DENTAL COMPOSITION

Abstract

The present invention is related to a dental composition comprising: (a) at least one polymerizable monomer having at least one ethylenically unsaturated group; (b) a radical initiator system comprising (i) a photosensitizer having an absorption maximum ranging from 400 nm to 800 nm; (ii) a coinitiator; and (iii) a compound of the following formula (1):

##STR00001## wherein R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; R.sup.3 and R.sup.4, which may be the same or different, independently represent a hydrogen atom, or a C.sub.1-6 alkyl group, or R.sup.3 and R.sup.4 may represent a bond so that the carbon atoms to which R.sup.3 and R.sup.4 are bonded are linked by a double bond; R.sup.5 and R.sup.6, which may be the same or different, independently represent a hydrogen atom, or a C.sub.1-6 alkyl group, or R.sup.5 and R.sup.6 may represent a bond so that the carbon atoms to which R.sup.5 and R.sup.6 are bonded are linked by a double bond; L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; n and m, independently are integers of 1 to 6.

Claims

1. Dental composition comprising: (a) at least one polymerizable monomer having at least one ethylenically unsaturated group; and (b) a radical initiator system comprising (i) a photosensitizer having an absorption maximum ranging from 400 nm to 800 nm; and (ii) a coinitiator; characterized in that the radical initiator system further comprises (iii) a compound of the following formula (I): ##STR00009## wherein R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; R.sup.3 and R.sup.4, which may be the same or different, independently represent a hydrogen atom, or a C.sub.1-6 alkyl group, or R.sup.3 and R.sup.4 may represent a bond so that the carbon atoms to which R.sup.3 and R.sup.4 are bonded are linked by a double bond; s R.sup.5 and R.sup.6, which may be the same or different, independently represent a hydrogen atom, or a C.sub.1-6 alkyl group, or R.sup.5 and R.sup.6 may represent a bond so that the carbon atoms to which R.sup.5 and R.sup.6 are bonded are linked by a double bond; L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; n and m, independently are integers of 1 to 6.

2. Dental composition according to claim 1, characterized in that the radical initiator system comprises an 1,2-diketone compound as photosensitizer; and a tertiary amine, an aromatic phosphine, a germanium hydride, a sulfinic acid salt or a sulfonic acid salt as coinitiator.

3. Dental composition according to claim 1 or 2, characterized in that the radical initiator system comprises camphorquinone as photosensitizer; a tertiary amine as coinitiator; and a compound of the following formula (Ia): ##STR00010## wherein R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; n and m, independently are integers of 1 to 6.

4. Dental composition according to one of the preceding claims, characterized in that the radical initiator system comprises camphorquinone as photosensitizer; a tertiary amine as coinitiator; and a compound of the following formula (Ib): ##STR00011## wherein R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; n and m, independently are integers of 1 to 6.

5. Dental composition according to one of the preceding claims, characterized in that the radical initiator system comprises camphorquinone as photosensitizer; a tertiary amine as coinitiator; and a compound of the following formula (Ic): ##STR00012##

6. Dental composition according to any one of the preceding claims, characterized in that the ratio of the amount of the photosensitizer to the amount of the compound of the formula (I), (Ia), (Ib) or (Ic) is ranging from 200:1 to 1:1; preferably ranging from 100:1 to 1:1; and more preferably ranging from 50:1 to 1:1.

7. Dental composition according to any one of the preceding claims, characterized in that the amount of the compound of the formula (I), (Ia), (Ib) or (Ic) is ranging from 0.01 to 1.2 percent by weight, preferably ranging from 0.02 to 0.9 percent by weight, and more preferably ranging from 0.03 to 0.7 percent by weight, based on the total weight of the dental composition.

8. Dental composition according to any one of the preceding claims, characterized in that the amount of the photosensitizer is ranging from 0.1 to 3 percent by weight, preferably ranging from 0.3 to 2.4 percent by weight, and more preferably ranging from 0.6 to 1.6 percent by weight, based on the total weight of the dental composition.

9. Dental composition according to one of the preceding claims characterized in that the dental composition further comprises an additive selected from iodonium salts, phosphonium salts, and sulfonium salts; preferably wherein said additive is an iodonium salt.

10. Dental composition according to claim 9 characterized in that the amount of the additive is ranging from 0.01 to 3 percent by weight, preferably ranging from 0.25 to 2 percent by weight, and more preferably ranging from 0.5 to 1.2 percent by weight, based on the total weight of the dental composition.

11. Dental composition according to one of the preceding claims characterized in that the amount of the radical initiator system is ranging from 0.1 to 10 percent by weight, preferably ranging from 0.7 to 7 percent by weight, and more preferably ranging from 1.5 to 4.5 percent by weight, based on the total weight of the dental composition.

12. The dental composition according to any one of the preceding claims characterized in that the amount of the coinitiator is ranging from 0.1 to 3 percent by weight, preferably ranging from 0.3 to 2.4 percent by weight, and more preferably ranging from 0.5 to 1.5 percent by weight, based on the total weight of the dental composition.

13. Dental composition according to any one of the preceding claims, characterized in that the dental composition is selected from a dental adhesive composition, a dental composite, a root canal filling composition, a dental pit and fissure sealer, a dental primer, a dental sealant, a dental varnish, a dental infiltrant or a resin modified dental cement composition.

14. Use of a compound of the formula (I), (Ia), (Ib) or (Ic) for preparing a dental composition according to any one of the preceding claims.

15. Use of a compound of the formula (I), (Ia), (Ib) or (Ic) for the treatment or prevention of dental disease by restoring hard dental tissue with a dental composition according to any one of the preceding claims 1 to 13.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0038] For a more complete understanding of the present invention, reference is made to the following Detailed Description of the Invention considered in conjunction with the accompanying figures, in which:

[0039] FIG. 1 shows the photopolymerization profiles of reactive functions in the presence of a fixed amount of camphorquinone as photosensitizer and different amounts of curcumin.

[0040] FIG. 2 shows the photopolymerization profiles of reactive functions in the presence of different amounts of camphorquinone as photosensitizer and a fixed amount of curcumin.

[0041] FIG. 3 shows the photopolymerization profiles of reactive functions in the presence of camphorquinone as photosensitizer with and without the presence of curcumin.

DETAILED DESCRIPTION OF THE INVENTION

[0042] The term “alkyl”, unless otherwise specified, refers to a monoradical branched or unbranched saturated hydrocarbon chain having from 1 to 18 carbon atoms. This term can be exemplified by groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-decyl, dodecyl, tetradecyl, and the like.

[0043] The term “alkoxy group”, unless otherwise specified refers to a monoradical branched or unbranched saturated hydrocarbon chain having from 1 to 18 carbon atoms, wherein at least one carbon atom of such an alkoxy group is substituted by one oxygen atom. Such an alkoxy group is attached by said at least one oxygen atom to a carbon atom of a chemical compound. This term can be exemplified by groups such as methoxy, ethoxy, and the like. That means the term “alkoxy group” is defined in the context of the present invention as any chemist would understand it based on common chemical knowledge.

[0044] The term “alkylene”, unless otherwise specified refers to a linear saturated divalent hydrocarbon radical of one to four carbon atoms or a branched saturated divalent hydrocarbon radical of three to four carbon atoms, e.g., methylene, ethylene, 2,2-dimethylethylene, propylene, 2-methylpropylene, butylene and the like, preferably methylene, ethylene, or propylene.

[0045] The term “aryl” refers to C.sub.6-C.sub.10-membered aromatic, heterocyclic, fused aromatic, fused heterocyclic, biaromatic, or bihetereocyclic ring systems. Broadly defined, “aryl”, as used herein, includes 5-, 6-, 7-, 8-, 9-, and 10-membered single-ring aromatic groups that may include from zero to four heteroatoms, for example, benzene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine, pyrimidine, and the like. Those “aryl” groups having heteroatoms in the ring structure may also be referred to as “heteroaryl” or “heterocyles” or “heteroaromatics”. The aromatic ring can be substituted at one or more ring positions with one or more substituents including, but not limited to, halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl, amino (or quaternized amino), nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moieties, —CF3, —CN, and combinations thereof.

[0046] The term “cycloalkyl” refers to monocyclic or polycyclic cycloalkyl radical. Examples of monocyclic acycloakyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycdoheptyl, and cyclooctyl. Examples of polycyclic cycloalkyl radical include, for example admantyl, norbomyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl, tricyclo[5.2.1.02,6]decyl and the like.

[0047] The term “(meth)acrylate” in the context of the present disclosure is meant to refer to the acrylate as well as to the corresponding methacrylate.

[0048] The term “(meth)acrylamide” in the context of the present disclosure is meant to include acrylamide and methacrylamide.

[0049] The term “polymerizable monomer” in the context of the present disclosure means any monomer capable of radical polymerization. The polymerizable monomer includes at least one ethylenically unsaturated groups. The at least one ethylenically unsaturated groups include vinyl, allyl, acryl, methacryl, and styryl.

[0050] The term “a polymerizable monomer having at least one ethylenically unsaturated group” and “ethylenically unsaturated monomers” may be used interchangeably.

[0051] The term “radical initiator system” in the context of the present disclosure means any system comprising a photosensitizer and at least one coinitiator forming free radicals when activate by thermal or light and/or ambient redox conditions, whereby polymerization of polymerizable monomer is initiated.

[0052] The term “coinitiator” in the context of the present disclosure means a compound that does not essentially absorb when exposed with UV radiation or visible light but forms free radicals together with the photosensitizers used according to the present disclosure.

[0053] The term “photosensitizer” in the context of the present disclosure means a compound which can absorb radiation of a wavelength in the range of 400 to 800 nm, when it is exposed but which cannot by itself, i.e. without the addition of coinitiators, form free radicals. Photosensitizers used in the present disclosure have to be capable of interacting with the coinitiators used in the present disclosure. The terms “photosensitizer” and “photoinitiators” are equivalents in the context of the present invention.

The Polymerizable Monomers

[0054] The dental composition of the present disclosure comprises one or more polymerizable monomers having at least one ethylenically unsaturated group.

[0055] Polymerizable monomers may be acrylates, methacrylates, ethylenically unsaturated compounds, carboxyl group-containing unsaturated monomers, C2-8 hydroxyl alkyl esters of (meth)acrylic acid, C1-24 alkyl esters or cycloalkyl esters of (meth)acrylic acid, C2-18 alkoxyalkyl esters of (meth)acrylic acid, olefins or diene compounds, monoesters/diesters, monoethers, adducts, vinyl monomer, styryl monomer, TPH resin, SDR Resin, PBA resins and/or BPA-free resins.

[0056] Examples of specific acrylate monomer include, but are not limited to, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, glycidyl acrylate, glycerol mono- and di-acrylate, ethylene glycol diacrylate, polyethyleneglycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, mono-, di-, tri-acrylate, mono-, di-, tri-, and tetra-acrylates of pentaerythritol and dipentaerythritol, 1,3-butanediol diacrylate, 1,4-butanedioldiacrylate, 1,6-hexanediol diacrylate, 2,2′-bis[3(4-phenoxy)-2-hydroxypropane-1-acrylate]propane, 2,2′-bis(4-acryloxyphenyl)propane, 2,2′-bis[4(2-hydroxy-3-acryloxy-phenyl)]propane, 2,2′-bis(4-acryloxyethoxyphenyl)propane, 2,2′-bis(4-acryloxypropoxyphenyl)propane,2,2′-bis(4-acryloxydiethoxyphenyl)propane, 2′-bis[3(4-phenoxy)-2-hydroxypropane-1-acrylate]propane, and dipentaerthritol pentaacrylate esters.

[0057] Examples of specific conventional methacrylate monomer include, but are not limited to, methyl methacrylates, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, glycidyl methacrylate, the diglycidyl methacrylate of bis-phenol A (2,2-Bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane) (BisGMA), 4,4,6,16 (or 4,6,6,16)-tetramethyl-10,15-dioxo-11,14-dioxa-2,9-diazaheptadec-16-enoicacid 2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl ester (CAS no. 72869-86-4)(UDMA), glycerol mono- and dimethacrylate, ethyleneglycol dimethacrylate, polyethyleneglycol dimethacrylate, triethylene glycol dimethacrylate (TEGDMA), neopentylglycol dimethacrylate, trimethyloi propane trimethacrylate, mono-, di-, tri-, and tetra-methacrylates of pentaerythrital and dipentaerythritol, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, Bis[2-(methacryloyloxy)ethyl]phosphate (BisMEP),1,6-hexanediol dimethacrylate, 2-2′-bis(4-methacryloxyphenyl)propane, 2,2-bis[4(2-hydroxy-3-methacryloxy-phenyl)]propane, 2,2′-bis(4-methacryloxyethoxyphenyl)propane, 2,2′-bis(4-methacryloxypropoxyphenyl)propene, 2,2′-bis(4-methacryloxydiethoxyphenyl)propane, 2,2′-bis[3(4-phenoxy)-2-hydroxypropane-1-methacrylate]propane, di-2-methacryloyloxethyl hexamethylene dicarbamate, di-2-methacryloyloxyethyl trimethylhexamethylene dicarbamate, di-2-methacryloyl oxyethyl dimethylbenzene dicarbamate, methylene-bis-2-methacryloxyetyl-cyclohexyl carbamate, di-2-methacryloxyethyl-dimethylcyclohexane dicarbamate, methylene-bis-2-methacryloxyethyl-4-cyclohexyl carbamate, di-1-methyl-2-methacryloxyethyl-trimethyl-hexamethylene dicarbamate, di-1-Methyl-2-methacryloxyethyl-dimethylbenzene dicarbamate, di-1-methyl-2-methacryloxyethyl-dimethylcyclohexane dicarbamate, methylenebis-1-methyl-2-methacryloxyethyl-4-cyclohexyl carbamate, di-1-chloromethyl-2-methacryloxyethyl-hexamethylene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-trimethylhexamethylene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylbenzene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylcyclohexane dicarbamate, methylene-bis-2-methacryloxyethyl-4-cyclohexyl carbamate, di-1-methyl-2-methacryloxyethyl-hexamethylene dicarbamate, di-1-methyl-2-methacryloxyethyl-trimethylhexamethylene dicarbamate, di-1-methyl-2-methacryloxyethyl-dimethylbenzene dicarbamate, di-1-methyl-2-methacryloxyethyl-dimethylcyclohexane dicarbamate, methylene-bis-1-methyl-2-methacryloxyethyl-4-cyclohexyl carbamate, di-1-chloromethyl-2-methacryloxyethyl-hexamethylene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-trimethylhexamethylene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylbenzene dicarbamate, di-1-chloromethyl-2-methacryloxyethyl-dimethylcyclohexane dicarbamate, and methylene-bis-1-chloromethyl-2-methacryloxyethyl-4-cyclohexyl carbamate.

[0058] Examples of ethylenically unsaturated compounds include, but are not limited to, acrylic acid esters, methacrylic acid esters, hydroxy-functional acrylic acid esters, hydroxy-functional methacrylic acid esters, halogen, and hydroxy containing methacrylic acid esters and combinations thereof. Such free radically polymerizable compound include n-, sec-, or t-buty methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octylmethacrylate, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, stearyl(meth)acrylate, allyl(meth)acrylate, glycerol tri(meth)acrylate, diethyleneglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,2,4-butanetriol tri(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, sorbitol hex(meth)acrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane, bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, ethoxylated bisphenol A di(meth)acrylate, and trishydroxyethyl-isocyanurate tri(meth)acrylate; urethane (meth)acrylates; ((di)urethane dimethacrylate), the bis-(meth)acrylates of polyethylene glycols, and chlorine-, bromine-, fluorine-, and hydroxyl group containing monomers, for example, 3-chloro-2-hydroxylpropyl (meth)acrylate, and reaction product of Bisphenol-A-Glycidylmethacryiate (BisGMA) and a hexamethylene diisocyanate (HMDI).

[0059] Examples of carboxyl group-containing unsaturated monomers include, but are not limited to, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. Examples of C2-8 hydroxyl alkyl esters of (meth)acrylic acid include, but are not limited to, 2-hydroxylethyl (meth)acrylate, 2-hydroxylpropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate. Examples of C2-18 alkoxyalkyl esters of (meth)acrylic acid include, but are not limited to, methoxybutyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, and ethoxybutyl methacrylate. Specifically, acrylate and methacrylates may be

##STR00003##

[0060] Specifically, methacrylamide may be bis-(meth)acrylamides, such as N,N′-diallyl-1,4-bisacrylamido-(2E)-but-2-en (BAABE) having the structural formula

##STR00004## [0061] and/or

[0062] N,N′-diethyl-1,3-bisacrylamido-propan (BADEP) having the structural formula

##STR00005##

A Radical Initiator System

[0063] The dental composition of the present disclosure includes a radical initiator system. Said radical initiator system includes at least one photoinitiator being in the form of a binary or a tertiary system. A binary system includes at least a photosensitizer and a coinitiator. A tertiary system comprises additionally an iodonium, sulfonium or phosphonium salt.

[0064] The present invention is based on the recognition that a compound of formula (I), particularly of a formula (Ia), (Ib) or (Ic), shows different photochemical properties in the ground state and excited states.

[0065] Furthermore, it is surprisingly found that a dental composition comprising a compound of formula (I), particularly of a formula (Ia), (Ib) or (Ic), requires only reduced amount of photosensitizer for curing reaction with a better polymerization efficiency in terms of conversion rate and curing rate. Therefore, leaching problems of the unreacted photoinitiator may also have been reduced or avoided.

[0066] Moreover, the present invention is also based on the recognition that a compound of formula (I), particularly of a formula (Ia), (Ib) or (Ic), has excellent photobleaching properties. Therefore, discoloration take place upon the curing of the dental composition, so that a dental practitioner can observe the onset of curing based on the color change in the dental composition. Besides, the singlet oxygen generated by the compound of formula (I) can also react with other chromophores, such as unreacted photoinitiator, in the composition and lead to its photo-bleaching and/or discoloration. Consequently, the cured dental composition has a color that is close to the natural teeth and does not have coloration problem.

[0067] In a preferred embodiment, the radical initiator system comprises an 1,2-diketone compound as photosensitizer, and a tertiary amine, an aromatic phosphine, a germanium hydride, a sulfinic acid salt or a sulfonic acid salt as coinitiator.

[0068] Suitable 1,2-diketone compounds may be selected from the group consisting of camphorquinone, benzil, 2,2′-3 3- and 4,4′-dihydroxylbenzil, 2,3-butanedione, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione, 2,3-heptanedione, 3,4-heptanedione, 2,3-octanedione, 4,5-octanedionefuril, biacetyl, 1,2-cyclohexanedione, 1,2-naphthaquinone, and acenaphthaquinone. Such suitable 1,2-diketone compounds preferably absorb light within a range of about 400 nm to about 520 nm, preferably about 450 nm to about 500 nm.

[0069] Suitable tertiary amines may be selected from the group consisting of trialkanolamine, 4-N,N-dialkylaminobenzonitrile, alkyl N,N-dialkylaminobenzoate, alkyl N,N-dialkylaminobenzoate, N,N-dialkylaminoethyl alkylacrylate and isoamyl 4-N,N-dialkylaminobenzoate, N,N-dialkylaniline, N,N-dialkyltoluidine, N,N-dialkylotoluidine, dialkylaminoanisole, 1 or 2-dialkylaminonaphthalene.

[0070] In particular, the tertiary amine may be selected from the group consisting of triethanolamine, alkyl 4-N,N-dialkylaminobenzoate, ethyl 4-N,N-dialkylaminobenzoate, 4-N,N-dialkylaminoethyl methacrylate, isoamyl 4-N,N-dialkylaminobenzoate and 4,4′-N,N-bis(dialkylamino)benzophenone.

[0071] Herein, the alkyl group may represent a straight chain, branched or cyclic alkyl group. Furthermore, if more than one alkyl group is comprised, the alkyl groups may be the same or different, preferably they are the same. Preferably, the alkyl group is a C1-6 alkyl group, more preferably a C1-4 alkyl group. Most preferably, the alkyl group is a methyl or ethyl group.

[0072] Particular preferred tertiary amines may be selected from the group consisting of triethanolamine, 4-N,N-dimethylaminobenzonitrile, methyl N,N-dimethylaminobenzoate, ethyl N,N-dimethylaminobenzoate (DMABE), N,N-dimethylaminoethyl methacrylate and isoamyl 4-N,N-dimethylaminobenzoate, N,N-dimethylaniline, N,N-dimethyltoluidine, N,N-diethanoltoluidine, dimethylaminoanisole, 1 or 2-dimethylaminonaphthalene. More preferred tertiary amines may be selected from the group consisting of triethanolamine, methyl 4-N,N-dimethylaminobenzoate, ethyl 4-N,N-dimethylaminobenzoate (DMABE), 4-N,N-dimethylaminoethyl methacrylate, isoamyl 4-N,N-dimethylaminobenzoate and 4,4′-N,N-bis(dimethylamino)benzophenone. Most preferably, the tertiary amine coinitiator is ethyl 4-N,N-dimethylaminobenzoate (DMABE) or 4-dimethylaminobenzonitrile (DMABN).

[0073] In a further embodiment, the radical initiator system comprises camphorquinone as photosensitizer a tertiary amine as coinitiator; and a compound of the following formula (Ia):

##STR00006## [0074] wherein [0075] R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; [0076] L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6alkoxy group; [0077] n and m, independently are integers of 1 to 6.

[0078] In a further embodiment, the radical initiator system comprises camphorquinone as photosensitize; a tertiary amine as coinitiator; and a compound of the following formula (Ib):

##STR00007## [0079] wherein [0080] R.sup.1 and R.sup.2, which may be the same or different, independently represent a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; [0081] L represents a single bond or a group —CRH—, wherein R may be a hydrogen atom, a C.sub.1-6 alkyl group, or a C.sub.1-6 alkoxy group; [0082] n and m, independently are integers of 1 to 6.

[0083] In a further embodiment, the radical initiator system comprises camphorquinone as photosensitizer, a tertiary amine as coinitiator; and a compound of the following formula (Ic):

##STR00008##

[0084] Said compound (Ic) is known as curcumin (herein also referred to as CCM).

[0085] In one embodiment, the ratio of the amount of the photosensitizer to the amount of the compound of the formula (I), (Ia), (Ib) or (Ic) is ranging from 200:1 to 1:1; preferably ranging from 100:1 to 1:1; and more preferably ranging from 50:1 to 1:1.

[0086] In one embodiment, the amount of the compound of the formula (I), (Ia), (Ib) or (Ic) is ranging from 0.01 to 1.2 percent by weight, preferably ranging from 0.02 to 0.9 percent by weight, and more preferably ranging from 0.03 to 0.7 percent by weight, based on the total weight of the dental composition.

[0087] In one embodiment, the amount of the photosensitizer is ranging from 0.1 to 3 percent by weight, preferably ranging from 0.3 to 2.4 percent by weight, and more preferably ranging from 0.6 to 1.6 percent by weight, based on the total weight of the dental composition.

[0088] In another preferred embodiment, the dental composition further comprises an additive selected from iodonium salts, phosphonium salts, and sulfonium salts; preferably wherein said additive is an iodonium salt.

[0089] In particular, said additive is selected from diaryl iodonium salts, triaryl sulfonium salts, and tetraaryl or tetraalkyl phosphonium salts.

[0090] For example, diaryl iodonium salt may be selected from the group consisting of (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodonium hexafluoroantimonate, include (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodonium tetrafluoroborate, diphenyliodonium (DPI) tetrafluoroborate, di(4-methylphenyl)iodonium (Me2-DPI) tetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate, di(4-heptylphenyl)iodonium tetrafluoroborate, di(3-nitrophenyl)iodonium hexafluorophosphate, di(4-chlorophenyl)iodonium hexafluorophosphate, di(naphthyl)iodonium tetrafluoroborate, di(4-trifluoromethylphenyl)iodonium tetrafluoroborate, DPI hexafluorophosphate, Me2-DPI hexafluorophosphate; DPI hexafluoroarsenate, di(4-phenoxyphenyl)iodonium tetrafluoroborate, phenyl-2-thienyliodonium hexafluorophosphate, 3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate, DPI hexafluoroantimonate, 2,7-DPI tetrafluoroborate, di(2,4-dichlorophenyl)iodonium hexafluorophosphate, di(4-bromophenyl)iodonium hexafluorophosphate, di(4-methoxyphenyl)iodonium hexafluorophosphate, di(3-carboxyphenyl)iodonium hexafluorophosphate, di(3-methoxycarbonylphenyl)iodonium hexafluorophosphate, di(3-methoxysulfonylphenyl)iodonium hexafluorophosphate, Bis-(4-t-butylphenyl)iodonium hexafluorophosphate (SC938), di(4-acetamidophenyl)iodonium hexafluorophosphate, di(2-benzothienyl)iodonium hexafluorophosphate, and DPI hexafluorophosphate.

[0091] Particularly preferred diaryl iodonium compounds include diphenyliodonium (DPI) hexafluorophosphate, di(4-methylphenyliodonium (Me2-DPI) hexafluorophosphate, diaryliodonium hexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodonium hexafluoroantimonate. (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate (IrgacureV® 250, commercial product available from BASF SE), (4-methylphenyl)[4-(2-methylpropyl) phenyl] iodonium tetrafluoroborate, 4-octyloxyphenyl phenyliodonium hexafluoroantimonate, Bis-(4-t-butylphenyl)-iodonium hexafluorophosphate (SC938), 4-(2-hydroxytetradecyloxyphenyl)phenyliodonium hexafluoroantimonate, and 4-isopropyl-4′-methyldiphenyliodonium borate.

[0092] According to a particularly preferred embodiment, the iodonium compound is (Me2-DPI) hexafluorophosphate or Bis-(4-t-butylphenyl)-iodonium hexafluorophosphate (SC938).

[0093] A preferred triaryl sulfonium salt is S-(phenyl)thianthrenium hexafluorophosphate.

[0094] Particularly preferred phosphonium salts are the tetraalkyl phosphonium salts tetrakis-(hydroxymethyl)-phosphonium (THP) salt or a tetrakis-(hydroxymethyl)-phosphonium hydroxide (THPOH) salt, wherein the anion of the tetraalkyl phosphonium salt is selected from the group consisting of formate, acetate, phosphate, sulphate, fluoride, chloride, bromide and iodide.

[0095] In a preferred embodiment thereof, the amount of the additive is ranging from 0.01 to 3 percent by weight, preferably ranging from 0.25 to 2 percent by weight, and more preferably ranging from 0.5 to 1.2 percent by weight, based on the total weight of the dental composition.

[0096] In one embodiment, the amount of the radical initiator system is ranging from 0.1 to 10 percent by weight, preferably ranging from 0.7 to 7 percent by weight, and more preferably ranging from 1.5 to 4.5 percent by weight, based on the total weight of the dental composition.

[0097] In one embodiment, the amount of the coinitiator is ranging from 0.1 to 3 percent by weight, preferably ranging from 0.3 to 2.4 percent by weight, and more preferably ranging from 0.5 to 1.5 percent by weight, based on the total weight of the dental composition.

[0098] In one embodiment, the dental composition is selected from a dental adhesive composition, a dental composite, a root canal filling composition, a dental pit and fissure sealer, a dental primer, a dental sealant, a dental varnish, a dental infiltrant or a resin modified dental cement composition.

[0099] The present invention also provides a use of a compound of the formula (I), (Ia), (Ib) or (Ic) for preparing a dental composition according to the present invention.

[0100] Additionally, the present invention also provides a use of a compound of the formula (I), (Ia), (Ib) or (Ic) for the treatment or prevention of dental disease by restoring hard dental tissue with a dental composition according to the present invention.

[0101] The present invention thus addresses the problem of improving known dental compositions having a radical initiator system comprising a photosensitizer and a coinitiator, which allows to significantly decrease the initially required photosensitizer (such as CQ) concentration without a significant loss of polymerization efficiency and without resulting in yellow-colored adhesive layers after curing (caused by unreacted photoinitiator).

[0102] The following non-limiting examples are provided to illustrate embodiments of the present invention and to facilitate understanding of the invention but are not intended to limit the scope of the invention, which is defined by the claims appended hereto.

Example 1

[0103] The polymerization of a Prime&Bond Active liquid in presence of CQ/CCM/DMABN/SC938 as radical initiator system has been investigated. Herein, different amounts of curcumin (CCM) has been used while keeping the amounts of CQ, DMABN and SC938 constant (s.a. FIG. 1).

[0104] Herein, FIG. 1 shows the respective photopolymerization profiles of reactive functions in the presence of a fixed amount of camphorquinone as photosensitizer and different amounts of curcumin (under air; SmartLite Focus 300 mW.Math.cm-2, in monomer Prime&Bond Active, the irradiation starts at t=5 s till t=120 s, thickness=15 μm). [0105] 1. CQ/CCM/DMABN/SC938 (1/0.5/1/1% w/w) [0106] 2. CQ/CCM/DMABN/SC938 (1/0.2/11/1% w/w) [0107] 3. CQ/CCM/DMABN/SC938 (1/0.1/1/1% w/w) [0108] 4. CQ/CCM/DMABN/SC938 (1/0.05/1/1% w/w) [0109] 5. CQ/DMABN/Me2-DPI as reference system (1.55/0.65/0.75% w/w).

[0110] Remarkably, the performances of the system CQ/CCM/DMABN/SC938 to initiate the radical polymerization of Prime&Bond Active as dental resin upon irradiation by a blue dental LED light (SmartLite Focus; 300 mW.Math.cm.sup.2) overcome the performance of the reference system CQ/DMABN/Me2-DPI in the same conditions, showing the role and effect of CCM as photoinitiator when combined with camphorquinone (s.a. FIG. 1).

Example 2

[0111] As CCM was proposed as a new additive when combined with CQ, it is also possible to decrease the amount of CQ by adding CCM while keeping the same polymerization performances. For example, the polymerization of Prime&Bond Active liquid in presence of CQ/CCM/DMABN/SC938 as radical initiator system comprising different amounts of CQ is shown in FIG. 2.

[0112] FIG. 2 shows the photopolymenzation profiles of reactive functions in the presence of camphorquinone as photoinitiator (under air; SmartLite Focus 300 mW.Math.cm-2, in monomer Prime&Bond Active, the irradiation starts at t=5 s till t=120 s, thickness=15 μm) [0113] 1. CQ/CCM/DMABN/SC938 (1.55/0.05/0.65/0.75% w/w); [0114] 2. CQ/CCM/DMABN/SC938 (1.00/0.0510.6510.75% w/w); [0115] 3. CQ/CCM/DMABN/SC938 (0.7/0.05/0.65/0.75% w/w); [0116] 4. CQ/DMABN/Me2-DPI as reference system (1.55/0.65/0.75% w/w).

[0117] Remarkably, the amount of CQ can be reduced from 1.55 to 0.7% in presence of 0.05% of CCM while maintaining the same photopolymerization performances as for the reference CQ/DMABN/Me2-DPI (1.55/0.6510.75% w/w).

Example 3

[0118] CCM can be used as coinitiator with CQ in the system CQ/CCM/DMABN/SC938 for the polymerization of thin samples (15 μm) of Prime&Bond Active under air and under irradiation with the SmartLite Focus (300 mW.Math.cm-2).

[0119] FIG. 3 shows the photopolymenzation profiles of reactive functions in the presence of camphorquinone as photoinitiator (under air; SmartLite Focus 300 mW.Math.cm-2, in monomer Prime&Bond Active, the irradiation starts at t=5 s till t=120 s, thickness=15 μm) [0120] 1. CQ/CCM/DMABN/SC938 (0.7/0.05/0.65/0.75% w/w) [0121] 2. CQ/CCM/DMABN/SC938 as reference system (0.7/0.0010.65/0.75% w/w).

[0122] Remarkably, the system CQ/CCM/DMABN/SC938 presents enhanced polymerization performances compared to the reference system CQ/DMABN/SC938 clearly demonstrating the high synergy between CQ and CCM for high performance initiating system (better than CQ alone).

Example 4

[0123] The system CQ/CCM/DMABN/SC938 presents also exceptional bleaching properties upon irradiation with the blue dental LED. Nevertheless, as CCM is orange colored, better bleaching properties have been obtained for the system CQ/CCM/DMABN/SC938 (1/0.05/1/1% w/w) than those of the reference system CQ/DMABN/Me2-DPI (1.55/0.6510.75% w/w).

[0124] Photos of the samples before and after polymerization have been taken. Based on these photos the L, a, and b values have been measured for each sample after irradiation. The respective polymerization has been executed under air; SmartLite Focus 300 mW.Math.cm-2, in monomer Prime&Bond Active, the irradiation starts at t=5 s till t=120 s, thickness=15 μm.

[0125] Invention: CQ/CCM/DMABN/SC938: L=67+/−2; a=−2+/−2; b=3+/−2

[0126] Prior Art: CQ/DMABN/Me2-DPI: L=66+/−2; a=−2+/−2; b=5+/−2

[0127] Thus, CCM can be used as a polymerization indicator i.e. the irradiated areas for which the light intensity is high enough to initiate an efficient polymerization are fully bleached. This visual inspection can be used by the dentist to know the well polymerized areas (bleached ones).

Example 5

[0128] Remarkably, adding 0.05% of CCM and decreasing the amount of CQ from 1.55 to 0.7% leads to exceptional bleaching properties and does not affect the final color properties after polymerization whereas the sample before irradiation is more colored in presence of CCM. The main advantage of this initial coloration is that the change of color upon polymerization can be followed by naked eye with CCM (the Ab is much higher than without CCM but with the advantage of a full final bleaching); CCM acts as a colored visible indicator of polymerization. CCM is also a light intensity indicator the higher the light intensity in a given zone, the better the change of color and bleaching of CCM.

[0129] Prior Art CQ/DMABN/SC938 (1.55/0.6510.75% w/w)

[0130] Invention: CQ/CCM/DMABN/SC938 (0.7/0.05/0.65/0.75% w/w).

[0131] Photos of the samples before irradiation and after different period of irradiations (10 s and 20 s) have been taken. The irradiated areas for which the light intensity is high enough to initiate an efficient polymerization are fully bleached. This visual inspection can be used by the dentist to know if the light intensity is high enough for an efficient polymerization in a given areas. Based on these photos the L, a, and b values have been measured for each sample after irradiation. The respective polymerization has been executed under air; SmartLite Focus 300 mW.Math.cm-2, in monomer Prime&Bond Active, the irradiation time t=10 s and t=20 s, thickness=15 μm.

[0132] Prior Art (before irradiation): L=67+/−2; a=−5+/−2; b=6+/−2

[0133] Prior Art (after 10 s of irradiation): L=66+/−2; a=2+/−2: b=2+/−2; Δb=4

[0134] Prior Art (after 20 s of irradiation): L=66+/−2; a=−2+/−2; b=2+/−2; Δb=4

[0135] Invention (before irradiation): L=72+/−2; a=−13+/−2; b=36+/−2

[0136] Invention (after 10 s of irradiation): L=67+/−2; a=−5+/−2; b=3+/−2; Δb=33

[0137] Invention (after 20 s of irradiation): L=67+/−2; a=−2+/−2; b=3+/−2; Δb=33

[0138] While the principles of the invention have been explained in relation to certain particular embodiments, and are provided for purposes of illustration, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims. The scope of the invention is limited only by the scope of the appended claims.