Orthodontic archwire

An archwire in orthodontics is a wire conforming to the alveolar or dental arch that can be used with dental braces as a source of force in correcting irregularities in the position of the teeth. An archwire can also be used to maintain existing dental positions; in this case it has a retentive purpose. An archwire in orthodontics is a wire conforming to the alveolar or dental arch that can be used with dental braces as a source of force in correcting irregularities in the position of the teeth. An archwire can also be used to maintain existing dental positions; in this case it has a retentive purpose. Orthodontic archwires may be fabricated from several alloys, most commonly stainless steel, nickel-titanium alloy (NiTi), and beta-titanium alloy (composed primarily of titanium and molybdenum). Noble metals such as gold, platinum, iridium, silver and their alloys were used early on in the field of Orthodontics because of their good corrosion resistance. Some of the other qualities that these alloys had were high ductility, variable stiffness (with heat), high resilience and ease of soldering. Disadvantages of these alloys were: Less elasticity, less tensile strength and greater cost. Composition of both platinum and palladium raised the melting point of the alloy and made it corrosion resistant. Copper material, along with the cold-working of the material, gave the strength to the alloy. The alloy composition of the wires made of noble metals would be Gold (55%-65%), Platinum (5-10%), Palladium (5-10%), Copper (11-18%) and Nickel (1-2%). These composition were similar that of Type IV Gold casting alloys. Edward Angle first introduced the German Silver in orthodontics in 1887 when he tried replacing the noble metals in this practice. At that time, John Nutting Farrar condemned Angle for using a material which lead to discoloration in the mouth. He then in 1888, started altering the alloy composition around the German Silver. However, Angle's composition were extremely difficult to reproduce and therefore, the usage of Silver-based alloys did not get popular in orthodontics. Angle was also known to use materials such as rubber, vulcanite, piano wire and silk thread. In 1929, stainless steel was introduced for the use of making appliances. This was the first material that truly replaced the usage of noble alloys in Orthodontics. Steel wire alloys, in comparison to the noble metals, were relatively cheaper. They also had better formability and can be readily used to be soldered and welded for fabrication of complex orthodontic appliances. The stainless steel alloys are of '18-8' austenitic type which contain Chromium (17-25%) and Nickel (8-25%) and Carbon (1-2%). Chromium in this stainless steel alloy forms a thin oxide layer which blocks the diffusion of oxygen into the alloy and allow for the corrosion resistance of this alloy. Angle used stainless steel in his last year practicing orthodontics. He used it as a ligature wire in his patient's mouth. At that time, Emil Herbst was the main opponent of the Stainless steel based alloys. According to him, he preferred using Noble alloys over stainless steel. By 1950, 300 series stainless steel alloy was used by the majority of orthodontists in United States, as European Orthodontists believed in using functional appliances such as Activator appliance with patient's malocclusions. Stainless steel archwires have high stiffness, low springiness, corrosion resistant, low range and good formability. They wires are often cheaper than the other archwires and can readily be used as 'working' archwires in an orthodontic treatment. Space closure after extractions is often done by placing these archwires in the mouth. This type of stainless steel archwire is made up multiple 0.008 in SS wires coiled together. There are 3 types: Coaxial, Braided and or Twisted. The coaxial type of archwire includes 6 strands of 0.008 in strands which are coiled together. The braided archwire includes 8 strands and twisted archwire includes 3. These wires can provide either a round shape or rectangular shaped stainless steel wire. The properties of these wires are drastically different from the traditional stainless steel archwires. They have low stiffness and can be used for initial leveling and aligning stage in orthodontics. However, due to their lower elastic limit they can be readily deformed if acted upon by any other force such as food. Arthur J. Wilcock, along with Raymond Begg, created the 'Australian archwire' in the 1940s in Australia. He was a metallurgist from Victoria, Australia. This archwire was prominently used in what is known as Begg Technique. Begg was seeking a stainless steel wire that was light, flexible stayed active for long periods of time in the mouth. The wire had high resiliency and toughness and were heat treated. The initial wire produced had dimension of 0.018in. These wires are often used in the treatment of deep bites because of their increased resistance to permanent deformation. The wire is composed of Iron (64%), Chromium (17%), Nickel (12%) and others. In the 1950s, cobalt-chromium alloy started being used in orthodontics. Rocky Mountain Orthodontics first started marketing the cobalt-chromium alloy as Elgiloy in the 1950s. It was the Elgin National Watch Company which introduced this alloy, composed of cobalt (40%), chromium (20%), iron (16%) and nickel (15%). Elgiloy offered increased resilience and strength, however, its stiffness was weak. These type of wires are still sold as alloys known as Remaloy, Forestaloy, Bioloy, Masel and Elgiloy. However, their use have decreased throughout the field of orthodontics due to the fact that no complex bends in wires are needed in today's treatment.