Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-08-27
2003-10-14
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S100000, C522S090000, C522S170000, C522S168000, C522S101000, C522S181000, C522S182000, C522S071000, C522S074000, C522S075000, C522S076000, C522S077000, C522S081000, C522S079000, C522S082000, C428S404000, C428S402000, C428S405000, C428S406000, C523S109000, C523S115000, C523S116000, C523S111000
Reexamination Certificate
active
06632853
ABSTRACT:
INTRODUCTION AND BACKGROUND
The present invention relates to a dental material and a process for producing this material. In a further aspect, the invention also relates to novel hybrid fillers.
The invention relates in particular, to dental materials formed from a polymerizable binder, for example ethylenically unsaturated monomers, epoxides, ormocers, liquid crystalline monomers, oxethanes, spiroorthoesters or spiroorthocarbonates, a catalyst for cold-, heat- or photo-polymerization and 0.5-75 wt. % in relation to the dental material of a hybrid filler (A) together with 0.0-95 wt. % in relation to the dental material of other fillers (B) and 0.0-2 wt. % of other conventional additives.
Because of the possible health risks involved in using materials containing mercury (amalgams) for tooth restoration, the search for new mercury-free preparations for this purpose has intensified.
Porous glass ceramics are known from U.S. Pat. No. 5,426,082, which are used to produce special catalysts. The ceramics cited there should have a minimum pore volume of >2000 mm
3
/g. These high pore volumes render these materials unsuitable for use as fillers in dental materials, as the resulting fillings are of low strength.
The filled inorganic porous particles disclosed in EP 48 681 are fillers consisting of amorphous glass. However, a disadvantage of the dental materials cited here is that, because of their structure and size, the particles of the filler, when applied, may penetrate the lungs, presenting the risk of an illness comparable to asbestosis.
EP-A 0 530 926 discloses dental compounds composed of a polymerizable monomer and an inorganic filler, which consist of 20-80 wt. % spherical inorganic oxide particles with an average particle size of 1.0 to 5.0 &mgr;m and 80-20 wt. % of spherical inorganic oxide particles with a particle size in the range 0.05 &mgr;m minimum and less than 1.0 &mgr;m, at least 5 wt. % of the latter component being in the range 0.05 to 0.2 &mgr;m. The inorganic particles are exclusively spherical particles of inorganic oxides of silicon, zirconium, aluminum and titanium or mixed oxides of elements from the main Groups I-IV of the Periodic Table of Elements with silicon. The spherical particles are produced e.g. by hydrolytic polymerization of alkoxysilanes and may also be surface-treated e.g. with &ggr;-methacryloxypropyl trimethoxysilane. The fillers cited here consist optionally of mixtures of particles produced from a single material.
DE 196 15 763 discloses amorphous silicon dioxide glasses loaded with monomers. The glasses are built up homogeneously, and so cannot be described as hybrid fillers according to the invention.
DE 198 46 556 proposes porous glass ceramics as filler components. A glass ceramic is deemed here to be a partially crystalline material, which is built up of amorphous SiO
2
compartments, in which compartments of crystalline oxides according to the invention are embedded (see also Ullman's Encyclopaedia of Industrial Chemistry 5
th
Ed., A12, p. 433 ff). This is therefore another mixed oxide, in other words a material built up homogeneously. The dental composites proposed hitherto have achieved the strength of amalgam fillings, and thus it is possible to use these composites on the chewing surface of teeth. However, in addition to strength, the optical quality of the composite must also be considered, which should merge as unobtrusively as possible with the surrounding natural teeth. The filler must also have sufficient radiopacity to allow the dentist to check the correct placing of the filling.
An object of the present invention was therefore to develop another dental filler, which satisfies the above criteria as well as possible.
In particular, the dental material should have improved abrasion resistance coupled with comparably good polymerization shrinkage and high strength. In addition, the polymer matrix should be prevented as far as possible from being detached from the inorganic filler by hydrolytic splitting. The dental material should also be radiopaque if desired and should be transparent enough to allow it to be inserted into the tooth cavity and light-cured in one step.
A still further object of the invention is to provide particular fillers, which are suitable for use in dental materials according to the invention.
Insofar as they relate to a dental material, the above and other objects of the invention can be achieved by a dental material as described herein.
The above and other objects relating to the particular filler of the invention can also be achieved as described herein below.
SUMMARY OF THE INVENTION
The dental material of the present invention is based on polymerizable binder, for example ethylenically unsaturated monomers, epoxides, ormocers, liquid crystalline monomers, oxethanes, spiroorthoesters or -carbonates, a catalyst for cold-, heat- and/or photo-polymerization and 0.5-75 wt. % in relation to the dental material of a hybrid filler (A) together with 0.0-95 wt. % in relation to the dental material of other fillers (B) and 0.0-2 wt. % of other conventional additives (C). The hybrid filler (A) of the invention comprises a sintered heterogeneous mixture of fillers (B) and one or more primary particles of oxides, fluorides, sulfates, phosphates, borides, nitrides, carbides and/or silicides of elements of Groups I to V of the Periodic Table of Elements. Superior dental materials are achieved in an unforeseeable manner in accordance with the invention. Reduced abrasion in particular is a striking feature of this dental material, due to the fact that the size of microfractures in the inorganic part of the filler is restricted, as each ends at the phase boundaries of the individual particles which have been sintered together (fracture control). However, filler components which are produced wholly from one material have a fracture which extends through the whole body of the filler. This increases the tendency for larger filler components to break off and thus also increases abrasion.
The relationship between the sizes of the particles in the dental material (hybrid filler (A) and filler (B) not contained in (A)) is variable. It should be established in such a way that the filler is packed as densely as possible, on the one hand to minimize polymer shrinkage and on the other to increase the strength of the dental material.
The optimum size of hybrid filler (A) according to the invention in the dental material is 1-200 &mgr;m, in particular 3-90 &mgr;m.
The ratio of the size of fillers (B) in hybrid filler (A) to one or more primary particles of oxides, fluorides, sulfates, phosphates, borides, nitrides, carbides and/or silicides of elements of Groups I to V of the Periodic Table of Elements can be chosen freely by the person skilled in the art depending on what is required of the hybrid filler and on practicability. A size ratio in the range >1:1-1:20000, preferably 1:10-1:1000, is preferred.
The ratio of the mass of fillers (B) in hybrid filler (A) to one or more primary particles of oxides, fluorides, sulfates, phosphates, borides, nitrides, carbides and/or silicides of elements of Groups I to V of the Periodic Table of Elements can be within ranges that seem obvious to the person skilled in the art from a reading of this application. A range of 25-75 wt. % of (B) in relation to the total weight of (A) is preferred.
The optionally porous components of hybrid filler (A) (filler (B) and primary particles) can be sintered together, depending on the temperature and sintering time, until the filler has been built up compactly and no longer contains any pores. Sintering for a shorter time at lower temperatures allows the pore volume and pore diameter to be chosen advantageously so as to allow special monomers to permeate the pores and form an internal monomer distribution. A filler (A) is therefore preferred, which has a pore volume of >0-2000 mm
3
/g, preferably 50-1500 mm
3
/g. It is also preferable for the pore diameter of hybrid filler (A) to be >0-1000 nm, in particular 20-100 nm.
As indicated above,
Alkemper Jochen
Binder Joachim
Hausselt Jürgen
Rentsch Harald
Ritzhaupt-Kleissl Hans-Joachim
Degussa - AG
McClendon Sanzal L
Seidleck James J.
Smith , Gambrell & Russell, LLP
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