Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-30
2002-03-26
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S209000, C523S217000, C106S035000, C433S228100, C524S492000, C524S493000, C524S701000, C524S780000, C524S783000, C524S784000, C524S785000, C524S786000, C524S847000
Reexamination Certificate
active
06362251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dental material and a process for the preparation thereof. The invention also relates to porous glass ceramics, a process for their preparation and their use.
The invention particularly relates to dental materials based on polymerizable, for example ethylenically unsaturated monomers, epoxides, ormocers, liquid crystal monomers, oxethanes, spiro-orthoesters or -carbonates as binders, a catalyst for cold, hot and/or photo-polymerization and, based on the dental material, 20-70 wt. % of an inorganic filler (A) and, based on the dental material, 0-60 wt. % of other fillers (B) and 0-2 wt. % of other conventional additives.
2. Background Information
Because of the possible health risks of mercury-containing materials (amalgams) in the field of tooth restoration, new mercury-free formulations are increasingly being sought for this intended use.
Porous glass ceramics which are used for the preparation of special catalysts are known from U.S. Pat. No. 5,426,082. The ceramics mentioned there are said to have a minimum pore volume of >2000 mm
3
/g. These high pore volumes make these substances unsuitable as filling materials in dental materials, since they result in low strength of the fillings.
The inorganic porous particles with filler contents described in EP 48 681 are fillers consisting of amorphous glasses. However, the dental materials mentioned here have the disadvantage that, because of their structure and size, the particles of the filler can enter the lungs thereby giving rise to the risk of a disease comparable to asbestosis.
EP-A 0 530 926 discloses dental compositions of a polymerizable monomer and an inorganic filler which comprises, in a proportion of 20 to 80 wt. %, spherical inorganic oxide particles with an average particle size of between 1.0 and 5.0 &mgr;m and, in a proportion of 80-20 wt. %, spherical inorganic oxide particles with a particle size in the range of at least 0.05 &mgr;m and less than 1.0 &mgr;m, at least 5 wt. % of the last component being in the range from 0.05 to 0.2 &mgr;m. The inorganic particles are exclusively spherical particles of inorganic oxides of silicon, zirconium, aluminium and titanium, or mixed oxides of metals of main groups I-IV of the periodic table with silicon. The spherical particles are prepared, for example, by hydrolytic polymerization of alkoxysilanes and can also be surface-treated for example with &ggr;-methacryloxypropyltrimethoxysilane.
DE 196 15 763 describes amorphous silicon dioxide glasses charged with monomers in dental composites.
The plastics-based tooth restoration materials which can be prepared from fillers in accordance with these last documents are inferior to amalgams in several respects:
the filling materials are not sufficiently abrasion-resistant to be used in the chewing region of teeth
the non-porous materials usually polymerized into the polymer mixtures, such as, for example, glass particles, must be coated with special coupling reagents and are often susceptible to hydrolytic cleavage reactions between the polymer material and filler. This reduces the abrasion resistance by the fillers breaking out.
filling materials which are based on porous amorphous glasses have the disadvantage that the filling materials are not opaque to X-rays and have a refractive index which differs from the surrounding polymer matrix by more than 0.02, which results in cloudy dental materials of low transparency which are difficult to cure by means of light in one step and therefore have to be polymerized into the cavity in layers in an expensive manner.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide dental materials which do not have the disadvantages of the materials of the prior art, and in particular have an increased strength and improved abrasion resistance with a comparably good polymerization shrinkage. Furthermore, the detachment of the polymer matrix from the inorganic filler caused by hydrolytic cleavage should be suppressed. The dental material should moreover be opaque to X-rays, if desired, and transparent such that the dental material can be introduced into the cavity of the tooth and cured by means of light in one working step.
It is another object of the invention to provide certain glass ceramics which are suitable as porous fillers for use in dental materials according to the invention.
This object, where it relates to a dental material, is achieved by a dental material comprising an inorganic filler (A), a porous glass ceramic having micro- and/or mesopores charged with polymerizable, ethylenically unsaturated monomers, epoxides, ormocers, liquid crystal monomers, oxethanes, spiro-orthoesters or -carbonates or with the polymerized form thereof. In preferred embodiments, filler (A) has a pore size greater than 10 nm and less than 100 nm, a particle size between 10 and 30 &mgr;m, and/or a pore volume greater than 500 mm
3
/g and less than 1500 mm
3
/g. Preferably, filler (A) comprises oxides of metals of main groups 1 to 4 and oxides of metals of the sub-groups, which are preferably present in filler (A) individually or as a mixture in an amount of between 1 and 50 wt. %
The invention also provides a process for the preparation of the dental material. In preferred embodiments of the process, filler (A) may charged with gaseous polymerizable, ethylenically unsaturated monomers or with liquid polymerizable, ethylenically unsaturated monomers before formulation of the dental material. The polymerizable, ethylenically unsaturated monomers present in filler (A) before formulation of the dental material may also be converted into their polymerized form. Filler (A) may be additionally charged with bactericidal agents, and the surface of filler (A) and/or (B) may be chemically modified.
The invention also provides a porous glass ceramic charged with polymerizable, ethylenically unsaturated monomers or with the polymerized form thereof. In preferred embodiments, the pore size of the glass ceramic is greater than 1 nm and less than 1000 nm, the particle size is between 10 and 30 &mgr;m, and/or the pore volume is greater than 150 mm
3
/g and less than 1500 mm
3
/g. The glass ceramic may comprise oxides of metals of main groups 1 to 4 and oxides of metals of the sub-groups. The oxides may be present, for example, in an amount between 1 and 50 wt. %.
The invention also provides a process for the preparation of the porous glass ceramics of the invention. In one embodiment, the glass ceramic is prepared by mixing an aqueous SiO
2
sol and one or more sols of oxides of metals of main groups 1 to 4 and of oxides of metals of the sub-groups. An aqueous solution of a salt may be added to the total sol. Furthermore, 0-10 wt. % (based on the sol mixture) of organic solvents may be added to the sol mixture. In one embodiment, the sol mixture may be spray-dried and optionally calcined at >800° C. and <1300° C.
The porous glass ceramics according to the invention may be charged with polymerizable, ethylenically unsaturated compounds and used in the dental materials according to the invention.
By providing a dental material based on polymerizable, for example ethylenically unsaturated monomers, epoxides, ormocers, liquid crystal monomers, oxethanes, spiro-orthoesters or -carbonates as binders, a catalyst for cold, hot and/or photo-polymerization and, based on the dental material, 20-70 wt. % of an inorganic filler (A) and, based on the dental material, 0-60 wt. % of other fillers (B) and 0-2 wt. % of other conventional additives, where the inorganic filler (A) is a porous glass ceramic in which the micro- and/or mesopores are charged with polymerizable, ethylenically unsaturated monomers, epoxides, ormocers, liquid crystal monomers, oxethanes, spiro-orthoesters or -carbonates or with the polymerized form thereof, a dental material which is optionally opaque to X-rays, has a transparency which can be adjusted to the particular conditions in a controlled manner and, with a good polymerization shrink
Albert Philipp
Alkemper Jochen
Dermann Klaus
Gall Corinna
Hausselt Jurgen
Degussa-Huls Aktiengesellschaft
Pillsbury & Winthrop LLP
Szekely Peter
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