Dentistry – Orthodontics – Means to transmit or apply force to tooth
Reexamination Certificate
2000-05-11
2002-08-13
Manahan, Todd E. (Department: 3732)
Dentistry
Orthodontics
Means to transmit or apply force to tooth
C433S024000
Reexamination Certificate
active
06431861
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an improved orthodontic archwire, and more particularly, to a vertically-acting, and optionally horizontally-acting, archwire that provides for rapid tooth positioning and overall enhanced results in orthodontic treatment.
BACKGROUND OF THE INVENTION
Orthodontic archwires are utilized to provide corrective tooth positioning forces in orthodontic treatment programs. For such purposes, archwires may be provided so as apply extrusive and/or intrusive forces to maxillary and/or mandibular bicuspids and/or incisors. Further, archwires may be employed to apply arch widening or narrowing forces.
Typically, the use of orthodontic archwires progresses in a number of phases. In a traditional first phase of treatment one or a succession of relatively flexible wires are utilized to position teeth to a first degree, followed by a second phase in which one or a succession of relatively stiff finishing archwires are employed to obtain a final desired arch form. The flexible wires utilized in phase I treatment may be generally characterized as having a relatively low modulus of elasticity in tension, including for example super elastic nickel titanium archwires, titanium molybdenum archwires and stainless steel woven, twisted or braided archwires. In contrast, phase II archwires may be generally characterized as having a relatively high modulus of elasticity in tension, including in particular monolithic stainless steel archwires arcuately configured to lie within a flat plane or to match a desired curve of spee in a passive state.
Although orthodontic archwires of the above-noted nature have been employed to yield acceptable results, the cumulative time of treatment can be quite extensive and entail a significant number of office visits. Further, depending on the type of orthodontic archwire(s) employed, undesired tooth movement may accompany intrusive/extrusive tooth movement, including in particular undesired molar tipping (e.g., crown tipping to the distal/root tipping to the mesial), molar rotation (e.g., to the distal) and molar root movement (e.g., the buccal).
SUMMARY OF THE INVENTION
In view of the foregoing, a primary objective of the present invention is to provide an orthodontic archwire that effects rapid bicuspid intrusion/extrusion and/or rapid incisor extrusion/intrusion.
An additional objective of the present invention is to address the above-noted objectives, while reducing or substantially avoiding undesired tooth movement, including undesired molar tipping, rotation and/or root movement.
Yet another objective of the present invention is to provide a multi-functional orthodontic archwire that may be utilized to achieve rapid bicuspid and/or incisor intrusion/extrusion as may be desired, while further providing for an increase or decrease of inter-canine and inter-molar distances in the maxillary and/or mandibular as may be desirable on a patient-by-patient basis.
One or more of the above-noted objectives and additional advantages may be realized in an inventive orthodontic archwire that includes a central curved portion and first and second end portions extending from opposing ends of the central curved portion. The central curved portion includes a middle section and first and second intermediate sections extending from opposing ends of the middle section. In a passive state, the middle section arcuately projects one of upwardly and downwardly with respect to a reference plane (e.g., to define a shallow, upright or downward arc), and the first and second intermediate sections arcuately project oppositely to the middle section with respect to the reference plane (e.g., to define a shallow, downward or upright arc). By way of further descriptive illustration, when the arcuate middle section is oriented upward and the arcuate intermediate sections are oriented downward, a gentle saddle-like configuration is defined by the archwire. As will be further described, the opposite vertical orientations of the arcuate middle and intermediate sections provide for the deflection of such sections into opposite corresponding orientations when the archwire is activated upon installation in a patient's mouth. Such deflective activation provides the necessary vertically-acting, corrective positioning forces to effect bicuspid intrusion/extrusion and/or incisor extrusion/intrusion.
In one aspect of the present invention, the first and second end portions may be provided to extend substantially non-convergently (i.e., relative to each other) from opposing ends of the central curved portion of the archwire in both a passive state and when the archwire is installed. More particularly, in a passive state, the end portions may be provided to extend from opposing ends of the central curved portion within an angle range of between about 0° to ±30° relative to an archwire mid-line (e.g., in a plan view). In a preferred embodiment, the end portions each extend linearly from the central curved portion in a plan view.
In another related aspect of the present invention, the first and second end portions of the inventive archwire may be provided so as to extend from opposing ends of the central curved portion substantially parallel to or substantially within the reference plane of the archwire in both a passive state and when the archwire is installed. More particularly, the first and second end portions may extend from opposing ends of the central curved portion within an angle range of between about ±5° relative to the reference plane (e.g., in a side view). In one embodiment, the end portions each extend substantially linearly within or parallel to the reference plane. As will be appreciated, the reference plane of the archwire is established so that upon installation of the archwire the reference plane will assume a position substantially parallel to a desired occlusal plane.
The provision of end portions configured in accordance with one or more of the noted aspects reduces or substantially avoids the application of undesired forces to interconnected teeth during use of the inventive archwire. As such, undesired tooth movement is reduced or avoided, including, for example, undesired molar tipping, rotation and/or root movement.
In another aspect of the present invention, the arcuate middle section of the orthodontic archwire may be provided so as to have a maximum projection of between about 0.3 mm and 0.6 mm relative to the reference plane in a passive state. Further, the arcuate first and second intermediate sections may be provided to each have a maximum projection of between about 2 mm and 4 mm relative to the reference plane in a passive state.
In a related important aspect of the present invention, the archwire may be provided to have a modulus of elasticity in tension, sometimes referred to as a modulus of stiffness, of between about 2.8×10
6
and 3.2×10
6
. In a different measure, the archwire may be provided to have an ultimate tensile strength of between about 275 KSI and 330 KSI (i.e., thousand pounds per square inch), and most preferably at least about 310 KSI. Further, the archwire preferably has a round cross-section, with a diameter of between about 0.012″ and 0.022″. Square, rectangular, woven and braided configurations may also be utilized. By way of example, the archwire may be fabricated from relatively hard, high tensile metal and/or metal alloy comprising chromium, nickel, molybdenum, manganese or iron.
In a further related aspect of the invention, the inventive archwire may be provided so that upon deflected activation when installed the arcuate middle section applies a total force of between about 45 gm to 65 gm per mm of deflection to the interconnected teeth (e.g., 135 gms-195 gms applied for a 3 mm deflection). Similarly, the intermediate sections may be provided so that upon activation they each apply a total force of between about 45 gm to 65 gm per mm deflection to the interconnected teeth.
In an additional aspect of the present invention, a plurality of archwires havi
Manahan Todd #E.
Marsh & Fischmann & Breyfogle LLP
White Velton C.
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