Dentistry – Orthodontics – Tool
Reexamination Certificate
2000-03-09
2001-09-25
Lewis, Ralph A. (Department: 3732)
Dentistry
Orthodontics
Tool
C433S159000, C081S424500, C140S106000
Reexamination Certificate
active
06293791
ABSTRACT:
The present invention relates to an orthodontic instrument and method, and, in particular, to an orthodontic instrument producing a Z-shaped bend in a wire and to a method of treatment employing a Z-shaped bend in a wire.
Orthodontics includes the installing of an orthodontic appliance, a brace or set of braces, on the teeth of a patient in order to straighten and align crooked and/or misaligned teeth. Following a treatment plan, an orthodontist installs the initial appliance by bonding or banding brackets to the surface of each tooth. Each bracket has a slot referred to as an arch wire slot, made to accept and hold an arch wire, and has a number of tie wings (typically four, but two, three or six are also common) near the arch wire slot. The force exerted between the arch wire and the bracket is transmitted to the tooth via the bracket to move the tooth towards the desired position. The arch wire is typically held in each bracket by a ligating module, i.e. an elastic ligature (a small plastic o-ring) or a thin metal ligature wire, which encircles the tie wings of the bracket, thereby securing the arch wire in the arch wire slot therein. So-called self-ligating brackets and arch wire tubes on molar bands serve a like purpose of engaging the arch wire and a bracket to exert force on a tooth.
Because the long axis of various teeth are at different angles with respect to the occlusal plane, the imaginary planar surface on which upper and lower teeth meet, different brackets are utilized for different teeth, e.g., central, lateral, cuspid, bicuspid, molar and so forth. The differences are manifest as differing angles between the bracket and tooth surface and different spacings therefrom, so as to account for the differing angulation, inclination and extraction needs of the orthodontic correction, so as to exert forces on the tooth to produce lateral movement, translation, rotation, torque, extraction and so forth.
Proper placement of the bracket on a tooth is difficult, particularly where the teeth are seriously misaligned and/or occluded. This is because the configuration of each bracket is determined by the final location and position of each tooth after the orthodontic correction is complete, not as the teeth are when the orthodontist selects and installs the brackets at the commencement of treatment. Moreover, each bracket must be bonded or banded to a tooth in precisely the proper position with respect to that particular tooth in relation to its long axis and its proper position in the mouth. Accordingly, it is difficult and requires great skill to install the brackets in exactly the right position on each tooth. The difficulty is increased where a tooth is misshaped due to an injury, poor restoration or congenital defect. While periodic orthodontic adjustment of the arch wire continues the exertion of corrective force on each tooth, it can not correct for significantly misplaced or misaligned brackets, which can only be corrected by replacement of the bracket or band, or by attempting to manually form the arch wire to include a number of bends to compensate for these discrepancies, each of which is a time-consuming and costly procedure.
Moreover, correction of inclined, angulated and derotated teeth using conventional orthodontic practice relies upon the fixed inclination and rotation, respectively, that are built into the particular bracket selected, for example, a fixed amount of 5° or 7° or 9° of correction in either inclination or rotation, or in both. If a different correction is required, or if a bracket is mis-positioned or mis-aligned, a different bracket or different bracket placement becomes necessary. This is a time-consuming and costly procedure requiring the removal of the bracket from the tooth, cleansing, drying and otherwise preparing the tooth for bonding (or banding) and bonding (or banding) the new bracket in the proper position with the required precision.
While one might attempt to correct tooth inclination and/or rotation by bending the arch wire, as is done conventionally for other corrections, there is no instrument available to make the necessary complex bends, as there are for other simpler, conventional bends such as the offset bends formed by a conventional bayonet (step) bending plier or the wire-shortening V-bend formed by a conventional stop (V bend) plier. Because the bends that are required to correct inclination and rotation must be very precise, they do not lend themselves to conventional arch wire bending practice. Even if one were to attempt to so bend the arch wire, it must be done outside the patient's mouth, thus requiring removal of the arch wire, and so would also be a time-consuming and costly procedure. In addition, a practitioner is unlikely to be able to make bends in the arch wire having the necessary precision and alignment due to the precision and complexity of the necessary bends in the arch wire. Any error in the bending produces undesired forces on the tooth in question as well as on adjacent teeth.
Accordingly, there is a need for an instrument for making a bend in an orthodontic arch wire suitable for correcting rotation and/or inclination of a tooth. It is desirable that the instrument facilitate in situ bending of the arch wire with only the arch wire removed from only a few brackets, at least for certain corrections on certain teeth.
To this end, the instrument of the present invention comprises a pair of complementary mating die for forming at least two portions of a Z-shaped bend in an wire, wherein unbent portions of the wire adjacent the Z-shaped bend are substantially co-linear; and a mechanism adapted to move the complementary mating die apart and to move the complementary mating die together, whereby the arch wire is formed to said Z shape when between said complementary mating die when said die move together.
Further, the method of adjusting an arch wire of an orthodontic appliance of the present invention comprises:
identifying a tooth to be angulated or rotated;
releasing the arch wire from a bracket on the identified tooth and from brackets on at least one tooth distal and one tooth mesial therefrom;
forming a Z-shaped bend in the arch wire using a Z-bend forming instrument, the Z-shaped bend having a longer diagonal portion between two substantially parallel shorter portions;
placing a longer diagonal portion of the Z-shaped bend into the bracket of the identified tooth; and
securing the arch wire in the brackets on the identified tooth and on the at least one tooth distal and one tooth mesial therefrom.
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Albert Einstein Healthcare Network
Dann Dorfman Herrell and Skillman, P.C.
Lewis Ralph A.
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