Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2001-09-10
2003-01-14
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...
C522S071000, C522S079000, C522S081000, C522S083000, C522S178000, C522S179000, C522S096000, C522S090000, C522S182000, C522S120000, C522S908000, C522S028000, C522S060000, C522S062000, C522S038000, C522S064000, C433S228100, C433S168100, C433S167000, C523S109000, C523S115000, C523S120000
Reexamination Certificate
active
06506815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition for denture base that is used for preparation of a denture base or a denture base plate, mending or repair of a denture, and the like. In particular, the present invention relates to a resin composition for denture base comprising a combination of a monomer component for forming a matrix after curing and a filler component.
2. Description of the Conventional Art
Hitherto, resin compositions for denture base have been consisted of a powder component made of polymethyl methacrylate or polyethyl methacrylate as a major component with a polymerization catalyst added thereto and a liquid component made of methyl methacrylate as a major component. During the use, predetermined amounts of the powder component and the liquid component are mixed with each other, and then used.
The preparation of a denture is usually carried out in the following manner. That is, an impression in an oral cavity of a patient is taken, and a gypsum cast is prepared; a denture base portion is formed by using a dental wax, etc. on the gypsum cast; the gypsum cast is set on an articulator; artificial teeth are aligned to prepare a wax denture; the wax denture is invested directly in a flask by using a gypsum investment; the wax portion is eliminated with hot water, etc., thereby forming a space for the denture base portion in the gypsum investment; a powder component and a liquid component for a resin material for denture base are weighed, and mixed with each other by means of a spatula, etc. to form a dough; the dough is filled in the space formed in the gypsum investment and then subjected to polymerization and curing; and after cooling the resulting material is removed from the gypsum investment, followed by trimming and polishing.
However, the completed denture is low in an elastic energy value, a feature of which is inherent to an acrylic resin, and is rigid and brittle in nature. Accordingly, such denture could not substantially absorb a force or an impact applied to a denture base and hence, involves such a defect that when dropped and applied with an impact, it was readily broken. Further, due to these natures, when excavating a denture from a gypsum investment during the preparation of the denture, a thin portion such as a side edge portion of the denture base, or a portion where a stress is concentrated, was liable to be broken. Moreover, since the conventional art resin compositions for denture base are required to mix the powder component and the liquid component with each other, they have such a defect that air bubbles are involved during the mixing. Such air bubbles induced a reduction in physical properties. Also, the air bubbles formed minute irregularities on the denture base surface after curing, causing staining or discoloration with a lapse of time.
In addition, during the preparation of the denture, the powder component and the liquid component for the resin composition for denture base are weighed, and mixed with each other by means of a spatula, etc.; and the mixed material is allowed to stand for a certain period of time; and when the resulting material has become into a doug-like state, it is filled. In such operation, the time until the mixed material has become into a dough-like state is liable to be influenced by an environment, and the dough-like state remains short, so that it greatly relies on an operator's perception and experiences. Further, not only the operation is difficult, but also an unpleasant feeling is imparted to the operator due to an odor or stimulation, and depending upon circumstances, the health of the operator was possibly injured.
SUMMARY OF THE INVENTION
Thus, the present invention is aimed to develop a resin composition for denture base in a one-paste state that is free from involving of air bubbles and from a reduction in physical properties and staining or discoloration with a lapse of time, because operations for weighing, and mixing is not required during the use. Further, a completed denture has a high elastic energy value, is superior in impact resistance, and when dropped and applied with an impact or a stress, is not readily broken.
In order to achieve the above-described aim, we, the present inventors made extensive and intensive investigations. As a result, they paid attention to the presence of a composite resin for dental restoration in a one-paste state as a dental resin material that does not require mixing, is superior in operability and can provide a stable performance. In another word, though the composite resin for dental restoration in a one-paste state uses an acrylic resin similar to a resin composition for denture base, since it is aimed to restore a tooth crown, an importance is attached to its hardness, bending strength and abrasion resistance. Accordingly, the composite resin for dental restoration in a one-paste state is a rigid and brittle material having a large amount of an inorganic filler or an organic-inorganic composite filler compounded therewith. Then, the inventors measured moduli of elasticity of the inorganic filler and the organic-inorganic composite filler compounded in the composite resin for dental restoration in a one-paste state and of a cured material. As a result, it has been found that the inorganic filler has a modulus of elasticity of about 5.00 GPa or more, the organic-inorganic composite filler has a modulus of elasticity of about 4.00 GPa or more, and consequently, the cured material has a modulus of elasticity of about 5.00 GPa or more. That is, it has been found that the compounding of a filler having a high modulus of elasticity ensures the hardness, bending strength and abrasion resistance of the cured material.
Thus, according to the present invention, a filler having a properly low modulus of elasticity is combined with a monomer, thereby suppressing a modulus of elasticity of a cured material to a properly low level, to complete a resin composition for denture base having a high elastic energy value so as to absorb an impact as well as being in a one-paste state without need of mixing, which is superior in operability and is free from involving of air bubbles and from a reduction in physical properties and staining or discoloration with a lapse of time.
Specifically, the resin composition for denture base according to the present invention is a resin composition for denture base in a one-paste state, comprising (a) a polymerizable monomer and/or oligomer having a modulus of elasticity at polymerization of 0.25 to 3.00 GPa, (b) an organic filler and/or an organic-inorganic composite filler having a modulus of elasticity of 0.25 to 3.00 GPa, and (c) a polymerization initiator comprising a heat polymerization type polymerization initiator and/or a photopolymerization type polymerization initiator. Of these, is preferred a resin composition for denture base in which a compounding amount of the organic filler and/or the organic-inorganic composite filler having a modulus of elasticity of 0.25 to 3.00 GPa is 1 to 75% by weight; a compounding amount of the polymerizable monomer and/or oligomer having a modulus of elasticity at polymerization of 0.25 to 3.00 GPa is from 15 to 95% by weight; and a compounding amount of the polymerization initiator comprising a heat polymerization type polymerization initiator and/or a photopolymerization type polymerization initiator is 0.05 to 5% by weight, and which may further contain from 1 to 60% by weight of an inorganic filler.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The respective components of the resin composition for denture base according to the present invention will be described below in detail.
The polymerizable monomer and/or oligomer having a modulus of elasticity at polymerization of 0.25 to 3.00 GPa as the component (a) is a component for constituting a matrix portion after curing, and monomers of a methacrylate or an acrylate having at least one unsaturated double bond are preferably used. Specific examples include methyl methacrylate, ethyl me
Kumagai Tomohiro
Shinozaki Yutaka
GC Corporation
McClendon Sanza L.
Seidleck James J.
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