Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-07-23
2004-07-06
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...
C523S116000, C523S223000, C433S228100
Reexamination Certificate
active
06759449
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a dental adhesive composition, as well as a dental adhesive kit consisting of a combination of the dental adhesive composition and a dental primer composition.
DESCRIPTION OF THE PRIOR ART
In the field of dental treatment, a damaged tooth due to caries or an accident must be firmly cemented with a restorative material for the tooth including a crown restorative material made by composite resins, metals and ceramics, and a variety of adhesive compositions have been suggested for such cementing.
Among these adhesive compositions, adhesive resin cements have been widely used because they can firmly cement a metal or ceramic prosthesis with a tooth. An adhesive resin cement essentially consists of a monomer component, a filler component and a polymerization initiator. It is believed that an adhesive resin cement containing a non-crosslinking resin filler (non-crosslinking polymer filler) as a filler component gives a cured resin cement exhibiting higher toughness than an adhesive resin cement comprising a crosslinking resin filler or inorganic filler and is adequately resistant to external stress applied to a prosthesis cemented with a tooth to prevent the prosthesis from being easily detached from the tooth. Known adhesive resin cements comprising a non-crosslinking resin filler (hereinafter, referred to as a resin-filler resin cement) include resin cements comprising tributylboran or its partially oxidized (TBBO) as a polymerization initiator and a non-crosslinking polymethyl methacrylate filler as a non-crosslinking polymer filler.
Although such a resin-filler adhesive resin cement advantageously exhibits higher adhesiveness, it has been indicated that it has the following problems in terms of operability in use. Specifically, the above polymerization initiator used in the resin cement is chemically unstable, so that it must be packed separately from the other components. Furthermore, the non-crosslinking polymer filler and the monomer must be also separately packed for preventing the non-crosslinking polymer filler from being dissolved. Thus, in the resin cement, the polymer filler, the monomer liquid and the polymerization initiator solution must be packed separately from each other, i.e., a three-packet system. When using the resin cement, given amounts of the monomer liquid and the polymerization initiator solution are mixed, and then a given amount of the polymer filler is added. This process is troublesome.
When using the resin cement, the three components can be mixed to rapidly increase a viscosity and thus to reduce a time for applying the mixture to a tooth surface and a crown restorative material (hereinafter, referred to as a “working time” or “operable time”). Higher technique which ensures rapid and firm cementing is, therefore required for achieving desired adhesive strength using the resin cement. When using the polymerization initiator, it takes a longer time until the resin cement is adequately cured to exhibit desired adhesiveness. There is thus a problem that a desired adhesive strength cannot be achieved if a strong force is applied after cementing a prosthesis on the tooth surface and before completion of curing of the resin cement.
There have been no known resin-filler resin cements which can sufficiently endure severe environmental conditions, i.e., in the mouth, to provide good adhesiveness; have a satisfactory working time and an appropriate curing time; and exhibit improved operability.
SUMMARY OF THE INVENTION
An objective of this invention is to provide a resin-filler resin cement meeting the above requirements.
The above problem in terms of packaging depends on stability of a polymerization initiator used. A curing time basically depends on a combination of a polymerization initiator and a monomer. These problems could be, therefore, solved by employing a stable polymerization initiator and a polymerization initiator-monomer system which can be quickly cured and exhibits higher adhesive ability. Actually, many such initiator-monomer systems have been found for a dental adhesive composition other than a resin-filler resin cement and have been practically used. The above two problems could be, therefore, solved by employing such a well-known monomer-initiator system.
However, a resin-filler resin cement contains a non-crosslinking polymer filler as a constituent. Thus, it is inevitable that on mixing a polymer filler with a monomer in use, expansion or dissolution of the polymer filler leads to increase in a viscosity of the mixture. It can be thus said that the above problem in terms of a working time is inherent to a resin-filler resin cement. Furthermore, a working time may vary significantly depending on a combination of a non-crosslinking polymer filler and a monomer. A working time might be increased by replacing one or both of these components. However, since replacing a monomer may substantially affect, e. g., an adhesive strength, it cannot be easily applied.
We thus considered the problem of a working time as a common problem for a dental adhesive composition comprising a non-crosslinking polymer filler and a monomer rather than that for a resin-filler resin cement alone. We have, therefore, attempted to solve the problem of a working time by first selecting an initiator-monomer system employed in a dental adhesive composition other than the above resin-filler resin cement and next developing a non-crosslinking polymer filler providing a suitable working time when being mixed with the initiator-monomer system.
It is well-known that a working time depends on a shape and a particle size of a non-crosslinking polymer filler. Specifically, a working time tends to be reduced by using an irregular form non-crosslinking polymethyl methacrylate filler as a component of a resin cement while it tends to be increased by using a spherical polymethyl methacrylate filler (Shika Zairyo-Kikai, Vol. 18, No.5, 347-351, 1999). It is also known that by controlling a particle size or particle size and surface roughness of an irregular form non-crosslinking polymethyl methacrylate filler can increase a working time to some extent (Shika Zairyo-Kikai, Vol. 19, No.1, 92-101, 2000 and JP-A 2000-53727). When using such a filler to adjust a working time, a curing time of a resin cement may be increased or an elongation of working time may not be sufficient. The above problem cannot be solved only by optimizing a shape or particle size of a filler.
Under such a situation, we have investigated not only a shape and a particle size of a non-crosslinking polymer filler but also its material quality. We have consequently found that a resin cement can be formulated using a mixture of a non-crosslinking polymethyl methacrylate spherical filler and a non-crosslinking polyethyl methacrylate spherical filler to increase a working time of the resin cement without adversely affecting a curing time or adhesive strength, achieving this invention.
This invention provides a dental adhesive composition comprising (A) a polymerizable monomer comprising an acidic-group containing polymerizable monomer; (B) a spherical filler substantially consisting of a non-crosslinking polymethyl methacrylate and a spherical filler substantially consisting of a non-crosslinking polyethyl methacrylate; and (C) a polymerization initiator.
Because a dental adhesive composition of this invention comprises a non-crosslinking polymer filler as a filler component, it can provide a cured product exhibiting higher toughness than that from a dental adhesive composition comprising a crosslinking filler or inorganic filler. Thus, it can adequately endure a stress applied to a prosthesis while maintaining the property in a conventional resin-filler resin cement that a cemented prosthesis is resistant to detachment. It can provide a higher adhesive strength, gives a shorter time to a proper viscosity, and gives an appropriately long working time of 40 to 150 sec, resulting in good operability. Furthermore, a curing time is as short as 5 min or less, the dental adhes
Kazama Hideki
Kimura Mikio
Matsushige Koji
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Szekely Peter
Tokuyama Dental Corporation
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