Compositions: coating or plastic – Coating or plastic compositions – Dental
Reexamination Certificate
1999-02-04
2001-04-10
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Dental
C523S116000, C433S228100
Reexamination Certificate
active
06214101
ABSTRACT:
FILED OF THE INVENTION
The present invention relates to a dental glass ionomer cement. More particularly, it relates to a paste-type dental glass ionomer cement composition comprising a first paste and a second paste, the both being cured upon mixing with each other.
BACKGROUND OF THE INVENTION
Many types of dental cements have become available and used in a wide range of applications. Representative examples of dental cements which are mainly used at present include zinc phosphate cements which utilize a reaction between zinc oxide and phosphoric acid; polycarboxylate cements which utilize a reaction between zinc oxide and a polycarboxylic acid; zinc oxide-eugenol cements which utilize a reaction between zinc oxide and eugenol; glass ionomer cements which utilize a reaction between a fluoroaluminosilicate glass powder and a polycarboxylic acid; and resin cements which utilize a polymerization of an acrylic monomer.
Each of these dental cements has merits and demerits. For instance, the zinc phosphate cements have no adhesive properties to a tooth structure and possess irritation of phosphoric acid at the initial stage of the curing; the polycarboxylate cements are low in the final strength of a cured product; and since the zinc oxide-eugenol cements are low in the strength and inferior in the intraoral durability, their use is limited to the temporary sealing, and the eugenol per se possess irritation. Also, though the resin cements have merits such as superior adhesive properties and high mechanical strength unlike other dental cements, they involve such defects that their operation is complicated and that their bioaffinity is questionable.
On the other hand, the glass ionomer cements are quite good in the affinity to living bodies and have good dentinal adhesive properties. Moreover, they are expected to have a caries preventing effect by the fluorine contained in the glass. While utilizing these many characteristic features, the glass ionomer cements are used in a wide range of applications such as filling and restoration of caries cavity; cementing of, for example, a crown, an inlay, a bridge, or an orthodontic band; lining of cavity; core construction; and pit and fissure sealing.
In addition, there are presently developed resin-reinforced glass ionomer cements in which the brittleness of a matrix by water at the time of the initial curing, which has hitherto been considered to be a disadvantage, is prevented, and the physical properties such as mechanical strengths, e.g., bending strength, and adhesive strength to a tooth structure are improved, and which have superior adhesive properties to dental metals, resins, porcelains, etc., upon addition of a polymerizable resin component to the liquid component of the glass ionomer cement.
As described above, the glass ionomer cements have various characteristic features. However, the conventional dental glass ionomer cements are constructed from a powder component and a liquid component and involve a drawback such that the operations such as weigh and mixing are complicated. The operation of mixing of a powder component with a liquid component is usually carried out on an exclusive mixing paper by using a spatula. However, at this time, since the powder component and the liquid component are not compatible with each other, the collected powder component is divided into two parts or four parts, which are then successively mixing with the liquid component. That is, the mixing operation is required such that the powder component and the liquid component are mixed with each other uniformly as far as possible. In addition, the mixing operation must be carried out within a short period of time, and in order to fully exhibit the characteristics of the materials to be used, a remarkably skilled technique is needed.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the defects of the conventional glass ionomer cements as described above and to provide a paste-type dental glass ionomer cement composition in which mixing is possible by a easy operation, through a construction such that a dental glass ionomer cement composition comprising a powder component and a liquid component is made pasty, whereby both of a first paste and a second paste are mixed with each other to achieve curing of the composition.
In order to achieve the above-described object, I, the present inventor, made extensive and intensive investigations. As a result, I have completed a paste-type dental glass ionomer cement composition which does not require a technical skill for mixing operation, through a paste-type dental glass ionomer cement composition having a construction comprising a first paste prepared by combining an &agr;-&bgr; unsaturated carboxylic acid polymer, water and a filler not reactive with the &agr;-&bgr; unsaturated carboxylic acid polymer; and a second paste prepared by combining a fluoroaluminosilicate glass powder and a polymerizable monomer free of an acid group, wherein at least one of the first paste and the second paste contains a polymerization catalyst.
DETAILED DESCRIPTION OF THE INVENTION
That is, the paste-type dental glass ionomer cement composition according to the present invention is characterized in that:
the first paste comprises (a) an &agr;-&bgr; unsaturated carboxylic acid polymer, (b) water, and (c) a filler not reactive with the above-described &agr;-&bgr; unsaturated carboxylic acid polymer; and
the second paste comprises (d) a fluoroaluminosilicate glass powder and (e) a polymerizable monomer free of an acid group; and
at least one said first paste and said second paste contains (f) a polymerization catalyst.
In this case, from the point of view of the mixing operation of the paste-type dental glass ionomer cement composition, it is preferred that the first paste comprises from 20 to 60% by weight of an &agr;-&bgr; unsaturated carboxylic acid polymer, from 20 to 60% by weight of water, and from 10 to 60% by weight of a filler not reactive with the above-described &agr;-&bgr; unsaturated carboxylic acid polymer; and the second paste comprises from 50 to 85% by weight of a fluoroaluminosilicate glass powder and from 15 to 50% by weight of a polymerizable monomer free of an acid group and that at least one of the first paste and the second paste contains a polymerization catalyst in an amount in total of from 0.05 to 10% by weight based on a total amount of the paste-type dental glass ionomer cement composition in mixing for using the first paste and the second paste.
The &agr;-&bgr; unsaturated carboxylic acid polymer as the component (a) to constitute the first paste is a homopolymer or copolymer of at least one member selected from acrylic acid, methacrylic acid, 2-chloroacrylic acid, 3-chloroacrylic acid, aconitic acid, mesaconic acid, maleic acid, itaconic acid, fumaric acid, glutaconic acid, and citraconic acid and is preferably a polymer not containing a polymerizable ethylenically unsaturated double bond and having a weight average molecular weight of from 5,000 to 40,000. In these &agr;-&bgr; unsaturated carboxylic acid polymers, in case that a polymer having a weight average molecular weight of less than 5,000, not only the strength of a cured product tends to become low, but also the adhesive strength to a tooth structure is liable to be lowered. In case that a polymer having a weight average molecular weight exceeding 40,000 is used, the consistency at the time of mixing is too high, whereby the mixing tends to become difficult. A proportion of the &agr;-&bgr; unsaturated carboxylic acid polymer in the first paste is preferably from 20 to 60% by weight. If the proportion is less than 20% by weight, the adhesive strength to a tooth structure which are a characteristic as the dental glass ionomer cement are liable to be lowered, whereas if it exceeds 60% by weight, the solubility of a cured product tends to increases so that the durability is liable to be inferior.
The water as the component (b) to constitute the first paste is an indispensable component in the present invention. This is bec
GC Corporation
Koslow C. Melissa
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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