Brackets &

Figure 1: An 0.014-inch PTFE-coated FLI® Cu-NiTi (Rocky Mountain ). The PTFE coating imparts an enamel hue. Despite the extremely low coefficient of friction of PTFE, the coating is applied only to the labial surface of rectangular wires to ensure the lowest frictional resistance. Aesthetic Archwires

The evolution of aesthetic archwires to meet patient demands for invisible labial treatment

BY NEAL D. KRAVITZ, DMD, MS

espite advancements in been routinely incorporated transparent nonmetallic. Each common aesthetic archwires on Dthe aesthetics of clear in treatment due to a lack of undergoes a distinct manu- the US market are coated with orthodontic brackets, evidence-based research and facturing process, resulting in either PTFE or epoxy-resin. the appearance of orthodontic practitioner familiarity, as well as unique challenges when used in PTFE, Teflon. PTFE, archwires has changed little. concerns regarding fragmenta- treatment. commonly recognized by While increasing attention has tion of the aesthetic coating and the DuPont Co brand name been given to the use of aes- increased frictional resistance. Coated Metal Archwires Teflon®, is a synthetic polymer thetically pleasing orthodontic Currently, aesthetic archwires Coated metal archwires are consisting wholly of and archwires to complement clear can be separated into two cat- - or fluorine. Due to the strength brackets, these wires have not egories: (1) coated metal and (2) wires treated with a polytetra- of the carbon-fluorine bonds, fluoroethylene (PTFE), epoxy- PTFE is nonreactive, heat-resis- resin, parylene-polymer, or less tant, and hydrophobic. Most NEAL D. KRAVITZ, DMD, MS, is a Diplomate of commonly covering importantly, it has the third the American Board of Orthodontics, as well as to impart an enamel hue. lowest coefficient of friction of clinical faculty member at Washington Hospital Center. Kravitz has been published in numer- Manufacturers vary with regard any known solid, making it ideal ous orthodontic journals, books, and educational to the coating material, thick- for use as a nonstick coating for materials. He lectures throughout the country ness of the coating, and steps cookware, gears, plain bearings, and internationally on modern advancements within the application process or where sliding action of parts in orthodontics, lingual orthodontics, treatment to maximize aesthetics, flake- is needed. planning, and practice management. He currently maintains two orthodontic practices in South resistance, and mechanical effi- PTFE coating is applied to Riding, Va, and White Plains, Md. ciency. Currently, the two most an orthodontic wire by thermal

20 ORTHODONTIC PRODUCTS / June 2013 orthodonticproductsonline.com Brackets & Wires

spraying, a process in which are supplied by Rocky Mountain materials, including composite Therefore, a .0180-inch NiTi finely heated materials are Orthodontics as part of its aes- resins, molds, and polyurethane wire becomes .020-inch diam- sprayed in a molten condition thetic FLI® series of products. aligners. eter with an epoxy coating, or onto a surface to form a coating. Though PTFE has an extremely Epoxy-resin coating is applied alternatively, the manufacturer Thermal spraying of PTFE low coefficient of friction, it is to an orthodontic archwire may choose to use a smaller- onto an orthodontic archwire used primarily for aesthetic by electrostatic coating, or diameter wire to compensate for entails: (1) surface treatment purposes. Round FLI wires have E-coating. Electrostatic coating the thickness of the coating. of the wire by sandblasting a three-quarter circumferential is a process that uses electrostat- Epoxy-coated nickel-titanium (50-micron alumina) to support coating, and rectangular wires ically charged particles to more and stainless steel wires are sup- coating adhesion, (2) “masking” are coated only on the labial efficiently coat a workpiece. plied by G&H® Orthodontics or covering with tape areas surface to reduce the effect on Electrostatic coating of epoxy as part of its UltraestheticTM that are not be treated, (3) sliding mechanics (Figure 1, resin onto an archwire entails: series of tooth-colored arch- air-spraying atomized PTFE page 20, and Figure 2). (1) applying a high-voltage wires (Figure 3). The coating particles with clean compressed Epoxy-resin. Epoxy is a electrostatic charge to the arch- wraps around all sides of the air to coat the wire, (4) baking synthetic resin made by combin- wire, (2) applying an opposing wire and extends beyond the in a chamber furnace to cure the ing epoxide with another com- electrostatic charge to the epoxy, second molar. coating onto the wire, and (5) pound. Primarily recognized for (3) air-spraying atomized liquid The challenge with coating removal of the masking tape. its excellent adhesion, epoxies epoxy particles to the wire, and metal archwires is the lack of The PTFE layer adds a minimal display a broad range of physi- (3) baking in a chamber furnace available metal primer. Metal thickness (.0008 to .001 inch) to cal properties, such as chemical to cure the coating onto the primer allows better cohe- the archwire. resistance, electrical insulation, wire. The epoxy coating does sion between the archwire PTFE-coated -nickel- and dimensional stability. They add a more significant thick- and coating. All current metal titanium and stainless steel wires are widely used in orthodontic ness (.002 inch) to the archwire. primers contain toxins, and

Figure 3

Figure 4

Figure 2: High aesthetics of a PTFE- coated FLI® Cu-NiTi wire (Rocky Mountain Orthodontics) with FLI® twin brackets. Figure 3: UltraestheticTM NiTi archwires (G&H Wire). Figure 4: Silver primer surface treatment of the VaporTM wire helps to adhere the thinner vapor- parylene coating.

Figure 2

22 ORTHODONTIC PRODUCTS / June 2013 orthodonticproductsonline.com Figure 5: Clear and flexible nonmetallic SimpliClearTM arch (BioMers Products). These arches allow for a few millimeters of deflection to gradually move teeth. They are inserted manually and pulled gently with a plier through the distal end of the terminal bracket. Teeth align by progressing through a sequence of larger arches.

these primers do not have FDA 5). More importantly, they force levels of coated wires has led to remarkable advance- approval for use in the mouth. display the translucency and may be attributed to: (1) the ments in aesthetic archwire As such, the coating often sepa- transparency ideal for ceramic thick aesthetic coating having technology, from PTFE and rates from the archwire due to brackets. Nonmetallic arches a negative effect on the load- vapor-parylene coating to mastication and activation of are not readily available. The deflection properties, or (2) a nonmetallic fiber-reinforced digestive enzymes. Research most popular commercially manufacturer’s use of a smaller- polymers. These wires will indicates that 25% of the epoxy available nonmetallic arch diameter wire to compensate for continue to improve with coating is lost within the first is SimpliClearTM, made by the thick coating, particularly regard to appearance, durabil- month in vivo.2 Recently, new BioMers Products LLC. for epoxy-coated archwires. ity, and biomechanical control. vapor-parylene coated wires The manufacturing process Additionally, the fragmentation Nonmetallic arches such as have been introduced, which for nonmetallic arches will of the coating adds increased FRCs and SRPs are likely the use FDA-approved silver primer vary depending on the type of frictional resistance and dimin- future of aesthetic orthodontic applied to the metal archwire to polymer. Fiber-reinforced com- ishes the aesthetic benefit. wires, and they may someday better secure a thinner aesthetic posite (FRC) orthodontic arches Meanwhile, nonmetallic replace traditional nickel- coating (Figure 4, page 22). are made through a production arches are brittle and allow for titanium and stainless steel process referred to as hot- only moderate deformation. wires in patients receiving Transparent Nonmetallic drawing. Drawing is a working Excess deformation or force- ceramic braces. Orthodontists Arches process that uses tensile forces ful grip with pliers can lead to should consider incorporating Within the past 20 years, to stretch a workpiece. Hot- permanent deformation and aesthetic archwires into their significant advancements have drawing FRC arches entails: (1) irreversible cracks, referred to practices to enhance the cos- been made to create nonmetal- melting of glass pellets, (2) spin- as “craze lines.” These clear metic experience of patients lic arches whose properties ning the glass into elastic and arches are restricted with who desire invisible labial resemble metal alloys. Flexible flexible fiber strands, (3) coating regard to torque, detailing, and treatment. OP nonmetallic arches are typi- the fibers with a silane-coupling changes in arch width, and they cally made from glass spindles agent, and (4) coagulation of the are currently not suitable for Acknowledgements embedded in a polymeric matrix. glass fibers and methacrylate patients requiring consolidation The author would like to thank Some examples of nonmetallic within an acetone solution.3 or anteroposterior correction. Kenneth Hrechka of Maryland arches include fiber-reinforced Despite the disadvantages of Orthodontics, Leon Laub of Rocky polymer (FRP)3,4 or newer Disadvantages of Aesthetic these commercially available Mountain Orthodontics, and Jon self-reinforced polymer (SRP).5 Archwires nonmetallic arches, they provide Sweitzer of G&H Orthodontics These arches allow for a few Coated metal archwires with an exciting first step for what’s for their guidance in the writing millimeters of deformation and circumferential coating deliver to come. of this paper. may be suitable for leveling statistically lower loading and and aligning in patients with unloading force levels than Conclusions References for this article are Class I with mild uncoated wires of the same The growing demand for available with Orthodontic to moderate crowding (Figure nominal sizes.2,6 The lower invisible orthodontic treatment Products’ interactive edition.

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