NOVEL DENTAL ADHESIVE

Abstract: A single package adhesive for tooth bonding application comprising a solvent-based homogenous mixture of: 1) an ethylenically unsaturated functional and hygroscopically functional monomer; 2) an ethylenically unsaturated functional and hygroscopically functional coupling agent that is capable of (a) chemically reacting with and through the ethylenic bond of the ethylenically unsaturated functional monomer of 1) above, and (b) chemically bonding to the surface to which the adhesive is applied; 3) a poly-ethylenically unsaturated functional crosslinking agent that is capable of reacting with the monomer of 1) above and the coupling agent of 2) above; and 4) a photoinitiator that induces addition polymerization of an ethylenically unsaturated compound. A method for forming a composite and composite structure are included that employ the single package adhesive.

Description: Novel Dental Adhesive Brief Description Of The Invention A single package adhesive for tooth bonding appli- cation comprising a solvent-based homogeneous mixture of — 1) an ethylenically unsaturated functional and hy¬ groscopically functional monomer; 2) an ethylenically unsaturated functional and hy- groscopically functional coupling agent; 3) a poly-ethylenically unsaturated functional crosslinker (cross linking agent) ; and 4) a photoinitiator. Composite formation by adhesively interbonding with tooth components using this single package adhe¬ sive. Background To The Invention Geristore™ and Tenure™, sold by Den-Mat Corpora¬ tion, Santa Maria, CA, are promoted for certain uses in dentistry. U.S. Patents Nos. 4,738,722, 5,334,625 and 5,151,453, incorporated herein by reference, describe Geristore™. Geristore™ is a small particle composite that contains fluoride, is radiopaque and hydrophilic. It has low-cure shrinkage, low coefficient of thermal expansion and high strength. It aggressively bonds by chemical coupling to dentin, enamel, composites used in dentistry, porcelain and metal, such as stainless steel. It is a paste/paste formulation that is easy to mix. It is capable of rapid cure by exposure to room temperature and for more rapid cure, by exposure to light. In addition, though it contains a fluoride, which could be toxic when ingested in large dosages, it is biocompatible and safe to use within a human or other animal when applied topically. Tenure™ is a solvent-based crossiinkable acrylic resin, provided as a solution/solution formulation, that is, a two package system. Its composition is de¬ scribed in U.S. Patent No. 4,964,911, patented October 27, 1990, and more effectively disclosed in U.S. Patent Re. 34,937, patented May 16, 1995, the disclosure of which is incorporated by reference. It is not an iono¬ mer and does not release fluoride ion. It is less hy¬ drophilic than Geristore™. It, too, is a crossiinkable resin. It contains a volatile solvent (typically ace¬ tone), which readily evaporates. After evaporation, a film of the resin rapidly cures in situ. The film is light and/or heat cured to a thermoset condition. Ten¬ ure™ bonds by chemical coupling to dentin, enamel, por¬ celain, metal and the composites typically used in den¬ tistry. It has been recommended for use with Geris- tore™ in chemically bonding Geristore™ to dentin or enamel . Bisco Inc., 1500 . Thordal Ave. , Itasca, IL, 60143, sells a "one-step" adhesive bonding acrylic resin system called "Uni-Bond" that uses a single solu- tion to form the adhesive resin film. It is cited by the seller to yield the following physical data in bonding to certain substrates: Substrates SBS, MPa Dentin (using etchant) 27.3 (0.6) Enamel (using etchant) 30.4 (3.8) Metals : Gold Alloy 20.6 (5.0) Rexillium III (Ni-Cr) 25.5 (2.3) Stainless Steel (316) 29.2 (1.7) Set Amalgam (Tytin®) 13.6 (1.5) There is a need for an adhesive composition with the properties of Tenure® that is designed to be used from a single package of ingredients. The Invention This invention relates to a single package adhesive for tooth bonding application comprising a solvent-based homogeneous mixture of — 1) An ethylenically unsaturated functional and hy¬ groscopically functional monomer. In other words, this monomer contains ethylenic unsatura¬ tion such that it co-reacts by addition polymeri¬ zation with the coupling agent, infra, and the crosslinking agent, infra. In addition, this monomer possesses a hygroscopic group that con- tributes to the properties of the adhesive. 2) An ethylenically unsaturated functional and hy¬ groscopically functional coupling agent. This coupling agent is capable of (a) chemically re¬ acting with and through the ethylenic bond of the ethylenically unsaturated-functional monomer of 1) above and (b) chemically bonding to the sur¬ face to which the adhesive is applied. For exam¬ ple, the coupling agent may be an acrylic-type monomer that possesses acrylic-type unsaturation and contains a surface bonding group, such as, one or more of the following groups: i) an alkylene poly¬ vii)phosphinyl ether; viii) stannoyl ii) hydroxyl ix) amide iii) carboxylic acid x) alkylene salt amine iv) quaternary ammo¬ xi) alkoxysilyl nium xii) acyloxysilyl v) tertiary amine vi)phosphoryl 3) A poly-ethylenically unsaturated functional crosslinker (cross linking agent) that is capable of reacting with the monomer of 1) above and the coupling agent of 2) above. In other words, the crosslinker (cross linking agent) is a polyfunc¬ tional molecule where the functionality is com¬ plementary to the ethylenic unsaturation of the ethylenically unsaturated functional monomer of 1) above and the coupling agent of 2) above. 4) a photoinitiator, i.e., a free radical photoini¬ tiator that induces addition polymerization of an ethylenically unsaturated compound. It was not predictable, and hence was unexpected, that the above solution, particularly as described herein, could be used as a replacement for the multi- package adhesive of U.S. Patent Re. 34,937. The single solution adhesive of this invention yields adhesive properties competitive with the multi-packaged adhe¬ sives described in U.S. Patent Re. 34,937. In characterizing the invention, reference is made to the fact that the adhesive is employed in tooth bonding. The term tooth bonding is intended to mean all of the various bonding applications used in the care, correction, restoration and/or repair of teeth and other oral surfaces, including bonding of and/or between enamel, dentin, bone, gum, porcelain, metal (gold, titanium, and the like), amalgam, plastic (e.g., the acrylics), and the like. An important facet of this invention is that the components of the formulation are sufficiently compati¬ ble with each other and the solvent of choice. This means that the combination of the ingredients used in making the invention form a stable homogeneous mixture, i. e., they form a stable solution that can be stored for an extended period of time. It is preferred in the practice of the invention that all of the components of the formulation remain in solution at ambient condi- tions for months, without precipitation of any compo¬ nent. However, it is within the contemplation of this invention that one or more of the ingredients of the formulation may precipitate from the solution on stand¬ ing. In those instances, the precipitate is a soft deposit that is readily redissolved by stirring. The solvent may be an aqueous-containing organic solvent. In addition, the invention relates to compos¬ ite formation by adhesively interbonding with tooth components . The inventive adhesive comprises a resin based on an ethylenically unsaturated-functional monomer that contains a hygroscopic group and exhibits hydrophilic¬ ity. Typical of such groups are hydroxyl, amide, amine, aliphatic ether, amine, hydroxyalkyl amine, hy- droxyalkyl amide, pyrrolidone, ureyl, and the like. Another feature of the inventive adhesive is that it tenaciously bonds to- surfaces onto which it is coated as well as securely tie up any inorganic filler that is included in its formulation. This is accom¬ plished by the presence of a coupling agent in the ad¬ hesive formulation of the invention. The coupling agent provides chemical bonding to the surface to which the adhesive is applied. Chemical bonding means strong and weak bonding forces. Strong bonding forces, as used herein, refers to covalent, ionic, hydrogen bond¬ ing and complexation, and weak bonding forces, encom¬ passes the other forms of bonding. Where weak bonding forces are employed, the extent of such bonding is such that the adhesion to the surface is of the nature of a stronger bonding force. For example, van der Waal forces are weak bonding forces. In the case of the in¬ vention, the amount of such forces existing between the adhesive and the surface will be sufficient to give the performance of a stronger bonding force. A desirable coupling agent is a compound, such as monomer, adduct or polymer, that is functionally com¬ plementary to the ethylenically unsaturated functional monomer. Desirably, the coupling agent contains a functional group that is complementary with the eth¬ ylenic unsaturation of the ethylenically unsaturated functional monomer. Preferably, the functional group is an acrylic-type ethylenic unsaturation. At another part of the coupling agent molecule is a surface bond¬ ing group that can impart one or more properties to the adhesive coating: 1) chemical bonding capabilities to the substrate surface to which the adhesive coating is applied; and/or 2) wetting agent properties, that is, reduce the surface tension of the adhesive coating, causing the coating to spread across or penetrate more easily the substrate surface onto which the adhe¬ sive coating is applied. In addition, the adhesive of the invention con¬ tains at least one crosslinking agent. The crosslinking agent is a polyfunctional molecule where the function¬ ality is complementary to the ethylenic unsaturation of the ethylenically unsaturated functional monomer and the functional group of the coupling agent. In one aspect, the functional groups of the crosslinking agent are bonded via aliphatic groups, each of up to 10 car¬ bon atoms, to a central organic moiety that is aromatic in nature, that is, comprises a group that has the ri¬ gidity characteristics of a benzene ring. Illustrative of such rigid groups are aromatic rings such as ben- zene, biphenyl, anthracyl, benzophenone, norbomyl, and the like. Such crosslinkers raise the Tg of the cured coating. In the case of such crosslinkers, it is de¬ sirable that they contain carboxylic acid alkali metal (Li, Na, K, Ru or Cs) salt groups directly bonded to a carbon atom of the rigid ring. Such salt forms enhance the solubility of the crosslinker in the solvent. Preferably, in another aspect, the functional groups of the crosslinking agent are bonded to a central moiety that is aliphatic in nature, that is, comprises a group that has the flexibility of an alkane or an alkyl ben¬ zene containing compound. Illustrative of such flexi¬ ble groups are the residues of ethylene glycol, dieth¬ ylene glycol, 2,2-bis (4-hydroxyphenyl) propane, 2,2,- bis (4-hydroxyphenyl) fluoroalkanes, and the like. Such softer crosslinkers toughen the cured coating and can raise the Tg of the cured coating, but not as high as the other more rigid crosslinking agents. Mixtures of such crosslinking agents .can be employed in the prac¬ tice of the invention. For example, mixtures of such crosslinking agents where one is employed in amount by weight greater than the other are within the contempla¬ tion of this invention, as is a mixture of equal amounts by weight of the different crosslinking agents. In the case of such mixtures, one of the crosslinking agents may be used in amount of from about 1 weight percent of the weight of the crosslinking agent compo¬ nent of the adhesive formulation of the invention to about 99 weight percent of the weight of the crosslink- ing agent component of the adhesive formulation of the invention. In order to cure the adhesive of the invention, its formulation is provided with a conventional free- radical photoinitiator. The invention also contem- plates, as an optional feature, the use of free radical scavengers in the formulation. A primary advantage of the invention is that the adhesive composition is a homogeneous liquid single- package system. This means that the adhesive composi- tion is a solution that can be stored in and used from a single container, such as a metal, glass or plastic container. Quite surprisingly, the adhesive of the in¬ vention yields adhesive performance similar to the Ten¬ ure® multi-package system adhesive, described in U.S. Patent Re. 34, 937. In particular, the invention relates to the im¬ provement where the adhesive composition is a homogene¬ ous liquid single-package system comprising: 1) an ethylenically unsaturated functional monomer, such as 2-hydroxyethyl-methacrylate, 2,3- dihydoxypropylmethacrylate, and the like; 2) a coupling agent, such as one or more of the al¬ kali metal salt of (i) N-phenylglycine, (ii) the adduct of N- (p-tolyl) glycine and glycidyl meth¬ acrylate, and (iii) the adduct of N-phenylglycine and glycidyl methacrylate; 3) a crosslinker (cross linking agent) such as 2,2- bis (4-methacryloxy 2-ethoxy- phenyl) propane, di¬ ethyleneglycol bismethacrylate, the alkali metal salts of 4, ' -bis (4-methacryloxy-2-ethoxy 3- carboxy) biphenyl (salt of the reaction product of 2-hydroxyethylmethacrylate and sym.- tetracarboxylic dianhydride) , the alkali metal salts of the reaction product of 2- hydroxyethylmethacrylate and pyromellitic anhy¬ dride, the alkali metal salt of the reaction product of 2-hydroxyethylmethacrylate and 3, 3' , 4, 4' -bensophenonetetracarboxylic anhydride, the alkali metal salt of the reaction product of 2-hydroxyethylmethacrylate and trimellitic anhy¬ dride, and the like, in which the alkali metals are one or more of Li, Na, K, Ru and Cs; 4) a photoinitiator; 5) a water soluble organic solvent such as acetone; and 6) water. In the preferred embodiment of the invention, the adhesive formulation is a solution comprising: a) 2-Hydroxyethylmethacrylate b) The alkali metal salt of the adduct of N- (p- tolyl) glycine and glycidyl methacrylate; e.g., the structure: where Y is an alkali metal such as Li, Na, K, Ru and Cs . Preferably, Y is sodium or potassium. c) Ethoxylated bisphenol A dimethacrylate, i. e., 2, 2-bis (4-methacryloxy 2-ethoxy- phenyl) propane; and d) A photoinitiator such as ethyl 4-dimethylamino benzoate and camphoquinone (i.e., 2,3- bornanedione) ; e) acetone-water solvent mixture, most desirably in about a 4/1 weight ratio. The adhesive composition of the invention is used to form a composite structure, and involves, in one preferred embodiment, the steps of — (a) Optionally, contacting the adherend surface with an aqueous etching or conditioning solution com¬ prising at least one strong acid or acidic salt in order to condition the surface, followed by rinsing and drying the surface. (b)coat the surface with a solution comprising: 1) an ethylenically unsaturated functional mono¬ mer; 2) a coupling agent; 3) a crosslinker (cross linking agent); 4) a photoinitiator; (c)cure the coating with light; (d) apply a compositing material to the coating; and (e)cure the compositing material in contact with the coating. The composite comprising the cured single package adhesive described above bonded to another sur¬ face, such as a portion of a tooth and/or a prosthetic device. The portion may be dentin, enamel or any tra¬ ditional prosthetic device material such as metal (titanium, gold, stainless steel, and the like) , porce- lain, acrylic plastic, and the like. Detail Description Of The Invention The adhesive coating based on the adhesive formu¬ lation of the invention is typically a crosslinked light set resin that contains hygroscopic groups that attract water to the coating. When the crosslinking is not too extensive, the adhesive coating can absorb enough water to cause it to swell. The amount of water that the adhesive coating can absorb can be as high as 25 weight percent. However, the degree of crosslinking of the adhesive coating is typically high enough that water absorption will not exceed about 5 weight per¬ cent. The backbone of the polymer providing the hygro¬ scopic groups of the resin phase of the adhesive coat¬ ing is typically aliphatic and may contain groups therein that enhance the hydrophilicity of the resin phase. The adhesive coating's resin is typically the in situ reaction product of one or more of a polymeriz¬ able ethylenically unsaturated organic monomer contain¬ ing groups that are attractive to water. Thus the co - ponents of the adhesive formulation may be — (a) an ethylenically unsaturated functional mono¬ mer that contains a hygroscopic group. Typical of such groups are hydroxyl, amide, amine, aliphatic ether, amine, hydroxyalkyl amine, hydroxyalkyl amide, pyr¬ rolidone, ureyl, and the like. Illustrative of such monomers are the following: A particularly desirable ethylenically unsaturated- functional monomer is an acrylic-type monomer having the following structure: wherein R' and R", individually, are hydrogen, alkyl of 1 to about 4 carbon atoms, monocyclic aryl, such as phenyl, alkyl phenyl where the alkyl is 1 to about 3 carbon atoms, cyclohexyl, and the like; R2 is hydrogen, alkyl of 1 to about 3 carbon atoms, and the like; X is 0, S and N-R3, where R3 is hydrogen, alkyl of 1 to about 4 carbon atoms, -Rl-Y, and the like; Rl is a di¬ valent radical connecting Y to X, and may be one of the following: -CH 2 - -CH 2 CHR 4 - -CΓ CΓ CΓ " OH -CH 2 CHCH 2 - -CH 2 CHR 4 OCH 2 CHR 4 - wherein each R4 is hydrogen or alkyl of 1 to about 3 carbon atoms; and Y is OH, NR5, SH, OR6, where R5 is hydrogen, methylol, methylol methyl ether, R6 is alkyl of 1 to about 3 carbon atoms provided that Rl is -CH2-, and the like; q is 0 or 1 and p is 0 or 1, and p is 0 when q is 1 and 1 when q is 0; and Z is hydrogen. A particularly desirable thermosetting adhesive coating is based on 2-hydroxyethyl methylmethacrylate ("HEMA"), 2-hydroxyethyl acrylate, 2, 3-dihydroxypropyl methacrylate, acrylamide, methacrylamide, hydroxyalkyl acrylamide, hydroxyalkyl methacrylamide, and the like materials co-reacted with the coupling agent and the crosslinking agent. (b) A desirable coupling agent is an acrylic-type monomer that possesses acrylic-type unsaturation and contains a surface bonding group possessing one or more of the following groups: 1) an alkylene poly¬ 7) phosphinyl ether; 8) stannoyl 2) hydroxyl 9) amide 3) carboxylic acid 10) alkylene amine salt 11) alkoxysilyl 4) quaternary ammonium 12) acyloxysilyl 5) tertiary amine 6) phosphoryl A preferred coupling agent is a simple aromatic substituted amino acid alkali metal salt such as the alkali metal salt of (i) N-phenylglycine, (ii) the ad¬ duct of N- (p-tolyl) glycine and glycidyl methacrylate, which is illustrated by the structure: where Y is one of the alkali metals, i.e., lithium, so¬ dium, potassium, rubidium and cesium, preferably sodium or potassium, and (iii) the adduct of N-phenylglycine and glycidyl methacrylate, which is illustrated by the structure: where Y is described above; or the mixture of the pre¬ ceding two compounds, alone or in combination with a compound containing at least one group or moiety capa¬ ble of free radical polymerization and at least one aromatic ring or moiety containing one or more elec¬ tron-withdrawing carboxylic acid alkali metal salt sub¬ stituents that do not interfere with free radical po- lymerization. Additional examples of coupling agents are the al¬ kali metal salts of a carboxylic acid containing at least one amino group. This includes the alkali metal salts or esters of the amino acids in general, such as N-phenylglycine, N- (p-tolyl) glycine, N-phenylalanine, sarkosine, N-lauroylsarkosine, glycine, N,N- dimethylglycine, 3- (N-phenyl) aminopropionic acid, 3-(N- p-tolyl) amino propionic acid, omega-amino fatty acids, N-substituted-omega-amino fatty acids, the addition re- action product of N-phenyl glycine and glycidyl rea¬ gents, and the reaction product of N- (substituted phenyl) glycine and glycidyl reagents. It is antici¬ pated that the alkali-metal salts of many or all of these compounds would be effective to one degree or an¬ other. These coupling agents interreact with the polym¬ erization of the aforementioned ethylenically unsatu- rated-functional monomer that contains a hygroscopic group, and enhance wetting and bonding by the resulting resin of proteinaceous surfaces by surface interaction with the carboxylic acid salt group of the coupling agent. (c) A number of acrylic coating resins rely on polyacrylyl substituted monomers to crosslink and chain extend the polymer that comes into existence on polym- erization in the presence of an polymerization initia¬ tor. For example, the pure forms of HEMA typically contain small amounts of ethylene glycol dimethacrylate which will crosslink a polymer based on HEMA. The de¬ gree of crosslink may be so minuscule as to have little effect on the ultimate properties of the polymer. Crosslinking agents are frequently intentionally added to HEMA based resins to impart a particular quality of crosslinking and toughness to the cured resin. How¬ ever, in the practice of this invention, it is desir- able to use a crosslinker in addition to that which may be inherent in the monomer. Such a crosslinker is soluble in the solvent employed in making the adhesive resin solution. In this respect, one may include the above crosslinker, in its normal impurity concentra- tions, as part of the crosslinker, plus one or more ad¬ ditional crosslinkers that contain at least two acrylyl groups bonded to aromatic containing moiety(ies) . A desirable crosslinker is characterized by the following formulae: wherein Y is an alkali metal such as Li, Na, K, Ru and Cs, and n is 0 or 1. The preferred hard crosslinking agent is one of a crosslinker (cross linking agent) such as 2,2-bis(4- methacryloxy 2-ethoxy- phenyl) propane, diethylenegly¬ col bismethacrylate, the alkali metal salts of 4,4'- bis (4-methacryloxy-2-ethoxy 3-carboxy) biphenyl (salt of the reaction product of 2-hydroxyethylmethacrylate and sym. -tetracarboxylic dianhydride), the alkali metal salts of the reaction product of 2- hydroxyethylmethacrylate and pyromellitic anhydride, the alkali metal salt of the reaction product of 2- hydroxyethylmethacrylate and 3, 3', 4,4'- benzophenonetetracarboxylic anhydride, the alkali metal salt of the reaction product of 2- hydroxyethylmethacrylate and trimellitic anhydride, and the like, in which the alkali metals are one or more of Li, Na, K, Ru and Cs . The preferred crosslinker is typically an diacrylic or dimethacrylic ester or ether of bisphenol A. (d) Also included in the formulation is a photo- initiator. According to one aspect this invention, the light-initiated curing of a polymerizable matrix mate¬ rial involves photosensitization of light-sensitive compounds by ultraviolet or visible light, which, in turn, initiates polymerization of the matrix material. The photoinitiator to be used in this invention com¬ prises a combination of a photosensitive ketone and a tertiary amine. Typical photosensitive ketones in¬ clude benzophenone, acetophenone, thioxanthen-9-one, 9- fluorenone, anthraquinone, ' -methoxyacetophenone, di- ethoxyacetophenone, biacetyl, 2, 3-pentadione, benzyl, 4, . ' -methoxybenzil, 4, 4' -oxidibenzil, and 2,3- bornadione (dl camphroquinone) . Typical tertiary amines include ethyl- -dimethyl amino benzoate, ethyl- 2-dimethyl amino benzoate, 4, 4' -bis (dimethylamino) ben- zophenone, N-methyldiethanolamine, and dimethylamino- benzaldehyde. A preferred combination of the photo¬ initiators is 2, 3-bornanedione with ethyl-2-dimethyl amino benzoate. Other suitable initiator are illus- trated in U.S. Pat. No. 4,674,980 to Ibsen, ' et al . , the disclosure of which is incorporated by reference. Al¬ ternatively, any known photosensitizing system which can function effectively in a solution composition when exposed to light may substitute for the above-named compounds or combinations. The amount of the photoini¬ tiator should be sufficient to initiate polymerization in a selected resin and complete it in depth within about half a minute when the filler-resin composition is exposed to a visible light output of at least 5,000 foot candles. In addition, any known free-radical scavenger (anti-oxidants) such as butylated hydroxy¬ toluene can be used to scavenge small amounts of free radicals generated during extended shelf storage. (e) The solvent employed in making the adhesive mixture of the invention is desirably miscible in water in an amount that facilitates the dissolution of the other ingredients of the formulation. It is desirable to use a volatile solvent that is quickly removed from the tooth on exposure of a coating of the adhesive on the tooth. A less volatile solvent can be used if it does not adversely affect the adhesive interface with the tooth and any composite component to which the ad¬ hesive is bound and serves to secure to the tooth. A preferred solvent is acetone. The most preferred sol- vent is a mixture of acetone and water, typically in the range as set forth in Table 1 below, and most pref¬ erably in the range of 4 parts by weight acetone to 1 part by weight water. Other solvents that might be em¬ ployed, alone or in combination with acetone and/or wa- ter are the hydroxyethylethers such as the monomethyl ether of ethylene glycol, and the like. Optionally, the adhesive coating may contain pig¬ ments such as iron oxide or titanium oxide and a color stabilizing agent such as 2,2-hydroxy-5-tert. octyl phenylbenzotriazole. In formulating the adhesive of the invention, the selection of the ingredients in formulating the coating is not narrowly critical. Illustrative of such a for¬ mulation is the composition as set forth in Table 1. Table 1 Percentage by Ingredients Weight λ Ethylenically unsaturated monomer, 5-30 e.g., 2-hydroxyethyl methacrylate Crosslinker, e.g., Ethoxylated 2-20 bisphenol A dimethacrylate Coupling agent, e.g., Na NTG-GMA 2-30 Photoinitiator, e.g. 0.02-0.6 2,3- bornanedione 0.02-0.3 Ethyl 2-dimethylaminobenzoate 0.00-0.3 Solvent, such as acetone 30-70 Deionized water 5-20 The solution is formed The resulting solution is then coated onto the surface as needed . The coating will self-cure in about 20-30 minutes , but cures in¬ stantly on exposure to light . Light having a wave length of about 480 ηM at an intensity of about 5000 foot-candles is preferred . An exposure of about 30 To 100% , i . e . , no combination of components exceed 100% . second is sufficient to cure the cement in most appli¬ cations . The method of the invention may be effected by the following procedure: (1) The first step in using the adhesive formula¬ tion of the invention involves preparing the tooth sur¬ face undergoing treatment. It is important to clean the surface to which the adhesive coating is being ap¬ plied. Water washing the surface, if an acid wash is not recommended or needed, will prepare the surface provided the surface is thoroughly dry before applying the adhesive coating. If an acid wash is not desired, then apply the adhesive to the tooth portion undergoing treatment as per step (2) below. If an acid wash is desired, then contact the tooth surface with an aqueous conditioning solution comprising at least one strong acid or acidic salt in order to condition the surface. This aqueous conditioning solution comprises (a) a strong acid or combination of acids and may include (b) one or more polyvalent cations (preferably A1+++) which can form relatively water-insoluble precipitates with phosphate ions. The preferred polyvalent cation, when used, is the trivalent aluminum ion, at least as to dental applications where aesthetics is important. Aluminum oxalate gives excellent results. The ferric ion, while usable in some applications, can lead to staining by reduction to ferrous ion in the presence of sulfide. The ferrous sulfide can be generated by the metabolic activity of anaerobic microorganisms. How- ever, sulfides do not form black complexes with alumi- num ions under the conditions of interest. Aluminum oxalate is -soluble in water when formu¬ lated with the other ingredients of the conditioner. The solubility of aluminum oxalate in water depends upon the stoichiometry and pH. Aluminum ions can form insoluble, metastable, microporous, quasi-amorphous precipitates of phosphate surfaces . Aluminum ions can strengthen the altered substrate surface structures by crosslinking and reinforcing the collagenous component of dentin surface reacted upon by the tooth surface with conditioner or etchant aqueous solutions. In applications where color stability and aesthet- ies are not deciding factors, aluminum ions, ferric ions, and other polyvalent cations can be used sepa¬ rately or in combinations in the conditioner/etchant step of the present invention. The function of the incorporation of a compound with one or more carboxyl groups, such as, for example, oxalic acid or an oligocarboxylic acid as exemplified by aluminum oxalate, is believed to be the precipita¬ tion of insoluble calcium and the other complexes which also can assist in obturating the dential tubules of vital dentin, when it is treated with such a condi¬ tioner/etchant solution. The strong acid which is also preferably present in the conditioner and/or etchant solution renders the solution low in pH value. The purposes of the low pH are (1) to dissolve the smeared (disturbed) surface layer on cut dentin, enamel, or other substrates, (2) to partially decalcify intertubular dentin, (3) to re¬ move pellicle, plaque, or other surface contaminants from the substrate, and (4) optionally, to acid etch enamel and other substrate surfaces. Another function of the strong acid component which renders the condi¬ tioner and/or etchant solution strongly acidic (low pH) is to render soluble some or all of the other compo- nents in the solution. The preferred acid is phospho¬ ric acid, or a mixture of phosphoric acid and nitric acid, ranging in concentration from about one-tenth percent to about 50% by weight, preferably, from about 0.1% to 10% by weight and most preferably on the order of about 2 to 5% by weight of the aqueous solution. Compounds such as A1(N03)3 can hydrolyze in the aqueous formulation of the conditioner and/or etchant solution to provide the strong acid and necessary low pH. Such strong acids as hydrochloric acid, perchloric acid, sulfuric acid and others, and acid mixtures may or may not be effective in improving the bond strengths ob¬ tainable in the use of the present invention. Particularly desirable etchant and conditioner so¬ lutions contain the following formulations: Etchant formulation Conditioner f< Drmulation Component weight percent Component weight percent Distilled Wa¬ 50.62 Distilled Wa¬ 92.5 ter ter Methyl Cellu¬ 7.00 Ortho- 2.8 lose phosphoric acid Ortho- 42.32 Nitric acid 1.3 phosphoric acid Red Food Col¬ 0.06 Aluminum ox¬ 3.4 oring alate Coating of these formulations may be effected with a dispensable brush or a skube (a preformed Styrofoam™ sponge) . A preferred etching solution comprises phos- phoric acid alone. A preferred conditioner comprises a mixture of phosphoric and nitric acids plus aluminum oxalate. Leave for 15 seconds and blot dry with a skube. (2) The next or first step, as the case may be involves coating the tooth portion undergoing treatment with the adhesive solution of the invention. Apply 2-5 coats of the adhesive solution onto the prepared bond- ing surface with a dispensable brush. Generally the adhesive coating in dry to touch in about 15 seconds with air drying. At this point, the composite can be affixed to the adhesive, or the adhesive can be light cured. Light activation is generally effected in about 30 seconds. (3) Optionally, more adhesive can be coated on the substrate followed by light-activate for 30 sec¬ onds. Whether more adhesive is added, the composite is applied to the adhesive treated substrate, and the co - posite affixed tooth portion is subjected to light cure, and final cure of the composite-adhesive-tooth structure is effected. Tests were run to determine bond strengths to den¬ tin involving the adhesive formulation of the invention and a competitive product. The formulation of the ad¬ hesive of invention comprised: Formulation components ("FOI") : Percent by wei .ght Acetone 55 . 92 Processed water (deionized water) 14 . 0 Na NTG-GMA 14 . 0 High purity ethoxylated bisphenol 1 AA 8 . 0 dimethacrylate 2-Hydroxymethacrylate 12 . 0 Camphorquinone 0 . 04 Ethyl 2-dimethylaminobenzoate 0 . 04 The formulation (FOI) was made by mixing the in¬ gredients with stirring in the order listed. This for¬ mulation was compared with a commercial adhesive sold by Bisco Inc., 1500 W. Thordal Ave. , Itasca, 111, 60143, under the tradename of "Uni-Bond", called a "one-step" adhesive bonding acrylic resin system, that uses a single solution to form the adhesive resin film. The compared adhesives were — 1. Formulation of invention (FOI) used with preferred etchant (designated "F-1E") ; 2. Formulation of invention (FOI) used with preferred conditioner (designated "F-2C") ; and 3. Uni-Bond with manufacturer's 32% phosphoric acid etchant according to manufacturers instructions (designated "UB") . The bonding tests 2 were conducted by placing the adhesive coatings on the treated substrate, and cured Bond Strength Standard Test: Materials and Equipment: 1. Instron Tester 2. Gelatin capsules, #3 3. Five 1/4-ounce polycons 4. Bovine teeth 5. Dental model trimmer 6. King Temporary Crown and Bridge Material or any other cold curing acrylic resin 7. Den-Mat designed laboratory curing light 8. Timer 9. Mixing sticks 10. ight-Cured Marathon™ A and B Paste (Den-Mat Corporation) 11.Bond strength test fixtures for Instron Tester 12.Water bath Method: 1. Select 5 large bovine teeth. 2. Using dental model trimmer, grind each tooth to a flat, dentin sur¬ face. 3. After all 5 teeth have been ground, remove lids from 5 ^-ounce poly¬ cons and set aside. 4. Into a small disposable beaker, weigh 5-h grams of Kind Powder (Den- Mat Corporation) and 6 grams of Kind Liquid (Den-Mat Corporation) . by exposure to light as indicated below. A heavy body composite, Marathon™ (sold by Den-Mat, Inc.) was placed in a 5.3mm diameter gelatin capsule which was then placed on the substrate and cured with light. The sam- pies were placed in 37°C. H20 for 1 hour or 24 hours, as indicated below, and debonded using an Instron Uni¬ versal 1011 testing machine using a cross head speed of Imm/min. The following results show the mean bond strengths and standard deviations in megapascals of at least 10 mpa: Mix well with a plastic mixing stick and pour into previously set aside polycon lids until half full. 5. Carefully place tooth into center of polycon lid, taking care not to contaminate flat ground surface. Allow Kind to cure at least to a rubbery consistence. 6. Mix another quantity of Kind and pour into polycon lid until full, taking care again not to contaminate flat ground surface. Allow Kind to cure completely. 7. When all 5 samples have been imbedded and Kind is completely cured, apply material to be tested to ground flat surface, following instruc¬ tions for that particular product. 8. Fill small diameter half of each of 5 #3 gelatin capsules with Mara¬ thon™ mixed to a 1:1 paste A/paste B ratio. Apply to prepared tooth surface. 9. Cure each prepared sample in laboratory curing light as follows: 10. Place sample at a 30° angle to the perpendicular in center of curing chamber. 11. Turn on curing light for one minute setting timer. 12. Rotate sample 90° and expose for an additional minute. 13. Mark sample for identification and place m 37°C water bath for one hour or 24 hours, as indicated. 14. Make sure that Instron Tester is configured for bond strength of test¬ ing. 15. After 1 hour or 24 hours, remove samples from conditioning water. Us¬ ing special fixture, stress until failure on Instron at a crosshead speed of 0.02 in/mm. Calculatio bond Strength = loadatfailwe (For # 3 gelatin capsules, area of sample -s ns . areaofsample 0.01380 mm.) Average of three highest values is taken as the bond strength. Application F-1E Application F-2C Application UB Apply ethant to Apply ethant to Apply manufac¬ dentin. After dentin. After turer' s 32% phos¬ 15 sec. , rinse 30 sec, rinse phoric acid with water and with water and etchant, rinse air dry air dry with water and dry with air. Apply 3 coats of Apply 3 coats of Apply two (2) con¬ FOI and gently FOI and gently secutive coats of evaporate sol¬ evaporate sol¬ UB, and air dry. vent with oil- vent with oil- The second coat is free compressed free compressed what is left on air. air. the brush from the first coat. Light cure for Light cure for Light cure for 10 30seconds 30seconds seconds . Apply composite, Apply composite, Apply another method step 8 of method step 8 of coating of UB, footnote 2, su¬ footnote 2, su¬ followed by air pra. pra. drying. Cure according Cure according Cure according to to method steps to method steps method steps 9-12 9-12 and test 9-12 and test and test according according to according to to method steps method steps 13- method steps 13- 13-15 of footnote 15 of footnote 15 of footnote 2, except that the 2. 2. cure was for 2 minutes, carried out three times .. Bond Strength (psi) Data 1 hour water bath - 1391, 1739, 2692, 1743, 368, 589, 587, 1097, 1513, 2107 1014, 1408, 2215 701, 701 Average of high¬ Average of high¬ Average of highest est three sample est three sample three sample re¬ results: 1786, results: 2217, sults: 664, with a standard with a standard with a standard of of deviation of of deviation of deviation of 53. 245. 387. Average of the Average of the Average of the five sample re¬ five sample re¬ five sample re¬ sults: 589, sults: 1569, sults: 1814, with a standard of with a standard with a standard deviation of 122. of deviation of of deviation of 339. 590. 24 hours water bath 2101, 1537, 2687, 1466, 299, 891, 373, 0, 526, 1697, 1461, 1629 2433, 1753 0 Average of high¬ Average of high¬ Average of highest est three sample est three sample three sample re¬ results: 1809, results: 2291, sults: 597, with a standard with a standard with a standard of of deviation of of deviation of deviation of 217. 208. 394. Average of the Average of the Average of the five sample re¬ five sample re¬ five sample re¬ sults: 350, sults: 1685, sults: 1728, with a standard of with a standard with a standard deviation of 337. of deviation of of deviation of 223. 840. Though this invention has been described with re¬ spect to a plurality of details, it is not intended that the invention be limited thereby except to the ex¬ tent that such limitations appear in the claims. Other embodiments that are obvious variations of the embodi¬ ments herein disclosed are intended to be encompassed by this invention.

Claims: Claims : 1. A single package adhesive for tooth bonding application comprising a solvent-based homogeneous mix¬ ture of — a) an ethylenically unsaturated functional and hy¬ groscopically functional mono- mer; b) an ethylenically unsaturated functional and hy¬ groscopically functional coupling agent that is capable of (a) chemically reacting with and through the ethylenic bond of the ethylenically unsaturated-functional monomer of 1) above and (b) chemically bonding to the surface to which the adhesive is applied; c) a poly-ethylenically unsaturated functional crosslinking agent that is capable of reacting with the monomer of 1) above and the coupling agent of 2) above; and d) a photoinitiator that induces addition polymeri¬ zation of an ethylenically unsaturated compound. 2. The single package adhesive of claim 1 wherein a) contains ethylenic unsaturation such that it co-reacts by addition polymerization with b) and c) and a hygroscopic group that contributes to the properties of the adhesive. 3. The single package adhesive of claim 1 wherein the coupling agent is an acrylic-type monomer that possesses acrylic-type unsaturation and contains a surface bonding group. 4. The single package adhesive of claim 3 wherein the surface bonding group is at another part of the coupling agent molecule than the acrylic-type un- saturation and imparts one or more of the following properties to the adhesive coating: 1) chemical bonding capabilities to the substrate surface to which the adhesive coating is applied; and 2) wetting agent properties in that it reduces the surface tension of the adhesive coating, causing the coating to spread across or penetrate more easily the substrate surface onto which the adhe- sive is applied. 5. The single package adhesive of claim 1 wherein the solvent is an aqueous containing organic solvent . 6. The single package adhesive of claim 1 wherein the organic solvent is acetone. 7. The single package adhesive of claim 1 wherein the functional groups of the crosslinking agent are bonded via aliphatic groups, each of up to 10 car¬ bon atoms, to a central organic moiety that is aromatic in nature, in that it comprises a group that has the rigidity characteristics of a benzene ring. 8. The single package adhesive of claim 7 wherein such crosslinking agents contain carboxylic acid alkali metal salt groups directly bonded to a car- bon atom of the rigid ring. 9. The single package adhesive of claim 8 wherein the alkali metal is selected from the group consisting of Li, Na, K, Ru and Cs . 10. The single package adhesive of claim 1 wherein the functional groups of the crosslinking agent are bonded to a central moiety that is aliphatic in na¬ ture in that it comprises a group that has the flexi- bility of an alkane or an alkyl benzene containing com¬ pound. 11. The single package adhesive of claim 10 wherein the functional groups of the crosslinking agent are flexible groups as the residues of ethylene glycol, diethylene glycol, 2, 2-bis (4-hydroxyphenyl) propane, and 2,2, -bis (4-hydroxyphenyl) fluoroalkanes . 12. The single package adhesive of claim 1 wherein the adhesive composition is a homogeneous liquid sin¬ gle-package system. 13. The single package adhesive of claim 12 wherein the adhesive composition is a solution that can be stored in and used from a single container. 14. The single package adhesive of claim 4 wherein the coupling agent is an acrylic-type monomer that pos¬ sesses acrylic-type unsaturation and contains a surface bonding group selected from the group of: i) an alkylene poly¬ vi) phosphinyl ether; vii) stannoyl ii) hydroxyl viii) amide iii) carboxylic acid ix) alkylene amine salt x) alkoxysilyl, and iv) quaternary ammonium xi) acyloxysilyl . v) tertiary amine vi)phosphoryl 15. A homogeneous liquid single-package system comprising: a) an ethylenically unsaturated functional monomer from the group of 2-hydroxyethyl-methacrylate and 2, 3-dihydoxypropylmethacrylate; b) a coupling agent from the group of an alkali metal salt of (i) N-phenylglycine, (ii) the ad¬ duct of N- (p-tolyl) glycine and glycidyl methacry¬ late, and (iii) the adduct of N-phenylglycine and glycidyl methacrylate; c) a crosslinker from the group of 2, 2-bis (4- methacryloxy 2-ethoxy-phenyl) propane, diethyle¬ neglycol bismethacrylate, the alkali metal salts of 4, 4' -bis (4-methacryloxy-2-ethoxy 3- carboxy)biphenyl, the alkali metal salts of the reaction product of 2-hydroxyethylmethacrylate and pyromellitic anhydride, the alkali metal salt of the reaction product of 2- hydroxyethylmethacrylate and 3, 3', 4,4'- bensophenonetetracarboxylic anhydride, the alkali metal salt of the reaction product of 2- hydroxyethylmethacrylate and trimellitic anhy¬ dride, in which the alkali metals are one or more of Li, Na, K, Ru and Cs; d) a photoinitiator; e) a water soluble organic solvent; and f) water. 16. A solution comprising: a) 2-Hydroxyethylmethacrylate b) the alkali metal salt of the adduct of N- (p- tolyl) glycine and glycidyl methacrylate; c) ethoxylated bisphenol A dimethacrylate; and d) a photoinitiator; and e) acetone-water solvent mixture. 17. A method of forming a composite structure, involving the steps of — (a) optionally contacting the adherend surface with an aqueous etching or conditioning solution com¬ prising at least one strong acid or acidic salt in order to condition the surface, followed by rinsing and drying the surface. (b) coating the surface with a solvent-based homoge- neous mixture of: 1) an ethylenically unsaturated functional mono¬ mer; 2' coupling agent; a crosslinker; and 4) a photoinitiator; (c)cure the coating with light; (d) apply a compositing material to the coating; and (e)cure the compositing material in contact with the coating. 18. The method of claim 17 wherein (b) is a so¬ lution. 19. The method of claim 18 wherein the solution comprises: i) an ethylenically unsaturated functional and hy- groscopically functional monomer; ii)an ethylenically unsaturated functional and hy¬ groscopically functional coupling agent that is capable of (a) chemically reacting with and through the ethylenic bond of the ethylenically unsaturated-functional monomer of 1) above and (b) chemically bonding to the surface to which the adhesive is applied; iii) a poly-ethylenically unsaturated functional crosslinking agent that is capable of reacting with the monomer of i) above and the coupling agent of ii) above; and iv) a photoinitiator that induces additional polymerization of an ethylenically unsaturated compound. 20. The single package adhesive of claim 1 wherein the solvent-based homogeneous mixture comprises the following ingredients in the percentages by weight: Ingredients Percentage by Weight an ethylenically unsaturated monomer, 5-30 encompassing 2-hydroxyethyl methacrylate a crosslinker, encompassing ethoxylated 2-20 bisphenol A demethacrylate a coupling agent, encompassing 2-30 Na NTG-GMA a photoinitiator, encompassing 0.02-0.6 2,3-bornanedione 0.02-0.3 Ethyl 2-dimethylaminobenzoate 0.00-0.3 a solvent encompassing acetone 30-70 water 5-20 21. A composite comprising the cured single package adhesive of claim 1 bonded to another surface. 22. The composite of claim 21 wherein the other surface is a portion of a tooth. 23. The composite of claim 22 wherein the portion comprises dentin. 24. The composite of claim 22 wherein the portion comprises enamel. 25. The composite of claim 21 wherein the other surface is one or more of metal, porcelain and plastic.

Inventors: GLACE WILLIAM R, IBSEN ROBERT L, GLACE, WILLIAM, R., IBSEN, ROBERT, L.
Applicants: DEN MAT CORP, DEN-MAT CORPORATION
Application year: 1996
Main classification: C09J4
IPC codes: A61K6, C08F2, C09J4