABLES TO BE CONSIDERED:
• RATE OF MESIO –OCCLUSAL MIGRATIONSS OF MANDIBULAR 1ST
MOLAR
• RATE OF RESORPTION OF ANTERIOR BORDER OF RAMUS
• TIME OF CESATION OF MOLAR MIGRATION
• TIME OF CESATION OF RAMUS RESORPTION
• SEX AND AGE
DIAGNOSTIC SPACE MANAGEMENT GUIDELINES
1)TOTAL SPACE ANALYSIS- TOOTH – ARCH DISCREPANCIES
A) ANTERIOR SURPLUS OR DEFICIT-SPACE MANAGEMENT
B) MID ARCH SURPLUS OR DEFICIT- ANTERIOR DEFICITS OVERIDEMID-ARCH DEFICITS
C) POSTERIOR SURPLUS OR DEFICITS
.

A) SKELETAL DISHARMONIES
• HORIZONTAL CLASS II MALOCCLUSIONS
• HORIZONTAL CLASS III MALOCCLUSIONS
• VERTICAL DISHARMONIES- OPEN BITES
• VERTICAL DISHARMONIES- CLOSED BITES
• FACIAL DISHARMONIES
.

THE TWEED –MERRIFIELD EDGEWISE APPLIANCE
DIRECTIONAL FORCE TECHNIQUE
THIS ADVANCED EDGEWISE TECHNIQUE ALLOWS CONTRACSION, EXPANSION AND
DIRECTIONAL CONTROL OF INDIVIDUAL OR GROUPS OF TEETH
I .BRACKETS AND TUBES:
ALL BRACKETS ARE 0.022 “ 6 ANT TEETH INTERMEDIATE SINGLE WIDTH BRACKETS ARE
PLACED ON PREMOLAR BANDS, TWIN BRACKET ON 1ST
MOLARSAND HEAVY EDGEWISE 0.022
TUBES WITH MESIAL HOOKS ON 2HD MOLARS. THE BANDS HAVE LINGUAL HOOKS ON MOLAR
AND LINGUAL CLEATS ON PREMOLARS
II. ARCHWIRES:
0.017”X 0.022”
0.018”X 0.025”
0.019”X 0.025”
0.020”X 0.025”
0.0215”X 0.025”
III.FIRST, SECOND, AND THIRD ORDER BENDS
AUXILLARIES
.

TREATMENT WITH THE TWEED- MERRIFIELD EDGEWISE :APPLIANCE;
THERE ARE ESSENTIALLY5 CONCEPTS COMPOSING THE TREATMENT PHILOSOPHY
1. SEQUENTIAL BANDING AND BONDING
2. SEQUENTIAL ANDOR INDIVIDUAL TOOTH MOVEMENT
3. SEQUENTIAL MANDIBULAR ANCHORAGE PREPARATION
4. DIRECTIONAL FORCESINCLUDING CONTROL OFVERTICAL DIMENSION, WHICH WILL
ENHANCE MANDIBULAR RESPONSE
1. PROPER TIMING OF TREATMENT
SEQUENTIAL BANDING AND BONDING:
ADVANTAGES:
• LESS TRAUMATIC TO THE PATIENT
• EASIER AND LESS TIME CONSUMING FOR THE ORTHODONTIST
• GREATER EFFICIENCY-GIVES THE ARCHWIRE MUCH LONGER INTERBRACKET LENGTH
• THIS CREATES A POWER STORAGE THAT ACCOMPLISHES TREATMENT OBJECTIVES MOR
RAPIDLY
.

• WIRE OF LARGER DIMENSION CAN BE USED
SEQUENTIAL ANDOR INDIVIDUAL TOOTH MOVEMENT:
IS NOT ENMASSE AS IN TWEED BUT IS SEQUENTIAL
SEQUENTIAL MANDIBULAR ANCHORAGE PREPARATION:
THIS METHOD IS SEQUENTIAL, PRECISE, AND CONTROLLED
.

DIRECTIONAL FORCE
USE OF DIRECTIONAL FORCE SYSTEM IS THE HALLMARK OF TWEED –MERRIFIELD
EDGEWISE TREATMENT
DEFINITION-CONTROLLED FORCES WHICH PLACE TEETH IN THE MOST HARMONIOUS
RELATIONSHIP WITH THEIR ENVIRONMENT
TIMING OF TREATMENT: SHOULD BE INITIATED AT A TIME WHEN TREATMENT OBJECTIVES
CAN BE MORE READILY ACCOMPLISHED.
THE STEPS OF TREATMENT:
THIS TWEED –MERRIFIELD EDGEWISE DIRECTIONAL FORCE TREATMEBT CAN BE ORGANISED
INTO 4 FORCE SYSTEMS
• DENTURE PREPARATION
• DENTURE CORRECTION
• DENTURE COMPLETION
• DENTURE RECOVERY
.

A) DENTURE PREPARATION:
THE BASIC OBJECTIVES
• LEVELLING
• INDIVIDUAL TOOTH ALIGNMENT AND ROTATION CORRRECTION
• CUSPID RETRACTION
• INITIAL PREPARATION OF THE TERMINAL MOLARS FOR STRAIN RESISTANCE.
.
B) DENTURE CORRECTION:
OBJECTIVES
1 .RETRACTION AND UPRIGHTING OF L-INCISORSTO THEIR PLANNED POSITIONS
2 COMPLETION OF SPACE CLOSURE
3 ACHIEVEMENT OF POSTERIOR AND MID-ARCH AXIAL INCLINATIONS THAT WILL PERMIT
4 PROPER FUNTIONAL CO-ORDINATION WITH THE MAXILLARY TEETH
.

-DENTURE COMPLETION:
THE GOALS OF THIS ARE
1. REMOVE ANY FIRST ORDER ASYMMETRIES, EXPANSION OR LACK OF ARCH CO-
ORDINATION
2. CORRECT RESIDUAL ROTATIONS, LACK OF ROOT PARALLELISM, TORQUE DEFICIENCES
AND SPACING
3. POSITION THE MAX. INCISORS WITH ARTISTIC BENDS
4. SEAT THE CUSPS WITH VERTICAL SPURS AND ELASTICS.
AT THE END OF THIS STAGE THE FULL CHARACTERISTICS SHOULD BE READILY OBSERVED
• INCISORS SHOULD BE ALIGNED
• OCCLUSION MUST BE OVER TRAETED TO CLASS I RELATIONSHIP
:
.

• ANTERIOR TEETH MUST BE EDGE TO EDGE
• MAXILLARY CANINES AND 2ND PREMOLARS MUST BE LOCKED INTO A CLASS I
RELATIONSHIP
• M-B CUSP OFMAX 1ST
MOLAR MUST OCCLUDE IN THE M-B GROOVE OF THE MAND 1ST
MOLAR
• DISTAL CUSPS OF THE 1ST
AND 2ND
MOLARS MUST BE OUT OF OCCLUSION
• ALL SPACES MUST BE CLOSED TIGHTLY FROM 2ND
PREMOLAR FORWARD.
D) DENTURE RECOVERY:
THIS IS THE FINAL PHASE OF TREATMENT.
.

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