METAL FILLED ADHESIVE COMPOSITION AND METHOD

Abstract: An adhesive composition comprising an ethylenically unsaturated compound, a particulate metallic filler, and a curing agent. Also disclosed is a method of adhering a restorative material such as amalgam to hard tissue such as dentin or enamel, involving the use of an adhesive composition of the invention as an intermediate layer between the restorative material and the hard tissue.

Description: METAL FILLED ADHESIVE COMPOSITION AND METHOD BACKGROUND OF THE INVENTION Technical Field This invention relates to adhesive compositions comprising an ethylenically unsaturated compound. In another aspect, this invention relates to adhesive compositions comprising a particulate metallic filler. This invention also relates to methods of adhering a restorative material to a substrate, and in another aspect to methods of adhering a dental restorative such as amalgam to hard tissue such as dentin or enamel. Description of the Related Art Dental amalgams and restorative composites are used extensively for intracoronal and extracoronal restorations. Amalgam, however, does not adhere to tooth structure and the dentist must prepare the tooth cavity with dovetails and various cutout grooves that mechanically lock the amalgam into the cavity. Such preparation, however, results in excavation of more tooth structure than would otherwise be necessary if there was good adhesion between the tooth structure and the amalgam. Moreover, leakage at the interface of the amalgam and cavity wall (known as "microleakage") tends to occur. This microleakage allows penetration of bacteria, soluble salts, and saliva into any space between the amalgam and tooth structure. This can lead to inflammation, pulp irritation, demineralization of the tooth, corrosion of the amalgam, and other attendant complications. An adhesive seal between amalgam and tooth structure could minimize and/or prevent microleakage and allow for a stronger restoration due to excavation of less tooth material. Products claiming to make amalgam adhesive to tooth structure are available. One such product is sold in a kit under the trademark AMALGAMBOND™ (Parkell Co.). This product is a liquid adhesive to be coated directly onto tooth structure. The active ingredients in the adhesive include 4-META (4-methacryloxyethyl trimellitic anhydride) and TBB (tri-n butyl borane) . Other products which similarly involve coating a specific curable resin directly onto tooth structure to make amalgam adhere are available under the trademarks PANAVIA™ Dental Adhesive (Kuraray Company) and SUPERBOND™ Adhesive (Sun Medical Co., Ltd., Kyoto, Japan) . These latter products also are difficult to employ, since there are a number of required preparatory steps for their application and curing. Articles that describe bonding of amalgam to tooth structure by precoating the tooth with ethylenically unsaturated adhesive resin include M. Staninec and M. Holt, Journal of Prosthetic Dentistry (1988), Vol. 59, pp. 397-402, A. Lacey and M. Staninec, Quintessence International (1989), Vol. 20, pp. 521-524, Y. Aboush and C. Jenkins, Br. Dent. J. (1989), Vol. 166, pp. 255- 257, Y. Aboush and R. Elderton, Br. Dent. J. (1991), Vol. 170, pp. 219-222, and Y. Aboush and R. Elderton, Dent. Mater. (1991), Vol. 7, pp. 130-132. The last article involves adhesion to previously hardened amalgam, whereas the other articles involve adhesion to fresh amalgam. Also, A. Ben-Amar, J. Am. Dent. Assoc. (1989) Vol. 119, pp. 725-728, describes a reduction in microleakage at the margins of amalgam restorations when "SCOTCHBOND" Dual Cure Dental Adhesive resin (3M) is applied to cavity margins prior to application of amalgam, and M. Mitrosky, Jr. , Quintessence International (1981) Vol. 9, pp. 871-874, describes the use of ethyl cyanoacrylate as a bonding agent beneath amalgam and composite restoratives. H. J. Staehle et al., Dtsch. Zahnartzt (1988) Vol. 43, pp. 952-957, describes the use of various dental adhesives and varnishes to adhere amalgam to dentin. Adhesive compositions that employ phosphorus- containing free-radically polymerizable compounds have been reported, see, e.g., M. Buonocore, . ileman, and F. Brudevold, J. Dent. Res.. 35. 846 (1956), M. Buonocore and M. Quigley, J. Amer. Dent. Assoc.. 57, 807 (1958), M. Anbar and E. Farley, J. Dent. Res.. 53. 879 (1974) , E. Farley, R. Jones, and M. Anbar, . Den . Res.. 56. 1943 (1977), U.S. Pat Nos. 3,882,600, 3,997,504, 4,222,780, 4,235,633, 4,259,075, 4,259,117, 4,368,043, 4,383,052, 4,499,251, 4,514,342, 4,515,930, 4,537,940, 4,539,382, and 4,544,467, European published patent application No. 0 058 483, and Japanese laid-open patent application (Kokai) Nos. 57-143372 and 57-167364. U.S. Pat. No. 3,513,123 (Saffir) describes a curable epoxy composition that can be added to amalgam in order to make the amalgam adhere to tooth structure. The curable epoxy composition contains a glycidyl ether type resin and a polyamine hardening agent. U.S. Pat. No. 4,064,629 (Stoner) describes a method for applying amalgam restorations. The method involves precoating the surfaces of a cavity within a carious tooth with a layer of an "adhesive-met l" lining composition. The metal of the lining composition is amalgamated by diffusion of the mercury from the subsequently applied conventional dental amalgam filling. The "adhesive-metal" lining composition is said to improve corrosion resistance of the dental amalgam filling and also to promote bonding between the amalgam restoration and the cavity surfaces. U.S. Pat. No. 4,001,483 (Lee, Jr. et al.) describes dental compositions for sealing margins between tooth structures and amalgam restorations therein, the compositions containing (a) an alkylene glycol di ethacrylate and/or its oligomer, (b) a polymerization initiator, (c) a polymerization accelerator and (d) a secondary monomer additive. U.S. Pat. No. 3,574,943 (Stark) describes a method of restoring a carious tooth whereby the cavity is excavated, lined with a layer of a polysiloxane pressure sensitive adhesive polymer dissolved in a fluorocarbon, and filled with amalgam. The polysiloxane layer is said to act as a barrier to leakage. Japanese Kokai 63-175085 describes an adhesive composition comprising an acid functional monomer, polymer, or copolymer, a vinyl monomer in which the acid functional component is soluble, an organic peroxide, and an aromatic amine or sulfinate salt. The composition is said to bond living tooth tissue to composites and amalgams. French Patent 2,561,521 describes an intermediate adhesive composition for sealing dental cavities and chemically securing amalgams, comprising a metal powder dispersed in an adhesive varnish. The composition contains metal powder, cellulosic varnish, ethyl acetate, amyl propionate, fluoride, and oil of pimento leaf. Japanese Kokai 63-250310 describes dental adhesive compositions containing (a) cellulose ether, (b) a vinyl monomer, (c) an organic peroxide, and (d) an aromatic amine or a sulfinate. The composition is said to be applicable to a wide variety of restorative materials, including composite resins, amalgam, alumina, gold, alloys, polymethyl methacrylate, polycarbonate, and the like. SUMMARY OF THE INVENTION This invention provides an adhesive composition, comprising: (i) an ethylenically unsaturated compound; (ii) a particulate metallic filler that does not interfere with the cure of the ethylenically unsaturated compound, in an amount effective to increase adhesion of amalgam to tooth structure when the composition is used as an intermediate layer between the amalgam and the tooth structure, compared to the adhesion obtained using a like composition absent the particulate metallic filler; and (iii) a polymerization initiator in an amount sufficient to effect cure of the composition. This invention also provides an adhesive composition, comprising: (i) an ethylenically unsaturated compound; (ii) a particulate metallic filler that does not interfere with the cure of the ethylenically unsaturated compound, in an amount of about 50 to about 4000 parts by weight based on 100 parts by weight of the ethylenically unsaturated compound; and (iii) a polymerization initiator in an amount sufficient to effect cure of the composition. This invention also provides a method of adhering a restorative material to a substrate, comprising the steps of: (i) combining the components of a composition of the invention as described above; (ii) placing an intermediate layer of the composition from step (i) on one member of the restorative material/substrate pair; (iii) optionally curing the intermediate layer; and (iv) adhering the other member of the restorative material/substrate pair to the first member by way of the intermediate layer. DETAILED DESCRIPTION OF THE INVENTION Materials suitable for use as the ethylenically unsaturated compound in a composition of the invention include such materials known to those skilled in the art to be capable of bonding to hard tissue such as dentin, enamel, bone, or the like. This compound is a monomer, oligomer, or polymer (or mixture thereof) , preferably suitable for use in the oral environment both in its unpolymerized and polymerized state. Both phosphorylated and phosphorus-free ethylenically unsaturated compounds as well as mixtures thereof are suitable. Suitable phosphorus-free ethylenically unsaturated compounds include mono- or poly- (e.g., di-, tri- or tetra- unctional) acrylates and methacrylates such as methyl acrylate, 2-hydroxyethyl acrylate, triethylene- glycol diacrylate, neopentylglycol diacrylate, hexamethyleneglycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyalkylene glycol mono- and di-acrylates, urethane mono- or poly-functional acrylates, Bisphenol A diacrylates, and the corresponding methacrylates of the above compounds, as well as acrylamides and methacrylamides, vinyl compounds, styrene compounds, and other olefinically unsaturated compounds suitable for use in the oral environment. U.S. Pat. Nos. 4,499,251, 4,515,930, 4,537,940 and 4,539,382 contain an extensive list of such compounds. Representative phosphorus-free ethylenically unsaturated dental adhesives include "SCOTCHBOND 2™" Dental Adhesive (3M) , "CONCISE™" Enamel Bond (3M) , "TENURE™" Solution Dentin Bonding System (Den-Mat Corp.), "GLUMA™" Bonding System (Columbus Dental Miles, Inc.) and "MIRAGE-BOND™" Dentin-Enamel Bonding System (Chameleon Dental Products, Inc., see U.S. Pat. Nos. 4,514,527, 4,521,550, 4,588,756, and 4,659,751) . Suitable ethylenically unsaturated phosphorylated compounds comprise one or more phosphorus atoms bonded through a carbon, nitrogen, oxygen, or sulfur atom to a radical containing one or more ethylenically unsaturated groups. Preferred ethylenically unsaturated groups are ethenyl and 2-propenyl as found, respectively, in acrylate and methacrylate groups. One or more of the phosphorus atoms can be bonded to one or more halogen atoms, active hydrogen atoms, or substituted or unsubstituted hydrocarbyl groups (e.g., an alkyl, aryl, alkaryl, or aryalkyl group) . A particular class of suitable phosphorylated compounds is described in European Patent Application No. 0 058 483 and U.S. Pat. No. 4,515,930. These phosphorylated compounds include those comprising an organic ester of one or more acids of phosphorus, the organic radical of said ester containing at least one ethylenically unsaturated group, wherein said ester has chlorine or bromine bonded directly to the phosphorus (hereinafter "halophosphorus acid esters"). A preferred subclass of such halophosphorus acid esters includes halophosphorus acid esters of diglycidyl methacrylate of Bisphenol A ("Bis-GMA") prepared by reacting Bis-GMA with a phosphorus acid halide. Phosphorus acid halides (e.g., chlorides, bromides) that can be reacted with Bis-GMA include P0C1 3 , PC1 3 , PBr 3 , R'0P(0)C1 2 , (R'0) 2 P(0)C1 where R' is a hydrocarbyl radical, preferably one derived from removal of one or more hydroxyl groups from a hydroxyl-containing compound such as 2-hydroxyethyl methacrylate, ethylene glycol, polyethylene glycol, pentaerythritol, and the like, as would result from a reaction of the hydroxyl-containing compound and the phosphorus acid halide. A particularly preferred class of phosphorylated compounds includes chlorophosphorus acid esters of Bis-GMA. An additional suitable class of phosphorylated compounds includes the phosphorus acid esters described in U.S. Pat. Nos. 3,882,600, 3,997,504, 4,222,780, 4,235,633, 4,259,075, 4,259,117, 4,368,043, 4,442,239, 4,499,251, 4,514,342, 4,537,940, 4,539,382 and Japanese published patent application (Koho) No. 85-17235. Exemplary members of this class are the compounds 2-methacryloyloxyethyl phenyl phosphate and 10-methacryloyloxydecyl dihydrogen phosphate. A further suitable class of phosphorylated compounds includes the pyrophosphate ester derivatives described in U.S. Pat. Nos. 4,383,052 and 4,404,150 and in Japanese Kokai 57-143372 and 57-167364. Glycerophosphate dimethacrylate, described in the above-mentioned Buonocore, ileman, and Brudevold publication is also suitable. Other dental adhesives suitable for use as the ethylenically unsaturated compound include those that contain phosphorylated compounds and/or acrylate- or methacrylate-functional polymers. In such dental adhesives either a single phosphorylated compound or a mixture of phosphorylated compounds can be used. Suitable dental adhesives include "SCOTCHBOND™" Dual Cure Dental Adhesive (3M) , "ALL-B0ND2™" Universal Dental Adhesive System (Bisco, Inc.), "CLEARFIL™" Photo Bond Light-Cured Dental Bonding Agent (Kuraray Co., Ltd.), "RESTOBOND 3™" Dual Dentin/Enamel Bonding Agent (Lee Pharmaceuticals, see U.S. Pat. Nos. 4,524,527 and 4,521,550), "PRISMA UNIVERSAL B0ND3™" Dentin/Enamel Bonding Agent (L. D. Caulk Division of Dentsply International, Inc., see U.S. Pat. No. 4,814,423), "BONDLITE™" Dental Adhesive (Sybron Corp.), "Johnson & Johnson" Dentin Bonding Agent and "Johnson & Johnson" Light-Curing Bonding Agent (Johnson & Johnson Co.), "PALFIQUE™" Bonding Agent (Tokuyama Soda Co., Ltd.), "SHOFU™" Bonding Base (Shofu, Inc.), and "SINTERBOND™" Dental Adhesive (Teledyne Getz) . In embodiments involving a mixture of ethylenically unsaturated compounds, suitable relative amounts of each compound can be easily selected by those skilled in the art. The compositions of the invention also comprise a particulate metallic filler that does not interfere with the cure of the ethylenically unsaturated compound. Particular suitable metallic fillers can be selected by those skilled in the art based on chemical compatibility with the particular ethylenically unsaturated compound and the particular polymerization initiator present in the composition. Interference with the cure of the ethylenically unsaturated compound can also be determined empirically, e.g., by adding a selected metallic filler to a mixture of ethylenically unsaturated compound and polymerization initiator, which mixture cures in a satisfactory manner absent the metallic filler. When cure of the metal-containing mixture is attempted, any interference with cure due to the metallic filler will be readily observable. Depending on the identity of the ethylenically unsaturated compound and the polymerization initiator, the filler can be a pure metal such as those of Groups IVA, VA, VIA, VIIA, VIII, IB, or IIB, aluminum, indium, and thallium of Group IIIB, and tin and lead of Group IVB, or alloys thereof. Conventional dental amalgam alloy powders, typically mixtures of silver, tin, copper, and zinc, are also suitable. The particulate metallic filler preferably has an average particle size of about 1 micron to about 100 microns, more preferably 1 micron to about 50 microns. In some embodiments, the metallic filler is present in an amount effective to increase adhesion of amalgam to tooth structure when the composition is used as an intermediate layer between the tooth structure and the amalgam, compared to the adhesion obtained using a like composition absent the metallic filler. An effective amount in these embodiments can be determined according to the method set forth in the EXAMPLES that follow. In other embodiments the particulate metallic filler is present in an amount of 50 to about 4000 parts by weight, preferably about 200 to about 3000 parts by weight based on 100 parts by weight of the ethylenically unsaturated compound. A composition of the invention also includes a polymerization initiator in an amount sufficient to effect cure of the composition. Suitable polymerization initiators include autocure and light cure polymerization initiators such as those mentioned in columns 28 and 29 of U.S. Pat. No. 4,539,382, chromophore-substituted halomethyl-s-triazines such as those shown in U.S. Pat. No. 3,954,475, and chromophore-substituted halomethyl-oxadiazoles such as those shown in U.S. Pat. No. 4,212,970. The polymerization initiator is preferably present in an amount of about 0.01 to about 20 parts by weight, more preferably about 0.1 to about 10 parts by weight, based on 100 parts by weight of ethylenically unsaturated compound. Other compounds (additional to the above-discussed ethylenically unsaturated compound) can be incorporated in the compositions of the invention in appropriate amounts easily selected by those skilled in the art to provide desired properties. Suitable compounds include mono- or polyacrylates and methacrylates such as methyl acrylate, 2-hydroxyethyl acrylate, triethyleneglycol diacrylate, neopentylglycol diacrylate, hexamethyl- eneglycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, polyalkylene glycol mono- and di-acrylates, urethane mono- or polyfunctional acrylates, Bisphenol A diacrylates, and the corresponding methacrylates of the above compounds, as well as acrylamides and methacrylamides, vinyl compounds, styrene compounds, and other olefinically unsaturated compounds suitable for use in the oral environment. U.S. Pat. Nos. 4,499,251, 4,515,930, 4,537,940 and 4,539,382 contain lists of such compounds. The compositions of the invention can also contain conventional adjuvants such as accelerators, inhibitors, stabilizers, pigments, dyes, viscosity modifiers, extending or reinforcing fillers, surface tension depressants, wetting aids, antioxidants, and other ingredients known to those skilled in the art. The compositions of the invention can be prepared by mixing and packaging the various components according to methods well known to those skilled in the art. For example, when a redox type curing agent is used, an appropriate package form keeps the oxidant and the reducing agent apart from each other in order to ensure storage stability of the composition. Examples of package forms include two-part packages of (a) an ethylenically unsaturated compound, a metallic filler, and a reducing agent in one part and (b) an ethylenically unsaturated compound and an oxidant in the other. In the case of an organic sulfinic acid (or salt thereof)/amine (or salt thereof)/peroxide ternary system, it is also possible to use a three-part package form in which the sulfinic acid and the amine are packaged separately. Where the polymerization initiator comprises a photoinitiator, an ethylenically unsaturated compound and a photoinitiator are preferably packaged separately or in a container opaque to light. With a thermal initiator that initiates polymerization when it is brought into contact with the ethylenically unsaturated compound (e.g., tributylborane) , the ethylenically unsaturated compound and the initiator are packaged separately. Such separately packaged components are mixed together shortly before use. A composition of the invention can be used as an intermediate layer between a substrate such as hard tissue (e.g., bone, enamel, or dentin) or ceramic, and a restorative material such as a pure metal or alloy, an amalgam, a ceramic composite, or a composite comprising an adhesive polymer (or a mixture of polymers) and a particulate filler. A primer may be used, but good adhesion is obtained without the use of auxiliary primers. The compositions of the invention generally provide better adhesion than is obtained using the ethylenically unsaturated compound alone. In order to adhere a restorative material to a substrate, the components of a composition of the invention are first combined in appropriate amounts. As discussed above, depending upon the particular type of curing agent used the components can be mixed prior to packaging or they can be packaged as two- or three-part systems and combined just prior to use. Once the components are combined the resulting composition of the invention can be placed in the form of a thin layer (e.g., by brushing) on either the restorative material or on the substrate. The layer can then optionally be cured by appropriate means (e.g., heat including exposure to room temperature, visible light, ultraviolet light, or the like) . The other member of the restorative material/substrate pair can then be prepared (e.g., mixed) if necessary and placed on the adhesive layer. For the reasons set forth above in connection with the Background of the Invention, it is desirable if an amalgam can be made to adhere well to tooth structure. Accordingly, one use of the compositions of the invention involves adhering dental amalgam to tooth structure in a prepared cavity. It is preferred to use a modified amalgam in order to optimize adhesion to tooth structure. Such a modified amalgam can be produced by admixing particulate additives into conventional amalgam alloy powder. The modified amalgam is then prepared in a conventional manner by triturating the modified alloy powder with mercury in an amalgamator. The preferred particulate additives are selected from the following groups: 1) acrylate- or methacrylate-functional polymers, 2) metal salts of acrylates or methacrylates, 3) nonmetallic fillers, 4) oxidizing agents, and 5) reducing agents. The particulate additives are applicable to the full range of conventional amalgam alloy powders and conventional weight ratios of mercury to amalgam alloy powder. Representative acrylate- or methacrylate- functional polymers include poly(alkanoic acid) powder. Representative metal salts of acrylates or methacrylates include zinc dimethacrylate, zirconium dimethacrylate, silver methacrylate, sodium methacrylate, and magnesium methacrylate. Nonmetallic fillers include both untreated organic fillers and surface-treated fillers. Representative nonmetallic fillers, also known as organic fillers, include blends of silane-treated OX-50™ pyrogenic silica (Degussa Company) , tetraethyleneglycol dimethacrylate ("TEGDMA") (Rohm Tech Co.), and Bisphenol A diglycidylether dimethacrylate in a 60:17:17 weight ratio. Other representative nonmetallic fillers include zirconia/silica filler either untreated or pretreated with gamma-methacryloxypropyl trimethoxysilane as described in U.S. Pat. No. 4,503,169. Preferred oxidizing agents include benzoyl peroxide. Preferred reducing agents include sodium benzenesulfinate. Adhesion of amalgam to etched enamel was evaluated as follows: Bovine teeth of similar age and appearance were partially embedded in circular acrylic disks such that the enamel was exposed. The exposed portion of each tooth was ground flat and parallel to the acrylic disc using Grade 120 silicon carbide paper-backed abrasive mounted on a lapidary wheel. Further grinding and polishing of the teeth was carried out by mounting Grade 320 silicon carbide paper-backed abrasive on the lapidary wheel. During the grinding and polishing steps, the teeth were continuously rinsed with water. The polished teeth were stored in distilled water and used for testing within 2 hours after polishing. The polished teeth were removed from the water and dried using a stream of compressed air. Phosphoric acid etching gel was applied to the enamel for 15 seconds, rinsed with water, and dried. The adhesive composition was applied to the entire enamel surface with a brush and blown into a thin film with compressed air and cured according to manufacturer's instructions. A mold made from a 2 mm thick TEFLON™ polytetra- fluoroethylene sheet with a 5 mm diameter circular hole through the sheet was clamped to each polished tooth so that the central axis of the hole in the mold was normal to the polished tooth surface. The hole in each mold was filled with a prepared amalgam and allowed to stand for about 15 minutes at room temperature, then stored in distilled water at 37°C for 24 hours. The molds were then carefully removed, leaving a molded button of amalgam attached to each tooth. Adhesive strength was evaluated by mounting the acrylic disk in a holder clamped in the jaws of an INSTRON™ tensile testing apparatus with the polished tooth surface oriented parallel to the direction of pull. A loop of orthodontic wire (0.44 mm diameter) was placed around the base of the amalgam button adjacent to the polished tooth surface. The ends of the orthodontic wire were clamped in the pulling jaw of the tensile testing apparatus, placing the bond in shear stress. The bond was stressed until it (or amalgam button) failed, using a crosshead speed of 2 mm/min. The following examples are offered to aid in understanding of the present invention and are not to be construed as limiting the scope thereof. Unless otherwise indicated, all parts and percentages are by weight. EXAMPLES 1-12 and COMPARATIVE EXAMPLES C-l to C-6 Using the procedure set forth above, the adhesive shear bond strength on etched enamel of several adhesive compositions was evaluated. The amalgam used was two-spill capsules of DISPERSALLOY™ amalgam. Commercially available adhesives were evaluated according to the manufacturer's instructions. Compositions of this invention were prepared by preweighing the metal additive into a mixing well. One drop (approximately 0.03 g) of a phosphorylated ethylenically unsaturated compound (SCOTCHBOND™ Dual Cure Dental Adhesive resin) and one drop (approximately 0.02 g) of a polymerization initiator (SCOTCHBOND™ Dual Cure Dental Adhesive liquid) were added to the metal additive. Alternatively a composition comprising a phosphorus-free ethylenically unsaturated compound was prepared by preweighing the metal additive into a mixing well and adding one drop each of: (i) a combination of a phosphorus-free ethylenically unsaturated compound and dihydroxyethyl-p-toluidine reducing agent (CONCISE™ Enamel Bond A) ; and (ii) a combination of a phosphorus-free ethylenically unsaturated compound and benzoyl peroxide oxidizing agent (CONCISE™ Enamel Bond B) . In each case the components were then mixed rapidly and applied with a brush to the etched enamel. The applied adhesive was then cured according to manufacturer's instructions prior to placement of the amalgam. Set out below in TABLE I are the example numbers, ethylenically unsaturated compound, metallic filler, and mean adhesive shear bond values for the various compositions tested. 1 SCOTCHBOND™ Dual Cure Dental Adhesive 2 AMALGAMBOND™ Dental Adhesive 3 PANAVIA™ Dental Adhesive 4 SUPERBOND™ Adhesive 5 CONCISE™ Enamel Bond The results in TABLE I illustrate that the exemplified compositions comprising a metallic filler and an ethylenically unsaturated compound provide improved shear adhesion to hard tissue and amalgam relative to the unfilled ethylenically unsaturated compound. Several compositions of this invention provided mean shear adhesion values better than those obtained with commercially available hard tissue/amalgam adhesives. Also, it was observed in Comparative Example C-6 that zinc interferes with the cure of the SCOTCHBOND™ Dual Cure Dental Adhesive resin when SCOTCHBOND™ Dual Cure Dental Adhesive liquid was used as the polymerization initiator. EXAMPLES 13-14 and COMPARATIVE EXAMPLES C-7 to C-ll Using the procedure set forth above, the shear adhesive bond strength on etched enamel of several adhesive compositions was evaluated. The amalgam used was two-spill capsules of DISPERSALLOY™ amalgam (Johnson and Johnson) or a modified version containing varying amounts of organic filler. Set out below in TABLE II are the example numbers, ethylenically unsaturated compound, metallic filler, amalgam, amalgam additive, and mean shear adhesion values for the various compositions tested. TABLE II ADHESION OF AMALGAM OR MODIFIED AMALGAM TO ETCHED ENAMEL 'SCOTCHBOND™ Dual Cure Dental Adhesive. 2 AMALGAMBOND™ Dental Adhesive. 3 PANAVIA™ Dental Adhesive. "SUPERBOND™ Adhesive. Containing 17 wt. % TEGDMA, 17 wt. % Bis-GMA, and 66 wt. % M OX-50" pyrogenic silica that had been treated with 20 wt. % gamma-methacryloxypropyl trimethoxysilane. The results in TABLE II show that the greatest mean adhesive shear bond values are obtained for the combination of metal filled adhesive and powder modified amalgam.

Claims: CLAIMS : 1. An adhesive composition, comprising: (i) an ethylenically unsaturated compound; (ii) a particulate metallic filler that does not interfere with the cure of the ethylenically unsaturated compound, in an amount effective to increase adhesion of amalgam to tooth structure when the composition is used as an intermediate layer between the amalgam and the tooth structure, compared to the adhesion obtained using a like composition absent the particulate metallic filler; and (iii) a curing agent in an amount sufficient to effect cure of the composition. 2. A composition according to Claim 1, wherein the ethylenically unsaturated compound comprises a phosphorylated compound. 3. A composition according to Claim 2, wherein the phosphorylated compound comprises a chlorophosphorus acid ester of Bis-GMA. 4. A composition according to Claim 1, wherein the ethylenically unsaturated compound comprises a phosphorous-free compound. 5. A composition according to Claim 1, wherein the ethylenically unsaturated compound comprises a mixture of at least one phosphorylated compound and at least one phosphorous-free compound. 6. A composition according to Claim 1, wherein the particulate metallic filler has an average particle size of about 1 micron to about 100 microns. 7. A composition according to Claim 1, wherein the particulate metallic filler has an average particle size of about 1 micron to about 50 microns. 8. A composition according to Claim 1, wherein the particulate metallic filler is a dental amalgam alloy powder. 9. A method of adhering a restorative material to a substrate, comprising the steps of: (i) combining the components of a composition according to Claim 1; (ii) placing an intermediate layer of the composition from step (i) on one member of the restorative material/substrate pair; (iii) optionally curing the intermediate layer; and (iv) adhering the other member of the restorative material/substrate pair to the first member by way of the intermediate layer.

Inventors: FUNDINGSLAND JON W, OXMAN JOEL D, FUNDINGSLAND, JON, W., OXMAN, JOEL, D.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1992
Main classification: C09J4
IPC codes: A61K6, C09J4