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ortho1_201232 I I technique_ archwire an account of a strange alloy discovered at the Naval Ordnance Laboratory (now the Naval Surface Weapons Center). He contacted Buehler, who sent Andreasen a number of different NITINOL composi- tion in different processing conditions. Andreasen didextensiveclinicalresearchandfoundoneofthese alloys worked most effectively; he called this alloy the “memory wire” because it returned to its original shapeafterbeingbent.Andreasen’s1978articlewas the first to use the terms “shorter treatment times,” “less patient discomfort” (light forces) and “fewer archwire changes.” The wire was commercialized by Unitek Corporation and trademarked as NITINOL, identical in name to what Buehler had called it. The first commercially available wire was 50/50 percent nickel to titanium and was a shape memory alloyincompositiononly.Coldworkingbymorethan 8to10percentsuppressedtheshapememoryeffect. Nevertheless, what made it attractive compared to the competitive wires available at that time was its light force (about 1/5 to 1/6 the force per unit of de- activation)4 ,anditsincreasedworkingrangeallowed it to be used in more severely maloccluded cases without taking a permanent set. Andreasen reported his research on the thermal dynamiceffectsofNITINOLintheAngleOrthodontist in April 1985. Andreasen’s work on NITINOL earned him the 1980 Iowa Inventor of the year Award. He diedin1989attheageof55.Thiswastheverybegin- ning of nickel-titanium wires for orthodontics. SENTALLOY:ThefirstsuperelasticNiTialloy In the meantime in Japan, Dr. Fujio Miura (Fig. 6), who is the most famous orthodontic professor in Japan’s history, was making basic research on the biology of tooth movement with the objective to establish the “ideal concept of tooth movement.” He waslookingforamaterialordevicethatcoulddeliver a constant and continuous force, and research was initiated to find a material that would satisfy this requirement. In 1982, Miura and his university team made an offertoTOMYIncorporated(manufacturerofortho- dontic products) and Furukawa Electric Co. (supplier ofwirematerial)todojointresearchonanewsupere- lasticwire(Fig.7).Thisnewwirewascharacterizedby its ability to generate optimal force for tooth move- mentandabout8percentstress-inducedmartensitic transformation (superelasticity). This new NiTi alloy waslaunchedin1985underthetradenameofSENT- ALLOY (superelastic nickel-titanium alloy) (Fig. 8). SENTALLOY had the features of superelasticity and shape memory. Miura5 describes these unique properties as follows. Shapememory Phenomenon occurring in an alloy that is soft and readily amenable to change in shape at low temperaturebutcaneasilybereformedtoitsoriginal configuration when heated to a suitable transition temperature. Superelasticity A phenomenon that occurs when the stress value remains fairly constant up to a certain point of wire deformation. This is produced by stress, not by Fig. 14 Fig. 15 Fig. 16 Fig. 17