JPH02213335A - Orthodontic wire - Google Patents

Abstract

PURPOSE:To provide an orthodontic wire showing ultraelasticity at the temp. in the oral cavity and capable of being freely deformed even when no specific treatment is performed by heat-treating a TiNi alloy having a specific composition at specific temp. CONSTITUTION:A TiNi alloy substantially consisting of 50.3-52.0% of Ni and the remainder of Ti on a basis of atomic % is subjected to solution treatment and subsequently heat-treated at 400-550 deg.C. This material shows ultraelasticity at the temp. (37 deg.C) in the oral cavity and can be subjected to plastic processing at 80 deg.C or less. When the concn. of Ni is 50.3% or more, transformation temp. can be shifted by ageing but, when the concn. exceeds 52.0%, cold processing becomes difficult. When heat-treatment temp. is lower than 400 deg.C, ageing effect is not obtained and, when the temp. exceeds 550 deg.C, the ageing effect after the solution treatment decreases. The expression such that the remainder is substantially composed of Ti does not mean that the remainder is only composed of Ti and one wherein a part of Ti is substituted with other metal such as Gr, Mn, V, Zr, Cu or the like is contained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to orthodontic wires in dentistry.

BACKGROUND OF THE INVENTION Orthodontic appliances are used to correct irregular and abnormal teeth. This correction operation is performed using a wire-based instrument that can reversibly absorb and release energy as the deformation stress is unloaded. The wire used for this orthodontic appliance is mainly 18.8
It was stainless steel wire. When using 18.8 stainless steel wire, the elongation and strain that can be subjected to straightening is approximately 1%. For this reason, if excessive stretching or bending is applied, the reversible energy absorption and release function originally required for the purpose will be impaired.

In contrast, TiNi alloy wires have been found to have unusual elastic limits compared to conventional stainless steel wires.

That is, the elastic limit (maximum value of elongation strain) of the processed material is approximately 4%. Unitclc (USA) is commercializing this alloy wire (processed material) as an orthodontic wire.

However, since this wire is a processed material, it is brittle, and the load required for deformation increases almost linearly as the elongation deformation increases, causing physiological pain to patients undergoing orthodontic treatment. There were some difficulties. To alleviate this pain, it has been established that the required tooth movement is best achieved by creating an optimal force application device capable of delivering a relatively light and continuous orthodontic force.
Angel Qrthodentist, Volume 31 (1
(published in 1961). To achieve this goal, the magnitude of the force required for deformation must be small and the level of force must be constant until the appliance becomes non-functional to provide maximum response to the oral tissues. It will be done.

An example of this approach can be found in the use of NfTi-containing Ti-ear annealed material. This annealed material is obtained by performing a heat treatment at 400 to 500° C. after being subjected to a cold working area reduction rate of usually 30 to 40%. A wire subjected to such treatment can exhibit rubber-like elastic behavior at least at intra-oral temperatures. That is, the elongation strain is 5 to 6%, the amount of force required for deformation is small, and elongation is possible even with a constant deformation force, and a light continuous orthodontic force accompanying tooth movement can be supplied. That is, the elastic deformation of the wire can facilitate reversible absorption and release of energy.

[Problem to be solved by the invention]

However, this wire cannot be cooled into an orthodontic shape because it either restores its shape by being heated or spontaneously restores its shape due to its rubber-like flexibility, or both. It could not be milled and had to be heated to a temperature of about 400°C or higher in order to fix it into the desired shape. For this reason, it cannot be used in closed-loop correction devices or the like, and the use of devices that require a certain degree of curvature due to design is restricted.

Therefore, the technical object of the present invention is to solve the problems when stainless steel or TiNi alloy is used and to facilitate the supply of optimal orthodontic force.

More specifically, the NiTi annealed material allows tooth movement to occur continuously and relatively painlessly, with maximum response from the oral tissues and minimal damage to the tissues. To achieve this, the orthodontic appliance acts on the crown of the tooth to displace it while maintaining the characteristics of a preferably small force magnitude and constant force over a long period of time. When forming orthodontic appliances, from simple to very complex orthodontic shapes, it can be formed into a wide range of orthodontic shapes to provide the optimum force-to-moment ratio to provide the correct center of rotation for the tooth. An object of the present invention is to provide an orthodontic wire that can perform the following at temperatures below 80°C.

[Means for Solving the Problems] In order to solve the above problems, the orthodontic wire of the present invention has a NL of 50.3 to 52.
A TiNi alloy consisting of 0 at% and the remainder substantially of Ti exhibits superelasticity at least at oral cavity temperature (37 °C) by heat treatment at 400 to 550 °C after solution treatment,
It is also characterized by being able to be plastically worked at temperatures below 80°C.

N1, which can shift the transformation temperature by aging, as shown in Japanese Patent Application Laid-Open No. 58-151445.
The concentration was found to be 50.3 at% or more. Therefore, it is clear that the effects of the present invention can be applied to TiNi alloys containing 50.3 at% or more of Ni. On the other hand, alloys containing more than 52.0 at % of Ni are difficult to cold work and are therefore not suitable for practical use, and are therefore excluded from the scope of the present invention.

In the orthodontic wire of the present invention, the heat treatment temperature is 4
The reason why the range is limited to 00 to 550°C is that if the temperature is less than 400°C, hardly any aging effect is obtained, and if it exceeds 550°C, the effect of aging after solution treatment is weakened.

Here, the expression that the remainder is substantially TL does not mean that it consists only of Ti, but also includes those in which a part of Ti is replaced with another metal.

Substituents include Cr, Mn, V, Zr, Cu, and the like. Regarding TiNi alloys using these substitutes,
TiNi alloy and TiN1X (X is CuSCr, VSM
n) is accompanied by a reverse transformation of the thermoelastic martensitic transformation,
It is well known that it exhibits a remarkable shape memory effect (
“Metals J February 13, 19H issue, 44 “Bulletin of the Japan Institute of Metals” No. 12a2 No. 3 (1973), 157, “Journal of the Japan Institute of Metals” Vol. 30, No. 2 (1975), 1
75,).

At the same time, it is well known that TiNi alloys have superelastic properties, exhibiting rubber-like flexibility (J,
Appl, Phys, 34 (1983), 475
, Tohoku University Research Report, 27 (1971), 245.
').

[Example] Next, examples of the present invention will be described.

The Tt-51 at% Ni alloy was melted by high frequency vacuum melting, then solution treated at 900°C, and processed to a diameter of 0.7 mm by hot rolling and cold working.

Thereafter, it was subjected to solution treatment at 900°C and cold worked to a diameter of 0.5 mm.

The obtained sample was heat treated at 900°C for 1 hour, and then heated at 40°C.
At each temperature of 0℃, 500℃ and 600℃, 15 minutes ~
Aging treatment was performed for 100 hours. These samples were subjected to a tensile test while changing the measurement temperature, and the temperature ranges of the shape memory region, superelastic region, and plastic deformation region were determined.

Figure 1 shows stress strain curves obtained by tensile tests of materials treated at 900°C for 1 hour, and Figure 2 shows stress strain curves obtained at 900°C for 1 hour.
It is a figure which shows the stress strain curve of the material treated at 0° C. for 1 hour.

In Figure 1, the material treated at 900°C for 1 hour is -40°C.
Superelasticity appears at 0°C, disappears at 0°C, and enters the plastic deformation region at temperatures above 0°C.

Considering a wire that exhibits superelasticity at intraoral temperature (37°C) and deforms plastically at temperatures above 37°C and within 150°C,
Materials treated at 900° C. for 1 hour are beyond the scope of the present invention. The TiNi alloy on the Ni-excessive side becomes TiNi due to aging.
It can be seen from the stress strain curve in FIG. 2 that excessive Ni precipitates such as , are formed, and the transformation temperature shifts to the higher temperature side. In other words, the temperature at which superelasticity appears is 20°C as the transformation temperature increases due to aging, and the temperature at which superelasticity disappears is:
It's over 40℃. This is the objective of the present invention.
It retains both superelasticity at temperatures above 37°C and a plastic deformation range at temperatures above 37°C.

Table 1 shows the results of heat treatment under each heat treatment condition obtained in this example.
The presence or absence of superelasticity at 7°C and the temperature at which plastic deformation begins are shown. In Table 1, an X mark indicates absence and an O mark indicates presence.

Neither the 900°C solution treated material nor the 600°C aged material exhibits superelasticity at 37°C. On the other hand, sample No. was aged without solution treatment after cold working.

For Nos. 11 to 16, good superelasticity was obtained at 37°C, but the temperature at which plastic deformation occurred was 80°C.
It's over ℃. Plastic deformation does not occur unless it exceeds 80° C. Usually, when a dentist processes orthodontic wire according to the patient's dentition, a specified heating furnace is required.

On the other hand, samples No. 2 to No. 7 according to the present invention
In this case, the plastic working temperature is 80° C. or lower in all cases, and desired processing can be performed by heating with hot water, a dryer, etc., without requiring a specified heating furnace.

In samples No. 2 in Table 1, the aging time was insufficient, so that no significant shift of the superelastic properties toward the high temperature side was observed. This shows that the alloy of this example is T i-51a
Ti-50, the lowest Ni-containing alloy for t%Ni alloys and high Ni side TiNi alloys that are affected by aging.
, 3 at% Ni alloy, the effects of the present invention can be obtained even at 400° C. for 15 minutes.

In addition, in the present invention, the transformation temperature can be changed not only by TiNi alloy but also by heat treatment as in the present invention, so TiN1X (X-Cu).

It is also applicable to alloys such as Cr, V, Mn5Zr...), and is not limited to this example.

Margin below Figure 1 εl! &5% [Effects of the Invention] As explained above, according to the present invention, it is possible to provide an orthodontic wire that exhibits superelasticity at intraoral temperature and can be freely deformed without any specific treatment. It's now possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing stress stress curves of a Ti-51 at% Ni alloy wire treated at 900°C for 1 hour according to an example of the present invention, from 50°C to +20°C; After the Ti-51at%Ni alloy according to the example was treated at 900°C for 1 hour, the aging treated material at 500°C for 1 hour was 50°C to +5
It is a figure which shows the stress strain curve at 0 degreeC. Figure 2

Claims (1)

[Claims] 1. 50.3 to 52.0 at% Ni in atomic percent
In a TiNi alloy, the remainder of which is substantially composed of Ti, by heat treatment at 400 to 550°C after solution treatment, it exhibits superelasticity at least at intra-oral temperature (37°C), and exhibits superelasticity at 80°C.
Orthodontic wire that can be plastically processed with: