Abstract:
The invention concerns a process for preparing a polymer composition, that is free-radical/photochemical and thermal curing epoxide-methacrylate and/or isocyanate-methacrylate adhesives in broadest terms, dental/medical adhesives, and dental restoratives. Furthermore the dual curing epoxide-methacrylate and/or isocyanate-methacrylate adhesives can be used in the optical industry, in optoelectronics and microelectronics, for example for the adhesion of complicated optical components in the combination glass/glass, glass/metal. Advantageous is the small shrinkage during polymerization and the good mechanical properties in combination with the possibility of step-wise or one-step polymerization.

Description:
This is a continuation, of application Ser. No. 08/231,535, filed Apr. 22, 1994, now abandoned. 
    
    
     The invention relates to a dental composition or kit of parts for preparing a polymer, to a process for preparing said polymers and polymer products obtained theory, notably artificial teeth. 
     BACKGROUND OF THE INVENTION 
     Dental filling materials mainly consist of liquid polymerizable organic monomers and/or polymers, reactive diluents, polymerization initiators, stabilizers, and fillers. 
     These composite materials have their good mechanical properties such as high flexural strengths, high compressive strengths and their hardness. Furthermore they are polishable and it is possible to adjust their dye. The most frequently used monomers are esters of methyacrylates and higher multifunctional alcoholes or isocyanates such as the bismethacrylate of biphenol-A diglycidyl ether, urethane bismethacrylates. 
     One of the main disadvantages using composites as dental filling materials is the relatively high shrinkage of organic monomers during polymerization. The shrinkage causes the well known effect of contraction gaps and subsequent cracks. Common dental composites show a shrinkage of 2.5 up to 4.0 vol.-%. 
     It is well known that the shrinkage directly depends on the molecular weight of polymerizable organic monomers. On the other hand, increasing molecular weights of the monomers are combined with an increasing viscosity of the resin. Therefore reactive diluents such as oligoethyleneglycoidimethacrylates, are necessary to obtain a lower viscosity and the possibility to incorporates the desired amount of fillers. However, reactive diluents show a relatively high shrinkage by themselves, for example 12.89 vol-% for pure triethyleneglycoldimethacrylate. 
     Moreover, conventional used composites snow a relatively low self-adhesion to teeth, metals are ceramics. In numerous experiments using epoxide polymers and methacryates for the preparation of IPNs (J. Polym. Sci. Part Al Polym. Chem. 30 (1992) 1941, J. Appl. Chrom. 24 (1991) 692, Polym. 31 (1990) 2066,) multiphase systems were obtained which have insufficient mechanical, thermal and optical properties or which result in microphase separated polymers (Acta Polymerica 38 (1987) 547 and DO 226731) with insufficient adhesion to teeth and ceramics. 
     DESCRIPTION OF THE INVENTION 
     Therefor it is the object of the invention to provide a process and composition for preparing a polymer composition for dental purposes exhibiting a low shrinkage and a high self-adhesion to ceramics and metals. 
     This object is advanced by a process according to claim 1. Preferably the macromonomers have a generally formula I or II: ##STR1## wherein A and D are unsaturated moieties, B is a moiety arisen from a diepoxide or a diisocyanate and C is a HX-residue selected from the group consisting of --OH, --COCH, --NH 2 , --NH--, --SH. 
     The macromonomers I and II preferably are α,ω-terminated poly (epoxide-carboxylic acid) macromonomers of formulas M-1, M8 and M-9, α,ω-terminated poly(epoxide-amine) macromonomers of formulas M-2 to M-5, M-10 and M-1 I or α,ω-terminated poly(epoxide-phenol) macromonomers of formulas M-6, M-7 and M-12 are described in the following literature (J. Klee, H.-H. Horhold, H. Schotz, Acta Polym. 42 (1991) 17-20; J. Klee et. al. Polym. Bull. 27 (1992) 511-517) and in the patent literature (DD 277 689, DD 279 667, DE-P 42 17 761.8). They are characterized by the structures M-1 to M-12: ##STR2## wherein 
     R is a residue derived from a diepoxide, notably a residue of the following formula ##STR3## whereby X is C(CH 3 ) 2 , --CH 2  --, --O--, --S--, --CO--, --SO 2  -- 
     R 1  denotes hydrogen or a substituted or unsubstituted C 1  to C 12  alkyl group or an oxyalkyl group, C 2  to C 12  alkenyl group, C 5  to C 1  2 cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl 
     R 2  is a difunctional substituted or unsubstituted C 1  to C 12  alkyl group, C 2  to C 12  alkenyl group, C 5  to C 12  cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl, 
     R 3  denotes hydrogen or a substituted or unsubstituted C 1  to C 12  alkyl group, C 2  to C 12  alkenyl group, C 5  to C 12  cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl, 
     R 4  is a substituted or unsubstituted C 6  to C 12  aryl, such as ##STR4## whereby X is C(CH 3 ) 2 , --CH 2  --, --O--, --S--, --CO--, --SO 2  -- and n is an integers of n=1, 2, 3, 4, 5, 6, 7, 8 
     Macromonomers M-1, M-2, M-3, M- are synthesised in two steps. At first by reaction of excessive bisphenol-A diglycidyl ether DGEBA, bisphenol-F diglycidyl ether DGEBF, butanediol diglycidyl ether BDODGE, tetrahydro terephtalic acid diglycidyl ether or diglycidyl aniline and methacryoic acid MAA (x&gt;2y) an oligomer mixture is obtained. This mixture contains the bismethacrylate of DGEBA (Bis-GMA, n=O) along with mono-GMA and unreacted DGEBA as well as governed by the epoxide-comonomer ratio. The formation of macromonomers follows in a second reaction of DGEBA and mono-GMA, respectively with primary monoamines to M-2, disecondary diamines to M-3 (J. Klee et al. Polym.Bull. 27 (1992) 511-517, DD 279667), carboxylic acids to M-1 (DE 4217761.8), or biphenols to M-6 (J. E. Klee et al., Acta Polym. 44 (1993) 163). ##STR5## 
     During the epoxide ring cleavage by carboxylic acids an amount of approximately 20% of the epoxide groups is opened to the corresponding primary alcohols. Consequently, macromonomers M-1, M-2, M-3 and M-6 contains booth types of molecules having primary and/or secondary alcohol units. 
     Macromonomers M-4 and M-5 are prepared by one- or two-step reactions of the diepoxides, primary monoamines or disecondary diamines and 2,3-epoxypropyl-metharylate using amine in excess and a mol ratio a&lt;b, and 2c+a=b. The macromonomers M-4 and M-5 also obtainable by terminating reaction of α,ω-amino terminated prepolymers with 2,3-epoxypropyl-methacrylate (DD 277689, J.Klee, H.-H. Horhold, H. Schutz, Acta Polym. 42 (1991) 17-20). ##STR6## 
     Instant of amines also were used bisphenols or dicarboxylic acids to produce macromonomers M-7 and M-8, respectively. ##STR7## 
     Macromonomers M-9 to M-12 are prepared by one- or two-step reactions of the diepoxides, primary monoamines, disecondary diamines, dicarboxylic acids, or phenols and amino alkyl methacrylates. 
     The polymer composition comprises α,ω-terminated poly(urethane) macromonomers, α,ω-terminated poly(urea) macromonomers or α,ω-terminated poly(thiourethane) macromonomers of the following formulas M-1 3 to M-24 which are polymerizable in a mixture with di-or polyepoxides and/or di- or polyisocyanates and polyamines and/or primary monoamines and/or disecondary diamines or dicarb-oxylic acids, dicarboxylic acid anhydrides, diphenols, or dithioles: ##STR8## wherein R is a residue derived from a diisocyanate, notably a residue of the following formula ##STR9## R 1  denotes hydrogen or a substituted or unsubstituted C 1  to C 12  alkyl group, C 2  to C 12  alkenyl group, C 5  to C 12  cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl 
     R 2  is a difunctional substituted or unsubstituted C 1  to C 12  alkyl group, C 2  to C 12  alkenyl group, C 5  to C 12  cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl 
     R 3  denotes hydrogen or a substituted or unsubstituted C 1  to C 12  alkyl group, C 2  to C 12  alkenyl group, C 5  to C 12  cycloalkyl, C 6  to C 12  aryl or C 7  to C 12  aralkyl, 
     R 4  is a substituted or unsubstituted C 6  to C 12  aryl, such as ##STR10## whereby X is C(CH 3 ) 2 , --CH 2  --, --O--, --S--, --CO--, --SO 2  -- and n is an integers of n=1, 2, 3, 4, 5, 6, 7, 8, . . . 
     It is possible to use the polymer composition as an one-part composition or as two part-composition. A two-part composition which is mixed immediately before use contains for example the following substances in the parts A and B: 
     part A: macromonomer, reactive diluent, di- or polyepoxide or di-or polyisocyanate and polymerization initiator 
     part B: macromonomer, reactive diluent, coinitiator and amine or dicarboxylic acid, dicarboxylic acid anhydride, diphenol, or dithiol, respectively. 
     The composition contains 1 to 99 mol-% of a macromonomer relative to to said monomers, preferably 10 to 90 mol-% of a macromonomer relative to to said monomers, most preferably 30 to 70 mol-% of a macromonomer relative to to said monomers. 
     The prepared adhesives, adhesive cements and composites are polymerizable in two different polymerization reactions, namely in a free-radical/photochemical and a thermal polymerization reaction which may run subsequently or simultaneously. In both cases interpenetrating networks or semi-IPNs were prepared depending on the comonomer used for the addition reaction namely if polyamines, primary monoamines, disecondary diamines or dicarboxylic acids, dicarboxylic acid anhydrides, diphenols or dithiols were used for epoxide-addition polymerization. The methacrylate networks and the epoxide networks and linear polymers, respectively are compatible. The invented polymer compositions exhibit advantageous mechanical properties and a small shrinkage during polymerization. 
     The invented polymer compositions may contain reactive diluents such as diethyleneglycoldimethacrylate, triethyleneglycoldimethacrylate, polypropyleneglycoldimethacrylate, methacrylate substituted spiroortho esters, glycerintrimethacrylate, furfurylmethacrylate, urethandimethacrylate, Bis-GMA in a content of 5 to 50 wt-%. 
     The invented polymer compositions may contain stabilisers such as hydroquinon or 2,6-di-tert.-butyl-p-cresol. 
     The invented polymer compositions may comprise redox-initiator systems such as azobisisobutyronitril, dibenzoyiperoxid/amine, Cu-acetylacetonate/Li-sulfinate, trialkylboranes or photo initiators such as benzoinmethylether, benzilketal, camphor quinon or acylphosphinoxides in contents of 0,1 to 3 wt-%. 
     When using the invented polymer compositions as composite, fillers can be mixed into the epoxidelmacromonomer or isocyanate/macromonomer matrix. As fillers were used inorganic glasses such as barium-alumosilicat glasses, silica gels, xero gels or inorganic compounds such as La 2  O 3 , ZrO 2 , BiPO 4 , CaWO 4 , BaWO 4 , SrF 2 , Bi 2  O 3  or organic fillers such as broken organic polymers. 
     The invented polymer compositions reveals interesting mechanical properties such as a high flexural and compressive strength, a low expansion, good adhesion to metal, glass and ceramics, a low shrinkage and a high radio-opacity between RO═2 and 10 mm/mm Al depending on the nature of the filler used. 
     When applying the invented dual curing material as adhesive, the viscosity and the adhesion properties of the material are adjustable through evaluation of the macromonomer and the chain length of these In many cases reactive diluents are necessary for the use of the invented materials 
     REFERENCE EXAMPLE 1 
     Preparation of macromonomer M-2 (n═1, R═--OC 6  H 4  --C(CH 3 ) 2  --C 6  H 4  O--, R 1  ═CH 3  --, R 3  ═C 6  H 4  COOC 4  H 9 ) 
     20,000 g (58,75 mmol) bisphenol-A diglycidyl ether, 5,058 g (58,75 mmol) methacrylic acid, 0,253 g triethylbenzylammoniumchlorid, 0,194 g 2,6-di-tert.-butyl-p-cresol (BHT), 7,747 g triethyleneglycoldimethacrylate and 5,677 g (29,38 mmol) p-amino-benzoic butyl ester were mixed and reacted for 16 hours at 80° C. In the IR-spectrum of the macromonomer no absorption of epoxide groups at 915 cm -1  was found. 
     REFERENCE EXAMPLE 2 
     Preparation of macromonomer M-3 (n═1, R═--OC 6  H 4  --C(CH 3 ) 2  --C 6  H 4  O--, R 1  ═CH 3  --, R 2  ═--(CH 2 ) 4  O(CH 2 ) 4  --, R 3  ═C 6  H 5  CH 2  --) 
     150,000 g (0,441 mol) bisphenol-A diglycidyl ether, 37,935 g (0,441 mol) methacrylic acid, 27000 g triethylbenzylammonium chloride, 1,115 g 2,6-di-tert.-butyl-pcresol (BHT) and 111,695 g ethoxylated Bis-GMA were homogeneously mixed under slow heating. The mixture was kept for two hours at 90° C. After this time 75,020 g (0,221 mol) N,N&#39;-dibenzyl-5-oxanonanediamine-1,9 were added to the mixture while stirring and was kept for additional two hours at 90° C. The obtained methacrylate terminated macromonomer is soluble in organic solvents such as chloroform, DMF and THF. In the IR-spectrum no absorption of epoxide groups at 915 and 3050 cm -1  was observed. A new absorption of ester groups was found at 1720 cm -1 . 
     REFERENCE EXAMPLE 3 
     Preparation of macromonomer M-5 (n═1, R═--OC 6  H 4  --C(CH 3 ) 2  --C 6  H 4  O--, R 1  ═CH 3  --, R 2  ═--(CH 2 ) 4  O(CH 2 ) 4  --, R 3  ═C 6  H 5  CH 2  --) 
     20,000 g (58,75 mmol) bisphenol-A diglycidyl ether and 40,012 g (117,50 mmol) N,N&#39;-dibenzyl-5-oxanonanediamine-1,9 were homogeneously mixed under slow heating. The mixture was kept for two hours at 90° C. After this time 16,704 g (117,50 mmol) 2,3-epoxypropyl methacrylate were added to the mixture while stirring and were kept for another two hours at 90° C. The obtained methacrylate terminated macromonomer is soluble in organic solvents such as chloroform, DMF and THF. In the IR-spectrum no absorption of epoxide groups at 915 and 3050 cm -1  were observed. 
     REFERENCE EXAMPLE 4 
     Preparation of macromonomer M-21 (n═1, R 1  ═CH 3  --, R 2  ═--CH 2  CH 2  --, R 4  ═--(CH 2 ) 2  O(CH 2 ) 2  O(CH 2 ) 2  --,) ##STR11## 
     15,000 g (67,790 mmol) isophorondiisocyanate, 6,179 g (33,895 mmol) 1,8-dimercapto-3,6-dioxaoctane, 8,822 g (67,790 mmol) hydroxyethylmethacrylate and 0,060 g BHT were homogeneously mixed and reacted for 8 h hours at 45° C. The obtained macromonomer does not show an absorption of the isocyanate group at 2200 cm -1  in the IR spectrum. 
    
    
     EXAMPLE 1-5 
     3,0 g (15,4 mmol) 3(4),8(9)-Bis(aminomethyl)tricyclo-5.2.1.0. 2 ,6 -decan TCD and 10,5 g (30,8 mmol) 2,2-Bis 4(2,3-epoxypropoxy)phenyl!propane DGEBA were mixed to give the epoxide-amine addition polymer AP. Different amounts (see table 1) of macromonomer M-5 (n═O, R═--OC 6  H 4  --C(CH 3 ) 2  --C 6  H 4  O--, R 1  ═CH 3  --, R 2  ═--(CH 2 ) 4  O(CH 2 ) 4  --, R 3  ═C 6  H 5  CH 2 ) N,N&#39;-Dibenzyl-N,N&#39;-bis-(2-hydroxy-3-methacryloyloxypropyl)-5-oxanonandiamin-1,9, and 0.5% photo initiator IRGACURE 651 (Ciba Geigy) were added and the parts thoroughly mixed. To remove gas bubbles the mixture was exposed to vacuum of an oil pump and then filled into moulds to prepare test samples for dynamic mechanic analysis (DMA). Methacrylate groups were polymerized upon exposure to UV light of a stroboscope UV lamp for 6 minutes. Then the samples were already stiff enough to be released from the mould. The polymerization of epoxide with amine was then completed by storing over night at 85° C. 
     The glass transition temperatures of the resulting materials were determined by differential scanning calorimetry (DSC) and the maximum of tan δ in DMA. Results are shown in table 1. Only one glass transition appears. Under scanning electron microscope phase separation is not being found (resolution 500 nm). 
     
                                           TABLE 1__________________________________________________________________________Composition and glass temperatures of IPN and homopolymers of M-5 and APoriginally weight-in quantity of                       ratio of                            Tg  TgDGEBA        TCD    M-5     M-5/AP                            (DSC)                                (DMA)Exampleg   mmol        g  mmol               g   mmol                       wt-% °C.                                °C.__________________________________________________________________________M-5  --  --  -- --  10,0                   16,0                       100/0                            10  181     2,00     5,88        0,57            2,94               25,70                   41,13                       90/10                             9  202     5,00    14,69        1,43            7,71               19,29                   30,87                       75/25                            37  363    10,50    30,84        3,00           15,42               13,50                   21,61                       50/50                            60  694    10,50    30,84        3,00           15,42                4,50                    7,20                       25/75                            98  1035    10,50    30,84        3,00           15,42                1,94                    3,11                       10/90                            140 125AP   10,50    30,84        3,00           15,42               --  --   0/100                            154 156__________________________________________________________________________ 
    
     EXAMPLE 6 (one-paste system) 
     3,000 g of macromonomer M-2 of reference example 1 and 1,142 g (3,35 mmol) bisphenol-A diglycidyl ether, 1,142 g (3,35 mmol) N,N&#39;-Dibenzyl-5-oxanonandiamine-1.9 and 0.02 g camphor quinon were homogeneously mixed and polymerized as described in example 1-5. The shrinkage of the photochemical polymerization is 0,68 vol-% and of the thermal addition polymerization 2,44 vol-%. 
     EXAMPLE 7 (one-paste system) 
     3,000 g of macromonomer M-2 of reference example 1 were homogeneously mixed with 1,142 g (3,35 mmol) bisphenol-A diglycidyl ether, 0,806 g (3,35 mmol) N,N&#39;-di-benzylethylenediamine and 0,02 g camphor quinon and polymerized as described in example 1-5. The shrinkage of the photochemical polymerization is 0,56 vol-% and of the thermal addition polymerization 3,43 vol-%. 
     EXAMPLE 8 (one-paste system) 
     3,000 g of macromonomer M-2 of reference example 1 were homogeneously mixed with 1,142 g (3,35 mmol) bisphenol-A diglycidyl ether, 0,176 g (1,34 mmol) N,N-dipropylenetriamine and 0,02 g camphor quinon and polymerized as described in example 1-5. A shrinkage of dV═3,5%, dV═1,8% was measured which is caused by the photochemical step and dV=1,7% which is caused by the thermal epoxide-amine addition polymerization. 
     EXAMPLE 9 (two-paste system) 
     Part A) 
     2,000 g of macromonomer M-2 of reference example 1 were homogeneously mixed with 4,246 g (3,35 mmol) Araldit-F, 0,054 g dibenzoylperoxide 19,500 g of a mixture of CaWO 4  /ZrO 2  (4:1) and 0,100 g aerosil. 
     Part B) 
     2,000 g of macromonomer M-2 of reference example 1 were homogeneously mixed with 1,086 g (5,59 mmol) 3(4),8(9)-bis(amino methyl)-tricyclo-5.2.1.0. 2 ,6 -decan, 0,054 g N,N-bis(β-hydroxyethyl)-p-aminobenzoic acid ethylester, 9,441 g of a mixture of CaWO 4  /ZrO 2  (4:1) and 0,100 g aerosil. 
     Parts A and B were mixed immediately before use in a weight ratio of 2:1 and polymerized for 10 minutes at 37° C. The shrinkage was measured as follows: dV=0,99 vol.-% and the radio-opacity RO═8,3 mm/mm Al. 
     EXAMPLE 10 (two-paste system) 
     Part A) 
     10,000 g of macromonomer M-3 of reference example 2 were homogeneously mixed with 7,010 g (20,60 mmol) Araldit MY-790, 0,010 g dibenzoylperoxide and 23,000 g Barium-Alumosilicate-glass and 0,100 g aerosil. 
     Part B) 
     2,000 g of macromonomer M-3 of reference example 2 were homogeneously mixed with 2,001 g (10,30 mmol) 3(4),8(9)-bis(amino methyl)-tricyclo-5.2.1.0. 2 ,6 -decan, 0,015 g N,N-bis(β-hydroxyethyl)-p-aminobenzoic acid ethyl ester, 22,000 g Barium-Alumo-silicate-glass and 0,100 g aerosil. 
     Parts A and B were mixed immediately before use in a weight ratio of 1:0,706 and polymerized at 37° C. for 10 minutes. The shrinkage was measured of dV=1,55 vol.-%. 
     EXAMPLE 11 (two-paste system) 
     Part A) 
     10,000 g of macromonomer M-5 of reference example 3 were homogeneously mixed with 7,010 g (20,60 mmol) Araldit MY-790 and 0,010 g dibenzoylperoxide. 
     Part B) 
     10,000 g of macromonomer M-5 of reference example 3 were homogeneously mixed with 2,001 g (10,30 mmol) 3(4),8(9)-bis(amino methyl)-tricyclo-5.2.1.0. 2 ,6 -decan and 0,015 g N,N-bis(β-hydroxy-ethyl)-p-aminobenzoic acid ethyl ester. 
     Parts A and B were mixed immediately before use in a weight ratio of 1:0,707. The first polymerization step occurs during radiation at λ&gt;365 nm for 360 seconds and the second step as thermal epoxide-amine polymerization at 85° C. for 16 hours. The following values were measured: Tg=69° C., ΔV=1,75 vol.-%. 
     EXAMPLE 12 (one-paste system) 
     8,650 g (7,25 mmol) of macromonomer M-5 of reference example 3 (R═--OC 6  H 4  --C(CH 3 ) 2  --C 6  H 4  O--, R 1  ═CH 3  --, R 2  ═--(CH 2 ) 4  O (CH 2 ) 4  --, R 3  ═C 6  H 5  CH 2  --), 3,707 g triethyleneglycoldimethacrylate, 1,35 g (3,62 mmol) 3(4),8(9)-Bis(aminomethyl)tricyclo-5.2.1.0. 2 ,6 -decan, 2,467 g (7,25 mmol) bisphenol-A diglycidyl ether, 0,124 g camphor quinon and 0,124 g N,N-bis(,-hydroxy-ethyl)-p-toluidine were mixed homogenously immeadely befor use. A smal layer of this mixture was put on a ceramic tooth and polymerized with visible light for 40 seconds. Thereafter a composite TP.H (De Trey Dentsply) was applied to this layer and polymerized for 40 seconds. Then material was reacted for 24 hours at 37° C. After this time the adhesion of the material is 7,4±1,3 MPa. 
     Comparison example (Acta Polym. 38 (1987) 547) 
     7,000 g (13,66 mmol) Bis-GMA, 3,000 g triethyleneglycoldimethacrylate, 5,0960 g (14,97 mmol) bisphenol-A diglycidyl ether, 4,917 g (14,97 mmol) N,N&#39;-Dibenzyl-3,6-dioxactanediamine-1,8 (Acta Polym. 38 (1987) 547 and DD 226731), 0,050 g camphor quinon and 0,0050 g N,N-bis(β-hydroxy-ethyl)-p-toluidine were mixed homogenously immeadely befor use. A smal layer of this mixture was put on a ceramic tooth and polymerized with visible light for 40 seconds. Thereafter a composite TP. H (De Trey Dentsply) was applied to this layer and polymerized for 40 seconds. Then the material was reacted in water for 24 hours at 37° C. After this time the adhesion of the material is 4,1±1,2 MPa. 
     EXAMPLE 13 (two-paste system) 
     5,000 g (7,532 mmol) of M-21, 1,373 g (7,532 mmol) 1,8-dimercapto-3,6-dioxaoctane, 2,564 g (7,532 mmol) bisphenol-A diglycidyl ether, 0,089 g camphor quinon and 0,089 g N,N-bis(β-hydroxy-ethyl)-p-toluidine were mixed homogenously immeadely befor use. A smal layer of this mixture was put on a ceramic tooth and polymerized with visible light for 40 seconds. Thereafter a composite TP.H (De Trey Dentsply) was applied to this layer and polymerized for 40 seconds. Then the material was reacted in water for 24 hours at 37° C. After this time the adhesion of the material is 6,9±0,7 MPa.