0.018 Vs 0.022

When there are two orthodontists in a room there will be at

least a minimum of three opinions. There are two slots 0.018” VS

0.022” each of their own pros and cons. This seminar will examine

in a un-biased manner the advantages and disadvantages of each of

these slots in various stages of PAE.

An Edgewise Bracket Design

Edward H. Angle – Edgewise arch mechanism.

Angle’s concept of the “line of occlusion”.

Metal bracket, rectangular slot-0.022 x 0.028”.

Rectangular wire of 0.022” x 0.028”.

Wire was inserted into the bracket in the narrowest or edgewise

position–hence the name EDGEWISE.

EDGEWISE BRACKET DESIGN

Single Width Bracket

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TWIN BRACKET

Junior Twin Standard Twin

Intermediate Twin Extra Wide

Posterior/ Wide Width Curved Base Twin

Primary arch wire bend intended for the most direct

movement of teeth. Secondary arch wire bends – any bend for tooth

guidance that are nor primary bends.

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- Secondary bends are needed to compensate for slot-siting

irregularities caused by bracket design and unreliable bracket-siting

techniques, wire bending and wire forming side effects and

judgement errors in bendings.

Tertiary wire bends – one placed for any reason other than

guidance. Examples are omega loops for stops, loops for increasing

wire flexibility and loops for elastics. Previously the orthodontist,

relied on modification in the arch wire in the form of first, 2 n d , 3 r d

order bends to detail the teeth.

PRIMARY BENDS OF THE ARCH WIRE- EDGEWISE

The first order bends

The second order bends

The third order bends

THE ADVENT OF SWA

The straight wire appliance was based on ANDREW’S six

keys to normal occlusion(1972)

Philosophy – an ideal bracket system.

– an ideal force system .

Advantages

Reduction in wire bending.

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Use of sliding mechanics.

Precision and finishing.

Flexibility of biomechanics.

Multiple bracket design.

Siamese

Single

Mini series

Midi series

Vertical slot

Self ligating

Disadvantages

Friction

Anchorage demands

Deceptive simplicity traps the unwary.

VARIOUS PRESCRIPTIONS AVAILABLE:

Roth

MBT

Alexander

EDGE- WISE PEA

Primary Bends In–Built Priscription

First Order Bends In–Out/ Prominence

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Pre-adjusted appliances build corrections directly into the

brackets.

- Labio-lingual position previously placed into the arch wire

bends are now programmed with the in – out depth of the bracket

slots (or) within the bracket bases

EDGE- WISE PEA

Primary Bends In – Built Prescription

Tip/ Angulation

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Preangualted slots in the brackets provide for precision

mesiodistal angulation.

EDGE- WISE

Primary Bends

Third Order Bends

PEA

In–Built Priscription

Torque/ Inclination

Labio-lingual inclination (or) torque previously managed with

auxiliary torquing appliances and arch wire adjustments are now

provided with accuracy by pre-torqued bracket slot and bases.

THE BIFURCATION OF SWA BASED ON SLOT DIMENSIONS

0.018” and 0.022”

SLOT SIZE: SLOT HEIGHT & SLOT DEPTH

HEIGHT:

The SWA is available with slot heights of 0.022” & 0.018”.

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SLOT DEPTH:

0.022” x 0.028”

0.018” x 0.025”

Rectangular wires in torque applications must be seated with

their outer working edges fully engaged in the slot.

Slots should be deep enough to ensure full engagement.

WIDTH

Proffit

0.018” - Narrow brackets.

Rectangular wires,-when they fill the slot in

later stages are more effective in large inter-bracket span.

Sliding teeth along arch-wire is relatively

unimportant.

0.022” – Wider brackets.

Larger slot provides clearance needed for

sliding

Single width Double width

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Mini Uni - Twin

AUTHORS SUPPORTING THE USE OF 0.022”SLOT

ROTH

Available both in 0.018” & 0.022 slot brackets

His preference is 0.022” slot, based on the

type of mechanics he uses. 0.018 is too restrictive in wire

size selection

He prefers 0.022”in terms of wire selection

stabilizing arches as anchor units, for orthognathic

surgery& for torque control, mainly in the buccal

segments.

M.B.T.

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The larger slot allows more freedom of movement for the

starting wires, keeping the forces light.

Later in treatment, the steel rectangular working wires of

0.019/0.025 have been found to perform well

With the 0.018 slot the main working wire is normally

0.016/0.022 or 0.017/0.025.These wires shows greater

deflection & binding during space closure with sliding

mechanics.

AUTHORS SUPPORTING THE USE OF 0.018” SLOTS

WICK ALEXANDER

• His concept was that 0.022” slot with heavy rectangular

wires was cumbersome for patients.

• He used 0.018” slot with 0.017” wires lighter forces

would result in less patient discomfort .

RICKETTS

• He used the edgewise bracket slot (0.018 x 0.030) to keep

the bracket and wire sizes smaller.

• The deep slot (0.030) permits two light arches to be

employed at once (Base archwire for stabilization & the

auxillary arch or section for rotation or movement).

PLAY (OR) SLOP

• The clearance between the arch wire and bracket.

• Four types of play.

(Straight wire the next generation –AJO 1998)

Torquing play

Play in the tipping plane

Vertical play

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Rotational play

Torquing play – depends on size of rectangular wire relative to the

size of the slot. Most prescriptions have excessive lingual root torque

in the maxillary anterior brackets that may deliver adequate lingual

root torque for retraction movements using less than full-sized arch

wires. Brackets with these excessive torques are incapable of

delivering labial root torque during protraction movements, without

extensive reverse torquing bends in the arch wire.

Play in tipping plane generally depends upon size of the arch-

wire, size of slot and overall width of the slot. Tipping play is less

than torquing play. But if torquing play is minimized by increasing

the arch wire size relative to slot size, then tipping play will be

minimized, regardless of the width of the bracket.

Vertical play

Play in the vertical plane will result in incomplete bracket to

bracket leveling.

Rotational play

Tendency of the tooth to rotate on its own axis. Rotational play

increases narrow bracket, decreases wide brackets. Play can

never be eliminated but can be minimized, in the tipping, torquing

and vertical planes, by “filling” the slot as much as possible.

Rotational play is minimized by using brackets with adequate

rotational lower arm length and ligating with sufficient force to keep

the arch wire seated in the bottom of the slot.

For every .001” difference between arch wire & slot - 4°play.

0.018” slot with 0.018 Wire 0.022” slot with 0.018 Wire

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IN – BUILT TORQUE Vs EXPRESSEDTORQUE

The area of torque application is small.depends on the twist

effect of a relatively small wire compared with the bulk of the

tooth.

.019/.025 steel wires have a slop about 12° in a 0.022 slot.

As a result of the relative inefficiency of pre-adjusted brackets

in delivering torque, it was necessary to built in extra torque

into the incisor, molar& lower premolar brackets

EFFECTIVE TORQUE

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ASPECTS INCORPORATED TO GET THE FULL EXPRESSION

OF TORQUE

• FILL THE SLOT

• INCORPORATE TORQUE INTO THE WIRE

THE THREE STAGES OF TREATMENT

• ALIGNMENT & LEVELING

• RETRACTION & SPACE CLOSURE

• FINISHING

ALIGNING &LEVELING

0.018” SLOT

Proffit prefers round wires for this stage .Says that rectangular

arch wires, particularly those with a tight fit with in the bracket slot,

so that the position of root apex could be affected, normally should

be avoided.

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The principle is that it is better to tip crowns to position during

initial alignment, rather than displacing the root apices, because

rectangular arch wire will create unnecessary and undesirable root

movement during alignment.

0.014 NITI

0.016 NITI

0.016 HANT

16x22 HANT

0.022” SLOT

• 0.015 MULTISTRAND

• 0.0175 MULTISTRAND

• 0.014 SS

• 0.016 SS

• 0.018 SS

• 0.020 SS

• 0.016 HANT

• 19 x 25 HANT

RETRACTION

Individual canine retraction- friction ,frictionless

Enmasse & Anterior retraction –friction, frictionless.

INDIVIDUAL CANINE RETRACTION

• Round wires are preferred than rectangular wires

• Decrease in the contact surface area – less friction

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FRICTION

0.018” Slot

• 0.016 Round SS

• 16 X 22 SS

0.022” Slot

• 0.018 Round SS

• 16 x 22 SS

• 17 x 25 SS

• Tip- edge bracket.

FRICTION-LESS

PG SPRING – 16 X 22 SS wire - 0.018” /0.022” slots.

BURSTONE T-Loop–0.017 x 0.025 TMA wire –0.018”/0.022”.

MARCOTTE SPRING – 0.016 SS wire – 0.018” /0.022”slots.

ENMASSE & ANTERIOR RETRACTION

0.018” Slot

• 16 x 22 SS

• 17 X 23 SS

0.022” Slot

• 18 x 25 SS

• 19 x 25 SS

FINISHING

0.018” Slot

• 17 x 25 NiTi

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• 17 x 25 SS

• 17 x 25 beta Ti

• 17 X 25 Ti Niobium

0.022” Slot

• 21 x 25 NiTi

• 21 x 25 beta Ti

• 21 x 25 M- NiTi

• 21 X 25 Ti Niobium

SURGICAL ORTHODONTICS

Normally it is said that 0.022 slot is preferred for surgical

cases, but

William proffit & Raymond P. White

• 0.018”slot or 0.022” slot can be used

• Rigidity of a 17 x 25 SS wire in a 0.018”is adequate for

stabilization

• One exception where 0.022” is advantageous –when segmented

arch mechanics are needed,-particularly in patients with severe

periodontal breakdown.

• In a 0.022”slot – 21 x 25 TMA / SS

0.018” SLOT

Martin .B. Epstein (AO. Vol.72. 2002)

Advantage

The capacity to fill the slot allows for a greater use of the

prescription built into the bracket.

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Disadvantage

Fewer choices of arch wire dimensions.

0.022” SLOT

Martin .B. Epstein (AO. Vol.72. 2002)

Advantages

Using undersized archwires, one can facilitate free sliding of

the archwire through the slot.

Hence less frictional resistance or binding at the bracket wings.

Larger wires are also useful

Large wires provide increased stiffness & facilitate to keep the

teeth upright during space closure & retraction mechanics.

Robert P. Kusy & John Whitley (EJO 1999)

Smaller brackets requires that the clinician be as much as 25%

more precise in the initial stage or else binding will occur.

This outcome suggests that inexperienced clinicians will find

the 0.022” slot more suitable for sliding mechanics.

To accomplish that “best case” scenario, most easily within the

strength & stiffness requirements of the appliance, the bracket

width & wire size should be small, & the bracket slot should be

large.

Disadvantages

Martin .B. Epstein (AO. Vol.72. 2002)

Disadvantage may be encountered when filling the slot.

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Full sized rectangular wires becomes markedly reduced in

springiness and range,-thereby severly limiting the ability to

place effective torque & finishing bends.

VIEWS OF AUTHORS

Raymond E. Siatkowski. (JCO / Sep. 1999 )

Bracket slot & arch-wire dimensions have caused unpredictable

failures of formerly reliable mechanics,-especially those that

depend on protracting posterior teeth.

This has resulted in lingual tipping of incisors & in general loss

of incisor axial inclination control.

Robert P. Kusy (AJO. Apr. 2002)

In reality manufactures do not provide discrete slot sizes, but

rather a spectrum of slot sizes – 0.0178 to 0.0237.

Angle’s generation necessitated 0.022”, where he used gold

wire.

The SS wires, which displaced gold, permitted the slot to shrink

to 0.018”.

All might have turned okay if technology had not made a hair

pin bend and come full circle to offer a titanium – molybedneum arch

wire alloy with a stiffness close to that of gold.

As a result of which the world according to its preference split

into two

United States-0.022” slot and Europe –0.018”slot.

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Resolution of the “slot – size” issue would simplify biomaterials &

biomechanic’s instruction for graduate residents too.

Lets not once again follow that well worn path as was done for

gold and S.S rather let’s walk the less trodden path that leads to

higher grounds.

Change never comes easy, but this modification is worth every

bit and effort.So let’s pick up one slot size, whatever it is & make it

metric.

CONCLUSION

Sheldon Peck. (AO – 71. 2001)

Experience with earlier manufacturing advances in other fields

shows that the company first to offer a progressive new standard,

becomes the “king of the road”, miles ahead of the latecomers trying

to jump on the bandwagon. With reference to these views of the

different authors, I believe that it would have reached the ears of

manufacturers too, who might have this “spark” of universal metric

system in the pipe line.

Understanding biomechanics is the matter; it is not the slot

dimension which in debate.

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