Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-04-30
2003-05-06
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S014000, C528S015000, C528S031000, C528S032000, C528S038000, C528S012000, C524S159000, C524S588000, C264S016000, C433S214000, C424S053000, C525S478000, C525S474000
Reexamination Certificate
active
06559199
ABSTRACT:
The field of the present invention is that of organosilicon systems comprising a polyorganosiloxane composition which can be hardened into an elastomer and at least one biocidal active ingredient chosen from chlorine derivatives. The applications targeted by such systems are in particular the taking of impressions and, still more particularly, the taking of dental impressions in the context of the production of prostheses.
The present invention therefore relates to a silicone elastomer system having biocidal properties and which can be used in particular for the taking of impressions, for example dental impressions.
The subject of the invention is also a material for taking impressions, in particular dental impressions, comprising the abovementioned silicone elastomer system.
Finally, the invention is aimed at the use of the system or of the material for the taking of impressions, for example dental impressions, as well as a process for preparing the said system and/or the said material.
The notion of biocidal activity relates to the fields of hygiene, comfort and medical and paramedical applications. The use of silicone elastomers is very widespread in these fields. This is partly due to the fact that silicone elastomers offer, on the one hand, a wide diversity of chemical, mechanical and physical characteristics, and, on the other hand, a nontoxic, nonirritant and nonallergenic character. In addition, silicone elastomers constitute poor culture substrates for microorganisms, which confers on them remarkable properties with regard to hygiene.
It is moreover known that silicones of the cold-vulcanizable elastomer type which advantageously exist in the form of two components (EVF 2 or RTV 2) are particularly suitable for the art which consists in taking impressions, in reproducing and in creating forms. This is explained by the fact that these silicones are endowed with properties of fluidity and film-forming ability before crosslinking, which makes possible the taking of an impression of any model or of any form. The subsequent crosslinking which causes the hardening of the silicone elastomer makes it possible to constitute suitable moulds from the impressions. The good thermal stability of the crosslinked EVFs (or RTVs) allows the moulds made from these materials to withstand the high melting points of certain moulding materials such as metals.
The production of moulds from EVF or RTV silicone elastomer is particularly advantageous in order to obtain small series for which the cost and the period of production of the mould are not excessive, unlike what is observed when the mould is metallic.
There is a link between this “moulding” application of EVFs or RTVs and their use in the health field since dentists, chiropodists and plastic surgeons use silicone elastomers to produce moulds for dentures or for corrective forms (inserts, breast prostheses).
Thus, without limitation, EVFs or RTVs are particularly advantageous in the field of the taking of impressions, in particular dental impressions, because they are available in the non-crosslinked state under fluid- or paste-type rheologies. Moreover, they crosslink within a few minutes at room temperature; they are nontoxic and satisfy European regulations in the pharmaceutical field. However, the taking of impressions remains subject to surface or even intermass contaminations by pathogenic microorganisms and thus becomes vectors for propagation and dissemination of microbes between the dental practice and the prosthetist's laboratory.
To attempt to counteract this, it is possible to conventionally carry out a disinfection treatment of the impression material by bringing it into contact with a conventional antiseptic, for example by immersion or by spraying. This type of disinfection treatment limited to the surface is of course not completely without efficacy in the desired attempt to break the contamination chain, but it remains totally inadequate. In addition, this additional step of surface disinfection represents a constraint which practitioners can gladly do without.
In the context of a search for efficacy in the area of decontamination of these materials for taking dental impressions in particular, the solution consisting in incorporating into the material itself an antiseptic which will perform its primary function both intermass and at the surface, is also known. By way of illustration of this technical proposition, there may be mentioned European patent application EP No. 0 361 301 which describes the introduction of a biocide into an alginate-based material for taking dental impressions. Alginates are a hardly convincing alternative to the EVFs or RTVs. The biocidal agent involved exists in the form of an aqueous solution of quaternary ammonium salts and of compounds based on guanidine and its derivatives. This solution replaces the water necessary for the preparation of the alginate paste.
There is also known outside the specific application “taking of dental impressions” but still in the context of the biocidal silicone elastomers used in the hygiene and health field, European patent application EP-A-0 493 186 which describes a biocidal organosilicon system comprising:
a two-component organopolysiloxane composition which can be crosslinked at room temperature or in the presence of heat, by in particular polyaddition reactions,
as well as a biocidal system consisting of a salt of a hydracid or of an inorganic oxacid or of an organic acid derived from a linear polymeric biguanide: poly(hexamethylene-biguanide). This silicone elastomer with biocidal activity is intended to be incorporated into sponges so as to combat bacterial proliferation both during the period of storage and during the period of use of the said sponges.
There should also be mentioned in this review of the prior art French patent application 93 08 114 published under No. 2 707 660 and which relates to a silicone elastomer system obtained by crosslinking a composition comprising:
A—100 parts by weight of &agr;,&ohgr;-di(hydroxy)diorganopolysiloxane silicone;
B—from 2 to 20 parts by weight of a crosslinking silane containing a hydrolysable group;
C—from 0 to 150 parts by weight of an inorganic or organic filler;
D—1 to 150 parts by weight per 100 parts of A+B+C, of a solid inorganic or organic compound capable of releasing active chlorine in contact with water or moisture (preferably calcium hypochlorite);
E—optionally a polycondensation crosslinking catalyst.
This composition contains at least 0.01% of its weight of water provided and optionally generated intrinsically and optionally provided extrinsically. In this patent application, the use of such a system as agent for releasing active chlorine, in particular for the treatment of water, is recommended.
The elastomer silicone system according to this patent application is strictly limited to the silicone of the &agr;,&ohgr;-di(hydroxy)diorganopolysiloxane type which is crosslinkable by polycondensation. In addition, the silicone elastomer system disclosed in this patent application is described as being capable of being used for the production of seals or of films useful in the fields of hygiene and of sanitary applications. Another application envisaged in this prior art reference is that of the treatment of water. The system is in this case provided in the form of silicone matrix contained in a cartridge which gradually releases the calcium hypochlorite biocidal active ingredient. The application of the system as material for the taking of impressions, in particular dental impressions, is not at all dealt with in this patent application.
It was found that the antiseptics used within the mass of materials as described in EP-A-0 361 301, in EP-A-0 493 186 and in FR-A-2 707 660 do not meet the specifications specific to the applications of elastomer materials in the field of hygiene and health and, more particularly but without limitation, in the case of materials for taking impressions, in particular dental impressions.
The specifications considered comprise, inter alia, the following
Del Torto Marco
Pusineri Christian
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