Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-11-28
2004-06-15
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, C523S118000, C522S908000, C433S228100
Reexamination Certificate
active
06750268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a self-etching and self-priming bonding composition for tooth restoration that keeps the restorative dental material bonded to the defective tooth for a long period of time.
2. Description of the Related Art
In the last half of the 20th century, the technology of bonding an acrylic resin to teeth had a great influence on the development of dental treatment. The first technique referred to is a technique developed by M. Buonocore in 1956. It comprises etching and roughening of the enamel of a tooth with an aqueous solution of phosphoric acid, resulting in a significant increase in the area of the bonding interface and an increase of the bonding strength between the tooth and the resin.
Later, various types of functional monomers capable of forming chemical bonds with the components of teeth have been developed. With those, the technique of bonding resins to the dentin of teeth has made remarkable progress in dental treatment. The proposed functional monomers include, for example, polymerizable monomers having an acid group, such as a phosphoric acid group or a carboxylic acid group, having high reactivity with the calcium hydroxyapatite (HAP) of teeth. Furthermore, other monomers capable of forming covalent bonds to the collagen of teeth have been proposed.
In Japanese Patent Laid-Open No. 45510/1985 the present applicant proposed a remarkable technique, wherein water is added to a dental bonding composition that contains a polymerizable monomer having a phosphoric acid residue. The dental bonding composition further comprises a specific terpolymerization initiator selected from diacyl peroxides, amine compounds, arylsulfinic acid salts, water, and optionally any other copolymerizable monomer. Conventionally it is assumed that the influence of water on the restored area of teeth is to be minimized to ensure good adhesion of a restorative material to teeth that are in constant contact with saliva. However, the disclosed invention is based on the finding that the bonding strength of the dental composition can be enhanced by adding water. The inventors disclose in the specification of 45510/1985 that the dental bonding composition exhibits high bonding strength even to the teeth not previously etched with an acid. The bonding strength may be further enhanced if the teeth are etched with an acid before the composition is applied. However, a self -etching or self -priming dental bonding composition is not disclosed.
After that, it was found that primers, if applied to teeth before the bonding composition, could enhance the bonding strength of the compositions to a great extent. Various proposals have been made for primers. Most of them ensured a complete wetting of the teeth by the bonding compositions. For example, Japanese Patent Laid-Open No. 223289/1987 discloses a primer for hard tissue which comprises an acid, a water-soluble film-forming agent, and optionally water. A specific acid is used in the invention. Its salt with calcium must be soluble in the water-soluble film-forming agent for the primer to provide high bonding strength. The specification discloses that the initial bonding strength of the bonding composition to the dentin of the tooth is increased if a primer is first applied to a tooth followed by the application of a bonding composition. However, when the bonded tooth sample is kept in water for a long period of time, the bonding strength of the bonding composition decreases, and the bonding durability is not satisfactory. Thus, the proposed primer has a drawback.
Japanese Patent Laid-Open No. 240712/1991 discloses a primer composition that comprises water, a polymerizable compound having a hydroxyl-group, a polymerizable compound having an acid group, and a curing agent. The object of the proposed primer is to provide high bonding strength and bonding durability. However, the polymerizable compound having an acid group is not specifically defined, and includes the polymerizable compounds that are exemplified as acids in the specification of above-mentioned 223289/1987.
The two techniques disclose a primer treatment of teeth instead of the ordinary etching with phosphoric acid to provide high bonding strength. However, bonding treatment with a liner or a similar bonding composition after the primer treatment is required when adhesive resin cement is used. Accordingly, the proposed techniques are still problematic because the use of primers does not shorten the process of dental treatment and does not fully meet the requirements of users and dentists.
The inventor has studied the mechanism of the bonding behavior and the bonding durability of the bonding compositions of above prior art. He found that the dentin of teeth is a complicated bio-tissue that comprises collagen fibers and HAP crystals. When an acidic primer having an acid ingredient is applied to dentin, it will partially dissolve the HAP crystals in the dentin. At the same time, the water-soluble monomer ingredient of the primer will penetrate into the collagen fibers remaining in the dentin after the HAP crystals were dissolved. As a result, the modified dentin surface is compatible with a bonding agent. The primer is then cured. The collagen fibers of the dentin will be entangled with the resin formed by polymerization of monomers and water-soluble film-forming agent. The bonding composition is applied to the tooth after the primer. As a result, the bonding composition has good bonding strength to the tooth.
The boundary area between the dentin of the tooth and the resin layer formed from the primer was analyzed. A calcium salt exists around the surface of the HAP crystals in the boundary area. The calcium salt was formed by reaction of above acid with HAP. In addition, resin portions containing the collagen fibers are left as they are after the partial dissolution of HAP. If the calcium salt of the acid is soluble in water it will gradually dissolve when the bonded sample is kept in water for a long period of time. Accordingly, the packing density of the bonding resin around the bonding interface will be lowered. As a result, the strength and durability of the bonding layer will also be lowered.
The present inventor has found the particular advantage of the prior art primers capable of exhibiting high bonding strength even when they are directly applied to teeth that are not previously subjected to acid etching (probably due to the self-etching effect of the primers). The present inventor further recognized the disadvantage of low bonding durability due to the solubility of the calcium salt of the acid in the bonding interface layer in water.
The present invention overcomes the drawback of the prior art primers on the basis of the fundamental knowledge relating to the composition of ordinary bonding compositions for dental use.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a self-etching and self-priming bonding composition which ensures good initial bonding strength to teeth and long-lasting durability. The self-etching and self-priming bonding composition is useful in dental treatment and provides good bonding to tooth tissue and does not require any pre-treatment, such as acid etching and priming.
Another object of the invention is to provide a liquid bonding composition with rapid curability.
Still another object of the invention is to provide a bonding composition having the an increased bonding strength, whereby the thickness of the bonding layer can be controlled in any desired manner.
The objects of the invention are attained by providing a bonding composition which comprises:
a mixture of a polymerizable compound having acid group, a water-soluble film-forming agent, water, and a curing agent;
wherein a calcium salt formed from said polymerizable compound having an acid group is insoluble in water;
wherein said film-forming agent is a polymerizable compound; and
wherein said film-forming agent is miscible with a physiological saline solution.
DETAILED DESCRIPTION OF THE INVENT
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Szekely Peter
LandOfFree
Bonding composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bonding composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bonding composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344345