Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-17
2003-09-16
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...
C523S115000, C523S116000, C523S118000, C523S200000, C523S201000, C523S204000, C523S205000, C523S207000, C523S209000, C523S213000, C523S214000, C523S216000, C523S217000, C524S492000, C524S493000, C524S494000, C524S588000, C524S779000, C524S789000, C524S847000, C524S858000, C524S860000
Reexamination Certificate
active
06620861
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an inorganic filler, particularly relates to a composition containing an organic polymer material as a matrix, particularly to an inorganic filler which is suitable for using as a filler in a dental composition, and a process for producing the same.
In addition, the present invention relates a multi-functional filler, particularly relates to a composition containing an organic polymer material as a matrix, particularly to an inorganic filler which is suitable for using as a filler in a dental composition, and a process for producing the same.
In addition, the present invention relates to a composition having a resin matrix of an organic polymer material, in particular, an organic compound filler which is suitable for using as a filler in a dental composition, as well as a process for producing the same.
Furthermore, the present invention relates to a composition having a resin matrix of an organic polymer material, in particular, a modified filler which is suitable for using as a filler in a dental composition, as well as a process for producing the same.
Furthermore, the present invention relates to a dental coloring filler which can be used in the dental field such as a crown and bridge material, a filling material, a prosthetic material and an adhesive material, light-shielding material (an opaque material), and a process for producing the same, as well as a dental composition containing the same.
BACKGROUND OF THE INVENTION
A composite restorative material which is widely used in the dental field in recent years is required to have the following properties. As such there are certain mechanical properties such as the mechanical strength which can stand a high gliding occlusal pressure upon mastication, the durability under severe conditions, the thermal expansion coefficient having the similar magnitude to that of a teeth substance and the low polymerization shrinkage for preventing stripping from a teeth substance upon curing and the like, the optical properties such as the color tone and the transparency adapted to a natural teeth and the surface smoothness and glossiness observed after polishing and the like. In addition to the bio-compatibility such as the non-toxicity, the insolubility and the low water absorbing property and the like. Moreover, particularly recently, the properties such as the sustained fluoride releasability for reinforcing a teeth substance to prevent dental caries and the radiopacity for confirming the recurrence situation of secondary caries after the treatment and for being capable of distinguishing from an enamel of a teeth substance have been required.
Composite restorative materials composed of a polymerizable monomer, a polymerization initiator, and a filler such as an inorganic material, an organic material and an organic-inorganic compound material and the like have hitherto been used for all restoration, such as filling and repairing, of a dentinal defective-part, prosthesis, artificial fang and other uses. Among these components, many have hitherto been reported on a filler. This is because the properties of a filler are thought to have the influence on the properties of a composite restorative material since the filler accounts for a large proportion of the composite restorative material.
Fillers which have used in a composite restorative material at the early stage are mainly a ground-type filler prepared by grinding a large mass such as a &agr;-quartz and a variety of glasses having an average particle size of a few microns to a few hundreds microns. When these fillers are used, they can impart various properties such as the suitable viscosity and the handling, the mechanical strength, the low polymerization shrinkage, the thermal expansion coefficient similar to that of a teeth substance to a composite restorative material.
However, such fillers have unacceptable polishability because of a large average particle size and, in particular, they have the shortcomings such as the inferior surface smoothness and the surface glossiness after polishing. In order to overcome this problem, an attempt has been tried to make an average particle size as small as possible but has not been sufficient yet.
In order to overcome this shortcoming, there has been proposed a composite restorative material using, as a filler, a ultrafme particle having an average particle size of 0.01~0.1 &mgr;m synthesized by a pyrolytic process or a a vapor phase process, for example, spray-pyrolized silica and fumed silica, and these have been used widely as a general abbreviation of MFR. This composite restorative material has the better polishability and is excellent in the surface smoothness and the surface glossiness. However, when the ultrafine particle is dispersed in a polymerizable monomer, the viscosity of the resulting paste is highly increased due to a large specific surface area and, for this reason, an amount of a filler content must be considerably suppressed. For this reason, the mechanical property of a composite restorative material, particularly, the bending strength becomes inferior. In addition, they have also a problem that the polymerization shrinkage upon the curing of a paste is relatively large and, additionally, the thermal expansion coefficient of a cured material becomes very large.
As the other filler, there are silica and silica composite oxide which are synthesized by a solution reaction such as a sol-gel process starting with an organometal compound, are narrow in the particle size distribution, are spherical and have an average particle size of 0.1 &mgr;m to a few microns. These fillers are disclosed in JP-A 59-101409 and the like. Since these fillers cause aggregation at a drying step, the surface treatment of a filler can not be performed uniformly and there is a problem on the mechanical strength and the durability such as deterioration of a material due to water absorption.
In addition, in the light of impartation of the favorable nature of each filler, there are provided hybrid-type composite materials in which an ultrafine particle of silica and a relatively large inorganic filler are combined.
For example, they are disclosed in JP-A 57-82303, J-A 57-50150, JP-A 61-148108 and the like. However, although these hybrid types improve the mechanical properties sufficiently, there is a problem that the operability is bad due to a viscous paste and they lack the smoothness after finish polishing as compared with MFR.
Then, for the purpose of satisfying the various properties necessary for a composite restorative material, many attempts have been hitherto reported to perform high density packing by fine-grinding and aggregating techniques and surface treating techniques. For example, a process of obtaining an aggregate from a solution of a metal compound and a silica sol is described in JP-A 7-196428 and a process of aggregating a metal oxide having an average particle size of not smaller than 0.05 &mgr;m and not greater than 1 &mgr;m is described in JP-A 7-196431. Although these improve the polishability, a surface treating agent such as a silane coupling agent does not act on aggregated parts, which causes a decrease in the durability due to water absorption.
According to the results of the present inventor's study, in order to obtain a sufficient polishability and mechanical properties such as the durability and the mechanical strength, it was found that the selection of a raw material of an inorganic filler, the fine-grinding and the surface treatment are a very important factor, but a variety of problems resulted. As a process of fine-grinding which has been previously performed, there is a dry-grinding process by a mechanical process with an ocsillating mill, a ball mill, a jet mill and the like. According to this process, it is difficult to obtain a particle having an average particle size of 3 &mgr;m or less and, since the particle size distribution is large, a complicated step such as separation becomes necessary. In addition, although in wet-grinding using the facility
Kimoto Katsuya
Mizuno Mitsuharu
Nakatuka Toshiyuki
Negoro Noriyuki
Yasuda Yasuhisa
Dawson Robert
Kabushiki Kaisha Shofu
Robertson Jeffrey B.
Stevens Davis Miller & Mosher L.L.P.
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