Biologically compatible adhesive

Abstract: A biologically compatible adhesive that is shelf stable as a single component adhesive and includes a mixture of an adhesive promoting and polymerizable monomer system having a free radical polymerizable monomer or prepolymer having ethylenic unsaturation and a phosphorus containing adhesion promoter, a free radical polymerization catalyst, and an accelerator for the catalyst, the accelerator selected from the group consisting of sulfinic acid or salt thereof, amine or amine salt and mixtures thereof.

Description: This invention relates to compositions which are polymerizable by means of free radical initiation, and more particularly, to dental adhesive and primer compositions having improved adhesion to dentin, enamel and bone. It is most desirable, when filling a tooth cavity with a filling material, such as a polymerizable dental restorative, to ensure good adhesion between the tooth surrounding the cavity and the set (polymerized) filling material since there is thereby obtained a good seal between the set filling material and the tooth which prevents, or at least markedly inhibits, ingress of mouth fluids and bacteria into the filled cavity and thus prevents further decay or loss of the filling material. In order to achieve good adhesion between the filler material and the tooth enamel, it has been recommended to provide a primer or adhesive bonding layer intermediate the filling material and surfaces of a prepared tooth. As disclosed, for example, in Canadian Patent No. 559,648 to Hagger, the bonding intermediate layer, which acts as an adhesive, should present polar groups toward the inorganic crystal lattice (apatite) of the tooth and be anchored by means of a non-polar group in the filling material. In order to accomplish this goal, it was taught to utilize dimethacrylglycerophosphoric acid as a polymerizable intermediate adhesive bonding layer. In practice, the surfaces in a prepared cavity of a tooth were dampened with the dimethacrylglycerophosphoric acid, usually in an alcohol medium, whereafter a paste of the filling material (monomer, polymer and room temperature effective catalyst such as sulfinic acid) was plugged into the cavity. The catalyst then caused simultaneous setting of the adhesive and filling material at the temperature in the mouth. It was also disclosed to dissolve the catalyst in the polymerizable adhesive and to spread the polymerizable adhesive solution on the surface to be bonded. The technique disclosed in the Hagger patent was effective for bonding tooth enamel, dentin and ivory with the polymerizable filling materials existing at that time. Another approach for aiding in the secure placement of fillings, that has been in general use for a number of years now, is the approach of acid etching the dental preparation and applying a low viscosity resin to penetrate the interiors caused by etching and thus prime or line the dental preparation and after curing of the primer layer then applying the higher viscosity polymerizable filling material. The primer is usually a lower viscosity form of the same base polymerizable filling material that will be used to fill the tooth, the difference in viscosity being primarily the result of the addition of less filler to the resin. Because the primer is basically the same system as the filling, compatibility has generally not been a severe problem. However, as the field of polymerizable dental restorative materials has developed a need for still further improved primers and adhesives has become self-evident, particularly with respect to the need for greater bonding strength and reduction of marginal leakage between exposed dentin and enamel surfaces and the restorative filling materials. This need lead to the development of two part chemically cured adhesives, such as those described in U.S. Patent No. 4,182,035 to Yamauchi et al. and in European Patent application No. 0084407 to Bunker. The adhesive described in the Yamauchi et al. patent comprises a first package consisting of a free radical polymerizable monomer and a diacyl peroxide, and a second package comprising an alkali or alkaline earth metal salt of an arylsulfinic acid and a volatile solvent. The adhesive disclosed in the Bunker application comprises a polymerizable phosphorous compound, a tertiary amine, a polymerization catalyst, a diluent, and an effective amount of a metal selected from iron, copper, manganese, cobolt, tin, chromium, nickel and zinc dissolved in a polar solvent. The metal dissolved in the polar solvent is stored separately from the remainder of the composition and is added thereto prior to the application of the adhesive to a tooth surface. While self-curing multi-part systems of the type described above can provide improved adhesion between a tooth surface and a polymerizable filling material, the limitations associated with the need for storing two or more components in separate containers until immediately before use can not be minimized. For example, the need for mixing several components prior to use requires not only time, but skill, since it is essential that the proper proportions of polymerizable material, catalyst and accelerator be mixed, without the inclusion of air bubbles, which act as a polymerization inhibitor, so as to ensure the formation of a polymerized adhesive having the desired physical characteristics. Then, too, polymerizable adhesives of the above type normally have limited working times available and must be hardened for a predetermined length of time before a polymerizable filling material can be plugged over the adhesive in a cavity. Following this, one must wait until the filling material and the underlying adhesive have hardened sufficiently to allow the filling material to be shaped and finished with burrs and/or abrasives and the like in order that the rigid filling material does not transmit forces which can dislodge and break or exceed the adhesive bond strength of the newly placed two component adhesive to dentin. Finally, self-curing two part adhesive systems of the type described above, preferably are used with multi-part self-curing filler materials. One of the recent advances in polymerizable filling systems has been the one component light curing composite filling material that can be cured in from about 5 to about 40 seconds as contrasted to the 5 to 15 minutes of cure time required for the self-curing two component system and does not require dentist office time for mixing. One component light curing filling materials are premixed in the factory to include all catalysts and activators in a single component package that is essentially free of air and needs no subsequent mixing and is sold in a light-tight package in order to exclude activating light. These light curing one component composite filling materials may be applied directly into the prepared restorative cavity and are hardened in a matter of seconds by the application of visible or ultraviolet light. This new one component product has brought about a need for new and improved primers and adhesives which are compatible with strong biologically safe adhesion to the tooth and to the new filling materials. Preferred new primers and adhesives would, in most instances, be convenient one component actinic light cure compositions. A one-pack shelf-stable adhesive has not been described previously. EP-A-0 088 527 discloses the concept of improving the adhesion between a composite dental filling material and tooth enamel by first applying a composition containing a polyunsaturated phosphate to the tooth enamel and subsequently filling the cavity in the tooth with filling material. In an alternative, the reference discloses incorporating the polyunsaturated phosphate in a composite dental filling material comprising an inert filler, an ethylenically unsaturated binder, an initiator for the binder and the polyunsaturated phosphate. As with conventional composite filling material the catalyst or initiator is brought into contact with the polymerizable ingredient of the filling material only immediately before introduction of the filling material into a dental cavity. EP-A-0 120 559 discloses an adhesive comprising halogenated polymerizable phosphorus compound. A shelf-stable one-package composition is not known from this reference. SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved primer or adhesive composition for the hard tissues of the human body which displays firm, sustained adhesion to bones and to dentin and enamel of teeth and which, when applied to the human body, can be cured by brief exposure to actinic light. It is another object of this invention to provide an adhesive composition which is in the form of a stable one component system that is especially useful as a dental adhesive when light cured. Yet another object is to provide a dental adhesive composition which is compatible with one component light cure filling materials and which is, itself, a one component system which is curable by exposure to visible light. DETAILED DESCRIPTION The above and other objects and advantages are accomplished in accordance with the present invention by providing a polymerizable dental adhesive composition as defined in claim 1 comprising a free radical polymerizable monomer or prepolymer having ethylenic unsaturation; a phosphorus derivative preferably a polymerizable phosphorus derivative, having ethylenic unsaturation; a catalyst, preferably a photosensitive catalyst, especially a diketone; a sulfinic acid (or a salt thereof), preferably both a sulfinic acid (or salt thereof) and an amine (or salt thereof); and optionally, a solvent for the above ingredients. It should be understood that when a phosphorus derivative having ethylenic unsaturation is used, the phosphorus derivative may function as part or all of the polymerizable monomer or prepolymer. The adhesive composition of this invention is in the form of a shelf-stable one component polymerizable system which obviates the difficulties of the prior art and which, when cured, exhibits exceptionally high adhesive bond strengths between tooth or bone surfaces, particularly dentin, and subsequently applied filling materials. Thus, while it is known that sulfinates have been used in catalytic quantities in self-curing compositions, especially those containing polymerizable partial esters of phosphoric acid, a peroxide and a polymerizable monomer as one component, and an alkali metal salt of an arylsulfinic acid and an amine and solvent therefor as a second component, it was unexpected to find it possible to combine a polymerizable monomer or prepolymer, a polymerizable phosphate, an amine and a sulfinate in a one component system which is both stable and useful as a dentin adhesive when light cured. As the free radical-polymerizable monomer or prepolymer to be employed in this invention, use may be made of any monomer, dimer, trimer, or other oligomer of the type that is usable in dental applications. Thus, the polymerizable monomer portion of the present adhesive composition generally comprises one or more monofunctional or polyfunctional ethylenically unsaturated monomers or prepolymers, e.g., dimers, trimers, and other oligomers, or mixtures or copolymers thereof, based on acrylic or methacrylic or itaconic acid, or derivatives thereof, including their esters which can be polymerized by free radical initiation. These materials include, but are not limited to acrylic and methacrylic acid, itaconic acid and the like, acrylic or methacrylic or itaconic acid esters of monohydric or polyhydric alkanols or polyhydric alcohols containing at least one phenyl group. Examples of such compound include monovinylmethacrylates , e.g., methylmethacrylate, ethyl acrylate, propyl methacrylate, hydroxyethylmethyacrylate, hydroxypropylmethacrylate, diethylene glycol acrylate, triethylene glycol acrylate, the monoester of trimellitic acid with hydroxyethyl methacrylate, hydroxypropyl itaconate and the like, esters of aliphatic polyhydric alcohols, such as for example, the di- and polyacrylates, the di- and polymethacrylates, and the di- and polyitaconates of alkylene glycols, alkoxylene glycols, alicyclic glycols and higher polyols, such as ethylene glycol, triethylene glycol, tetraethylene glycol, tetramethylene glycol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and the like, or mixtures of these with each other or with their partially esterified analogs, and their prepolymers, such compound or mixture optionally having free hydroxyl content. Typical compounds of this type, include but are not limited to, trimethylolpropane triacrylate, trimethylolethane triacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylene glycol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexacrylate, tripentaerythritol octaacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol dimethacrylate, glycerin trimethacrylate, ethylene glycol dimethacrylate, butanediol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, bisphenol-A dimethacrylate, bisphenol-A diglycidyl methacrylate, 2,2'-bis-(4- methacryloxyethoxyphenyl) propane and so on. Also included among the polymerizable monomers which may be used are the vinyl urethane or urethaneacrylate prepolymers which are well known in the art. These prepolymers are polymerizable by free radical initiation and may be prepared, for example, by reacting an organic diisocyanate or an isocyanate-terminated urethane prepolymer with an ethylenically unsaturated monomer which is reactive with the diisocyanate or urethane prepolymer. These polymers also may be prepared by reacting a hydroxyl-containing material, such as a polyol or a hydroxyl-terminated urethane prepolymer with an ethylenically unsaturated monomer which is reactive with the polyol or hydroxyl-terminated urethane. The urethane prepolymers, which may be linear or branched, carry isocyanate end groups and generally are prepared by reacting a compound having hydroxyl functionality with a molar excess of diisocyanate. Any of a wide variety of diisocyanates may be used to prepare the isocyanate-terminated urethane prepolymer including aliphatic, cycloaliphatic, heterocyclic, and aromatic diisocyanates, and combinations of these. Examples include, but are not limited to, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,4-phenylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate, hexamethylene diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, p,p'-diphenyl diisocyanate, butylene-1,4-diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, tetramethylene-1,4-diisocyanate, butylene-2,3-diisocyanate, cyclohexylene-1,2-diisocyanate, methylene-bis-(4-phenyl-isocyanate), diphenyl-3,3'-dimethyl-4,4'-diisocyanate, xylylene diisocyanate, cyclohexane-1,4-diisocyanate, 1-methoxyphenyl-2,4-diisocyanate and the like, and mixtures thereof. A wide variety of compounds having hydroxyl functionality may be used to form the isocyanate-terminated urethane prepolymers. For example, diols of the structure may be used, where R₁ and R₂ are hydrogen atoms or alkyl groups, e.g., methyl, and Ar is a divalent aromatic group in which each free valency is on an aromatic carbon atom, and where a and b, independently, may be zero or an integer. Other suitable hydroxyl containing compounds include diols and polyols such as ethylene glycol, propylene glycol, triethylene glycol, tetramethylene glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like, or esters of acrylic acid, methacrylic acid or itaconic acid or the like with aliphatic polyhydric alcohols. Among the more preferred hydroxyl containing compounds are the esters of acrylic or methacrylic acid and a hydroxyalkanol of at least two carbon atoms such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyisopropyl methacrylate, and the like. Formation of the isocyanate terminated urethane prepolymers may be assisted by the use of a catalyst known in the art to assist polyurethane formation, for example, tertiary amines and metal salts, e.g., tin salts, titanium salts and the like. To form the vinyl urethane or urethane-acrylate prepolymer starting materials, an isocyanate-terminated urethane prepolymer or a diisocyanate is reacted with an ethylenically unsaturated compound having hydroxyl functionality. These compounds include for example, esters of acrylic acid, methacrylic acid or itaconic acid with aliphatic polyhydric alcohols, such as hydroxyethyl acrylate, hydroxypropyl methacrylate or the like. The resulting vinyl urethanes are well known in the art and are described for example, in U.S. Patent No. 3,629,187 to Waller, U.S. Patent No. 3,759,809 to Carlick et al, U.S. Patent No. 3,709,866 to Waller and U.S. Patent 4,459,193 to Ratcliffe et al, all of these patents being incorporated herein by reference. Formation of the vinyl urethane prepolymers may be assisted by the use of the same catalysts noted above, namely, tertiary amines and metal salts. Of course, the foregoing list of polymerizable ethylenically unsaturated monomers and prepolymers is intended to be exemplary only, and other known polymerizable materials can be used in compositions of this invention. In practice, a mixture of two or more ethylenically unsaturated materials may be, and commonly is, employed. In the preferred aspects of the invention the polymerizable monomer portion of the composition is liquid at ambient temperature, e.g. 20-25°C. The polymerizable monomer portion of the composition generally should comprise from 0.5 to 99.998% by weight of the composition, with amounts ranging from 1 to 99.98% being preferred, and amounts ranging from 1.5 to 99.8% being more preferred. The phosphorus derivative which is used as an adhesion promoter in the present composition, may comprise any of the the well known phosphorus-containing adhesion promoters. The phosphorus derivative may be polymerizable or non-polymerizable, however the preferred phosphorus-containing adhesion promoters comprise polymerizable phosphorus materials having ethylenic unsaturation and include, among others, organic esters of one or more acids of phosphorus (hereinafter referred to as phosphorus acid esters), wherein the organic portion of the ester contains at least one polymerizable ethylenically unsaturated group. The organic portion of the ester may be alkenyl, alkenoxy, cycloalkenyl, aralkenyl, or alkenaryl, and preferably may have from 2 to 40 carbon atoms. The organic portion may be straight chain, branched, or cyclic, can contain skeletal hetero atoms, i.e., atoms other than carbon, and can be unsubstituted or substituted with moieties which do not interfere with the free radical polymerization of the phosphorus acid esters. Examples of saturated and unsaturated phosphorus acid esters which may be used include, but are not limited to, monomers containing phosphoric acid groups such as hydroxyethyl methacrylate monophosphate, 2,2'-bis(α-methacryloxy-β-hydroxypropoxyphenyl) propane diphosphonate (BIS-GMA diphosphonate), BIS-GMA diphosphate, dibutyl phosphite, di-2-ethylhexyl phosphite, di-2-ethylhexyl phosphate, glyceryl-2-phosphate, glyceryl-phosphoric acid, methacryloxyethyl phosphate, glyceryl dimethacrylate monofluorophosphate, and glyceryl dimethacrylate phosphate. Other suitable polymerizable phosphorus acid esters are disclosed, for example, in U.S. Patent No. 4,182,035 to Yamauchi et al, U.S. Patent No. 4,222,780 to Shibantani et al, U.S. Patent No. 4,235,633 to Tomioka, U.S. Patent No. 4,359,117 to Yamauchi et al, U.S. Patent No, 4,368,043 to Yamauchi et al, European Patent Application No. 0084407 to Bunker, and U.S. Serial No. 464,778, to Prodger, Billington & Blackwell filed February 7, 1983, and assigned to the assignee of this invention. Of the polymerizable phosphorus acid compounds disclosed in the above patents and application, the preferred compounds are those polyethylenically unsaturated monophosphates of the formula: and salts thereof, in which R is an organic radical having a valency of n + 1; and R may be interrupted by one or more oxygen atoms and may be substituted or unsubstituted, and may comprise an aliphatic radical, or a cycloaliphatic radical, or an aryl radical; R¹ is a hydrogen atom, alkyl C₁ - C₃, halogen or CN radical, and n is an integer of at least 1. Preferably n is an integer of 2 or more, and more preferably from 3 to 6. Examples of the preferred compounds include pentaerythritol triacrylate monophosphate, pentaerythritol trimethacrylate monophosphate, dipentaerythritol pentaacrylate monophosphate, and dipentaerythritol pentamethacrylate monophosphate. The phosphorus acid compound normally should comprise from 0.25 to 99.998% by weight of the adhesive composition, with amounts ranging from 1 to 50% being preferred. In a more preferred embodiment the phosphorus acid compound would comprise from 2 to 29.8% by weight of the composition. The catalyst component may comprise any of those free radical initiators normally used in conjunction with polymerizable ethylenically unsaturated materials, although those which will initiate polymerization at room temperature are preferred. Thus, the catalyst may comprise, for examble, a peroxide such as dibenzoyl peroxide, dilauroyl peroxide, acetyl peroxide, benzoyl peroxide and the like. In a preferred aspect, the catalyst comprises an actinic light sensitive initiator, such as ultraviolet light-sensitive initiators or visible light sensitive initiators. As examples of suitable ultraviolet light-sensitive initiators there may be mentioned the monoketals of an aromatic 1,2-diketones, benzophenones, substituted benzophenones, benzoin methyl ether, isopropoxybenzoin, benzoin phenyl ether or benzoin isobutyl ether. Among the suitable visible light sensitive initiators, α-diketones, such as camphoroquinone, are particularly preferred. The preferred initiators are the visible light sensitive initiators. The catalyst generally is employed in the range of from 0.001 to 10% of the composition. In a preferred embodiment the catalyst is used within the range of from 0.01 to 5%. In a still further preferred embodiment, from 0.1 to 2% by weight of catalyst is employed. In addition to the foregoing constituents, the adhesive composition also includes 0.001 to 10 wt.-% of an accelerator system comprising a sulfinic acid or salt thereof. In a preferred embodiment both an amine or amine salt and the sulfinic acid or salt thereof are present. In a preferred embodiment, the amine or amine salt is used in the range of 0.001 to 10% by weight and the sulfinic acid or a sulfinic acid salt is used in the range of from 0.01 to 5%, the combined weight being in the range of from 0.01-10% by weight. In a still more preferred embodiment, the amine or amine salt is used in an amount of from 0.1-8% and the sulfinic acid or salt thereof is used in an amount from 0.1-2%, the combined amount ranging from 0.2 to 10% by weight. The amine or amine salt employed in the preferred aspects of this invention desirably is a secondary or tertiary amine rather than a primary amine, since the use of a secondary or tertiary amine leads to significantly accelerated curing. Examples of suitable amines include N,N-dimethylaniline, N,N-dimethyl-p-toluidine, N-methyl-N-β-hydroxyethylaniline, N,N-di-β-hydroxyethylanaline, N-methylanaline, N-methyl-p-toluidine, dimethylamino benzoic acid and its esters and butyl diethanolamine. In a preferred aspect, the amine or amine salt comprises a (meth)acrylate group. Examles of such amines and their acrylic or methacrylic acid amine salts include dimethylaminoneopentyl (meth)acrylate, morpholinoethyl methacrylate, morpholinoethyl acrylate and the like. The salt of sulfinic acid employed in the invention may be a salt of any organic sulfinic acid, but in terms of stability, a salt of a sulfinic acid attached to an aryl group is desirable. The salts may be alkali metal salts, alkaline earth metal salts and amine salts, although the alkali metal and alkaline earth metal salts are preferred. As examples of suitable sulfinic acid salts there may mentioned sodium benzene sulfinate, calcium benzene sulfinate, triethyl ammonium benzene sulfinate, lithium toluene sulfinate, benzene sulfinic acid, N,N-dimethyl-p-toluidine sulfinate and the like. Particularly desirable are the salts of toluene sulfinic acid. The sulfinic acid or sulfinic acid salt acts as an accelerator for the catalyst system as does the amine salt and it has been found that, in a preferred aspect of this invention, both constituents should be present to ensure the desired adhesive strength and rate of polymerization of the composition. The relative amounts of initiator, amine or amine salt and sulfinic acid or salt thereof is selected such that the composition will be shelf-stable, i.e., will not self cure in less than about 3 months when stored at 20°C and less than about 2 days when stored at 50°C. In this application, a composition will be considered to have self cured at the intended operating temperature when it has polymerized to the extent that it has become solid. The adhesive composition optionally may include a non-reactive solvent such as an alcohol, e.g. ethanol. When used, the solvent would comprise as much as about 90% by weight of the composition. As necessary, other polymers, fillers, stabilizers and so forth may be incorporated in the composition of this invention. As the polymers incorporated to reduce the polymerization shrinkage or for viscosity adjustment, there may be mentioned polymethyl acrylate (or methacrylate), polyethyl acrylate (methacrylate), polyhydroxyethyl methacrylate, polystyrene, unsaturated polyesters, etc. The fillers may be aluminum oxide, α-quartz powders, colloidal silica, glass beads etc. within the range of 0.04 to 100 µm in particle diameter. As examples of said stabilizers, there may be mentioned butylated hydroxy toluene, hydroxymethoxybenzophenone, and the like. As will be appreciated, conventional systems which employ reactive free radical initiator systems, such as a peroxide-amine system, or a peroxide-sulfinic acid-amine system, require that the catalyst or initiator system be brought into contact with the polymerizable monomer and phosphorus acid compound only immediately before introducing the adhesive composition into a dental cavity. To this end it is common practice to put up the initiator system in two-part packs, one part containing the initiator and the other part containing the accelerator, with the polymerizable constituents being mixed with either or both of the initiator and accelerator. In accordance with the invention of the present application in preferred embodiments, the adhesive is to be polymerized by actinic radiation and the composition is put up as a single pack. In addition to being especially suited for adhesion to dentin, the adhesive composition of the present invention adheres quite well to tooth enamel. Accordingly, the composition may be used in orthodontics, for example, to bond orthodontic brackets or bands to tooth enamel, or in periodontics, for the treatment of enamel to which a splint is to be attached. Further, the composition may be used as an adhesive in the buildup of teeth with composite materials and the attachment of acrylic veneers via a composite or unfilled resin for the same purpose. Similarly, they may be used as adhesives in the attachment of single unit pontics to the abutment teeth via a composite or unfilled resin. It also has been found that the adhesive composition of the present invention may be used to adhere composite materials to metal substrates, and in this connection, the adhesive composition can find application in the construction of crowns and bridges in which a polymeric material is bonded to the framework or substrate formed of a metal, such as a chromium/cobalt alloy, a gold/copper alloy or the like, or such metals coated with reactive oxide layers as, for example, tin oxide, silicon dioxide, aluminum oxide and the like. It is also contemplated that the primers and adhesives of this invention may be filled to such an extent that they would serve not only as primers and adhesives, but also as pit and fissure sealants and dental filling composites. In this specification the term "(meth)acrylate" is intended to refer to an acrylic or methacrylic acid moiety, and the term "polymerizable monomer or prepolymer" is intended to refer to monomers, dimers, trimers or oligomers which contain ethylenic unsaturation and which may be polymerized by free radical initiation, including phosphorus derivatives containing ethylenic unsaturation. The ranges of "polymerizable monomer portion" recited herein include the phosphorus-containing adhesive promoter to the extent that the phosphorus-containing adhesive promoters are polymerizable phosphorus materials having ethylenic unsaturation. All of the percentages recited herein are by weight based on the weight of the entire composition unless otherwise stated. Having generally described the invention, a more complete understanding can be obtained with reference to certain specific examples, which are included for purposes of illustration only. EXAMPLE 1 Preparation of Urethane Dimethyacrylate (UDMA) To a mechanically stirred mixture of 59.19 weight parts of dry hydroxypropyl methacrylate (HPMA), 0.0177 weight parts of monomethyl ether hydroquinone (MEHQ) and 0.05 weight parts of stannous octoate in a reactor, heated to 45°C and purged with dry air, there is added 40.76 weight parts of trimethylhexamethylene diisocyanate while maintaining the reaction temperature at 45° to 55°C. After the addition is complete, the reaction mixture was held for 16 hours at 50° to 55°C and heated at 70°C until the % NCO assay is below 0.01%. EXAMPLE 2 Dipentaerythritol Pentaacrylate Phosphoric Acid Ester (PENTA) A solution of technical dipentaerythritol monohydroxypentaacrylate (1 mole) and triethylamine (1 mole) in dry ether was slowly added with stirring to a solution of phosphorus oxychloride (1 mole) in dry ether, at 0°C. After stirring for two hours at room temperature, the triethylamine hydrochloride formed was filtered off and the product remaining in solution was hydrolyzed by addition of the ether solution to ice water with stirring at below 10°C. The resultant mixture was separated and the separated ether layer was then extracted with a 25% aqueous sodium carbonate solution. The aqueous extract exhibited a PH of about 8. The alkaline aqueous extract was then acidified with 18% acid and an oily material was formed. The oily material was extracted with methylene chloride and the extract was dried over anhydrous sodium sulphate. The methylene chloride was then removed from the dried extract under reduced pressure to give the title compound as a clear straw-colored oil. EXAMPLE 3 A general procedure for the preparation of all of the resins used for the bond strength testing is illustrated as follows: Resin A Weight Part UDMA 59.72 Triethylene glycol dimethacrylate (TEGDMA) 29.92 Bisphenol A dimethacrylate (BPDMA) 10.34 Butylated hydroxytoluene (BHT) 0.02 A mixture of these four components was mixed with agitation at 25° to 50°C until a homogeneous solution was obtained. Composition B1 Weight Part Resin A 86.59 Dipentaerythritol pentaacrylate phosphoric acid ester of Example 2 (PENTA) 9.55 butyl diethanol amine (BDE) 3.38 lithium para-toluene sulfinate (LTS) 0.24 Camphoroquinone (CQ) 0.24 This activated resin is prepared by the method described for Resin A, except that the entire operation was carried out under yellow lighting or red lighting which does not cure the resin. EXAMPLE 4 The following dentin bonding compositions were prepared by the method described in Example 3, except that the amine was varied as given in Table I, and evaluated in five replications by the method described below. All compositions shown are in parts by weight. The average bond strengths are illustrated in Table I. Composition Resin A PENTA Amines LTS CQ Bond (MPa) Strength S.D. (MPa) B1 86.62 9.55 BDE 3.38 0.24 0.24 4.94 1.77 C1 86.38 9.69 DMANPA 3.49 0.22 0.22 8.08 3.10 D1 86.16 9.18 MPEMA 4.18 0.24 0.24 6.75 2.29 E1 86.42 9.53 MPEA 3.87 0.24 0.24 5.77 2.57 As shown in Table I, the amines containing a polymerizable substituent such as acrylate or methacrylate appear to afford more favorable bond strengths. The following abbreviations in Example 4 have not been identified previously: 1. MPa is Mega Pascals. 2. DMANPA is dimethylaminoneopentyl acrylate. 3. MPEMA is 2-N-morpholinoethyl methacrylate. 4. MPEA is 2-N-morpholinoethyl acrylate. 5. S. D. is standard deviations. EVALUATION METHOD Preparation of Teeth Extracted human teeth used for the bond strength testing were treated in 1% sodium hypochlorite for 18 to 24 hours, washed with water, mechanically sanded with 120/320/600 grit carborundum paper until the dentin was exposed, and followed by hand sanding with 600 grit carborundum powder on glass slab. The prepared teeth were stored in distilled water in a refrigerator at about 4°C until needed. Method of Bond Strength Test The teeth were then individually prepared as follows: the tooth was blow dried with compressed dry air to ensure the dentin surface was free from noticeable moisture, the test conpositions were applied with a brush and blown with compressed dry air to give a thin film on the surface. A small plastic straw with 1.84 mm of inner-diameter and 2 to 3 mm of length was filled with uncured Prisma-Fil® composite filling material (a light curing composite filling material sold by L.D. Caulk Division of Dentsply International, Inc.) and seated on the dentin to form as a post. The upper open end of the straw was covered with a thin film of cellophane. Gentle pressure was applied to the post through the cellophane with the tip of the handpiece of a Prisma-Lite® light curing unit (sold by L.D. Caulk Division of Dentsply International, Inc.). The unit was activated and the composite was cured for 30 seconds. The specimens were stored in distilled water at 37°C for 1 to 3 days and their posts were sheared on an INSTRON with 50 kg load and 1mm/min. head speed. The shear bond strengths were calculated and are shown in the following tables. EXAMPLE 5 The following compositions illustrated the concentration effects on bond strengths of amines shown in Table I. These resins were prepared by the method described in Example 3 and evaluated by the method described in Example 4. The compositions shown are in weight parts and the bond strengths are summarized in the following tables. All compositions designated by the letter B, with the exception of B8, contain BDE, all compositions designated by the letter C, with the exception of C6, contain DMANPA, and all compositions designated by the letter D, with the exception of D6, contain MPEMA. Composition Resin A PENTA BDE LTS CQ Bond (MPA) Strength S.D. (MPA) B1 86.62 9.55 3.38 0.24 0.24 4.94 1.77 B2 86.54 9.75 3.47 0.00 0.24 4.28 1.97 B3 86.69 9.51 3.44 0.24 0.12 5.97 3.72 B4 91.25 4.81 3.46 0.24 0.24 4.42 3.30 B5 96.14 0.00 3.38 0.24 0.24 1.48 2.69 B6 85.78 9.85 6.97 0.25 0.25 2.91 1.11 B7 88.28 9.55 1.69 0.24 0.24 2.10 0.61 B8 89.97 9.55 0.00 0.24 0.24 3.99 2.55 Composition Resin A PENTA DMANPA LTS CQ Bond (MPA) Strength S.D. (MPA) C1 86.38 9.65 3.49 0.22 0.22 8.08 3.10 C2 88.12 9.64 1.87 0.12 0.24 6.24 2.2 C3 95.82 0.00 3.71 0.24 0.24 0.16 0.27 C4 76.21 19.34 3.96 0.24 0.24 3.15 1.45 C5 85.67 10.42 3.67 0.00 0.24 4.26 3.61 C6 89.62 9.96 0.00 0.25 0.17 4.77 1.05 C7 92.89 4.82 1.93 0.12 0.24 6.35 2.29 C8 TEGDMA 46.05 46.48 6.94 0.17 0.17 4.89 1.30 Composition Resin A PENTA MPEMA LTS CQ Bond (MPA) Strength S.D. (MPA) D1 86.16 9.18 4.18 0.24 0.24 6.75 2.29 D2 76.43 18.99 4.11 0.23 0.23 5.68 2.12 D3 87.93 9.53 2.07 0.24 0.24 4.83 1.72 D4 86.11 9.4 4.14 0.12 0.24 6.30 1.11 D5 81.76 9.46 8.32 0.22 0.24 7.17 2.62 D6 89.62 9.96 0.00 0.25 0.17 4.77 1.05 D7 92.83 4.73 2.08 0.12 0.24 5.88 2.41 As illustrated in Tables II - IV, the following conclusions may be drawn: 1. Without PENTA in the compositions, the adhesion is very poor. 2. Sufficient adhesion can be obtained using either an amine or LTS accelerator. 3. Superior adhesion is obtained when both an amine and LTS accelerator is used. EXAMPLE 6 Other adhesion promoters such as polymerizable and non-polymerizable phosphates, phosphonates and phosphites in place of PENTA are illustrated in this Example. The composition preparation and test method were the same as described in Examples 3 and 4, except as otherwise indicated. The bond strengths are summarized in Table V. Composition Resin A Adhesion Promoter Amines LTS CQ Bond (MPA) Strength S.D. (MPA) F 83.93 PETMAP 9.64 MPEMA 5.96 0.24 0.24 4.02 1.54 G 88.1 GPDMA 9.7 DMANPA 1.85 0.24 0.12 2.68 3.18 H 85.95 HEMAP 9.52 DMANPA 4.12 0.23 0.18 1.66 1.8 I 94.11 BISGMAPP 4.77 DMANPA 0.94 0.12 0.06 2.12 1.08 J 87.28 GP 8.65 DMANPA 3.72 0.23 0.12 0.5 1.45 K 85.92 DP 9.4 MPEMA 4.2 0.24 0.24 1.78 2.5 L 86 DEHPA 9.38 MPEMA 4.15 0.24 0.24 1.99 2.23 M 85.9 DEHPI 9.45 MPEMA 4.18 0.24 0.24 3.30 2.04 N 43.07 BISGMAP 9.66 DMANPA 1.73 0.11 0.11 2.77 0.77 The following abbreviations in Example 6 have not been identified previously: 1. PETMAP is Petaerythritol trimethacrylate phosphoric acid ester. 2. GPDMA is glycerol 2-phosphate dimethacrylate. 3. HEMAP is 2-methacryloxyethyl phenyl phosphate. 4. BISGMAPP is BIS-GMA di(phenyl phosphonate). 5. GP is glycerol 2-phosphate. 6. DP is dibutyl phosphite. 7. DEHPA is di(2-ethylhexyl) phosphate. 8. DEHPI is di (2-ethylhexyl) phosphite. 9. BISGMAP is BIS-GMA diphosphate. In comparing the results shown in Table V with those illustrated in Tables II, III and IV, it is apparent that the use of the polymerizable phosphates PENTA and PETMAP resulted in compositions which exhibit superior adhesion. EXAMPLE 8 The following compositions N, O, and P were prepared and the stability of each composition was tested. Composition N - Dibenzoyl Peroxide 1 weight part Polymethyl Methacrylate 20 weight part LTS 3 weight part The above components were charged into a vessel and blended until homogenous. The composition N is a powder blend. Composition O - CQ 1 weight part Polymethyl Methacrylate 20 weight part LTS 3 weight part Composition O was prepared in the same manner as for composition N. This composition also is a powder blend. Composition P - PENTA 20 weight part Ethylene Glycol Dimethacrylate 20 weight part N,N-Demethyl para-Toluidine 2 weight part Composition P was prepared in accordance with Example 3. This liquid composition was mixed with an equal weight part of composition N or O. The mixture of P and N formed a solid mass instantaneously. The mixture of compositions P and O, which were mixed and stored in the dark at room temperature, resulted in a soft unusable gel within two hours. Composition P, by itself, was stable when stored in a clear amber bottle at room temperature for more than two weeks. Example 8 illustrates that the simple substitution of a light cure initiator (CQ) for an acyl peroxide inititator (BPO) does not, in and of itself, result in an acceptably stable one component composition. It is evident from the foregoing example that the invention may be described as comprising a liquid polymerizable dental adhesive composition comprising a polymerizable monomer or prepolymer, a catalyst active on command to catalyze the polymerization of the polymerizable monomer or prepolymer, and an accelerator and adhesion promoting system comprising at least two components which are balanced either in concentration or activity or both such as to provide at least three months of usable shelf life. Another characteristic of the accelerator adhesion promoting system components is that when the components are not in close tolerance balance they bring about premature polymerization of the polymerizable monomer or prepolymer or fail to bring about the polymerization of the polymerizable monomer or prepolymer within less than three minutes. EXAMPLE 9 STABILITY TEST Seven resin compositions shown in Example 5 were selected for stability study. They were kept at room temperature at 20°C to 25°C and in an oven at 50°C separately and visually inspected for whether they would gel on standing over a period of time. The results are illustrated in Table VI. Further, the shear bond strengths were determined after a week at 50°C for these compositions by the method described in Example 4. The test results are summarized in Table VII. Compositions Time Elapsed Conditioning Temperature Physical Appearance B1 2½ - Month 20° - 25°C Liquid B1 2 - Week 50°C Liquid B2 2½ - Month 20°- 25°C Liquid B8 2½ - Month 20° - 25° Liquid C1 2½ - Month 20° - 25° Liquid C1 2 - Week 50°C Liquid C5 1½ - Month 20° - 25° Liquid C6 1½ - Month 20° - 25°C Liquid D1 2½ - Month 20° - 25°C Liquid D1 2 - Week 50°C Liquid Compositions Bond Strength (MPa) S.D. (MPa) B1 4.84 1.82 B2 2.21 1.43 C1 8.39 3.77 C5 6.19 3.92 D1 7.88 2.50 B8 2.56 1.01 C6 1.77 1.16

Claims: A polymerizable dental adhesive composition for priming purposes comprising: (a) adhesion promoting and polymerizable monomer or prepolymer system with at least one free radical polymerizable monomer or prepolymer having ethylenic unsaturation and a phosphoric acid ester containing phosphoric acid groups as adhesion promoter, said adhesion promoter optionally containing ethylenic unsaturation in which latter case it may form all of said polymerizable monomer or prepolymer, characterized in further comprising (b) 0.001 to 10% wt. -% free radical polymerization catalyst; and (c) 0.001 to 10 wt. -% accelerator for said catalyst, and in that (i) the composition is a one-pack shelf-stable composition; (ii) a sulfinic acid and/or salt thereof is used as an accelerator; and (iii) the relative amounts of said catalyst and said accelerator are selected such that the composition will not self-cure in less than three months when stored at 20°C and less than two days when stored at 50°C. The composition of Claim 1 wherein said catalyst comprises a photosensitive catalyst. The composition of Claim 2, wherein said catalyst comprises a visible light cure catalyst. The composition of Claim 3, wherein said catalyst comprises an α-diketone. The composition of Claim 4, wherein said catalyst comprises camphoroquinone. The composition of Claim 2 or 3, wherein said polymerizable monomer or prepolymer includes a derivative of at least one unsaturated carboxylic acid selected from the group consisting of (meth)acrylic acid, and itaconic acid, and mixtures thereof. The composition of Claim 6, wherein said polymerizable monomer or prepolymer includes at least one derivative of (meth)acrylic acid having at least one ester functionality wherein the alcohol moiety of said ester functionality is selected from the group consisting of monohydric alkanols, polyhydric alkanols, and polyhydric alcohols containing at least one phenyl group. The composition of Claim 6, wherein said polymerizable monomer or prepolymer includes at least one member selected from the group consisting of triethylene glycol di(meth)acrylate and bisphenol A di(meth)acrylate. The composition of Claims 2 or 3, wherein said polymerizable monomer or prepolymer includes at least one reaction-product of a monoester of a dihydric alcohol with a polyisocyanate. The composition of Claim 9, wherein said monoester is selected from the group consisting of ethylene glycol mono(meth)acrylate and propylene glycol mono(meth)acrylate, and wherein said polyisocyanate is an aliphatic diisocyanate. The composition of Claim 10 wherein said aliphatic diisocyanate is selected from 2,2,4-trimethyl hexamethylene diisocyanate and hexamethylene diisocyanate. The composition of Claims 2 or 3 wherein said at least one polymerizable monomer or prepolymer includes a mixture of at least one ester or (meth)acrylic acid with a monohydric alkanol, a polyhydric alkanol or a polyhydric alcohol containing at least one phenyl group, and at least one reaction product of a monoester of a polyhydric alcohol with an aliphatic, aromatic, or cycloaliphatic diisocyanate. The composition of Claims 2 or 3, wherein said phosphoric acid ester containing phosphoric acid groups as adhesion promoter comprises a polymerizable phosphoric acid derivative having ethylenic unsaturation. The composition of Claim 13, wherein said polymerizable phosphoric acid derivative comprises a polyethylenically unsaturated monophosphate of the formula: and salts thereof, in which R is an organic radical having a valency of n + 1; and R may be interrupted by one or more oxygen atoms and may be substituted or unsubstituted, and may comprise an aliphatic radical, or a cycloaliphatic radical, or an aryl radical; R¹ is a hydrogen atom, alkyl C₁ - C₃, halogen or CN radical, and n is an integer of at least 1. The composition of Claim 14 , wherein said polymerizable phosphoric acid derivative is a member selected from pentaerythritol tri(meth)acrylate monophosphate and dipentaerythritol penta(meth)acrylate monophosphate, and mixtures thereof. The composition of Claims 8, 11 or 12 which comprises an amine or amine salt selected from butyldiethanolamine, dimethylaminoneopentyl(meth)acrylate, morpholino ethyl(meth)acrylate, dimethylamino benzoic acid or its esters and mixtures thereof, as an accelerator. The composition of Claims 8, 11 or 12, wherein said salt of sulfinic acid is selected from alkali metal salts, alkaline earth metal salts, and amine salts of aryl sulfinic acids, and mixtures thereof. The dental adhesive composition of Claim 1 which comprises a shelf stable mixture of: (a) an adhesion promoting and polymerizable monomer or prepolymer system with at least one free radical polymerizable monomer or prepolymer having ethylenic unsaturation and at least one phosphoric acid derivative having ethylenic unsaturation, and mixtures thereof, said phosphoric acid derivative comprising an ethylenically unsaturated monophosphate of the formula: and salts thereof, in which R is an organic radical having a valency of n + 1; and R may be interrupted by one or more oxygen atoms and may be substituted or unsubstituted, and may comprise an aliphatic radical, or a cycloaliphatic radical, or an aryl radical; R¹ is a hydrogen atom, alkyl C₁ - C₃, halogen or CN radical, and n is an integer of at least 1; (b) a photosensitive free radical polymerization catalyst; (c) a secondary or tertiary amine or salt thereof; (d) an alkali meal salt of an aryl sulfinic acid, an alkaline earth metal salt of an aryl sulfinic acid, or an amine salt of an aryl sulfinic acid; and optionally, (e) an inert solvent, an inert filler, or mixtures thereof; wherein said components (b), (c), and (d) are present in said composition in relative amounts such that said composition will not self cure in less than three months when stored at 20°C and less than two days when stored at 50°C. The dental composition of Claim 18 which is packaged as a one component system, and wherein said polymerization catalyst comprises an α-diketone. The dental composition of Claim 19, wherein said α-diketone comprises camphoroquinone, and said amine or amine salt is selected from the group consisting of butyldiethanolamine, dimethylaminoneopentyl(meth)acrylate, morpholinoethyl(meth)acrylate, dimethylamino benzoic acid or its esters and mixtures thereof.

Inventors: BLACKWELL GORDON B, HUANG CHIN-TEH, BLACKWELL, GORDON B., HUANG, CHIN-TEH
Applicants: DENTSPLY INT INC, DENTSPLY INTERNATIONAL, INC.
Application year: 1985
Main classification: A61K6
IPC codes: C08L33, C09J4, A61K6, C09J133, C09J11