2015_ajodo_magno et al_effect of the clinical use of niti coil

7182019 2015_AJODO_Magno Et Al_Effect of the Clinical Use of Niti Coil

httpslidepdfcomreaderfull2015ajodomagno-et-aleffect-of-the-clinical-use-of-niti-coil 17

Effect of clinical use of nickel-titanium springs

Amanda Fahning Magnoa Andre da Costa Moninia Marisa Veiga Capelab Lıdia Parsekian Martinsc

and Renato Parsekian Martinsd

Ribeir ~ao Preto and Araraquara S ~ao Paulo Brazil

Introduction Our objectives were to determine whether there are changes on the load de 1047298ection rate (LDP)

and the average force (FP) of the superelastic pseudoplateau and whether permanent deformation is changed

in nickel-titanium closed-coil springs (CCSs) after 6 months of clinical use Methods Twenty-two nickel-titanium

CCSs (Sentalloy 100 g Dentsply GAC York Pa) were subjected to tensile mechanical testing at 37C on

activations varying from 32 to 160 mm before and after 6 months of clinical use A regression line was 1047297tted

over the most horizontal area of the unloading part of the stress-strain graph of every CCS and its slope was

used as LDP The FP was determined by the midpoint of the longest segment of the curve that could be 1047297t

within the regression line with a R 2 of at least 0999 and permanent deformation was determined graphically

by obtaining the strain value when the measured stress reached zero The data were analyzed by 3 analyses

of variance at 2 levels with 5 of signi1047297cance Results Time and activation signi1047297cantly in1047298uenced the vari-ables tested (P 0001) Time increased the LDP and permanent deformation but decreased the FP Activation

decreased LDP FP and permanent deformation Signi1047297cant interactions between time and activation were de-

tected for FP (P 5 0013) and deformation (P 0001) Conclusions After 6 months of active clinical use the

analyzed springs had a signi1047297cant but small increase in their LDP FP dropped up to 88 and the CCSs

deformed up to 126 mm (Am J Orthod Dentofacial Orthop 201514876-82)

Ef 1047297cient orthodontic space closure must be care-fully planned and should be conducted with aknown force system1 One method of space

closure is through sliding mechanics and chain elastics

or closed-coil springs (CCSs) of stainless steel ornickel-titanium2 The use of nickel-titanium springshas been suggested as an alternative to elastomericproducts because they produce faster rates of spaceclosure3-7 as a result of the constant forces produced

by their superelasticity8

When enough stress is applied to nickel-titanium

alloys it can induce a transformation in its crystallo-graphic structure from an austenitic phase to a

martensitic phase called stress-induced martensite When a stress-induced martensite transformation occursand a reverse transformation takes place upon removalof the stress a straight and near-1047298at area (called a pseu-

doplateau) occurs on its stress-strain graph thus it issaid that superelasticity occurred89

During orthodontic treatment it is desired for anickel-titanium CCS to be superelastic producing alow elastic modulus a mostly constant force and nodeformation89 Normally there should be no concernsabout permanent deformations because the literature

reports activations of up to 500 of the originallength of the CCSs without deformation10 However itis unclear whether CCSs undergo permanent deforma-tion with clinical use since springs made of other alloysdo exhibit stress relaxation11

Despite being nearly constant the forces generated by nickel-titanium appliances in general may vary over

time because of a phenomenon known as stress relaxa-tion1213 Some authors have observed a time-dependentpermanent deformation in nickel-titanium archwiresdecreasing the forces produced914-16 It has also been

reported that nickel-titanium wires show a higher pro b-ability of fatigue17 and exhibit changes in their surface18

after clinical use but changes of their mechanical prop-erties remain contro versial Although 1 in-vitro study 19

and 1 in-vivo study 20 showed that recycled archwiresare less superelastic other in-vitro studies observed no

a Private practice Ribeir~ao Preto S~ao Paulo Brazil b

Professor Faculdade de Quımica de Araraquara Universidade Estadual Paulista

Araraquara S~ao Paulo Brazilc Professor Faculdade de Odontologia de Araraquara UniversidadeEstadual Pau-

lista Araraquara S~ao Paulo Brazild Private practice adjunct professor Orthodontics Graduate Program Faculdade

de Odontologia de Araraquara Universidade Estadual Paulista Araraquara S~ao

Paulo Brazil

All authors have completed and submitted the ICMJE Form for Disclosure of

Potential Con1047298icts of Interest and none were reported

Address correspondence to Renato Parsekian Martins Rua Voluntarios da Patria

1766 ap 12 Centro Araraquara S~ao Paulo CEP 14801-320 Brazil e-mail

dr_renatopmartinshotmailcom

Submitted February 2014 revised and accepted February 2015

0889-5406$3600

Copyright 2015 by the American Association of Orthodontists

httpdxdoiorg101016jajodo201502028

76

ORIGINAL ARTICLE



signi1047297cant differences in mechanical properties2122

Regarding nickel-titanium CCSs the authors of severalin-vitro studies21223-26 evaluated the forces produced

by them in a simulated oral environment but similarly

the results are controversial with increases

25

decreases21223 and no differences2426 of the forcesover time suggesting that an in-vivo clinical study is

necessary to bring new light to this controversyIt is clinically important to have as much information

as possible on the mechanical properties of nickel-titanium CCSs over time speci1047297cally on the elasticmodulus the average force level used and the perma-nent deformation of these devices This would allowthe clinician to know whether a nickel-titanium CCS

should be replaced or even whether it could be recycled but there is no in-vivo research evaluating the effects of time and use on CCSs Therefore the aims of this study

were to determine the changes that occur in the load-

de1047298ection rate of the superelastic pseudoplateau(LDP) the average force of the superelastic pseudopla-teau (FP) and the permanent deformation of nickel-titanium CCSs after clinical use

MATERIAL AND METHODS

The sample for this prospective study was composedinitially of 50 nickel-titanium CCSs (Sentalloy 100 g

Dentsply GAC York Pa) which were to be used in a ran-domized clinical trial for canine retraction

Before clinical use a mechanical testing machine(DL 2000 EMIC S~ao Jose dos Pinhais Brazil) was

used to test the springs to determine their LDP rates FP and permanent deformation The springs and thehooks that attached them to the machine were sub-mersed in 37C 6 1C of distilled water which was

temperature controlled with a 30-W heater and a ther-mostat27-29

The mechanical test activated the springs to 32 mm(act1) returning them to their initial position (zero) andthen activating them to 64 mm (act2) 96 mm (act3)128 mm (act4) and 1047297nally 160 mm (act5) always re-

turning to the initial position between activationsTo ensure correct activations any possible initial

looseness of the springs was avoided by adjustingthem in increments of 01 mm manually with the digitalindicator of the testing machine before the test startedThe software Tesc (version 304 EMIC) recorded all force

values during the test expressed in raw data format at a

rate of 20 mm per minute No spring showed permanentdeformation after the tests They were properly identi-1047297ed so that the values of the 1047297rst (T1) and second (T2)tests made after clinical use would correspond to thesame springs

To collect the variables stress raw data of each spring were exported to Excel (Microsoft Redmond Wash) Alinear regression was 1047297tted in the most horizontal areaof the stress-strain graph on deactivation to allow thedetermination of the superelastic pseudoplateau Two

points were chosen to determine the beginning andthe end of the pseudoplateau which was the longest

segment of the stress-strain graph explained by theregression line with a coef 1047297cient of determination notless than 0999 The modulus of elasticity of the supere-lastic pseudoplateau (LDP) was determined by the slope

of the regression line ( Fig 1) FP was determined by themidpoint of the superelastic pseudoplateau and perma-

nent deformation was determined graphically at eachstress-strain curve by obtaining the de1047298ection value(variable x) when the amount of force (variable y)reached zero ( Fig 2)

The 50 CCSs tested were then used for canine retrac-tion in 25 patients They were activated by 17 mm (twicethe total length of 85 mm) and were reactivated to thesame length every month After 6 months of treatment22 springs were selected for a second test which wascarried out with the same parameters as the 1047297rst Only 22 springs were tested because the remaining springs

were still in use in the clinical trial after 6 months The22 springs used for the test at T2 showed no visible signsof permanent deformation after clinical use

Because the data collected before and after treatment were normally distributed the SPSS statistical software

Fig 1 Stress-strain graph showing the deactivation of a

nickel-titanium spring The regression line (black ) wasused to identify the more horizontal area of the graph

and to determine LDP (using its slope) The green arrows

show the initial and 1047297nal points chosen to determine the

clinical superelastic pseudoplateau (red ) the midpoint

of that segment (yellow arrow ) is the force variable

measured (FP) in this study

Magno et al 77

American Journal of Orthodontics and Dentofacial Orthopedics July 2015 Vol 148 Issue 1



(version 160 SPSS Chicago Ill) was used to perform 3analyses of variance (at 2 levels) with a signi1047297cance levelof 5 The tests were used to determine differences be-tween times and activations as well as to identify apossible interaction between these 2 factors in the vari-ables LDP FP and permanent deformation

RESULTS

Clinical use (time) signi1047297cantly in1047298uenced the LDPof the springs (P 0001 Table I) When their total pro-1047297le was evaluated the average LDP increased from T1(042) to T2 (053) Activation also in1047298uenced LDP

(P 0001 Table II) The Tukey post hoc test showedthat LDP values were different at act1 (011 Nmm)

and act2 (005 Nmm) but they were the same at act3(003 Nmm) act4 (002 Nmm) and act5 (002 Nmm)(Table II) No interaction was detected between timeand activation in LDP (P 5 0721)

Time signi1047297cantly in1047298uenced the FP when the overallpro1047297le of the springs was evaluated (P 0001 Table I)

with FP decreasing from T1 (106 N) to T2 (016 N)(Table I) Activation also signi1047297cantly affected the FP(P 0001 Table II) The means of the FP were equalin act1 (061 N) act2 (062 N) act3 (061 N) and act4

(065 N) decreasing in act5 (054 N) (Table II) A signif-icant interaction was found between the activation andtime factors in variable FP (P 5 0013 and P 0001respectively)

Time in1047298uenced signi1047297cantly the permanent defor-mation of the springs (P 0001 Table II) When thesprings were evaluated for deformation the total perma-

nent deformation increased from T1 (022 mm) to T2(115 mm) (Table I) Permanent deformation was alsoin1047298uenced by activation (P 0001 Table II) with

values gradually becoming different from 028 mm atact1 049 mm at act2 061 mm at act3 084 mm at

act4 and up to 126 mm at act5 (Table II) A signi1047297cantdifference was also detected between time and activa-tion in the variable of permanent deformation(P 0001)

DISCUSSIONClinical use increased the elastic modulus of the

CCSs This means that ldquoas-receivedrdquo CCSs have a moreconstant deactivation when stress-induced martensiteis transformed back into austenite (when it is superelas-tic) than do used CCSs ( Fig 3) In addition it was found

that the LDP decreased with activation meaning thatthe CCSs produce a more constant force in larger activa-

tions an effect that has already been substantiated inthe literature28 Even though it appears that the differ-ences in the LDP between T1 and T2 increase withactivations ( Fig 4 Table III) we did not have enough

power (0172) to detect interactions This is clinically important because although there is no signi1047297cant dif-ference in LDP caused by time in a small activation(32 mm) brand-new CCSs deliver a much more constantforce than used ones in the normal range of activations(64-160 mm) No clinical studies have analyzedchanges in superelastic properties in nickel-titanium

CCSs over time however an in-vitro study analyzednickel-titanium CCSs after prolonged activation andthermocycling mimicking a clinical situation but noapparent changes in those properties were found26

Even though these results disagree with our 1047297ndings

Table I Means and standard deviations of the springs before and after use regardless of the activationmeasured where the effect of time alone is seen on

LDP FP and permanent deformation

Group LDP (SD) FP (SD) Deformation (SD)

T1 042 (004) 106 N (007) 022 mm (013)

T2 053 (004) 016 N (011) 115 mm (132)

P 0001 0001 0001

Fig 2 The measured permanent deformation data

determined by obtaining the value on the x-axis of the

stress-strain graph when the force registered was 0 N

on the deactivation curve of each spring

Table II Means and standard deviations of the springsat the different activations measured the effect of activation alone regardless of the time of the evalua-tion is seen on LDP FP and permanent deformation

Activation LDP (SD) FP (SD) Deformation (SD)

Act1 (32 mm) 011A (002) 061 NA (049) 028 mmA (024)

Act2 (64 mm) 005 B (002) 062 NA (047) 049 mmAB (044)

Act3 (96 mm) 003C (001) 061 NA (046) 061 mmAB (065)

Act4 (128 mm) 002C (001) 065 NA (044) 084 mm BC (100)

Act5 (160 mm) 002C (001) 054 N B (044) 126 mmC (182)

P 0001 0001 0001

Different letters indicate differences between groups

78 Magno et al

July 2015 Vol 148 Issue 1 American Journal of Orthodontics and Dentofacial Orthopedics



the CCSs were not used clinically as we have done andtheir laboratory simulation may not accurately representan in-vivo situation

We activated the CCSs at 32 64 92 128 and160 mm (act1-act5) because those values are multiplesof the length of nickel-titanium coil that is functional

(32 mm) when an 85-mm (10-mm-long advertisedlength) CCS is activated The maximum activation that

we used was 16 mm or 500 of 32 mm this adds upto 245 mm of total length of the CCS activated(16 1 85 mm) This activation is only 15 mm greater

than the average distance from the maxillary caninesto the 1047297rst molars which is 23 mm and could be easily

reached in patients with larger teeth or when a CCS issecured from the second molars to an archwire hookdistal to the canines30 This percentage used shouldnot be confused with activations in relation to the

percentage of the total length of the CCS which isusually used in the literature to quantify activation10

Using the latter would result in unrealistic activationranges intraorally additionally it would not makepractical sense because those percentages wouldinclude areas of the CCS that do not have superelastic

properties such as the stainless steel eyelets or someamount of nickel-titanium that is not in use when aCCS is activated

There was a signi1047297cant decrease of FP with the clin-ical use of CCSs that may have occurred f rom stressrelaxation1112 since permanent deformation31 did nottake place (the CCSs showed no apparent signs of elon-

gation before their second evaluation after clinical use)The literature is controversial on force changes in nickel-titanium CCSs after prolonged activation in a simulatedoral environment One study reported increased force25

others reported decreased force21223 and others

reported no change2426 The differences betweenmethods may have caused these differences such as

inclusion of thermocycling26 or not21223-25 using thesame samples2232526 or using different samples in

evaluations over time24 Finally the CCSs were evaluateddynamically in some studies122426 and statically inothers22325 Compared with those previous studiesour 1047297ndings present more reliable data because ours

was an in-vivo study Moreover we used a methodology already established for determining the force of CCSstaking into account the superelastic pseudoplateau intheir deactivation curve283233 This is important

because the nonlinear stress-strain ratio of superelasticalloys makes the prediction of mechanical properties of nickel-titanium CCS complex34 From a clinical point

of view the reduction of forces of a CCS may cause toothmovement to slow down or even stop completely if forces fall to suboptimal levels This situation can forcethe orthodontist to change the CCS or modify the strat-egy of space closure

Table III Means and standard deviations of the LDPat different times and activations

Activation T1 (SD) T2 (SD) P

Act1 (32 mm) 011 (0016)Aa 012 (0031)Aa 0361

Act2 (64 mm) 004 (0008) Ba 005 (0019) Bb 0016

Act3 (96 mm) 003 (0005)Ca 003 (0015)Cb 0009

Act4 (128 mm) 002 (0004)Ca 003 (0014)Cb 0001

Act5 (160 mm) 001 (0003)Ca 003 (0013)Cb 0001

P 0001 0001

Different capital letters indicate differences between activations and

different lowercase letters indicate differences between times

Fig 4 Graph depicting the LDP values of the differenttimes taken at different activations

Fig 3 Graph depictingthe LDP values of all 5 activations

taken at different times

Magno et al 79




FP values were also different with increasing

activations with lower forces on the highest activation(Table IV) The effect of stress on austenitic to martens-itic transformation and on its reversal allowing the use of

the superelastic pseudoplateau in orthodontics hasalready been described and CCSs provide better proper-ties at higher activations912 The distances used in this

study were clinically usable distances but if theclinician desires to further explore the potential of nickel-titanium a CCS should be overactivated duringits attachment to the appliance12 If the clinician has asmall distance between attachments he or she could al-

ways secure 1 side of the CCS 1047297rst activate the spring by 16 mm and then allow it to return to its original size

before securing it to the other attachment A signi1047297cantinteraction was also found between time and activationof the CCSs for the FP ( Fig 5) meaning that the patternof force variation was different for different activations

when comparing the 2 times (Table IV) Whereas thereis a tendency for the FP to decrease with greater activa-tions on a new CCS the FP is more or less stable in usedCCSs ( Fig 5) Clinically the reduction of up to 88 in the

FP of nickel-titanium CCSs after clinical use changes theforces initially planned by the orthodontist and could

result in a force level that is too low Despite the many in-vitro studies that have evaluated

superelastic materials laboratory simulations are notcomparable with the oral environment The main factorsthat distinguish the oral cavity from the in-vitro environ-

ment are the presence of complex oral 1047298ora and their by-products the accumulation of plaque on the mate-

rials tested35 and the mechanical effects of oral func-tion In most cases in-vitro material studies providedifferent results from what is observed in in-vivo studiesshowing no evidence of a pattern of intraoral deteriora-

tion and associated phenomena such as surfacechanges or structural and mechanical property

changes35 The observations in LDP and FP show signif-icant changes in the mechanical properties in the oralenvironment after 6 months ( Fig 6) These 1047297ndings agree

with 2 clinical studies that analyzed used nickel-

titanium archwires and found a higher probability of archwire fracture caused by fatigue17 loss of superelas-ticity20 and changes in the topography and surfacestructure of wires from localized corrosion andformation of organic compounds in1047298uencing the super-1047297cial roughness and consequently the mechanicaleffectiveness18

Permanent deformation increased in the CCSs testedafter 6 months of clinical use In-vitro studies designedto simulate an oral environment found some changesin the mechanical properties of nickel-titanium CCSsover time however no one has evaluated whether there

was any difference in their elastic recovery capabil-ities21223 This can in1047298uence signi1047297cantly the clinical

use of these CCSs because the loss of the elasticrecovery may decrease or cause teeth not to move atall if the force falls to suboptimal levels10

The permanent deformations in superelastic alloys

may result from stress relaxation plastic deformationand reversible martensitic deformation caused by stabi-lization of the martensitic phase Although some in-vitrostudies observed a time-dependent permanent deforma-tion in nickel-titanium wires at different times914-16 thedeformations found in this study may have occurred

because of reversible martensitic deformations since

the CCSs were activated below the elastic limit 1047297 xed inthe literature at 500 of the original size10 and becausethe initial tensile tests (T1) of the CCSs showed no signsof permanent deformation This effect was caused by theuse of CCSs in the oral cavity where they were subjected

Table IV Means and standard deviations of FP indifferent times and activations and percentages of reduction of FP between T1 and T2

Activation T1 (SD) T2 (SD)Reduction

T1 T2 ()

Act1 (32 mm) 109 N (007)Aa 013 N (008)Ab 8807

Act2 (64 mm) 108 N (005)Aa 016 N (010)ABb 8519

Act3 (96 mm) 106 N (005)Aa 017 N (011)ABb 8396

Act4 (128 mm) 107 N (005)Aa 022 N (013) Bb 7944

Act5 (160 mm) 097 N (004) Ba 011 N (009)Ab 8866



Fig 5 Graph depicting the average force of the clinical

superelastic pseudoplateau (FP) of the springs obser-

ved at the different activations before and after use (in

Newtons)

80 Magno et al




to degradation of structure changes in temperature and

ldquocold workrdquo due to masticatory forces All of these fac-

tors may have caused changes in the transition temper-atures of the alloy a factor related to reversiblemartensitic deformation1936

Activation also in1047298uenced the permanent deforma-tion of the CCSs this increased progressively withincreasing activations ( Fig 7) We found that clinicaluse affected permanent deformation and its effect

became greater as the amount of activation increased(Table V) More importantly that effect was greatest atthe activations normally used (act4 and act5) whichalso showed low LDP rates and stable FP and aremore practical because they correspond approximately

to the distance between the 1047297rst molars and the canines

Although it is known that cyclic stresses in nickel-titanium could generate a residual permanent deforma-tion which would confuse the results31 this did notoccur in the T2 test otherwise it would have happened

in T1 when the CCSs were also subjected to cycles of activation Despite the increase in permanent deforma-tion the CCSs probably were not plastically deformedat T2 because there was no plastic deformation at T1Therefore what probably occurred was an increase inthe reversible martensitic deformation with the increasedactivations

The long-term use or recycling of nickel-titaniumCCSs is inadvisable because of their degradations insuperelastic properties changes in force and decreasedelastic recovery Clinically our 1047297ndings do not supportthe reuse of nickel-titanium CCSs because they lose

Fig 6 Stress-strain graph showing the different activations of a typical spring before and after use The

force degradation (since the entire plot is lower at T2 than at T1) and a slight increase in the slope of the

superelastic pseudoplateaus (since the recovery curves tend to 1047298atten producing a steeper or lesshorizontal pseudoplateau) can be observed

Fig 7 Graphof the permanent deformation of the springs

taken at different activations before and after use (in mil-

limeters)

Table V Means and standard deviations of the per-manent deformation of springs at different timesand activations and percentages of increased defor-mation between T1 and T2

Activation T1 (SD) T2 (SD)

Increase T1 T2

()

Act1 (32 mm) 020 mm (014)Aa 036 mm (030)Aa 800 NS

Act2 (64 mm) 022 mm (014)Aa 068 mm (051)ABa 2091 NS


Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952



NS Nonsigni1047297cant value

Magno et al 81




the ability to return to their original shape What is still

lacking in the literature however is further research todetermine what changes occur in the transition temper-atures of nickel-titanium alloys in the oral cavity and

what percentage of permanent deformation after clinicaluse of these CCSs is caused by reversible martensiticdeformation or permanent residual deformation Clini-

cians should understand the limitations of these mate-rials and modify their expectations by monitoring theprogress of treatment accordingly

CONCLUSIONS

After 6 months of clinical use the nickel-titanium

CCSs showed signi1047297cant decay of their properties whereas LDP showed only a slight increase the supere-

lastic force pseudoplateau decreased up to 88 and

there were signi1047297

cantly greater permanent deformations(up to 126 mm)

REFERENCES

1 Heo W Nahm DS Baek SH En masse retraction and two-step

retraction of maxillary anterior teeth in adult Class I women A

comparison of anchorage loss Angle Orthod 200777973-8

2 Santos AC Tortamano A Naccarato SR Dominguez-

Rodriguez GC Vigorito JW An in vitro comparison of the force

decay generated by different commercially available elastomeric

chains and NiTi closed coil springs Braz Oral Res 20072151-7

3 Bennett JCMcLaughlin RPControlled space closure with a pread-

justed appliance system J Clin Orthod 199024251-60

4 Dixon V Read MJ OBrien KD Worthington HV Mandall NA A

randomized clinical trial to compare three methods of orthodontic

space closure J Orthod 20022931-6

5 Samuels RH Rudge SJ Mair LH A comparison of the rate of space

closure using a nickel-titanium spring and an elastic module a

clinical study Am J Orthod Dentofacial Orthop 1993103464-7

6 Sonis AL Comparison of NiTi coil springs vs elastics in canine

retraction J Clin Orthod 199428293-5

7 Sueri MY Turk T Effectiveness of laceback ligatures on maxillary

canine retraction Angle Orthod 2006761010-4

8 Miura F Mogi M Ohura Y Hamanaka H The super-elastic prop-

erty of the Japanese NiTi alloy wire for use in orthodontics Am

J Orthod Dentofacial Orthop 1986901-10

9 Burstone CJ Qin B Morton JY Chinese NiTi wiremdasha new ortho-

dontic alloy Am J Orthod 198587445-52

10 Miura F Mogi M Ohura Y Karibe M The super-elastic Japanese NiTi alloy wire for use in orthodontics Part III Studies on the Jap-

anese NiTi alloy coil springs Am J Orthod Dentofacial Orthop

19889489-96

11 Caldas SG Martins RP Viecilli RF Galvao MR Martins LP Effects

of stress relaxation in beta-titanium orthodontic loops Am

J Orthod Dentofacial Orthop 2011140e85-92

12 Manhartsberger C Seidenbusch W Force delivery of Ni-Ti coil

springs Am J Orthod Dentofacial Orthop 19961098-21

13 Hazel RJ Rohan GJ West VC Force relaxation in orthodontic arch

wires Am J Orthod 198486396-402

14 Hudgins JJ Bagby MD Erickson LC The effect of long-term

de1047298ection on permanent deformation of nickel-titanium arch-

wires Angle Orthod 199060283-8

15 Wong EK Borland DW West VC Deformation of orthodontic

archwires over time Aust Orthod J 199413152-8

16 Al-Jwary E Factors affecting on permanent deformation of ortho-

dontic arch wires (an in vitro study) Al-Ra1047297dain Dent J 201111

317-22

17 Bourauel C Scharold W Jager A Eliades T Fatigue failure of as-received and retrieved NiTi orthodontic archwires Dent Mater

2008241095-101

18 EliadesT Eliades G Athanasiou AEBradley TGSurface character-

ization of retrieved NiTi orthodontic archwires Eur J Orthod 2000

22317-26

19 Gil FJEspinar E Llamas JMManeroJM GinebraMP Variationof

the superelastic properties and nickel release from original and

reused NiTi orthodontic archwires J Mech Behav Biomed Mater

20126113-9

20 Kapila S Reichhold G Anderson R Watanabe B Effects of clinical

recycling on mechanical properties of nickel-titanium alloy wires

Am J Orthod Dentofacial Orthop 1991100428-35

21 Ramazanzadeh BA Ahrari F Sabzevari B Zebarjad SM Ahrari A

Effects of a simulated oral environment and sterilization on

load-de1047298ection properties of superelastic nickel titanium-basedorthodontic wires Int J Orthod 20112213-21

22 LeeSH Chang YIEffects of recycling on the mechanical properties

and the surface topography of nickel-titanium alloy wires Am


23 Angolkar PV Arnold JV Nanda RS Duncanson MG Force degra-

dation of closed coil springs an in vitro evaluation Am J Orthod

Dentofacial Orthop 1992102127-33

24 Han S Quick DC Nickel-titanium spring properties in a simulated

oral environment Angle Orthod 19936367-72

25 Nattrass C Ireland AJ Sherriff M The effect of environmental fac-

torson elastomeric chain andnickel titanium coil springsEur J Or-

thod 199820169-76

26 VidoniG Perinetti G Antoniolli F CastaldoA ContardoL Combined

aging effects of strain and thermocycling on unload de1047298ection

modes of nickel-titanium closed-coil springs an in-vitro compara-

tive study Am J Orthod Dentofacial Orthop 2010138451-7

27 Maganzini AL Wong AM Ahmed MK Forces of various nickel

titanium closed coil springs Angle Orthod 201080182-7

28 Wichelhaus A Brauchli L Ball J Mertmann M Mechanical

behavior and clinical application of nickel-titanium closed-coil

springs under different stress levels and mechanical loading cycles


29 New American Dental Association speci1047297cation no 32 for ortho-

dontic wires not containing precious metals Council on Dental

Materials and Devices J Am Dent Assoc 1977951169-71

30 Martins RP Buschang PH Gandini LG Jr Group A T-loop for dif-

ferential moment mechanics an implant study Am J Orthod Den-

tofacial Orthop 2009135182-9

31 DuerigTW MeltonKN Stockel D Engineeringaspects of shape mem-ory alloys London United Kingdom Butterworth-Heinemann 1990

32 Segner D IbeD Propertiesof superelastic wires andtheir relevance

to orthodontic treatment Eur J Orthod 199517395-402

33 Bartzela TNSenn C Wichelhaus A Load-de1047298ection characteristics

of superelastic nickel-titanium wires Angle Orthod 200777

991-8

34 Melsen B Topp LF Melsen HM Terp S Force system developed

from closed coil springs Eur J Orthod 199416531-9

35 EliadesT Bourauel C Intraoral aging of orthodontic materials the

picture we miss and its clinical relevance Am J Orthod Dentofacial

Orthop 2005127403-12

36 Otsuka K Ren X Martensitic transformations in nonferous shape

memory alloys Mater Sci Eng A 1999273-27589-105

82 Magno et al




signi1047297cant differences in mechanical properties2122

Regarding nickel-titanium CCSs the authors of severalin-vitro studies21223-26 evaluated the forces produced

by them in a simulated oral environment but similarly

the results are controversial with increases

25

decreases21223 and no differences2426 of the forcesover time suggesting that an in-vivo clinical study is

necessary to bring new light to this controversyIt is clinically important to have as much information

as possible on the mechanical properties of nickel-titanium CCSs over time speci1047297cally on the elasticmodulus the average force level used and the perma-nent deformation of these devices This would allowthe clinician to know whether a nickel-titanium CCS

should be replaced or even whether it could be recycled but there is no in-vivo research evaluating the effects of time and use on CCSs Therefore the aims of this study

were to determine the changes that occur in the load-

de1047298ection rate of the superelastic pseudoplateau(LDP) the average force of the superelastic pseudopla-teau (FP) and the permanent deformation of nickel-titanium CCSs after clinical use

MATERIAL AND METHODS

The sample for this prospective study was composedinitially of 50 nickel-titanium CCSs (Sentalloy 100 g

Dentsply GAC York Pa) which were to be used in a ran-domized clinical trial for canine retraction

Before clinical use a mechanical testing machine(DL 2000 EMIC S~ao Jose dos Pinhais Brazil) was

used to test the springs to determine their LDP rates FP and permanent deformation The springs and thehooks that attached them to the machine were sub-mersed in 37C 6 1C of distilled water which was

temperature controlled with a 30-W heater and a ther-mostat27-29

The mechanical test activated the springs to 32 mm(act1) returning them to their initial position (zero) andthen activating them to 64 mm (act2) 96 mm (act3)128 mm (act4) and 1047297nally 160 mm (act5) always re-

turning to the initial position between activationsTo ensure correct activations any possible initial

looseness of the springs was avoided by adjustingthem in increments of 01 mm manually with the digitalindicator of the testing machine before the test startedThe software Tesc (version 304 EMIC) recorded all force

values during the test expressed in raw data format at a

rate of 20 mm per minute No spring showed permanentdeformation after the tests They were properly identi-1047297ed so that the values of the 1047297rst (T1) and second (T2)tests made after clinical use would correspond to thesame springs

To collect the variables stress raw data of each spring were exported to Excel (Microsoft Redmond Wash) Alinear regression was 1047297tted in the most horizontal areaof the stress-strain graph on deactivation to allow thedetermination of the superelastic pseudoplateau Two

points were chosen to determine the beginning andthe end of the pseudoplateau which was the longest

segment of the stress-strain graph explained by theregression line with a coef 1047297cient of determination notless than 0999 The modulus of elasticity of the supere-lastic pseudoplateau (LDP) was determined by the slope

of the regression line ( Fig 1) FP was determined by themidpoint of the superelastic pseudoplateau and perma-

nent deformation was determined graphically at eachstress-strain curve by obtaining the de1047298ection value(variable x) when the amount of force (variable y)reached zero ( Fig 2)

The 50 CCSs tested were then used for canine retrac-tion in 25 patients They were activated by 17 mm (twicethe total length of 85 mm) and were reactivated to thesame length every month After 6 months of treatment22 springs were selected for a second test which wascarried out with the same parameters as the 1047297rst Only 22 springs were tested because the remaining springs

were still in use in the clinical trial after 6 months The22 springs used for the test at T2 showed no visible signsof permanent deformation after clinical use

Because the data collected before and after treatment were normally distributed the SPSS statistical software

Fig 1 Stress-strain graph showing the deactivation of a

nickel-titanium spring The regression line (black ) wasused to identify the more horizontal area of the graph

and to determine LDP (using its slope) The green arrows

show the initial and 1047297nal points chosen to determine the

clinical superelastic pseudoplateau (red ) the midpoint

of that segment (yellow arrow ) is the force variable

measured (FP) in this study

Magno et al 77





RESULTS





















T1 042 (004) 106 N (007) 022 mm (013)

T2 053 (004) 016 N (011) 115 mm (132)

P 0001 0001 0001







Act1 (32 mm) 011A (002) 061 NA (049) 028 mmA (024)

Act2 (64 mm) 005 B (002) 062 NA (047) 049 mmAB (044)

Act3 (96 mm) 003C (001) 061 NA (046) 061 mmAB (065)

Act4 (128 mm) 002C (001) 065 NA (044) 084 mm BC (100)

Act5 (160 mm) 002C (001) 054 N B (044) 126 mmC (182)

P 0001 0001 0001


78 Magno et al
























Act1 (32 mm) 011 (0016)Aa 012 (0031)Aa 0361

Act2 (64 mm) 004 (0008) Ba 005 (0019) Bb 0016

Act3 (96 mm) 003 (0005)Ca 003 (0015)Cb 0009

Act4 (128 mm) 002 (0004)Ca 003 (0014)Cb 0001

Act5 (160 mm) 001 (0003)Ca 003 (0013)Cb 0001

P 0001 0001






Magno et al 79





























T1 T2 ()

Act1 (32 mm) 109 N (007)Aa 013 N (008)Ab 8807

Act2 (64 mm) 108 N (005)Aa 016 N (010)ABb 8519

Act3 (96 mm) 106 N (005)Aa 017 N (011)ABb 8396

Act4 (128 mm) 107 N (005)Aa 022 N (013) Bb 7944

Act5 (160 mm) 097 N (004) Ba 011 N (009)Ab 8866






Newtons)

80 Magno et al


















limeters)



Increase T1 T2

()




Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952




Magno et al 81








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al





RESULTS





















T1 042 (004) 106 N (007) 022 mm (013)

T2 053 (004) 016 N (011) 115 mm (132)

P 0001 0001 0001







Act1 (32 mm) 011A (002) 061 NA (049) 028 mmA (024)

Act2 (64 mm) 005 B (002) 062 NA (047) 049 mmAB (044)

Act3 (96 mm) 003C (001) 061 NA (046) 061 mmAB (065)

Act4 (128 mm) 002C (001) 065 NA (044) 084 mm BC (100)

Act5 (160 mm) 002C (001) 054 N B (044) 126 mmC (182)

P 0001 0001 0001


78 Magno et al
























Act1 (32 mm) 011 (0016)Aa 012 (0031)Aa 0361

Act2 (64 mm) 004 (0008) Ba 005 (0019) Bb 0016

Act3 (96 mm) 003 (0005)Ca 003 (0015)Cb 0009

Act4 (128 mm) 002 (0004)Ca 003 (0014)Cb 0001

Act5 (160 mm) 001 (0003)Ca 003 (0013)Cb 0001

P 0001 0001






Magno et al 79





























T1 T2 ()

Act1 (32 mm) 109 N (007)Aa 013 N (008)Ab 8807

Act2 (64 mm) 108 N (005)Aa 016 N (010)ABb 8519

Act3 (96 mm) 106 N (005)Aa 017 N (011)ABb 8396

Act4 (128 mm) 107 N (005)Aa 022 N (013) Bb 7944

Act5 (160 mm) 097 N (004) Ba 011 N (009)Ab 8866






Newtons)

80 Magno et al


















limeters)



Increase T1 T2

()




Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952




Magno et al 81








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al
























Act1 (32 mm) 011 (0016)Aa 012 (0031)Aa 0361

Act2 (64 mm) 004 (0008) Ba 005 (0019) Bb 0016

Act3 (96 mm) 003 (0005)Ca 003 (0015)Cb 0009

Act4 (128 mm) 002 (0004)Ca 003 (0014)Cb 0001

Act5 (160 mm) 001 (0003)Ca 003 (0013)Cb 0001

P 0001 0001






Magno et al 79





























T1 T2 ()

Act1 (32 mm) 109 N (007)Aa 013 N (008)Ab 8807

Act2 (64 mm) 108 N (005)Aa 016 N (010)ABb 8519

Act3 (96 mm) 106 N (005)Aa 017 N (011)ABb 8396

Act4 (128 mm) 107 N (005)Aa 022 N (013) Bb 7944

Act5 (160 mm) 097 N (004) Ba 011 N (009)Ab 8866






Newtons)

80 Magno et al


















limeters)



Increase T1 T2

()




Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952




Magno et al 81








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al





























T1 T2 ()

Act1 (32 mm) 109 N (007)Aa 013 N (008)Ab 8807

Act2 (64 mm) 108 N (005)Aa 016 N (010)ABb 8519

Act3 (96 mm) 106 N (005)Aa 017 N (011)ABb 8396

Act4 (128 mm) 107 N (005)Aa 022 N (013) Bb 7944

Act5 (160 mm) 097 N (004) Ba 011 N (009)Ab 8866






Newtons)

80 Magno et al


















limeters)



Increase T1 T2

()




Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952




Magno et al 81








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al


















limeters)



Increase T1 T2

()




Act4 (128 mm) 023 mm (014)Aa 144 mm (112) Bb 5261

Act5 (160 mm) 021 mm (015)Aa 230 mm (212)Cb 9952




Magno et al 81








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al








CONCLUSIONS






REFERENCES



























19889489-96















317-22


2008241095-101



22317-26




20126113-9

















thod 199820169-76






















991-8





Orthop 2005127403-12



82 Magno et al


2015_ajodo_magno et al_effect of the clinical use of niti coil

Documents