Contemporary ArchwiresContemporary Archwires

Dr. Firas ElayyanDr. Firas Elayyan

University of ManchesterUniversity of Manchester

Orthodontic ArchwiresOrthodontic ArchwiresKey considerationsKey considerations

11--Stiffness ( Spring rate): Stiffness ( Spring rate): magnitude of force at a magnitude of force at a

given deflectiongiven deflection??

2-Springback ( range of 2-Springback ( range of action): action): Will it deflect Will it deflect that far?that far?

3-Strength: 3-Strength: The highest The highest amount of force delivered amount of force delivered by the wire.by the wire.

Factors affects the force Factors affects the force wire exertswire exerts::

Thickness

Length Material

11--Effect of thicknessEffect of thicknessround wiresround wires

Stiffness is proportional to (diameter)Stiffness is proportional to (diameter)44

DiameterDiameter StiffnessStiffness

1414 1.001.00

1616 1.711.71

1818 2.732.73

2020 4.164.16

Small increment in size= big increment in forceSmall increment in size= big increment in force

14

20

Effect of thicknessEffect of thicknessRectangular wiresRectangular wires

Stiffness is proportional to w x hStiffness is proportional to w x h33

W

h3

19x25 18x25

Stiffness of 19x25 > 18x25

22--Effect of LengthEffect of LengthStiffness is inversely proportional to LStiffness is inversely proportional to L33

SpanSpan StiffnessStiffness66 mm 1.00mm 1.0055 mm 1.73mm 1.7344 mm 3.38mm 3.3833 mm 8.00mm 8.00

22 mm 27.00mm 27.00Critical areas: smallest interbracket spanCritical areas: smallest interbracket span

MaterialsMaterials--Stainless steelStainless steel

--Cobalt ChromiumCobalt Chromium

--Beta-TitaniumBeta-Titanium

--Nickel Titanium alloysNickel Titanium alloys

--Glass OptiflexGlass Optiflex

--Fibre reinforced compositeFibre reinforced composite

0

20

40

60

80

100

120

140

160

SS CoCr TMA NiTi

Range

RangeRange

0

20

40

60

80

100

120

140

160

180

SS CrCO TMA NiTi

Stiffness

Range

Stiffness and Range

StiffnessStiffness

S.S.Stress

Strain

NiTi

The Chronological Development of The Chronological Development of Archwires Archwires ( Evans,1996)( Evans,1996)

Phase lPhase l : : Gold and Stainless steel ( 1900-1960’s)Gold and Stainless steel ( 1900-1960’s)

Phase llPhase ll: : Stabilized NiTi “ Stabilized Martensitic” ( 1970’s)Stabilized NiTi “ Stabilized Martensitic” ( 1970’s) Phase lllPhase lll : : Superelastic NiTi “ Active Austenitic” ( 1980’s)Superelastic NiTi “ Active Austenitic” ( 1980’s)

Phase lVPhase lV : : Thermodynamic NiTi “Active Martensitic”Thermodynamic NiTi “Active Martensitic” ( Early 1990’s)( Early 1990’s)

Phase VPhase V : : Graded thermodynamic ( Late 1990’s)Graded thermodynamic ( Late 1990’s)

Stainless steel archwiresStainless steel archwires

- SS was developed in World War l, only in SS was developed in World War l, only in the 1940’s was introduced to orthodontics.the 1940’s was introduced to orthodontics.

- Very rigid wire, good for space closure but Very rigid wire, good for space closure but not for alignment .not for alignment .

- This was solved by: Wire bending and This was solved by: Wire bending and loops, the use of multistrand SS.loops, the use of multistrand SS.

- Multistrand SS has 20% of the stiffness Multistrand SS has 20% of the stiffness and twice as range as SS.and twice as range as SS.

Development of the Development of the High Technology High Technology

AlloysAlloys

-NiTi alloys were developed in early1960’s for space programs -NiTi alloys were developed in early1960’s for space programs by W.Buehler in USA.by W.Buehler in USA.

-This metal was called “ The Memory Metal”-This metal was called “ The Memory Metal”

--Very complex structure and mechanical behaviorVery complex structure and mechanical behavior..

--Mechanical properties and thermal behavior are highly Mechanical properties and thermal behavior are highly affected by composition, machining characteristics and heat affected by composition, machining characteristics and heat

treatment during manufacturingtreatment during manufacturing..

Shape memory effect (SME)Shape memory effect (SME)!! !!

NiTi TransformationNiTi Transformation

Austenite

Martensite

High Temperature

Low Temperature

TTR

In response to temp variation, the crystal structure undergoes deformations in which the molecular arrangement is modified without a change of atomic composition.

Properties of different phasesProperties of different phases

Austenite NiTiAustenite NiTiMartensite NiTiMartensite NiTi

Crystalline structureCrystalline structureCubicCubicHexagonalHexagonal

Elastic ModulusElastic Modulus 9898 GPaGPa3131 GPaGPa

Yield StrengthYield Strength 379379 MPaMPa138138 MPaMPa

NiTi AlloysNiTi Alloys

--Martensitic NiTi is responsible for the Martensitic NiTi is responsible for the lowering of the delivery forcelowering of the delivery force..

--Austenitic NiTi is responsible for Austenitic NiTi is responsible for elasticityelasticity..

--Modulus of elasticity of Austenitic NiTi Modulus of elasticity of Austenitic NiTi is 3-4 times than Martensitic NiTiis 3-4 times than Martensitic NiTi..

Transitional Transformation Range Transitional Transformation Range (TTR)(TTR)

Temperature

Austenite

0%

100%

NiTi Alloys DevelopmentNiTi Alloys Development

Stage lStage l : Nitinol : Nitinol “Stabilized Martensetic“Stabilized Martensetic ” ”))19701970’’ss((

Stage llStage ll : Superelastic NiTi : Superelastic NiTi “ Active Austenite“ Active Austenite”” ) )Mid 1980’sMid 1980’s((

Stage lllStage lll: Thermal Wires : Thermal Wires “ Active Martensite“ Active Martensite””))Early 1990’sEarly 1990’s((

Stage lVStage lV: Development of Copper NiTi : Development of Copper NiTi “CuNiTi“CuNiTi””))Late 1990’sLate 1990’s((

Stage l: Stabilized Martensetic Stage l: Stabilized Martensetic “ Nitinol“ Nitinol ” ”

--Composed of 55 Ni:45 TiComposed of 55 Ni:45 Ti

--Introduced to Orthodontic by Dr.Andreasen mid Introduced to Orthodontic by Dr.Andreasen mid 1970’s1970’s..

--No shape memory or superelasticityNo shape memory or superelasticity..

--Deformation occurring during processingDeformation occurring during processing

) ) work hardeningwork hardening ( (suppress SMEsuppress SME

--It is passive “ Stabilized” alloyIt is passive “ Stabilized” alloy

Cont. Stabilized Martensitic wiresCont. Stabilized Martensitic wires( Nitinol)( Nitinol)

AdvantagesAdvantages::

--Low stiffnessLow stiffness

) )20%20% of SSof SS((

--SpringySpringy

) ) range 2.5 as SSrange 2.5 as SS((

--Light, continuous and Light, continuous and linear force deliverylinear force delivery..

S.S.

NiTiStress

Strain

Stage ll: Superelastic NiTi Stage ll: Superelastic NiTi (Japanese or Chinese Wires)(Japanese or Chinese Wires)

--Developed by Dr.Burstone and Muira mid 1980’sDeveloped by Dr.Burstone and Muira mid 1980’s

--TTR below room temperature ( Cr, Nb additions)TTR below room temperature ( Cr, Nb additions)

--Active Austenitic at room temperatureActive Austenitic at room temperature

--AAff is lower than oral temperature so no is lower than oral temperature so no

thermoelastic propertiesthermoelastic properties..

SuperelasticitySuperelasticity--Occurs above TTROccurs above TTR

--Wire initially austeniticWire initially austenitic--Only stressed ares Only stressed ares

transform to martensite transform to martensite Stress Induced Martensitic Stress Induced Martensitic Transformation Transformation ( SIMT)( SIMT)..

--Superelasticity only exists Superelasticity only exists when both phases of metal when both phases of metal are presentare present..

--Delivery of forces will be Delivery of forces will be lowered in the needed lowered in the needed areas onlyareas only..

Muira et al. AJODO 90: 1-10; 1986

Advantages of Superelastic NiTi Advantages of Superelastic NiTi archwiresarchwires

--Excellent springback (4-5 of SS)Excellent springback (4-5 of SS)

--Constant forces over large wire deflectionConstant forces over large wire deflection

0 1 2 3 4

0

1

2

3

4

Strain in mm

Sta

nda

rd fo

rce

in N

Activation

Deactivation

SE NiTi wiresSE NiTi wires?? ??

--The slope of the graph The slope of the graph starts with a slope three starts with a slope three

times that of Nitinoltimes that of Nitinol. .

--22 mm deflection is mm deflection is necessary for the necessary for the formation of SIM in formation of SIM in austenitic wiresaustenitic wires

- -Austenitic alloys only Austenitic alloys only behave superelastically in behave superelastically in very severe crowding very severe crowding casescases..

Muira et al. AJODO 90: 1-10; 1986

Effect of heat treatment on SE NiTi Effect of heat treatment on SE NiTi deformationdeformation

Muira et al. AJODO 1986

Stage lll: Thermal WiresStage lll: Thermal Wires(Martensitic Active)(Martensitic Active)

--For the memory property to For the memory property to be clinically detectable, Abe clinically detectable, Aff

has to be slightly below oral has to be slightly below oral temperaturetemperature..

--For every 150 ppm variation For every 150 ppm variation in composition, a 1°C in composition, a 1°C change in TTR occurschange in TTR occurs..

--Mainly Martensitic at room Mainly Martensitic at room temperature-softish, ductile temperature-softish, ductile with shape memorywith shape memory

--Austenitic with SIMT at 37˚ CAustenitic with SIMT at 37˚ C--Deliver 25-30% of the force of SE NiTi and greater range Deliver 25-30% of the force of SE NiTi and greater range

of actionof action . .

Room Temp

Mouth TempAUSTENI

TE

Thermal Wires ( AThermal Wires ( Aff=37°)=37°)

Iijima et al. Dental Material 18 ( 2002) 88-93

Stress

Deflection

60°C

37°C

23°C

Thermal NiTiThermal NiTi

-The main benefit is that these wires generate -The main benefit is that these wires generate lower forces at mouth temperature than the lower forces at mouth temperature than the corresponding size of non-thermal wire.corresponding size of non-thermal wire.

-Allow earlier progression to large dimension -Allow earlier progression to large dimension wireswires e.g. 18x25,20x20.e.g. 18x25,20x20.

-Allow control amount of force delivered to -Allow control amount of force delivered to posterior and anterior teeth.posterior and anterior teeth.

-Allow more severely displaced brackets to -Allow more severely displaced brackets to be engaged by chilling the wire locally. be engaged by chilling the wire locally.

But Thermal wiresBut Thermal wires::

-More expensive.-More expensive.

-Very sensitive to manufacturing process.-Very sensitive to manufacturing process.

-Offer little advantages in small diameters.-Offer little advantages in small diameters.

-May give almost no force in the unloading curve if -May give almost no force in the unloading curve if they are not formulated correctly, so may be they are not formulated correctly, so may be inefficient.inefficient.

-Very sensitive to temperature changes in the oral -Very sensitive to temperature changes in the oral cavity. cavity.

Effect of temperature changes on Effect of temperature changes on thermal archwires during activationthermal archwires during activation

T.Melling and J.Odegaard AJODO 2001; 119: 263-73

Effect of temperature changes on Effect of temperature changes on thermal archwires during deactivationthermal archwires during deactivation

T.Melling and J.Odegard AJODO 2001; 119: 263-73

Effect of repeated short-term Effect of repeated short-term exposure to ice cream on torsional exposure to ice cream on torsional

stiffness of thermal archwiresstiffness of thermal archwires

T.Melling and J.Odegaard Angle Orthod 1998; 68: 369-376

Stage lV: Development of Stage lV: Development of Copper NiTi “’ CuNiTiCopper NiTi “’ CuNiTi””

-5% Copper, 0.2-0.5% Chromium-5% Copper, 0.2-0.5% Chromium-The addition of Cu: -The addition of Cu: Increase strength, reduce energy Increase strength, reduce energy

loss and allows greater loss and allows greater control of TTR.control of TTR.

-Long force plateau-Long force plateau-Better manufacturing consistency-Better manufacturing consistency-Tolerate repeated loading better-Tolerate repeated loading better-3 Types 27°, 35°, 40°.-3 Types 27°, 35°, 40°.

CuNiTi 40°

CuNiTi 35°

CuNiTi 27°

Stress

Deflection

CuNiTi 27CuNiTi 27˚̊

-A-Aff at 27˚. at 27˚.

-Superelastic wire-Superelastic wire- In patients :In patients :

-with average or high pain threshold.-with average or high pain threshold.

-Normal periodontal health.-Normal periodontal health.

-where rapid tooth movement is required -where rapid tooth movement is required

CuNiTi 35CuNiTi 35˚̊

-A-Aff at 35˚. at 35˚.

-Thermoelastic wire-Thermoelastic wire- In patients :In patients : -with low to normal pain threshold.-with low to normal pain threshold. -Normal to compromised periodontal -Normal to compromised periodontal

health.health. -where relative low forces are required -where relative low forces are required

CuNiTi 40CuNiTi 40˚̊

-A-Aff at 40˚. at 40˚.

-Thermoelastic wire-Thermoelastic wire- In patients :In patients :

-who are sensitive to pain .-who are sensitive to pain .

-with compromised periodontal conditions.-with compromised periodontal conditions.- Good as initial rectangular wire.Good as initial rectangular wire.

Stage V: Graded Thermodynamic Stage V: Graded Thermodynamic NiTi archwiresNiTi archwires

--Deliver different amount of force at different Deliver different amount of force at different areas of the dentition according to the areas of the dentition according to the surface area of periodontiumsurface area of periodontium..

- -Controlled by specifying different TTRControlled by specifying different TTR..

--8080 gm of force anteriorly and 300 gm gm of force anteriorly and 300 gm posteriorlyposteriorly..

Beta-Titanium Alloy ( TMA)Beta-Titanium Alloy ( TMA)

--Contains 80% Ti, 11% Contains 80% Ti, 11% Mo, 7% Zr and 4% SnMo, 7% Zr and 4% Sn..

--Medium stiffness ( 1/3 of Medium stiffness ( 1/3 of SS and twice of (Nitinol)SS and twice of (Nitinol)

--Produce gentler linear Produce gentler linear forces than SSforces than SS

--Has more range and Has more range and greater springbackgreater springback

--Has rough surfaceHas rough surface

Stiffness ( Young's Modulus) GPa

Stiffness0 1 2 3 4 5 6

0

20

40

60

80

100

120

140

160

180

SSCoCrTMANiTi

Archwire applicationArchwire application

--Aligning archesAligning arches

--Working archesWorking arches

--Finishing archesFinishing arches

More Stiffness

Less Range

Springback and stiffness ratios of Springback and stiffness ratios of different materialsdifferent materials**

SpringbackSpringbackStiffnessStiffness

Stainless steelStainless steel1111

Multistrand SSMultistrand SS1.5-21.5-2..1313

B-TitaniumB-Titanium1.751.75..3636

NitinolNitinol2.52.5..1717

SE NiTiSE NiTi4-54-5..4141

*Evans (1996), Profit (2000)

Aligning wires needAligning wires need::

--Low stiffness:Low stiffness: low forces on activationlow forces on activation

--High strength:High strength: prevent permanent deformationprevent permanent deformation

--Long working range : Long working range : maximize activationmaximize activation

First aligning wireFirst aligning wireWhich is the bestWhich is the best??--1515 Multistrand SSMultistrand SS

--1212 SE NiTiSE NiTi--1414 SE NiTiSE NiTi--1616 SE NiTiSE NiTi

--1616 ThermalThermal --1818 ThermalThermal

--16x22 Thermal16x22 Thermal--14x25 Thermal14x25 Thermal--20x20 Thermal20x20 Thermal

Physiological Physiological ForceForce?! ?!

Amount of force delivered by wiresAmount of force delivered by wires

16x22 Nitinol16x22 Nitinol307307 gmgm

16x22 NiTi SE16x22 NiTi SE193193 gmgm

16x22 Thermal16x22 Thermal143143 gmgm

16x22 CuNiTi 2716x22 CuNiTi 27˚ ˚ 137137 gmgm

16x22 CuNiTi 3516x22 CuNiTi 35˚̊100100 gmgm

1818 thermalthermal8787 gmgm

1616 NiTi SENiTi SE7373 gmgm

1616 ThermalThermal6060 gmgm

17.517.5 MultistrandMultistrand43.1gm43.1gm

Advantages of NiTi as aligning Advantages of NiTi as aligning archwires compare to Multistrand SSarchwires compare to Multistrand SS::

-Long working range-Long working range

-Damage resistance-Damage resistance

-Sustained forces!-Sustained forces!

-Low Forces-Low Forces!!

Aligning ArchwiresAligning Archwires

--The smallest diameter archwire to be The smallest diameter archwire to be avoided at this stageavoided at this stage: :

- - Small amount of forceSmall amount of force

- - Play between bracket and wires limits Play between bracket and wires limits the accuracy of alignment producedthe accuracy of alignment produced

Inefficient archwire progressionInefficient archwire progression

Multiple round & rectangular wiresMultiple round & rectangular wires

e.g. 12-14-16-18-16x22-18x25e.g. 12-14-16-18-16x22-18x25

Evidence based archwire Evidence based archwire selectionselection

““Clinical trials”Clinical trials”-Superelastic NiTi vs Stabilized NiTi-Superelastic NiTi vs Stabilized NiTiO’Brien et al , EJO 12 ( 1990) 380-384O’Brien et al , EJO 12 ( 1990) 380-384

-Superelastic NiTi vs multistrand steel-Superelastic NiTi vs multistrand steelWest. Jones & Newcombe , AJODO 108 (1995) 464-471West. Jones & Newcombe , AJODO 108 (1995) 464-471

-Thermal NiTi vs graded force NiTi vs multistrand steel-Thermal NiTi vs graded force NiTi vs multistrand steelEvans, jones & Newcombe, AJODO 114 ( 1998) 32-39 Evans, jones & Newcombe, AJODO 114 ( 1998) 32-39

-Superelastic NiTi vs ion implanted NiTi vs multistrand steel-Superelastic NiTi vs ion implanted NiTi vs multistrand steelCobb et al, clin orth Res 1 ( 1998 ) 12-19Cobb et al, clin orth Res 1 ( 1998 ) 12-19

-Does the transition temperature of CuNiTi archwires affect the -Does the transition temperature of CuNiTi archwires affect the amount of tooth movement during alignment?amount of tooth movement during alignment?

Dalstra & Melsen Orthd. Craniof. Res. 7 (2004) 21-25Dalstra & Melsen Orthd. Craniof. Res. 7 (2004) 21-25

Results of clinical trialsResults of clinical trials

- Rates of tooth movement hardly affected Rates of tooth movement hardly affected by type of wire, any difference no clinically by type of wire, any difference no clinically significant.significant.

- Pain experience not affected.Pain experience not affected.- Results are related to the individual Results are related to the individual

variations in variations in metabolic responsemetabolic response within within the periodontal ligaments and bone.the periodontal ligaments and bone.

22--Archwires SequenceArchwires Sequence

-A recent RCT in Manchester by Mandall N. -A recent RCT in Manchester by Mandall N. et al.et al. EJO in pressEJO in press

-Three randomly allocated archwire sequence in -Three randomly allocated archwire sequence in terms of : efficiency, patient discomfort, root terms of : efficiency, patient discomfort, root resorption.resorption.

--A=16 NiTi, 18x25 NiTi ( n=41)A=16 NiTi, 18x25 NiTi ( n=41)--B=16 NiTi, 16 SS, 20 SS ( n= 44)B=16 NiTi, 16 SS, 20 SS ( n= 44)--C=16x22 CuNiTi, 19x25 CuNiTi ( n=44)C=16x22 CuNiTi, 19x25 CuNiTi ( n=44)The endpoint was the passive placement of 19x25 The endpoint was the passive placement of 19x25

SS for at least 4 weeksSS for at least 4 weeks

ResultsResults

-No statistical difference for patient discomfort at -No statistical difference for patient discomfort at hours 4 hrs, 24 hrs, 3 days and 1 week.hours 4 hrs, 24 hrs, 3 days and 1 week.

-Root resorption was not statistically significant -Root resorption was not statistically significant with average root resorpion between .96-1.39 with average root resorpion between .96-1.39 mmmm

Time required to reach the Time required to reach the working archwireworking archwire

Archwire Archwire sequencesequence

Time ( Months)Time ( Months)No of visitsNo of visits

A LowerA Lower

UpperUpper

6.86.8 ) ) 2.52.5((

6.76.7 ) ) 3.53.5((

5.75.7 ) ) 2.12.1((

5.45.4 ) ) 2.12.1((

B LowerB Lower

UpperUpper

9.39.3 ) ) 4.44.4((

7.97.9 ) ) 3.53.5((

7.57.5 ) ) 1.91.9((

7.17.1 ) ) 2.62.6((

C LowerC Lower

UpperUpper

8.38.3 ) ) 4.24.2((

7.17.1 ) ) 3.43.4((

6.46.4 ) ) 2.22.2((

5.95.9 ) ) 2.82.8((

Can Thermal Rectangular wires be Can Thermal Rectangular wires be used as first aligning archwiresused as first aligning archwires??

First aligning archwiresFirst aligning archwires

-Mild crowding:-Mild crowding: 15 Multistrand SS15 Multistrand SS

14 Nitinol14 Nitinol

18 Thermal 18 Thermal

(20x20 CuNiTi)(20x20 CuNiTi)

-Moderate crowding:-Moderate crowding: 16 Thermal16 Thermal

14 SE NiTi14 SE NiTi

-Severe crowding:-Severe crowding: 14 Thermal14 Thermal

12 SE NiTi12 SE NiTi

When to move to the next wireWhen to move to the next wire??

-When the next wire can be engaged in all -When the next wire can be engaged in all the slotsthe slots

-Look at the worst tooth to decide-Look at the worst tooth to decide

-Watch for rotation particularly-Watch for rotation particularly

-Give enough time for the wire to work -Give enough time for the wire to work especially the new high technology wiresespecially the new high technology wires

Second aligning archwireSecond aligning archwire

--18x25 NiTi18x25 NiTi

--20x20 CuNiTi20x20 CuNiTi

Possible uses of 20x20 CuNiTiPossible uses of 20x20 CuNiTi

-Final alignment wire -Final alignment wire after round NiTi wireafter round NiTi wire

-Sole aligning wire for -Sole aligning wire for mild irregularities mild irregularities

( few cases)( few cases)

-Realignment after -Realignment after bracket repairs or bracket repairs or repositioning.repositioning.

Working archwiresWorking archwires

PhotoPhoto

Working arch usageWorking arch usage0.022 slot0.022 slot

Rec SS ( 18x25+) Rec SS (<18x25)Round SSRec NiTi

Percentage of Force loss due to Percentage of Force loss due to FrictionFriction

16x22 archwires, Slot size 18, bracket width 3.3mm ( D.Tidy)

0

10

20

30

40

50

60

70

80

90

SS NiTi TMA

%

Stainless steel working archesStainless steel working arches

-High stiffness-good control-High stiffness-good control

-Easily adjusted -Easily adjusted

-Low friction-Low friction

-Can be welded or soldered-Can be welded or soldered

-Cheap-Cheap

NiTi working archesNiTi working arches

-Flexible- poorer control-Flexible- poorer control

-Difficult to adjust-Difficult to adjust

-Higher friction-Higher friction

-Cannot weld or solder-Cannot weld or solder

-More expensive-More expensive

Finishing archwires (22 slots)Finishing archwires (22 slots)

Loose fitting SSClose fitting SSMultistrand SSOthers

Finishing wiresFinishing wires

Options for close-fitting archwires (21x25)Options for close-fitting archwires (21x25)::

--Steel : Too stiffSteel : Too stiff

--NiTi: Not adjustableNiTi: Not adjustable

Poor torqueingPoor torqueing

--B-Titanium: Ideal stiffnessB-Titanium: Ideal stiffness

used to provide root parallelingused to provide root paralleling

Self-Ligating BracketsSelf-Ligating Brackets??

Self- Ligation

Low Force, Low Friction

Active Ligation High Force, High

Friction

19x25 19x25

Damon 4 Solid Walls

Conventional Wire Out

Of Slot

Elastic Ligature or Metal Clip

What Are The Limitations Of Conventional or Active Ligation?

Poor Control – Less Effective Torque

-Friction is increased 500% over Damon, if -Friction is increased 500% over Damon, if using a conventional bracket with steel using a conventional bracket with steel ligaturesligatures

-Friction is increased 1500% over Damon, if Friction is increased 1500% over Damon, if using an elastic ligatureusing an elastic ligature

-There are 70 grams of frictional force, per There are 70 grams of frictional force, per tooth, when using an elastic ligature tooth, when using an elastic ligature

EJO 2004 KhandyEJO 2004 Khandy

Self-Ligating BracketsSelf-Ligating Brackets

Friction!!Friction!!

0

0.5

1

1.5

2

2.5

3

3.5

4

016 x 022 017 x 025 018 x 025 019 x 025

DAMON SPEED SWA 'O' SWA '8'

Sims, Birnie and Waters (1993)Sims, Birnie and Waters (1993)

Frictional Resistance N/m

Deflection (mm)

0 1 2 3 4

Fo

rce

s (

gra

m)

0

100

200

300

self-ligating bracketsElastomeric ligature

F.Elayyan et al. Angle Ortho ( 2006) , in press

Archwires in Self-Ligating bracketsArchwires in Self-Ligating brackets

--High Technology Wires should be usedHigh Technology Wires should be used

) ) e.g. CuNiTie.g. CuNiTi.(.(

--Smaller dimensions ( Start with 14)Smaller dimensions ( Start with 14)

--Give 10 weeks appointment intervalGive 10 weeks appointment interval..

--Use 14x25 CuNiTi as second aligning archwires Use 14x25 CuNiTi as second aligning archwires to correct rotationsto correct rotations..

- -Then 18x25 CuNiTi to express additional Then 18x25 CuNiTi to express additional torquetorque..

FutureFuture

FutureFiber-reinforced composite Archwires