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1 (J Ind Orthocl Soc 2002; 35: ).::...;;;,:..=.::..==;::..;=== RESEARCH ARTICLE - Evaluation of frictional forces of different archwire materials against preadjusted edgewise stainless steel bracket, using two modes of ligation. Perman Sedigi Friction has always been one of the main factors in orthodontic movement that has occupied the clinician's mind, in his quest for better and improved treatment mechanics and results. In this test, the most commonly used archwire materials, namely, Stainless Sleel, Nickel-Titanium, Chrome-Cobalt, Copper-Niti and Beta-Titanium are tested against a Stainless Steel preadjusted edgewise bracket, using two diherent ligation methods, one by Elastic modules and the other, Stainless Steel ligature wire. Introduction: Friction is classically described as the force acting tangentially at the surfaces of the two moving bodies in contact. Friction acts parajlel to and opposing movement. It can be either static or kinetic. Orthodontists have long been aware th~t effects of forces applied by treatment appliances are reduced by friction, therefore causing the need for increase in magnitude of the force, and greater anchorage contralto counter the friction. In recent years a variety of new metal alloys have been used in the manufacture of orthodontic archwires. The straight wire edgewise appliance employing sliding mechanics has become a popular and commonly used appliance. In this context, knowledge of frictional differences between some of the available orthodontic archwire alloys would be very benelicial in orthodontic treatment. In the search for the alloy with the least amount of friction, which is the primary requisite for maximum anchorage cases, the five different alloys; Stainless Steel Nickel- Titanium Chrome-Cobalt af/oy Copper-Niti Beta-Titanium (TMA) are tested, using two modes of ligation - Elastic modules and stainless sleef ligature wire. This test will help the clinician in choosing the right type of wire with regard to his treatment requisites. In Private Practice al 11145fA, 9th Man Road, Raj Mahal Vilas, BangalOfe Review of Literature: Riley et al (1979), determined that steel ligatures generated more friction than elastic ligatures, particularly when plastic brackets were used. Kusy et al (1988)2 used laser spectroscopy to study surface roughness 01 orthodontic wires. Among the 4 wire-alloys that are commonly used in orthodontic practice, stainless steel appeared the smoothest, followed by Cobalt-Chromium, Beta Titanium and Nickel-Titanium. Kusy cautioned that surface roughness and friction in orthodontic appliance syslems have yet to be correlated. Schumacher and Bourauel (1990)3 conducted a sefies of experiments to find the frictional forces affected by the ligation technique. They inlerred that friction is determined by the sort of ligature and the way alligation and not by the dimensions of different archwires. Sims and Waters (1993)'1 compared self-ligating and two other types of ligations. The placing of figure of "8" tie increased friction than self ligating brackets, because the self-ligating brackets apply less frictional contact to the archwire than conventionally ties Siamese brackets. Burstone and Farzin (1995)5 introduced the process 01 ion implantation of archwires to reduce friction. According to them, the ions penetrate the surface of the wire on impact, building up a structure that consists 01 both the original wire and a layer of tin compound, on the surface and immediate sub-surface. This layer being hard, creates a considerable amount of compressive 107

2 108 Evaluation ollrictional forces of diherent archwire materials against... - Peyman Sedigi force in the material at the atomic level. These compressive forces and the increased surface hardness improve the fatigue resistance and ductility and reduce the coefficient of friction in the wire. Downing, Mc Cabe and Gordon (1995)6 studied the ehects of artificial saliva on the static and kinetic frictional forces of stainless steel and polycrystalline ceramic brackets in combination with inch round and x inch rectangular wires and stainless steel, Niti and Beta Tilanium archwires under constant ligature force. In all cases the artilicial saliva had the effect of increasing the frictional forces when compared with dry state. Franco, Fraunholer and Spiller (1996)' investigated the effects of Teflon coated ligatures on frictional forces and found that they produced less friction when compared to elastomers. Kusy (1996)8 in an independent study done at the university 01 Carolina, using the procedure of "i o n -i mp l antation ~ found about 54% reduction 01 frictional resistance in the 8eta-Titanium archwire materials. Materials and Methods: The tests were conducted at the Central Power Resea rch Institute (CPR I), 8angalore. The archwire materials selected are the everyday-use routine alloys, gauged at x inch dimensions. 1. Stainless Steel 2. Chrome-Cobah 3. Nickle-Titanium 4. Copper-Niti 5. Beta-Titanium (TMA) The bracket chosen for the experiment is stainless steel preadjusted edgewise with a x inch slot size. The two modes of ligation are 1. Elastic modules 2. Stainless Steelligalure wires The test is done in a dry condition and the instrument used is called.,he coal flow factor controller apparatus ~ ( Photograph1), manufactured by Ducom. The machine consists of a main body within which there is a digital screen (Photograph 2) on which the read-outs of frictional values appear. A moving segment from which an extension arm protrudes (Photograph 3). is used in pushing and sliding of the testing surfaces and objects in a straight line. It has three speeds, 0.5 mm. 0.8 mm, and 1.0 mm per minute. II has a platform on which the bracket is attached (using a composite bonding material), with the bracket slot along the long axis of the extension arm, in order to prevent any inttuence of angulation of the wire to the sial. (Photograph 3) Each archwire material is passed through the bracket and ligated, once by stainless steel ligature wire, and then by Elastic modules. One end of the wire is placed 1 mm away from Ihe extended arm, which on activation moves forwards. The distance between the bracket and the face of the arm is kept al a constant 15 mm. and the distance traveled by the wire through the bracket slot is 5 mm for each and every test. The frictional forces are measured as the resistance offered by the wire to the direction of movement of the arm. The values are displayed on the screen in Newtons (each Kilogram being equal to 9.81 Newtons). The force values are noted donn for each lest, and a new wire and new ligation done lor each test. Each archwire material is lested a total of 12 limes, using 12 different wire segments.. On testing there is an initial peak in the values. It corresponds to the static friction, which is usually higher than the rest of the values. Subsequenlly, the values lower slighlly to denote kinetic friction. There are minor liuctuations in the values, as the wife is pushed through the bracket. due to the intermittent sliding and binding of the archwire and the bracket. Photo I Photo 2 Photo 3

3 (J Ind Orthod Soc 2002; 35: ) 109 Results Table I: Frictional values recorded for archwires, using elastic modules Stainless Chrome - Beta - Nitinol Copper-Niti Steel Cobalt Titanium Mean in Newtons Mean in Grams Table II : Frictional values recorded for the archwires, using stainless steel ligature wire Stainless Chrome - Nitinol Copper-Niti Beta - Steel Cobalt Titanium lob Mean in Newtons Mean in Grams

4 110 Evaluation of frictional forces of different archwire materials against... - Peyman Sedigi Bar diagram I depicting different values for the alloys, using elastomerlc ligation Stalnle Steel Chrome Cobalt Nltlnol Copper Nitl.e... Titanium X-axis : Tested alloys V-axis : Frictional mean values in grams Bar diagram II depicting different values for the alloys used, using steel ligation Stainless Steel Chrome Cobalt Nickle TItanium Copper Nltl Beta Titanium X-axis : Tested alloys V-axis : Frictional mean values in grams Bar diagram III depicting the difference In ligation technique for each archwire material 150 jr-----""~_(1_~ X-axis : Tested alloys V -8xls : Frictional mean values in grams

5 (J Ind Orthod Soc 2002; 35:107-'12),,, Discussion: Friction between archwire and bracket has been shown to be a very important factor in tooth movement. The static and kinetic frictional force generated during sliding mechanics should be minimized to allow optimal tooth movement. Some variables that directly or indirectly contribute to the frictional force levels are as follows: 1. Archwire: Material 9 Cross-sectional shape/size1.9. 1o. 11 Surface texture 12 Stiffness 2. Ligation: Ligature wires Elastomerics Brackets: Malerial' Slot width and depth First order bends Second order bends Third order bends 4. Orthodontic appliance: Inter-bracket distance 13 Level of bracket slots between adjacent teeth Forces applied for retraction 5. Intra-oral variables: Saliva 10 Plaque Acquired pellicle Corrosion1 Fr iction of two sliding surface is more a function of surface conditions at the interface, rather than the specific material used. Surface films are the most powerful modifiers of friction. Surface roughness influences friction most directly in dry, un lubricated sliding or when only meager lubrication is present. A very smooth surface makes possible relatively large areas of adhesion that tend to grow during sliding. A very rough surface can cause high friction because of the contact and interlocking of peaks and valleys. With respect to orthodontic brackets, one can appreciate Ihe fact that the edgewise brackets due to their increased su rface contact with the wire in their slot provide a larger area of contact as compared to 8egg's or Tip-Edge types. Metal brackets, though not esthetically satisfactory, have the advantage of high fracture resistance under stress, less frictionat resistance and are cost effective. Therefore the materiat of choice for low friction is stainless steel, which is used in Ihis lest. At present orthodontic brackets are fabricated from several types of materials with varying degrees of roughness, such as ceramic, plastic, titanium, composite and polycarboxylate 10 name a few. The results obtained for this study demonstrates that the least frictional forces generated is that of Stainless Steel wires, using elastomeric modules. Also the most values were recorded using the Beta-Titanium alloy archwire, which in addition to high surface roughness, the form microwelds with the brackets in dry conditions with the process of ion implantation implemented on TMA alloys, there is a favourable 54% reduction of kinetic friction presenting a viable method of reducing the effects of friction. Burstone and Farzi n5 introduced the process of ion implantation of archwires to reduce friction. According to them, the ions penetrate the surface of the wire on impact. building up a structure that consists of both the original wire and a layer of lin compound, on the surface and immediate subsurface. This layer being hard creates a considerable amount of compressive force in the material at the atomic level. These compressive forces and the increased surface hardness improve the fatigue resistance and ductility and reduce the coefficient of friction in the wire. Conclusion: Admittedly there is no such thing as the ''idea/" archwire material that can satisfy all the criteria for an ideal treatment. and is devoid of any disadvantages. Therefore, the final say belongs to the clinician to use that knowledge, strike a compromise and improvise his objectives and treatment plan based on the choice of materials at hand, which in turn will differ from one case to another. So far the Stainless Steel alloys have been proven to allow the teasl amount of friction among the vast number of materials available to the clinician. Therefore, they do not tax the anchorage units as much as the rest of the wire-materials. In this study, the archwire material demonstrated to have the lowest frictional resistance is proved to be Stainless Steel, followed by Chrome-Cobalt alloy. Nitinol and Copper-Niti. The Beta-Titanium had the highest friclional values recorded. Therebre it is safe to say that the material of choice for maximum anchorage cases with least res istance in sliding of the wi re is Stainless Steel. Also that the ligation using elastic modules produces less amount of friction as compared to stainless stee! wire ligation.

6 112 Evaluation of frictional forces of different archwire materials against... - Peyman Sedigt Bibliography: Riley JL, Garrett SG, Moon PC : Frictional forces of ligated plastic and metal edgewise brackets. J. Dent Res. 1979; 58 : A21 Kusy RP. Whitely JQ, Mayhew MJ, Bucklhal JE : Surface roughness of orthodontic archwires via laser spectroscopy. Angle Ortho. 1988: 58: Schumacher HA, Bourauel C, Drescher D : The effect of ligation on friction between bracket and archwire. Fortscher-Keifer Orthop. 1990: 51 (2) : Sims AP. walers NE. Birnie OJ, Pethybridge RJ : A comparison 01 forces required to produce tooth movement in-vitro using two self-ligating brackets and a preadjusted bracket employing two types of ligation. Eur J. Ortho. 1993: Oct15:5: Burstone CJ, Farzin-nia Farrokh : Production of low friction and colored TMA by ion implantation. J. Clin. Ortho. 1995, July Downing A, Mc Cabe J. Gordon P : The effect of artificial saliva on the frictional forces between orthodontic brackets and archwires. B. J. Ortho. 1995: 22: 1: Franco D, Fraunhofer J. Spiller A : Frictional resistances using Tellon-coated ligatures with various brackets to archwire combinations. Angle Ortho. 1995: 65(1) : Kusy A : Independent study done at Carolina University Tidy DC : Frictional forces in fixed appliance. Am J. Orthod. 1989: 96: Anderson GF, Quevedo FA : Evaluation of friction forces in the 0.022xO.025 inch edgewise bracket in-vitro. J. Biomech. 1970: 3: Peterson L, Spencer A, Anderson G : A comparison of friction resistance for Nitinol and stainless steel wires in edgewise brackets. Quintessence Int. 1982;13: Kusy AP. Whitely JQ : Effects of surface roughness on frictional coefficients of archwires. J. Dent Aes. 1988: 67:A 1986 Frank CA, Nikolai AJ : A comparative study of frictional resistance between orthodontic bracket and archwire. Am J Orthod. 1980:78: , "An Orthodontisr Cartoon sketched by a young Dental Graduate, a sludent of Professor Nanda. This was sketched in the year By Col. Dr. B. R. Parulhi, who is a retired Army Dentist, presently settled in Chandigarh.