Étude systématique de la dégradation de la force libérée par la chaînette élastomérique

A review of the literatureRevue de litt�erature

� 2012 CEOPublished by / Edite par Elsevier Masson SAS

All rights reserved / Tous droits reserves

A systematic review of force decay inorthodontic elastomeric power chains

�Etude syst�ematique de la d�egradation de la forcelib�er�ee par la chaınette �elastom�erique

Abdelali HALIMIa,*, Hicham BENYAHIAa, Anas DOUKKALIb,Mohamed-Faouzi AZEROUALc, Fatima ZAOUIa

aUniversity Mohammed V-Souissi (UM5S), Oral Biomechanics and Biotechnology ResearchUnit, Dentofacial Orthopedics Department, College of Dental Medicine, centre hospitalier Ibn-Sina, BP 6212, Rabat-Instituts, Madinat Al Irfane, Rabat, MoroccobUniversity Mohammed V-Souissi (UM5S), Analytical Chemistry Laboratory, College ofMedicine and Pharmacy, centre hospitalier Ibn-Sina, BP 6212, Rabat-Instituts, Madinat AlIrfane, Rabat, MoroccocUniversity Mohammed V-Souissi (UM5S), College of Dental Medicine, DentofacialOrthopedics Department, Clinical and Epidemiological Biostatistics Research Laboratory(LBRCE), centre hospitalier Ibn-Sina, BP 6212, Rabat-Instituts, Madinat Al Irfane, Rabat,Morocco

/ D

SummaryIntroduction: Elastomeric chains are one of several devices usedto provide force for orthodontic tooth movement, but the forcethey exert diminishes over time and can thus be difficult tocontrol. The objective of this investigation was to provide asystematic review of publications pertinent to force decay inorthodontic elastomeric chains.Materials and methods: A systematic review was performed viaelectronic querying of multiple databases for the period 1970–2011. Queries were limited to a set of specific keywords in twolanguages (English and French). Five main reviews were con-sulted manually to identify relevant publications. Two investi-gators sorted out those studies that complied with selectioncriteria.

Available online: 18 August 2012

Results and discussion: A total of 53 studies were found to berelevant to force decay in elastomeric chains, including 22 onforce decay over time, seven on the force consequences of

International Orthodontics 2012 ; 10 : 223-240doi:10.1016/j.ortho.2012.06.013

R�esum�e

Introduction : La chaınette �elastom�erique est l’un des moyensassurant la force du d�eplacement orthodontique. Cependant,cette force n’est pas stable dans le temps, ce qui engendre unprobl�eme de controle de la force exerc�ee sur la dent. L’objectifde ce travail est de pr�esenter une revue syst�ematique des�etudes sur la d�egradation de la force lib�er�ee par la chaınette.Mat�eriel et m�ethode : Une �etude syst�ematique a �et�e r�ealis�eesur la base d’une recherche �electronique (entre 1970 et 2011)de plusieurs bases de donn�ees. La recherche a �et�e limit�ee parl’utilisation de plusieurs mots cl�es sp�ecifiques en deuxlangues : l’anglais et le francais. Une consultation manuelledes cinq principales revues sp�ecifiques a permis derechercher les �etudes pertinentes sur ce sujet. Deux investi-gateurs ont retenu celles qui r�epondaient aux crit�eres des�election.R�esultats et discussion : Nous avons trouv�e 53 �etudes analy-sant la d�egradation de la force lib�er�ee par la chaınette�elastom�erique. Parmi ces �etudes : 22 s’int�eressent a lad�egradation de la force dans le temps, sept analysent l’effet

isponible en ligne : 18 aout 2012

*Correspondence and reprints / Correspondance et tir�es a part :

Abdelali HALIMI, Lot. Wifak 1, immeuble 1422, appartement 20, Tamara, Morocco.e-mail address / Adresse e-mail : [email protected]

223

mailto: [email protected]

http://dx.doi.org/10.1016/j.ortho.2012.06.013

Abdelali HALIMI et al.

pre-stretching, 12 on the impact of the environment on the forcedelivered, and 11 on clinical efficacy.

Conclusion: The force delivered by elastomeric chains decaysrapidly over time, affecting their mechanical properties andclinical efficacy when studied in either human saliva or labo-ratory test media.� 2012 CEO. Published by Elsevier Masson SAS. All rightsreserved

Key-words

·Elastomeric chains.
·Biodegradation. ·Biomechanics. ·Tooth movement.
·Orthodontics.
·Systematic review.Introduction
Elastomeric power chains were first introduced in orthodon-tics in the early 20th century. In the 1960s, industrialimprovements allowed their more frequent adoption in ortho-dontic biomechanics [1,2].Elastomeric chains come in three different forms: short (open),long (wide), and closed (continuous). They may be transparent,gray, or other-colored (fig. 1). Their exact composition is keptsecret by orthodontic manufacturers [3–5], but they are mademainly from clear resin or polyurethanes. Polyurethane rubberis a generic material manufactured from polyester or polyetherglycol, or from polyhydrocarbon diols with a diisocyanate.Biodegradable polyurethanes (PU) have been synthesized

[(Fig._1)TD$FIG]

Fig. 1: Different types of elastomdimensions.Fig. 1 : Diff�erents types de chaınet

dimensions vari�ees.

224

de pr�e-�etirement sur la force lib�er�ee par chaınette, 12s’int�eressent a l’effet de l’environnement sur la force lib�er�eeet 11 examinent l’efficacit�e clinique des chaınettes.Conclusion : La force lib�er�ee par la chaınette subit uned�egradation rapide dans le temps ; cela affecte ses propri�et�esm�ecaniques et son efficacit�e clinique, aussi bien dans la salivehumaine que dans les milieux biologiques �etudi�es.� 2012 CEO. Edite par Elsevier Masson SAS. Tous droitsreserves

Mots-cl�es

·Chaınette �elastom�erique.

·Biod�egradation.
·Biom�ecanique.
·D�eplacement dentaire.

·Orthodontie.

·Revue syst�ematique.

Introduction

La chaınette �elastom�erique est apparue en orthodontie aud�ebut du XX

e si�ecle. Dans les ann�ees soixante, son am�eliora-tion industrielle a permis sa fr�equente int�egration dans labiom�ecanique orthodontique [1,2].Les chaınettes �elastom�eriques existent sous diff�erentes for-mes : chaınettes a modules serr�es, chaınettes a modulesrapproch�es et chaınettes a modules espac�es. Elles peuventetre transparentes, grises, ou de diff�erentes couleurs (fig. 1).La composition exacte des chaınettes est gard�ee secr�ete parles diff�erents fabricants de mat�eriel orthodontique [3–5]. Lachaınette peut etre fabriqu�ee a partir des r�esines claires oudes polyur�ethanes qui constituent le composant principal. Le

eric chain: various colors and

tes �elastom�eriques : couleurs et

International Orthodontics 2012 ; 10 : 223-240

[(Fig._2)TD$FIG]

Fig. 2: Polyurethane synthesis mechanisms (methylene diphenyldiisocyanate [MDI], polycaprolactone [PCL] 530, methylimino-diethanol [MIDE], N, N-bis[Hydroxyethyl]-2-aminoethanesulfonicacid [BES]). Molecular chain extension can be modified to obtaindifferent functionality from the same material.Fig. 2 : Sch�ema synth�etique de la pr�eparation des polyur�etanes

(m�ethyl�ene diph�enylique di-isocyanate [MDI], polycaprolactone

[PCL] 530, MIDE ou N, N-bis [2-acide hydorxyethyl]-2-aminoethane-

sulfonic [BES]). L’extension de la chaıne peut etre modifi�ee pour obte-

nir diff�erentes fonctionnalit�es du meme mat�eriel.

A systematic review of force decay in orthodontic elastomeric power chains�Etude syst�ematique de la d�egradation de la force lib�er�ee par la chaınette �elastom�erique

from methylene diphenyl diisocyanate (MDI), polycaprolac-tone diol (PCL-diol), and N, N-bis(Hydroxyethyl)-2-ami-noethanesulfonic acid (BES) [6](fig. 2).

Elastomeric chains provide force for tooth leveling and align-ing, rotation correction, canine and incisor retraction afterextraction, space closure, midline correction, orthodonticretention, mesial displacement in the posterior quadrants,and traction of impacted teeth [1,4,6,7] (fig. 3). Change intheir force over time, however, leads to therapeutic controlproblems. Several studies (Table I) have reported that chainsmay lose 50 to 75% of their initial force during the first day ofwear, followed by continuous exponential decay (Table II)(fig. 4). This is due to exposure to the intraoral environment,mastication, oral hygiene, salivary enzyme activity, and


polyur�ethane caoutchoutique est un g�en�erique fabriqu�e a par-tir de polyester ou poly�ether glycol ou polyhydrocarbon diolavec a di-isocyante. Les polyur�ethanes biod�egradables (PU)ont �et�e synth�etis�es a partir du m�ethyl�ene diph�enyliquedi-isocyanate (MDI), polycaprolactone diol (PCL-diol) et N,N-bis (2-acide hydorxyethyl)-2-aminoethane-sulfonic (BES)[6] (fig. 2).La chaınette �elastom�erique assure la force d’alignement/nivel-lement dentaire, la correction des rotations, la r�etractioncanine et incisive apr�es extraction, la fermeture des espaces,la correction des m�edianes, le maintien des dents entre elles,la m�esialisation des secteurs post�erieurs, la traction des dentsincluses [1,4,6,7] (fig. 3). Mais l’instabilit�e de cette force dansle temps engendre un probl�eme de controle th�erapeutique.Plusieurs �etudes (Tableau I) rapportent que la chaınette pour-rait perdre 50 % a 75 % de sa force initiale pendant le premierjour d’application, puis continue a se d�egrader d’une faconexponentielle (Tableau II) (fig. 4). Cette d�egradation s’explique

225

[(Fig._3)TD$FIG]

Fig. 3: Some clinical applications for elastomeric chains in orthodontics: a: leveling-aligning-derotating of 2; band c: canine retraction; d: space closure and central incisor correction.Fig. 3 :Quelques applications cliniques de la chaınette �elastom�erique en orthodontie : a : alignement-nivellement-

d�erotation de la 2 ; b et c : r�etraction canine ; d : fermeture d’espaces et correction des m�edianes incisives.

[(Fig._4)TD$FIG]

Fig. 4: a and b: force decay curves for the gray chain and the Fluor-I chain. Kovatch et al. [12].

Fig. 4 : a et b : courbes de d�egradation de la force lib�er�ee par la chaınette grise et la chaınette Fluor-I. D’apr�es

Kovatch et al. [12].

226 International Orthodontics 2012 ; 10 : 223-240


Table IList of studies relevant to force decay over time.

Tableau IListe des �etudes qui s’int�eressent a la d�egradation de la forcelib�er�ee dans le temps.

8, 9 Degradationof forcereleased inthe time/D�egradationde la forcelib�er�ee dansle temps

Andreasen 1970 AO Unitek C-1 alastik modules and latex elastics/Unitek C-1 modulesalastik et �elastiques en latex

10 Hershey 1975 AJO Unitek C-1 alastik modules, Ormco Power chain, TP Elast-O-Chain

11 Wong 1976 AO Unitek C-1 alastik modules, Ormco Power chain

12 Kovatch 1976 JDR Unitek C-1 alastik modules

1 Ash 1978 JDR Unitek C-1 alastik modules

13 Brantley 1979 AO Unitek C-1 alastik modules, Ormco Power chain II

14 De Genova 1985 AJO Ormco Power chain II, Rocky mountain Energy chain, TP Elast-O-Chain

15 Rock 1985 BJO 13 different types of chains/13 differents types de chaınette

16 Killiany 1985 JCO Rocky mountain Energy chain/

17 Kuster 1986 EJO Unitek C-1 alastik modules, Ormco Power chain II

18 Baty 1992 IP Unitek C-1 alastik modules, Ormco Power chain II and Masel coloredchains/Unitek C-1 modules alastik, Ormco Power Chain II et MaselColored Chains

19 Eliades 2003 HOR Open and closed types of elastomeric chain (ORMCO)/Chaınette�elastom�erique de type ouvert et ferm�e (ORMCO)

20 Chimenti 2001 PO Six differents types of elastomeric chains, total of 312 elastomericchains/Six diff�erents types de chaınettes �elastom�eriques, total de 312chaınettes �elastom�eriques

27 Eliades 2005 JOR Three polyurethane elastomeric modules (Generation II, Dentaurum,Alastic)/Trois modules �elastom�eriques en polyur�ethane (Generation II,Dentaurum, Alastic)

21 Eliades 2004 EJO Two types (open and closed chains, with and without link) of three brandsof elastomeric module/Deux types de modules �elastom�eriques(chaınette ouverte et ferm�ee, avec et sans lien) de 3 marques

22 Storie 1994 AO Fluor-I-Chain, standard gray elastomeric chain/Fluor-I-Chain,chaınettes �elastom�eriques standard grise

24 Stevenson 1993 AJO-DO Transparent and grey elastomeric chains/Chaınettes �elastom�eriquestransparentes et grises

25 Renick 1994 AO Three polyurethane-based elastomeric chains (Nihon, Pellethane,Texin)/Trois chaınettes �elastom�eriques a base de polyur�ethane (Nihon,Pellethane, Texin)

26 Sang 2004 AJO-DO Three different colored chains (gray, red and purple) from 3manufacturers (RMO, Ormco and G&H)/Trois diff�erentes chaınettescolor�ees (gris, rouge et pourpre) provenant de 3 fournisseurs (RMO,Ormco et G&H)

28 Balhoff 2008 SKQYX The chains of different type of filament and number of loops, specifiedinitial force/Chaınettes avec diff�erents types de liens et de nombred’anneaux, d�elivrant une force initiale sp�ecifique

23 Chau Lu 2011 JO Closed (non-spaced), grey elastomeric chains from four companies/Chaınettes �elastom�eriques grises ferm�ees (sans espace) de 4fournisseurs

International Orthodontics 2012 ; 10 : 223-240 227


Table IIValues for force exerted by the gray chain and the Fluor-Ichain.

Tableau IIValeurs de la force lib�er�ee par la chaınette grise et la chaınetteFluor-I.

Force delivery in grams at a distraction of 100% and percentage of initial load/Force d�elivr�ee en grammes pour un �etirement de100% et pourcentage de la charge initiale

Time/Temps 0 4 hours/4 heures

24 hours/24 heures

7 days/7 jours

14 days/14 jours

21 days/21 jours

Gray chain

Fluor-I Chain

Force/Force 316.3 W 25.6 188.2 W 4.4 122.4 W 2.8 43.2 W 2.0 26.5 W 1.4 20.4 W 1.2a

Percentage/Pourcentage

100 59.5 38.7 13.7 8.4 1.2

Gray chain

Force/Force 279.6 W 18.2 164.6 W 5.2 127.1 W 4.3 106.9W 3.9 101.2 W 4.6 97.5 W 4.0

Percentage/Pourcentage

100 58.9 45.5 38.3 36.2 34.9

Difference (P)/Diff�erenceb(p) <0.05 <0.05 ns <0.05 <0.05 <0.05aMean valueW standard deviation.b Significance of difference between mean force levels.

Kovatch et al. [12].aMean valueW standard d�eviation.b Signification de la diff�erence entre les niveaux de force moyenne.Kovatch et al. [12].


variations in oral temperature potentially accelerating in vivochain aging (fig. 5).

The objective of this investigation was to develop a systematicreview of force decay in orthodontic elastomeric chains.

Materials and methods

Research methodology

A systematic study was performed via electronic querying ofseveral databases (Medline, PubMed, and Cochrane CentralRegister of Controlled Trials) for the period 1970–2011.

Queries were limited to a set of specific keywords (elastomericchain, polyurethane chain, orthodontic space closure, ortho-dontics, dental, clinical trials, systematic review, meta-analysis) in both English and French.

228

par l’exposition intra orale, l’effet de la mastication, l’hygi�eneorale, les enzymes salivaires et la variation de la temp�eraturebuccale qui pourrait acc�el�erer le vieillissement in vivo de lachaınette (fig. 5).L’auteur pr�esente une revue syst�ematique autour de la ques-tion de la d�egradation de la force lib�er�ee par la chaınette�elastom�erique.

Mat�eriel et m�ethode

Strat�egie de recherche

Une �etude syst�ematique a �et�e r�ealis�ee sur la base d’unerecherche �electronique (entre 1970 et 2011) de plusieursbases de donn�ees (Medline, PubMed et Cochrane CentralRegister of Controlled Trials).La recherche a �et�e limit�ee par l’utilisation de plusieurs motscl�es sp�ecifiques (elastomeric chain, polyurhetane chain,orthodontic space closure, orthodontics, dental, clinical trials,systematic review, meta-analysis), et cela en deux langues :l’anglais et le francais.


[(Fig._5)TD$FIG]

Fig. 5: Phase-contrast microscopy showing the appearance of agingin an elastomeric chain after 3-week intraoral use.Fig. 5 : Image par contraste des phases montrant l’aspect du vieillis-

sement de la chaınette �elastom�erique apr�es trois semaines d’utilisa-

tion en bouche.


Five main reviews (American Journal of Orthodontics andDentofacial Orthopedics, European Journal of Orthodontics,Angle Orthodontist, British Journal of Orthodontics,Australian Journal of Orthodontics) were consulted manuallyto identify pertinent investigations (prospective clinical, invivo and in vitro trials). Two investigators selected a subsetof such studies based on the inclusion criteria.

Inclusion criteria

Inclusion was limited to in vivo and in vitro prospective clin-ical studies addressing force decay in elastomeric chains andanalyzing the various factors capable of influencing theirmechanical properties and clinical efficacy.

Only publications in English and French were considered.

Results and discussion

A total of 53 prospective studies were found to analyze forcedecay in elastomeric chains, including:

— 22 studies of force decay over time (Table I);

— seven studies addressing the effects of pre-stretching onchain force (Table III);— 12 studies considering environmental effects on force(Table IV);— 11 studies investigating the clinical efficacy of elastomericchains (Tables V and VI).


Une consultation manuelle des cinq principales revues sp�eci-fiques (American Journal of Orthodontics and DentofacialOrthopedics, European Journal of Orthodontics, AngleOrthodontist, British Journal of Orthodontics, AustralianJournal of Orthodontics) a �et�e faite a la recherche des �etudespertinentes (prospective clinical, in vivo and in vitro trials)s’int�eressant au sujet. Deux investigateurs ont retenu cellesqui r�epondaient aux crit�eres de s�election.

Crit�ere d’inclusion

L’inclusion a �et�e limit�ee a des �etudes prospectives cliniques invivo et in vitro qui s’int�eressent a la d�egradation de la forcelib�er�ee par la chaınette �elastom�erique, ainsi qu’a l’analyse desdiff�erents facteurs qui peuvent influencer les propri�et�esm�ecaniques et l’efficacit�e clinique de cet outil.La recherche a �et�e limit�ee aux langues anglaise et francaise.

R�esultats et discussion

Nous avons d�enombr�e 53 �etudes prospectives analysant lad�egradation de la force lib�er�ee par la chaınette �elastom�erique,parmi ces �etudes :— 22 �etudes s’int�eressent a la d�egradation de la force dans letemps (Tableau I) ;— sept �etudes analysent l’effet de pr�e-�etirement sur la forcelib�er�ee par chaınette (Tableau III) ;— 12 �etudes examinent l’effet de l’environnement sur la forcelib�er�ee (Tableau IV) ;— 11 �etudes portent sur l’efficacit�e clinique des chaınettes�elastom�eriques (Tableaux V et VI).

229

Table IIIList of studies reporting on the impact of pre-stretching.

Tableau IIIListe des �etudes qui rapportent l’effet du pr�e-�etirement sur lachaınette �elastom�erique.

Reference No./R�ef�erence no

Topic/Sujet First author/Premier auteur

Year/Ann�ee

Journal/Journal

Tested material/Mat�eriel test�e

11 Effect ofpre-stretch/Effet dupr�e-�etirement

Wong 1976 AO Unitek C-1 alastik modules,Ormco Power chain

30 Brooks 1976 JDR Unitek C-1 alastik modules

13 Brantley 1979 AO Unitek C-1 alastik modules,Ormco Power chain II

29 Young 1979 AO Unitek C-1 alastik modules,Unitek C-2 alastik modules

7 Kim 2005 AJO-DO Two module lengths, Five-unit and6-unit of clear, closed loop chain(Generation II, Ormco, Glendora, Calif)/Deux longueurs de modules,5 et 6 unit�es de chaınette claire,anneaux serr�es (Generation II,Ormco, Glendora, Calif)

24 Stevenson 1994 AO Three polyurethane-based elastomericchains (Nihon, Pellethane, Texin)/Trois chaınettes �elastom�eriquesa base de polyur�ethane(Nihon, Pellethane, Texin)

8 Andreasen 1970 AO Alastik chains with elastics involvedwith intra-arch molar-to-molar forces/Chaınettes alastik associ�ees a uneforce �elastique intra-arcadereliant une molaire a l’autre


Decay of force over time

Ideally, force decay between activation time-points should beminimal, with force remaining constant during the timeelapsed. As this literature review revealed, however, 22 dif-ferent studies (Table I) by a variety of authors [1,8–28] con-curred that elastomeric chains were incapable of deliveringcontinuous force over time. Force decay in elastomeric chainswas greatest on day one, then continued regularly at a muchslower rate, yielding an average degradation of 50 to 85% after4 weeks (depending on study and chain type) versus initialforce.

All authors concurred that force dropped by 40 to 50% overthe first few hours, then continued to decay at a lesser rate for 2to 3 weeks. The greatest loss of force occurred during hour 1,reaching total loss by day 4 [17]. In order to compensate for

230

D�egradation de la force dans le temps

Id�ealement la d�eperdition de force entre deux activations estminimale et la force g�en�er�ee est d’intensit�e constante pendantcette p�eriode.Malheureusement, d’apr�es la pr�esente revue delitt�erature, rassemblant 22 �etudes autour de cette question(Tableau I), tous les auteurs [1,8–28] s’accordent a dire quela chaınette �elastom�erique est incapable de d�elivrer une forcecontinue dans le temps. La d�eperdition de force deschaınettes est plus importante le premier jour, puis elle estensuite r�eguli�ere et beaucoup plus faible. Cette d�eperdition estenmoyenne de 50 a 85 % de la force initiale au bout de quatresemaines en fonction des diff�erentes chaınettes et desdiff�erentes �etudes.Selon un consensus g�en�eral, il se produit un d�eclin de la forcede 40 a 50 % durant les premi�eres heures, puis la d�eperditionde force continue a un taux plus faible pendant deux a troissemaines. La plus grande partie de cette d�egradation se


Table IVList of studies addressing the effect of surroundingenvironment on elastomeric force.

Tableau IVListe des �etudes qui s’int�eressent a l’effet de l’environnementsur la force �elastom�erique lib�er�ee.


Topic/Sujet First author/Premier auteur

Year/Ann�ee

Journal/Journal


14 Effects ofsurroundingenvironment/Effet del’environnement

De Genova 1985 AJO Ormco Power chain II, Rocky mountain Energy chain,TP Elast-O-Chain

31 Ferriter 1990 AJO-DO ’A” Company Force A Chain, American Memory Chain,GAC Chainette, Ormco Power chain II, Rocky mountainEnergy chain, TP Elast-O-Chain, Unitek C-1 alastikmodules

32 Jefferies 1991 AO ’A” Company Force A Chain, American Memory Chain,GAC Chainette, Ormco Power chain II, Rocky mountainEnergy chain, TP Elast-O-Chain, Unitek C-1 alastikmodules

33 Von Frauhofer 1992 AO Unitek C-1 alastik modules, Ormco Generation II Powerchain, TP E-Chain

27 Eliades 2005 JOR Three polyurethane elastomeric modules (GenerationII, Dentaurum, Alastic)/Trois modules �elastom�eriquesen polyur�ethane (Generation II, Dentaurum, Alastic)

34 Eliades 1999 EJO Two types of three brands of elastomeric modules/Deuxtypes de 3 marques de modules �elastom�eriques

35 Nattrass 1998 EJO Nickel titanium springs, medium-spaced elastomericchain (Durachain, Ortho-Care, Bradford, UK)/Ressortsen nickel-titane, chaınette �elastom�eriquemoyennement espac�ee (Durachain, Ortho-Care,Bradford, UK)

36 Stevenson 1995 JMS Three polyurethane-based elastomeric modules/Troismodules �elastom�eriques a base de polyur�ethane

37 Casaccia 2007 AO Elastomeric chains from three manufacturers(Ortho-Organizers Inc, 3 M Unitek, and DentalMorelli)/Chaınettes �elastom�eriques de 3 fournisseurs(Ortho-Organizers Inc, 3M Unitek, et Dental Morelli)

38 Teixeira 2008 JCDP 160 gray colored elastomeric chain modules, immersioninto Light Coke, phosphoric acid, citric acid andartificial saliva/160 chaınettes �elastom�eriques decouleur grise, immerg�ees dans duCoca Light, de l’acidephosphoric, de l’acide citrique et de la salive artificielle

39 Ramazanzadeh 2009 JCPD American Orthodontics chains, Dentaurum chains;artificial saliva, 0.05% NaF and artificial saliva-NaFmixture/American Orthodontics Chains, DentaurumChains, immerg�ees dans de la salive artificielle, du NaFa 0,05% et un m�elange de salive artificielle et de NaF

40 Pithon 2010 OW Three orthodontic elastic chain bands, sterilization byseven different methods/Trois longueurs de chaınette�elastique st�erilis�ees par 7 m�ethodes diff�erentes



Table VList of studies reporting on the clinical efficacy of elastomericchains.

Tableau VListe des �etudes qui rapportent l’efficacit�e clinique de lachaınette �elastom�erique.


Topic/Sujet

First author/Premier auteur

Year/Ann�ee

Journal/Journal


42 Clinicalefficacy

Sonis 1986 AJO Unitek C-1 alastik modules, Rocky mountain Energychain, Unitek nylon-covered latex thread

43 Huget 1990 JDR Ormco Power chain II

44 Sonis 1994 JCO Niti coil springs vs. Elastics/Ressorts en Nitinol parrapport aux �elastiques

45 Samuels 1993 AJO-DO Nickel-titanium spring and an elastic module/Ressort en nickel-titanium et module �elastique

46 Samuels 1998 AJO-DO Nickel-titanium closed coil spring and an elasticmodule/Ressort a spires ferm�ees en nickel-titaniumet module �elastique

47 Dixon 2002 JO Three methods of orthodontics space closure:Ni-Tispring, active ligature, power chain/Trois m�ethodesde fermeture d’espaces orthodontiques: ressort Ni-Ti, ligature active, chaınette �elastique

48 Nightingale 2003 JO Niti spring, Medium-spaced elastomeric chain(Power chain)/Ressort Ni-ti, chaınette �elastique aespaces moyens (Power chain)

49 Bokas 2006 AOJ Niti spring, Power chain/Ressort Ni-ti, chaınette�elastique

50 Bousquet 2006 AJO-DO Two types of elastomeric chains (injection moldedand die-cut stamped)/Deux types de chaınettes�elastom�eriques (moul�ees par injection etd�ecoup�ees par estampage)

51 Santos 2007 BOR Forty elastomeric chains and forty NiTi closed coilsprings from four manufacturers/Quarantechaınettes �elastom�eriques et 40 ressorts NiTi aspires ferm�ees de 4 fournisseurs

52 Barlow 2008 OCR Elastomeric chain, nickel-titanium coil springs


this rapid decay, Andreasen and Bishara [8] recommendedincreased stretching of the chain (so as to obtain considerablymore initial force), but this caused enormous discomfort forpatients and could lead to complications such as root resorp-tion [7].

Deformation mechanisms also played a very important part inforce decay (fig. 6). Stretching a chain slowly or at hightemperatures caused its load–deflection curve to deviate froma straight line towards greater compliance, whereas rapid orlow-temperature stretching led the material to behave more

232

produit pendant la premi�ere heure avec une intensit�eminimumau quatri�eme jour [17]. Pour compenser cette d�egradationrapide, Andreasen et Bishara [8] recommande un �etirementaccentu�e de la chaınette (pour avoir une force initiale beau-coup plus importante), mais cela cause �enorm�ement d’incon-fort pour le patient et peut entraıner d’autres complicationstelle que la r�esorption radiculaire [7].Lemode de d�eformation joue �egalement un role tr�es importantdans cette d�egradation (fig. 6), et l’�etirement de la chaınettea un rythme lent ou a haute temp�erature d�evie la courbecharge–flexion de cet outil vers la ligne droite, le mat�eriauest plus compliant. Au contraire, son �etirement a un rythme


Table VIBibliographical abbreviations and their references.

Tableau VILes abr�eviations des r�ef�erences bibliographiques et leurscorrespondances.

(AO) Angle Orthodontist

(AJO) American Journal of Orthodontists

(AJO-DO) American Journal of Orthodontics and Dentofacial Orthopaedics

(BJO) British Journal of Orthodontics

(BOR) Braz Oral Res

(EJO) European Journal of Orthodontics

(HOR) Hellenic Orthodontic Review

(IO) International Orthodontics

(IP) In Press

(JCDP) J Contemp Dent Pact

(JCO) Journal of Clinical Orthodontics

(JCPD) J Clin Pediatr Dent

(JDR) Journal Dental Research

(JMS) Journal of Materials Science: Materials In Medicine

(JO) J Orthodox

(JOR) Journal of Oral Rehabilitation

(OCR) Orthodontics & Craniofacial Research

(OW) Orthodontic Waves

(PC) Personnel Communication

(PNSCRC) Proc Natl Sci Counc Repub China

(PO) Progress in Orthodontics

(SKQYX) Shanghai Kou Qiang Yi uXe


like a rigid body, because the chain segments lacked time tomobilize and there was no molecular slippage [25]. The morethe chain was stretched, the greater the initial force deliveredand the weaker the residual force [9]. The authors of thisreview recommend gentler stretching of the chain so as toavoid major force decay.

Chain manufacturing methods

Chain manufacturing methods [7,27] had no effect on forcedecay, and clinical results in canine retraction were statisti-cally similar for both injection-molded and die-cut stampedmodules.


rapide ou a basse temp�erature conduit le mat�eriau a plus secomporter comme un corps rigide, car les segments n’ont pasle temps d’etremobilis�es, et il n’y a pas de glissement entre leschaınes [25]. Plus la chaınette est �etir�ee, plus la force initialed�elivr�ee est importante et plus la force r�esiduelle sera faible[9]. Pour rem�edier a une d�egradation importante, l’auteurrecommande un �etirement plus doux de la chaınette.

La m�ethode de fabrication de la chaınette

La m�ethode de fabrication de la chaınette [7,27] n’influencepas sa d�egradation, et le r�esultat de l’utilisation clinique decette m�ecanique (qu’elle soit concue par technique de mou-lage par injection injection-molded ou par technique dematric-age die-cut stamped) pour la r�etraction canine �etait statique-ment similaire.

233

[(Fig._6)TD$FIG]

Fig. 6: Correlation between extension speed and relaxationin a polyurethane elastomeric module. Kovatch et al. [12].

Fig. 6 : D�ependance entre la vitesse d’extension et la relaxa-

tion d’un module �elastom�erique en polyur�ethane. D’apr�esKovatch et al. [12].


Eliades et al. [16,19,27] found that open chains exhibitedgreater residual elongation than closed ones, allegedly dueto major extension of the inter-modular link areas, but thesedifferences varied from brand to brand depending on linklength and module shape. Closed chains delivered more forceand decayed more rapidly than open ones after 100% stretch-ing [1,10,14,27]. The initial force delivered by closed chainsstretched to 100% was 403 to 625 g. Rock et al. [15] judgedthis to be a considerable amount of force, and recommendedstretching the chain by only 50 to 75% of its initial length so asto yield a force of around 300 g.

For Wong [11], the force delivered by the chain also variedfrom brand to brand. The Ormco Power chain was more resil-ient than the Unitek Alastik chain, but the latter exertedgreater force. Renick et al. [25] found that the RockyMountain Orthodontics (RMO) chain delivered more forcethan the Ormco and G&H chains. Balhoff et al. [28] foundthat the Ormco chain exhibited the least decay and the Unitekchain the most. Killiany and Duplessis [16] found that theAmerican Orthodontics (AO) closed chain exerted greaterinitial force (375 g) than the RMO “Energy” closed chain(330 g) after 100% stretching. After 4-week storage in a sim-ulated oral environment, the RMO chain retained 66% of itsinitial force, while the AO chain retained only 33%.

In light of these variations in force, Hershey and Reynolds [10]recommended determining initial chain force via a dynamom-eter prior to clinical implementation.

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Eliades et al. [16,19,27] ont trouv�e que les chaınettes a mod-ules espac�es pr�esentent des �elongations r�esiduelles plusimportantes que les chaınettes a modules serr�es. Cela seraitdu a une �elongation importante au niveau des r�egions inter-modulaires, mais les diff�erences varient selon les marques enraison de la variabilit�e de la longueur entre les modules, et dela forme des modules. La chaınette a modules serr�es d�elivreplus de force et se d�egrade plus rapidement par rapport a lachaınette a modules espac�es suite a l’�etirement a 100 %[1,10,14,27]. La force initiale d�elivr�ee par les chaınettesserr�ees �etir�ees a 100 % est de l’ordre de 403 a 625 g : cetteforce est jug�ee importante par Rock et al. [15] qui ontrecommand�e l’extension de la chaınette de 50 % a 75 % seu-lement par rapport a sa longueur initiale pour produire uneforce souhait�ee autour de 300 g.Pour Wong [11], la force d�elivr�ee par la chaınette varie enfonction de la marque. La chaınette Ormco Power est plusr�esiliente par rapport a la chaınette Unitek Alastik ; cette der-ni�ere d�egage plus de force. Renick et al. [25] ont trouv�e que lachaınette RMO d�elivre une force plus importante en compa-raison avec la chaınette Ormco et la chaınette G&H. Balhoff etal. [28] ont trouv�e que la chaınette Ormco avait le plus faiblepourcentage de d�egradation et que la chaınette Unitek avait leplus grand pourcentage de d�egradation. Killiany et Duplessis[16] ont trouv�e que la chaınette American Orthodontics (AO)a module serr�e lib�ere une force initiale plus importante (375 g)que la chaınette RMO « �Energie » a module serr�e (330 g)suite a l’�etirement a 100 %. Apr�es quatre semaines de stock-age dans un environnement oral simul�e, la chaınette RMOretient 66 % de la force initiale par rapport a l’AO qui retientseulement 33 % de sa force initiale.Pour ces raisons de variation de la force, Hershey et Reynolds[10] recommandent un dosage de la force initiale de lachaınette par un dynamom�etre avant son utilisation clinique.



Chimenti et al. [20] found that the gray chain decayed lessrapidly than the transparent one. This decay was dependent onmultiple factors: time, thickness, and degree of stretching.Sang and Wu [26] reported that residual force was dependenton filament type (medium, mini, small, large), and that thenumber of modular rings was statistically significant. Initialforce, however, had no impact on decay.

Rock et al. [15] showed that force decay was greater in vivothan in air. Chains stretched in air maintained 70 to 75% oftheir initial force, while those stretched in vivo maintainedonly 43 to 52% after 4 weeks.

Ash and Nicolai [1] showed force decay to be greater in vivothan in vitro. For this reason, certain authors have recom-mended against the use of elastomeric chains, in favor ofnickel-titanium (NiTi) springs, which exhibit much less forcedecay.

Effects of pre-stretching on chain force

So as to obtain moderate and relatively stable force over time,certain authors [11,13,29] recommended pre-stretching ortho-dontic elastomeric chains prior to clinical use. Pre-stretchingstresses the molecular bonds in the polymeric material inorder to improve the force exerted by the elastomer.According to this literature review, however, every author[7,8,11,13,24,29,30] involved in all eight studies on the issue(Table III) concurred that pre-stretching elastomeric chainsdid nothing to inhibit force decay over time.

Brantley et al. [13] concluded that pre-stretching had noimpact on elastomer relaxation and thus conferred no clinicaladvantage, while Kim et al. [7] concluded that pre-stretchinghad an effect only during the first hour following activation andthat its clinical payoff remained dubious.

Brooks and Hershey [30] found that pre-stretching combinedwith heating of the chain yielded a non-significant reductionin force decay (50% at 1 hour, 31% at 4 weeks), while heatalone only aggravated the decay.

Effects of environment

Multiple authors have investigated the impact of environmen-tal factors on force decay in orthodontic elastomeric chains.Twelve such studies were found here (Table IV).

Ash [1], von Fraunhofer, and Stevenson concluded that chainswere highly sensitive to thermal shock and temperature varia-tions [14,31–38]. A potential thermal aging phenomenon wasobserved in chains prior to their intraoral implementation,


Chimenti et al. [20] ont trouv�e que la chaınette grise sed�egrade moins vite par rapport a la chaınette transparente.Cette d�egradation d�epend de plusieurs facteurs : temps,�epaisseur et longueur d’�etirement de la chaınette. Sang etWu [26] ont rapport�e que la force restante r�esultait du typede filament (m�edium, mini, petit, large) et que le nombred’anneaux �etait statiquement significatif. En revanche, l’influ-ence de la force initiale n’avait pas d’impact sur la d�egradation.Rock et al. [15] ont montr�e que la d�egradation de la forcelib�er�ee par les chaınettes est plus importante in vivo qu’al’air ambiant. Les chaınettes �etir�ees a l’air ambiant maintien-nent 70 % a 75 % de la force initiale, et les chaınettes �etir�eesin vivo maintiennent seulement 43 % a 52 % apr�es quatresemaines.Ash et Nicolai [1] ont montr�e que ce ph�enom�ene ded�egradation de la force est plus important in vivo que in vitro.C’est pourquoi certains recommandent d’�eviter l’utilisation dechaınettes �elastom�eriques, et d’utiliser des ressorts en nickel-titanium (NiTi) avec lesquels la d�eperdition de force est beau-coup moins importante.

Effet du pr�e-�etirement sur la force lib�er�ee par chaınette

A la recherche d’une force faible et relativement stable dans letemps, certains auteurs [11,13,29] recommandent le pr�e-�etirement des chaınettes avant utilisation clinique. Le pr�e-�etirement consiste a pr�e-stresser les liaisons mol�ecules dupolym�ere en vue d’am�eliorer la force lib�er�ee par cet�elastom�ere. Malheureusement, d’apr�es la pr�esente revue delitt�erature, rassemblant huit �etudes autour de cette question(Tableau III), tous les auteurs [7,8,11,13,24,29,30] s’accor-dent a dire que le pr�e-�etirement de la chaınette �elastom�eriquene r�eduit pas la d�egradation de la force dans le temps.Brantley et al. [13] ont conclu que le pr�e-�etirement de lachaınette n’a pas d’influence sur la relaxation de l’�elastom�ereet par cons�equent n’a aucun int�eret sur le plan clinique. Kim etal. [7] ont conclu que le pr�e-�etirement n’a d’effet que pendant lapremi�ere heure d’activation et que les r�esultats cliniques decette manœuvre �etaient discutables.Brooks et Hershey [30] ont trouv�e la combinaison de l’effet dupr�e-�etirement avec l’�echauffement de la chaınette permet uner�eduction non significative (50 % a la premi�ere heure et 31 %a quatre semaines) de la d�egradation, mais l’�echauffementseul de la chaınette augmente cette d�egradation.

Effet de l’environnement

Plusieurs auteurs se sont int�eress�es a l’�etude de l’influence del’environnement sur la d�egradation de la force lib�er�ee par lachaınette �elastom�erique. Nous avons trouv�e dans cette rubri-que 12 �etudes traitant ce sujet (Tableau IV).Ash [1], von Fraunhofer et Stevenson ont conclu que leschaınettes sont tr�es sensibles aux chocs thermiques et auxvariations de temp�erature [14,31–38]. Un ph�enom�ene de vieil-lissement thermique des chaınettes peut exister avant leur

235


whence the relevance of storage media. Autoclaving chainsled to force decay.

De Genova et al. [14] came nonetheless to the conclusion thatelastomeric chains subjected to a varying thermal environ-ment (15 to 45 �C) retained more of their force than thosesubjected to a constant temperature of 37 �C.

Chains lost less force in basic environments than in acidicones. Nattrass et al. [35] showed greater elastomeric chainforce decay in cola and curcuma than in water. Eliades etal. [34], however, demonstrated no significant difference inthe tensile strength of chains stretched in air versus intra-orally. Teixeira et al. [38] showed that immersion of chainsin phosphoric or citric acid had no impact on their force decayproperties, and Ramazanzadeh et al. [39] concluded the samefor daily mouth rinsing with a NaF solution. Jefferies and VonFraunhofer [32] concluded that an alkaline glutaraldehydesolution was without deleterious effect, and might in factconstitute an appropriate disinfection medium.

Pithon et al. [40] showed that sterilizing elastics chemically(alcohol 70�, glutaraldehyde) or thermally (autoclaving,microwaving) led to a statistically significant increase in elas-tomer cytotoxicity. This increase in cytotoxicity varieddepending on the sterilization method used for comparison(ethylene, ultraviolet, gamma rays).

Clinical efficacy of elastomeric chains

Elastomeric chains are commonly used to achieve orthodontictooth movement, especially in straight-wire techniques, buttheir force does not remain stable over time and can lead totherapeutic control problems. This literature review covering11 studies on the clinical efficacy of orthodontic elastomericchains (Table V) revealed that authors failed to concur on thesubject, and that chains were regularly compared with spring-type continuous-force devices despite ongoing debate overcontinuous versus discontinuous forces in orthodontic toothmovement [41–49].

The results of three comparative studies [47–49] comparingthe clinical efficacy of elastomeric chains versus springsshowed no statistically significant difference between thesetwo methods as regards orthodontic tooth movement, despitethe rapid movement observed with the springs. The springs’greatest advantages were their rapidity of action and their easeof clinical implementation.Samuels et al. [45] found no difference between a closed NiTispring and an elastomeric chain during canine retraction

236

utilisation en bouche, d’ou l’importance du role du milieu deconservation. La d�esinfection des chaınettes a l’autoclaveentraıne une d�eperdition de leur force.Cependant, De Genova et al. [14] ont abouti a la conclusionque les chaınettes �elastom�eriques soumises a un environne-ment thermique variable (de 15 �C a 45 �C) maintiennent uneforce r�esiduelle plus importante que celles soumises a unetemp�erature constante de 37 �C.Les chaınettes perdent moins de force dans unmilieu basiquequ’en milieu acide. Nattrass et al. [35] ont montr�e uned�eperdition de force des chaınettes �elastom�eriques plusimportante dans le cola et le curcuma que dans l’eau. Enrevanche, Eliades et al. [34] ont mont�e qu’il n’y a pas dediff�erence significative concernant la r�esistance a la tractionentre des chaınettes �etir�ees a l’air et en bouche. Teixeira et al.[38] ont montr�e que l’immersion de la chaınette dans l’acidephosphorique ou l’acide citrique n’influence pas la d�egradationde la force lib�er�ee par cet outil. Ramazanzadeh et al. [39] ontconclu que le rincage quotidien de la bouche avec la solutionNaF n’affecte pas les propri�et�es de la force lib�er�ee par lachaınette. Jefferies et Von Fraunhofer [32] ont conclu quel’utilisation d’une solution alcaline de glutarald�ehyde n’alt�erepas les propri�et�es de la chaınette, mais au contraire peut etreune solution ad�equate pour la d�esinfection des chaınettes.Pithon et al. [40] ont montr�e que la st�erilisation des �elastiquesfaite avec des moyens chimiques (alcool a 70�, glutar-ald�ehyde) ou des moyens thermiques (autoclave, micro-ondes) entraıne une augmentation statiquement significativede la cytotoxicit�e de l’�elastom�ere. Cette augmentation de lacytotoxicit�e varie en fonction dumoyen utilis�e : �ethyl�ene, ultra-violet et rayons gamma.

Efficacit�e clinique de la chaınette �elastom�erique

En pratique orthodontique, la chaınette �elastom�erique est unmoyen incontournable pour d�eplacer les dents surtout entechnique d’arc droit, mais cette force n’est pas stable dansle temps ce qui engendre un probl�eme de controle th�erapeu-tique. D’apr�es la pr�esente revue de litt�erature, rassemblant 11�etudes autour de la question de l’efficacit�e clinique de lachaınette �elastom�erique (Tableau V), les auteurs ne s’accor-dent pas sur la question et l’efficacit�e clinique de la chaınetteest compar�ee avec un autre moyen d�elivrant des forcescontinues, les « ressorts », soulevant l’�eternelle discussionrapport�ee par la litt�erature entre la force continue et discon-tinue pour le d�eplacement orthodontique [41–49].Le r�esultat de trois �etudes comparatives [47–49] de l’efficacit�eclinique entre la chaınette �elastom�erique et les ressorts nemontrent aucune diff�erence statiquement significative entreces deux m�ethodes utilis�ees pour le d�eplacement dentaire,le plus grand avantage des ressorts �etant la rapidit�e et lafacilit�e de manipulation clinique.

Samuels et al. [45] n’ont trouv�e aucune diff�erence entre leressort NiTi ferm�e et la chaınette �elastom�erique pendant le



using a .01900 � .02200 steel archwire with .02200 � .02800brackets, although a 150 g and 200 g spring did providequicker retraction than the chain [46].Bousquet et al. [50] observed no statistically significant dif-ference between force decay in different types of elastomericchain over a 3-week study period. Chain behavior was statis-tically and clinically similar. Santos et al. [51] found closedNiTi springs to be better suited to orthodontic tooth movementthan elastomeric chains. Barlow and Kula [52] found that anelastomeric chain provided tooth movement similar to thatobtained with NiTi springs.

Sonis [42,44] demonstrated a significantly greater rate ofspace closure using 150 g NiTi springs versus 3/1600 Class Ielastics run from molar hook to canine hook. Certain authorsrecommended avoiding the use of elastomeric chains, onaccount of the force decay they exhibited [1]. They advisedopting instead for NiTi springs, which showed much less forcedecay [45].

Conclusion and recommendations

Elastomeric chains provide force for orthodontic tooth move-ment, but this force is not constant over time. Several studiesdescribed a rapid decay in the force generated by such devicesover time, which affected their mechanical properties andclinical efficacy (fig. 7). This decay was dependent on severalfactors including manufacturing specifications and clinicalenvironment.

[(Fig._7)TD$FIG]

Fig. 7: a: polarized-light microscopy of a chain stretchorientation of the fringes (dark areas) at the center of therings. Magnification � 2.5. Brawtley, Eliades [44].Fig. 7 : a : images en lumi�ere polaris�ee pour une chaınette

direction des franges (zones sombres) aumilieu de l’espace

Grossissement � 2,5. D’apr�es Brawtley, Eliades [44].


mouvement de recul canine sur un arc acier 0,019 � 0,022” etdes attaches en 0,022 � 0,028”, mais le ressort NiTi 150 g et200 g produit un recul plus rapide que la chaınette [46].Bousquet et al. [50] n’ont observ�e aucune diff�erence statisti-quement significative entre la d�egradation de la force lib�er�eepar les diff�erents types de chaınettes �elastom�eriques pendantla p�eriode d’�etude de trois semaines. Le comportement deschaınettes a �et�e statistiquement et cliniquement similaire.Santos et al. [51] ont trouv�e que les ressorts NiTi ferm�es�etudi�es �etaient plus ad�equats pour le d�eplacement dentaireque les chaınettes �elastom�eriques. Barlow et Kula [52] onttrouv�eque la chaınette �elastom�erique produit un d�eplacementdentaire similaire a celui des ressorts NiTi.Sonis [42,44] a r�ev�el�e un taux de la fermeture d’espaces sig-nificativement plus rapide avec l’utilisation des ressorts 150 gen nickel-titane par rapport aux �elastiques 3/16” de Classe Itendus du crochet molaire au crochet canine. Certainsauteurs recommandent d’�eviter l’utilisation de chaınettes�elastom�eriques vu le ph�enom�ene de d�egradation de la forcelib�er�ee par cet outil [1], et d’utiliser des ressorts en NiTi aveclesquels la d�eperdition de force est beaucoup moins impor-tante [45].

Conclusion et recommandations

La chaınette �elastom�erique assure la force du d�eplacementorthodontique. N�eanmoins, cette force n’est pas stable dans letemps. Plusieurs �etudes d�ecrivent une d�egradation rapide dela force lib�er�ee par cet outil dans le temps, ce qui affecte leurspropri�et�es m�ecaniques et leur efficacit�e clinique (fig. 7). Cettevariation est due a l’influence de plusieurs facteurs notammentindustriels et environnementaux.

ed at 50% for 24 hours; b: after removal. Note theintermodular link and at its junction with the modular

�etir�ee a 50 % pendant 24 h ; b : apr�es d�epose. Noter la

intermodulaire et a la liaison avec la zone des anneaux.

237


Specific recommendations have been proposed in an effort tomitigate such rapid force decay:— Andreasen and Bishara suggested overstretching the chainto further increase its initial force, but this was associated withmajor discomfort and potential complications such as rootresorption;— Kovatch et al. proposed stretching the chain more slowlyand over a longer period of time;— Rock et al. recommended extending the chain to only 50-75% of its initial length to achieve the desired force;

— Ferriter et al. suggested that maintaining oral pH below7.26 might attenuate force decay, but this proved extremelydifficult to implement (if not impossible);— Kim et al. proposed pre-stretching the chain prior to clin-ical implementation;— Santos suggested avoiding elastomeric chains and optinginstead for NiTi springs.The efficacy of elastomeric chains has been demonstratedregardless of force type (continuous/discontinuous). Theauthors of this review consider it advisable to take certainprecautions, e.g. chain force measurements via dynamometry,prior to clinical implementation and during follow-up, so as tominimize biodegradation.Alcohol disinfection may increase the toxicity of elastomericchains.

Disclosure of interest

The authors declare that they have no conflicts of interestconcerning this article.

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238

Certaines recommandations ont �et�e propos�ees afin derem�edier a ce ph�enom�ene de d�egradation rapide :— Andreasen et Bishara sugg�ere de sur-tendre la chaınettepour augmenter la force initiale mais cela cause un grandinconfort et provoque d’autres complications telles que lar�esorption radiculaire ;— Kovatch et al. proposent d’�etirer plus lentement la chaınetteet pendant une p�eriode prolong�ee ;— Rock et al. recommandent l’extension de la chaınette seu-lement de 50 % a 75 % par rapport a sa longueur initiale pourproduire une force d�esir�ee ;— Ferriter et al. sugg�erent de maintenir le pH oral en dessousde 7,26 pour r�eduire la d�egradation, mais cela est tr�es difficilea r�ealiser, voire impossible ;— Kim et al. proposent de pr�e-�etirer la chaınette avant sonutilisation clinique ;— Santos propose d’�eviter l’utilisation de chaınettes�elastom�eriques et d’utiliser des ressorts en Ni-Ti.L’efficacit�e de la chaınette a �et�e d�emontr�ee, que la force soitcontinue ou discontinue. A notre sens, certaines pr�ecautionsdoivent etre prises comme le dosage de la force lib�er�ee par lachaınette a l’aide d’un dynamom�etre avant son utilisation et aucours des controles pour minimiser les effets de labiod�egradation.Par ailleurs, la d�econtamination par l’alcool risque d’augmen-ter la toxicit�e des chaınettes �elastom�eriques.

D�eclaration d’int�erets

Les auteurs d�eclarent ne pas avoir de conflits d’int�erets enrelation avec cet article.

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Documents

Étude systématique de la dégradation de la force libérée par la chaînette élastomérique