Dentistry – Orthodontics – Bracket
Patent
1997-05-05
1998-10-13
Lucchesi, Nicholas D.
Dentistry
Orthodontics
Bracket
A61K 300
Patent
active
058203710
DESCRIPTION:
BRIEF SUMMARY
The present invention pertaining to a device for receiving and guiding arch wires and for transferring onto the tooth the forces resulting from their mechanical tension. They comprise for this purpose a pad with a concave underside, intended for being pasted onto the front face of a tooth, and a mounting and guide element for the wire that projects from the upper face of the pad. The underside of the pad is pasted onto the front surface of the tooth. In order to permit the forces exerted by the arch wire to be transferred onto the tooth, it is necessary that the adhesive bond be strong and durable. With the known tooth-position correction devices, which in most of the cases are made from stainless steel, the underside of the pad is provided for this purpose with a wire mesh which has the effect that in addition to the adhesive bond a mechanical interlock is obtained between the pad and the adhesive. In U.S. Pat. No. 5,267,854 there is described a metal bracket, which is produced by powder metallurgy processes, where blanks are first molded with the aid of a multiple mold, then removed from the mold and stabilized by sintering. The brackets so produced are provided with rodshaped projections on the underside of the pad, which slightly taper toward their outer ends in order to enable them to be removed from the mold. After the sintering process, the projections are then compressed by the action of a press die to give them a mushroom-like shape. This mushroom-like shape allows them to interlock with the adhesive used for pasting them onto the teeth. The production of these known brackets is relatively expensive, and this the more as the press die used for shaping the projections requires a counter-die adapted in shape to match the contour of the mounting and guide element of the bracket.
As an additional aspect, stainless steel brackets contain nickel. In view of reports regarding contact allergies that are said to be caused by nickel, efforts have been made to produce tooth-position correction devices from materials that do not contain any nickel. At present, titanium is the only known metallic material that can be used for medical purposes without producing any allergic reactions. But titanium is relatively difficult to work.
There have also been known brackets made from ceramics which do not produce any allergic reactions, but which are by their nature relatively brittle so that they tend to break easily.
Further, brackets have been known to be made from thermoplastic synthetic materials, i.e. from clear polycarbonate. They were originally developed because they are less noticeable in the mouth than metallic brackets. The adhesive used for pasting the brackets onto the teeth have the tendency to bite polycarbonate so that the adhesive and the pad are firmly bonded one to the other, by chemical means, whereby any mechanical interlock between the pad and the adhesive is rendered superfluous. Brackets made from polycarbonate may, therefore, have a flat underside which is favorable in terms of the removal from the mold after the molding process. Being free from nickel, brackets made from polycarbonate are substituted to an increasing extent for the previously used stainless steel brackets. Unfortunately, however, brackets made from polycarbonate lack in mechanical strength and, thus, in durability and inherent stability.
Plastic brackets known from U.S. Pat. No. 4,604,057 are provided on the underside of the pad with inclined recesses which are delimited by parallel surfaces and which are formed as part of the injection-molding process. Plastic brackets known from U.S. Pat. No. 5,254,002, are provided with a slot, which is reinforced by a metallic insert and is intended to absorb the tension forces produced by an arch wire.
Polyarylether ketones (PAEK) have vary favorable properties in terms of the invention. Non-reinforced PAEK already offers a well-balanced combination of high rigidity and strength, with good toughness, high inherent thermal stability and good kinetic friction properties. As regards its stre
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Bernhard Forster GmbH
Lucchesi Nicholas D.
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