Dentistry – Apparatus – Having static product shaping surface
Reexamination Certificate
1999-12-07
2003-09-02
Moore, Margaret G. (Department: 1712)
Dentistry
Apparatus
Having static product shaping surface
C433S048000, C528S015000, C528S025000, C528S031000
Reexamination Certificate
active
06612836
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a molding that has a) a layer of copolymers that are crosslinkable by means of addition or condensation reactions and, optionally, b) thereon, a layer of silicone that is crosslinkable by means of addition or condensation reactions.
More particularly, the invention relates to moldings that are coated with at least one adhesion promoter and, optionally, silicone and that bond readily with a silicone that is curing. The invention relates more especially to ready-to-use single-use dental impression trays having adhesive coatings that, when a cast is taken, produce an intimate bond between a silicone impression composition and the impression tray even without using impression tray adhesives or mechanical retaining means in the impression tray. Impression trays of that kind can be charged with impression compositions at the dentist's directly, without further pre-treatment, and placed in the mouth. They bond intimately with the silicone impression composition; the resulting silicone impressions are firmly bonded to the impression trays.
BACKGROUND OF THE INVENTION
For taking impressions in the mouth with the aid of flexible impression compositions it is customary to use impression trays, so that the impression composition can be introduced into the mouth effectively and, after the impression composition has cured, the cast can be removed from the mouth, as far as possible without deformation. For that purpose, impression trays must have a very high degree of dimensional stability. Generally, they are pre-formed components made of hard plastics or of metal, having different sizes and geometries.
The bond between the impression trays and the impression compositions poses a major problem. Silicones do not by themselves adhere to plastics or metal; rather, they act as separating agents. In order to enable the silicone impression compositions, which in other respects are very suitable, to be reliably used nonetheless, attempts were firstly made to hold the impression composition in a stable manner on the tray and to prevent it from lifting off when the cast is taken out of the mouth, with the aid of mechanical retaining means, such as holes, coarse mesh plate parts, undercut ribs, bent-round tray rims etc., that is to say by mechanical means. Attempts were also made to improve the adhesion of the silicone compositions to the trays by molecular/mechanical means with the aid of solutions of viscous polymers (adhesives). Generally, such impression tray adhesives are solutions of only partially crosslinked silicones in volatile solvents. Nevertheless, no chemical reaction occurs, either between the silicone impression composition and the tray adhesive or between the tray adhesive and the impression tray.
However, all such measures for better adhesion of the silicone impression compositions to the impression trays have disadvantages. Trays having efficacious, relatively large mechanical retaining means generally consist of hard metal, are expensive and therefore can be used economically only in the form of multiple-use impression trays. Removing the silicone impression compositions after each impression is, however, laborious and time-consuming.
Trays that can be used inexpensively in the form of single-use impression trays, such as, for example, trays made of thermoplastics or aluminium, cannot, for reasons of stability, have quite as many retaining holes or undercuts. Their retaining characteristics are therefore inadequate.
The commercially available viscous adhesives have an action that is merely auxiliary: when subjected to relatively strong tensile forces, the silicone impression composition lifts off, with deformation; the viscous adhesive comes away, with many drawn-out threads being formed; and the dental cast is deformed, resulting in defective fittings.
DE 42 28 538 A1 describes surface-conditioned impression trays that, even after several impressions, are said to ensure unchanged adhesion of the impression composition. The impression trays are treated with a bonding layer of a solidified phenolic resin-methacrylate dispersion; adhesive strengths of 0.5 Mpa are mentioned. A secure bond is not possible using systems of that kind.
SUMMARY OF THE INVENTION
The invention provides moldings that bond very firmly to silicone compositions customarily used as impression compositions. The invention especially provides an impression tray to which dental impression compositions irreversibly adhere especially after a cast is taken even without the use of viscous impression tray adhesives or mechanical retaining means.
In addition, the invention provides moldings that have a layer of copolymers that are crosslinkable by means of addition or condensation reactions and, optionally, b) thereon, a layer of silicone that is crosslinkable by means of addition or condensation reactions.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive strength of dental impression compositions on the impression tray is of a similar magnitude to the cohesive strength of the impression compositions themselves so that, when the impression tray is removed from the mouth, they adhere firmly to the tray.
According to a preferred embodiment, the moulding can be coated, on top of layer a), with a firmly adhering film of cured silicones (layer b) that still have sufficient reactivity to bond firmly to further curable silicone, for example silicone of the same reaction type as dental silicones.
For the dentist, the impression trays according to the invention represent a reliable and easy to use means of perfectly positioning and fixing the silicone impression material.
The mouldings according to the invention can be characterised in that, excluding layers a) and b), they consist of at least 95% by weight of at least one plastics material and/or at least one non-noble metal.
According to an embodiment, suitable moldings for coating and also, especially, impression trays for coating comprise, or consist of, plastics materials that can be partially dissolved by readily volatile, inert solvents, such as, for example, halogenated or non-halogenated aliphatic or aromatic hydrocarbons, ethers, ketones, esters or cyclic siloxanes. Suitable impression trays are, for example, those that have also already been used hitherto because of their strength properties and/or comprise polystyrene, polycarbonate, polymethacrylate, polyvinyl chloride, polysulphone, polymethylpentene, styreneacrylonitrile or mixtures thereof.
Alternatively, the moldings and, especially, the impression trays can comprise, or consist of, one or more non-noble metals, such as aluminum or steel. According to the invention, single-use impression trays that are suitable for use may therefore be, for example, impression trays that, excluding layers a) and b), consist of at least 95% by weight of inexpensive metals, such as, for example, aluminum or steel. The surfaces of moldings of that kind can be treated with, for example, alkoxy-, alkacetoxy-, vinyl- or methacrylo-silane, phosphoric acid, phosphonic acids, multi-functional carboxylic acids or also derivatives thereof.
According to the invention, moldings and impression trays are coated with, for example, copolymers (adhesion promoters, primers) that are crosslinkable by means of addition reactions, such as those described, for example, in Application DE 199 05 224 of S & C Polymer of Feb. 9, 1999 and in Application EP 94 304 825.6 of Tokuyama Corporation of Jul. 1, 1994 for addition-crosslinking systems. With respect to the copolymers that are crosslinkable by means of addition reactions, reference is expressly made to those Applications.
Adhesion promoters (A) of that kind for impression trays being coated for addition-crosslinking impression compositions can be present, for example, in the form of solutions of polymers that contain sufficient SiH or vinyl groups. The concentrations of the solutions are, preferably, from 0.1 to 20% by weight.
According to the invention, the moldings and impression trays can also be coated with copolymers (adhesion promo
Frommer & Lawrence & Haug LLP
Moore Margaret G.
S & C Polymer, Silicon- und Composite-Spezialitation GmbH
Santucci Ronald R.
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