Dentistry – Orthodontics – Means to transmit or apply force to tooth
Reexamination Certificate
2001-06-21
2003-07-22
O'Connor, Cary E. (Department: 3732)
Dentistry
Orthodontics
Means to transmit or apply force to tooth
C433S018000
Reexamination Certificate
active
06595774
ABSTRACT:
The present invention relates to an orthodontic arch for making it in particular possible to effect intrusion and corporal retraction of front teeth, especially in the upper jaw, in a faster, more gentle and better controlled manner as compared to conventional arches and methods.
Orthodontics is a treatment method in dental orthopedics in which rigid appliances are used. Brackets/tapes having specific slots are applied to the teeth in the upper and lower jaws. In the Edgewise technique, preferably rectangular slots having specific dimensions and angles are provided for this purpose. So-called arches, preferably made of square wires, are inserted in the slots; along these wires or by means of these wires a torsion or angulation imparts forces to the teeth in order to bring them into a different position. A specific and difficult problem in dental orthopedics regularly occurs in case of a so-called “deep bite” in which the upper front teeth bite vertically considerably over the lower front teeth. For a correction, the upper front teeth have to be intruded vertically, i.e. they have to be pushed again back into the jaw.
A mere intrusion, however, is rarely necessary; rather, in most cases also especially the roots of the front teeth have to be moved in the distal direction, i.e. towards the back. For this purpose, the front teeth are preferably tilted by a distortion of the square arch, wherein the point of rotation is located in the slot. This is also called torque. If the square arch is distorted much, the torque normally causes an extrusion of the front, i.e. exactly the opposite of the desired movement.
An even larger degree of difficulty is caused if extraction gaps, e.g. of the teeth Nos.
4
and
5
have to be closed, wherein at the same time front teeth have to be intruded and the roots of the front teeth have to be moved corporally in the distal direction, since an even stronger torque is required for this purpose, which means at the same time an increased extrusion.
It is pointed out in general that the individual teeth in the upper and lower jaws are enumerated from the center (mesial) towards the back (distal), wherein it is in each case started with “1”. The arch according to the present invention, which is described in the following, is preferably but not necessarily realized such that it can be used for a similar, symmetrical treatment of both sides of the respective jaw.
Normally, first the canine teeth are moved in the distal direction along a continuous arch or along partial arches, thereby using loops, if, e.g., the teeth Nos.
4
or
5
are extracted, wherein the rear teeth (e.g., the teeth Nos.
5
and/or
6
) are used as an anchorage. If the teeth No.
3
are in the respective positions of the original teeth No.
4
, a relatively large gap has been generated in the distal direction of the teeth No.
2
. The front, i.e. the teeth Nos.
1
and
2
, are then commonly drawn backwards in one block. Thus, the above-mentioned vertical and angulation problems are caused in connection with anchorage problems from distal to mesial. In concrete terms, the rear anchorage teeth move too much towards the front.
This movement of the four front teeth, sometimes also of the six front teeth, in the distal direction is partially carried out by means of continuous arches to both sides of which one vertical hook is soldered. At this vertical hooks additional forces are applied by means of rubber bands which are anchored for the second time at the teeth No.
6
in the upper jaw or in the counter jaw. An example of such a conventional arrangement is shown in FIG.
1
. This arrangement to which hooks are soldered or screwed is a very rigid system which is a biological and causes considerable damage. Moreover, extreme anchorage losses are caused and it is difficult to estimate the ideally applicable forces and/or the forces being practically actually applied.
In a second conventional form of distalization of the front teeth, a square arch having vertical loops (so-called bulloops) in the distal direction of the teeth Nos.
2
or
3
is used. Such an arch is shown, for example, in DE-C-35 24 714. These loops act as a spring and are first closed and then opened by activation in order to cause a resilient tensile force. The “activation” preferably takes place by fixing the arch in the distal direction at the respective anchor tooth, e.g. the teeth Nos.
6
or
7
. The tensile force applied by the resiliency of the spring takes the front teeth with it, as shown, for example, in FIG.
2
. This arrangement and method is biologically better tolerable and more elastic; however, due to the loops there is the disadvantages that the movement in the distal direction goes along with a very strong tilting movement of the crowns in the distal direction and that due to the strong torque which is required also an extrusion of the upper front teeth has to be expected, i.e. altogether a strong tilting of the crowns downwards in the distal direction. As mentioned, these movements have negative effects and must be counteracted by other arches. This means that additional time is necessary and thus additional costs arise.
The square orthodontic arches known from the prior art, e.g. for treating the above-mentioned diseases, are all disadvantageous in that the rigid system tends to cause an overactivation and then the front teeth have to be moved in a position which is unfavorable as regards anchorage, comparable to a plough through the ground. The biological tissue is thus not offered the necessary rest phases.
U.S. Pat. No. 5,131,843 describes an orthodontic arch for imparting forces to teeth. The arch is essentially U-shaped and has a central front portion and a pair of rear portions extending at both sides of the front portion. Moreover, the arch comprises a pair of T-loop elements, wherein one of the T-loop elements is provided at any side of the mesial center line. Each of the T-loop elements has a pair of legs which extend essentially vertically and are adjacent to each other and which form an essentially closed loop at its upper end. The upper cross-loop of the T-shape extends essentially parallel to the arch.
U.S. Pat. No. 5,092,768 relates to a removable appliance for distalizing the lips or for keeping the lips away from the teeth. In order to provide an as large as possible rest area for the lips, loops are bent-in in a wire. The wire is fixed at the two molars.
U.S. Pat. No. 4,412,819 describes an orthodontic arch with front and rear portions having a different elasticity and strength, wherein a central portion made of a relatively resilient wire and rear portions made of a different and harder wire are formed. Moreover, different cross-sectional shapes can be realized in the portions.
It is the object of the present invention to provide an improved orthodontic arch which is particularly suitable for regulating the above-described phenomena in a better way.
Thus, a system should be developed which is biological, flexible, fast and better controllable, widely avoids damages as well as exhibits minimum anchorage losses.
For achieving this object, the invention starts out from the basic idea of achieving the desired improved intrusion and torque movements by means of a novel lever system, so that minimum forces have to be applied and the system is flexible. For this purpose, the arch comprises a spring hook which preferably extends obliquely to the arch direction.
It is an essential aspect of the present invention that a favorable mechanical force application (lever and at the same time spring) and not only directly action-reaction is striven for, this interaction taking into account the biological aspects more strongly. In medicine in general and thus also in dental orthopedics, the biological factors such as, e.g., blood supply play an important role in order to effect the desired change as biologically, painlessly and quickly as possible. If the blood supply is compressed, there is no movement since no transformation of the bone is possible due to the lack of blood. This means that in the bio
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