Compositions: coating or plastic – Coating or plastic compositions – Dental
Reexamination Certificate
2001-09-28
2004-04-13
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Dental
C523S116000, C433S226000, C433S228100, C428S407000, C206S219000, C206S222000, C206S277000, C222S095000, C222S630000
Reexamination Certificate
active
06719834
ABSTRACT:
The invention relates to a single-component or multiple-component polyelectrolyte cement containing at least two reaction partners, (a) a metal-cation-releasing compound and (b) one or more polyelectrolytes capable of being converted into a solid state, wherein at least one of the polyelectrolytes is at least partially water soluble, and wherein at least one part of reaction partner (a) and/or (b) is coated with an organic surface coating agent. Moreover, the invention relates to a granulate obtained from at least one part of the formulation constituents of the polyelectrolyte cement present in solid form, wherein, in the context of an autogenous granulation process, at least one part of reaction partner (b) serves as the essential granulation agent, and the granulate disintegrates back to the primary grain on contact with the liquid formulation constituents.
Furthermore, the invention relates to processes for production of the granulate and the use of the polyelectrolyte cement as a dental material.
In the sense of the present invention, polyelectrolytes are understood to be polymers with ionically dissociable groups, which may be a component or a substituent of the polymer chain and of which the number is so great that the polymers are at least partially water soluble at least in their partially dissociated form. In the sense of the present invention, polyelectrolyte cements are understood to be materials which contain a polyelectrolyte. In particular, these polyelectrolytes should be able to react with a metal-ion-releasing compound in the context of a chelate-forming reaction, particularly preferably, an acid-base reaction
eutralization reaction. This reaction is described as a curing reaction or simply as curing. A polymerization reaction may also take place alongside this curing, if polymerizable compounds are added together with initiators suitable for the polymerization of these compounds.
Polyelectrolyte cements of this kind are obtained, for example, through the reaction of a polyalkenoic acid, in particular a polyacrylic acid, with zinc oxide or a metal-cation-releasing, so-called basic glass powder in the presence of water. These cements have been known since 1967 as polycarboxylic cements [D. C. Smith, Biomaterials 19, 467-478 (1998)] and since 1969 as (conventional) glass-ionomer cements (glass-polyalkenoate cements, GIC) [A. D. Wilson, B. E. Kent, DE 20 61 513]. Polyelectrolyte cements which contain additional polymerizable compounds and suitable initiators are, for example, synthetically modified glass-ionomer cements (see e.g. R. Mathis, I. L. Ferracane, J. Dent. Res. 66, 113 (Abstract 51) (1987)] or compomers [see e.g. EP 219 058].
The above named polyelectrolyte cements can be formulated as two-component paste-paste systems and single-component paste systems. Normally, however, the above-named polyelectrolyte cements are formulated as powder-liquid systems. In this context, the polyelectrolyte may be either in the liquid, or it may be mixed with the powder as a solid. Mixed forms, in which parts of the polyelectrolyte are contained in the powder and parts in the liquid, are also known [see, for example, GB-A-17880-72, DE-A-2319715]. Solid mixtures, in which at least one part of the polyelectrolyte is present alongside a metal-cation-releasing compound, are defined as “dry powder mixtures”.
Addition of polyelectrolytes to the powder as a solid is advantageous, for example, if additional processing time is to be gained by the dissolution of the polyelectrolyte or if the complete amount of polyelectrolyte in the solution leads to a high, and therefore no longer suitable viscosity and workability.
One disadvantage of the dry powder mixture is that in the presence of moisture, e.g. from atmospheric humidity during the storage of the product up to the time of use, a reaction takes place between the two reaction partners, i.e. the metal-cation-releasing compound and the polyelectrolyte, which slows down the curing of the cement. This means that a reliable use of the polyelectrolyte cement is no longer guaranteed, because the curing of the material increases in dependence upon the duration of storage.
This plays an important role, in particular with the hand-mixed variants of these polyelectrolyte cements, because these products are conceived for the cost-conscious user in such a manner that several applications can be implemented with the packaged material. Accordingly, the dry powder mixture is provided in small glass containers which allow access to atmospheric moisture every time the material is removed, which slows down the curing. Moreover, in time, it becomes more difficult to mix the cement because, as a result of the reaction occurring at the surface between the metal-cation-releasing compound and the polyelectrolyte in the presence of atmospheric humidity, agglomerates of increased solidity may be formed and can only be broken down with an increased input of energy during mixing.
It is possible to achieve stable curing throughout the storage period by preventing the access of moisture to the dry powder mixture. This can only be realized through more elaborate packaging: for example, polyelectrolyte cements of this kind which are offered in a mixing capsule specially developed for single application, are blister-packed in aluminium foil possibly with an additional dessicant pad. Indeed, this measure does have the desired stabilizing effect on curing, but is associated with significantly increased cost of manufacture which is therefore transferred to the consumer. Moreover, with increasing awareness of environmental matters, the consumer's acceptance of an elaborately packaged product is constantly declining.
Also, particular steps must be taken during production and packaging of the dry powder mixture in order to minimize contact with atmospheric moisture as much as possible, otherwise initial damage to the dry powder mixture may occur and this may cause difficulties with the packaging of the dry powder mixture which leads to increased expenditure on maintenance.
Another option for protecting substances essentially from environmental influences is to provide the substances to be protected with a coating.
Organic coating compounds used in the production of tablets [H. P. Fiedler, Lexicon der Hilfsstoffe für Pharmazie, Kosmetik und angrenzende Gebiete (Dictionary of excipients for pharmaceutical, cosmetics and associated areas) Editio Cantor Verlag Aulendorf, 4
th
edition, 1996, pages 1498-1500] are known in the pharmaceutical industry. Depending on the area of use of the tablet, these coating compounds may be soluble in acid (solubility in the stomach), soluble in alkali (solubility in the intestine) or soluble in water. Typical representatives of these very widely used tablet coatings are the Eudragit® types manufactured by Röhm. Eudragit® L (acid-resistant) is an acid-functional polymer, while Eudragit® E (acid soluble) provides amino groups [H. P. Fiedler, Lexicon der Hilfsstoffe für Pharmazie, Kosmetik und angrenzende Gebiete (Dictionary of excipients for pharmaceutical, cosmetics and associated areas) Editio Cantor Verlag Aulendorf, 4
th
edition, 1996, pages 596-598]. The product Copolymer 845 manufactured by ISP, which provides tertiary amino and pyrrolidon groups, is also amino-functional, however, water soluble. Coating compounds based on cellulose derivatives (such as OPADRY® II, manufactured by Colorcon, or Sepifilm, manufactured by Seppic) are also known. Copolymers, which also contain polysaccharides, such as e.g. Surelease (by Colorcon) are also used for this purpose (see product catalogues of the individual companies).
The manufacturers provide recommendations regarding the film thickness required to achieve resistance to moisture with these coating compounds. For example, Röhm recommends film thicknesses of approximately 10 &mgr;m for the production of moisture-resistant tablet coatings; this corresponds to around one milligram of coating compound per cm
2
(Eudragit® pr
Braun Peter
Glaser Jürgen
Nirschl Hermann
Stefan Klaus-Peter
3M ESPE AG
Birch & Stewart Kolasch & Birch, LLP
Marcantoni Paul
LandOfFree
Polyelectrolyte cement does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyelectrolyte cement, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyelectrolyte cement will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3252927