pH sensitive microcapsules for dental use

Abstract

The present invention relates to a dental composition comprising: a polymerizable component without an acidic moiety, and microcapsules comprising a first component of a water-insoluble redox initiator system and a pH-sensitive inorganic component, the microcapsules being free of polymeric material. The present invention also relates to the use of certain microcapsules for preparing a curable dental composition and a method for curing the dental composition, as well as a device for storing the dental composition.

Description

Technical Field

[0001] The present invention relates to a dental composition comprising a polymerizable component and microcapsules comprising a pH-sensitive component and components of a redox initiator system. Background Art

[0002] The use of microcapsules for storing components, such as components of redox initiator systems, is generally known.

[0003] US 5,154,762 (Mitra et al.) relates to an aqueous, ionically hardenable, photocurable, ethylenically unsaturated dental cement comprising a) a finely divided acid-reactive filler, b) a water-miscible acidic polymer, c) a photoinitiator, d) a water-soluble reducing agent and a water-soluble oxidizing agent, wherein the reducing agent or the oxidizing agent may be contained in microcapsules. It is suggested to use a medically acceptable polymer and a film-forming agent as encapsulating agent.

[0004] WO 2019 / 234661 A1 (3M IPC) describes a two-part hardenable dental composition comprising a first part comprising a composition comprising a liquid material and an encapsulating material comprising a base core material and an inorganic shell material comprising a metal oxide surrounding the core, and a second part comprising a composition comprising a liquid material. It is stated that the encapsulated alkaline material is generally not a reducing agent for a redox curing system because this would delay the redox curing reaction.

[0005] US 2020 / 368117 A1 (Claussen et al.) relates to a microcapsule comprising a hollow or porous core composed of a polymer material and comprising components of a redox initiator system, and a shell composed of a pH-sensitive material. It is summarized that the cross-linked matrix of the polymer material is sufficiently stable to withstand the shear forces generated during mixing.

[0006] This technique is particularly useful for preparing powder compositions. However, compared to paste / paste systems, powder compositions are easier to prepare and stabilize due to the physical separation of the powder components to be mixed.

[0007] In contrast, pasty compositions are usually produced by kneading methods, in which high shear forces are applied to the microcapsules.

[0008] Microcapsules described in the art, in particular those proposed for storing components of redox initiator systems, are generally not stable enough to withstand such high shear forces.

[0009] On the other hand, when mixing pastes / paste compositions, the mixing forces applied are often not strong enough to break up the microcapsules to enable release of the active agent.

[0010] Therefore, the techniques suggested for preparing powder compositions cannot usually be used for paste / paste compositions.

[0011] Other references describing the use and preparation of microcapsules include:

[0012] US 2016 / 0088836 A1 (Sahouani et al.) describes polymer composite particles that can be used to store and deliver various bioactive agents. The polymer composite particles include a porous polymer core and a coating surrounding the polymer core.

[0013] WO 2007 / 013794 A1 (Stichting Gronignen Centre for Drug Research) describes a pH-controlled pulsed release system comprising a core surrounded by a coating layer, wherein the core comprises the active substance and the coating layer comprises a pH-sensitive coating material in which a swelling agent is embedded. Sodium starch glycolate is suggested as the swelling agent.

[0014] US 6,022,501 (Dexter et al.) relates to pH-sensitive microcapsules containing a water-immiscible active ingredient within a shell wall, wherein the shell wall has free carboxylic acid groups incorporated therein.

[0015] Jun Wang et al. describe calcium carbonate / carboxymethyl chitosan hybrid microspheres for drug delivery, in particular for water-soluble anticancer drug delivery, in J. Phys. Chem C 2010, 114, 18940-18945.

[0016] Sukhorukov et al. describe porous calcium carbonate microparticles as templates for encapsulating biologically active compounds, in particular biomacromolecules, in J. Mater. Chem., 2004, 14, 2073-2081.

[0017] Yu et al. in Applied Energy 114 (2014), 632-643 describe a method of microencapsulating n-octadecane phase change materials with a calcium carbonate shell to improve thermal conductivity and service durability. Summary of the invention

[0018] There is a need for microcapsules that can be used to produce storage-stable pasty compositions.

[0019] There is also a need for microcapsules which are mechanically stable enough to allow the microcapsules to be processed in kneading equipment and to allow the release of agents or components stored in the microcapsules on demand.

[0020] Furthermore, the release of the component to be released should be rapid enough on demand.

[0021] It would also be ideal if the setting behavior of the composition was not negatively affected.

[0022] If possible, the microcapsules should also allow a high loading of the components to be stored in the microcapsules.

[0023] One or more of these objects are addressed by the microcapsules and related methods described in the claims and herein.

[0024] In one embodiment, the invention features a dental composition comprising: a polymerizable component that is free of an acidic moiety, and microcapsules comprising a water-insoluble first component comprising a redox initiator system and a pH-sensitive inorganic component, the microcapsules being free of polymeric material, the pH-sensitive inorganic component preferably forming a shell around a core comprising the water-insoluble first component.

[0025] The present invention also relates to the use of the microcapsules described herein for preparing a curable dental composition.

[0026] Furthermore, the present invention relates to a method for curing the dental composition described herein, comprising the steps of combining a base paste and a catalyst paste, wherein an acidic component is contacted with microcapsules comprising a first component of a redox initiator system and reacts with the pH-sensitive inorganic component of the microcapsules, wherein the pH-sensitive inorganic component of the microcapsules is dissolved and the water-insoluble first component of the redox initiator system is released.

[0027] The invention also relates to a device for storing a dental composition.

[0028] Furthermore, the present invention relates to a kit comprising the dental composition described herein and the following components, alone or in combination: a dental milling block for machining a dental restoration, a dental adhesive.

[0029] Additionally, the invention features a dental composition as described herein for use in a method of restoring a tooth in a patient's mouth, the method comprising the steps of providing the dental composition in the form of a kit comprising a base paste and a catalyst paste, mixing the base paste and the catalyst paste, and applying the mixture to a surface of a prepared tooth to be restored.

[0030] Unless otherwise defined, for the purposes of this specification, the following terms shall have the given meanings:

[0031] An "initiator" is a substance that is capable of initiating a chemical reaction, preferably by a free radical reaction. An initiator may be a single compound, or may comprise more than one component, such as a combination of a sensitizer and a reducing agent. Depending on the reaction conditions selected (e.g., pH>7 or pH<7), different initiators may be preferred.

[0032] A "redox initiator system" is defined as a combination of a reducing agent and an oxidizing agent. If present, a transition metal component is also considered a component of the redox initiator system.

[0033] As used herein, "hardening" or "curing" are used interchangeably and refer to polymerization and / or cross-linking reactions, including, for example, photopolymerization reactions involving one or more materials included in the composition and chemical polymerization techniques (e.g., ionic reactions or chemical reactions that form free radicals effective to polymerize ethylenically unsaturated compounds).

[0034] "Dental article" means an article to be used in the dental field, in particular as or for the preparation of a dental restoration. Dental articles generally have two different surface parts, an outer surface and an inner surface. The outer surface is the surface that is generally not in permanent contact with the tooth surface. In contrast, the inner surface is the surface that is used to attach or fix the dental article to the tooth. If the dental article has the shape of a crown, the inner surface generally has a concave shape, while the outer surface generally has a convex shape. Dental articles should not contain components that are harmful to the patient's health and therefore do not contain hazardous and toxic components that can migrate from the dental article or orthodontic article.

[0035] A "dental composition" or "composition for dental use" or "composition to be used in the dental field" is any composition that can be used in the dental field. In this respect, the composition should be harmless to the patient's health and therefore contain no hazardous and toxic components that can migrate from the composition. Examples of dental compositions include permanent and temporary crown and bridge materials, artificial crowns, anterior or posterior filling materials, adhesives, mill blanks, laboratory materials, bonding agents and dental orthodontic devices. Dental compositions are typically hardenable compositions that can harden under ambient conditions including a temperature range of 15°C to 50°C or 20°C to 40°C within a time range of 30 minutes or 20 minutes or 10 minutes. Higher temperatures are not recommended because they may cause pain to the patient and may be detrimental to the patient's health. Dental compositions are typically provided to practitioners in relatively small volumes, i.e., volumes in the range of 0.1 ml to 100 ml or 0.5 ml to 50 ml or 1 ml to 30 ml. Therefore, the storage volume of the available packaging device is within these ranges.

[0036] "Dental restoration" means a dental article used to repair a tooth to be treated. Examples of dental restorations include crowns, bridges, inlays, onlays, veneers, caps, copings, crown and bridge frameworks and parts thereof.

[0037] The term "compound" or "component" refers to a chemical substance having a specific molecular formula or consisting of a mixture of substances such as a polymeric substance.

[0038] A "polymerizable component" is any component that can be cured or hardened, for example by heating to cause polymerization or chemical crosslinking, or for example by radiation-induced polymerization or crosslinking, or for example using a redox initiator or by any other free radical forming method. A free radical polymerizable component may contain only one, two, three or more free radical polymerizable groups. Typical examples of free radical polymerizable groups include unsaturated carbon groups, such as vinyl groups present in, for example, (meth)acrylate groups.

[0039] A "monomer" is any chemical species characterizable by a chemical formula, with free radical polymerizable unsaturated groups (including (meth)acrylate groups) that can be polymerized into oligomers or polymers to increase molecular weight. The molecular weight of a monomer can usually be simply calculated based on a given chemical formula.

[0040] "Polymer" or "polymeric material" are used interchangeably to refer to homopolymers, copolymers, terpolymers, and the like.

[0041] A "derivative" or "structural analogue" is a compound that exhibits a chemical structure that is closely related to a corresponding reference compound, and that contains all of the characteristic structural elements of the corresponding reference compound, but with minor changes compared to the corresponding reference compound, such as with additional chemical groups, such as alkyl moieties, Br, Cl or F, or without chemical groups, such as alkyl moieties. In other words, a derivative is a structural analogue of a reference compound. A derivative of a compound is a compound that contains the chemical structure of the compound.

[0042] As used herein, "(meth)acryloyl" is a shorthand term that refers to "acryloyl" and / or "methacryloyl." For example, a "(meth)acryloyloxy" group is a shorthand term that refers to an acryloyloxy group (i.e., CH2=CH-C(O)-O-) and / or a methacryloyloxy group (i.e., CH2=C(CH3)-C(O)-O-).

[0043] A composition comprising an "ascorbic acid moiety" is a composition comprising the following structural elements:

[0044]

[0045] The symbol "*" indicates a connection to another chemical moiety or atom.

[0046] "Particle" means a solid substance having a geometrically determinable shape. The shape may be regular or irregular. Particles can often be analyzed in terms of, for example, particle size and particle size distribution.

[0047] The particle size (d50) of the powder can be obtained from the cumulative curve of the grain size distribution. The corresponding measurement can be performed using a commercially available particle size meter (e.g., Malvern Mastersizer 2000). "D" represents the diameter of the powder particles, and "50" refers to the volume percentage of the particles. Sometimes, 50% is also expressed as "0.5". For example, "(d50) = 1 μm" means that 50% of the particles have a size of 1 μm or less.

[0048] "Environmental conditions" means the conditions to which the compositions described herein are typically subjected during storage and handling. Environmental conditions may be, for example, a pressure of 900 mbar to 1,100 mbar, a temperature of 10°C to 40°C, and a relative humidity of 10% to 100%. In the laboratory, environmental conditions are typically adjusted to 20°C to 25°C and 1,000 mbar to 1,025 mbar (at sea level).

[0049] As used herein, "one (kind)", "the / said", "at least one (kind)" and "one (kind) or more (kinds)" are used interchangeably. In addition, in this article, the numerical ranges expressed by endpoints include all numerical values ​​contained in the range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0050] Adding the plural form "(s)" to a term means that the term should include both the singular and the plural. For example, the term "additive" means one additive and multiple additives (eg, 2, 3, 4, etc.).

[0051] Unless otherwise indicated, all numbers expressing quantities of ingredients, measurements of physical properties such as described below, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about."

[0052] The terms "comprising" or "containing" and variations thereof do not have a limiting meaning where these terms appear in the specification and claims. "Consisting essentially of means that certain additional components may be present, i.e., those components that do not materially affect the basic characteristics of the article or composition. "Consisting of means that no additional components should be present. The term "comprising" shall also include the terms "consisting essentially of" and "consisting of."

[0053] A composition is "substantially or substantially free of" a certain component if the composition does not contain the component as an essential feature. Thus, the component is not arbitrarily added to the composition or is not arbitrarily combined with other components or ingredients of other components. A composition that is substantially free of a certain component generally does not contain the component at all. However, the presence of a small amount of the component is sometimes unavoidable, for example due to impurities contained in the raw materials used. DETAILED DESCRIPTION

[0054] It has been discovered that the compositions described herein have several advantageous properties.

[0055] The microcapsules are sufficiently mechanically stable and withstand the shear forces which usually occur during production processes involving kneading steps, for example when preparing pasty compositions.

[0056] The microcapsules contain pH-sensitive components, ie components that undergo a chemical reaction, in particular an acid / base reaction, if the pH changes. Specifically, pH sensitivity refers to sensitivity to an acidic environment.

[0057] Due to this property, the microcapsules described herein may also be considered as pH sensitive microcapsules.

[0058] An example of a pH sensitive component is a component that dissolves when in contact with an acidic component or generates gas when exposed to an acidic component. Such a component is particularly useful because it enables rapid release of the component to be released from the microcapsule in need thereof. If gas is generated, the gas helps to widen, perforate and / or rupture the microcapsule.

[0059] This may be advantageous, for example, if the redox initiator system is included in a dental two-part paste / paste composition containing an acidic component.

[0060] Thus, the microcapsules described herein may help overcome challenges associated with, for example, the production of redox-curable pastes / paste compositions.

[0061] In order to produce storage-stable pastes / paste compositions comprising a redox initiator system, a rapid release of the redox initiator component is often required to ensure that the curable composition hardens within a suitable time.

[0062] Compared to microcapsules described in the prior art, the microcapsules described herein allow for considerably higher loadings of components to be released, since the components are directly encapsulated without the need for additional shells or layers.

[0063] Therefore, in order to provide a sufficient amount of the component to be released, a lower amount of microcapsules is required. This may be advantageous in applications where the amount of shell material used may have an impact. For example, in a dental curable composition, the presence of too high an amount of shell material may have a negative impact on the aesthetics of the cured composition.

[0064] The present invention relates to a dental composition comprising a polymerizable component and microcapsules comprising a water-insoluble first component of a redox initiator system.

[0065] The microcapsules may generally be characterized by the following features, alone or in combination: diameter: 1 μm to 200 μm, or 1 μm to 100 μm, or 5 μm to 100 μm, or 5 μm to 50 μm, or 5 μm to 25 μm; are mechanically stable.

[0066] It is sometimes preferred to use microcapsules having a diameter in the range of 1 μm to 100 μm.

[0067] It has also been found that by using components with a small particle size, the reaction between the acidic component and the pH-sensitive component of the microcapsule can be improved as the reaction surface is increased.

[0068] The shape and diameter can be assessed by microscopy, in particular by scanning electron microscopy (SEM). If desired, the diameter and particle size distribution can be determined by light scattering.

[0069] Microcapsules are mechanically stable if they can withstand the high shear forces which usually occur during the preparation of pastes in mixing or kneading machines. Suitable tests are described in the Examples section.

[0070] Mechanical stability can be achieved, for example, if the microcapsules comprise predominantly inorganic components and the presence of polymeric materials is avoided.

[0071] The microcapsules contain a pH-sensitive inorganic component.

[0072] Without wishing to be bound by a particular theory, it is believed that the use of an inorganic component is beneficial because these microcapsules tend to be more mechanically stable than microcapsules comprising or consisting essentially of polymeric materials.

[0073] The pH-sensitive inorganic component forms a shell around a core of a water-insoluble first component comprising a redox initiator system.

[0074] The presence of the pH-sensitive inorganic component helps to promote the release of the component to be released and stored in the microcapsules, especially if the microcapsules are brought into contact with an acidic or alkaline environment.

[0075] The pH sensitive inorganic components generally contain anions and multivalent cations.

[0076] The anion is typically selected from carbonate, bicarbonate, phosphate, nitrate and sulfate.

[0077] The multivalent cations are typically selected from ions of Mg, Ca, Sr, Ba, Al and Zn.

[0078] Examples of pH-sensitive inorganic components include MgCO3, CaCO3, ZnCO3, Ca(HCO3)2, CaSO4, and MgSO4.

[0079] If the pH-sensitive inorganic component generates a gas upon contact with an acidic environment, the release of this component can be even further improved.

[0080] If such microcapsules are brought into contact with an acidic environment, not only are the pH-sensitive components decomposed or dissolved, but also the generated gas accelerates the decomposition.

[0081] The component that generates gas when contacting acid generally comprises a moiety selected from carbonate or bicarbonate. The gas generated is generally CO2.

[0082] Examples of components that generate gas when exposed to acid include, in particular, alkaline earth metal (eg, Mg, Ca) carbonates or bicarbonates and Zn carbonates and bicarbonates, such as MgCO 3 , CaCO 3 , ZnCO 3 , and mixtures thereof.

[0083] The use of the following components is sometimes preferred as they have proven to be very effective for the desired purpose: CaCO3, Ca(HCO3)2.

[0084] If the microcapsules are to be used in the medical or dental fields, the components should be sufficiently biocompatible and substantially non-toxic in the amounts employed.

[0085] The microcapsules contain the component to be released. The component to be released is contained in the microcapsules, in particular in the core of the microcapsules.

[0086] Any type of component to be released that does not adversely interact with the pH-sensitive inorganic material of the microcapsules can be stored in the microcapsules.

[0087] According to one embodiment, the microcapsules comprise a first component of a redox initiator system. Such components are sometimes referred to as active agents.

[0088] The first component of the redox initiator system is water-insoluble.

[0089] Water-insoluble means that the solubility of the component is less than 0.1 g / 100 ml water or less than 0.05 g / 100 ml water (23° C.).

[0090] Suitable methods for determining the solubility of components in water are given in the Examples section.

[0091] Furthermore, the first component of the redox initiator system is usually provided as a solid component. That is, the first component is provided in the form of particles.

[0092] The first component of the redox initiator system can be suspended in water under stirring.

[0093] Redox initiator systems generally comprise an oxidizing agent and a reducing agent and sometimes a transition metal.

[0094] According to one embodiment, the microcapsules contain a water-insoluble oxidizing agent.

[0095] The nature and structure of the oxidizing agent are not particularly limited unless the desired results cannot be achieved.

[0096] Suitable oxidizing agents include water-insoluble organic peroxide and persulfate components and mixtures thereof.

[0097] In general, all water-insoluble peroxides which can be incorporated or absorbed by the microcapsules can be used, in particular organic peroxides.

[0098] Organic peroxides which may be used include hydroperoxides, ketone peroxides, diacyl peroxides, dialkyl peroxides, peroxyketals, peroxyesters and peroxydicarbonates.

[0099] Useful diperoxides include diperoxides containing the moiety R1-OO-R2-OO-R3, wherein R1 and R3 are independently selected from H, alkyl (e.g., C1 to C6), branched alkyl (e.g., C1 to C6), cycloalkyl (e.g., C5 to C6), 10 ), alkylaryl (e.g. C7 to C 12 ) or aryl (e.g. C6 to C 10 ), and R2 is selected from an alkyl group (eg, C1 to C6) or a branched alkyl group (eg, C1 to C6).

[0100] Examples of the ketone peroxide include methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, methyl cyclohexanone peroxide, and cyclohexanone peroxide.

[0101] Examples of peroxyesters include cumyl peroxyneodecanoate, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, 2,2,4-trimethylpentyl peroxy-2-ethylhexanoate, t-pentyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxyisophthalate, di-t-butyl peroxyhexahydroterephthalate, t-butyl peroxy-3,3,5-trimethylhexanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butylperoxymaleic acid.

[0102] Examples of the peroxydicarbonate include di-3-methoxy peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, diisopropyl 1-peroxydicarbonate, di-n-propyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, and diallyl peroxydicarbonate.

[0103] Examples of the diacyl peroxide include acetyl peroxide, benzoyl peroxide, decanoyl peroxide, 3,3,5-trimethylhexanoyl peroxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.

[0104] Examples of the dialkyl peroxide include di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,3-bis(tert-butylperoxyisopropyl)benzene, and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexane.

[0105] Examples of peroxyketals include 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, 2,2-bis(tert-butylperoxy)octane, and n-butyl 4,4-bis(tert-butylperoxy)valerate.

[0106] According to one embodiment, the organic peroxide is a hydroperoxide, in particular a hydroperoxide comprising the moiety ROOH, wherein R is (e.g. C1 to C 20 ) alkyl, (e.g. C3 to C 20 ) branched alkyl, (e.g. C6 to C 12 ) cycloalkyl, (e.g. C7 to C 20 ) alkylaryl or (e.g. C6 to C 12 )aryl.

[0107] Examples of suitable organic hydroperoxides include tert-butyl hydroperoxide, tert-amyl hydroperoxide, p-diisopropylbenzene hydroperoxide, cumene hydroperoxide, pinane hydroperoxide, p-methane hydroperoxide, and 1,1,3,3-tetramethylbutyl hydroperoxide.

[0108] Suitable peroxydisulfate components and / or peroxydiphosphate components and / or mixtures thereof that may be used comprise organic components and / or inorganic components.

[0109] Suitable examples include ammonium, sodium and potassium peroxodisulfate components and / or ammonium, sodium and potassium peroxodiphosphate components. Sodium peroxodisulfate is sometimes preferred.

[0110] According to another embodiment, the microcapsules contain a water-insoluble reducing agent.

[0111] The nature and structure of the water-insoluble reducing agent are not particularly limited unless the desired result cannot be achieved.

[0112] Suitable reducing agents include organic and inorganic components, and mixtures thereof.

[0113] The reducing agent is generally solid under ambient conditions (23° C.; 1013 hPa).

[0114] The reducing agent that may be contained in the core of the microcapsule includes water-insoluble ascorbic acid components, tertiary amine components, sulfinate components, sulfite components, borane components, (thio)urea components and (thio)barbituric acid components, saccharin, and metal salts thereof.

[0115] Sometimes preferred are one or more components containing ascorbic acid moieties, such as salts and esters of ascorbic acid, ethers, ketals or acetals. These components are referred to as ascorbic acid components.

[0116] Suitable salts include alkali metal salts and alkaline earth metal salts, such as Na, K, Ca and mixtures thereof.

[0117] Esters of ascorbic acid include those prepared by reacting one or more of the hydroxyl groups of ascorbic acid with a carboxylic acid, particularly a C2 to C 30 Those formed by reaction of carboxylic acids.

[0118] C2 to C 30 Suitable examples of carboxylic acids include fatty acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleic acid, palmitoleic acid, hexadecenoic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, trans-linoleic acid, α-linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid.

[0119] Particularly preferred are those ascorbic acid components which are readily soluble in or admixed with the remaining resin matrix comprising the polymerizable components.

[0120] That is, it may sometimes be preferred to use an ascorbic acid component having a hydrophobic portion. Suitable hydrophobic portions include saturated and unsaturated aliphatic residues (e.g., C2 to C 30 or C 12 To C 30 Those ascorbic acid components can also be used as surface-active substances (substances with a so-called "head / tail structure"). Ascorbyl palmitate, ascorbyl stearate, mixtures thereof and salts thereof are sometimes particularly preferred.

[0121] If the oxidizing agent is brought into contact with the reducing agent, a redox reaction will generally begin. This redox reaction is suitable for initiating the curing of the curable component, thereby resulting in crosslinking of the curable component.

[0122] If desired, the microcapsules may also be additionally filled with other components, such as dyes, fluoride release agents. Suitable dyes and fluoride release agents are described below.

[0123] Typically, the content of the pH-sensitive component in the microcapsules is greater than the content of the first component of the redox initiator system. The larger the particles of the first component of the redox initiator system, the lower the amount of the pH-sensitive component.

[0124] A weight ratio of the pH sensitive component of the microcapsules to the first component of the redox initiator system in a range of less than 20:1, or less than 10:1, or less than 5:1, or less than 3:1 has been found to be useful.

[0125] Such a ratio was found to be beneficial as it provides a good balance between the amount of the desired redox initiator component to be released and the components used to produce the microcapsules, which is not always required in the final composition.

[0126] The microcapsules described herein allow for the incorporation or loading of the first component of the redox initiator system in an amount of up to 50% by weight or up to 40% by weight relative to the weight of the microcapsule.

[0127] If desired, the mass or amount of the shell can be calculated using the following formula:

[0128] D= d p +2x Shell Thickness

[0129] V 壳 = V 总 -V p

[0130] ( V 壳 / V p )=( V 总 / V p )-1

[0131] =(D3 / d p 3 )-1

[0132] ρ 壳 = m 壳 In 壳

[0133] ρ p =m p / V p

[0134] m 壳 =m p (ρ 壳 / ρ p )[(D 3 / d p 3 )-1]

[0135] D is the diameter of the microcapsule, d p is the diameter of the particles contained in the microcapsule, m 壳 is the mass of the shell, p 壳 is the density of the shell material, p p is the density of the core particle, V 壳 is the volume of the shell, V 总 is the total volume of the microcapsules, V p is the volume of the particles contained in the microcapsule.

[0136] The microcapsules containing the first component of the redox initiator system are present in the dental composition in an amount effective to initiate curing of the polymerizable component in the presence of the second component of the redox initiator system.

[0137] The dental composition generally contains microcapsules in an amount of 0.05 to 10 wt %, or 0.1 to 5 wt %, or 0.2 to 3 wt %, or 0.3 to 2 wt % relative to the dental composition.

[0138] The microcapsules described herein can be produced as follows:

[0139] A composition comprising water, a surfactant, a water-insoluble component (eg, a first component of a redox initiator system), and a water-soluble pH-sensitive inorganic component (comprising a monovalent cation) is provided.

[0140] The composition is mixed.

[0141] The mixture (dispersion) was centrifuged and the precipitated portion was separated.

[0142] The separated fraction is combined with an aqueous solution containing a water-soluble salt comprising a multivalent (particularly divalent) cation.

[0143] The resulting composition (dispersion) is mixed again, centrifuged, and the precipitated fraction is separated, further purified if necessary (eg by resuspending in water and filtering), and dried.

[0144] The addition of a surfactant is often advantageous because it can help obtain a more uniform distribution of the components in the mixture.

[0145] Since the water-insoluble component does not dissolve in water, it forms a suspension in water.

[0146] Without wishing to be bound by a particular theory, it is believed that the surfactant forms micelles containing the water-insoluble components of the redox initiator system and thus stabilizes these components in aqueous solution or the environment.

[0147] There is no particular restriction on the nature of the surfactant unless the desired effect cannot be achieved.

[0148] Suitable surfactants include ionic surfactants (eg, sulfates, sulfonates, phosphates, carboxylates, quaternary ammonium salts), amphoteric surfactants (eg, sulfobetaines, betaines) and nonionic surfactants, among which nonionic surfactants are preferred.

[0149] Nonionic surfactants generally have a covalently bonded oxygen-containing hydrophilic group bonded to a hydrophobic parent structure. Nonionic surfactants tend to be less foaming than other surfactants.

[0150] Examples of nonionic surfactants that can be used include alkyl polyglycosides, fatty amine ethoxylates, fatty alcohol ethoxylates, fatty acid alkanolamides, castor oil ethoxylates, alcohol ethoxylates / propoxylates, and blends thereof (e.g., blends of decyl glucoside and undecyl glucoside; APG TM 325, BASF).

[0151] If a surfactant is used, it is typically used only in small amounts, such as 2 to 10 wt %, or 5 to 8 wt %, relative to the amount of pH sensitive components formed during the production process.

[0152]

[0013] The dental compositions described herein include a polymerizable component.

[0153] Polymerizable components include components having at least one or two polymerizable moieties such as (meth)acrylate moieties.

[0154] The crosslinking or polymerization of the polymerizable components can be initiated by using redox initiator systems.

[0155] The polymerizable component does not contain an acidic moiety.

[0156] The polymerizable component not containing an acidic moiety is generally a free radical polymerizable material including ethylenically unsaturated monomers, monomers or oligomers or polymers.

[0157] Suitable polymerizable component(s) not containing an acidic moiety can be characterized by the formula:

[0158] A n BA m

[0159] wherein A is an ethylenically unsaturated group, such as a (meth)acryloyl moiety,

[0160] B is selected from (i) a linear or branched C1 to C 12 Alkyl, which is optionally substituted with other functional groups (e.g., halides (including Cl, Br, I), OH or mixtures thereof), (ii) C6 to C 12 aryl, which is optionally substituted with other functional groups (e.g., halide, OH or mixtures thereof), or (iii) organic groups having 4 to 20 carbon atoms bonded to each other via one or more ether, thioether, ester, thioester, thiocarbonyl, amide, carbamate, carbonyl and / or sulfonyl linkers,

[0161] m, n are independently selected from 0, 1, 2, 3, 4, 5 or 6, provided that n+m is greater than 0, that is, at least one A group is present.

[0162] Such polymerizable materials include mono-, di- or poly-acrylates and methacrylates, such as methyl acrylate, methyl methacrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-hexyl (meth)acrylate, stearyl (meth)acrylate, allyl (meth)acrylate, glyceryl di(meth)acrylate, diurethane dimethacrylate known as UDMA (a mixture of isomers, e.g. Plex 6661-0) (which is the reaction product of 2-hydroxyethyl methacrylate (HEMA) and 2,2,4-trimethylhexamethylene diisocyanate (TMDI)), glycerol tri(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-propylene glycol diacrylate, 1,3-propylene glycol dimethacrylate, trimethylolpropane tri(meth)acrylate, 1,2,4-butanetriol tri(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate , pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, sorbitol hexa(meth)acrylate, bis[1-(2-(meth)acryloyloxy)]-p-ethoxyphenyl dimethylmethane, bis[1-(3-methacryloyloxy-2-hydroxy)]-p-propoxyphenyl dimethylmethane (BisGMA), bis[1-(3-acryloyloxy-2-hydroxy)]-p-propoxy-phenyl dimethylmethane and tris(hydroxyethyl) isocyanurate trimethacrylate; diacrylates and dimethacrylates of polyethylene glycol having a molecular weight of 200-500, acrylated monomers (see, for example, US 4,652,274) and acrylated oligomers (see, for example, US 4,642,126); and vinyl compounds such as styrene, diallyl phthalate, divinyl succinate, divinyl adipate and divinyl phthalate; polyfunctional (meth)acrylates containing urethane, urea or amide groups. If desired, mixtures of two or more of these free radical polymerizable materials can be used.

[0163] Other polymerizable components that may be present include di(meth)acrylates of ethoxylated bisphenol A, such as 2,2'-bis(4-(meth)acryloyloxytetraethoxyphenyl)propane, urethane (meth)acrylates and (meth)acrylamides. In addition, the monomers used may be esters of [α]-cyanoacrylic acid, crotonic acid, cinnamic acid and sorbic acid.

[0164] It is also possible to use methacrylates mentioned in EP 0 235 826 such as bis[3[4]-methacryloyl-oxymethyl-8(9)-tricyclo[5.2.1.0 2,6 Also suitable are 2,2-bis-4 (3-methacryloyloxy-2-hydroxypropoxy) phenylpropane (bis-GMA), 2,2-bis-4 (3-methacryloyloxypropoxy) phenylpropane, 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-dioxydimethacrylate (UDMA), urethane (meth)acrylate and bishydroxymethyl tricyclo-(5.2.1.0 2,6)decane di(meth)acrylate.

[0165] These ethylenically unsaturated monomers can be used alone or in combination with other ethylenically unsaturated monomers in dental compositions. In addition to those components, other hardenable components that can be added include oligomeric or polymeric compounds such as polyester (meth) acrylates, polyether (meth) acrylates, polycarbonate (meth) acrylates, and polyurethane (meth) acrylates. The molecular weight of these compounds is generally less than 20,000 g / mol, specifically less than 15,000 g / mol, and especially less than 10,000 g / mol.

[0166] The polymerizable component without an acidic moiety is typically present in the following amounts: lower limit: at least 5 wt%, or at least 10 wt%, or at least 20 wt%; upper limit: maximum 65 wt%, or maximum 55 wt%, or maximum 45 wt%; range: 5 wt% to 65 wt%, or 10 wt% to 55 wt%, or 20 wt% to 45 wt%; the wt% is relative to the weight of the dental composition.

[0167] According to one embodiment, the dental compositions described herein are provided in the form of a kit comprising a catalyst paste and a base paste.

[0168] The catalyst paste comprises a polymerizable component free of acidic moieties, microcapsules comprising the first component of the redox initiator system, and optionally a filler.

[0169] The base paste comprises an acidic component, a second component of the redox initiator system and optionally a filler.

[0170] The catalyst paste and the base paste are separated from each other during storage.

[0171] The first component and the second component of the redox initiator system together form an initiator system suitable for initiating the curing of a curable component present in the catalyst paste or in the base paste or in both the catalyst paste and the base paste.

[0172] According to one embodiment, the first component of the redox initiator system contained in the microcapsules is a reducing agent and the second component of the redox initiator system is an oxidizing agent.

[0173] According to another embodiment, the first component of the redox initiator system contained in the microcapsules is an oxidizing agent and the second component of the redox initiator system is a reducing agent.

[0174] According to one embodiment, the kit comprises two microcapsules, namely microcapsules comprising a reducing agent and microcapsules comprising an oxidizing agent.

[0175] Oxidizing agents and reducing agents include those described above.

[0176] The acidic component included in the base paste is a component adapted to interact with the pH-sensitive component of the microcapsules, causing the structure of the microcapsules to weaken (eg, dissolve), thereby enabling the first component of the redox initiator system to migrate out of the microcapsules.

[0177] The nature and structure of the acidic component are not particularly limited unless the intended purpose cannot be achieved. Inorganic and organic acidic components can be used as desired.

[0178] Usable inorganic acidic components include hydrochloric acid, sulfuric acid, phosphoric acid, mixtures thereof, and acid salts thereof.

[0179] Organic acidic components that can be used include monocarboxylic acids such as formic acid, acetic acid and benzoic acid, and derivatives of these acids; or dicarboxylic acids selected from oxalic acid, malonic acid, succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, sorbic acid, phthalic acid and terephthalic acid, and derivatives of these acids; or tricarboxylic acids selected from trimellitic acid, trimellitic acid, pyromellitic acid, agaric acid, citric acid, 1,2,3-propanediol, and derivatives of these acids; or polycarboxylic acids selected from the group consisting of pyromellitic acid and mellitic acid, and derivatives of these acids; or polycarboxylic acids selected from polyacrylic acid and polymethacrylic acid, and derivatives of these acids; and mixtures thereof.

[0180] The acidic component may be characterized by the following features, alone or in combination:

[0181] a) pK value: equal to or lower than 5, equal to or lower than 4, or equal to or lower than 3.5, or equal to or lower than 3, or equal to or lower than 2;

[0182] b) comprises an acidic moiety selected from sulfonic acid, sulfinic acid, phosphoric acid, phosphonic acid, phosphinic acid or carboxylic acid moieties.

[0183] If desired, the acidic component may also contain one or more polymerizable moieties, such as (meth)acrylate moieties.If desired, one or more polymerizable components containing acidic moieties may be present.

[0184] The polymerizable component containing an acid moiety can generally be represented by the formula:

[0185] A n BC m

[0186] wherein A is an ethylenically unsaturated group, such as a (meth)acryloyl moiety,

[0187] B is a spacer group, such as (i) a linear or branched C1 to C 12 Alkyl, which is optionally substituted with other functional groups (e.g., halides (including Cl, Br, I), OH or mixtures thereof), (ii) C6 to C 12 aryl, which is optionally substituted by other functional groups (e.g., halide, OH or mixtures thereof), (iii) organic groups having 4 to 20 carbon atoms bonded to each other via one or more ether, thioether, ester, thioester, thiocarbonyl, amide, carbamate, carbonyl and / or sulfonyl linkers, and

[0188] C is an acidic group, or a precursor of an acidic group such as an anhydride,

[0189] m and n are independently selected from 1, 2, 3, 4, 5 or 6,

[0190] The acidic group comprises one or more carboxylic acid residues such as -COOH or -CO-O-CO-, phosphoric acid residues such as -OP(O)(OH)OH, phosphonic acid residues such as CP(O)(OH)(OH), sulfonic acid residues such as -SO3H, or sulfinic acid residues such as -SO2H.

[0191] Examples of polymerizable components containing an acid moiety include, but are not limited to, glycerophosphomono(meth)acrylate, glycerophosphodi(meth)acrylate, hydroxyethyl(meth)acrylate (e.g., HEMA) phosphate, bis((meth)acryloyloxyethyl)phosphate, (meth)acryloyloxypropyl phosphate, bis((meth)acryloyloxypropyl)phosphate, bis((meth)acryloyloxy)propoxy phosphate, (meth)acryloyloxyhexyl phosphate, bis((meth)acryloyloxyhexyl)phosphate, (meth)acryloyloxyoctyl phosphate, bis((meth)acryloyloxyethyl)phosphate, (meth)acryloyloxyoctyl) phosphate, (meth)acryloyloxydecyl phosphate, bis((meth)acryloyloxydecyl) phosphate, caprolactone methacrylate phosphate, citric acid di- or tri-methacrylate, poly(meth)acrylated oligomeric maleic acid, poly(meth)acrylated polymaleic acid, poly(meth)acrylated poly(meth)acrylic acid, poly(meth)acrylated polycarboxy-polyphosphonic acid, poly(meth)acrylated polychlorophosphoric acid, poly(meth)acrylated polysulfonic acid, poly(meth)acrylated polyboric acid, etc. Derivatives of these having an acid moiety that can readily react with, for example, water to form the above-mentioned specific examples of hardenable components such as acid halides or acid anhydrides are also contemplated.

[0192] Monomers, oligomers and polymers of unsaturated carboxylic acids such as (meth)acrylic acid, aromatic (meth)acrylated acids (eg, methacrylated trimellitic acid) and their anhydrides may also be used.

[0193] If present, the acidic component is typically present in the following amounts: lower limit: at least 2 wt%, or at least 3 wt%, or at least 4 wt%; upper limit: maximum 50 wt%, or maximum 40 wt%, or maximum 30 wt%; range: 2 wt% to 50 wt%, or 3 wt% to 40 wt%, or 4 wt% to 30 wt%; the wt% are relative to the weight of the dental composition obtained with the catalyst paste and the base paste of the combination kit.

[0194] The dental composition or its corresponding kit and the catalyst paste and / or base paste may contain other components including fillers, photoinitiators, and additives including fluoride release agents, stabilizers, colorants, dyes, pigments, and other additives.

[0195] The amount and type of each ingredient in the composition, both before and after polymerization, should be adjusted to provide the desired physical and handling properties.

[0196] The dental composition or the corresponding paste of the kit may contain one or more fillers.

[0197] The nature and structure of the filler are not particularly limited unless the intended purpose cannot be achieved.

[0198] The addition of fillers can be beneficial, for example, to adjust rheological properties such as viscosity. The amount of filler also generally affects the physical properties of the composition after hardening, such as hardness or flexural strength.

[0199] The size of the filler particles should be such that a homogeneous mixture with the hardenable components forming the resin matrix can be obtained.

[0200] The average particle size of the filler may be in the range of 5 nm to 100 μm.

[0201] If desired, particle size measurement of the filler particles can be performed using a TEM (transmission electron microscopy) method, whereby a population is analyzed to obtain an average particle size.

[0202] The preferred method for measuring particle size can be described as follows: A sample about 80 nm thick is placed on a 200 mesh copper grid with a carbon stabilized polyvinyl acetate substrate (SPI Supplies-a division of Structure Probe, Inc., West Chester, PA). TMTransmission electron micrographs (TEM) were taken at 200 Kv using a 200CX (produced by JEOL, Ltd., Akishima, Japan, and sold by JEOL USA, Inc., USA). The size of a population of about 50-100 particles can be measured and the average diameter determined.

[0203] Fillers generally include non-acid reactive fillers. Non-acid reactive fillers are fillers that do not react with acids to form acid / base reactions.

[0204] Useful non-acid-reactive fillers include fumed silica, fillers based on non-acid-reactive fluoroaluminosilicate glass, quartz, ground glass, water-insoluble fluorides such as CaF2, silica gels such as silicic acid (especially fumed silicic acid and particles thereof), cristobalite, calcium silicate, zirconium silicate, zeolites (including molecular sieves).

[0205] Suitable fumed silicas include, for example, products sold under the following trade names: Aerosil TM Series OX-50, -130, -150 and -200; Aerosil from Evonik TM R8200, -R805; CAB-O-SIL purchased from Cabot Corp, Tuscola TM M5; and HDK types from Wacker, such as HDK TM -H2000, HDK TM H15, HDK TM H18, HDK TM H20 and HDK TM H30.

[0206] Fillers that can also be used and provide radiopacity to the dental materials described herein include heavy metal oxides and fluorides. As used herein, "radiopacity" describes the ability to distinguish hardened dental materials from tooth structure using standard dental X-ray equipment in a conventional manner. Radiopacity in dental materials is advantageous in certain situations where X-rays are used to diagnose dental conditions. For example, radiopaque materials would allow detection of secondary caries that may have formed in tooth tissue around a filling.

[0207] It may be preferred to have an oxide or fluoride of a heavy metal with an atomic number greater than about 28. The selection of the heavy metal oxide or fluoride should be such that the hardened resin in which it is dispersed is not given an undesirable color or shade. For example, iron and cobalt will be disadvantageous because they give dark colors and colors that contrast with the neutral tooth color of the dental material. More preferably, the heavy metal oxide or fluoride is an oxide or fluoride of a metal with an atomic number greater than 30. Suitable metal oxides are oxides of yttrium, strontium, barium, zirconium, hafnium, niobium, tantalum, tungsten, bismuth, molybdenum, tin, zinc, lanthanides (i.e. elements with an atomic number in the range of 57 to 71 (including end values)), cerium, and their combinations. Suitable metal fluorides are, for example, yttrium trifluoride and ytterbium trifluoride. Most preferably, the oxide and fluoride of a heavy metal with an atomic number greater than 30 but less than 72 are optionally included in the material of the present invention. Particularly preferred radiopaque metal oxides include lanthanum oxide, zirconium oxide, yttrium oxide, ytterbium oxide, barium oxide, strontium oxide, cerium oxide, and combinations thereof. The heavy metal oxide particles may be aggregated. If so, it is preferred that the average diameter of the aggregated particles is equal to or less than 200 nm.

[0208] Other suitable fillers for increasing radiopacity are salts of barium and strontium, especially strontium sulfate and barium sulfate.

[0209] Filler(s) that may also be used include nano-sized fillers such as nano-sized silica.

[0210] Suitable nano-sized particles generally have an average particle size in the range of 5 nm to 80 nm.

[0211] Preferred nano-sized silica is commercially available from: NALCO under the product name TM COLLOIDAL SILICAS are available from Nalco Chemical Co. (Naperville, Ill.) (e.g., preferred silica particles can be obtained from Nalco TMProducts 1040, 1042, 1050, 1060, 2327 and 2329 are commercially available); Nissan Chemical America Company, Houston, Texas (e.g., SNOWTEX-ZL, -OL, -O, -N, -C, -20L, -40 and -50); Admatechs Co., Ltd., Japan (e.g., SX009-MIE, SX009-MIF, SC1050-MJM and SC1050-MLV); Grace GmbH & Co. KG, Worms, Germany (e.g., available under the product name LUDOX TM such as those available under the product names LEVASIL TM and Bayer MaterialScience AG, Leverkusen, Germany (e.g., those available under the product name DISPERCOLL TM S (such as those purchased from 5005, 4510, 4020 and 3030).

[0212] Surface treatment of the nano-sized silica particles prior to loading them into the dental material can provide a more stable dispersion in the resin. Preferably, the surface treatment stabilizes the nano-sized particles so that the particles are well dispersed in the hardenable resin and a substantially uniform composition is obtained. In addition, preferably the silica can be modified with a surface treatment agent on at least a portion of its surface so that the stabilized particles can copolymerize, or react with the hardenable resin during curing.

[0213] Thus, silica particles, as well as other suitable non-acid reactive fillers, may be treated with a surface treatment agent that is compatible with the resin.

[0214] If present, the filler is typically present in the following amounts: lower limit: at least 1 wt%, or at least 5 wt%, or at least 10 wt%; upper limit: maximum 80 wt%, or maximum 70 wt%, or maximum 60 wt%; range: 1 wt% to 80 wt%, or 5 wt% to 70 wt%, or 10 wt% to 60 wt%; the weight % is relative to the weight of the dental composition obtained in the case of the catalyst paste and the base paste of the combination kit.

[0215] The dental composition or the corresponding paste of the kit may also comprise a photoinitiator.

[0216] The photoinitiator may be present in the base paste or the catalyst paste or in both pastes. Typically, the photoinitiator is present in the catalyst paste.

[0217] The nature and structure of the photoinitiator are not particularly limited unless the intended purpose cannot be achieved. Photoinitiators suitable for free radical polymerization are well known to those skilled in the art of processing dental materials.

[0218] As the photoinitiator, preferred are those which can polymerize the polymerizable monomer by the action of visible light within a wavelength range of 350 nm to 500 nm.

[0219] Suitable photoinitiators typically contain an alpha diketo moiety, an anthraquinone moiety, a thioxanthone moiety, or a benzoin moiety.

[0220] Examples of photoinitiators include camphorquinone, 1-phenylpropane-1,2-dione, benzil, diacetyl, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl di(2-methoxyethyl) ketal, 4,4,'-dimethylbenzyl dimethyl ketal, anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 1,2-benzoquininone, 1-hydroxyanthraquinone, 1-methylanthraquinone, 2-ethylanthraquinone, 1-bromoanthraquinone, thioxanthone, 2-isopropylthioxanthone, 2-nitrothioxanthone, and the like. Thioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chloro-7-trifluoromethylthioxanthone, thioxanthone-10,10-dioxide, thioxanthone-10-oxide, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, bis(4-dimethyl-aminophenyl)ketone, 4,4,'-bisdiethylaminobenzophenone.

[0221] It has been found that the use of acylphosphine oxides is also useful.

[0222] Suitable acylphosphine oxides can be characterized by the following formula:

[0223] (R 9 )2—P(=O)—C(=O)—R 10

[0224] Each R 9 R may be a hydrocarbon group such as alkyl, cycloalkyl, aryl and aralkyl, any of which may be substituted by a halogen, alkyl or alkoxy group, or both R 9 The groups may be joined to form a ring together with the phosphorus atom, and wherein R 10 is a hydrocarbon group, a five-membered or six-membered heterocyclic group containing S-, O- or N-, or -ZC(=O)-P(=O)-(R 9 )2 group, wherein Z represents a divalent hydrocarbon group such as an alkylene group or a phenylene group having 2 to 6 carbon atoms.

[0225] Suitable systems are also described, for example, in US 4,737,593 (Ellrich et al.), the contents of which are incorporated herein by reference.

[0226] Preferred acylphosphine oxides are those in which R 9 and R 10 The groups are phenyl or phenyl substituted by lower alkyl or lower alkoxy. "Lower alkyl" and "lower alkoxy" mean such groups having 1 to 4 carbon atoms. In particular, it has been found that 2,4,6-trimethylbenzoyldiphenylphosphine oxide is useful (Lucirin TM TPO, BASF).

[0227] Suitable bisacylphosphine oxides can also be described by the following formula:

[0228]

[0229] Where n is 1 or 2, and R 4 , R 5 , R 6 and R 7 H, C 1-4 Alkyl, C 1-4 Alkoxy, F, Cl or Br; R 2 and R 3 the same or different, representing a cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenyl group, replaced by F, Cl, Br, I, C1-4 alkyl and / or C 1-4 an alkoxy-substituted cyclopentyl, cyclohexyl, phenyl, naphthyl or biphenyl group, or a 5- or 6-membered heterocyclic ring containing S or N; or R 2 and R 3 The carbon atoms are joined to form a carbonyl group containing 4 to 10 carbon atoms and optionally 1 to 6 C 1-4 The ring is substituted with an alkyl group.

[0230] More specific examples include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-ethoxyphenyl-phosphine oxide, bis-(2,6-dichlorobenzoyl)-4-biphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2-naphthylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, Bis-(2,6-dichlorobenzoyl)-4-chlorophenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,4-dimethoxyphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)decylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-octylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-2,5-dimethylphenylphosphine oxide Phosphine, bis-(2,6-dichloro-3,4,5-trimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichloro-3,4,5-trimethoxybenzoyl)-4-ethoxyphenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-2,5-dimethylphenyl-phosphine oxide, bis-(2-methyl-1-naphthoyl)phenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-4-biphenylphosphine oxide, bis-(2-methyl-1-naphthoyl)-4-ethoxyphenylphosphine oxide , bis-(2-methyl-1-naphthoyl)-2-naphthyl phosphine oxide, bis-(2-methyl-1-naphthoyl)-4-propylphenyl phosphine oxide, bis-(2-methyl-1-naphthoyl)-2,5-dimethyl phosphine oxide, bis-(2-methoxy-1-naphthoyl)-4-ethoxyphenyl-phosphine oxide, bis-(2-methoxy-1-naphthoyl)-4-biphenyl phosphine oxide, bis-(2-methoxy-1-naphthoyl)-2-naphthyl phosphine oxide and bis-(2-chloro-1-naphthoyl)-2,5-dimethylphenyl phosphine oxide.

[0231] Acylphosphine oxides are sometimes preferred: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (formerly known as IRGACURE TM 819, Ciba Specialty Chemicals).

[0232] If present, the photoinitiator is typically present in the following amounts: lower limit: at least 0.1 wt%, or at least 0.2 wt%, or at least 0.3 wt%; upper limit: at most 10 wt%, or at most 8 wt%, or at most 6 wt%; range: 0.1 wt% to 10 wt%, or 0.2 wt% to 8 wt%, or 0.3 wt% to 6 wt%; the wt% are relative to the weight of the dental composition obtained with the catalyst paste and the base paste of the combination kit.

[0233] Examples of dyes or pigments that may be used include titanium dioxide or zinc sulfide (barium white), red iron oxide 3395, Bayferrox TM 920Z Yellow, Neazopon TM Blue 807 (a copper phthalocyanine based dye) or Helio TM Fast Yellow ER. These additives can be used for individual coloring of dental compositions.

[0234] Examples of photobleachable colorants that may be present include Rose Bengal, Methylene Violet, Methylene Blue, Fluorescein, Eosin Yellow, Eosin Y, Ethyl Eosin, Eosin Blue, Eosin B, Erythrosin B, Erythrosin Yellow blends, Toluidine Blue, 4',5'-Dibromofluorescein and blends thereof. Other examples of photobleachable colorants may be found in US 6,444,725.

[0235] Examples of fluoride release agents that may be present include naturally occurring or synthetic fluoride minerals. These fluoride sources may optionally be treated with a surface treatment agent.

[0236] Other additives that may be added include stabilizers, especially free radical scavengers, for example substituted and / or unsubstituted hydroxyaromatic compounds such as butylated hydroxytoluene (BHT), hydroquinone, hydroquinone monomethyl ether (MEHQ), 3,5-di-tert-butyl-4-hydroxyanisole (2,6-di-tert-butyl-4-ethoxyphenol), 2,6-di-tert-butyl-4-(dimethylamino)-methylphenol or 2,5-di-tert-butyl-hydroquinone or 2- (2'-Hydroxy-5'-methylphenyl)-2H-benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)-2H-benzotriazole, 2-hydroxy-4-methoxybenzophenone (UV-9), 2-(2'-hydroxy-4',6'-di-tert-pentylphenyl)-2H-benzotriazole, 2-hydroxy-4-n-octyloxybenzophenone, 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole and phenothiazine.

[0237] Other additives that may be added include retarders (such as 1,2-diphenylethylene), plasticizers (including polyethylene glycol derivatives, polypropylene glycol, low molecular weight polyesters, dibutyl phthalate, dioctyl phthalate, dinonyl phthalate, diphenyl phthalate, di(isononyl adipate), tricresyl phosphate, paraffin oil, triacetin, bisphenol A diacetate, ethoxylated bisphenol A diacetate and silicone oil) and fragrances.

[0238] The presence of these adjuvants or additives is not essential, so they may be completely absent. However, if present, they are generally present in amounts that are not harmful for the intended purpose.

[0239] If present, the additive is typically present in the following amounts: lower limit: at least 0.01 wt%, or at least 0.05 wt%, or at least 0.1 wt%; upper limit: maximum 15 wt%, or maximum 10 wt%, or maximum 5 wt%; range: 0.01 wt% to 15 wt%, or 0.05 wt% to 10 wt%, or 0.1 wt% to 5 wt%, the wt% being relative to the weight of the dental composition obtained with the catalyst paste and the base paste of the combination kit.

[0240] The dental compositions described herein may comprise, consist essentially of, or consist of the following amounts of the respective components:

[0241] Polymerizable components without acidic moieties: 5 to 65 wt %,

[0242] Polymerizable component with acidic moiety: 2 wt% to 50 wt%,

[0243] Filler: 1 wt% to 80 wt%,

[0244] Microcapsules comprising the first component of the redox initiator system: 0.05% to 10% by weight,

[0245] Second component of the redox initiator system: 0.01 wt % to 5 wt %,

[0246] Additives: 0 wt% to 10 wt%,

[0247] The weight % is relative to the dental composition.

[0248] In another embodiment, the dental composition can comprise, consist essentially of, or consist of the following amounts of the respective components:

[0249] Polymerizable components without acidic moieties: 20 wt % to 65 wt %,

[0250] Polymerizable component with acidic moiety: 2 wt% to 20 wt%,

[0251] Filler: 30% to 70% by weight,

[0252] Microcapsules comprising the first component of the redox initiator system: 0.1% to 5% by weight,

[0253] Second component of the redox initiator system: 0.01 wt % to 5 wt %,

[0254] Additives: 0 wt% to 10 wt%,

[0255] The weight % is relative to the dental composition.

[0256] To avoid undesired reactions, acidic and basic components should not be stored together during storage, especially with microcapsules containing pH-sensitive components.

[0257] The microcapsules should also not be stored with water. Thus, if the dental composition is provided in the form of a kit comprising a catalyst and a base paste, the paste comprising the microcapsules should be substantially free of water.

[0258] Furthermore, in order to reduce the risk of conflicting reactions, it may be advantageous if the dental composition is substantially free or free of additional pH-sensitive or acid-reactive materials such as calcium carbonate fillers.

[0259] The dental compositions described herein are generally prepared by combining or mixing the respective components (ie, the polymerizable component and microcapsules described herein) with other optional components, such as fillers or additives.

[0260] Mixing also includes kneading. If necessary, a high-speed mixer can be used. Depending on the components to be mixed, the mixing is carried out under light-proof conditions.

[0261] The dental compositions described herein are typically stored in packaging means.

[0262] If the dental composition is provided in the form of a kit comprising a catalyst paste and a base paste, the pastes may be contained in separate sealable containers (eg, made of plastic or glass).

[0263] For use, the physician may take a sufficient portion of the composition from the container and manually mix the portion on a mixing plate.

[0264] According to a preferred embodiment, the catalyst paste and the base paste are contained in separate compartments of the storage device.

[0265] The storage device usually comprises two compartments for storing the individual parts, each compartment being equipped with a nozzle for delivering the individual parts.Once divided into enough parts for delivery, the parts can be mixed manually on a mixing plate.

[0266] According to another preferred embodiment, the storage device has an interface for receiving a static mixing head. The mixing head is used for mixing the corresponding paste. Static mixing heads are commercially available, for example, from Sulzer Mixpac company.

[0267] Suitable storage devices include cartridges, syringes, and tubes.

[0268] The storage device generally comprises two housings or compartments having a front end with a nozzle and a rear end and at least one piston movable in the housings or compartments.

[0269] Useful cartridges are described, for example, in US 2007 / 0090079 A1 (Keller) or US 5,918,772 (Keller et al.), the disclosures of which are incorporated by reference. Some of the usable cartridges are commercially available, for example, from Sulzer Mixpac AG (Switzerland). Useful static mixing heads are described, for example, in US 2006 / 0187752 A1 (Keller) or US 5,944,419 (Streiff), the disclosures of which are incorporated by reference. Useful mixing heads are also commercially available from Sulzer Mixpac AG (Switzerland).

[0270] Other suitable storage devices are described, for example, in WO 2010 / 123800 (3M), WO 2005 / 016783 (3M), WO 2007 / 104037 (3M), WO 2009 / 061884 (3M), in particular the device shown in FIG. 14 of WO 2009 / 061884 (3M) or WO 2015 / 073246 (3M), in particular the device shown in FIG. 1 of WO 2015 / 07346. These storage devices have the shape of a syringe. The contents of these references are also incorporated herein by reference.

[0271] Alternatively, but less preferably, the pastes / paste compositions described herein may be provided in two separate syringes and the individual pastes may be mixed manually prior to use.

[0272] Therefore, the present invention also relates to a device for storing the kit box described herein, which comprises two compartments, namely compartment A and compartment B, compartment A contains a catalyst paste and compartment B contains a base paste, the catalyst paste and the base paste are as described herein, and compartment A and compartment B both include a nozzle or an interface for receiving an inlet orifice of a static mixing head.

[0273] The mixing ratio of the base paste and the catalyst base paste is generally 3:1 to 1:3, preferably 2:1 to 1:2, and more preferably 1:1, relative to the volume.

[0274] The microcapsules described herein are particularly useful for producing curable compositions comprising a curable component and a redox initiator system.

[0275] According to one embodiment, the curable composition is a dental or orthodontic composition.

[0276] According to one embodiment, the curable composition is a dental or orthodontic cement, adhesive or filling material.

[0277] The microcapsules described herein are particularly useful for producing a curable composition obtained by mixing two pastes, a base paste and a catalyst paste, wherein one of these pastes comprises the microcapsules described herein and the other paste comprises an acidic component.

[0278] When the two pastes are mixed, the paste containing the acidic component comes into contact with the microcapsules. Upon contact, the microcapsules are weakened. This enables the components of the redox initiator system to be released more easily from the microcapsules.

[0279] Since self-adhesive dental materials usually contain an acidic paste, the acidity of the paste can serve as a trigger to weaken the microcapsules.

[0280] The present invention also relates to a method of curing the curable dental composition.

[0281] This method comprises the steps of providing a catalyst paste comprising the microcapsules described herein and a base paste comprising an acidic or basic component.

[0282] The microcapsules comprise the first component of the redox initiator system as the component to be released.

[0283] The catalyst paste, or the base paste, or both the catalyst paste and the base paste comprises a curable component and a second component of a redox initiator system.

[0284] The first component and the second component of the redox initiator system forming the initiator system are capable of initiating curing of the curable component.

[0285] The catalyst paste and base paste are mixed.

[0286] The acidic component contained in the base paste dissolves or weakens the microcapsules, thereby causing the release of the redox initiator component contained therein.

[0287] If in contact with each other, the redox initiator components initiate cure of the curable components of the curable composition.

[0288] The present invention also relates to a dental composition as described herein for use in a method of restoring a tooth in the mouth of a patient, the method comprising the steps of:

[0289] providing a dental composition in the form of a kit comprising a base paste and a catalyst paste as described herein,

[0290] mixing the base paste and the catalyst paste,

[0291] Apply the mixture to the prepared surface of the tooth to be restored.

[0292] More suitable implementations are described below:

[0293] According to one embodiment, the kit is characterized by:

[0294] The catalyst paste comprises

[0295] The microcapsules described herein contain a reducing component, preferably an ascorbic acid component,

[0296] one or more curable non-acidic (meth)acrylate components,

[0297] one or more fillers,

[0298] The base paste comprises

[0299] one or more acidic components, preferably polymerizable components comprising an acidic moiety,

[0300] one or more curable (meth)acrylate components,

[0301] one or more fillers,

[0302] Oxidizing components,

[0303] The reducing component and the oxidizing agent form a redox initiator system for curing the one or more curable (meth)acrylate components.

[0304] According to another embodiment, the kit is characterized as follows:

[0305] The catalyst paste comprises

[0306] The microcapsules described herein, the microcapsules comprising an oxidizing component, preferably a component containing a peroxide moiety,

[0307] one or more curable non-acidic (meth)acrylate components,

[0308] one or more fillers,

[0309] The base paste comprises

[0310] one or more acidic components, preferably polymerizable components comprising an acidic moiety,

[0311] one or more curable (meth)acrylate components,

[0312] one or more fillers,

[0313] Reducing components,

[0314] The reducing component and the oxidizing agent form a redox initiator system for curing the one or more curable (meth)acrylate components.

[0315] The present invention also relates to a kit comprising the dental composition described herein and any of the following components, alone or in combination:

[0316] Dental milling blocks for machining dental restorations,

[0317] Dental adhesives.

[0318] Suitable dental milling blocks typically comprise a porous zirconium oxide material containing yttria as a phase stabilizing component and a coloring component. Examples of dental milling blocks are described in US 2017 / 020639 (Jahns et al.), US 2015 / 238291A1 (Hauptmann et al.).

[0319] Suitable dental adhesives are acidic dental compositions with relatively low viscosity (e.g., 0.01 Pa*s to 3 Pa*s at 23°C). Dental adhesives interact directly with the enamel or dentin surface of the teeth. Dental adhesives are typically one-component compositions that are radiation-curable and contain an ethylenically unsaturated component having an acidic portion, an ethylenically unsaturated component not having an acidic portion, water, a sensitizer, a reducing agent, and additives. Examples of dental adhesives are described in US 2020 / 0069532 A1 (Thalacker et al.) and US 2017 / 0065495 A1 (Eckert et al.), US 2019 / 231494 A1 (Dittmann et al.),

[0320] Thus, the kit includes components or assemblies that can be used together in the process of restoring a missing tooth.

[0321] The dental milling block is used for machining a dental restoration, the dental adhesive is used for treating a tooth surface to be restored, and the dental composition described herein is used for bonding a dental restoration machined by the dental milling block.

[0322] All disclosures of the patents, patent documents and publications cited herein are incorporated by reference in their entirety, as if each file were cited separately. Various modifications and changes of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The above description, examples and data provide a description of the preparation, use and inventive method of the composition of the present invention. The present invention is not limited to the embodiments disclosed herein. Those skilled in the art will appreciate that many alternative embodiments of the present invention can be made without departing from the spirit and scope of the present invention.

[0323] The following examples are intended to further illustrate the present invention.

[0324] Example

[0325] Unless otherwise specified, all parts and percentages are based on weight, all water is deionized water, and all molecular weights are weight average molecular weight. In addition, unless otherwise specified, all experiments were performed under ambient conditions (23° C.; 1013 mbar).

[0326] method

[0327] Scanning electron microscopy (SEM)

[0328] If desired, the particle size and shape of the microcapsules can be further analyzed and determined by SEM, for example using the apparatus JSM 5400 (Hitachi).

[0329] Light Scattering

[0330] If desired, the particle size distribution can be determined by light scattering, for example using a Horiba (Horiba, JP) device. The light scattering particle size classifier illuminates the sample with a laser and analyzes the intensity fluctuations of the light scattered by the particles at an angle of 173 degrees. The instrument can calculate the particle size using the photon correlation spectroscopy (PCS) method. PCS measures the Brownian motion of particles in a liquid using fluctuating light intensity. The particle size is then calculated as the diameter of a sphere moving at the measured speed. The intensity of the light scattered by the particles is proportional to the sixth power of the particle size. The Z-average particle size or cumulative average is the average value calculated from the intensity distribution, which is based on the assumption that the particles are monomodal, monodisperse and spherical. The correlation function calculated from the fluctuating light intensity is the intensity distribution and its average value. The average value of the intensity distribution is calculated based on the assumption that the particles are spherical. Both the Z-average particle size and the intensity distribution average are more sensitive to larger particles than to smaller particles.

[0331] The volume distribution gives the percentage of the total volume of particles that corresponds to particles in a given size range. The volume average size is the particle size corresponding to the average volume distribution. Since the volume of a particle is proportional to the cube of the diameter, this distribution is less sensitive to larger particles than the Z average particle size. Therefore, the value of the volume average particle size is usually less than the Z average particle size. Within the scope of this document, the Z average particle size is referred to as the "average particle size".

[0332] pH :

[0333] If desired, the pH value can be measured as follows: 1.0 g of a component (e.g. filler) is dispersed in 10 ml of deionized water and stirred for about 5 minutes. A calibrated pH electrode is immersed in the suspension and the pH value is measured during stirring.

[0334] Elemental composition

[0335] If desired, the elemental composition can be determined by X-ray fluorescence spectroscopy (XRF), for example using a ZSX Primus II from Rigaku, Japan. This method is particularly suitable for analyzing solids, such as zirconia ceramics or glass materials.

[0336] Mechanical stability

[0337] If desired, the mechanical stability of the microcapsules can be determined as follows: Fill the microcapsules to be analyzed with Sudan Blue II (a dye with a blue color). Then prepare a paste using, for example, the following composition: 18 wt% TEGDMA, 20 wt% UDMA, 52.02 wt% glass filler, 8.0 wt% fumed silica, 0.1 wt% IC 819, 0.46 wt% coated filled microcapsules. Mix the microcapsules by using a commercially available high-speed mixer (e.g., SpeedMixer TM DAC 150SP; Hauschild, Germany), the composition was mixed using the following conditions: 3 x 90 s at 2500 RPM and 3 x 20 s at 3500 RPM, cooling to room temperature after each mixing step.

[0338] Photocurable trays were prepared from the composition by filling 700 mg of the paste into a cylindrical mold (15 mm diameter; 1.5 mm height) which was placed between glass slides covered with a transparent film. TM The sandwich structure was illuminated from both sides by an S10 light curing device (3M Oral Care) for 20 s (without light guide).

[0339] The sample was then removed from the mold and placed in a Visio TM The samples were completely light cured in a Beta Vario light oven (3M Oral Care) for 7 minutes.

[0340] Then, the L*a*b* color coordinates were determined. If the b* value is positive, then the blue Sudan Blue II was apparently not released from the microcapsules during the paste and disc preparation. This indicates that the tested microcapsules are mechanically stable. If the b* value is negative, then the blue Sudan Blue II was apparently released from the microcapsules during the paste and disc preparation. This indicates that the tested microcapsules are mechanically unstable.

[0341] Water Solubility

[0342] If desired, the water solubility of a substance can be determined by adding 0.1 g of the component to be tested to 100 g of water (23° C.) and stirring the composition for 10 minutes. If the component is completely dissolved, the water solubility is at least 0.1 g / 100 ml of water.

[0343] Determination of working and setting times

[0344] A Physica MCR 301 rheometer (Anton Paar, Graz, Austria) with a plate / plate geometry of 8 mm diameter was used at a temperature of 28° C. 100 mg of paste AX was mixed manually with 100 mg of paste B1 (mixing ratio 1.0:1.0 w / w) on a mixing pad with the aid of a spatula for 20 seconds. The mixture was then applied between the plates and the gap was set to 0.75 mm. The frequency was 1.25 Hz and the oscillation had a deflection of 1.75%.

[0345] The working time (Ta) is defined as the time between the start of mixing and the time when the intersection of G' and G" is reached. The setting time (Tf) is defined as the time between the start of mixing and the time when the mixed paste reaches a shear stress of 100,000 Pa.

[0346] Material

[0347] Table 1

[0348]

[0349]

[0350] Method for coating ascorbyl palmitate particles :

[0351] To 200 g of distilled water, add: 10 g of sodium bicarbonate (or potassium bicarbonate, ammonium bicarbonate or any other monovalent cation bicarbonate), 20 g of sodium carbonate (or potassium carbonate, ammonium carbonate or any other monovalent cation bicarbonate), 200 mg of SURF, 10 g of ASP.

[0352] The blending was performed using a high shear rotary mixer (IKA T50 Ultra Turrax TM) The mixture was mixed for 3 minutes. The mixed mixture was kept at 20°C for 15 minutes. The mixture was then centrifuged at 4,000 RPM for 3 minutes. The supernatant was discarded and the precipitated portion was transferred to 50 g of 28% calcium acetate aqueous solution. The mixture was then mixed for about 3 minutes (mixing device: IKA T50 Ultra Turrax). The blended dispersion was then left to stand at room temperature (20°C) for about 15 minutes. It was then centrifuged at 4,000 rpm for 3 minutes. The supernatant was discarded. The precipitated portion was resuspended in distilled water and filtered. The resulting solid was air-dried and then vacuum-dried.

[0353] Composition

[0354] All pastes AX were prepared by weighing the corresponding compounds.

[0355] By using the commercially available SpeedMixer TM DAC 150SP (Hauschild, Germany) was used to mix the composition of the paste given in Table 2 by applying 3 x 90 s at 2500 RPM and 3 x 20 s at 3500 RPM (cooling to room temperature after each mixing step).

[0356] Table 2

[0357]

[0358]

[0359] Paste B1 was prepared by weighing the corresponding compounds given in Table 3. Then, a commercially available SpeedMixer TM The mixture was mixed using a DAC 150SP (Hauschild, Germany) by applying 3 x 90 s at 2500 RPM and 2 x 60 s at 3500 RPM (cooling to room temperature after each mixing step).

[0360] Table 3

[0361]

[0362] Different kits (Examples 1-12) were provided as shown in Table 4. Pastes A1 and A2 were stored at room temperature (23°C), 36°C or 50°C for the listed storage times. Paste B1 was stored at room temperature (23°C).

[0363] Table 4

[0364]

[0365]

[0366] The working and setting times of the compositions of Examples 1-12 were determined according to the storage times and temperatures as described above. The results are given in Table 5.

[0367] Table 5

[0368]

[0369] The compositions obtained after mixing pastes A1 and A2 with paste B1 showed very similar working and setting times within the desired range (Examples 1 and 7).

[0370] Paste A1 containing the water-insoluble components of the redox initiator system showed reduced working and setting times after 4 weeks at 50° C. (Example 6), indicating some degradation of the components of the redox initiator system.

[0371] Paste A2 containing the water-insoluble components of the encapsulated redox initiator system showed only slightly reduced working and setting times even after 6 weeks at 50° C. (Example 12).

[0372] Thus, the use of microcapsules as described herein are not only stable enough to survive the mixing process, but also help increase the shelf life stability of the redox initiator component in the paste.

[0373] Furthermore, it was found that the working time and setting time of curable compositions comprising a redox initiator component encapsulated in microcapsules comprising a crosslinked polymeric material may vary over a wider range, which may lead to a less predictable curing behavior.

[0374] Compared to the microcapsules described in, for example, US 2020 / 368117 A1 (Claussen et al.), the microcapsules described herein allow for a higher loading of the first component of the redox initiator system. If desired, the loading capacity can be increased by up to about 5 times, or 4 times, or 3 times the weight. Thus, in order to provide a dental composition with the same amount of redox initiator system, a smaller amount of microcapsules is required.

Claims

1. A dental composition, comprising: a polymerizable component that does not contain an acidic moiety, and A microcapsule comprising: a water-insoluble first component of a redox initiator system, and pH sensitive inorganic components, The microcapsules do not contain polymeric materials, The pH-sensitive inorganic component forms a shell around a core comprising the water-insoluble first component, The pH-sensitive inorganic component comprises anions and multivalent cations, The anions are selected from carbonate, bicarbonate, phosphate, nitrate and sulfate, and the polyvalent cations are selected from ions of Mg, Ca, Sr, Ba, Al or Zn, The polymerizable component is a component that can be cured or hardened by heating, or by radiation-induced polymerization or crosslinking, or by the use of redox initiators or by any other free radical forming method, The pH sensitive inorganic component is capable of generating a gas when in contact with an acidic component.

2. The dental composition of claim 1, wherein the pH sensitive component is selected from carbonates and bicarbonates of multivalent cations.

3. The dental composition of claim 1 or 2, wherein the water-insoluble first component of the redox initiator system is a reducing agent.

4. The dental composition of claim 1 or 2, wherein the weight ratio of the pH-sensitive inorganic component of the microcapsules to the water-insoluble first component of the redox initiator system is in the range of 20:1 to 1:

1. 5 . The dental composition according to claim 1 , wherein the microcapsule has a diameter of 1 μm to 200 μm.

6. The dental composition according to claim 1 or 2, provided as a kit comprising a catalyst paste and a base paste, The catalyst paste comprises: A polymerizable component containing no acidic moiety, said microcapsules comprising a water-insoluble first component of a redox initiator system, Optional fillers, The base paste comprises: an acidic component, a polymerizable component comprising an acidic moiety, The second component of the redox initiator system, Optional filler.

7. The dental composition according to claim 1 or 2, provided as a kit comprising a catalyst paste and a base paste, The catalyst paste comprises: A polymerizable component containing no acidic moiety, filler, microcapsules comprising a pH-sensitive component and a water-insoluble first component of a redox initiator system, The pH sensitive component comprises a salt of a multivalent cation and a carbonate or bicarbonate anion, The water-insoluble first component of the redox initiator system is a water-insoluble ascorbic acid component, The microcapsules have a diameter ranging from 1 μm to 100 μm, The base paste comprises: a polymerizable component comprising an acidic moiety, filler, The second component of the redox initiator system, the second component of the redox initiator system is selected from an oxidizing component and a transition metal component.

8. The dental composition of claim 6, wherein the acidic component is characterized by the following features alone or in combination: pK value: less than 5; Contains an acidic moiety selected from a sulfonic acid, sulfinic acid, phosphoric acid, phosphonic acid, phosphinic acid or carboxylic acid moiety.

9. The dental composition of claim 7, wherein the acidic component is characterized by the following features alone or in combination: pK value: less than 5; Contains an acidic moiety selected from a sulfonic acid, sulfinic acid, phosphoric acid, phosphonic acid, phosphinic acid or carboxylic acid moiety.

10. The dental composition according to claim 1 or 2, which is a self-adhesive dental cement composition.

11. Use of the microcapsules according to any one of claims 1 to 9 for the preparation of a dental composition comprising a polymerizable component containing an acidic moiety.

12. A method of curing a dental composition according to any one of claims 6 to 9, comprising the steps of combining the base paste and the catalyst paste, wherein the acidic component contacts the microcapsules comprising the first component of the redox initiator system and reacts with the pH-sensitive inorganic component of the microcapsules, and The pH-sensitive inorganic component of the microcapsules is dissolved and the water-insoluble first component of the redox initiator system is released.

13. A device for storing a dental composition according to any one of claims 6 to 9, the device comprising two compartments, compartment A and compartment B, compartment A containing the catalyst paste and compartment B containing the base paste, the catalyst paste and the base paste being according to the preceding claims, compartment A and compartment B each comprising a nozzle or an interface for receiving an inlet orifice of a static mixing head.

14. A kit comprising a dental composition according to any one of claims 1 to 10 and the following components, alone or in combination: a dental milling block for machining dental restorations; a dental adhesive.

15. Use of a dental composition according to any one of claims 1 to 10 for the preparation of a kit for restoring a tooth in the mouth of a patient.

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