NL9200427A - Temperature-sensitive axial clamp for face bows - Google Patents

Abstract

This invention relates to a novel technique for adjusting face bows, which are widely used in orthondontics, in which use is made of small clamping sleeves made from memory metal. Currently, face bow wires are plastically deformed in order to carry out corrections, but this often causes them to break after they have been deformed a number of times. By making use of small clamping sleeves made from memory metal, adjustment can be carried out an unlimited number of times without any fatigue problems arising. At the temperature of use, the small clamping sleeves made from memory metal provide a rigid connection between the various components of the face bow. Cooling the memory metal to below the transition temperature releases the connection and allows the stop which pushes the face bow wire against the tooth or even the entire face bow wire to be displaced extremely easily.

Description

Temperature sensitive axial clamping for Face-Bows

This invention relates to a new type of orthodontic brace, in which axial adjustment is possible without plastic deformation of the material of the brace.

In orthodontics, many braces are used that serve to exert a corrective force on the teeth.

One of the known techniques is that of the so-called “Head-Gears” or “Face-Bows, where a so-called outer bracket is used.

The clamping force is then provided by elastic elements, which are hooked from the neck to the ends of the bracket.

At the front, this outer bracket is connected to an inner arch that is placed in the oral cavity.

At the level of the canines, this inner arch has a face-bow thread attached on both sides, which is attached at the back of the mouth to the molar to be moved.

The end of the face-bow wire is inserted into a tube, which is attached to the tooth with a strap.

In this way, the wire can exert both a backward axial force and a torque on the molar.

This is currently achieved by bending a loop in the wire that cannot slip through the pipe and thus as a stopper? serves. The free end of the loop can also be set at any angle with respect to the fixed end of the wire in order to realize the desired rotation.

In the case of intermediate treatments, the orthodontist must regularly bend the loop in order to make corrections.

Increasing or decreasing the arc length in particular is achieved by giving the loop a more or less strong curvature.

After a number of uvula treatments, this often leads to fatigue breaks in or near the loop in the wire, which leads to a lot of extra work and costs, but is also dangerous because the broken piece can shoot into the patient's throat.

The object of the invention is to avoid the large deformations of the wire by making another type of support against the tube on the molar.

Instead of making a sharp bend in the thread, a thickening in the form of a clamping bush is set up, which is able to absorb the axial forces.

The angular corrections can be achieved by bending the wire over a longer length than before, so that fewer fatigue problems occur here.

In order to perform axial corrections, the clamping bush must be able to be moved axially on the thread, or the entire thread must be moved at the fixed end, where it is fixed in the outer arch.

This can be achieved by manufacturing the clamping bush from a metal with shape memory, which is fixed at use temperature and after cooling changes properties such that the connection loosens and can thus be displaced.

This shape memory metal is in the form of a cylindrical sleeve, the inner diameter of the sleeve being smaller than the outer diameter of the wire or pipe to be inserted.

In the cold state, i.e. below the so-called transformation temperature of the memory metal, the crystal lattice changes and the sleeve can be stretched such that the wire or pipe can be slid into it with minimal force.

When heated to normal temperature, which is above the transformation temperature of the memory metal, the sleeve wants to return to the original smaller diameter and thereby becomes stuck on the wire or sleeve.

Axial shifting can then take place later by briefly cooling the memory metal sleeve with, for example, a cold gas, and then quickly performing the correction.

By applying a mark to the wire prior to cooling, it is possible to determine very precisely the distance over which the axial shift has taken place.

This is much easier and more precise to perform than when bending the wire.

Also, the shape of the face-bow wire does not change, so that corrections can be made faster.

If desired, the memory bus can be integrated with a resilient normal metal intermediate sleeve, which makes the memory metal stretch more easily upon cooling. This intermediate sleeve is then elastically deformed by the memory metal above the transformation temperature and clamped firmly on the inserted wire or tube.

Since normal metals cannot yield as much elastic elongation as memory metal, a slot can be placed in the intermediate sleeve to increase displacement and prevent plastic deformation.

When the memory bus is placed on the tube of the inner arc, in addition to the axial adjustment possibility, it is also achieved that the face-bow wire can rotate about its longitudinal axis when the memory bus is cooled.

Rotation corrections can therefore also be carried out with this.

In the drawings, some things are shown again. Fig. 1 shows a face bow outer bow. which is attached to the face-bow inner arch with a welded or soldered connection 2.

This inner arch 3, which in the current systems is of solid design with an axial bore in the end or tubular over the entire length, is firmly connected to the actual face-bow thread 7 which fits against the molar 4.

Around the molar 4 there is a band 5 and on this band there is a tube 6 that forms the connection between the molar and face-bow.

Fig. 2 shows how currently the axial support of the face-bow wire 7 against tube 6 takes place.

By changing the shape of the bend in wire 7, a certain length correction (indicated by x in fig. 2) can be realized. With repeated bending this gives the mentioned fatigue problems which lead to breakage.

Fig. 3 shows the principle of a temperature-sensitive axial clamping, with a clamping sleeve 8 of shape memory metal which, after cooling, can be axially displaced x without deforming wire 7.

Usually clamping sleeve 8 is still provided on the inside with a resilient sleeve 9 which is provided with a slot 10 in the longitudinal direction, as shown in Fig. 4.

As a result, the memory metal is stretched by the resilient bushing upon cooling and axial shifting is therefore easier.

Fig. 5a, b and c finally show how the end of the face-bow inner arch g, which is designed as a tube, can also serve as a resilient sleeve by arranging one or more slots 110 therein over a certain length.

The cannister 18 is thus placed directly on the inner arc and above the transformation temperature will firmly press the resilient ends of the inner arc onto the wire 7. This has created a kind of telescope construction.

The end of wire 7 can now be provided with the usual bend (which now no longer has to be bent anymore) or with another axial stop, such as for instance a soldered ring.

An advantage of using the bend as a stop may be that some axial elasticity is retained in the face bow.

With a construction, as shown in fig. 5, it is possible, depending on the shape of the patient's teeth, to choose a certain thread from a set and fix it in the inner arch, so that this creates a very flexible method whereby endless there are many combination options.

It goes without saying that the invention relates not only to the illustrated examples, but also to variants based on the principle of a temperature-sensitive clamping bush.

Claims (5)

Temperature-sensitive axial clamping for face bows, characterized by a memory metal element capable of forcibly returning to a pre-programmed shape upon reaching a specified temperature range, providing a stable axial connection of two sliding parts of the face bow and that upon cooling below this temperature range, properties change such that the connection of the parts of the face bow is broken, so that these parts can be displaced mutually in both axial direction and in the sense of a mutual rotation about the longitudinal axis. Temperature-sensitive clamping according to claim 1, characterized in that the memory metal element consists of a ring which can slide freely below the cover temperature over a cylindrical part of the face-bow and which, because of reaching above the cover temperature. a smaller inner diameter than the outer diameter of the said cylindrical part of the face bow is clamped thereon. Temperature-sensitive clamping according to claim 2, characterized in that a resilient sleeve is inserted into the ring of memory metal, which expands the memory metal on cooling and which is pressed in by the memory metal during heating. Temperature-sensitive clamping according to claim 3, characterized in that the resilient sleeve forms a whole with a tubular part of the face bow, in which another part of the face bow can be moved freely as a tecope construction below the wrap temperature. Temperature sensitive clamping according to claim 4, characterized in that the tubular end of the face bow has one or more longitudinal slots to increase the elastic suspension.