CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Pursuant to 37 C.F.R. § 1.78(a)(4), this application claims the benefit of and priority to prior filed co-pending Provisional Application Serial No. 61/186,063, filed June 11, 2009, which is expressly incorporated herein by reference.

FIELD OF INVENTION

[0002] The present invention relates to adhesive and/or sealant compositions that cure by cationic polymerization and free -radical polymerization, and particularly to self-adhering dental compositions suitable for use as a root canal sealer.

BACKGROUND OF INVENTION

[0003] Methacrylate resin-based compositions have been used in dentistry for decades. However, dental materials based on (meth)acrylate resins, which are chemically cured, usually have wet surfaces due to the inhibition of the free-radical polymerization reaction at the surface by molecular oxygen. The oxygen inhibition is even more apparent as the rate of polymerization of the material decreases. This presents a potential problem with the restoration of a tooth. For example, when the oxygen inhibition effect takes place in an interface, such as at the tooth surface of a root canal, unsatisfactory sealing may result. [0004] Alternatively, compositions cured by epoxy ring-opening polymerization have been used to seal root canals. For example, products, such as AH 26® Silver Free and AH PLUS JET® by Dentsply, are commercially- available, two-part epoxy- amine compositions. While compositions cured by epoxy ring-opening polymerization are not susceptible to the oxygen inhibition effect, as described above, two drawbacks to these conventional epoxy and amine two-component systems are slower reaction times at room temperature, and lack of adhesion to a tooth surface. Additionally, the slow curing time inhibits the material from possessing instant mechanical properties because the setting time of the material can take hours, if not days. [0005] Compositions cured by epoxy ring-opening polymerization may also be initiated through a cationic polymerization of the epoxy resin using a starter, such as a Lewis acid or a strong Brønsted acid. For example, Lewis acids, such as BF ₃ »Et ₂ 0, BF ₃ »THF, AlCl ₃ , FeCl ₃ and the like, where Et ₂ O is diethyl ether and THF is tetrahydrofuran, may initiate the cationic ring- opening polymerization under ambient conditions. Similarly, strong Brønsted acids, such as HBF ₄ , HB(C ₆ Fs) ₄ , HPF ₆ , HAsF ₆ or HSbF ₆ may initiate the cationic ring-opening polymerization immediately after mixing with the epoxy.

[0006] Another type of initiator for the cationic ring-opening polymerization is a latent starter, which upon contact with the epoxy does not itself initiate the polymerization, but starts the polymerization upon contact with an agent that transforms the starter into a form that is able to initiate the polymerization. For example, halonium salts of the general formula HaI-(Ar) ₂ ⁺ An ^" , wherein Hal is a halogen, Ar is an aryl group, and An is an anion, when transformed can liberate H ⁺ as extremely strong acid H ⁺ An ^" . An exemplary latent starter is diaryliodonium compounds, such as diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate and the like. Generally, Cu(I) salts and a reducing agent, such as ascorbic acid, are used to transform the halonium salt.

[0007] Additionally, the use of light-initiated cationic ring-opening polymerization of epoxy resins in dentistry has grown in recent years, largely due to the lower shrinkage of the resulting composite as compared to the free radical polymerization of (meth)acrylates. But these epoxy compositions cured by the methods described above can still present poor adhesion to a tooth surface.

[0008] Therefore, what is needed is a composition that possesses favorable curing properties and improved adhesion.

SUMMARY OF THE INVENTION

[0009] In one embodiment of the invention, a polymerizable composition is provided comprising a first part comprising an epoxy compound; and a second part comprising a polymerizable, ethylenically-unsaturated resin having an acid functional group, wherein the first part and/or the second part further comprises a radical initiator. [0010] In another embodiment of the invention, a method of providing a polymerized composition is provided which comprises mixing a first part comprising an epoxy compound with a second part comprising a polymerizable, ethylenically-unsaturated resin having an acid functional group, wherein the mixing initiates a cationic polymerization reaction of the epoxy compound facilitated by the acid functional group; and polymerizing the polymerizable, ethylenically-unsaturated resin, wherein the polymerizing is a free-radical polymerization initiated by a self-cure free-radical initiator and/or an photo-initiated free radical initiator. [0011] In another embodiment of the invention, a method of curing a two-part composition, which has a first part comprising an epoxy compound, and a second part comprising a polymerizable, ethylenically-unsaturated resin having an acid functional group, wherein the first and/or second part further comprises a self-cure free-radical initiator and/or a photo- initiated free-radical initiator, is provided wherein the method comprises effecting a first polymerization of the epoxy compound initiated by the acid functional group selected from the group consisting of a carboxylic acid, a carboxylic acid anhydride, an acyl halide, a sulfonic acid, a sulfonic anhydride, a sulfonyl halide, a sulfinic acid, a sulfinic anhydride, a sulfinyl halide, a phosphoric acid, a phosphoric acid derivative, a phosphonic acid, and a phosphonic acid derivative; and effecting a second polymerization of the polymerizable, ethylenically- unsaturated resin initiated by the self-cure free radical initiator and/or the photo-initiated free radical initiator.

[0012] In another embodiment of the invention, a kit is provided comprising a first part comprising an epoxy compound; a second part comprising a polymerizable, ethylenically- unsaturated resin having an acid functional group, wherein the first and/or second part further comprises a radical initiator, wherein the first part and the second part are provided in packaging that physically separates the first part from the second part; and instructions for mixing to effect a self-cure.

[0013] In yet another embodiment of the invention, there is provided a method of providing a polymerizable composition comprising providing a first part comprising an epoxy compound; and providing a second part comprising a polymerizable, ethylenically-unsaturated resin having an acid functional group, wherein the first and/or second part further comprises a self-cure free- radical initiator and/or a photo-initiator free-radical initiator, whereby upon mixing the first part and the second part the acid functional group is adapted to initiate a cationic polymerization of the epoxy compound; and the self-cure free -radical initiator and/or a photo-initiator free -radical initiator is adapted to initiate a free-radical polymerization of the polymerizable, ethylenically- unsaturated resin.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention is related to a two-part polymerizable composition having improved adhesion or bond strength to a substrate. In one exemplary embodiment, a two-part paste/paste acidic self-adhering dental composition is provided, wherein the first part comprises an epoxy compound and the second part comprises a polymerizable, ethylenically-unsaturated resin having an acid functional group and the first part and/or the second part further comprises a radical initiator.

[0015] According to one embodiment of the invention, a self-adhesive two-part paste/paste dental composition is prepared for use by mixing together an epoxy compound and a polymerizable, ethylenically-unsaturated resin having an acid functional group, along with a radical initiator. This combination provides for two modes of cure for the resinous combination: epoxy ring-opening polymerization catalyzed by the acidic functional group and free-radical polymerization of the ethylene moieties.

[0016] As used herein, the term "self-cure" means the inventive compositions can go through a chemical polymerization process when the first part and the second part are mixed together, without an external energy such as heat, light, or other radiation energies. For example, the epoxy-ring opening polymerization through the cationic reaction of the epoxy and acid group contained in the polymerizable monomer and/or through a redox reaction of a peroxide-tertiary amine initiated free radical curing for the (meth)acrylate monomer(s) in the compositions. The sequence of the various polymerization mechanisms can be simultaneous, sequential, or even delayed with respect to the other(s).

[0017] The first part of the two-part polymerizable composition may comprise epoxy resins of many different structures. These epoxy resins include monomeric epoxy compounds and epoxides of the polymeric type and may be aliphatic, cycloaliphatic, aromatic or heterocyclic. These epoxy resins generally have, on the average, about one polymerizable epoxy group per molecule, but may include about two polymerizable epoxy groups per molecule. The polymeric epoxides include linear polymers having terminal epoxy groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol), polymers having skeletal oxirane units (e.g., polybutadiene polyepoxide), and polymers having pendent epoxy groups (e.g., a glycidyl methacrylate polymer or copolymer). The epoxides may be pure compounds or may be mixtures of compounds containing one, two, or more epoxy groups per molecule. The "average" number of epoxy groups per molecule is determined by dividing the total number of epoxy groups in the epoxy-containing material by the total number of epoxy-containing molecules present. [0018] These epoxy-containing materials may vary from low molecular weight monomeric materials to high molecular weight polymers and may vary greatly in the nature of their backbone and substituent groups. Illustrative of permissible substituent groups include halogens, ester groups, ethers, sulfonate groups, siloxane groups, nitro groups, phosphate groups, and the like. The molecular weight of the epoxy-containing materials may vary from about 58 to about 100,000 or more.

[0019] Useful epoxy-containing materials include those which contain cyclohexane oxide groups such as epoxycyclohexane carboxylates, typified by 3,4-epoxycyclohexylmethyl-3,4- epoxycyclohexane carboxylate, S^-epoxy-l-methylcyclohexylmethyl-S^-epoxy-l- methylcyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. [0020] Other epoxy-containing materials that are useful in this invention include glycidyl ether monomers, such as glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin such as epichlorohydrin (e.g., the diglycidyl ether of 2,2- bis-(2,3-epoxypropoxyphenol)-propane).

[0021] Still other epoxy resins contain copolymers of acrylic acid esters or glycidol such as glycidylacrylate and glycidylmethacrylate with one or more copolymerizable vinyl compounds. Examples of such copolymers are 1 : 1 styrene-glycidylmethacrylate, 1 : 1 methylmethacrylate- glycidylacrylate and a 62.5:24:13.5 methylmethacrylate-ethyl acrylate-glycidylmethacrylate. [0022] Other useful epoxy resins are well known and contain epoxides, such as epichlorohydrins; alkylene oxides, e.g., propylene oxide; styrene oxide; alkenyl oxides, e.g., butadiene oxide; and glycidyl esters, e.g., ethyl glycidate.

[0023] Blends of various epoxy-containing materials are also contemplated. Examples of such blends include two or more weight average molecular weight distributions of epoxy-containing compounds, such as low molecular weight (below 200), intermediate molecular weight (200 to 10,000) and high molecular weight (above 10,000). Alternatively or additionally, the epoxy resin may contain a blend of epoxy-containing materials having different chemical natures, such as aliphatic and aromatic, or different functionalities, such as polar and non-polar. [0024] There are a host of commercially-available epoxy resins which can be used in this invention. In particular, epoxides which are readily available include octadecylene oxide, epichlorohydrin, styrene oxide, vinylcyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ether of Bisphenol A (e.g., those available under the trade designations "Epon 828", "Epon 825", "Epon 1004" and "Epon 1010" from Shell Chemical Co., "DER-331", "DER-332", and "DER-334", from Dow Chemical Co.), vinylcyclohexene dioxide (e.g., "ERL-4206" from Union Carbide Corp.), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (e.g., "ERL-4221" or "CYRACURE UVR 6110" or "UVR 6105" from Union Carbide Corp.), 3,4- epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methyl-cyclohexen e carboxylate (e.g., "ERL- 4201" from Union Carbide Corp.), bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (e.g., "ERL-4289" from Union Carbide Corp.), bis(2,3-epoxycyclopentyl)ether (e.g., "ERL-0400" from Union Carbide Corp.), aliphatic epoxy modified from polypropylene glycol (e.g., "ERL- 4050" and "ERL-4052" from Union Carbide Corp.), dipentene dioxide (e.g., "ERL-4269" from Union Carbide Corp.), epoxidized polybutadiene (e.g., "Oxiron 2001" from FMC Corp.), silicone resin containing epoxy functionality, flame retardant epoxy resins (e.g., "DER-580", a brominated bisphenol type epoxy resin available from Dow Chemical Co.), 1,4-butanediol diglycidyl ether of phenolformaldehyde novolak (e.g., "DEN-431 " and "DEN-438" from Dow Chemical Co.), resorcinol diglycidyl ether (e.g., "Kopoxite" from Koppers Company, Inc.), bis(3,4-epoxycyclohexyl)adipate (e.g., "ERL-4299" or "UVR-6128", from Union Carbide Corp.), 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta- dioxane (e.g., "ERL- 4234" from Union Carbide Corp.), vinylcyclohexene monoxide 1,2-epoxyhexadecane (e.g., "UVR-6216" from Union Carbide Corp.), alkyl glycidyl ethers such as alkyl C ₈ -C _1O glycidyl ether (e.g., "HELOXY Modifier 7" from Shell Chemical Co.), alkyl Ci ₂ -Ci ₄ glycidyl ether (e.g., "HELOXY Modifier 8" from Shell Chemical Co.), butyl glycidyl ether (e.g., "HELOXY Modifier 61" from Shell Chemical Co.), cresyl glycidyl ether (e.g., "HELOXY Modifier 62" from Shell Chemical Co.), p-ter butylphenyl glycidyl ether (e.g., "HELOXY Modifier 65" from Shell Chemical Co.), polyfunctional glycidyl ethers such as diglycidyl ether of 1,4-butanediol (e.g., "HELOXY Modifier 67" from Shell Chemical Co.), diglycidyl ether of neopentyl glycol (e.g., "HELOXY Modifier 68" from Shell Chemical Co.), diglycidyl ether of cyclohexanedimethanol (e.g., "HELOXY Modifier 107" from Shell Chemical Co.), trimethylol ethane triglycidyl ether (e.g., "HELOXY Modifier 44" from Shell Chemical Co.), trimethylol propane triglycidyl ether (e.g., "HELOXY Modifier 48" from Shell Chemical Co.), polyglycidyl ether of an aliphatic polyol (e.g., "HELOXY Modifier 84" from Shell Chemical Co.), polyglycol diepoxide (e.g., "HELOXY Modifier 32" from Shell Chemical Co.), bisphenol F epoxides (e.g., "EPN-1138" or "GY-281" from Ciba-Geigy Corp.), and 9,9-bis[4-(2,3- epoxypropoxy) -phenyl] fluorenone (e.g., "Epon 1079" from Shell Chemical Co.). [0025] Additionally, the epoxy resin may be accompanied by a variety of other resins, including free radically-polymerizable resins, ionically-polymerizable resins, or combinations thereof, provided that the resins do not contain an acid functional group. Examples of free radically-polymerizable resins include, but are not limited to those resins with ethylenically unsaturated functional groups, such as (meth)acrylates; vinyl monomers, such as styrene; vinyl esters; and a variety of unsaturated cyclic monomers, such as spiro-ortho carbonates, spiro- ortho esters, vinyl cyclic ethers, and cyclic acetals.

[0026] Examples of ionically-polymerizable resins include, but are not limited to, vinyl ethers; and cyclic monomers, such as epoxies, siloranes, lactides, ε-caprolactones, and ε-caprolactams. [0027] Examples of resins containing both free radically- and ionically-active functional groups include, but are not limited to, the resin oligomers having both an epoxy functionality and a (meth)acrylate functionality as set forth in commonly owned U.S. Patent No. 7,241,856, which is hereby incorporated by reference.

[0028] Examples of ethylenically-unsaturated resins include those based on acrylate and methacrylate monomers, for example those disclosed in U.S. Patent Nos. 3,066,112, 3,179,623, and 3,194,784 to Bowen; U.S. Patent Nos. 3,751,399 and 3,926,906 to Lee et al.; and commonly assigned U.S. Patent No. 5,276,068 to Waknine, all of which are herein incorporated by reference in their entirety. Methacrylate-based monomers are particularly useful, including the condensation product of bisphenol A and glycidyl methacrylate; 2,2'- bis[4-(3-methacryloxy-2-hydroxy propoxy) -phenyl] -propane (BIS-GMA); dipentaerythritol pentaacrylate (DPEPA); pentaerythritol dimethacrylate (PEDM); the condensation product of ethoxylated bisphenol A and glycidyl methacrylate (EBPA-DMA); urethane dimethacrylate (UDMA); ethoxylated bisphenol A di(meth)acrylates including ethoxylated bisphenol A dimethacrylate (EBPDMA) as disclosed in U.S. Patent No. 6,013,694 to Jia, et al.; the condensation product of 2 parts hydroxymethylmethacrylate and 1 part Methylene glycol bis(chloroformate) (PCDMA); polyurethane -based dimethacrylates (PUDMA) and polycarbonate modified-BisGMA (PCBisGMA) and other monomers set forth in commonly owned U.S. Patent No. 6,787,629, which is hereby incorporated by reference. [0029] This first part may also contain other additives, such as radiopaque and thickening fillers. Additionally, free radical initiator systems that are compatible with an epoxide functional group may also be included. For example, light initiators, such as camphorquinone (CQ); and co-initiators, such as ethyl-4-dimethyl benzoate (EDMAB); are particularly suitable for use. Self-cure inititiators as reducing agents for the free-radical polymerization of methacrylates, such as bis(2-hydroxylethyl)-p-toluidine (DHEPT), dimethyl-p-toluidine (DMPT), and thioureas, may also be included. The commonly-known epoxy addition reaction polymerization initiators, such as a primary or a secondary amine should not be included. [0030] The second part of the multi-part polymerizable composition, which comprises a polymerizable, ethylenically-unsaturated resin having an acid functional group, includes aliphatic or aromatic polymerizable resin monomers or oligomers. It is generally understood that the acid functional group facilitates the self-etching or self-adhering effect to the tooth structure, as well as acts as an initiator of the epoxy polymerization reaction. Furthermore, in one embodiment, an ionic reaction between the acid group of the ethylenically-unsaturated resin and the surface of an acid-reactive glass ionomer filler is also possible when there is water/moisture present.

[0031] These polymerizable monomers or oligomers comprise at least one acidic functional group, which includes acid-precursor functional groups, such as anhydrides. For example, an anhydride may react with water, an alcohol or the like to form a carboxylic acid. As such, an acidic functional group may be a carboxylic acid, carboxylic acid anhydride, acyl halide, sulfonic acid, sulfonyl halide, sulfonic anhydride, sulfinic acid, sulfinyl halide, sulfinic anhydride, phosphoric acid, phosphoric acid derivative, phosphonic acid, and phosphonic acid derivative, and combinations thereof. Additionally, the polymerizable monomers or oligomers comprise at least one polymerizable unsaturated carbon - carbon bond, such as an alkene functional group. In one embodiment, the polymerizable, ethylenically-unsaturated resin is an ethylenically-unsaturated carboxylic acid.

[0032] In another embodiment, the polymerizable, ethylenically-unsaturated resin contains at least two acidic functional groups. For example, the ratio between the number of acidic functional groups and the number of polymerizable unsaturated carbon - carbon bonds in the polymerizable, ethylenically-unsaturated resin may range between about 1:3 to about 3:1, for example, about 1:2 to about 2:1.

[0033] Exemplary polymerizable, ethylenically-unsaturated resins include, but are not limited to, acrylic acid, methacrylic acid, 2-(methacryloyloxy)ethyl phosphate, bis(2- (methacryloyloxy)ethyl) phosphate, biphenyl dimethacrylate, ethylene glycol methacrylate phosphate, 4-methacryloxyethyl trimellitic anhydride, 4-methacryloxyethyl trimellitic acid, adduct reaction product of pyromellitic di-anhydride with 2-hydroxyethylmethacrylate, adduct reaction product of pyromellitic di-anhydride with glycerol dimethacrylate, or adduct reaction product of benzenetetracarboxylic acid di-anhydride with 2-(6-hydroxy-l-oxo-hexyloxy)ethyl methacrylate.

[0034] Another suitable class of polymerizable, ethylenically-unsaturated resins is an ethylenically-unsaturated phosphoric acid ester having the general formula:

(CH ₂ =C(CH ₃ )CO ₂ -R-O) _n P(O)(OH) ₃ ^

[0035] wherein R is a substituted or un- substituted alkyl or aryl group having about 1 to about 36 carbon atoms and n equals 1 or 2.

[0036] Additionally, the second part may further include a variety of other resins that do not have an acid functional group, including free radically-polymerizable resins, ionically- polymerizable resins, or combinations thereof, as discussed above, provided that the resin is stable under reasonable storage conditions in the presence of an acid functional group and the other constituents included in this mixture. The second part may also contain other additives, such as radiopaque and thickening fillers. Self-cure initiators compatible with the acidic media may also be included. For example, oxidizing agents such as benzoyl peroxide or cumene hydroperoxide are suitable for use.

[0037] Known viscous resins may be added to the first part or the second part of the polymerizable composition. Non-limiting examples include polyurethane dimethacrylates (PUDMA), diurethane dimethacrylates (DUDMA), and/or the polycarbonate dimethacrylate (PCDMA) disclosed in U.S. Patent Nos. 5,276,068 and 5,444,104 to Waknine, which is the condensation product of two parts of a hydroxyalkylmethacrylate and 1 part of a bis(chloroformate). Another advantageous resin having lower water sorption characteristics is an ethoxylated bisphenol A dimethacrylate (EBPDMA) as disclosed in U.S. Patent No. 6,013,694. An especially useful methacrylate resin is the condensation product of bisphenol A and glycidyl methacrylate, 2,2'-bis [4-(3-methacryloxy-2-hydroxy propoxy) -phenyl] -propane (Bis-GMA).

[0038] Diluent monomers may be added to the first part or the second part of the polymerizable composition to increase the surface wettability of the composition and/or to decrease the viscosity of the polymerization medium. Suitable diluent monomers include those known in the art such as hydroxy alkyl methacrylates, for example 2-hydroxyethyl methacrylate and 2- hydroxypropyl methacrylate; ethylene glycol methacrylates, including ethylene glycol methacrylate, diethylene glycol methacrylate, tri(ethylene glycol) dimethacrylate and tetra(ethylene glycol) dimethacrylate; and diol dimethacrylates such as butanedimethacrylate, dodecanedimethacrylate, or 1,6-hexanedioldimethacrylate (HDDMA). Tri(ethylene glycol) dimethacrylate (TEGDMA) is particularly suitable for use.

[0039] Diluent monomers or viscous resins, when present, are incorporated into the polymerizable composition in an amount of about 1 to about 70 wt % of the total composition. Optionally, excess water or alcohol may be included.

[0040] As stated above, the composition further includes a radical polymerization curing system to facilitate another mechanism for curing the polymerizable resins. These initiator systems may include polymerization initiators; polymerization accelerators; ultraviolet light absorbers; antioxidants; and other additives known in the art.

[0041] A light cure system may be selected from known light- activated polymerization initiators, including but not being limited to benzil, benzoin, benzoin methyl ether, DL- camphorquinone (CQ) and benzil diketones. Either UV-activated cure or visible light- activated cure (about 230 nm to about 750 nm) is acceptable. The amount of photoinitiator may be selected according to the curing rate desired. A minimally catalytically effective amount is generally about 0.01% by weight of the polymeric components. Faster rates of cure are achieved with amounts of catalyst in the range from greater than about 0.01% to about 5% by weight of the polymeric component. Visible light curing systems may further comprise polymerization accelerators, which include various organic tertiary amines well known in the art. In visible light curable compositions, the tertiary amines may be acrylate derivatives such as dimethylaminoethyl methacrylate and, particularly, diethylaminoethyl methacrylate (DEAEMA) and aromatic tertiary amines such as ethyl dimethylamino benzoate (EDMAB) in amounts in the range from about 0.05 to about 2 weight percent, for example from about 0.1 to about 0.5 weight percent.

[0042] Alternatively, the composition may be formulated as a self-curing system. Self-curing compositions will generally contain free radical polymerization initiators, such as a peroxide in an amount of about 0.01 to about 2.0 wt % of the total resin composite material. Particularly suitable free radical initiators include lauryl peroxide, tributyl hydroperoxide, benzoyl peroxide, and cumene hydroperoxide.

[0043] Polymerization accelerators suitable for use are the various organic tertiary amines well known in the art. In visible light curable composite materials, the tertiary amines are generally acrylate derivatives, such as dimethylaminoethyl methacrylate and, particularly, diethylaminoethyl methacrylate (DEAEMA) in an amount of about 0.05 to about 0.5 wt % of the total composition.

[0044] In the self-curing compositions, the tertiary amines are generally aromatic tertiary amines. For example, tertiary aromatic amines such as ethyl 4-(dimethylamino)benzoate (EDMAB), 2-[4-(dimethylamino)phenyl]ethanol, N,N-dimethyl-p-toluidine (DMPT), and bis(hydroxyethyl)-p-toluidine are commonly useful. Such reducing agents are generally present in an amount of about 0.5 to about 4.0 wt % of the total composition. A thiourea or its derivative reducing agent may also be used in the compositions as taught by U.S. Patent No. 7,275,932, assigned to Jin, et al.

[0045] The compositions may also comprise other additives and solvents known in the art, for example, ultra-violet light absorbers; anti-oxidants such as BHT; stabilizers; fillers; pigments; opacifiers; handling agents/rheology modifiers; fluorescence agent; antimicrobial agents; therapeutical and/or bioactive components; mineralization promoting agent or filler; and others. For example, it is useful to employ an ultraviolet absorber in an amount of about 0.05 to about 5.0 wt % of the total composition. Such UV absorbers are particularly desirable in the visible light curable compositions in order to avoid discoloration of the resin from incident ultraviolet light. Suitable UV absorbers are the various benzophenones, particularly UV-5411 available from American Cyanamid Company; and benzotriazoles known in the art, particularly 2-(2'- hydroxy-5'-methylphenyl)-benzotriazole, sold under the trademark TINUVIN® P by Ciba- Geigy Corporation, Ardsley, N. Y.

[0046] Suitable fillers may be particulate or fibrous fillers with sizes from nano-scales to micron- scales. Fillers conventionally used in the dental industry that are capable of being covalently bonded to the resin matrix itself or to a coupling agent may be included. Such fillers are described in U.S. Patent Nos. 4,544,359 and 4,547,531, the pertinent portions of which are hereby incorporated by reference. Examples of suitable filling materials include but are not limited to amorphous silica; spherical silica; colloidal silica; barium glasses; quartz; ceramic fillers; silicate glass; hydroxyapatite; calcium carbonate; fluoroaluminosilicate; barium sulfate; quartz; barium silicate; strontium silicate; barium borosilicate; barium boroaluminosilicate; strontium borosilicate; strontium boroaluminosilicate; bioglass; dental glass ionomer filler; glass fibers; lithium silicate; ammoniated calcium phosphate; deammoniated calcium phosphate; calcium tungstate; alumina; zirconia; tin oxide; zinc oxide; calcium oxide; bismuth compounds such as bismuth oxychloride and bismuth oxide; polymer powders such as polymethyl methacrylate, polystyrene, and polyvinyl chloride; titanium dioxide; bound and nano structured silica fillers as set forth in commonly owned U.S. Patent No. 6,417,246, which is hereby incorporated by reference; densified and embrittled glass fibers or particles as set forth in commonly owned U.S. Patent Nos. 6,013,694 and 6,403,676, which are hereby incorporated by reference; fibrous material and one or more forms of surface-modifying particles bonded thereto as set forth in commonly owned U.S. Patent No. 6,270,562, which is hereby incorporated by reference; polyhedral oligomeric silsesquioxane fillers as set forth in U.S. Patent No. 6,653,365, which is hereby incorporated by reference; nanostructures such as POSS™ (polyhedral oligomeric silsesquioxane) supplied by Hybrid Plastics; and combinations of all the fillers mentioned. Particularly suitable fillers for dental filling-type materials prepared are those having a particle size in the range from about 0.01 to about 10 μm, together with a colloidal silica or fumed silica having particle sizes in the range from about 0.001 to about 0.07 μm.

[0047] A coupling agent may be used with the filler or the filler may be pretreated with a coupling agent, such as a silane coupling agent. For example, a commonly used coupling agent in the dental industry is γ-methacryloxypropyltrimethoxy silane.

[0048] In one particular embodiment, the composition may further include an acid-reactive filler, such as a glass ionomer (GI) filler. Contact between the acid functional group and the acid-reactive GI filler, in the presence of water or moisture, facilitates a self -hardening in the dark due to an ionic reaction between the acidic group and the surface of the GI filler. This provides a complementary polymerization to the epoxy ring-opening and free-radical polymerizations, as discussed above.

[0049] Therefore, according to embodiment of the invention, a two-part composition is provided wherein the first part comprises an epoxy-containing compound, and optionally non- epoxy containing compounds which can be (meth)acrylates without acidic groups; and a second part comprises a polymerizable, ethylenically-unsaturated resin having an acid functional group. The weight ratio between epoxy-containing compound and polymerizable, ethylenically-unsaturated resin having an acid functional group can vary depending on the type of acid and epoxy, as well as the applications. In one embodiment, the range is from about 1:10 to about 10:1; for example about 1:5 to about 5:1. A suitable radical polymerization initiator may be included in one or both of the aforementioned parts. [0050] As such, a convenient procedure can be realized when the two-part polymerizable composition is pre-packaged, such that the desired mixing ratio is provided upon use. For example, a dental composition may be packaged in a dual-syringe assembly, two individual non-joined syringes, two tubes, two capsules, one capsule where the two pastes are segregated and do not come in contact with each other, blister packs, etc., as known to one skilled in the art. The above are examples of pre-packaged containers, which provide the first part and the second part in packaging that physically separates the first part from the second part. [0051] The dual-syringe assembly may be fitted with a static mixer/tip so that the two pastes are mixed in the static mixer to result in a homogenous or a substantially homogenous composition which flows out from the tip. The dental practitioner can dispense the homogeneously mixed composition directly to a dental substrate, resulting in significant time savings and convenience in addition to improved adhesion.

[0052] This invention is illustrated by the following examples that are merely for the purpose of illustration and are not to be regarded as limiting the scope of the invention or the manner in which it can be practiced.

EXAMPLES

[0053] Materials used for the following examples are set forth in Table A below. The recited percentage for a specific additive included in a given resin component is a weight percentage based on the total weight of the resin component.

Table A: Materials used in examples.

Abbreviation Chemical Name Producer

UVR6110 Cyracure ™ Cycloaliphatic epoxide resin Dow Chemical

Epoxy 06 Cycloaliphatic epoxide resin equivalent to UVR6110 Synasia, NJ

BADGE Bisphenol A diglycidyl ether - DER332 Dow Chemical

BFDGE Bisphenol F diglycidyl ether Sigma Aldrich

RDGE Resorcinol digycidylether Sigma Aldrich

NGDGE Neopentyl glycol diglycidyl ether Sigma Aldrich

4-MET 4-Methacryloxyethyl trimellitic acid Pentron

HEMA 2-Hydroxyethyl methacrylate Degussa

MMA Methacylic acid Sigma Aldrich

BEPMA Bis[2-(Methacryloyloxy)-ethyl] phosphate Sigma Aldrich

EGPMA Ethylene glycol methacrylate phosphate Sigma Aldrich

TEGDMA Triethyleneglycol dimethacrylate Esstech,PA

R7200 Silane treated fumed silica based on Aerosil A200 Degussa Corp

GI Glass ionomer filler, 4 micron particles IndustrialCorporation

BiOCl Bismuth oxychloride Engelhard

CaWO ₄ Calcium Tung state Sigma Aldrich

Barite Barium Sulfate Sachtleben Corp.

Example 1

[0054] Cationic curing test of epoxy with various acidic methacylates [0055] For the curing tests of Example 1, the compositions utilized for the epoxy pastes (UVR6110, BFDGE/TEGDMA, BADGE/TEGDMA, RDGE and NGDGE) and the acidic methacrylate pastes (4-MET/HEMA, MMA, BEPMA and EGPMA) are shown in Table 1. The BADGE/TEGDMA resin was prepared by mixing BADGE and TEGDMA in 90/10 weigh ratio. The 4-MET/HEMA resin was prepared by mixing 4-MET with HEMA in 67/33 weight ratio. The remaining resins (MMA, EGPMA and UVR6110) were used as received. The resin and fillers were mixed together and yielded a flowable consistency. The curing tests were performed at 38° C by mixing an equivalent portion, by weight, of each epoxy paste and each acidic methacrylate paste. By monitoring the gel times of the curing samples, the chemical reactivity upon mixing between an epoxy and an acidic methacrylate resin composition was determined. (As a definition, the gel time here is the interval of time required for the flowable resin composition to become a semisolid jelly or viscosity build-up significantly from the original pasty consistence). The gel time is recorded in Table 2.

Table 1: Epoxy and acidic methacrylate paste composition.

Paste Resin Paste composition

Ell UVR6110 50% resin, 50% GI

E12 BFDGE/TEGDMA (90/10) 50% resin, 50% GI

E13 BADGE/TEGDMA (90/10) 50% resin, 50% GI

E14 RDGE 38% resin, 62% GI

E15 NGDGE 34% resin, 66% GI

Mil 4-MET/HEMA (67/33) 50% resin, 50% BiOCl

M12 MMA 41% resin, 2% R7200, 57% BiOCl

M13 BEPMA 43% resin, 2% R7200, 55% BiOCl

M14 EGPMA 43% resin, 2% R7200, 55% BiOCl

Table 2: Epoxy and acidic methacrylate paste curing test.

Curing test Gel time at RT Gel time at 38 ⁰ C

E11-M12 1 hr 30 min 30 min

E11-M13 10 sec < 5 sec

E11-M14 10 sec < 5 sec

E12-M11 >24 hrs 15 hrs

E12-M12 >24 hrs >24 hrs

E12-M13 2 hrs 30 min

E13-M13 2 hrs 30 min

E14-M13 2 hrs 30 min

E15-M13 5 hrs 1 hr 30 min

Example 2

[0056] Epoxy resin cationic curing test monitored by FTIR

[0057] Epoxy resin UVR6110 and 4-MET/HEMA/UDMA (in a weight ratio of 60/30/10) resin were mixed in 1:1 weight ratio and maintained at a temperature of 38° C while the polymerization reaction was monitored by FTIR. After 5 hours at 38° C, it was observed that the composition had an increased viscosity and the epoxy peak in the IR spectrum at 898 cm ^"1 was observed to have decreased intensity relative to when the resins were initially mixed. The disappearance of epoxy peak at 898 cm ^"1 , as well as the hardening of mixed resin, were observed after 24 hours of curing at 38° C, indicating the epoxide had undergone a ring-opening polymerization in the presence of 4-MET. It could be visually determined that the cured resin had a dry surface.

Example 3

[0058] Epoxy Resin cationic curing and methacrylate free radical curing test [0059] Light initiator CQ (0.4%) and co-initiator EDMAB (1.0%) were added to a sample of UVR6110 resin. Stabilizer BHT (0.02%) and peroxide BPO (2.5%) were added to a sample of 4-MET/HEMA/UDMA (in a weight ratio of 60/30/10) resin. The two resins were mixed in 1:1 weight ratio and the polymerization was monitored by FTIR. The resin hardened after 30 minutes, but the surface remained wet at that time. The observed faster rate of hardening of the resin mixture, as compared to Example 2, indicates that the methacrylate free radical polymerization occurred before the epoxide ring-opening polymerization. The surface layer demonstrated a curing behavior similar to Example 2, however. A subsequent FTIR scan of the surfaced layer was conducted at 5 hours and 24 hours after the cure and showed a similar disappearance of the epoxy peak at 898 cm ^"1 , as in Example 2.

Example 4

[0060] Paste-paste epoxy cationic curing and methacrylate free radical curing test

[0061] Each resin in Example 2 and Example 3 was mixed with fillers to obtain a flowable consistency. The paste compositions are listed in Table 3. The curing test was performed by mixing 1:1 weight ratio of epoxy paste and methacrylate paste. Gel time was tested at both room temperature and 38° C. The test results were shown in Table 4.

Table 3: Epoxy and methacrylate paste composition.

Paste Resin Paste composition

^~ E4Ϊ UVR6110 in Example 2 47% resin, 1% R7200, 15% GI, 25% BiOCl,

12% Ca ₃ (PO ₄ ) ₃ E42 UVR6110 in Example 3 47% resin, 1% R7200, 15% GI, 25% BiOC,

(contains CQ & EDMAB) 12% Ca ₃ (PO ₄ ) ₃ M41 4-MET/HEMA/UDMA 49.5% resin, 0.5% R7200, 50% BiOCl

60/30/10 in Example 2 M42 4-MET/HEMA/UDMA 49.5% resin, 0.5% R7200, 50% BiOCl 60/30/10 in Example 3

Table 4: Epoxy and methacrylate paste curing test.

Curing test Gel time at RT Gel time at 38° C

E41-M41 24 hr 12 hr E42-M42 2 hr 40 min

[0062] A significantly faster curing rate was observed for the epoxy/methacrylate composition containing the peroxide free radical polymerization initiator, as shown in Table 4. Moreover, the E42-M42 system is also light curable. The dual cure (light and self-curable) nature and working time is suitable for root canal sealant applications.

Example 5

[0063] Property test of cured epoxy/methacrylate compositions as root canal sealant [0064] The epoxy paste E42 and acidic methacrylate paste M42 were mixed in 1 : 1 weight ratio and the properties were tested and summarized in Table 5. The surface residue monomer of the cured paste was evaluated by measuring the removable/wipable surface residue monomer amount. The catalyst and base paste, 0.25 g each, were mixed and the resultant paste was applied as a film to a glass slide without covering the film. The paste was spread on the glass slide in a way that the film thickness of the paste varied from approximately 0.1mm to 1.0 mm. After the paste gelled at room temperature, it was placed under different conditions: 1) room temperature for over 24 hours, 2) 37° C for over 12 hours without moisture, 3) 37° C for over 24 hours with 100% humidity. The glass slide, which included the cured sealer material, was first weighed to obtain an original weight, then the surface of the cured sealer material was wiped with lint free Kimwipes®. The glass slide was weighed again to obtain a final weight. The residue monomer % value was calculated as the weight percent difference of the final weight and the original weight.

[0065] For physical properties evaluation, the pastes were mixed and set at 37° C for 24 hours, and then stored at 37° C in water for 24 hours for the flexural strength (FS) testing and 1 week for water absorption (WA) and water solubility (WS) testing in reference to ISO 4049 (Dentistry — Polymer-based filling, restorative and luting materials) method for the sample dimensions and sizes. Table 5: Summary of cured epoxy/methacrylate compositions as root canal sealant.

Property tested Property value

Residue monomer %

RT over 24 hrs 0

37° C over 12 hrs no moisture 0

37° C over 12 hrs 100% humidity 0

FS (MPa) 51

WA(μg/mmVweek) 52

WS (μg/mmVweek) 0

[0066] Two commercial epoxy resin-based root canal sealers (AH Plus Jet® and AH Plus® Silver free); one commercial acid-containing methacrylate resin based root canal sealant (Epiphany® SE); and one self-etching (SE) root canal sealant (RCS) composition according to an embodiment of the present invention ("Exp. SE RCS") were tested for dimensional change and 24 hours' solubility according to AD A/ ANSI Specification No. 57 "Endodontic Sealing Material". A comparison of the results is shown below in Table 6.

Table 6: Water solubility and expansion.

Material Manufacturer Lot# Expansion ¹ Solubility ²

%

Exp. SE RCS Pentron Clinical Tech. Experimental 1.00 0.003

AH Plus Jet Dentsply 0801000301 0.64 0.01

AH 26 Silver Dentsply 0710000944 3.2 0.08

Free

Epiphany SE Pentron Clinical 163647 3.5 0.13

Technologies

¹ Expansion is the linear percentage change after 30 days in distilled water. Weight percent soluble in distilled water after 24 hours.

Example 6

[0067] Self-adhering root canal sealant tooth bonding test

[0068] Bonding strength of the Exp. SE RCS composition to dentin was compared to a self- etch sealant (Epiphany® SE); an acid-containing methacylate resin-based self-etch root canal sealant (Pentron Corp.); and an epoxy-amine based root canal sealer material (AH Plus® Jet), which is packaged in a double barrel dental syringe like the Epiphany® SE. Six rods (3 mm in diameter, 6 mm height cylinder) were made using each of the materials being tested. Similar to a conventional dentin bonding test, coronal dentin surface was exposed and ground first (n=6). The dentin surfaces were subjected to a standard endodontic cleaning procedure using 5% sodium hypochlorite (NaOCl) and 17% ethylenediamine tetraacid (EDTA) solutions sequentially (Epiphany Instruction of Use, Pentron Corp.). The rods were then applied and adhered onto the dentin surface using the corresponding sealer as the cement there between the rod and dentin surface under a pressure load of a 500 gram weight on top of the composite rod. The excess sealer was removed using a spatula. The sealant was first light cured for 30 seconds from two sides of the composite rod and then removed from load and further self-cured (allow to stand on bench) for 30 minutes before transferring into a container with 100% humidity in a 37° C oven for 48 hours. Because AH Plus Jet® material is epoxy- amine chemically-cured and the working and setting times are much longer, the bonding samples were allowed to set on bench under the 500 gram load for at least 24 hours before transferring to the 37° C oven. Bonding strengths were then tested by breaking the composite rod off the dentin surface using an ATS Universal Testing Machine with a push-shear direction. The load was then recorded and the bonding strength was calculated using the load divided by the surface area of the rod adhering to the dentin surface. The test results are shown in Table 7 below. As can be seen, the bonding strength to dentin of the Exp. SE RCS of the invention is unexpectedly much better over the current commercially available Epiphany® SE sealant and the AH Plus Jet® epoxy- based sealer.

Table 7: Bonding strength of self-etch/self adhering I root canal sealant on dentin surface.

Sealant Epiphany SE ² Exp. SE RCS AH Plus Jet ³

Bonding strength ¹ (MPa) 2.4(1.0) 6.3(2 •5) 0.39 (0.1)

¹ Bonding strength to Dentin (MPa)

² Lot#162744

³ Lot# 0801000301

[0069] As can be seen from the data in Table 7, the bonding strength of the Exp. SE RCS demonstrates about a 2.5 times increase in bonding strength, as compared to the methacrylate resin based composition with acidic methacrylate monomer (Epiphany® SE), and about a 16 times increase over that of an epoxy resin-based composition using epoxy-amine root canal sealer (AH Plus Jet®). The Exp. SE RCS, as formulated, can therefore be used as a root canal filling material, either alone or in combination with a conventional root canal filling material such as a Gutta Percha cone, a RealSeal point made from Resilon™ material, a carrier based point such as ThermaFil™ (product of Dentsply) or RealSeal 1™ (product of SybronEndo), in a dental root canal treatment procedure.

Example 7

[0070] Property test of another experimental self-etching root canal sealer (SE RCS). [0071] In this example, Epoxy 06 was used as replacement of UVR6110 because Dow discontinued the chemical supply. Radio-opacifier filler calcium tungstate and barium sulfate were used to replace bismuth oxychloride. The formulation of this experimental self-etch root canal sealer is shown in Tables 7a and 7b.

Table 7a: Catalyst paste formulation.

Catalyst paste composition Catalyst paste composition

(wt%)

4-META 27

HEMA 13.5

UDMA 4.5

BHT 0.09

BPO 1.11

Silane-treated barium glass filler 25.8

Barite 28

Table 7b: Base paste formulation.

Base paste composition Base paste composition

(wt%)

Epoxy 06 28.45

CQ 0.15

EDMAB 0.3

DHEPT 0.05

Y#8087 pigment 0.05

Silane-treated fumed silica 2

Barite 9

Calcium Tungstate 52

GI 8 [0072] Properties were tested on this experimental SE RCS. The residue monomer %, FS, expansion and solubility tests were performed as describe in Example 5. Bonding strength test was performed as described in Example 6. The properties are summarized in Table 8.

Table 8: Property summary of experimental SE RCS.

Property tested Property value

Residue monomer %

RT over 24 hrs 0

37° C over 12 hrs no moisture 0

37° C over 12 hrs 100% humidity 0

FS (MPa) 41(4)

Expansion (%) 2.63

Water Solubility (%) 0.08

Bonding strength to dentin (MPa) 6.03 (2.77)

[0073] While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. For example, dental applications have been described for embodiments of the invention, but other non-dental applications may likewise benefit from the inventive composition. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative product and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.