Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-16
2002-08-20
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S030000, C524S551000, C524S555000, C524S558000, C524S815000, C524S816000, C524S829000, C524S831000, C524S833000, C524S818000, C524S494000
Reexamination Certificate
active
06437019
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to glass ionomer cement systems. More specifically, this invention relates to glass ionomer cement systems comprising an aqueous composition and an acidic organic composition.
BACKGROUND OF THE INVENTION
Glass ionomer cements in general are materials that comprise an ionic polymer composition and a reactive glass composition, where mixing these two compositions in an aqueous environment initiates a cement setting reaction. These materials are used in a number of applications in the dental and medical industries where a cement is used on, for example, tooth or bone structure. Conventionally, these materials are provided in two part systems, wherein one of the parts is in a powder form. Typically, the ionic polymer is provided in an aqueous liquid form and the reactive glass is provided as a powder. Considerable effort has been expended in designing systems to mix a powder and a liquid quickly and easily to enable complete reaction of conventional glass ionomer systems.
U.S. Pat. No. 4,288,355 to Anderson discloses surgical cement compositions comprising a concentrated non-gelling aqueous solution of a polycarboxylic acid and an aqueous suspension of metal oxide powder which when mixed together form a plastic mass which is formable into the desired shape before it hardens. These cements are formulated using a paste:paste format, but in all cases both pastes are aqueous pastes. This reference fails to disclose use of an organic paste for delivery of the reactive filler.
U.S. Pat. No. 4,591,384 to Akahane discloses dental cement compositions comprising a metal oxide and second ingredient capable of reacting with the metal oxide. The composition further comprises a tannic acid derivative that is sparingly soluble in water and a reducing agent that is soluble in water. Various forms of combining these two reactive ingredient are disclosed at column 2, lines 18-27. Included in this recitation is “powder/liquid, powder/paste, paste/paste, paste/liquid and the like,” apparently indicating that all forms of delivery are equivalent for the cement system disclosed therein.
U.S. Pat. No. 5,063,257 to Akahane discloses dental glass ionomer cement compositions comprising (a) a polymer of an alpha-beta unsaturated carboxylic acid, (b) a fluoroaluminosilicate glass powder, (c) a polymerizable unsaturated organic compound, (d) a polymerization catalyst, (e) water, (f) a surfactant and (g) a reducing agent. Paste:paste compositions are exemplified having the ionomer in an aqueous paste and the reactive filler in an organic paste.
U.S. Pat. No. 5,154,762 to Mitra et. al discloses a Univeral Water-Based Medical and Dental Cement, wherein the cement contains water, acid-reactive filler, water-miscible acidic polymer, an ethylenically-unsaturated moiety, photoinitiator, water-soluble reducing agent and water-soluble oxidizing agent. Two-part paste:paste formulations are broadly disclosed at column 2, lines 58-66.
SUMMARY OF THE INVENTION
The present invention provides a multiple part ionomeric cement system comprising an organic composition that is substantially free of added water, and an aqueous composition comprising water. The organic composition contains at least a hydrophilic component and an acid functional compound that is provided as greater than 1.0% weight of the organic composition. The liquid ingredients of the organic composition form a miscible solution, and the liquid ingredients of the aqueous composition also form a miscible solution. The liquid ingredients of the organic composition and the aqueous composition when mixed together also form a miscible solution. At least one of the organic composition and the aqueous composition comprises an acid reactive filler, provided that the aqueous composition does not contain both an acid reactive filler and an acid. At least one of the organic composition and the aqueous composition comprises a polymerizable component. Al least one of the organic composition and the aqueous composition comprises a polymerization catalyst to initiate polymerization of said polymerizable component. Finally, the organic composition and the aqueous composition are substantially free of surfactant.
DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS
The present invention provides an easy to use glass ionomer cement system that has excellent strength characteristics as well as good wetting properties on a wet field in the oral environment. The system is surprisingly highly stable, because the acid component and the acid reactive filler component may be incorporated together in the organic composition without deleterious effects.
Because there is no surfactant in the composition and the liquid ingredients of each composition are miscible both before and after the parts are mixed, the instant compositions provide an excellent matrix when polymerized. Since the liquid ingredients form a single phase, the curative agents are uniformly dispersed throughout the matrix with no unpolymerized regions. The resulting compositions have excellent strength characteristics. Additionally, the compositions of the present invention exhibit excellent fluoride release.
Because the organic composition of the present invention is substantially free of added water, reactive filler may optionally be provided in both the organic and the aqueous compositions of the ionomeric cement. Higher reactive filler loading allows a better ionomeric matrix to be established upon curing, and a higher fluoride release may be achieved as well.
The liquid components of the aqueous and organic compositions of the present system are determined to be miscible by evaluation of the stability of the liquid components over time. The liquid components are placed mixed together in the desired ratio, and placed in a 25 mls vial such that the vial is about half full. The vial is then agitated by rotation around the short axis at about 25 revolutions per minute for three days. The vial is then allowed to stand for four weeks at ambient temperature and the presence of sediment is determined by visual inspection. If no sediment is observed, the composition is determined to be miscible and stable.
For purposes of the present invention, the term “substantially free of added water” means that the composition does not contain water that is intentionally added as a non-complexed or coordinated entity. It is understood that many materials, such as metals or glasses, contain water that is taken up from the atmosphere or is present as a coordination complex in its normal state. Water taken up by hygroscopic materials or present as a hydrate is permissibly present in the compositions described herein. Any water that is present in the composition, regardless of source, should not be present in amounts such that the water will have a deleterious effect on the long term properties of the composition. For example, water should not be present in an amount that would facilitate reaction of the fluoride-releasing material with the acidic component so that lumpiness or graininess of the material develops during commercially required storage times.
The compositions of the present invention are both liquid in nature, either as a readily flowable liquid or as a paste. Preferred ionomeric systems have both compositions provided as a paste. For purposes of the present invention, a paste is defined as a material wherein the inelastic modulus is less than the elastic modulus of the material. An organic paste is a paste wherein the liquid components are organic in nature, and wherein said organic paste is substantially free of added water. Preferably, the aqueous paste and the organic paste each have a viscosity between about 1×10
2
and 1×10
11
Cps. More preferably, the aqueous paste and the organic paste each have a viscosity between about 1×10
7
and 1×10
9
Cps. Viscosity is measured using a rheometer at a shear rate between 0.01 and 0.1 sec
−1
at about 25° C. A preferred test protocol is to utilize a Bohlin CS50 controlled stress rheometer (Metric Group,
Oxman Joel D.
Rusin Richard P.
Winters Edward J.
3M Innovative Properties Company
Reddick Judy M.
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