Dentistry – Method or material for testing – treating – restoring – or... – Crown
Reexamination Certificate
2002-02-05
2003-11-25
Dawson, Robert (Department: 1712)
Dentistry
Method or material for testing, treating, restoring, or...
Crown
C433S217100, C433S222100, C433S226000, C433S228100, C526S197000, C526S198000, C526S222000, C528S088000, C528S090000, C528S091000
Reexamination Certificate
active
06652281
ABSTRACT:
For some time the goal in dental medicine has been to replace the classical filling material amalgam with composites (“plastics”). In contrast to amalgam, it is necessary in the provision with composites to use a bonding agent. This so-called bonding is applied on the prepared hard tooth substance prior to the insertion of the composite into the cavity.
One important requirement of users of dental materials is that the processing be as simple as possible, that the processing not allow any processing errors and that the desired results are always the same.
This requirement can be fulfilled at least to some degree when single component dental materials are prepared and processed.
The use of single component dental materials assumes that the polymer-forming reaction can be initiated either by supplying energy and/or through reaction with components of “active” surfaces or the surrounding atmosphere.
A typical case for the initiation of polymerization through the supply of energy is photo-induced curing of dental materials, where irradiation with light causes the decomposition of the photo initiators into polymerization initiating species.
The curing rate of such photocuring dental materials is generally very high, but curing takes place only in the areas reached by the light.
Due to the short lifespan of the polymerization initiating species, like the free radicals, it is usually only possible to realize the exposure and thus the curing at the site of the end use of the cured dental material.
This circumstance restricts the use of photocuring for dental materials. Therefore, dental materials are desired that exhibit, as single component preparations, an adequate shelf life and that can be easily “activated”.
In this respect “activability” means that the polymerization initiating species are produced in the dental materials taken from the storage container through the introduction of energy and/or through reaction with components having “active” surfaces or the surrounding atmosphere, provided that the dental materials can flow adequately freely for at least another 10 seconds following “activation” in order to guarantee an application as intended.
Therefore, the object is to propose single component dental materials that exhibit stability in storage and an adequately long processing period after “activation”.
The problem of the invention is solved by dental materials, containing monomers and/or prepolymers that are capable of a polymer-forming reaction; at least one initiating system, and optionally fillers, dyes, flow modifiers, stabilizers, ion-transferring substances, the x-ray opacity-increasing compounds or other modifiers, which are characterized in that the initiating system is produced in such a manner that, when brought into contact with oxygen, it releases species initiating the polymer-forming reaction; and the quantity of initiating system is dimensioned in such a manner that after bringing into contact with oxygen the dental materials can flow adequately freely and can be processed for at least another 10 seconds and thereafter cure to a solid.
The resulting smear layer is preferably less than 0.2 mg/cm
2
.
According to the invention, an oxygen sensitive compound is used, that when brought into contact with oxygen, can form an excited or reactive species, preferably radicals that in turn can release acid from a saline initiator by means of another reaction sequence. Said acid can initiate a polymerization reaction, in particular a cationic polymerization reaction.
This saline initiator is, for example, iodonium compounds, which, when activated, for example, by means of free radicals, can decompose into acids.
Thus, there are two initiator systems, which react with each other, to control the course of the polymerization reaction.
According to a preferred embodiment of the invention, the dental materials are taken from the sealed, oxygen-impermeable storage container and brought into contact with the ambient air within a period ranging from 1 to 120 seconds. At the same time it is expedient to provide new surfaces by filling and slightly mixing, a feature that accelerates the “activation”.
According to another embodiment of the invention, the dental materials are applied on “active” surfaces that release oxygen, whereby the oxygen can be produced, for example, through reaction of a compound, located on the surface, with a component of the liquid dental materials.
The dental materials, according to the invention, cure so as to form a polymer, whereby preferably such monomers or prepolymers are used that polymerize according to a cation chain mechanism, by means of a thiol-ene mechanism or according to a radical chain mechanism.
Combinations of several mechanisms are also possible.
Thus, the dental materials can contain monomers and prepolymers that cure by means of ring-opening polymerization, whereby the use of compounds containing at least two epoxide groups is preferred. Cycloaliphatic epoxide resins, which cure according to a cationic ring opening mechanism, constitute a class of monomers that can be used advantageously.
Typical representatives of these cycloaliphatic epoxide resins are described, for example, in the DE-A-196 48 283 A1.
The dental preparations, which cure according to a thiol-ene mechanism, contain multi-thiol compounds, like the tetramercaptopropionate of pentaerythritol, and multi-allyl compounds, like triallyl isocyanurate.
Such dental materials, based on thiol-ene systems, are described in detail in the DE-A 3837569, to which reference is made here.
Typical monomers or prepolymers that cure according to a radical chain mechanism and are used in dental materials are acrylates or methacrylates. Suitable are generally uni- or multi-functional (meth)acrylate monomers. Typical representatives of this class of compounds are alkyl(meth)acrylates, including cycloalkyl(meth)acrylates, aralkyl(meth)acrylates and 2-hydroxyalkyl(meth) acrylates, like hydroxypropyl methacrylate, hydroxyethylmethacrylate, isobornyl acrylate, isobornyl methacrylate, butyl glycol methacrylate, acetyl glycol methacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 2-phenylethylmethacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate and hexanedioldi(meth)acrylate, as described in the DE-A 4328960.
Long chained monomers, based on bisphenol A and glycidyl methacrylate or their derivatives, produced through the addition of isocyanates, as described in the U.S. Pat. No. 3,066,112, can also be used. Suitable are also the compounds of the type bisphenyl-A-diethyloxy(meth)acrylate and bisphenol-A-dipropyloxy(meth)acrylate.
Furthermore, the oligoethoxylated and oligopropoxylated bisphenol-A-diacrylic and dimethacrylic acid esters can be used. Quite suitable are also the diacrylic and dimethacrylic acid esters, which are mentioned in the DE-C 2816823 and belong to bis(hydroxymethyl)-tricyclo[5.2.1.0
2,6
]-decane, and the diacrylic and dimethacrylic acid esters of the compounds of bis(hydroxymethyl)-tricyclo [5.2.1.0
2,6
]-decane, which are extended with 1 to 3 ethylene oxide and/or propylene oxide units. This list is intended as an example and not to be understood as conclusive by any means.
Mixtures of the aforementioned monomers can also be used.
The inventive dental materials contain at least one initiating system, which upon contact with oxygen releases the species initiating the polymer-forming reaction.
Preferably the dental materials contain compounds, which are rapidly oxidized by means of oxygen, whereby free radicals are formed by this reaction or by successive reactions. Said free radicals initiate either directly the polymer formation or form, after reaction with other components of the liquid dental preparations, the species initiating the polymer-forming reactions.
Suitable classes of compounds subject to rapid oxidation by means of oxygen are, for example, substituted hydrazones and boranes.
Thus, the autoxidation of hydrazones is already described in the Report 47 (1994) pp. 3277 to 3291.
Hydraz
Eckhardt Gunther
Klettke Thomas
Luchterhandt Thomas
3M ESPE AG
Aylward D.
Dawson Robert
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