Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-18
2004-06-29
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S115000, C524S081000, C524S088000, C524S431000, C524S492000
Reexamination Certificate
active
06756421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dental glass ionomer cement composition to be used for dental restoration or prevention.
2. Conventional Art
In general, dental cements are used in a number of types for the dental remedy. Representative examples include a zinc phosphate cement in which zinc oxide is reacted with phosphoric acid, a carboxylate cement in which zinc oxide is reacted with a polycarboxylic acid, a resin cement in which polymerization of an acrylic monomer is used, a calcium hydroxide cement in which calcium hydroxide is reacted with an oily component, a zinc oxide eugenol cement in which zinc oxide is reacted with eugenol, and a glass ionomer cement using a fluoroaluminosilicate glass powder and a polycarboxylic acid.
These dental cements are used in a wide range in the dental remedy. There are applications in a wide range in, for example, a luting cement for cementing a dental prosthesis, such as crown, inlay, and bridge to a tooth or for cementing an orthodontic appliance to a tooth; a filling cement for filling a dental cavity; a sealant cement for sealing pit and fissure in posterior teeth; a lining cement for lining a cavity; and a cement for core construction.
Of these dental cements, the dental glass ionomer cement has a superior affinity to living bodies and has adhesive properties to a tooth structure, and a set product thereof has translucence and is superior in esthetics. In addition, the dental glass ionomer cement has such an advantage that after set, it releases gradually fluorine ions with a lapse of time, whereby it can be expected to have a caries preventing function. Therefore, the dental glass ionomer cement is a dental cement that is most generally used at present over a wide range of dental applications.
This dental glass ionomer cement is a dental cement comprising, as major components, a fluoroaluminosilicate glass powder, a polycarboxylic acid and water. Specifically, the dental glass ionomer cement is a dental cement in which an aqueous solution of polyacrylic acid acts to the fluoroaluminosilicate glass powder to liberate metal ions (alkali metal ions, alkaline earth metal ions, and aluminum ions) in the glass, and the liberated metal ions undergo ionic bonding to a carboxyl group of the polyacrylic acid to form a crosslinking structure, whereby the cement is gelled for setting (such reaction being sometimes referred to “ionomer reaction”, hereinafter).
In addition, nowadays, a resin-reinforced dental glass ionomer cement is developed in which a dental glass ionomer cement is compounded with a polymerizable monomer, and a polymerization reaction of the monomer is used in combination with the ionomer reaction. This cement is improved in mechanical strengths, such as bending strength, and adhesive properties to a tooth structure, as compared with the conventional dental glass ionomer cements in which the setting is effected only by the ionomer reaction.
Since the dental glass ionomer cement uses the ionomer reaction, a time is required for effecting initial setting. Thus, it is impossible to proceed to the next clinical operation until finishing the initial setting. Further, it is pointed out that the dental glass ionomer cement has a defect called as sensitization to water: that is, before finishing the initial setting, when a surface of the dental glass ionomer cement mixture comes into contact with water, metal ions elute out during the setting reaction, or the content of water increases, whereby the cement surface becomes cloudy or brittle, ultimately leading to a decreased surface performance of the set product. This is due to an acid/base reaction between the fluoroaluminosilicate glass (base) and the polycarboxylic acid (acid radical) in the presence of water caused by the ionomer reaction of the dental glass ionomer cement, such reaction being sensitively influenced by water from the outside.
In order to overcome this defect, the following measure was hitherto taken. That is, the dental glass ionomer before the setting is carefully subjected to cementing, filling and application operations so that it does not come into contact with water such as saliva from the surface of the mixture and applied with a coating material called as a varnish such as resin-based materials, and after drying, a coating film is formed on the dental glass ionomer cement surface for from 20 to 25 minutes during the initial setting.
Further, the present inventors developed a method for setting a dental glass ionomer cement, by means of irradiation with a light to accelerate initial setting, the cement comprising fluoroaluminosilicate glass and polycarboxylic acid and water, without particularly undergoing an operation with a varnish or the like, and then filed an application for patent in Japanese Patent Application No. 226354/1999. According to this method, it is possible to suppress the influence by the sensitization to water to some extent. However, actually, it is difficult to completely suppress the influence by the sensitization to water, and therefore, the development of a more effective dental glass ionomer cement composition has been demanded.
An object of the invention is to provide a dental glass ionomer cement composition which, when applied to the inventors' previously proposed setting method of a dental glass ionomer cement by means of irradiation with a light to accelerate initial setting, the cement comprising fluoroaluminosilicate glass powder, a polycarboxylic acid and water.
Thus, the inventors have made further investigations as to a dental glass ionomer cement composition in which, when irradiated with light, a setting reaction by the ionomer reaction is promoted. As a result, it has been found that, when a coloring matter is contained in a dental glass ionomer cement composition, and a color is specified such that an L* value, when expressed by an L*a*b* colorimetric system in a standard illuminant D
65
, is 60 or less, setting reaction has been further promoted effectively leading to accomplishment of a dental glass ionomer cement composition of the present invention.
Specifically, the dental glass ionomer cement composition according to the present invention is a dental glass ionomer cement composition comprising a coloring matter, a color of which is specified such that an L* value, when expressed by an L*a*b* colorimetric system in a standard illuminant D
65
, is 60 or less.
In particular, it has also been found that the dental glass ionomer cement composition according to the present invention preferably has a content of the coloring matter which is from 0.1 to 5% by weight based on the whole of the composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The dental glass ionomer cement composition according to the present invention is a dental glass ionomer cement composition, a color of which is specified such that in a standard illuminant D
65
, an L* value is 60 or less, when expressed by an L*a*b* colorimetric system, by adding a coloring matter to the conventionally used dental glass ionomer cement composed mainly of a fluoroaluminosilicate glass component, a polycarboxylic acid and water and having a mechanism in which the fluoroaluminosilicate glass component and the polycarboxylic acid cause a setting reaction (namely, the ionomer reaction) in the presence of water, whereby the cement is set. The dental glass ionomer cement composition according to the present invention is used mainly where a light having a wavelength of from 320 to 780 nm as widely used in the current dental remedy, is irradiated.
In order to color a dental glass ionomer cement composition to present a tooth, a trace amount (from about 0.001 to 0.01% by weight based on the whole of the dental glass ionomer cement composition) of a coloring matter such as TiO
2
and red oxide was hitherto used. However, in such conventional dental glass ionomer cement, the above-described coloring matter was used for the purpose of realizing a tooth color. For this reason, an L* value, when expressed in an L*a*b* col
Hirota Kazuo
Okada Kaori
Sekiguchi Toshihiro
Todo Atsuhiro
GC Corporation
Yoon Tae H.
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