moving the teeth

ORTHODONTICS BY MBT TECHNIQUE

The straight wire concept

“The birth of a new concept is never an all or none phenomenon. It is a slow evolution with contributions from many. A new principle is an inexhaustible source of new views”

“Nothing in education is more astonishing than the amount of ignorance it accumulates in the form of inert facts.. However , it is the amalgamation of these inert facts, put forward by the genius’ of our profession, that has led to the high standard of the Preadjusted Appliance system which it has acquired today”

“The beauty of this concept is that a more consistent, more ideal result can be obtained with less physical and mental drain on the operator in less overall time and minimal discomfort to the patient.”

www.indiandentalacademy.com

The Straight Wire Concept

“The straight wire concept is not a product of serendipity, but is a poetry in design. It is an appliance fully programmed to combine simplicity and effectiveness required for the road to success”

The genesis of the straight wire appliance was not a result of a single stray discovery, but rather the result of numerous experiments. Many individual innovations were distilled and combined to form this intricate design.


BUILDING TREATMENT INTO EDGEWISE BRACKETS

HOLDAWAY (1952)

PUBLISHED A LANDMARK ARTICLE IN 1952 DESCRIBED 3 USES OF BRACKET ANGULATION

AIDS IN PARALLELING ROOTS ADJACENT TO EXTRACTION SITES

METHOD OF SETTING UP POSTERIOR ANCHORAGE

TO OBTAIN CORRECT AXIAL INLINATIONS.


Stages 0.018” slot 0.022” slot

Leveling 0.016” NiTi 0.016” X 0.022” Thermal NiTi

0.016” NiTi 0.017” X 0.025” Thermal NiTi

Retraction 0.016” X 0.022” SS/TMA 0.017” X 0.025” SS/TMA

Finishing 0.017” X 0.025” SS 0.019” X 0.025” SS

Detailing 0.017” X 0.025” Braided SS 0.019” X 0.025” Braided SS

HOLDAWAY



JOHN STIFTER (1958)

BRACKETS WITH MALE AND FEMALE ATTACHMENT

IVAN LEE(1960)

BRACKETS OF UPPER ANTERIORS AND LOWER POSTERIORS HAD TORQUED SLOTS

JARABACK (1962)

SUGGESTED THAT UPPER ANTERIORS BE TORQUED AND ANGULATED



LAWRENCE F. ANDREWS’ STRAIGHT WIRE APPLIANCE (1976)

2 PRESCRIPTIONS STANDARD (NON EXTRACTION) TRANSLATION (EXTRACTION)


CONCEPT OF THE PEA APPLIANCE

THE CONCEPT OF THE PEA APPLIANCE EVOLVED FROM A SERIES OF 5 STUDIES CONDUCTED BY L.F. ANDREWS.

EXAMINATION OF POST TREATMENT OCCLUSION STUDY OF NATURALLY OCCURING OPTIMAL

OCCLUSION THE SIX KEYS TO OPTIMAL OCCLUSION CROWN MEASUREMENTS COMPARISON OF TREATED AND NATURAL

OCCLUSION


EXAMINATION OF POST TREATMENT OCCLUSION

The first experiment was conducted in 1960

Study models of hundreds of treated cases submitted to the ABO, E. H. Angle Soc and Tweed Foundation considered to be the state of the art in static occlusion in the US.


EXAMINATION OF POST TREATMENT OCCLUSION

All models showed some common trends- Molars were in Class I relationship Incisors were not rotated No overjet/ crossbite

But there were several inconsistencies like- Articulation? Long axes of teeth adjacent to extraction sites Inclinations and angulations varied 2nd molar not included Interdental spacing due to incomplete treatment Rotation of teeth requiring translation No mounting to check functional occlusion Co-Cr coordination


STUDY OF NATURALLY OCCURING OPTIMAL

OCCLUSION 2nd experiment, 1964, Help of

A.G.Brodie (Univ of Illinois) With the presumption that

naturally occuring optimal occlusion is worth emulating.

120 casts of patients with following features-

Never had undergone orthodontic treatment

Well aligned teeth, pleasing appearance

Excellent occlusion Would not benefit from

orthodontic treatment

The facial axis and mid point of clinical crown of each tooth was marked www.indiandentalacademy.com

THE SIX KEYS TO OPTIMAL OCCLUSION

The third and most important experiment in the development of the preadjusted appliance

The 6 keys individually were not new but put together were of special value as-

Complete set of indicators of optim al occlusion. Judged by tangible landmarks Judged from facial/ occlusal view


TERMINOLOGY

Andrews Plane

Clinical Crown


TERMINOLOGY

Crown Angulation

Crown Inclination

FACC

FA Point Class Type


Six Keys Key 1

Molar Interarach relationship

Mesiobuccal cusp of the permanent maxillary molar occludes in the buccal groove of the perm mand molar

Distal marginal ridge of the upper 1st molar occludes with the mesial marginal ridge of the lower 2nd molar

Mesiopalatal cusp of the upper 1st molar occludes in the central fossa of the lower ist molar

Buccal cusps of upper premolars in the embrasures of the lower premolars

Palatal cusps of upper premolars in a cusp-fossa relationship with lower pms

Upper canines in cusp embrasure with lower canines

Upper anteriors overlap the lower anteriors


Six Keys

Key 2

Crown Angulations Essentially all crowns have

positive angulation Gingival potion of FACC distal

to occlusal portion All crowns of tooth type have

similar angulations Tip pattern is consistent for all

individuals Important esp anteriorly


Six Keys

Key 3-Crown Inclination

Maxillary incisors have positive inclination

Mandibular incisors have slight negative inclination

Interincisal angle<180* Max incisor +ve inclination >

mand incisor –ve incl Upper Central> Lateral Upper 345 –ve Upper 67 more –ve Mand= progresively -ve


Six Keys

Key 4-Absence of rotations

Key 5-Tight contacts

Key 6-slight to flat curve of spee


CROWN MEASUREMENTS

4th study involved the measurement of crowns in the sample for-

• Bracket area of tooth type• Vertical crown contour• Crown angulation• Crown inclination• Maxillary molar offset• Horizontal crown contour • Facial prominence• Depth of Curve of Spee


CROWN MEASUREMENTS

Upper 1 2 3 4,5 6Angulation 5 9 11 2 5Inclination 7 3 -7 -7 -9Prominence 2.1 1.65 2.5 2.4 2.9Molar Offset 10* Lower 1 2 3 4,5 6Angulation 2 2 5 2 2Inclination -1 -1 -11 -17,-22 -30Prominence 1.2 1.2 1.9 2.35 2.5Curve of Spee 0-2.5www.indiandentalacademy.com

COMPARISON OF TREATED AND NATURAL OCCLUSION

The 5th study compared 1150 treated cases with the measurements and the six keys.

KEY 1-- Most cases showed Angle’s Class I molar relationship.

However, The distal marg ridge of upper 6 x mmr of lower 7 Pm’s and canines didn’t show a cusp- embrasure

relationship



KEY 2-Values= +/- 2 was considered incorrect91% of cases had 1 or more teeth with incorrect angulationUpper laterals and canines showed –ve angUpper 6 ranged from -ve in non ext to +ve in ext cases

KEY 3-Values +/- 2 was considered incorrectInterincisal angle on FACC > 180* in 78% casesUpper 456 not always -ve



KEY 4-Rotational errors were measured using angle between

contact points and arch form.

Values= +/- 2 was considered incorrect

67% of cases had rotations esp. teeth that were translated

KEY 5-47% showed spacing due to incorrect angulation

KEY 6-56% showed excessive curve of spee


PRINCIPLES

ALL TEETH OF SAME TYPE WERE SIMILAR IN SIZE AND SHAPE

SIZE OF CROWN HAS NO EFFECT ON ANGULATION, INCLINATION OR PROMINENCE

MOST PEOPLE HAVE NORMAL TEETH REGARDLESS OF OCCLUSION

JAWS MUST BE CORRECTLY RELATED FOR OPTIMAL OCCLUSION

DENTITIONS WITH NORMAL TEETH IN JAWS THAR ARE/ CAN BE CORRECTLY RELATED CAN BE BROUGHT TO OPTIMAL OCCLUSION


SHORTCOMINGS OF THE STANDARD EDGEWISE

APPLIANCE

1. BRACKET BASES PERPENDICULAR TO THE STEM

PROBLEMS IN SLOT INCLINATION

PROBLEMS IN OCCLUSO-GINGIVAL POSITION



APPLIANCE2. BRACKETS NOT

CONTOURED OCCLUSO-GINGIVALLY

PROBLEMS IN SLOT INCLINATION

PROBLEMS IN OCCLUSO-GINGIVAL POSITION



APPLIANCE

3. BRACKETS NOT CONTOURED MESIO DISTALLY

PROBLEMS IN SLOT SITING



APPLIANCE

4. SLOTS NOT ANGULATED

EACH CROWN HAS ANGULATION.

WHEN A FULL SIZE WIRE IS INSERTED RESULTANT ANGULATION INCORRECT.

IF BRACKET ANGULATED ONLY 2 POINT CONTACT. www.indiandentalacademy.com


APPLIANCE

5. BRACKETS STEMS OF EQUAL PROMINENCE

6. MAXILLARY MOLAR OFFSET NOT BUILT IN

IST ORDER BENDS REQUIRED.



APPLIANCE7. ANGULAGTION

LANDMARKS DIFFERED LONG AXIS OF CROWN –

NOT VISIBLE LONG AXIS OF TOOTH-

NOT VISIBLE INCISAL EDGE- TOO FAR AWAY,

MAY BE CHIPPED LATERAL CURVEDCUSP TIPS?

MARGINAL RIDGES – TOO FAR AWAY

CONTACT POINTS– NOT VISIBLE



APPLIANCE8. INCLINATION

LANDMARKS DIFFERED

LONG AXIS OF CROWN –NOT VISIBLE

BRACKET HEIGHT FRON CUSP TIP



APPLIANCE8. EXCESSIVE WIRE BENDING REQUIRED TO INITIATE/ MAINTAIN TOOTH MOVEMENT TO COMPENSATE FOR SLOT SITING

ERRORS TO COMPENSATE FOR ERRORS IN WIRE

BENDING TO COMPENSATE FOR SIDE EFFECTS

OFWIRE BENDING



APPLIANCE PRIMARY BENDS

1ST ORDER -46 BENDS2ND ORDER- 3RD ORDER-ERRORS- 30 BENDS

SECONDARY BENDSFOR ERRORS INSLOT SITINGWIRE BENDINGJUDGEMENT

TERTIARY BENDSLOOPS, STOPS ETC


DESIGN FEATURES OF THE NEW APPLIANCE

SLOT SITING FEATURES

CONVENIENCE FEATURES

AUXILLIARY FEATURES



MID TRANSVERSE PLANE THE MID TRANSVERSE PLANE OF THE SLOT, STEM

AND CROWN MUST COINCIDE BASE SHOULD HAVE SAME INCLINATION AS THE

FACIAL PLANE BASE CONTOURED OCCLUSO GINGIVALLY TO

MATCH CROWN CURVATURETHESE FEATURES ELIMINATED-

X 2ND ORDER BENDS FOR OCC-GIN DISHARMONYX 3RD ORDER BENDS FOR INCLINATIONX OTHER BENDS FOR SIDE EFFECTS



MID SAGGITAL PLANE THE MID SAGGITAL PLANE OF THE SLOT, STEM AND CROWN

MUST COINCIDE THE PLANE OF BASE AT BASE POINT SHOULD BE IDENTICAL

TO FACIAL PLANE AT FA POINT BASE CONTOURED MESIODISTALLY TO FIT EACH TOOTH VERTCAL COMPONENTS PARALLELTO EACH OTHER

THESE FEATURES ELIMINATED-X 1ST ORDER BENDS FOR MOLAR OFFSETS AND M-D SLOT

SITINGX 2ND ORDER BENDS FOR OCC-GIN DISHARMONY AND

ANGULATIONX SECONDARY BENDS FOR SIDE EFFECTS



MID FRONTAL PLANE THE MID FRONTAL PLANE OF EACH

SLOT MUST SUPERIMPOSE ON IT’S CROWN’S PROMINENCE PLANE

ALL SLOTS SHOULD HAVE SAME DISTANCE FROM EMBRASURE LINE

THESE FEATURES ELIMINATED-

X 1ST ORDER BENDSwww.indiandentalacademy.com

CONVENIENCE FEATURES

o GINGIVAL TIE WINGS LATERAL TO SEA

NO GINGIVAL IMPINGEMENT EASY LIGATION

o STEMS OF LOWER 456 GINGIVAL

• NO OCCLUSAL INTERFERENCES

o FACIAL SURFACES OF UPPER 123 PARALLEL TO BASES IN TURN PARALLEL TO CROWN FACE

o LIP COMFORT


AUXILLIARY FEATURES

COUNTER BUCCOLINGUAL TIP IN UPPER 6’S COUNTER MESIODISTAL TIP COUNTER ROTATION TRANSLATION BRACKETS MAX TRANSLATION BRACKETS MEDIUM TRANSLATION BRACKETS MIN TRANSLATION BRACKETS POWER ARM


STAGES OF TREATMENT

ANCHORAGE CONTROLLEVELLING AND ALIGNINGOVERBITE/ OVERJET CONTTROLSPACE CLOSUREFINISHING


ANCHORAGE CONTROL WITH THE INCREASE IN THE TIP THERE IS A

GREATER TENDENCY OF THE ANTERIORS TO PROCLINE

UPPER>LOWERSOLUTIONS

OMEGA LOOP STOPS MOLAR TIE BACKS TPA, LINGUAL ARCH, HG CLASSIII ELASTICS ARCH WIRE BENT DISTALLY BEHIND MOLAR


LEVELLING AND ALIGNING

TWO PROBLEMS ASSOCIATED WITH THE PEA

ROLLER COASTER EFFECT

NEED FOR OVERCOMPENSATION


OVERBITE CONTROL

DEEP BITE DUE TO CANINE TIP

A. WHEN CANINES WERE UPRIGHT / DISTALLY TIPPED

B. ROLLER COASTER EFFECT


SPACE CLOSURE

MOST SIGNIFICANTSLIDING POSSIBLE BECAUSE OF THE

STRAIGHT WIRE


FINISHING

FINISHING REQUIRED MINIMAL WIRE BENDING TO COMPENSATE FOR VARIATIONS IN TOOTH SHAPE, SIZE, ERRANEOUS BRACKET POSITIONING OR OVERCORRECTION

TIP CONTROL- ADJUSTMENT MAY BE NEEDED TORQUE CONTROL-NEEDED IN UPPER AND LOWER

INCISORS.

LOWER MOLARS -VE TORQUE, UPPER MOLARS-+VE ROOT TORQUE

ARCH WIDTH ADJUSTMENTS ROTATIONAL CONTROL CURVE OF SPEE CORRECTION


Dr Lawrence F. Andrews developed the straight wire appliance in mid 1970 based on 6 keys

It was a radical step ,offering dual advantage of less wire bending and better quality of finish

•Initial results of SWA were disappointing

•Old mechanics and heavy force levels ,developed for standard edgewise brackets simply did not transfer to the new system

• ROLLER COASTER effect was seen

•Premolars and canines tended to tip and rotate in the extraction sites

FRICTION

Friction is the resistance to motion that exists when a solid

moves tangentially with the respect to the surface of another

solid.

FRICTIONAL FORCE FFR : Is parallel but opposite to the

direction of force (F) causing motion.

The frictional force produced is proportional to the force with

which the contacting surfaces are pressed together and is

affected by the nature of the surface at the interface.

MECHANISM OF ACTION OF FRICTION MECHANICS :

To move a tooth bodily, the force applied has

to pass through the center of resistance of the tooth.

However as the force is applied at the bracket level

of the crown, the concerned tooth experiences both

force and moment.


Moment of force is created in 2 planes of space. One

moment tends to rotate the canine mesial out as the force

application is buccal to the center of resistance and the

other tends to cause distal tipping of the tooth as the point

of force application is occlusal to the center of resistance.


The wire bracket interaction tends to counteract this

moment by applying an opposite moment. When

distal tipping of the crown takes place the M/F ratio

will be around 7:1, the tooth slides along the

archwire till binding occurs between the archwire and

the bracket. This produces a COUPLE at the bracket.

FORCE DELIVERY SYSTEMS IN SLIDING MECHANICS

1. Elastic module with ligature

2. E - chains

3. closed coil springs

4. J - hook head gear

5. Mulligan’s V - bend sliding mechanics (JCO 1980

July 1994 Sep)

6. Employing Tip-edge Bracket on canines

METHODS OF CANINE RETRACTION IN SLIDING MECHANICS

There are two ways in which anterior teeth are

retracted.

1. By retracting the canine first followed by retraction of

other four anteriors enmasse.

2. Enmasse retraction of six anterior teeth.

Among the above mentioned force delivery system,

commonly used are the elastomeric materials and the

closed coil spring.

They are either attached directly to attachments on the teeth

(canine hooks) or more usually to hooks on the archwire

Methods of applying traction to the archwire include

Fabricated tie back loops (in shape of boot or inverted boot)

Soldered brass hooks (0.7mm)

Stainless steel hooks (0.6mm)

Crimpable hooks

Kobayashi hooks

Preposted archwires are also available

FORCE DELIVERY SYSTEM :

ELASTOMERICS:

Composition and structure

Elastomeric modules and E-chains are polyurethanes,

which are thermosetting polymers. The polymers

posses rubber like elasticity and have long chain

which are lightly cross-linked. The cross-links

between chains must be relatively few to facilitate

large extension with no rupture of primary bonds.

2. E – CHAIN (ELASTOMERIC CHAINS)

It was introduced in 1960 and used in orthodontics

for canine retraction, diastema closure, rotation

correction and arch constriction.

Most of the elastomeric chains generally lose 50% -

70% of their initial force during the 1st day of load

application and at 3 weeks retain only 30 – 40% of

their original force.

In view of the wide variation of initial force levels of

different types of power chains, a force gauge should

be used to determine the desired initial force.

To overcome the problem of rapid force decay

rate and provide for a more constant and consistent

force delivery, prestreching of elastomeric chains has

been suggested.

2. E – CHAIN (ELASTOMERIC CHAINS)

CONFIGURATIONS

Elastomeric chains are available in 3

configurations

Closed loop chain

Short filament chain

Long filament chain :

- generally deliver a lower initial force

and exhibit a greater rate of force

decay at the same extension.

CLINICAL CONSIDERATIONS WHEN USING ELASTICS FOR RETRACTION OF CANINES

A common mistake is to change the elastic chain or

module too often, thus maintaining high force levels and

a moment to force ratio that produces distal crown

tipping only. This also causes excessive mesial out

rotation of the canines. Constantly high force levels can

cause excessive hyalinization of the periodontal

ligaments and inhibit direct resorption around the canine.

If the posterior segment undergoes direct bone

resorption at the same time, loss of anchorage may

result. It is therefore recommended that elastic

modules or chain should be changed at an intervals

of 4-6 weeks to optimize sliding retraction of the

canine.

CLINICAL CONSIDERATIONS WHEN USING ELASTICS FOR RETRACTION OF CANINES

Advantages

absorb water and saliva and

permanent staining takes place.

Stretching causes permanent

deformation.

The loss of force (FORCE

DECAY) with time leads to

variable forces levels during the

treatment, this results in

decreased effectiveness.

Disadvantages

Inexpensive,

Relatively hygienic,

Can be easily applied

without arch wire

removal

No patient co-operation

required.

3. CLOSED COIL SPRINGS

Coil springs were introduced to the orthodontic world as early

as 1931. During the manufacturing process, the material is

subjected to winding that includes tensional and torsional

components and hence spring properties may be slightly

different from the wires made from the same material. The

various materials that have been used for making springs are

Stainless steel

NiTi

Co-Cr Ni alloy

b. NiTi closed coil springs

Nickel titanium alloys were introduced to the

dental profession by William. P. Bleur in the

1960's. He demonstrated the unique combination

of properties of shape memory and super

elasticity in addition to low modulus of

elasticity, moderately high strength, high

resilience and less corrosion.

The force degradation is very less due to the low load deflection rate. They deliver constant amount of force till they reach the terminal end of deactivation stage and generally close space with single activation. They are available in lengths of 9 mm and 11 mm.

b. NiTi closed coil springs

ADVANTAGES OF NITI COIL SPRINGS

Can be easily placed and removed without archwire removal

Do not need to be reactivated at each appointment Patient co-operation not required.

DISADVANTAGES Relatively unhygienic compared to elastic force

systems.

EFFECTS OF OVERLY SPACE CLOSURE:

Space closure typically occurs more easily in high angle patterns with weak musculature. The rate of closure can be increased either by increasing the force or using thinner arch wire. However more rapid space closure leads to

loss of control of torque, rotation or tip

Loss of control of torque

results in upper incisors being too upright at the end of

space closure with the spaces distal to the canines and

a consequent unesthetic appearance. The lost torque is

difficult to regain. Also, rapid mesial movement of the

upper molars can allow the palatal cusps to hang down,

resulting in functional interferences, and rapid

movement of the lower molars causes “rolling in “.

Loss of control of torque

Reduced rotation control

can be seen mainly in

the teeth adjacent to

extraction sites, which

also tend to roll in if

spaces are closed too

rapidly.

Reduced tip control

produces unwanted movement of canines, premolars, and

molars, along with a tendency for lateral open bite. In high-

angle cases, where lower molars tip most freely, the elevated

distal cusps create the possibility of a molar fulcrum effect. In

some instances, excessive soft-tissue hyperplasia occurs at the

extraction sites. This can prevent full space closure or allow

spaces to reopen after treatment. Local gingival surgery may be

necessary in such cases.

INHIBITORS TO SLIDING MECHANICS

1. Occlusal interference - To prevent this proper aligning

and leveling of the arches is required.

2. Friction and binding between bracket and archwire

may place heavy demand on anchorage.

3. Poor canine control can be a problem : Doing canine

retraction on heavier arch wire reduces the problem.

4. Cortical plate resistance (Narrowing of alveolar bone in extraction

sites)

5. Excessive forces causes lower molar tipping and extrusion of

distal cusps

6. Soft tissue build up in the extraction site can prevent space closure

(or) reopen spaces after treatment.

7. Rotation of canines mesio-bucally and molar mesiopalatally.This

occurs due to the use buccal traction. It can be prevented

simultaneous palatal traction using lingual cleats or buttons.

INHIBITORS TO SLIDING MECHANICS

moving the teeth

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