Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From heterocyclic reactant containing as ring atoms oxygen,...
Reexamination Certificate
1997-11-12
2001-02-06
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From heterocyclic reactant containing as ring atoms oxygen,...
C522S090000, C522S155000, C522S156000, C522S100000, C522S908000, C523S109000, C523S116000, C523S118000, C523S115000, C523S300000, C423S226000, C528S406000, C528S418000, C528S059000, C528S065000, C528S087000
Reexamination Certificate
active
06184339
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to high strength polymeric networks derived from (meth)acrylate resins with moderate to high organofluorine contents and processes for making same. In particular, these resins are useful for dental composites.
BACKGROUND OF THE INVENTION
In dentistry, fluoropolymers have been widely utilized as components of medical devices because of the advantageous blend of chemical inertness with generally good biocompatibility. As the demand for advanced fluoropolymers with specific physical properties has grown, the molecular design of new types of fluorinated monomers has become an important area in synthetic polymer chemistry. Several properties of fluoropolymers, including their chemical inertness, hydrophobicity and toughness, make fluoropolymers interesting candidates for use in dental composites. However, due to low cohesive energies, amorphous fluorinated polymers tend to have unacceptably low mechanical strength.
In the area of aesthetic dental composite materials used for restorative and cosmetic purposes, the critical advancement in polymer technology was the introduction of 2,2-bis[p-(2′-hydroxy-3′-methacrylpropoxy)phenyl]propane, commonly referred to as Bis-GMA. This bulky dimethacrylate monomer is used with a low viscosity diluent comonomer, typically triethylene glycol dimethacrylate (TEGDMA), to prepare resins that form strong, densely cross-linked polymeric networks. More than 30 years after their introduction, resins based on varying proportions of Bis-GMA/TEGDMA still constitute the majority of commercial dental composite filling materials. Among other methacrylates utilized in commercial composite restoratives are urethane-containing monomers, such as urethane dimethacrylate (UDMA), and oligomers, such as the linear poly(urethane) prepared from Bis-GMA and hexamethylene diisocyanate (Bis-GMA-HMDI). Additional components of dental composites include a particulate filler, generally a barium, strontium or zirconium-containing glass and/or a microfine silica, whose surface is modified by attachment of a layer of a methacrylate-functionalized silane coupling agent, 3-methacryloxypropyltrimethoxysilane. A visible light activated photoinitiator system, camphorquinone (CQ) and an amine photoreductant, such as ethyl 4-N,N-dimethylaminobenzoate (EDMAB), allows the onset of polymerization to be controlled and then the rapid development of the cross-linked resin matrix to yield the cured composite under ambient conditions.
The relatively high modulus fillers used in dental composites serve to increase the strength, wear resistance and toughness of the resin matrix by reinforcement. The silane coupling agent plays a critical role in the development and maintenance of the reinforcing effect of the filler. Addition of substantial amounts of filler also minimizes the overall polymerization shrinkage associated with the continuous matrix phase. The particulate filler is also responsible for the translucence of the cured composite that gives it the natural tooth-like appearance. Coloration incorporated during the preparation of the filler can reproduce a broad spectrum of natural tooth shades and this allows near perfect matching of the composite to the adjacent tooth structure. The small particle size of the fillers used in the dental composites means that the composites can be polished to produce an excellent texture match with natural tooth.
Typical conventional resins based on Bis-GMA and TEGDMA ranging from mass ratios of 50:50 to 80:20, depending on the particular dental application, provide strong polymers. The cross-linked polymers are glasses whose degree of conversion of the available methacrylate groups is restricted by vitrification as the glass transition temperature of the developing polymer reaches the cure temperature. The degree of conversion attained during ambient temperature photopolymerzation is generally in the range 60% to 70%. The conversion varies somewhat with the intensity of the curing light; a more intense irradiation results in a faster polymerization with a greater exotherm. The fully cured resin is characterized as a highly cross-linked three dimensional polymeric network with many pendant methacrylate-terminated chains that lack sufficient mobility for further reaction.
Polymers designed to permanently replace tissues in the human body lost to disease, trauma or simple deterioration must satisfy a number of criteria. Beyond the obvious requirement of biocompatibility, long-tem stability dictates the need for materials that are highly resistant to alteration or degradation upon exposure to aqueous environments and resistant to a variety of chemical substances. In materials under consideration for dental composite restorative applications, the need for inert polymer matrices is coupled with the need for polymers that have adequate mechanical properties to minimize wear and fracture in both load-bearing and non-loadbearing situations. With an essentially limitless range of potential monomeric components available, advanced polymeric materials can be tailored to meet specific challenges such as these. Because of the excellent resistance displayed by fluoropolymers used in aqueous or other aggressive chemical environments, a variety of partially fluorinated monomers have been investigated previously as a means to achieve hydrophobic, chemically stable dental polymers. However, the use of significant proportions of fluorinated mono- or di-methacrylate monomers in dental resins typically produces polymers with unacceptably low mechanical strength properties primarily due to the low cohesive energies of amorphous fluorinated polymers.
Fluorinated resins for use in dental materials and a variety of other uses are disclosed by U.S. Pat. No. 4,616,073 (Antonucci); U.S. Pat. No. 4,914,171 (Zweig); and U.S. Pat. No. 5,380,901 (Antonucci et al.) all of which are incorporated herein by reference in their entirety. Fluorinated resins for use in dental materials and a variety of other uses are also disclosed by publications such as Douglas et al.,
J. Dent. Res.
58, 1981 (1979); Kurata et al.,
J. Dent. Res.
68, 481 (1989); Maruno et al.,
J. Polym. Sci. Part A: Polym. Chem.
32, 3211 (1994); Cassidy et al.,
Eur. Polym. J.
31, 353 (1995); and Stansbury et al.,
Amer. Chem. Soc., Polym. Prepr.
36(1), 831 (1995) all of which are incorporated herein by reference in their entirety.
Fluorinated polymers with moderate fluorine contents are generally hydrophobic but lack good mechanical strength properties due to the low cohesive energies associated with fluorine-substituted amorphous polymers. A photocurable dimethacrylate monomer 2,2-bis(p-(2′-hydroxy-3′-methacryloxy-propoxy)phenylene) propane (Bis-GMA) has been synthesized from the diglycidyl ether of bisphenol A and methacrylic acid. This reaction is shown by Reaction I.
Bis-GMA has been used extensively as the basis of dental composite filling materials as disclosed by Bowen, R. L., U.S. Pat. No. 3,066,112; Bowen, R. L., U.S. Pat. No. 3,194,783; Venhoven, B. A. M., DeGee, A. J., Davidson, C. L.,
Biomaterials
1993, 14(11), 871; Stansbury, J. W., Antonucci, J. M.,
Dent. Mater.
1992, 8, 270; Venz, S.; Dickens, B.,
J. Biomed. Mater. Res.
1991,25,1231; Antonucci, J. M., Scott, G. L.,
Polym. Prepr.,
1995, 36 (1), 831; and Dulik, D., Bernier, R., Brauer, G. M.,
J. Dent. Res.,
1981, 60 (6), 983. The photopolymerization of an unfilled resin based on Bis-GMA diluted with triethylene glycol dimethylacrylate (TEGDMA) (7:3 by mass) produced a volumetric shrinkage of 7.9%. The resulting crosslinked polymer has a diametral tensile strength (DTS) and transverse strength (TS) of 42.2±3.6 MPa and 75.3±4.3 MPa, respectively and a water uptake of 3.8% as disclosed by Venhoven, B. A. M., DeGee, A. J., Davidson, C. L.,
Biomaterials
1993, 14(11), 871; Stansbury, J. W., Antonucci, J. M.,
Dent. Mater.
1992, 8, 270; and Venz, S., Dickens, B.
J. Biomed. Mater. Res.
1991, 25, 1231.
However, new fluorocompounds are needed to impr
Antonucci Joseph M.
Choi Kyung M.
Stansbury Jeffrey W.
McClendon Sanza L.
Seidleck James J.
Stevens Davis Miller & Mosher LLP
The United States of America as represented by the Secretary of
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