FI80381B - A visible light cured fluid dental composition, a process for the preparation thereof and its use as a dental filler material - Google Patents

Description

1 80381 Visible light-curable flowable dental composition, method for its preparation and its use as a dental filling material 5 Separated from patent application 820759

The invention relates to a visible light-curable fluid dental composition comprising at least one polymerizable ethylenically unsaturated substance, 40-10% by weight of the composition of at least one finely divided filler and a visible light-sensitive catalyst. The invention further relates to a method for preparing a dental composition and to its use as a dental filling material.

15 Many polymerizable substances have been used for dental purposes. Examples of materials include polyurethanes, monomeric and polymeric acrylates and methacrylates, polyamides, epoxy compounds, poly-styrenes. They have been assigned many applications such as fillings, crowns, denture body, coating, gaskets and cements. For some of these uses, it has been proposed to add inorganic fillers to give the desired color and / or strength.

Preferred polymerizable materials used in dental fillings include the reaction product of bisphenol A and Glycidyl methacrylate, sometimes referred to as bis-GMA, described in U.S. Patent 3,066,112, and a vinyl urethane prepolymer, such as those described in GB 1,352,063. These ethylenically unsaturated substances are polymerized in situ using a conventional redox (e.g. amine peroxide) catalyst system or an ultraviolet or preferably visible photocatalyst system such as that described in GB 40. The mixture may contain up to 90% by weight of an inert inorganic filler, as described, for example, in GB Patents 1,465,897, 1,488,403, 1,498,421, U.S. Pat. Nos. 3,629,187 and 3,709,866. In DE-A-2 419 887 and 2 816 823 and in EP-A-13 491. When filling with 5 teeth, it is important that the visible light the curable filler would cure (i.e. would harden rapidly when exposed to visible light) and that the cure would be substantially homogeneous throughout the volume of the filler. Then the dentist can be sure that the filling is satisfactory and the patient can use the teeth immediately after the treatment without waiting for the filling to harden.

GB patent application 2,016,994 describes a visible light curable dental composition comprising a ketone and an organic peroxide.

It has now unexpectedly been found that the depth of curing in a visible light cured dental composition increases and the curing is more homogeneous than in the previously described compositions if the catalyst system contains a mixture of ketone, organic peroxide and amine.

According to the invention, there is provided a visible light curable dental composition comprising at least one polymerizable ethylenically unsaturated substance, 40-90% by weight of the composition of at least one finely divided filler and a visible light sensitive catalyst. The dental composition of the invention is characterized in that the catalyst comprises (i) at least one ketone having a photosensitive catalytic activity selected from fluorenone-30 and α-diketones of formula A-C-C-A,

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oo 35 wherein the groups A may be the same or different and are 3 80381 hydrocarbon or substituted hydrocarbon groups, and wherein the groups A may be further linked by a divalent linkage or via a divalent hydrocarbon or substituted hydrocarbon group, or wherein the groups A together may form a fused (ii) at least one organic peroxide having a half-life of less than 150 ° C for ten hours and having the formula ROOR, wherein the groups R may be Salo mat or different and are hydrogen, alkyl, aryl or acyl groups, with up to one of the groups R is hydrogen, and (iii) a reducing agent which is an organic amine capable of reducing the ketone when it is in the excited state.

The dental compositions of the invention can be used for a variety of dental purposes, such as fillers, orthodontic cements, and reinforcing agents. The compositions may be colored as desired to match the color of the tooth and / or adjacent teeth.

The compositions of the invention are liquid, pasty and not powdery or crumbly at ambient temperatures so that in the uncured state they can be formed into a permanent mass and kept in this form without substantial flow. Such properties allow the composition to be placed in a cavity or molded over a tooth in the upper jaw without changing shape prior to curing. Accordingly, in the compositions of the invention, the viscosity of the polymerizable material 30 is such that a composition containing 40% (preferably 60%) to 90% by weight of a finely divided excipient has the required liquid paste-like consistency. The compositions may contain a mixture of polymerizable ethylenically unsaturated substances. If one or more of those substances are solid 4 80381 or semi-solid, then the polymerizable substances of one or more of the other ingredients should be liquid at ambient temperatures to give the mixture a pasty consistency. If desired, all of the polymerizable materials 5 may be liquid at ambient temperatures. The viscosity of the polymerizable substance and the consistency of the composition can be controlled by controlling the mixture of polymerizable substances.

The polymerizable substance includes those mentioned above, but is preferably a liquid, ethylenically unsaturated substance, such as vinyl urethane, for example those described in GB 1 352 063, 1 465 097, 1 498 421 and DE application. 2,419,887, or the reaction product of a diol such as glycol or especially bisphenol, glycidyl alkacrylate, as described in U.S. Patent Nos. 3,066,112 and 4,131,729.

The preferred reaction product of glycidyl alkacrylate and diol has the formula 20 F ί1 * 3? H JT ~ \ \ l CH2 = C-C0.0-CH2CH.CH2-0-r / ~ 2) c CH3 In the above-mentioned GB patents and DE application the preferred vinyl urethanes described in the publication are a reaction product of a urethane prepolymer and an ester of acrylic or methacrylic acid and a hydroxyalkanol having at least 2 carbon atoms, wherein the urethane prepolymer is an diiso-cyanate of the formula OCN-R1-NCO and a diol of the formula HO-R2-OH R2 is a condensate group of an alkylene oxide and an organic compound containing two phenolic or alcoholic groups, a reaction product.

Other suitable vinyl urethanes include those made in the reaction between alkyl and aryl, preferably alkyl, diisocyanates and hydroxyalkyl acrylates and alkacrylates, such as those described in GB Patents 1,401,805, 1,428,672 and 1 430 303.

Liquid ethylenically unsaturated monomers (whose polymers should be water-insoluble) suitable as polymerizable materials include vinyl monomers, e.g., vinyl esters such as n-hexyl, cyclohexyl, and tetrahydrofurfuryl acrylates, and methacrylates. Monomers should have low toxicity and volatility.

Polyfunctional monomers are also suitable as polymerizable vinyl monomer waves, i. monomers containing two or more vinyl groups. Suitable monomers include, for example, glycol, dimethacrylates, diallyl phthalate and triallyl cyanurate.

The preferred polymerizable material consists of a mixture of vinyl urethane or glycidyl alkacrylate and 25 to 150% by weight of vinyl urethane or glycidyl alkacrylate of at least one of the polyfunctional monomers described above.

The dental compositions of the invention are cured by irradiating the composition with visible light, preferably one having a wavelength in the range of 400 to 500 nm. In order for the mixtures to cure in this range, the mixtures contain at least one ketone selected from fluorenone and diketone and at least one organic peroxide, and an organic amine capable of reducing the ketone when excited.

The ketones suitable for use in the compositions of the invention exhibit some photosensitive catalytic activity by themselves in the absence of organic peroxides. Such ketone activity is enhanced by the addition of an organic amine described in the aforementioned GB Patent No. 1,408,265. According to this, 6,80381 of the present ketones are selected from fluorenone and α-diketones as defined above and derivatives thereof which are mixed with a similar amount of organic amine. an amine capable of reducing that ketone in its excited state, but in the absence of organic peroxide, catalyzes the curing of the ethylenically unsaturated substance. Evidence of curing can be conveniently detected by examining the change in viscosity of its ethylenically unsaturated material containing ketone and 10 organic amines, both 1% by weight of ethylenically unsaturated material, using vibration rheometry, sample thickness 2 mm, while irradiating the mixture with light at 400 500 nm. Such an examination may be carried out using British Standard Method 5199: 1975, paragraph 6.4, provided that the possibility of directing visible light to the mixture is provided. Preferably, the cure time of the ketone is less than 15 minutes at a radiation level of 1000 W / m2 measured at 470 nm, bandwidth ± 8 nm, for example using a Macam Radiometer (Macam Photometries Ltd., Edinburgh, Scotland).

Diketones have the formula:

A-C-C-A

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25 0 0 in which the groups A, which may be the same or different, are hydrocarbon or substituted hydrocarbon groups and in which the groups A may be further linked by a divalent bond or a divalent hydrocarbon or substituted hydrocarbon group, or in which the groups A may together form a fused aromatic ring system-min. The groups A are preferably the same.

Groups A can be aliphatic or aromatic. The term aliphatic includes cycloaliphatic groups and aliphatic groups having aromatic substituents, that is, aralkyl groups. Similarly, the term aromatic group includes groups having alkyl substituents, that is, alkaryl groups.

The term aromatic groups includes heterocyclic groups.

The aromatic group may be a benzenoid aromatic group, e.g., a phenyl group, or it may be a non-benzenoid cyclic group identified in the art for its benzenoid aromatic group properties.

Groups A, especially aromatic ones, may be substituted by non-hydrocarbon groups, e.g. a halogen or alkoxy group. Non-hydrocarbon substituents can lead to inhibition of the polymerization of ethylenically unsaturated substances, and if α-diketone has such substituents, it is preferably not present in the photopolymerizable mixture at a concentration that would result in significant inhibition of polymerization of the ethylenically unsaturated substance.

The groups A may further be linked together by a direct bond or a divalent group, e.g. a divalent hydrocarbon group, i.e. a -C-C- group.

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In addition to coupling via 25 0 0, the groups A may be coupled to each other to form a cyclic ring system. For example, if the groups A are aromatic, the α-diketone may have the structure: / T \ / \

Ph - C - C - Ph I

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35 0 0 e 80381 wherein Ph is a phenylene group, Y is> CH 2, or a derivative thereof, wherein one or both of the hydrogen atoms are substituted by a hydrocarbon group and m is 0, 1 or 2. Preferably the group Y is attached to aromatic groups at the ortho positions to the group 5 -CC-

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o o relative to 10.

Groups A together may form a fused aromatic ring system.

In general, α-diketones are able to excite at the wavelength of visible light in the spectrum, that is, in light with a wavelength greater than 400 nm, e.g., in the wavelength range of 400 nm to 500 nm. For the present invention, the volatility of α-diketone should be low to minimize variations in odor and concentration. Suitable α-diketones include benzyl in which each group A is phenyl, α-diketones in which each group A is a fused aromatic group, e.g. α-naphthyl and β-naphthyl, and α-di-ketones in which groups A are alkylaryl groups, e.g. p-tolyl. As an example of a suitable α-diketone in which the groups A are non-benzoidal aromatic groups, mention may be made of furil, e.g. 2: 2'-furil. Suitable α-diketone derivatives in which non-hydrocarbon groups are attached to the groups A are, for example, p, p'-dialoxybenzyl, e.g. p, p'-dimethoxybenzyl or p, p'-dihalobenzyl, e.g. p, p'-dichlorobenzyl or p-nitrobenz-30.

The groups A may be linked together by a direct bond or a divalent hydrocarbon group to form a cyclic ring system. For example, if the groups A are aliphatic, the α-diketone may be camphor-35 noni.

9 80381

An example of an α-diketone of structure I is phenanthraquinone in which the aromatic groups A are attached by a direct bond in the ortho position to the group -C -C-

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o o.

Suitable derivatives include 2-bromo, 2-nitro-10-, 4-nitro, 3-chloro, 2,7-dinitro, 1-methyl-7-isopropylphenanthraquinone.

The α-diketone may be an acenaphthene quinone in which the groups A together form a fused aromatic ring system.

The present ketone may also be a fluorenone or a derivative thereof, such as a lower alkyl (C1-6), halogen, nitro, carboxylic acid or ester derivative thereof, especially in the 2- and 4-positions.

For example, ketone may be present in the mixture at a pi-20 content of 0.01 to 2% by weight of the polymerizable substance in the mixture, although concentrations outside this range may be used if desired. Suitably the ketone is present in a concentration of 0.1 to 1% and more preferably 0.5 to 1% by weight of the ethylenically unsaturated substance in the mixture. The ketone should be soluble in the polymerizable material and the concentrations given above refer to solution concentrations.

Organic peroxides useful in the present mixture have the formula:

R-O-O-R

wherein the groups R, which may be the same or different, are hydrogen, alkyl, aryl or acyl groups, wherein at most one of the groups R is hydrogen. The term acyl means 80381 groups of the formula R3 -CO- wherein R3 is an alkyl, aryl, alkyloxy or aryl-oxy group. The terms alkyl and aryl have the meanings given above in connection with groups A and include substituted alkyls and aryls.

Examples of organic peroxides 10 useful in the composition of the present invention include e.g. diacetyl peroxide, dibenzoyl peroxide, di-tertiary butyl peroxide, dilauroyl peroxide, tertiary butyl perbenzoate, diter tert-butyl cyclohexyl perdicarbonate.

Organic peroxide may be present in the mixture, for example 0.1 to 20% by weight of the polymerizable substance in the mixture, although concentrations outside this range may be used if desired.

Peroxide reactivity is often measured in terms of ten-hour half-temperature temperatures, i. within ten to 20 hours at this temperature, half of the oxygen is made available. The peroxides of the present compositions preferably have a ten hour half-life temperature of less than 150 ° C, more preferably less than 100 ° C.

The reducing agent contained in the composition of the invention, which is capable of reducing the ketone when the latter is in the excited state, increases the rate at which the composition cures under the influence of visible light. Such reducing agents are described, for example, in DE-A-2 251048 and are organic amines, preferably of the formula R43N, in which the groups R4, which may be the same or different, are hydrogen atoms, hydrocarbon groups, substituted hydrocarbon groups or groups in which two R4 together with the nitrogen atom form a cyclic ring system, with up to two of the R4 units being hydrogen atoms and, if the nitrogen atom is attached to a nitrogen atom,

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80381 to the aromatic group R4, at least one of the other units R4 is a group 5 -C-

B

attached to a nitrogen atom. The reducing agent is preferably present in the mixture in a concentration of 0.01 to 2% by weight of the polymerizable substance 10, although concentrations outside this range may be used if desired. However, as described above, the advantage of the present compositions is that they can be used by a dentist from a single container; the presence of a reducing agent together with the organic peroxide can lead to premature invisible light-initiated curing, thus shortening the storage time of the mixture. However, the amine reducing agent used in the compositions of the invention, together with a suitable diketone and organic peroxide, is capable of producing an improved curing depth at the same time as an acceptable storage time.

As indicated above, the composition of the invention contains 40 to 90% by weight of finely divided excipient. It is preferred that at least 50% of the particles have a maximum dimension of no more than 500. This means that the maximum dimension of the particles in any direction should not exceed 500. Thus, if the filler is spherical, at least 50% of the spheres should be no more than 500 μm in diameter. If the filler is in the form of fibers, at least 50% of the fibers 30 should be no more than 500 μm in length. Preferably, virtually all filler particles should have a maximum dimension of no more than 500.

The maximum dimension of the preferred filler particles is determined by the shape of the filler. Thus, if the filler 35 is in the form of fibers, the maximum dimension of the fibers is preferably at most 100 μιη. On the other hand, if the filler is in the form of spheres or flakes or is of a vague shape, the maximum dimension of the filler particles is preferably at most 300 and more preferably in the range of 5 to 100.

In order to produce a hard tooth filling by curing the mixture, it is desirable that the filler particles have a Knoop hardness of at least 100. In general, the higher the hardness of the filler particles in the mixture, the higher the tooth filling hardness obtained when the mixture cures. would be at least 300, and more preferably at least 500. In general, the desired hardness, and in particular the preferred hardness, is characteristic of inorganic fillers.

The filler may be in the form of, for example, spheres, flakes, fibers or fibrous logs, or may be of indeterminate shape. Suitable fillers include, for example, apatite, soda glass, quartz, silica gel, borosilicate glass, synthetic sapphire (alumina-20 di), and opaque fillers such as barium and strontium oxide glasses.

The mixing of the ingredients can be performed by mixing the polymerizable substance and the filler together. However, the polymerizable material may be viscous and thus difficult to mix with the filler to achieve adequate mixing, whereby the polymerizable material can be conveniently diluted with a suitable diluent to reduce the viscosity so that adequate mixing of the filler is easier. After mixing, the diluent 30 can be removed, for example, by evaporation.

In order to produce a dental filling in which the filler adheres to a particularly well-cured polymerizable material in the filling, it is highly advantageous to treat the filler with a coupling agent capable of reacting with both the filler and the polymerizable material before filling.

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13 80381 mixing the tea and the polymerizable substance. The coupling agent should increase the strength of the bond between the filler in the filler and the polymerizable material.

Suitable coupling agents for use with glass include silanes, e.g., N-methacryloxypropyl-trimethoxysilane, N-aminopropyltriethoxysilane, and glycidoxypropyltrimethoxysilane.

The filler component of the composition of the invention may be a mixture of fillers to provide a dental filling or an artificial tooth with an optimal combination of physical properties, e.g. compressive strength, abrasion resistance. To achieve this, the preferred filler mixture contains 5 to 55%, preferably 5 to 25% of at least one single filler having an average particle size of less than 0.5 nm in its largest dimension and the remainder of the filler having an average particle size of more than 0.5 nm in its largest dimension. The above percentages are by volume of filler in the mixture of filler and polymerizable material.

The dental composition according to the invention is preferably packaged in separate small containers (e.g. with a capacity of 10 g) to allow treatment in the receiving room and to inadvertently reduce the risk of curing due to, for example, diffuse light. However, an amine-containing catalyst composition of the invention may, if desired, be packaged in two containers, one containing peroxide and the other amine together with other ingredients of the mixture such that when the contents of the two containers are mixed, e.g. in a dentist's office, the composition of the invention is formed; however, packaging in a single container is preferred.

For cosmetic purposes, the composition of the invention may have the appearance of a darkened, colored or natural tooth and therefore may contain small amounts of pigments, opacifiers and the like. The composition may also contain minor amounts of other substances such as antioxidants and stabilizers, provided that they do not substantially affect co-hydration.

It is preferred that the tooth surface be cleaned prior to application of the composition. The tooth can thus be cleaned, for example, by grinding with a rotating disc or brush or by etching using, for example, an aqueous solution of phosphoric acid. In the case of complex cavities, etching and beveling of the enamel edges improve the preservation and anatomical shape of the composite structure. The dental composition can be applied to the tooth, e.g. as a filling in the tooth cavity, and the polymerizable substance is then polymerized to form a hard substance. When the composition is used as a dental filler, it is preferred that the cavity liner be applied first. The liner can be anything commonly used in the field of composite filling, such as aqueous slurry cements of polycarboxylate and calcium hydroxide. Suitable lining cements are described in Journal of Dentistry, 6 (1979) 2, pages 117-125. In general, it is preferred to avoid linings such as zinc oxide-eugenol liners, which may affect the curing of the combination.

Since the photosensitive catalyst sensitizes the polymerizable substance and monomer in the light visible range, at 400 to 500 nm, the step of preparing the composition in which the photosensitive catalyst is added and the subsequent treatment, e.g. filling into tanks, should be performed in this range. completely absent. Most conveniently, the preparation can be carried out using light outside this range, for example provided by a sodium vapor lamp.

The invention is described with reference to the following Examples. The following experimental methods were used in the examples.

is 80 381

The curing time was determined according to British Standard 5199: 1975 (definition for resin-based dental fillings), section 6.4. Curing was achieved by exposing the test sample to an optical light guide 11 cm in length and 7 mm in diameter. Intensity was measured using a Macam Radiometer with a bandwidth of 470 nm ± 8 nm.

The light source was a tungsten halogen lamp 12 volts, 50 watts (Thorn Electrical), with a tuned reflector-10 tin And a two-color filter to remove UV radiation.

The Knoop hardness number (KHN) at varying depths of curing was determined by measuring the Knoop hardness along the length of the alloy sample in a mold irradiated at one end with the above light source. A 10 mm long metal mold was used, which had a flat surface And a 10 mm long, 3 mm wide and 1.5 mm deep groove on the surface. The groove was filled with the composition and the Mylar film and then the metal plate was placed and fixed on top of the composition. Excess composition was removed from the open end of the groove. The combination was then irradiated for a predetermined time using the above light source with the head of the optical light guide just without touching the mixture. After irradiation, the mixture was post-cured at 37 ° C. The metal plate and Mylar film were then removed. The power of the light source was standardized to 900 W / m2 for each 25-hour determination. The Knoop Hardness Number (KHN) was determined using a Zwick Hardness tester fitted with a Knoop Indentor, a 100 g load, and an X40 lens, at 0.25 mm intervals along the length (i.e., depth) of the cured sample in the groove. The KHN is used for the load divided by the area on which the sy-30 stretch is reflected. The results are plotted as a function of KHN depth.

Example 1

The condensate (35.2 g, 0.1 mol) obtained by reacting 2,2-bis- (4-hydroxyphenyl) propane and propylene oxide in a molar ratio of 1: 2 (oxy 80381 cipropylated bisphenol A), was dissolved in approximately 100 g of methylene dichloride, and the resulting solution was added dropwise to a solution of 33.6 g (0.2 moles) of hexamethylene diisocyanate in 100 g of methylene dichloride under a nitrogen atmosphere. 4 drops of dibutyltin dilaurate (available under the tradename "Mellite" 12, "Mellite" is a registered trademark) was added as a catalyst. The mixture was stirred under nitrogen for 1 hour, after which it was heated to reflux for 9 hours. The mixture was then cooled and a solution of 29 g (0.2 mol) of hydroxypropyl methacrylate in 100 g of methylene dichloride was added, after which the mixture was heated under reflux for 3 hours. The hydroxypropyl ester contained isomers in a weight ratio of 2.6 parts of 2-hydroxypropyl / 1 part of 1-methyl-2-hydroxyethyl. To the mixture of vinyl urethane and methylene chloride was added triethylene glycol dimethacrylate sufficiently to produce a polymerizable substance containing 50% by weight of vinyl urethane and 50% by weight of triethylene glycol dimethacrylate. Methylene chloride was removed by distillation.

A catalyst mixture containing camphorquinone, organic peroxide and dimethylaminoethyl methacrylate as described above was prepared by dissolving the ingredients in methylene chloride. The solution was added to the polymerized material; this and the following steps were performed in the light of a sodium discharge lamp.

The camphorquinone content was 0.3% by weight, the peroxide was 5% by weight and the dimethylaminoethyl methacrylate was 0.4% by weight based on the amount of polymerizable substance.

The filler was added to the above to give a final mixture containing 83% by weight of filler (barium aluminosilicate Raysorb T-3000 coated with silane A-174, Union Carbide Corporation). The final flowable mixture was then produced by removing the remaining methylene chloride using a twin roll n 80381 at ambient temperature and reduced pressure. The mixture as a function of the KHN cure depth was evaluated and the results are shown in the accompanying Figures 1-3: 5 Figure α-Diketone Peroxide Amine Cured- Post-aging time (s) time (h) 1 CQ dilauroyl-DMAEM 30 48 hyperoxide 10 2 CQ di- tert.bu- DMAEM 30 48 style perbenzoate 3 * CQ - DMAEM variable 24 CQ = camphorquinone 15 DMAEM = dimethylaminoethyl methacrylate * 1 for reference purposes.

The results show that the curing depth of the compositions according to the invention, as shown in Figures 1 and 2, is greater and more homogeneous than at the same irradiation time with the peroxide-free mixture (Figure 3).

Example 2

A series of mixtures were prepared by the method described in Example 1 to show the effect of catalyst mixture variation on cure time. The catalyst mixtures and curing time results are shown in the following table, in which the component concentrations are given in% by weight of the polymerizable substance. Measuring the cure time using the method described above results in a cure rate and quality.

18 80381

Peroxide

Formula X 10-hour α-diketone DMAEM Hardening half-life time (s) mistime- 5__temperature t. ° C ____ - I - CQ 1.0 55x) - - not curedx) CQ 1.0 0.4 17x ) dibenzoyl 2.7 72 - - not hardened3 ^ 15 dibenzoyl 2.7 72 CQ 1.0 0.05 10 dibenzoyl 2.7 72 CQ 1.0 0.4 5 2Q dilauroyl 5 '63 CQ 1.0 0, 2 10 perbenzoate 2.4 97 CQ 1.0 0.2 7 dibenzoyl 2.7 72 BZ 1.0 0.4 70 25 - BZ 1.0 - 300X) dibenzoyl 5 72 AC 1.0 0.4 85 30 - 5 - AC 1.0 - 170X ^ di-tert-butyl 2.4 126 [CQ 1.0 0.4 20

X

) outside the scope of the present invention for reference purposes only T, - CQ = camphorquinone BZ = benzyl AC = acenaphthquinone DMAEM = dimethylaminoethyl methacrylate 19 80381

The results given in the table show that the curing time of the mixtures increases in the following order: Peroxide alone> diketone + peroxide + amine and dike-Toni alone> diketone + peroxydiamine.

5 Example 3

Two mixtures (b and c) were prepared by the method of Example 1, except that the α-diketone, peroxide and amine were as follows: b) camphorquinone 1% tertiary butyl hydroperoxide 1% DMAEM 0.2% c) camphorquinone 1% tertiary butyl hydroperoxide 2.5% DMAEM 0.2% The cure times measured with the rheometer described above were: b) 15 seconds c) 15 seconds compared to the cure times obtained in Example 2 above with camphorquinone alone (55 seconds) and camphorquinone / DMAEM (17 seconds).

Example 4

Two mixtures (a and b) were prepared by the method of Example 1 not only that the mixture also contained 0.5% by weight of 25% of the mixture "Aerosil" R 972 (Degussa, West Germany) and that the catalyst content was as follows: a) camphorquinone 0.3% DMAEM 0.4% b) camphorquinone 0.3% DMAEM 0.3% t-butyl perbenzoate 1.5% wherein the percentages of the catalyst component are based on the amount of polymerizable substance.

Figure 4 shows the variation in the depth of cure of the mixtures (a as a solid line, b as a dashed line) at irradiation times of 80381 20 la (a) 20 seconds and (b) 15 seconds. The results show that the cure depth and hardness associated with the catalyst of the present invention are greater than those obtained with the α-diketone-organic amine system.

Example 5

Two mixtures (a and b) were prepared by the method of Example 1 except that the catalyst content was as follows: a) fluorenone 0.25% DMAEM 0.5% b) fluorenone 0.25% DMAEM 0.5% t-butyl perbenzoate 2.5% 15 wherein the percentages of catalyst component are based on the polymerizable substance.

Figure 5 shows the variation of the curing depth with the mixture (a solid line, b dashed line) irradiated for 60 seconds using a light intensity of 1000 watts / m2 measured at 470 nm. The results show that the depth of cure and strength of the present blends are superior to those having fluorenone as the catalyst system and an organic reducing agent alone.

Example 6 The variation in surface hardness of the mixtures of Example 4 was studied over the curing time range using a light source with an intensity of 970 watts / m2 measured at 470 nm. Surface hardness was measured from the samples after aging in water at 37 ° C for 24 hours after irradiation (seconds). The results are shown in Fig. 6, which shows that the mixture (b) according to the present invention reaches the maximum surface hardness with shorter irradiation times than the mixture (a) with an α-diketone and an organic amine catalyst system.

35 Example 7

The mechanical properties of the two mixtures (a and b) of 21 80381 prepared by the method of Example 1 were determined at varying times from curing. Curing was achieved by irradiating (a) for 20 seconds and (b) for 15 seconds using a light intensity of 1000 watts-5 t / m2 measured at 470 nm a) camphorquinone 0.3% DMAEM 0.4% b) camphorquinone 0.3 % DMAEM 0.3% 10 t-butyl perbenzoate 1.5% where the percentages of the catalyst component are based on the amount of polymerizable substance.

The values of mechanical properties 1/2 hour, 1 hour and 24 hours after curing are shown in the following table: (a) (b)

Compression 1/2 hour 26.1 ± 4.27 279.4 ± 7.73 strength (N / nun2) 1 hour 270.0 + 8.73 310.1 ± 9.24 20 24 hours 308.2 ± 7 , 41,317.8 ± 6.08

Diameter 1/2 hours 38.4 + 2.06 51.6 ± 0.63 lines 1 hour 43.3 + 3.87 55.5 ± 1.52 cheese 25 (N / mm2) 24 hours 52, 9 ± 3.97 57.9 ± 1.10

Bending 1/2 hours 108.2 ± 6.48 144.8 ± 10.60 hours 1 hour 119.3 ± 7.76 161.8 ± 12.16 cheese 24 hours 152.6 ± 7.63 154, 0 ± 13.13 30 (N / mm2)

Elastic- 1/2 hours 9.46 ± 0.63 15.51 ± 1.28 coefficient 1 hour 12.27 ± 0.89 16.01 ± 0.54 (GPa) 24 hours 13.71 ± 0.39 14 , 99 ± 0.77 35 22 8 0 3 81

The results show that the compositions according to the invention reach their maximum mechanical properties earlier and that the maximum is higher than for mixtures with camphorquinone alone / organic amine as catalyst.

The mechanical properties were determined with a Hovrden Testing device type EU 5 BS as follows: 1. Flexural strength and modulus of elasticity. After being immersed in deionized water for 24 hours (except Example 1) at 37 ° C, the samples were blotted dry and allowed to equilibrate at room temperature for 10 minutes. The rough edges of the samples were carefully ground using an emery cloth grade 0. The cross-sectional dimensions of each sample were determined using 15 micrometers. A three-point bending test was then performed on each sample using a 200 N load cell and a crosshead speed of 1.0 ± 0.05 mm / minute. The load at the fracture point was recorded and the flexural strength (FS) was calculated according to the following formula: 20 FS - 3PL N / mm2 2bd2 where P is the load at the fracture (N) 25 L is the distance between the supports (mm to the nearest 0,01 mm) b is the width of the sample (mm to the nearest 0,01 mm) d is the depth of the sample (mm to the nearest 0,01 mm)

The coefficient of elasticity (FM) was calculated according to the following formula: 30 P1 L3 FM «- GPa 4bd3 y 35 where L, b and d are as defined above, y is the deflection (mm) of the tensile point (mm) in the test machine and p1 is the load deflection the load of the linear part, which corresponds to the deviation y.

2. Compressive strength. After being immersed in deionized water for 24 hours at 37 ° C, the samples were

dried on tissue paper and allowed to equilibrate at room temperature for 10 minutes. The diameter was measured with a micrometer, each sample was placed in a vertical position between two parallel planes of the experimental machine and compressed until fracture. Load breaking (P

measured in Newtons) was recorded and the compressive strength (CS) was calculated according to the following formula: CS - _P N / mra2 15 n r2 where r is the radius of the cross - section of the sample (measured in mm to the nearest 0,01 mm).

3. Diameter tensile strength. After being immersed in water for 24 hours at 37 ° C, the samples were dried with tissue paper and allowed to equilibrate at room temperature for 10 minutes. The length and diameter of each sample were measured using a micrometer. Each specimen was placed sideways between two parallel plane plates of the test machine and compressed at 1.0 ± 25 0.05 mm / min, the load at fracture (T measured in Newtons) was recorded, and the diametrical tensile strength (TS) was calculated according to the following formula: 30 TS * 2T N / mm2

π DL

where D and L are the diameter and length of the sample (measured in mm to the nearest 0,01 mm).

When evaluating each of the above properties 35, an average of 12 sample results was taken and each 24 80381 value that was more than 15% less than the mean was discarded. The mean of the remaining samples was recorded as the standard deviation. The experiments were repeated if more than 3 samples were rejected.

5

Claims (9)

25 80381 A visible light curable dental composition comprising at least one polymerizable ethylenically unsaturated substance, 40% to 90% by weight of the composition of at least one finely divided filler and a visible light sensitive catalyst, characterized in that the catalyst comprises (i) at least one a ketone having a photosensitive catalytic activity selected from fluorenone and α-diketones of the formula ACCA, wherein the groups A may be the same or different and are hydrocarbon or substituted hydrocarbon groups, and wherein the groups A may be further linked together by a divalent linkage or via a divalent hydrocarbon or substituted hydrocarbon group, or wherein the groups A together may form a fused aromatic ring system, (ii) at least one organic peroxide having a ten hour half-life temperature of less than 15; 0 eC 25 and of the formula ROOR, wherein the groups R may be the same or different and are hydrogen, alkyl, aryl or acyl groups, where at most one of the groups R is hydrogen, and (iii) a reducing agent which is an organic amine capable of to reduce the ketone while it is in the excited state of 30. Composition according to Claim 1, characterized in that the reducing agent is an organic amine of the formula R 43 N, in which the groups R 4, which may be the same or different, are hydrogen atoms, hydrocarbon groups, substituted hydrocarbon groups or groups in which 26 80 381 two the units R4 together with the nitrogen atom form a cyclic ring system in which at most two of the units R4 are hydrogen atoms and if the nitrogen atom is directly attached to the aromatic group R4, at least one of the other 5 units R4 has a group -c- H10 attached to the nitrogen atom. Composition according to Claim 1 or 2, characterized in that the α-diketone is camphorquinone. Composition according to one of Claims 1 to 3, characterized in that the ketone content is between 0.01 and 2% by weight of the polymerizable substance. Composition according to one of Claims 1 to 4, characterized in that the content of organic peroxide is 0.1 to 20% by weight of the polymerizable substance. Composition according to one of Claims 1 to 5, characterized in that the organic peroxide is tertiary butyl perbenzoate. Method for curing a composition according to any one of claims 1 to 6, characterized in that the composition is irradiated with visible light having a wavelength in the range of 400 to 500 nm. Process for producing a composition according to one of Claims 1 to 6, characterized in that the ingredients are mixed after the addition of the photosensitive catalyst, excluded from visible light having a wavelength in the range from 400 to 500 nm. Use of a visible light curable dental composition according to any one of claims 1 to 6 or produced by the method of claim 8 as a dental filling material. 27 80381