Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-28
2001-09-18
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...
C523S117000, C524S559000, C524S832000, C526S318100, C526S326000, C433S228100, C260S998110
Reexamination Certificate
active
06291548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dental cement composition. More specifically, the invention relates to a dental cement composition utilizing an acid-base reaction between a 4-methacryloxyethyl trimellitic acid aqueous solution and a powdered fluoroalumino silicate glass or a powdered metal oxide containing zinc oxide as a major component.
2. Description of the Related Art
In the dental field, when an inlay, a crown, a bridge, or the like, are to be adhered zinc phosphate cements, carboxylate cements, glass ionomer cements, or resin cements have been widely used.
Of these cements, since the dental zinc phosphate cements have no adhesive properties to a tooth structure, have a low pH value due to the presence of phosphoric acid and may cause stimulation to the tooth structure at the initiation time of setting, the frequency of their use is being decreased.
Though the dental carboxyl ate cements are a dental cement having low stimulation to the tooth structure, they have a defect that the mechanical strength is low and lack in reliability.
The dental glass ionomer cements have adhesive properties to the tooth structure and have a anti-caries function from their properties to release fluorine, thus accordingly, the dental glass ionomer cements were now widely used. In addition, since set products obtained from a dental glass ionomer cement have translucent and are superior in esthetics, they can also be applied to filling. However, as compared with the dental resin cements, the dental glass ionomer cements are low in bending strengths and have brittleness, and therefore, they have clinically a defect that when used for filling on an occlusion surface of a posterior tooth, edge portions are liable to break off.
On the other hand, the dental resin cements are superior in mechanical strengths but an exclusive dental adhesive is necessary for the adhesion to the tooth structure, due to the fact that such cement have no adhesive properties to the tooth structure. Accordingly, the dental resin cements have a defect that complicated adhesion steps are required to obtain a thorough adhesive strength.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a dental cement composition which overcomes the defects of the various dental cement compositions as described above, firmly adheres to a tooth structure without using dental adhesives requiring the surface treatment or priming, has superior adhesive durability, and is superior in mechanical strength, particularly in bending strength so that it is free from breaking off during filling on an occlusion surface of a posterior tooth.
In order to achieve the above-described problems, we, the present inventors made extensive and intensive investigations and paid an attention to the fact that 4-methacryloxyethyl trimellitic acid which has hitherto been used as a dental adhesive is a carboxylic acid group-containing acidic monomer. As a result of combining a 4-methacryloxyethyl trimellitic acid aqueous solution as a liquid material with a powder which has hitherto been used as a dental cement, it has been found that a dental cement composition which firmly adheres to a tooth structure, has superior adhesive durability and has superior mechanical strengths, particularly bending strength can be obtained, leading to accomplishment of the present invention.
That is, the dental cement composition according to the present invention comprises a liquid material and a powder material, wherein the liquid material comprises 4-methacryloxyethyl trimellitic acid and water, and the powder material comprises a powdered fluoroalumino silicate glass or a powdered metal oxide containing zinc oxide as the major component. Particularly when the liquid material is a 65% to 85% by weight aqueous solution of 4-methacryloxethyl trimellitic acid and, the liquid material and the powder material mixed in a weight ratio of from 1:0.5 to 1:4.0, remarkable superior properties can be obtained as compared with the conventional dental cement composition.
DETAILED DESCRIPTION OF THE INVENTION
4-Methacryloxyethyl trimellitic acid is a dentinal adhesive monomer which has hitherto been compounded in a dental adhesive or the like to impart adhesive properties to a tooth structure. Since this monomer is a carboxylic acid group-containing acidic monomer, it has such properties that it is rapidly set through an acid-base reaction in the presence of a powdered fluoroalumino silicate glass or a powdered metal oxide containing zinc oxide as the major component and water. For these reasons, as compared with polycarboxylic acids which have hitherto been used for dental glass ionomer cements, it can markedly improve the adhesive properties to a tooth structure so that a dental cement composition without using dental adhesives required the surface treatment or priming.
While this 4-methacryloxyethyl trimellitic acid causes an acid-base reaction with the powdered fluoroalumino silicate glass or the powdered metal oxide containing zinc oxide as a major component, since the 4-methacryloxyethyl trimellitic acid is a polymerizable monomer, it can be polymerized and set by itself. Thus, the dental cement composition according to the present invention can impart superior mechanical strengths, particularly bending strength as compared with the conventional dental cement compositions such as the dental glass ionomer cements.
In the present invention, by using the 4-methacryloxyethyl trimellitic acid in a state of an aqueous solution, its storage stability is improved. The 4-methacryloxyethyl trimellitic acid aqueous solution as the liquid material is preferably prepared in the amount of 15 to 35% by weight of water to 65 to 85% by weight of the 4-methacryloxyethyl trimellitic acid.
In the 4-methacryloxyethyl trimellitic acid aqueous solution, when the amount of the 4-methacryloxyethyl trimellitic acid is less than 65% by weight, the mechanical strengths, particularly bending strength of a set product is liable to be lowered. Further, when the amount of the 4-methacryloxyethyl trimellitic acid exceeds 85% by weight, the storage stability of the liquid material tends to be deteriorated.
The powder material to be mixed with the 4-methacryloxyethyl trimellitic acid aqueous solution as the liquid material causes an acid-base reaction in the presence of 4-methacryloxyethyl trimellitic acid and water, leading to setting. As the powder material, a powdered fluoroalumino silicate glass which is currently used as the powder component of the dental glass ionomer cement, or a powdered metal oxide containing zinc oxide as the major component, which is used as a powder component of the dental zinc phosphate cement or dental carboxylate cement, is preferable.
The powdered fluoroalumino silicate glass which is used in the dental glass ionomer cement as referred to herein is preferably a powdered fluoroalumino silicate glass containing Al
3+
, Si
4+
, F
−
, and O
2−
as the major components and additionally containing Sr
2+
and/or Ca
2+
. Further, the proportions of Al
3+
, Si
4+
, F
−
, and the sum of Sr
2+
. Further, the preferably from 10 to 21% by weight, from 9 to 24% by weight, from 1 to 20% by weight, and from 10 to 34% by weight, respectively based on the total weight of the glass.
These proportions of the major components greatly influence the handling property and physical properties such as setting rate, final strength, and solubility. When the proportion of Al
3+
is less than 10% by weight, the setting rate is slow, and the strength tends to be lowered. When the proportion of Al
3+
exceeds 21% by weight, the preparation of the glass is difficult, and the transparency is lowered, whereby the esthetics are liable to be inferior. When the proportion of Si
4+
is less than 9% by weight, the preparation of the glass is liable to be difficult, too. When the proportion of Si
4+
exceeds 24% by weight, the setting rate is liable to be slow, and the strength is low,
Akahane Shoji
Nakaseko Hisashi
GC Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Szekely Peter
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