Dentistry – Orthodontics – Means to transmit or apply force to tooth
Reexamination Certificate
2002-03-06
2004-05-18
Lewis, Ralph A. (Department: 3732)
Dentistry
Orthodontics
Means to transmit or apply force to tooth
Reexamination Certificate
active
06736637
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to orthodontics and, in particular, intraoral arch wires employed as the force-transmitting member to move teeth.
BACKGROUND OF THE INVENTION
Modern orthodontic appliances consist of two main components: arch wires, which exert forces on the teeth, and attachments on the teeth called brackets or tubes. Arch wires are shaped by the manufacturer (preformed arch wires) or at chair-side by the orthodontist, into a curve resembling an ellipse or parabola which approximates the normal shape of the patient's dental arch. When an arch wire is secured in the slot of a bracket, or into a molar tube, it is elastically deformed. The force generated by the deformation is applied to the tooth, and is transmitted by the root of the tooth to the surrounding tissues. Bone remodeling occurs, allowing the tooth to move into better alignment with the other teeth. As alignment occurs, the arch wire becomes passive.
Before the introduction of preformed arch wires, the orthodontist fabricated the arch wire from a straight length of wire. In addition to placing the arch form in the wire, a number of other bends were necessary to accommodate the crown anatomy of the various teeth, since the machined brackets were all the same thickness from the tooth surface to the bracket slot. Prior to making the bends, marks were made while the arch wire was in the patient's mouth using an indelible pencil or wax china marker. The marks are used to located the bends.
The first preformed arch wires were introduced in the mid 1960s. Most were a basic U-shape, which saved the orthodontist time in forming a symmetrical arch wire from straight wire. In order to position the arch wire symmetrically in the mouth, a mid-line mark was necessary in the center of the arc. Soon arch wires were offered with midline marks painted on the wire or printed with FDA approved indelible ink. While these marks were helpful in the initial placement of the arch wires, they disappeared after the first visit. Fortunately, the routine arch wire bends acted as a guide to the correct positioning of the arch wire at future office visits. As technology advanced, some of the manufacturers permanently etched the midlines of their preformed arch wires. McKenna introduced a permanent midline mark bent into the arch wire in 1990 in the form of a U-shaped “dimple.”
The introduction of the “straight-wire” appliance by Dr. Lawrence Andrews in 1972 made possible the reduction or elimination of many routine arch wire bends. His system included cast stainless steel brackets and tubes individualized for the different tooth anatomy. The goal was to produce ideal tooth alignment without routine anatomical or adjustment bends in the arch wire. Nevertheless, individual variations in tooth anatomy, imprecise placement of brackets on teeth, and other factors still made some adjustment bends necessary during treatment, especially during the finishing stages.
The use of the china marker or indelible pencil to mark arch wire bends was effective, but unhygienic. Neither instrument could be sterilized. Concern about the spread of HIV, hepatitis B, and other communicable diseases led to the introduction of the disposable arch wire marker. Like the china marker, it has a wax tip. However, the disposable marker resembles a thin wooden matchstick with its pointed end dipped in red wax. In order to adhere to the stick, maintain its shape, and make several marks on the arch wire, the composition of the wax material is different from that of the china marker, and it does not adhere as well to the arch wire in the mouth.
In practice, many of the marks shift, smear, or disappear during removal of the arch wire from the mouth. Others are rubbed off as bends are placed in the arch wire. A second or third visit to the mouth is usually necessary to mark all adjustment bends. Since adjustment bends are often very small, it is difficult to use them to orient the arch wire for subsequent marks or for arch wire placement in the mouth. Errors can result in which previous bends interfere with seating of the arch wire in the brackets. Occasionally an arch wire may be turned wrong side up when removed from the mouth, leading to adjustment errors and incorrect re-insertion into the mouth. These errors extend chair time with the patient and overall treatment time, as well as increasing patient discomfort and trauma to the teeth.
Current high quality preformed ideal arch wires are shaped into an arc with proportions similar to the anatomic shape of the dental arch. Most are provided with a midline mark that is either etched or painted. The etched marks are permanent but the painted midline marks soon disappear. Except for space closing arch wires that incorporate loops, or have hooks or tubes attached, preformed arch wires have no other markings to indicate where adjustment bends should be made.
SUMMARY OF THE INVENTION
In order to solve the problems in the dental arts described above, the present arch wire has been devised. Specifically, the arch wire comprises a preformed and premarked wire having a plurality of markings along a surface thereof. The marks may be applied to the arch wire by various permanent marking processes such as chemical etching, laser etching, or laser engraving. Preferably the markings are along a top surface of the arch wire or along the labial/buccal surface. In use, a premarked arch wire is selected from a group of arch wires of different sizes to match the size of the patient's dental arch. This conveniently places the permanent markings on the arch wire between the patient's teeth where adjustment bends need to be made.
A preformed arch wire with adjustment marks etched or otherwise permanently marked on the surface eliminates the above-described problems and the problem of cross-contamination, as well as greatly increasing efficiency. It is therefore an object of the present invention to provide an arch wire system to eliminate repeated arch wire insertions to replace lost, smeared, or drifted marks. It is a further object of the invention to permit arch wire adjustment bends to be made accurately and quickly with reduction in discomfort to the patient. Other objects and advantages of the invention will become apparent to those of skill in the art from the following drawings and description of the preferred embodiment.
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Gore Gregory J.
Lewis Ralph A.
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