Indiana University-Purdue University Indianapolis (IUPUI) / A study was made to ascertain the effect of heat treatment, at a time-temperature ratio of three minutes at 900 F., on orthodontic 18-8 and Elgiloy steel wire with respect to the followings a) the ability of a vertical loop to resist permanent deformation when subjected to a tensile load; b) the effect of heat treatment on ductility of a steel orthodontic wire; c) the effect of heat treatment on the warpage of a orthodontic wire which has previously been formed. A standardized nine millimeter vertical loop was incorporated in the wire. Weights in increments of 100 grams were suspended from one end of the wire while the other end was firmly held in a vice. Permanent deformation as a result of a given load was determined by the amount of permanent opening of the vertical loop. The force just necessary to produce a permanent opening of the vertical loop is defined as the proportional limit. The ability of Elgiloy to resist permanent deformation due to heat treatment is enhanced as much as 66 percent. On the other hand, Elgiloy heat treatment produces the undesirable side effect of reducing ductility i.e., as high as 77 percent reduction in ductility following heat treatment. Therefore a Elgiloy steel wire cannot be altered in shape to any great extent after heat treatment. Eighteen-eight type 304 steel wire, when subjected to the same treatment, shows an increased ability to resist permanent deformation i.e. a 39 percent increase in proportional limit following heat treatment. It is significant that ductility, as determined by the cold bend test, is not significantly affected by heat treating 18-8 steel wire. The latter phenomena supports the claim of many investigators that 18-8 steel is not capable of a true heat treating transformation and therefore any improvements in elastic properties as a result of heat treatment can be considered to be due to a stress-relieving process. Ductility, as determined by the cold bend test, was found to be a highly variable property. Large variations in ductility were even found in the same feet-length of wire. Both 18-8 and Elgiloy steel wire exhibit this phenomena. Following heat treatment of Elgiloy a reduction in the variability of ductility was noted in all the wires tested. The effect of heat treatment on warpage of a previously shaped orthodontic steel wire was studied by incorporating a right angle bend in the center of a four inch section of wire. After a three week storage at a constant temperature of 98.6m to simulate mouth conditions, the angles were again measured. Any alteration in degrees from the right angle was considered to be indicative of warpage. Heat treated wires were compared to non-heat treated. Heat treatment appears to increase warpage in orthodontic steel wires; however, because of large variations no conclusive results were obtained with respect to this problem.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/34127 |
| Date | 06 1900 |
| Creators | Denver, Paul Irwin |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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