JP2532884B2 - Orthodontic wire load level adjustment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an orthodontic wire used for correcting an maloccluded dentition into an ideal dental arch in the field of orthodontics. In particular, the present invention relates to a method for adjusting the load level of an orthodontic wire made of a superelastic Ni-Ti alloy.

“Prior Art” Ordinary orthodontic treatment is performed by fixing brackets to the tooth surface of a patient by adhesive bonding, and fixing orthodontic wires formed in an arch shape to the brackets via ligatures to fix the arch. It is carried out by applying a load generated by bending and pulling the linear wire to the tooth to be straightened.

And, as such a wire for straightening, wires made of stainless steel, cobalt chrome alloy, etc. have been used before, but since these wires have a low elastic limit due to their properties, excessive bending or the like is required. If added, permanent deformation will occur, and the purpose of orthodontic treatment will not be fulfilled, and even if the amount of deflection is slightly increased or decreased, the load will suddenly increase or decrease. When the amount changes, there is a problem that the load necessary for moving the tooth cannot be obtained.

Therefore, in the past, it was necessary to prepare several kinds of wires having different sizes, which made the treatment complicated.

Therefore, in recent years, in view of the root point of the conventional straightening wire, there is a tendency to use a wire made of a Ni-Ti alloy having a superelastic effect.

Therefore, if a wire made of such a Ni-Ti alloy is used, the load level is maintained substantially constant even if the amount of deflection changes in the superelasticity development region. The problem of will be solved once.

"Problems to be solved by the invention" However, in orthodontic treatment, the tooth is moved in the desired direction with the optimum orthodontic force according to the degree of orthodontic treatment and the treatment process without damaging the circumference of the tooth. It is strongly required to select the corrective force depending on the type of tooth to be corrected.
Even under a wire made of a Ni-Ti alloy, such a requirement must be satisfied.

Therefore, as for superelasticity of Ni-Ti alloys, as is clear from JP-A-60-203249, usually, cold-rolled raw wires are work-hardening alloys having high load levels. However, it is known that by selecting the heating time and heating temperature and performing heat treatment once under certain conditions, it is possible to develop a superelastic region with a low load level. For the above, it is possible to appropriately select the heating time and the heating temperature during the heat treatment and set a desired load level on the wire made of a superelastic Ni-Ti alloy.

However, this known technique is, so to speak, a superelastic Ni-
It is only about the first heat treatment to produce wires made of Ti-based alloys, not on the orthodontist's chair side to raise or lower the load level of the same wire that has already been heat treated.

On the other hand, in orthodontic treatment, at the beginning of the treatment, it is customary to carry out leveling with a wire having a relatively low load level and then to use the one with a higher load level in order as the treatment progresses. Therefore, in such a case, as a matter of course, the known technique shown in Japanese Patent Laid-Open No. 60-203249 described above cannot sufficiently cope with the problem. The wire with the optimum load must be prepared for each case.

Therefore, in orthodontic practice, it is strongly desired to reversibly adjust the load level of the same wire, including the increase of the load level once set, according to the progress of treatment.

"Means for solving the problem" Therefore, the present invention, as a result of performing various studies in view of the actual situation, an orthodontic wire made of a superelastic Ni-Ti alloy is first applied. Another object of the present invention is to provide a load level adjusting method capable of reversibly adjusting the load level by reheating at a temperature above or below the heat treatment temperature for a predetermined time and then cooling.

[Operation] In the present invention, an alloy consisting of Ni50.0 to 51.5 at% and the balance Ti, or 1.0 at% or less of the Ti content is added to V.Cr.Mn.
Heat treatment previously applied to the super elastic Ni-Ti alloy material itself, which has been trace-replaced with one or more elements selected from Fe, Co, Cu, Zr, Nb, Mo, Ta, and precious metals. If the material is reheated at a temperature higher than the temperature for a predetermined time and then cooled, the load level applied during the previous processing can be increased, and conversely, the temperature is lower than the temperature of the heat treatment applied earlier, and the reheat processing is performed for a predetermined time. After cooling, we found out that it has the property of being able to lower the load level applied during the previous treatment, and we applied that property to the method of adjusting the load level of the orthodontic wire made of superelastic Ni-Ti alloy. By applying it, it becomes possible for the first time to set freely the optimum correction force according to the degree of correction, the treatment process, etc., for one and the same wire.

In addition, in order to raise the load level,
In the range of 500 to 530 ℃, for 2 to 120 minutes, after re-heat treatment, it is cooled and vice versa
Reheating for 120 minutes followed by cooling proved to be extremely effective, especially for reversibly adjusting load levels.

Therefore, if the above-mentioned reheating treatment and cooling are applied to the whole or part of one wire and the load level is reversibly adjusted as necessary, Ni-Ti alloy wires with different set loads can be obtained. Since it is possible to cover most of the orthodontics by using a single wire without preparing it each time, it is by far the most suitable adjustment method to be performed at the chair side of the orthodontist. .

"Example" An alloy consisting of Ni50.5at% and the balance Ti, 0.018 "x 0.02
A 5 "square original wire was produced. This original wire needs to be sufficiently work hardened by cold drawing such as cold drawing.

Next, the original wire is molded and fixed in an arch shape, 510 ° C
Heat treatment for 2 to 5 minutes to memorize arch shape, 3
When the point bending test was performed and the load was measured, the deflection-load curve No. 0 shown in FIG. 1 was obtained.

Then, when this raw wire was heat-treated at 440 ° C. for 10 minutes using an electric furnace and then water-cooled, a three-point bending test was carried out to measure the load, and the deflection-load curve No. 1 shown in FIG. 1 was obtained. The obtained curve No. 1 is clearly lower in both the load at the maximum amount of deflection and the load in the superelasticity developing region, as compared with the curve No. 0.

Then, this heat-treated original wire is heated to 510 ° C.
The sample was heat treated for 2 minutes, cooled with water, and similarly subjected to a three-point bending test to measure the load. As a result, a deflection-load curve No. 2 shown in Fig. 1 was obtained. It is shown that the load at the maximum deflection amount and the load in the superelasticity developing region are both clearly increased as compared with those in Section 1.1.

Therefore, from the above, if the water is cooled after the reheating treatment for a predetermined time at a temperature equal to or lower than the previously applied heat treatment temperature, the load level applied in the previous treatment is lowered, and conversely, first. It was found that the load level applied in the previous treatment can be increased by water-cooling after reheating for a predetermined time at a temperature equal to or higher than the applied heat treatment temperature.

In addition, reheating and water cooling at 440 ° C for 20 minutes and reheating at 510 ° C for 2 minutes and water cooling were repeated for the original line of curve No. 0. From the chart shown in Fig. 2. As can be seen, the load level decreased and increased in sequence.

That is, the maximum deflection amount of 2 mm was 840 g, 1,080 g, 800 g, 1,020 g, which was 1120 g at the time of the first heat treatment for deposition.
・ Changes to 760g ・ 980g, and the amount of deflection when unloaded is 1m
The load of m was 625 g at the time of the first heat treatment, but 2
It changed to 80g ・ 620g ・ 240g ・ 530g ・ 170g ・ 460g. still,
In the figure, the numbers in the middle of the respective load numerical values show the respective reduction rates and increase rates.

Therefore, it was found that the load level can basically be reversibly and repeatedly adjusted, although the overall level slightly decreases each time the load level is repeatedly adjusted for the same original line.

Regarding the alloy composition, Ni50.0-51.5at%, balance Ti
Alloy consisting of, or less than 1.0at% of Ti content is V ・ Cr
・ Mn, Fe, Co, Cr, Zr, Nb, Mo, Ta, and the same results as above were obtained within the range of alloys with trace substitution with one or more elements selected from noble metals. At the same time, similar results were obtained for round and bales-shaped and other cross-section shapes.

Therefore, if such a reversible adjustment method of the load level is applied to a straightening wire made of a superelastic Ni-Ti alloy, the optimum load according to the degree of straightening and the treatment process can be obtained each time. Since it is possible to set repeatedly for one wire, for example, initially, the load level is intentionally set weakly, and the initial treatment such as leveling is performed using the wire of the weak level. If the load level of the same wire is gradually increased with the progress of the treatment and treatment, it becomes possible for the first time to cover most of the orthodontic treatment with one orthodontic wire.

In addition, this reversible adjustment method can be applied not only to the entire orthodontic wire, but to that portion as well, so that the load level can be partially raised or lowered in one wire. It is also possible to do so.

Therefore, if the load level is partially changed,
Damage to the circumference of the patient's teeth because the type of tooth to be corrected, that is, the optimum correction force for the anterior teeth, premolars and molars, is obtained from one orthodontic wire. Orthodontic treatment becomes extremely rational as a result of the quick and reliable tooth movement.

In addition, when reversibly adjusting the load level with respect to the whole or part of the straightening wire, heating means such as electric furnace heating, electric heating, salt bath, etc. will be adopted. In the case of adjusting the load level with respect to the part (1), it is preferable to grip the part of the wire that requires adjustment with a pair of energizing pliers and apply an electric potential difference between the pliers to energize and heat.

"Effects of the Invention" As described above, according to the adjusting method of the present invention, the load level can be reversibly adjusted for the whole or part of one orthodontic wire for the first time. Without having to prepare wires of different levels each time,
As a result of using a single wire for the first time, it is possible to provide an optimal correction force according to the degree of correction, the treatment process, the type of tooth to be corrected, etc., and as a result, it is possible to dramatically contribute to the improvement of orthodontic treatment.

Moreover, it is needless to say that the load level can be increased according to the progress of treatment, as described above, to more than fully meet the demands of the orthodontic clinic, but also the following advantages. Can be expected.

That is, there are cases in which an offset vent, a loop, a hook, or the like is added to the orthodontic wire based on the arch form or treatment policy of each patient. In such a case, according to the progress of the treatment as in the conventional case, if the separately prepared ones having a high load level are used in order, the above-mentioned additional elements must be accurately remanufactured for each of the other wires. Although it does not happen, under the present invention, the additional element up to now can be used as it is by simply increasing the load level of one same wire, and from this point as well, the working time on the chair side is large. It can also be shortened to the width.

[Brief description of drawings]

FIG. 1 is a flexure-load curve diagram showing the adjustment relation of the load level under the adjusting method of the present invention, and FIG. 2 is an explanatory diagram showing the reversible change of the load in the repeated adjustment of the load level.

Claims (3)

(57) [Claims] 1. An orthodontic wire made of a superelastic Ni-Ti alloy is reheated at a temperature above or below the heat treatment temperature previously applied for a predetermined time, and then cooled.
A method for adjusting the load level of an orthodontic wire, which comprises reversibly adjusting the load level. 2. 500 to 530 ° C. for increasing the load level
The method for adjusting a load level according to claim 1, further comprising the step of reheating for 2 to 120 minutes and then cooling. 3. 350 to 480 ° C. to reduce the load level
The method for adjusting a load level according to claim 1, further comprising the step of reheating for 2 to 120 minutes and then cooling.