specific examples of the aliphatic amine salts of polymerizable phosphoric esters represented by the above general formula ( 1 ) include the monoethanolamine , dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate salts of ( meth ) acryloyloxyethyl phosphate , ( meth ) acryloyloxypropyl phosphate , ( meth ) acryloyloxyethyloxyethyl phosphate and bis [( meth ) acryloyloxyethyl ] phosphate . especially preferred is methacryloyloxyethyl phosphate dimethylaminoethyl methacrylate salt . the radical - polymerizable unsaturated monomer used in the dental adhesive compositions of the present invention can be a monofunctional or a multifunctional unsaturated monomer . examples of useful monofunctional unsaturated monomers include methyl ( meth ) acrylate , ethyl ( meth ) acrylate , propyl ( meth ) acrylate , butyl ( meth ) acrylate , pentyl ( meth ) acrylate , hexyl ( meth ) acrylate , 2 - hydroxyethyl ( meth ) acrylate , vinyl acetate , styrene , acrylonitrile , glycidyl methacrylate and benzyl methacrylate . among others , methyl ( meth ) acrylate , benzyl methacrylate and 2 - hydroxyethyl methacrylate are preferred . examples of useful multifunctional unsaturated monomers include ethylene glycol di ( meth ) acrylate , polyethylene glycol di ( meth ) acrylate having 2 to 20 ethylene glycol units , 1 , 6 - hexanediol di ( meth ) acrylate , neopentyl glycol di ( meth ) acrylate , trimethylolpropane tri ( meth ) acrylate , ## str3 ## where r &# 34 ; is hydrogen or methyl , and p is a whole number of 1 to 20 , ## str4 ## wherein r 3 is hydrogen or methyl and the two r 3 radicals may be the same or different , and x is an alkylene group of 1 to 6 carbon atoms or ## str5 ## 1 , 2 - bis [ 3 - meth ) acryloyloxy - 2 - hydroxypropoxy ] ethane and 1 , 4 - bis [ 3 -( meth ) acryloyloxy - 2 - hydroxypropoxy ] butane . among the foregoing radical - polymerizable unsaturated monomers , preferred monomers are methyl ( meth ) acrylate , benzyl methacrylate , 2 - hydroxyethyl methacrylate , ethylene glycol di ( meth ) acrylate , triethylene glycol di ( meth ) acrylate , nonaethylene glycol di ( meth ) acrylate , tetradecaethylene glycol di ( meth ) acrylate , trimethylolpropane triacrylate , 1 , 6 - hexanediol di ( meth ) acrylate , compounds of the general formula ( 2 ) or ( 3 ) in which r &# 34 ; is methyl , the compound of the general formula ( 4 ) in which all r 3 radicals are methyl and x is hexylene ( hereinafter referred to as u - 4h ), and the compound represented by the following formula ( hereinafter referred to as u - 4ha ). ## str6 ## in the dental adhesive compositions of the present invention , the weight ratio of components ( a ) to component ( b ) should be such that compound ( a ) is preferably present in an amount of 0 . 1 to 30 parts by weight , more preferably 0 . 5 to 10 parts by weight and most preferably 1 . 0 to 5 . 0 parts by weight , per 100 parts by weight of component ( b ). the radical polymerization initiator used as component ( c ) in the dental adhesive compositions of the present invention may be a photopolymerization initiator or a redox polymerization initiator . where a photopolymerization initiator is used as the radical polymerization initiator , both ultraviolet light polymerization initiators and visible light polymerization initiators may be used . however , if the dental adhesive compositions of the present invention are to be used in the oral cavity , it is preferable that they contain a photopolymerization initiator capable of initiating the polymerization in response to visible light in the wavelength range of about 400 to 1 , 200 nm , because ultraviolet light may do harm to the oral mucosa . accordingly , it is preferable to use a photopolymerization initiator which can be excited by visible light in the wavelength range of about 400 to 1 , 200 nm . the photopolymerization initiator may comprise a single photopolymerization initiator which exhibits hydrogen abstracting power when excited by light , or a combination of a so - called photosensitizer ( i . e ., a compound that is excited by light but does not exhibit hydrogen abstracting power ) and a reducing agent . an example of the former is camphorquinone . in this case , however , a reducing agent may preferably be used in combination with the photopolymerization initiator to enhance its hydrogen abstracting power . in this situation , the photopolymerization initiator can be regarded as a photosensitizer . examples of useful photosensitizers are - diketone compounds such as benzil and diacetyl . among others , camphorquinone is preferably used because of its high polymerization activity . where a combination of a photosensitizer and a reducing agent is used in the dental adhesive compositions of the present invention , the reducing agent can be any compound that exhibits hydrogen abstracting power when it receives energy from the excited photosensitizer . as such reducing agents , tertiary amines are preferably used . examples of useful tertiary amines include aliphatic amines such as trimethylamine , triethylamine and tripropylamine ; and aromatic amines such as isoamyl 4 -( n , n - dimethylamino ) benzoate , hexyl 4 -( n , n - dimethylamino ) benzoate , heptyl 4 -( n , n - dimethylamino ) benzoate , octyl 4 -( n , n - dimethylamino ) benzoate , 4 , 4 &# 39 ;- bis ( dimethylamino ) benzophenone , 4 , 4 &# 39 ;- bis ( diethylamino ) benzophenone and 4 , 4 &# 39 ;- bis ( dibutylamino ) benzophenone . among others , aromatic tertiary amines are preferred . in particular , a combination of camphorquinone as a photosensitizer and 4 , 4 &# 39 ;- bis ( diethylamino ) benzophenone as a reducing agent is most preferred because of its excellent visible light polymerizing activity . the appropriate amount of photopolymerization initiator added to the dental adhesive compositions of the present invention may vary according to the type of photopolymerization initiator or photosensitizer / reducing agent used . however , the photopolymerization initiator is usually added in an amount of 0 . 005 to 30 % by weight based on the total amount of the radical - polymerizable unsaturated monomer ( s ). for example , in the camphorquinone / 4 , 4 &# 39 ;- bis ( diethylamino ) benzophenone system , camphorquinone is preferably added in an amount of 0 . 005 to 30 % by weight , more preferably 0 . 03 to 20 % by weight , based on the total amount of the radical - polymerizable unsaturated monomer ( s ), and 4 , 4 &# 39 ;- bis -( diethylamino ) benzophenone is preferably added in an amount of 0 . 01 to 25 % by weight , more preferably 0 . 05 to 20 % by weight . where a redox polymerization initiator is used in the dental adhesive compositions of the present invention , it preferably comprises a combination of an aromatic amine and an organic peroxide , a combination of a sulfinic acid salt and an organic peroxide , or a combination of an aromatic amine , a sulfinic acid salt and an organic peroxide . examples of useful organic peroxides include diacetyl peroxide , dilauroyl peroxide , distearoyl peroxide , dibenzoyl peroxide and di - p - chlorobenzoyl peroxide . among them , dibenzoyl peroxide is preferably used because of its excellent room temperature polymerizing activity . as the aromatic amine , there may be used any of primary , secondary and tertiary amines . however , tertiary amines are preferably used from the viewpoint of room temperature polymerizing activity . preferred examples of useful aromatic amines include , n , n - dimethylaniline , n , n - diethylaniline , n , n - di ( β - hydroxyethyl ) aniline , n , n - dimethyl - p - toluidine , n , n - diethyl - p - toluidine , n , n - di ( β - hydroxyethyl )- p - toluidine , n - methylaniline , n - methyl - p - toluidine , n , n - dimethylanisidine , n , n - diethylanisidine and diphenylamine . among them , n , n - dimethyl - p - toluidine and n , n - di ( β - hydroxyethyl )- p - toluidine are more preferred from the viewpoint of room temperature polymerizing activity . examples of useful sulfinic acid salts include sodium p - toluenesulfinate , sodium benzenesulfinate , potassium benzenesulfinate , calcium benzenesulfinate , barium benzenesulfinate and ammonium benzenesulfinate . among them , sodium p - toluenesulfinate is preferably used from the viewpoint of room temperature polymerizing activity . where a redox polymerization initiator is used the organic peroxide is preferably used in an amount of 0 . 01 to 10 % by weight , more preferably 0 . 05 to 5 % by weight , based on the total amount of the radical - polymerizable unsaturated monomer ( s ). in order to control their viscosity from the viewpoint of workability , the dental adhesive composition of the present invention can contain low - boiling organic solvents such as ethanol , isopropanol and chloroform . in addition , the dental adhesive compositions of the present invention can also contain inorganic fillers , organic polymers , colorants , polymerization inhibitors , antioxidants , ultraviolet light absorbers and the like , in commonly employed amounts . examples of useful inorganic fillers include silica powder , quartz powder and various glass powders ; examples of useful organic polymers include polymethyl methacrylate and polystyrene ; examples of useful colorants include various pigments and dyes ; and examples of useful polymerization inhibitors include hydroquinone and methylphenol . the dental adhesive compositions of the present invention contain at least the above - described components ( a ), ( b ) and ( c ), until use , these three components may be stored in a mixed state . however , where the dental adhesive composition of the present invention comprises a combination of components whose storage stability will be reduced during storage in a mixed state , it is also possible to store those components separately and mix them prior to use . for example , where a redox polymerization initiator is used , it is possible to divide component ( b ), namely a radical - polymerizable unsaturated monomer or monomers , into two parts , add an organic peroxide to one part , and add an aromatic amine or a sulfinic acid salt to the other . these two parts may be stored separately and mixed prior to use . in the dental adhesive compositions of the present invention , a redox polymerization initiator and a photopolymerization initiator may be used in combination . the dental adhesive compositions of the present invention can be applied to a variety of restorative materials . insofar as materials to be bonded to dentin are concerned , they have excellent bonding properties to thermosetting resins for use in composite resins ( i . e ., composite materials obtained by blending a multifunctional monomer with an inorganic filler ) and crown resins ; thermoplastic resins for use in denture bases , such as polymethyl methacrylate , polysulfone and polycarbonate ; inorganic materials such as various cementing materials , amalgam , alumina , gold , and alloys ; and the like . the present invention is further illustrated by the following examples . however , these examples are not to be construed to limit the scope of the invention . ______________________________________preparation of restorative material a ( visible lightcurable composite resin ) ingredient amount______________________________________2 , 2 - bis [ 4 - methacryloyloxyethoxy ) phenyl ]- 8 gpropane ( hereinafter referred to asbis - mepp ) triethylene glycol dimethacrylate 12 g ( hereinafter referred to as tegdma ) silane - treated quartz powder ( comprising 74 gquartz powder to which 2 % by weight ofγ - methacryloyloxypropyl trimethoxy silanehas been added , and having an averageparticle diameter of about 4 μm ) finely powdered silicon dioxide (# r - 972 , 6 gmanufactured by nippon aerosil co ., ltd .) camphorquinone 0 . 4 gisoamyl 4 -( n , n - dimethylamino ) benzoate 2 g______________________________________ according to the above formulation , multifunctional monomer , inorganic fillers and visible light polymerization initiators were blended in a dark room to obtain a visible light curable composite resin ( hereinafter referred to as restorative material a ). ______________________________________preparation of restorative material a ( visible lightcurable composite resin ) ingredient amount______________________________________2 , 2 - bis [ 4 -( 3 - methacryloyloxy - 2 - hydroxy - 40 gpropoxy ) phenyl ] propane ( hereinafterreferred to as bis - gma ) tegdma 60 gcamphorquinone 0 . 7 gisoamyl 4 -( n , n - dimethylamino ) benzoate 2 . 8 g______________________________________ according to the above formulation , multifunctional monomers and visible light polymerization initiators were blended in a dark room to obtain a visible light curable crown resin ( hereinafter referred to as restorative material b ). ______________________________________preparation of restorative material c ( redox polymerizationtype composite resin ) ingredient amount______________________________________ ( catalyst paste ) bis - gma 8 gtegdma 12 gsilane - treated quartz powder ( same as 74 gused in restorative material a ) finely powdered silicon dioxide ( same as 6 gused in restorative material a ) benzoyl peroxide 2 g ( base paste ) bis - gma 8 gtegdma 12 gsilane - treated quartz powder ( same as used 74 gin restorative material a ) finely powdered silicon dioxide ( same as 6 gused in restorative material a ) dihydroxyethyl - p - toluidine 4 g______________________________________ according to the above formulations , various ingredients were blended to obtain a catalyst paste and a base paste . these pastes were stored separately . the bonding properties of a dental adhesive composition using a photopolymerization initiator were evaluated according to the following procedure . ( 1 ) freshly extracted cattle fore - teeth were cut with a precision cutter ( isomet ; manufactured by buhler ag ) to expose a flat enamel or dentin surface . then , using a piece of no . 1000 water - resistant abrasive paper , the exposed surface was fully polished under a stream of water . ( 2 ) the polished surfaces of the above specimens were treated with an etchant ( manufactured by gc dental industries co ., ltd . ), washed with water , and then air - dried . ( 3 ) a dental adhesive composition to be tested was applied to the polished and etched surface of each specimen . when the composition contained any volatile component such as solvent , it was evaporated and expelled by exposure to a stream of air for about 10 seconds . ( 4 ) a cylindrical silicone ring ( openable on one side ) having an inner diameter of about 5 mm , a height of about 5 mm and a wall thickness of about 3 mm was placed on the surface to which the dental adhesive composition had been applied . then , the silicone ring was filled with a liquid restorative material to a height of about 3 mm . ( 5 ) the aperture of a visible light projector ( gc light : manufactured by gc dental industries co ., ltd .) was brought into contact with the upper end of the silicone ring filled with the restorative material . thus , the restorative material and the adhesive composition were cured by exposure to visible light for 60 seconds . after the lapse of about 10 minutes , the silicone ring was removed to obtain a specimen having the restorative material bonded to the enamel or dentin surface . ( 6 ) after the entire specimen was stored in water at 37 ° c . for one day , a rod formed of methyl methacrylate resin and having the same diameter as the restorative material was joined to the top of the restorative material by means of a rapid - polymerizable resin ( uni fast ; manufactured by gc dental industries co ., ltd .). the resulting assembly was subjected to a tensile test for the measurement of bond strength . the measuring conditions were as follows . the bonding properties of a dental adhesive composition using a redox polymerization initiator were evaluated in the same manner as described above , except that the dental adhesive composition was prepared by mixing fluids a and b immediately before use and the restorative material was prepared by mixing the catalyst paste and base paste of restorative material c immediately before use and kneading the mixture for 30 seconds . more specifically , freshly extracted cattle fore - teeth were cut , polished , etched , washed with water , and then dried as described in steps ( 1 ) and ( 2 ) above . then , the dental adhesive composition was applied to each specimen as described in step ( 3 ) above , and a silicone ring was placed thereon and filled with restorative material c as described in step ( 4 ) above . after the assembly was allowed to stand at room temperature for 10 minutes , the silicone ring was removed to obtain a specimen having the restorative material bonded to the enamel or dentin surface . the bond strength of the dental adhesive composition was measured in the same manner as described for photopolymerizable adhesive compositions . the aliphatic amine salts of polymerizable phosphoric esters , radical - polymerizable unsaturated monomers and visible light polymerization initiators listed in table 1 were blended with a general - purpose mixer in a dark room to obtain various dental adhesive compositions . using each of these dental adhesive compositions , restorative material a was bonded to enamel and dentin surfaces , and the resulting bond strengths were measured . the results thus obtained are shown in table 2 . table 1__________________________________________________________________________ aliphatic amine amounts ofamounts of radical - polymerizable salt of polymerizationunsaturated monomers ( g ) phosphoric initiators used ( g ) examplehema ester camphor - tertiaryno . (* 1 ) tegdma bis - gma bis - mepp u - 4ha ( g ) quinone amine (* 6 ) __________________________________________________________________________1 20 40 60 -- (* 2 ) 2 . 0 0 . 8 1 . 22 20 -- 20 60 -- (* 2 ) 2 . 0 0 . 8 1 . 23 20 -- 20 60 (* 2 ) 2 . 0 0 . 8 1 . 24 20 20 20 40 (* 2 ) 2 . 0 0 . 8 1 . 25 20 20 20 40 (* 2 ) 1 . 0 0 . 8 1 . 26 20 20 20 40 (* 2 ) 5 . 0 0 . 8 1 . 27 20 20 20 40 (* 3 ) 2 . 0 0 . 8 1 . 28 20 20 20 40 (* 4 ) 2 . 0 0 . 8 1 . 29 20 20 20 40 (* 5 ) 2 . 0 0 . 8 1 . 2__________________________________________________________________________ (* 1 ) 2hydroxyethyl methacrylate (* 2 ) methacryloyloxyethyl phosphate dimethylaminoethyl methacrylate (* 3 ) methacryloyloxyethyl phosphate diethylaminoethyl methacrylate (* 4 ) methacryloyloxypropyl phosphate dimethylaminoethyl methacrylate (* 5 ) methacryloyloxyethyl phosphate monoethanolamine (* 6 ) 4 , 4bis ( diethylamino ) benzophenone table 2______________________________________example bond strength ( kg / cm . sup . 2 ) no . enamel dentin______________________________________1 215 452 224 313 209 524 237 685 217 556 240 517 231 488 201 419 214 43______________________________________ dental adhesive compositions were prepared in the same manner as in example 1 , except that the radical - polymerizable unsaturated monomers , aliphatic amine salt of polymerizable phosphoric ester , and visible light polymerization initiators listed in table 3 were used . then , the bond strengths of these compositions were measured in the same manner as in example 1 . the results thus obtained are shown in table 4 . table 3__________________________________________________________________________amounts of radical - polymerizable aliphatic amine amounts of polymerizationunsaturated monomers ( g ) salt of initiators used ( g ) examplevinyl hema phosphoric camphor - tertiaryno . acetate styrene (* 1 ) bis - gma ester ( g ) quinone amine (* 6 ) __________________________________________________________________________10 10 10 20 60 (* 2 ) 2 . 0 0 . 8 1 . 211 20 -- 30 50 (* 2 ) 2 . 0 0 . 8 1 . 212 -- 20 30 50 (* 2 ) 2 . 0 0 . 8 1 . 2__________________________________________________________________________ table 4______________________________________example bond strength ( kg / cm . sup . 2 ) no . enamel dentin______________________________________10 198 4511 205 4312 190 35______________________________________ ______________________________________ingredient amount______________________________________ [ radical - polymerizable unsaturated monomer / redoxpolymerization initiator mixture ( 1 - a )] u - 4ha 20 gtriethylene glycol dimethacrylate 10 gbis - gma 50 g2 - hydroxyethyl methacrylate 20 gmethacryloyloxyethyl phosphate 2 . 0 gdimethylaminoethyl methacrylatedibenzoyl peroxide 1 . 0 g2 , 6 - di - tert - butyl - 4 - methylphenol 0 . 05 g [ radical - polymerizable unsaturated monomer / redoxpolymerization initiator mixture ( 1 - b )] 2 - hydroxyethyl methacrylate 10 gethanol 90 gdihydroxyethyl - p - toluidine 0 . 8 gsodium p - toluenesulfinate 0 . 5 g______________________________________ the above mixtures ( 1 - a ) and ( 1 - b ) were separately prepared by blending the ingredients with a mixer in a dark room , and mixed immediately before use . when measured according to the procedure for the evaluation of dental adhesive compositions using a redox polymerization initiator , the bond strengths to enamel and dentin of this dental adhesive composition after storage in water for one day were 231 kg / cm 2 and 49 kg / cm 2 , respectively . using the dental adhesive composition obtained in example 1 , its bonding properties to various restorative materials was evaluated in the same manner as in example 1 . the results thus obtained are shown in table 5 . table 5______________________________________ mean bond mean bond strength strengthexample to enamel to dentinno . restorative material ( kg / cm . sup . 2 ) ( kg / cm . sup . 2 ) ______________________________________14 restorative material b 198 4315 commercially available one - 242 38 part composite resin (* 7 ) 16 commercially available two - 214 41 part composite resin (* 8 ) 17 polymethyl methacrylate 227 50 (* 9 ) ______________________________________ (* 7 ) occlusin ( manufactured by ici co ., ltd .) (* 8 ) microrest ap ( manufactured by gc dental industries co ., ltd .). (* 9 ) acrypet # vh ( manufactured by mitsubishi rayon co ., ltd .). in the same manner as in example 13 , two dental adhesive compositions containing no aliphatic amine salt of polymerizable phosphoric ester were prepared according to the following formulations ( the combination of 2 - a and 2 - b and the combination of 3 - a and 3 - b . then , the bonding properties of these compositions was evaluated in the same manner as in example 13 . ______________________________________ingredient amount______________________________________ ( 2 - a ) u - 4ha 20 gtriethylene glycol dimethacrylate 10 gbis - gma 50 g2 - hydroxyethyl methacrylate 20 gmethacryloyloxyethyl phosphate 2 . 0 gdibenzoyl peroxide 1 . 0 g ( 2 - b ) 2 - hydroxyethyl methacrylate 10 gethanol 90 gdihdyroxyethyl - p - toluidine 0 . 8 gsodium p - toluenesulfinate 0 . 5 g ( 3 - a ) u - 4ha 20 gtriethylene glycol dimethacrylate 10 gbis - gma 50 g2 - hydroxyethyl methacrylate 20 gdimethylaminoethyl methacrylate 2 . 0 gdibenzoyl peroxide 1 . 0 g ( 3 - b ) 2 - hydroxyethyl methacrylate 10 gethanol 90 gdihydroxyethyl - p - toluidine 0 . 8 gsodium p - toluenesulfinate 0 . 5 g______________________________________ when measured after storage in water for one day , the bond strengths of dental adhesive composition 2 ( the combination of 2 - a and 2 - b ) to enamel and dentin were 184 kg / cm 2 and 25 kg / cm 2 , respectively . similarly , the bond strengths of dental adhesive composition 3 ( the combination of 3 - a and 3 - b ) to enamel and dentin were 107 kg / cm 2 and 10 kg / cm 2 , respectively .
this invention provides dental adhesive compositions consisting essentially of an aliphatic amine salt of a polymerizable phosphoric ester , as represented by the formula ## str1 ## where r and r &# 39 ; are specific radicals ; at least one radical - polymerizable unsaturated monomer ; and a radical polymerization initiator . these compositions are useful in bonding living dental tissue restoration materials to living tooth tissues , particularly to dentin .