Dental composition

Abstract

The present invention relates to a dental composition comprising at least one polymerizable monomer having at least one ethylenically unsaturated group, a photosensitizer having an absorption maximum in the range of 400 nm to 800 nm, and a radical initiator system comprising at least one thiophenium compound as a coinitiator.

Description

[Technical Field]

[0001] The present invention relates to a dental composition comprising at least one polymerizable monomer having at least one ethylenically unsaturated group, a photosensitizer having an absorption maximum in the range of 400 nm to 800 nm, and a radical initiator system comprising at least one coinitiator compound. [Background technology]

[0002] Dental restorations typically involve light-curable dental compositions containing free-radically polymerizable resins. Light-curing of dental compositions involves a photoinitiator system that generates free radicals upon exposure to visible light. Traditionally, photosensitizers such as camphorquinone (CQ), optionally combined with a tertiary aromatic amine, are often used as the photoinitiator system.

[0003] However, the presence of amines in (meth)acrylate-containing compositions can cause yellowing of the resulting photocured composition. Another drawback of tertiary aromatic amines is their tendency to discolor and their sensitivity to strongly acidic media. Furthermore, tertiary aromatic amines react with oxygen radicals. Therefore, while their use has the benefit of avoiding sticky surfaces, more aromatic amines are required for initiation than the stoichiometric requirements of the respective photosensitizers, such as CQ. Tertiary aromatic amines for use as coinitiators in dental compositions can leach from the cured composition, which can raise toxicological concerns. Toxicological concerns about tertiary aromatic amines, in particular, necessitate the development of new coinitiators for photosensitizers, such as CQ, in dental materials.

[0004] Prior art document D1, EP 3470048 A1, discloses a light-curable dental composition containing a specific polymerization initiator system containing a combination of a photoinitiator compound and a specific sulfinate or sulfonate coinitiator. The present invention also relates to the use of the polymerization initiator system in a light-curable dental composition. The specific polymerization initiator system of the present invention has high stability in an acidic medium.

[0005] Prior art document D2, US 2011 / 300484 A1, discloses new sulfonium salts, chemically amplified photoresist compositions containing the aforementioned compounds, and the use of the compounds as latent acids that can be activated by irradiation with actinic electromagnetic radiation and electron beams.

[0006] Prior art document D3, ZHANG BIANXIANG et al., 'Synthesis and characterization of triarylsulfonium salts as novel cationic photoinitiators for UV-photopolymerization', discloses the use of diaryliodonium salts as arylating reagents and copper as a catalyst to synthesize a series of triarylsulfonium salts bearing benzoyl or benzoheterocyclic moieties, 1 H NMR, 13 The compounds were characterized by C NMR and high-resolution mass spectrometry. The photoinitiating behavior of triarylsulfonium salts on the photopolymerization of an epoxy acrylate resin (UV6104) containing hexane-1,6-diyl diacrylate (HDDA) as an activated monomer was investigated. The results indicated that these triarylsulfonium salts could be utilized as cationic photoinitiators in UV curing processes. A photoinitiating mechanism was proposed.

[0007] Object of the invention In view of the prior art, it was therefore an object of the present invention to provide a novel dental composition comprising an initiator system that does not exhibit the aforementioned drawbacks of known prior art dental compositions.

[0008] In particular, it was an object of the present invention to provide dental compositions comprising a radical initiator system that is at least substantially free, and preferably completely free, of amines, particularly tertiary amines, and more particularly tertiary aromatic amines.

[0009] Therefore, what is needed is a method to provide new coinitiators for common photosensitizers such as camphorquinone in dental compositions, where the coinitiators are amine-free.

[0010] It is a further object of the present invention to provide dental compositions comprising radical initiator systems containing a combination of a photosensitizer and at least one specific amine-free coinitiator, which can reduce, or ideally avoid or eliminate, the leaching issues and toxicological concerns of commonly used tertiary aromatic amine-based coinitiators, while simultaneously improving required biocompatibility. Summary of the Invention

[0011] These objects, as well as further objects not expressly stated but which can be immediately derived or discerned from the relationships discussed herein as a preamble, are achieved by a dental composition having all the features of claim 1. Appropriate modifications of the dental composition are protected in dependent claims 2 to 15.

[0012] The present invention therefore provides: a) at least one polymerizable monomer having at least one ethylenically unsaturated group; b) a radical initiator system, i. a photosensitizer having an absorption maximum in the range of 400 nm to 800 nm; ii. at least one coinitiator compound; a radical initiator system comprising A dental composition comprising: At least one coinitiator compound is a thiophenium salt comprising a thiophenium cation and a monovalent anion, the thiophenium cation having the following formula (I): [ka] (In the formula, R1 = hydrogen, C1-C8 alkyl, or C1-C8 alkyl in which at least one hydrogen atom of the aforementioned C1-C8 alkyl is substituted with a halogen atom; R2, R3, R4, R5, R6, R7, R8, R9 = hydrogen, C1-C8 alkyl, C1-C8 alkyl in which at least one hydrogen atom of the aforementioned C1-C8 alkyl is substituted with a halogen atom, or halogen) The present invention provides a dental composition comprising:

[0013] It is therefore possible to provide novel dental compositions comprising initiator systems that, in an unpredictable manner, do not exhibit the aforementioned drawbacks of known prior art dental compositions.

[0014] Specifically, the present invention provides dental compositions comprising a radical initiator system that is at least substantially free, and preferably completely free, of amines, particularly tertiary amines, and more particularly tertiary aromatic amines.

[0015] The present invention thereby provides novel, amine-free coinitiators for common photosensitizers such as camphorquinone in dental compositions.

[0016] Additionally, dental compositions are provided that include a radical initiator system containing a combination of a photosensitizer and at least one specific coinitiator, which can reduce, or ideally avoid or eliminate, the leaching issues and toxicological concerns of commonly used tertiary aromatic amine-based coinitiators while simultaneously improving required biocompatibility.

[0017] Dental compositions containing such specific co-initiators of the present invention provide improved polymerization efficiency, including good conversion, without causing the problem of aromatic amine leaching. Such specific co-initiators of the present invention are stable in strongly acidic media, making them suitable for dental applications such as adhesives, composites, cements, and self-etching formulations. When incorporated into such dental compositions, such co-initiators of the present invention have low discoloration tendency while simultaneously exhibiting good storage stability.

[0018] The at least one co-initiator acts by initiating the polymerization of one or more polymerizable monomers having at least one ethylenically unsaturated group. When incorporated into such dental compositions, the co-initiators of the present invention provide biocompatibility with reduced component release.

[0019] For a more complete understanding of the present invention, reference is now made to the following detailed description taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1] Photopolymerization profiles of six different thiophenium salts as coinitiators in combination with CQ compared to CQ in combination with tertiary amines are shown for the polymerization of Prime&bond Active resin (methacrylate resin). [Figure 2] We present the photopolymerization profile of one particular thiophenium salt (5) as a coinitiator in combination with CQ (both combined in several different amounts) compared to CQ in combination with iodonium ions for the polymerization of Prime&bond Active resin (a methacrylate resin). [Figure 3] The photopolymerization profile of one particular thiophenium salt (1) as a coinitiator in combination with CQ is shown, compared to CQ in combination with two alternatives to thiophenium, for the polymerization of Prime&bond Active resin (a methacrylate resin). DETAILED DESCRIPTION OF THE INVENTION

[0021] The term "alkyl," unless otherwise specified, refers to a monoradical branched or unbranched saturated hydrocarbon chain having 1 to 18 carbon atoms. This term can be exemplified by groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-decyl, dodecyl, and tetradecyl.

[0022] The term "alkoxy group," unless otherwise specified, refers to a monoradical branched or unbranched saturated hydrocarbon chain having 1 to 18 carbon atoms, wherein at least one carbon atom of such an alkoxy group is substituted with an oxygen atom. Such an alkoxy group is attached to a carbon atom of the compound by said at least one oxygen atom. This term can be exemplified by groups such as methoxy and ethoxy. Thus, the term "alkoxy group," in the context of this invention, is defined as understood by a chemist based on common chemical knowledge.

[0023] The term "alkylene," unless otherwise specified, refers to a linear saturated divalent hydrocarbon radical of 1 to 4 carbon atoms or a branched saturated divalent hydrocarbon radical of 3 to 4 carbon atoms, such as methylene, ethylene, 2,2-dimethylethylene, propylene, 2-methylpropylene, and butylene, preferably methylene, ethylene, or propylene.

[0024] The term "aryl" refers to a C6-C10 membered aromatic, heterocyclic, fused aromatic, fused heterocyclic, biaromatic, or biheterocyclic ring system. Broadly defined, "aryl," as used herein, includes 5-, 6-, 7-, 8-, 9-, and 10-membered monocyclic aromatic groups that may contain 0-4 heteroatoms, such as benzene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine, and pyrimidine. "Aryl" groups having heteroatoms in the ring structure may also be referred to as "heteroaryl" or "heterocyclic" or "heteroaromatic." The aromatic ring may 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, amide, phosphonate, phosphate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamide, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moiety, --CF3, --CN, and combinations thereof.

[0025] The term "cycloalkyl" refers to a monocyclic or polycyclic cycloalkyl radical. Examples of monocyclic acycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic cycloalkyl radicals include, for example, adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl, and tricyclo[5.2.1.0]heptanyl. 2,6 ]Decil, etc.

[0026] The term "(meth)acrylate" is intended in the context of the present disclosure to refer to the acrylate and the corresponding methacrylate.

[0027] The term "(meth)acrylamide", in the context of the present disclosure, is intended to include acrylamide and methacrylamide.

[0028] The term "polymerizable monomer" in the context of this disclosure means any monomer capable of radical polymerization. The polymerizable monomer contains at least one ethylenically unsaturated group. The at least one ethylenically unsaturated group includes vinyl, allyl, acrylic, methacrylic, and styryl.

[0029] The terms "polymerizable monomer having at least one ethylenically unsaturated group" and "ethylenically unsaturated monomer" may be used interchangeably.

[0030] The term "radical initiator system," in the context of this disclosure, means any system comprising a sensitizer and at least one coinitiator that, when activated by heat or light and / or environmental redox conditions, forms free radicals, thereby initiating the polymerization of polymerizable monomers.

[0031] The term "co-initiator," in the context of the present disclosure, means a compound that does not essentially absorb upon exposure to UV radiation or visible light, but forms free radicals together with the sensitizer used in accordance with the present disclosure.

[0032] The term "sensitizer," in the context of this disclosure, refers to a compound that can absorb radiation in the wavelength range of 400-800 nm upon exposure, but cannot form free radicals alone, i.e., without the addition of a coinitiator. Sensitizers used in this disclosure must be able to interact with the coinitiators used in this disclosure.

[0033] The present disclosure relates to a dental composition selected from a dental adhesive, a dental composite, a dental sealant, and a dental cement.

[0034] The dental compositions of the present disclosure include one or more polymerizable monomers having at least one ethylenically unsaturated group.

[0035] The polymerizable monomer may be an acrylate, a methacrylate, an ethylenically unsaturated compound, a carboxyl group-containing unsaturated monomer, a C2-8 hydroxyl alkyl ester of (meth)acrylic acid, a C1-24 alkyl ester or cycloalkyl ester of (meth)acrylic acid, a C2-18 alkoxyalkyl ester of (meth)acrylic acid, an olefin or diene compound, a monoester / diester, a monoether, an adduct, a vinyl monomer, a styryl monomer, a TPH resin, an SDR resin, a PBA resin, and / or a BPA-free resin.

[0036] Radical initiator system The dental composition of the present disclosure includes a radical initiator system. The radical initiator system may include a photoinitiator. Suitable photoinitiators may be in the form of a two-component or three-component system. The two-component system may include a photosensitizer and a thiophenium salt as a coinitiator. The three-component system may further include an iodonium, sulfonium, or phosphonium salt.

[0037] In one embodiment, the monovalent anion of the thiophenium salt is selected from the group consisting of sulfonic acids, substituted sulfonic acids, borohydrides, and substituted borohydrides.

[0038] In a preferred embodiment thereof, the monovalent anion of the thiophenium salt is selected from the group consisting of alkylsulfonic acids, substituted alkylsulfonic acids, borohydrides, and substituted borohydrides in which at least one hydrogen atom of the aforementioned borohydrides has been replaced with a halogen atom.

[0039] In a more preferred embodiment, the monovalent anion of the thiophenium salt is selected from the group consisting of substituted alkylsulfonic acids in which at least one hydrogen atom, preferably all hydrogen atoms, of the alkyl group of the aforementioned alkylsulfonic acids are replaced with halogen atoms, and substituted borohydrides in which all hydrogen atoms of the aforementioned borohydrides are replaced with halogen atoms.

[0040] In another preferred embodiment, the thiophenium cation has the following formula (II): [ka] (In the formula, R4, R7, R 10 , R 11 , R 12 = hydrogen or halogen, with the proviso that R 10 , R 11 , R 12 At least one of = halogen, preferably R4 and R7 = hydrogen or halogen, R 10 , R 11 , R 12 = halogen) It has.

[0041] In a more preferred embodiment, the thiophenium cation has the following formula (III) or (IV): [ka] It has one of the following.

[0042] In one embodiment, the thiophenium salt is present in an amount of 0.1 to 5 weight percent, preferably 0.15 to 2.5 weight percent, and more preferably 0.2 to 2 weight percent, based on the total weight of the dental composition.

[0043] In conclusion, according to one embodiment of the present invention, at least one coinitiator is a compound according to one of formulae (I), (II), (III) or (IV) as defined above.

[0044] In one embodiment, two or more coinitiator compounds are included by the radical initiator system of the present invention, and all included coinitiator compounds are compounds according to one of formulas (I), (II), (III), or (IV).

[0045] In an alternative embodiment, two or more coinitiator compounds are included by the radical initiator system of the present invention, each of the included coinitiator compounds being a compound according to one of formulas (I), (II), (III), or (IV), and at least two of these coinitiator compounds being a compound according to the same formula (I), (II), (III), or (IV).

[0046] In a further alternative embodiment, two or more coinitiator compounds are included by the radical initiator system of the present invention, and all included coinitiators are compounds according to the same formula (I), (II), (III), or (IV).

[0047] In one embodiment, the photosensitizer is a 1,2-diketone compound.

[0048] The alpha-diketone sensitizer compound may be selected from camphorquinone, 1,2-diphenylethane-1,2-dione (benzyl), 1,2-cyclohexanedione, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione, 2,3-heptanedione, 3,4-heptanedione, glyoxal, biacetyl, 3,3,6,6-tetramethylcyclohexanedione, 3,3,7,7-tetramethyl-1,2-cycloheptanedione, 3,3,8,8-tetramethyl-1,2-cyclooctanedione, 3,3,18,18-tetramethyl-1,2-cyclooctadecanedione, dipivaloyl, furyl, hydroxybenzyl, 2,3-butanedione, 2,3-octanedione, 4,5-octanedione, and 1-phenyl-1,2-propanedione.

[0049] In a preferred embodiment, the photosensitizer is camphorquinone (CQ).

[0050] In one embodiment, the photosensitizer is present in an amount of 0.1 to 5 weight percent, preferably 0.15 to 2.5 weight percent, and more preferably 0.2 to 2 weight percent, based on the total weight of the dental composition.

[0051] In one embodiment, the ratio of the amount of photosensitizer to the amount of coinitiator ranges from 1:2.5 to 2.5:1, preferably from 1:3.5 to 3.5:1, and more preferably from 1:5 to 5:1.

[0052] In one embodiment, the radical initiator system is present in an amount of 0.1 to 10 weight percent based on the total weight of the dental composition.

[0053] In one embodiment, the dental composition comprises a radical initiator system that is at least substantially free, and preferably completely free, of amines, particularly tertiary amines, and more particularly tertiary aromatic amines.

[0054] In one embodiment, the dental composition further comprises an additive selected from an iodonium salt, a phosphonium salt, and a sulfonium salt, preferably, the additive is an iodonium salt.

[0055] In one preferred embodiment thereof, the additive is present in an amount of 0.01 to 5 weight percent based on the total weight of the dental composition.

[0056] Such iodonium compounds have the following formula (C): R 21 -I + -R 22 A - Formula (C) (In the formula, R 21 and R 22 are independent of each other and represent organic moieties, A - is an anion) may include:

[0057] In embodiments, the iodonium compounds include diphenyliodonium (DPI) hexafluorophosphate, di(4-methylphenyl)iodonium (Me2-DPI) hexafluorophosphate, di-(4-t-butylphenyl)-iodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate (Irgacure® 250, BASF commercially available from SE), (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium tetrafluoroborate, 4-octyloxyphenylphenyliodonium hexafluoroantimonate, 4-(2-hydroxytetradecyloxyphenyl)phenyliodonium hexafluoroantimonate, and 4-isopropyl-4'-methyldiphenyliodonium borate.

[0058] According to further embodiments, the iodonium compound is bis-(4-t-butylphenyl)-iodonium hexafluorophosphate (SC938), di(4-methylphenyl)iodonium (Me2-DPI) hexafluorophosphate, or bis(4-tert-butylphenyl)iodonium p-toluenesulfonate.

[0059] According to a further embodiment, the photoinitiator has the following formula (D): R 23 R 24 R 25 S + A - Formula (D) (In the formula, R 23 , R 24 , and R 25 are independent of each other and represent an organic moiety or R 23 , R 24 , and R 25 any two of these form a ring structure together with the sulfur atom to which they are attached, A - is an anion) The sulfonium compounds may include:

[0060] The triarylsulfonium salts are as follows: [ka] S-(phenyl)thianthrenium hexafluorophosphate of the formula:

[0061] According to a further embodiment, the photoinitiator has the following formula (E): R 26 R 27 R 28 R 29 P + A - Formula (E) (In the formula, R 26 , R 27 , R 28 , and R 29 are independent of each other and represent organic moieties, A - is an anion) The phosphonium compounds may include:

[0062] The phosphonium salt of Formula (E) can be a tetraalkylphosphonium salt, a tetrakis-(hydroxymethyl)-phosphonium (THP) salt, or a tetrakis-(hydroxymethyl)-phosphonium hydroxide (THPOH) salt, wherein the anion of the tetraalkylphosphonium salt is selected from the group consisting of formate, acetate, phosphate, sulfate, fluoride, chloride, bromide, and iodide.

[0063] Other suitable photoinitiators for polymerizing free radical photopolymerizable compositions can include the class of phosphine oxides, which typically have a functional wavelength range of about 380 nm to about 1200 nm. Additional suitable phosphine oxide free radical initiators, having a functional wavelength range of about 380 nm to about 450 nm, are the acyl and bisacyl phosphine oxides.

[0064] The present invention therefore addresses the problem of providing dental compositions of the present invention that include an improved initiator system.

[0065] 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 as defined by the claims appended hereto.

[0066] The following different thiophenium salts were used in the inventive and comparative experiments: [ka]

[0067] Example 1: Systematic study of all six different thiophenium salts shown above as coinitiators in combination with CQ compared to CQ in combination with tertiary amines for the polymerization of Prime&bond Active resin (methacrylate resin) In the presence of camphorquinone (CQ) as a photoinitiator (air, thickness = 13 μm, SmartLite Focus 300 mW / cm 2 ) photopolymerization profile of C=C double bond (PrimeBond Active) (shown in Figure 1): (1) CQ / thiophenium 1 (1.5 / 1% w / w) (2) CQ / thiophenium 2 (1.5 / 1% w / w) (3) CQ / thiophenium 3 (1.5 / 1% w / w) (4) CQ / thiophenium 4 (1.5 / 1% w / w) (5) CQ / thiophenium 5 (1.5 / 1% w / w) (6) CQ / thiophenium 6 (1.5 / 1% w / w), and (7) CQ / ethyl 4-(dimethylamino)benzoate (EDB) (1.5 / 1% w / w). Illumination (LED @ 477 nm) begins at t = 8 seconds (shown in Figure 1).

[0068] It is clearly demonstrated here that the effect of the invention is achieved only when the compound of formula (I) as defined in claim 1 is selected instead of EDB, meaning that it has at least the same photopolymerization conversion as the well-known and established prior art system of CQ with a tertiary amine such as EDB.

[0069] Good results were achieved with the inventive examples of thiopheniums 1, 3, and 5, while comparative examples were produced by using thiopheniums 2, 4, and 6. Thiopheniums 1, 3, and 5 proved to offer a promising approach for replacing tertiary amines with certain thiophenium compounds. However, as will be shown, even in this case, applicants carefully studied potential candidates to determine which thiophenium compounds (salts) would be suitable for this application and which would not.

[0070] Example 2: Systematic investigation of different amounts of thiophenium salt 5 (shown above) as a coinitiator in combination with different amounts of CQ compared to CQ in combination with an iodonium compound (SC938) for the polymerization of Prime&bond Active resin (a methacrylate resin) In the presence of camphorquinone (CQ) as a photoinitiator (air, thickness = 13 μm, SmartLite Focus 300 mW / cm 2 ) photopolymerization profile of C=C double bond (PrimeBond Active) (shown in Figure 2): (1) CQ / thiophenium 5 (1.5 / 1.5% w / w) (2) CQ / thiophenium 5 (1.5 / 1% w / w) (3) CQ / thiophenium 5 (1.5 / 0.5% w / w) (4) CQ / thiophenium 5 (1 / 1.5% w / w) (5) CQ / thiophenium 5 (1 / 0.5% w / w), and (6) CQ / SC938(1 / 0.5%w / w). Illumination (LED @ 477 nm) begins again at t = 8 seconds (shown in Figure 1).

[0071] It is now clearly demonstrated that the initiator system of the present invention, based on the combination of CQ with a selected thiophenium compound according to the claimed set, in this example thiophenium 5, provides superior photopolymerization conversion results compared to initiator systems based on the well-known and established prior art system of CQ with an iodonium compound.

[0072] Furthermore, specific different ratios of CQ and the amount of each thiophenium 5 used were investigated. As can be easily derived from Figure 2, all photopolymerization results are promising, even if the results vary somewhat between each other, depending on the exact ratio.

[0073] All initiator systems applied in Example 2 showed good solubility. Too much initiator often limits its possible applications due to serious solubility problems.

[0074] These initiator systems were then successfully used to provide transparent dental adhesives that did not result in a yellow adhesive layer after curing (caused by unreacted photoinitiators such as CQ) and at the same time did not result in a significant decrease in photopolymerization efficiency.

[0075] The initiator system of the present invention therefore also exhibits excellent bleaching properties upon irradiation with a blue dental LED, as shown in Table 1.

[0076] [Table 1]

[0077] Photographs of the samples were taken before and after polymerization. Based on these photographs, the L, a, and b values ​​of each sample after irradiation were measured. Each polymerization was performed under air with a SmartLite Focus at 300 mW / cm. 2 was performed in the monomer Prime&Bond Active, irradiation started at t=5 s and continued until t=120 s, thickness=13 μm.

[0078] Example 3. Preparation and analysis of different dental adhesive compositions using different thiophenium salts as coinitiators in combination with different amounts of CQ compared to CQ in combination with a tertiary amine (DMABN) All compounds were weighed into a brown glass flask and stirred at room temperature for 24 hours. The solution was filtered through a 0.45 μl PTFE filter.

[0079] The shear bond strength (SBS) of each example was measured according to ISO 29022 using a sample size of 7 instead of 15. Table 2 below shows the results of Experiments 3a-3i, all of which are examples of the present invention except for Examples 3b and 3f, which are comparative examples.

[0080] [Table 2]

[0081] Example 4. Systematic Investigation of Alternatives to Thiophenium 1 as Co-initiators in Combination with CQ Compared to CQ in Combination with Tertiary Amines for the Polymerization of Prime&bond Active Resin (Methacrylate Resin) The following two alternatives were investigated for comparison with thiophenium salts as coinitiators: [ka]

[0082] In the presence of camphorquinone (CQ) as a photoinitiator (air, thickness = 13 μm, SmartLite Focus 300 mW / cm 2 ) photopolymerization profile of C=C double bond (PrimeBond Active) (shown in Figure 3): (1) CQ / thiophenium 1 (1.5 / 1% w / w) (2) CQ / thianthrenium (1.5 / 1% w / w) (3) CQ / sulfonium (1.5 / 1% w / w), and (4) CQ / ethyl 4-(dimethylamino)benzoate (EDB) (1.5 / 1% w / w). Illumination (LED @ 477 nm) begins at t = 8 seconds (shown in Figure 1).

[0083] [Table 3]

[0084] Photographs of the samples were taken before and after polymerization. Based on these photographs, the L, a, and b values ​​of each sample after irradiation were measured. Each polymerization was performed under air with a SmartLite Focus at 300 mW / cm. 2 was performed in the monomer Prime&Bond Active, irradiation started at t=5 s and continued until t=120 s, thickness=13 μm.

[0085] As can be seen from the comparison of the photopolymerization conversion results, the proposed substitutes for the claimed thiophenium compounds, i.e., thianthrenium salts or sulfonium salts, do not provide sufficient photopolymerization experimental conversion rates, even when their subsequently determined optical values ​​are good enough to provide transparent dental adhesives.

[0086] Thus, even these chemically very similar compounds may not provide the same good performance as the selected thiophenium compounds claimed.

[0087] This demonstrates that neither the choice of the exact thiophenium compound itself nor the choice of chemical properties of such compounds is irrelevant to arrive at the technical teachings of the present invention.

[0088] While the principles of the invention have been explained in relation to specific embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. It is therefore to be understood that the invention disclosed herein is intended to cover all 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.

Claims

1. a) at least one polymerizable monomer having at least one ethylenically unsaturated group; b) a radical initiator system, i. a photosensitizer having an absorption maximum in the range of 400 nm to 800 nm; ii. at least one coinitiator compound; a radical initiator system comprising A dental composition comprising: The at least one coinitiator compound is a thiophenium salt comprising a thiophenium cation and a monovalent anion, the thiophenium cation having the following formula (I): 【Chemistry 1】 (In the formula, R １ = hydrogen, C １ ~C ８ Alkyl, or the C １ ~C ８ C in which at least one hydrogen atom of the alkyl is substituted with a halogen atom １ ~C ８ is alkyl, R ２ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ = hydrogen, C １ ~C ８ alkyl, the C １ ~C ８ C in which at least one hydrogen atom of the alkyl is substituted with a halogen atom １ ~C ８ alkyl, or halogen) A dental composition comprising:

2. 2. The dental composition of claim 1, wherein the monovalent anion of the thiophenium salt is selected from the group consisting of sulfonic acids, substituted sulfonic acids, borohydrides, and substituted borohydrides.

3. 3. The dental composition of claim 2, wherein the monovalent anion of the thiophenium salt is selected from the group consisting of alkylsulfonic acids, substituted alkylsulfonic acids, borohydrides, and substituted borohydrides in which at least one hydrogen atom of the borohydride is replaced with a halogen atom.

4. 4. The dental composition of claim 3, wherein the monovalent anion of the thiophenium salt is selected from the group consisting of substituted alkylsulfonic acids in which at least one hydrogen atom, preferably all hydrogen atoms in the alkyl group of the alkylsulfonic acid, is replaced with a halogen atom, and substituted borohydrides in which all hydrogen atoms of the borohydride are replaced with a halogen atom.

5. The thiophenium cation has the following formula (II): 【Chemistry 2】 (In the formula, R ４ , R ７ , R １０ , R １１ , R １２ = hydrogen or halogen, with the proviso that R １０ , R １１ , R １２ At least one of the above is halogen, preferably R ４ and R ７ = hydrogen or halogen, R １０ , R １１ , R １２ = halogen) The dental composition according to any one of claims 1 to 4, characterized in that it comprises:

6. The thiophenium cation is represented by the following formula (III) or (IV): 【Transformation 3】 The dental composition according to any one of claims 1 to 5, characterized in that it comprises one of the following:

7. 7. The dental composition according to claim 1, wherein the thiophenium salt is present in an amount of 0.1 to 5 weight percent, preferably 0.15 to 2.5 weight percent, and more preferably 0.2 to 2 weight percent, based on the total weight of the dental composition.

8. 8. The dental composition according to claim 1, wherein the photosensitizer is present in an amount of 0.1 to 5 weight percent, preferably 0.15 to 2.5 weight percent, and more preferably 0.2 to 2 weight percent, based on the total weight of the dental composition.

9. 9. The dental composition according to claim 1, wherein the ratio of the amount of photosensitizer to the amount of coinitiator is in the range of 1:2.5 to 2.5:1, preferably 1:3.5 to 3.5:1, more preferably 1:5 to 5:

1.

10. The dental composition according to any one of claims 1 to 9, further comprising an additive selected from an iodonium salt, a phosphonium salt, and a sulfonium salt, preferably wherein the additive is an iodonium salt.

11. 11. The dental composition of claim 10, wherein the additive is present in an amount of 0.01 to 5 weight percent based on the total weight of the dental composition.

12. Dental composition according to any one of claims 1 to 11, characterized in that the photosensitizer is a 1,2-diketone compound, preferably camphorquinone.

13. 13. The dental composition of any one of claims 1 to 12, wherein the radical initiator system is present in an amount of 0.1 to 10 weight percent, based on the total weight of the dental composition.

14. 14. Dental composition according to any one of claims 1 to 13, characterized in that the dental composition comprises a radical initiator system that is at least substantially free, preferably completely free, of amines, in particular tertiary amines, more in particular tertiary aromatic amines.

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