Water-setting dental cement, its manufacturing method, its manufacturing kit and its use

Abstract

A water-setting dental cement with improved fracture toughness is provided. The present invention provides a water-curable dental cement comprising an acid-reactive powder, a polyprotonic acid, water, and dispersed polymer particles. The present invention also provides a method for producing the water-curable dental cement, a kit for producing the water-curable dental cement, and uses of the water-curable dental cement.

Description

[Technical Field]

[0001] The present invention relates to a water-setting dental cement, a method for producing the water-setting dental cement, a kit for producing the water-setting dental cement, and its use as a dental filling and / or luting material. [Background technology]

[0002] From a chemical point of view, a water-setting dental cement is a powder-liquid mixture that solidifies via an acid-base reaction. To this end, the dental cement contains at least three components: an acid-reactive powder as a base, an acid, and water.

[0003] Conventional glass ionomer cement (CGIC) is a hydraulic cement that essentially contains three components: an acid-reactive glass powder, a polyalkenoic acid, and water. The powder, for example, contains an acid-reactive fluoroaluminosilicate glass. The liquid contains water. The acid, typically a water-soluble polyalkenoic acid, may be present in either the powder or the liquid.

[0004] An example of a conventional glass ionomer cement for fillings (for type III and type V caries, root caries, tunnel formations, caries in primary teeth and underfilling) known in the prior art is sold under the name Alpha®Fil (DMG). Further known products are GC Fuji IX® and Ketac®Fil.

[0005] Critical stress intensity factor K Ic is a measure of the fracture toughness of a material. A problem with known cements is that they have insufficient fracture toughness. The present invention aims to solve this problem.

[0006] The prior art has attempted to improve the fracture toughness of water-containing dental cements by adding polymerizable components, particularly monomers, polymers, and / or fillers containing (meth)acrylate groups. However, such polymerizable cements suffer from drawbacks compared to conventional glass ionomer cements, such as reduced biocompatibility.

[0007] JP 2001-354509 A describes a powder mixture for glass ionomer cement containing fibers based on apatite or fluoroapatite, which have improved mechanical properties, especially fracture toughness. The fibers provide anisotropic reinforcement. However, a drawback of the fibers used is that they can produce undesirable rough surfaces.

[0008] U.S. Patent No. 6,860,932 describes improvements in fracture toughness with TiO or AlO particles. The metal oxides described have a high refractive index and therefore increase the opacity of the glass ionomer cement, making it more difficult to stain like teeth.

[0009] WO2017083039 discloses a kit for manufacturing glass ionomer cement, which includes alumina or silica-based particles as one component. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a water-setting dental cement having improved fracture toughness without simultaneously sacrificing other advantageous properties. [Means for solving the problem]

[0011] This object is achieved by a water-setting dental cement according to the independent claims.The invention relates inter alia to a water-setting dental cement comprising an acid-reactive powder, a polyprotonic acid, water and dispersed polymer particles.

[0012] Further advantageous embodiments can be found in the dependent claims.

[0013] First, some terms used in the context of the present invention will be explained.

[0014] Critical stress intensity factor K Ic is a measure of the fracture toughness of a material. The stress intensity factor K is a measure of the strength of the stress field in the vicinity of the crack tip. The stress intensity factor at which fracture finally occurs is the critical stress intensity factor. This material performance is also called fracture toughness. Critical stress intensity factor K Ic is considered to be the fracture toughness when the crack opens perpendicular to the crack surface. This crack opening regime is the most important in practice.

[0015] "Acid-reactive powder" is understood in the context of the present invention to mean a powder that reacts with a polyprotic acid via an acid-base reaction. Suitable acid-reactive powders are known in the prior art and are described in more detail below.

[0016] "Polyprotic acid" is understood in the prior art and in the context of the present invention to mean an acid having multiple protons, the release of which occurs stepwise over multiple dissociation steps. Polyprotic acids suitable for the present invention are described in more detail below.

[0017] The essence of the present invention is to provide a hydraulic dental cement, preferably a conventional glass ionomer cement, in which polymer particles are dispersed, so that the propagation of cracks that lead to fracture in the cement is prevented. In this way, the fracture toughness of the hydraulic cement is improved in a simple manner without deteriorating other performances. The fracture toughness or critical stress intensity factor K of the hydraulic cement is Ic The increase in the resistance of the filling also leads to an increase in its durability, which makes it possible to extend the application of the filling, in particular for chewing loads.

[0018] Therefore, in the context of the present invention, it is desirable to improve the fracture toughness or critical stress intensity factor K while retaining or improving other advantageous performance properties of water-setting dental cements. Ic Other performance characteristics of water-setting dental cements, especially conventional glass ionomer cements, that should be considered are consistency / moldability, working time, setting time (1.5-6 minutes), compressive strength (>100, >180 MPa), flexural strength (>25 MPa), abrasion / acid erosion (<0.17 mm), optical performance (opacity C0.70 of CGIC 0.35-0.90), radiographic visibility (%Al), color and color stability, self-adhesion / moisture resistance, biocompatibility / sensitivity, fluoride release, and expansion behavior. The minimum requirements specified for conventional glass ionomer cements are taken from ISO 9917.

[0019] A further advantage of the present invention is that the polymer particles of the present invention are toxicologically harmless and occupy only a very low weight percentage in the cement. The main components in the selected dental cement can also be commercially available, clinically approved cement components. The addition of polymerizable compounds, such as (meth)acrylates, among others, can also be omitted.

[0020] In the context of the present invention, the water-setting dental cement is preferably a glass ionomer cement, more preferably a conventional glass ionomer cement (CGIC).

[0021] Conventional glass ionomer cements are known in the prior art; they harden via an acid-base reaction. In addition to conventional glass ionomer cements, there are also so-called metal-reinforced or cermet cements (e.g., Ketac® Silver and Alpha® Silver) and plastic-modified glass ionomer cements (e.g., Photac® Fil Quick, Vitremer® Fuji® II LC). One advantage of conventional glass ionomer cements is, for example, their good chemical adhesion to hard tooth tissue.

[0022] [Polymer particles] Suitable polymer particles form a polymer dispersion in water or in an aqueous phase.

[0023] The polymer particles preferably have on their surface ionic groups and / or groups which sterically stabilise them in the aqueous phase.

[0024] Ionic groups are understood here to mean all electrostatic stabilizing groups, especially anionic and cationic groups.

[0025] Here, sterically stabilizing groups are understood to mean polymeric or oligomeric chain moieties that are at least partially soluble in water. They stabilize dispersed particles due to entropic effects, according to the mechanism of steric stabilization in aqueous media against flocculation and coagulation (T.S. Stadros, Interfacial Phenomena and Colloid Stability, Vol. 1, Fundamentals, De Gruyter, 2015, pp. 209 ff.). Suitable polymer chains that are generally preferred as polymeric or oligomeric chain moieties are described in more detail in the description of the individual polymer particles.

[0026] The ionically and / or sterically stabilising groups are preferably primarily covalently attached to the polymer of the particle.

[0027] The polymer particles are preferably spherical.

[0028] The polymer particles are preferably prepared in the form of a primary and / or secondary dispersion.

[0029] In addition, the average particle size of the polymer particles is preferably less than about 1 μm, more preferably between 5 nm and 500 nm, and even more preferably between 5 nm and 100 nm. The particle size can be determined by dynamic light scattering (e.g., Malvern Zeta-Sizer Nano-zs) performed on an aqueous dispersion of the polymer particles. Generally speaking, the polymer particles are already present after production as an aqueous dispersion, which is processed for light scattering measurements by methods known to those skilled in the art. If the polymer particles are present as a dry solid, e.g., a powder, they are converted into an aqueous dispersion using, for example, stirring, dispersing, and / or ultrasonic devices (e.g., ultrasonic homogenizers such as Bandelin Sonopuls 4200) prior to light scattering measurements.

[0030] It is further preferred that the polymer particles are present as a water-containing dispersion for the preparation of the water-setting dental cement, ie prior to the setting of the water-setting cement.

[0031] The dispersed polymer particles of the present invention are characterized, inter alia, by forming a stable dispersed phase with water as the dispersing medium, where "stable" means that the dispersed polymer particles remain substantially dispersed in water as the dispersing medium and do not form precipitates and / or agglomerate and / or aggregate for at least 1 hour, preferably over the commercial shelf life, preferably at least 6 months.

[0032] Additionally, the proportion of dispersed polymer particles in the dental cement is preferably at least 0.005 wt. %, more preferably at least 0.01 wt. %, based on the overall composition of the dental cement before hardening.

[0033] The proportion of dispersed polymer particles in the dental cement, based on the overall composition of the dental cement before hardening, is more preferably at most 10% by weight, even more preferably at most 3% by weight, even more preferably at most 1% by weight, even more preferably at most 0.5% by weight, and most preferably at most 0.3% by weight.

[0034] Additionally, the proportion of dispersed polymer particles in the dental cement, based on the overall composition of the dental cement before hardening, is more preferably 0.005% by weight to 5% by weight, more preferably 0.005% by weight to 3% by weight, even more preferably 0.01% by weight to 1% by weight, even more preferably 0.01% by weight to 0.5% by weight, and most preferably 0.01% by weight to 0.3% by weight.

[0035] Preferred polymer particles are those prepared by emulsion polymerization.

[0036] Preferred polymer particles contain polymer chains formed by optionally substituted homopolymer chains (see H.G. Elias, Macromolecules, Vol. 1, Chemische Struktur und Synthesen, 6th edition, Wiley VCH).

[0037] Preferred base polymers for the particles are homopolymer polyacrylates, poly(alkyl)acrylates such as polymethacrylates, polyisoprene, polybutadiene, polystyrene, polyvinyl acetate, polyacrylonitrile, and polyacrylamide. Particularly preferred base polymers are copolymers polymerized from the above-mentioned homopolymer monomers and / or additional monomers. For example, it is particularly preferred to form poly(meth)acrylate particles from two or more acrylate or methacrylate monomers. Further preferred copolymers for use in the polymer particles of the present invention are styrene-acrylate copolymers, styrene-maleic acid derivative copolymers, styrene-butadiene copolymers, vinyl acetate-ethylene copolymers, vinyl acetate-vinyl alcohol copolymers, vinyl acetate-acrylate copolymers, and acrylonitrile-butadiene copolymers.

[0038] It is advantageous to use a small amount of an acidic monomer such as acrylic acid, maleic acid, or a salt thereof in the base polymer. It is advantageous to use a small amount of a basic monomer such as N,N-dimethylaminoethyl methacrylate or a salt thereof in the base polymer of the particles. The proportion of the acidic monomer or a salt thereof or the basic monomer or a salt thereof is preferably less than 10% by weight, particularly preferably less than 5% by weight.

[0039] The homochain particle dispersions of the polymers of the present invention can be particularly advantageously prepared by a free-radical emulsion polymerization process, in which the monomers are polymerized in an aqueous phase with a water-soluble free-radical initiator, optionally with the addition of a surfactant.

[0040] Another preferred method for obtaining ionically stabilized particle dispersions with charged centers covalently bonded to the particle surface is the so-called emulsifier-free emulsion polymerization (M. Egen, Functional Three-Dimensional Photonic Crystals Made from Polymer Lattices, Dissertation, Johannes Gutenberg University, Mainz, 2003). This alternative emulsion polymerization method uses ionic free-radical initiators such as potassium peroxodisulfate, which introduce ionic groups into the growing polymer chains during the initiation reaction. In this way, electrostatically stabilized polymer particles with covalently bonded ionic groups are produced without the use of surfactants.

[0041] A more preferred process for producing polymer particles with covalently attached stabilizing groups uses polymerizable surfactants (so-called surfmers), which first copolymerize with the monomers in a free-radical reaction and then stabilize the dispersion through surfactant properties (M. Summers and J. Easto, Advances in Colloid and Interface Science, 100-102, (2003), 137-152). The use of surfmers allows for the production of sterically and electrostatically stabilized dispersions.

[0042] In certain embodiments, the homochain-based polymer particles may be crosslinked, where the crosslinked structure is formed as a separate process by copolymerizing a monomer having a copolymerizable group with a monomer having multiple copolymerizable groups during emulsion polymerization.

[0043] Further suitable polymer particles for use in the dental materials of the present invention can be prepared by miniemulsion polymerization, a process in which suitable particles can be produced by both a free radical mechanism and polyaddition (K. Landfester, F. Tiarks, H.-P. Hentze, M. Antonietti, Macromol. Chem. Phys. 201, (2000) 1-5; K. Landfester, Macromol. Rapid Commun. 22, (2001) 896).

[0044] Preferred polymer particles contain polymer chains that may have substituted heterochains. Such polymer particles preferably comprise a polysiloxane elastomer, preferably a particle core, with slight to substantial crosslinking. Preference is given to polydialkyl, polyalkylaryl, or polydiaryl siloxane elastomers. The steric or electrostatic stabilizing groups are preferably attached to the surface of the polysiloxane elastomer particles via Si-C bonds.

[0045] In some embodiments, the stabilizing group is a poly(meth)acrylic acid copolymer chain. These may be produced, for example, by copolymerization of a (meth)acrylic acid-containing monomer mixture with polysiloxane particles surface-modified with methacrylic acid groups. For this process, a comonomer can be selected appropriately. If, for example, it is intended to increase the negative charge in the copolymer shell, this can be achieved by copolymerization with 0.1%-20% by weight, particularly preferably 0.2%-5% by weight (based on (meth)acrylic acid) of a polymerizable medium- or strong acid or its salt. Polymerizable sulfonic acids or their salts are suitable for this purpose. (Meth)acrylamidopropyl sulfonic acid derivatives or their salts are particularly suitable for this purpose. Similarly, polymerizable acidic phosphate or phosphonate esters found in the prior art can also be used as comonomers.

[0046] In one alternative, suitable polymer particles can be prepared from polysiloxane particles having a poly(meth)acrylate shell by hydrolysis of the poly(meth)acrylate shell, for example as commercially available under the name Genioperl P52 (Wacker Chemie, Germany).

[0047] Preferred polymer particles are core-shell particles, in which the inner part of the particle differs from the outer part in terms of the material and potentially in terms of other properties, such as modulus of elasticity. The term "shell" in this context is not understood to mean a layer of sterically or electrostatically stabilizing groups. Preferred core-shell particles may have a relatively soft core and a relatively hard shell. In another embodiment, they comprise a relatively hard core and a relatively soft shell. Core-shell particles preferably comprise essentially homopolymer chains. Core-shell particles are preferably produced via a two-stage emulsion polymerization process. Preferred core-shell particles may be PU particles. In a preferred embodiment, the core-shell particles have a polyurethane core and a shell composed of polymer chains formed by optionally substituted homopolymer chains.

[0048] Preferred polymer particles are polyurethane particles (PU particles).

[0049] Preference is given to these PU particles produced from: a) at least one polyisocyanate; b) optionally at least one compound which is mono- or difunctional with respect to the reaction of isocyanates, in particular a polyol A, c) at least one further compound which is mono- or difunctional with respect to the isocyanate reaction and which further comprises at least one ionic group and / or at least one functional group which can be converted into an ionic group and / or at least one sterically stabilizing group, and d) optionally at least one further compound which is mono-, di- or polyfunctional with respect to the isocyanate reaction and which is selected from the group of polyols B, chain extenders and crosslinkers, Here, at least one of the two components b) or d) must be present.

[0050] Preference is given to these PU particles produced from: a) at least one polyisocyanate; b) at least one polyol A, c) at least one further compound which is mono- or difunctional with respect to the isocyanate reaction and which further comprises at least one ionic group and / or at least one functional group which can be converted into an ionic group and / or at least one sterically stabilizing group, and d) Optionally, at least one polyol B and / or one chain extender and / or one crosslinker.

[0051] Mono- or difunctional compounds in an isocyanate reaction are compounds containing groups capable of reacting with isocyanates. These are preferably functional groups containing active hydrogen, such as OH, NH, NH, NHNH, SH, etc. Such groups are known to those skilled in the art and are described, for example, in "The Polyurethanes Book," edited by D. Randall and S. Lee, John Wiley & Sons, Ltd., 2002. Those skilled in the art will select the compound according to the desired performance.

[0052] Suitable polyisocyanates have at least two isocyanate groups. Preferably, the at least one polyisocyanate has exactly two isocyanate groups. However, it is also preferred that the at least one polyisocyanate is a high-functionality polyisocyanate, preferably having two or more isocyanate groups. The at least one polyisocyanate is preferably an aromatic or aliphatic compound, in particular an acyclic or cyclic compound. It is particularly preferred when the at least one polyisocyanate is an aliphatic compound, more preferably an alicyclic compound. The at least one polyisocyanate is preferably modified or unmodified. Suitable modified polyisocyanates include, for example, those containing carbodiimide groups, allophanate groups, isocyanurate groups, urethane groups, and / or biuret groups. It is also preferred to use a combination of modified and unmodified polyisocyanates.

[0053] Examples of preferred polyisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1,4-diisocyanatocyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-diisocyanatodicyclohexylmethane, 1,4-phenylene diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, m-xylene diisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate. Particularly preferred polyisocyanates are selected from aliphatic and cycloaliphatic polyisocyanates.

[0054] Polyol A preferably has hydroxy groups and at least one further hydroxy or amino group.

[0055] In a further embodiment, polyol A has two or more amino groups, preferably in the terminal position, such as, for example, the Jeffamine® polyetheramine type α,ω-diaminopolyethers sold by Huntsman.

[0056] The polyol A preferably has a molecular weight of 500 to 6000 g / mol, more preferably 500 to 2000 g / mol. Suitable polyols A are preferably linear or branched. Examples of suitable polyols A include polyether polyols, polyester polyols, polyesteramide polyols, polycarbonate polyols, polyolefin polyols, polysiloxane polyols, and poly(meth)acrylate polyols, more preferably those further having hydroxyl groups at their respective ends. Polyether polyols are particularly preferred. Polytetrahydrofuran 1000 is most preferred.

[0057] Polyether polyols are preferably the reaction products of the polymerization of cyclic organic oxides, such as ethylene oxide, propylene oxide, and tetrahydrofuran, with polyfunctional initiators, such as water, ethylene glycol, propylene glycol, diethylene glycol, cyclohexanedimethanol, glycerol, trimethylolpropane, and pentaerythritol. Mixtures of cyclic organic oxides can also be used. Polymerization of various cyclic organic oxides can be effected simultaneously to form random copolymers, which can be added sequentially to form block copolymers.

[0058] The polyester polyol is preferably obtained by reacting at least a dihydric alcohol with at least a dihydric carboxylic acid. These carboxylic acids may be aliphatic, alicyclic, heterocyclic, araliphatic, or aromatic. In addition to the free carboxylic acid, the corresponding carboxylic acid anhydride or the methyl or ethyl ester of the corresponding carboxylic acid can also be used. Mixtures of different polycarboxylic acids and their derivatives can also be reacted with mixtures of different polyhydric alcohols. Examples of suitable carboxylic acids, carboxylic acid anhydrides, and carboxylic acid esters are succinic acid, succinic anhydride, dimethyl succinate, adipic acid, dimethyl adipate, glutaric acid, dimethyl glutarate, cyclohexane-1,4-dicarboxylic acid, maleic acid, maleic anhydride, fumaric acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic acid, hexahydrophthalic acid, and dimethyl terephthalate. Examples of suitable alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propane-1,2-diol, propane-1,3-diol, dipropylene glycol, butane-1,3-diol, butane-1,4-diol, neopentyl glycol, hexane-1,6-diol, 1,4-bis(hydroxymethyl)cyclohexane, trimethylolpropane, glycerol, and pentaerythritol. Polyester polyols can also be prepared by the polymerization of lactones. Examples of suitable lactones include β-propiolactone, γ-butyrolactone, and ε-caprolactone.

[0059] Suitable polyesteramides are prepared like polyesters, with part of the polyhydric alcohol being replaced by an aminoalcohol, such as ethanolamine, or a diamine, such as ethylenediamine.

[0060] Suitable polycarbonate polyols can be obtained by reacting diols such as propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, and diethylene glycol with carbonates such as diphenyl carbonate and dimethyl carbonate, or with phosgene.

[0061] An example of a suitable polyolefin polyol is hydroxy-terminated polybutadiene, which is sold by Nippon Soda Co., Ltd. under the name "NISSO-PB G Series."

[0062] An example of a suitable polysiloxane polyol is polydimethylsiloxane terminated with hydroxyalkyl groups, preferably hydroxybutyl or hydroxypropyl groups.

[0063] Examples of suitable poly(meth)acrylate polyols are copolymers of (meth)acrylic acid esters with at least one compound having at least one hydroxy group and at least one (meth)acrylate group. Preference is given to copolymers of (meth)acrylic acid esters with one hydroxy group and at least one compound having only one (meth)acrylate group.

[0064] Furthermore, it is preferred that the at least one ionic group of the at least one further compound that is mono- or difunctional with respect to the isocyanate reaction is an anionic or cationic group.

[0065] The anionic groups are preferably carboxylate, sulfonate, sulfate, sulfonium, phosphate, or phosphonate groups. The cationic groups are preferably ammonium or phosphonium groups. Ionic groups and / or functional groups convertible to ionic groups can be incorporated into both the PU backbone and the lateral PU backbone.

[0066] The sterically stabilizing groups are at least partially water-soluble polymeric or oligomeric chain moieties, preferably covalently bonded to the polyurethane particles. They stabilize the particles due to entropic effects, according to the mechanism of steric stabilization in aqueous media against flocculation and coagulation (T. S. Stadros, Interfacial Phenomena and Colloidal Stability, Vol. 1, Fundamentals, De Gruyter, 2015, pp. 209ff.). Examples of suitable polymer chains include water-soluble polymer chains such as poly(oxyethylene), poly(oxazoline), water-soluble poly(2-alkyloxazoline), water-soluble poly(ethyleneimine) derivatives, poly(N-vinylpyrrolidone), water-soluble poly((meth)acrylates) such as poly(hydroxyethyl(meth)acrylate) and poly(meth)acrylamide), water-soluble polysaccharides such as starch, pectin, and cellulose, and cellulose ethers such as methylcellulose or hydroxyethylcellulose, proteins such as gelatin, and partially hydrolyzed polyvinyl acetate or polyvinyl alcohol.

[0067] In a preferred embodiment, the polymer chains do not have any groups that are charged in water between pH 1 and 9.

[0068] In a further embodiment, the polymer chains carry additional groups that have a charge between pH 1 and 9. These may be positive or negative charge carriers. Suitable chemical groups are those described as ionic groups.

[0069] In certain embodiments, the sterically stabilizing group that also carries a charge is a poly(meth)acrylic acid chain or a poly(meth)acrylic acid copolymer chain.

[0070] Suitable relative molecular weights of the sterically stabilising polymer chains are between 200 and 100,000, preferably between 300 and 20,000, particularly preferably between 400 and 4,000.

[0071] In certain embodiments, the sterically stabilizing groups are in each case polymer chains that are covalently attached to the particles by chain segments. The chain segments can be located at the ends of the chains or at other positions on the chains. The linking chain segments are preferably located at the ends of the chains.

[0072] In a further preferred embodiment, the further at least one ionic and / or sterically stabilising group of the at least one further compound which is mono- or difunctional with respect to the isocyanate reaction is a sterically stabilising chain.

[0073] The sterically stabilizing chains can be attached to the particles by a variety of means: In a preferred embodiment, the chains are attached to the particles via urethane or urea groups.

[0074] Typical sterically stabilizing groups tethered to the particles via chain segments are, for example, monofunctionally terminated methoxypoly(oxyethylenes) introduced during particle synthesis in the form of α-methoxy, ω-hydroxypoly(oxyethylenes) or α-methoxy, ω-aminopoly(oxyethylenes), or poly(methyloxazolines) introduced during particle synthesis in the form of monohydroxy- or amino-functionalized poly(methyloxazolines), for example. They may also be attached to the sides of polyurethane chains.

[0075] In a further embodiment, the sterically stabilizing group is a polymer chain covalently bonded to the particle via two or more chain segments. Preference is given to polymer chains that are bonded to the particle via two chain segments. In a preferred embodiment, the bond segment is located at the end of the chain. Here, the sterically stabilizing polymer chain is preferably introduced during particle synthesis in the form of polyol A or polyol B. In a preferred embodiment, the chain is attached to the particle via a urethane or urea group.

[0076] A typical example of a sterically stabilizing group attached to the particle via two chain segments is poly(oxyethylene), introduced during the particle synthesis, for example in the form of polyethylene glycol (polyol A or B) or other α,ω-diaminopoly(oxyethylene). Another example is a hydroxy or amino telechelic poly(methyloxazoline) or poly(ethyloxazoline).

[0077] The at least one further compound which is mono- or difunctional with respect to the isocyanate reaction is particularly preferably hydroquinone monosulfonic acid potassium salt, N-methyldiethanolamine, PEG 350, PEG 600, TEGOMER® D3403 or Ymer® N120.

[0078] The at least one polyol B is preferably a polyol B having at least two hydroxy groups. The at least one polyol B preferably has a molecular weight of less than 500 g / mol. Suitable polyols B may be preferably aromatic, in particular carbocyclic or heterocyclic, or aliphatic, in particular linear, branched, or cyclic. Polyol B is particularly preferably aliphatic. Polyol B is preferably an at least dihydric alcohol. Examples of suitable polyols B are ethylene glycol, diethylene glycol, triethylene glycol, propane-1,2-diol, propane-1,3-diol, dipropylene glycol, butane-1,3-diol, butane-1,4-diol, neopentyl glycol, hexane-1,6-diol, 1,4-bis(hydroxymethyl)cyclohexane, trimethylolpropane, glycerol, and pentaerythritol.

[0079] The chain extender is preferably a diamine having a molecular weight of less than 500 g / mol. Preferred diamines are α,ω-alkylenediamines such as ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,6-hexamethylenediamine, or other high molecular weight primary and secondary diamines, particularly preferably ethylenediamine. Further preferred embodiments of the diamine are diamines having additional heteroatoms, especially oxygen atoms, in the organic residue (between the amino groups).

[0080] The cross-linking agent is preferably one having at least three functional groups, such as diethylenetriamine.

[0081] The production of such polyurethane particles is described inter alia below:

[0082] Robin et al., Polym. Int., vol. 61, pp. 495-510, 2012. Ramesh et al., J. Macromol. Sci. C, Vol. 38, pp. 481-509, 1998 Long et al., Macromol. Chem. Phys., Vol. 215, pp. 2161-2174, 2014, and Kim, Colloid Polym. Sci., Vol. 274, pp. 599-611, 1996.

[0083] The PU particles of the present invention have, as linking sites, b), c) and / or d), depending in each case on the selected components, urethane, urea, allophanate and / or biuret groups. All or only some of these groups may be present. It is preferred to use PU particles that contain only urethane groups as linking sites from the polyaddition process. For reasons of hydrolytic stability, it is also preferred to use PU particles that contain exclusively or at least mainly urea groups as linking sites from the polyaddition process.

[0084] The polymer particles preferably do not have any polymerizable groups, and in particular do not have any (alkyl)acrylate groups or (alkyl)acrylamide groups.

[0085] [Acid-reactive powder] Suitable acid-reactive powders are known to those skilled in the art and are preferably selected from metal oxides, metal hydroxides, mineral trioxide aggregates (MTAs), hydroxyapatites, bioactive glasses, acid-reactive glasses and mixtures thereof.

[0086] The metal oxide is preferably selected from magnesium oxide, calcium oxide, strontium oxide, barium oxide, zinc oxide, lanthanum oxide, yttrium oxide and mixtures thereof.

[0087] The metal hydroxide is preferably selected from magnesium hydroxide, calcium hydroxide, strontium hydroxide, lanthanum hydroxide, yttrium hydroxide and mixtures thereof.

[0088] Mineral trioxide aggregates (MTA) are powders consisting primarily of calcium silicates (dicalcium silicate ((CaO)2·SiO2) and tricalcium silicate ((CaO)3·SiO2), tricalcium aluminate ((CaO)3·Al2O3), and calcium oxide. Further components present may preferably be gypsum (CaSO4·2H2O) and bismuth(III) oxide.

[0089] Bioactive glasses are a group of surface-active glasses with biological activity. In contrast to conventional glasses, they are distinguished by the fact that they are soluble in aqueous media and form a hydroxyapatite layer on their surface. Examples of preferred bioactive glasses are Bioglass 45S5 or Bioglass, as described in WO 2011 / 000866, WO 2011 / 161422 and WO 2014 / 154874.

[0090] The acid-reactive glass used may preferably be an aluminosilicate glass, more preferably a fluoroaluminosilicate glass, even more preferably a calcium fluoroaluminosilicate glass or a strontium fluoroaluminosilicate glass. In addition, glasses containing lanthanides are also preferred. Suitable glasses are, inter alia, those described in, for example, EP 0 885 854, DE 3 804 469 or EP 1 343 452.

[0091] Preferred components of suitable glass powders are SiO, AlO, CaF, AlF, NaF, AlPO, CaO, SrO, SrF, P0, B0, BiO, MgO, TiO, ZrO, GeO, LaO or further oxides of the lanthanide series and ZnO. Suitable combinations are, for example, those described in A.D. Wilson and J.W. Nicholson, "Acid-base cements: their biomedical and industrial applications", Cambridge Press, 1993.

[0092] It is preferred that the surface of the powder has not been treated or modified with an organic compound, and it is even more preferred that it does not contain any polymerizable groups, in particular, neither (alkyl)acrylate groups nor (alkyl)acrylamide groups.

[0093] The acid-reactive powder preferably has an average particle size (d50) of 0.5-30 μm, more preferably 1-20 μm, and / or a maximum particle size (d99) of less than 150 μm, preferably less than 100 μm, more preferably less than 80 μm (e.g., Beckman Coulter Laser Particle Size Analyzer LS13320). The acid-reactive powder preferably comprises a first amount of glass particles having an average particle size of 5-20 μm, more preferably 5-15 μm, and a second amount of glass particles having an average particle size of 1-5 μm, more preferably 2-3 μm. The first and second amounts of glass particles may differ from each other, for example, due to different glass compositions, surface treatments applied, and / or different shapes, e.g., irregular or round.

[0094] The proportion of the acid-reactive powder in the dental cement is preferably 20% by weight to 90% by weight, more preferably 40% by weight to 85% by weight, based on the entire composition of the dental cement before hardening.

[0095] [Polyprotonic acid] Suitable polyprotic acids are known to those skilled in the art, and are preferably selected from polyacids and phosphoric acids, especially polyacids.

[0096] Preferred polyacids are homopolymers and copolymers of unsaturated carboxylic or phosphonic acids. Further preference is given to polyalkenoic acids as polyacids. Particular preference is given to polyacrylic acid (PAA), poly(acrylic acid-co-maleic acid), poly(acrylic acid-co-itaconic acid), poly(acrylic acid-co-vinylphosphonic acid) and poly(vinylphosphonic acid). Further suitable monomers and comonomers for homopolymers and copolymers are described in Schricker et al., J. Mat. Chem. 22, 2824-2833, 2012, such as N-vinylcaprolactam, N-vinylpyrrolidone, amino acid-modified acrylates and acrylamide.

[0097] In a preferred embodiment, the polyprotonic acid does not contain any free-radically polymerizable groups, in particular does not contain any (alkyl)acrylate or (alkyl)acrylamide groups.

[0098] The proportion of polyprotonic acid in the dental cement is preferably 4.9% by weight to 40% by weight, more preferably 7.4% by weight to 25% by weight, based on the total composition of the dental cement before hardening.

[0099] [water] The proportion of water in the dental cement, based on the entire composition of the dental cement before hardening, is preferably 4.9% by weight to 40% by weight, more preferably 7.4% by weight to 25% by weight.

[0100] [Additional Components] In a preferred embodiment, the water-setting dental cement further comprises additional components selected from the group consisting of complexing agents, inorganic and organic fillers, inorganic and organic colorants, and mixtures thereof. Suitable complexing agents include, for example, tartaric acid, citric acid, and / or those described in Prosser et al., J. Dent. Res., Vol. 61, 1982, pp. 1195-1198. Suitable inorganic fillers include, for example, radiopaque, non-acid-reactive (inert) inorganic fillers.

[0101] The present invention further provides a method for preparing a water-setting dental cement by mixing at least an acid-reactive powder, a polyprotonic acid, water, and dispersed polymer particles.

[0102] The method for producing the water-setting dental cement of the present invention can be developed with the additional features described in relation to the water-setting dental cement of the present invention and the kit of the present invention.

[0103] The present invention further provides a kit for making a water-setting dental cement, comprising the following components: a) dispersed polymer particles; b) acid-reactive powders; c) polyprotic acids, and d) water.

[0104] The proportion of dispersed polymer particles in the kit, based on the total composition of the kit before hardening of the dental cement, is preferably at least 0.005% by weight, more preferably at least 0.01% by weight, the weight value relating to the polymer particles themselves and not to the particle dispersion.

[0105] The proportion of dispersed polymer particles in the dental cement, based on the overall composition of the kit before hardening of the dental cement, is preferably at most 10% by weight, more preferably at most 3% by weight, even more preferably at most 1% by weight, even more preferably at most 0.5% by weight, and most preferably at most 0.3% by weight.

[0106] Additionally, the proportion of dispersed polymer particles in the dental cement, based on the overall composition of the kit before the dental cement hardens, is more preferably 0.005% to 5% by weight, more preferably 0.005% to 3% by weight, even more preferably 0.01% to 1% by weight, even more preferably 0.01% to 0.5% by weight, and most preferably 0.01% to 0.3% by weight.

[0107] The proportion of the acid-reactive powder in the kit is preferably 20% by weight to 90% by weight, more preferably 40% by weight to 85% by weight, based on the total composition of the kit before hardening of the dental cement.

[0108] The proportion of polyprotonic acid in the kit, based on the total composition of the kit before the dental cement hardens, is preferably 4.9% by weight to 40% by weight, and more preferably 7.4% by weight to 25% by weight.

[0109] The proportion of water in the kit, based on the total composition of the kit before hardening of the dental cement, is preferably 4.9% by weight to 40% by weight, more preferably 7.4% by weight to 25% by weight.

[0110] Kits of the present invention can be developed with further features described in relation to the water-setting dental cements of the present invention, particularly the further and additional components thereof.

[0111] The kit preferably comprises at least two components, and the components of the kit are preferably divided into these components. The components of the kit are preferably present in the first and / or second components depending on the embodiment, unless the component consisting of the acid-reactive powder, the polyprotic acid, and the water is present in only one separate component. In this case, different combinations are associated with different advantages, for example, with regard to storage stability and miscibility. The dispersed polymer particles are preferably present in the first and / or second components depending on the embodiment. In a preferred embodiment, the first component comprises the acid-reactive powder, and the second component comprises water and the dispersed polymer particles. Depending on the embodiment, the polyprotic acid is present in the first and / or second components. The at least two components need to be mixed immediately before use to produce the water-curable dental cement.

[0112] It is even more preferred that the first component of the kit is provided as a powder and the second component is provided as a liquid, or that the first component of the kit is provided as a paste and the second component is provided as a paste.

[0113] The kit also preferably comprises a suitable device for mixing the components. Preferred devices for mixing are, for example, a spatula, a mixing pad and / or a device in which the parts of the kit are present in pre-measured form and / or a device for automatic mixing of the parts.

[0114] The mixing ratio of powder component to liquid component is preferably greater than 1: 1, more preferably greater than 2: 1, and even more preferably greater than 3: 1. This means, for example, mixing 3.5 parts by weight of powder with 1 part by weight of liquid.

[0115] Examples of suitable kit component systems that may be mentioned are the capsules described in EP 1344500 and, for example, the commercially available Mixpac TM Includes cartridge systems for automatic mixing such as L / S systems.

[0116] The present invention further provides the use of the water-setting dental cement of the present invention as a filling, and even more preferably as a masticatory load filling. [Brief explanation of the drawings]

[0117] The invention will now be described using advantageous embodiments with reference to the accompanying drawings, in which:

[0118] [Figure 1] Figure 1: Mean values ​​and standard deviations of fracture toughness (stress intensity factor KIc (unit: MPa√m)) for cements 1 to 3 shown in Table 4.

[0119] [Figure 2] Figure 2: Mean values ​​and standard deviations of compressive strength (units: MPa) for cements 1 and 2 shown in Table 4.

[0120] [Figure 3] Figure 3: Mean values ​​and standard deviations of flexural strength (units: MPa) for cements 1 to 3 shown in Table 4.

[0121] TIFF2026041736000002.tif110164

[0122] Polytetrahydrofuran 1000 was heated at 60°C and 0.03 mbar for 4 hours to obtain dry polytetrahydrofuran (PTHF). The powder was stored under nitrogen.

[0123] Fluoroaluminosilicate glass A (FAS A): Composition 32.2 wt% Si as SiO2 31.6 wt% Al as Al2O3 24.9 wt% Sr as SrO 5.2 wt% P as P2O5 1.7 wt% Na as Na2O F as F- 7.2 wt%

[0124] The glass powder was pulverized in a ball mill to an average particle size d50 of 2.6 μm, and then heat-treated at 500°C for 8 hours.

[0125] Fluoroaluminosilicate glass B (FAS B): Composition SiO2 36.00% by weight Al2O3 22.50% by weight CaF221.00wt% Na3AlF69.00% by weight AlF36.60% by weight AlPO45.00wt%

[0126] The glass powder was ground in a ball mill to an average particle size (d50) of 7.7 μm. 1 kg of the powder was then suspended in a solution of 30 g of KH2PO4 in 3 L of distilled water and stirred at room temperature (RT) for 24 h. The suspension was then filtered, washed with distilled water, and dried at 100 °C for 6 h.

[0127] [method] Average particle size and average zeta potential of ionic polyurethane particles (PU particles):

[0128] The parameters were determined by dynamic light scattering using a Malvern Zeta-Sizer Nano-zs. The average particle size was measured as the mean hydrodynamic equivalent radius in the form of Z-average. The particles were in the form of an aqueous dispersion. The prepared dispersion was diluted 1:10 with ultrapure water. Water was used as the dispersion medium for the measurements of the following parameters: Refractive index 1.33, Dielectric constant 78.5, and Viscosity 0.8873cP.

[0129] The measurements were carried out at 25°C.

[0130] Fluoroaluminosilicate glass particle size:

[0131] The particle size distribution and mean particle size (d50) were determined using a Beckman Coulter Laser Particle Sizer LS130 and a Beckman Coulter Laser Particle Sizer LS13320.

[0132] 250 mg of ground glass was mixed with 4 drops of glycerol on a coarse watch glass to obtain a creamy paste. This paste was pre-dispersed with 1 drop of water using a pestle. The paste was then mixed with 5 ml of water and dispersed in an ultrasonic bath (Bandelin Sonorex RK102H) with ice-water cooling for 5 minutes. This dispersion was introduced into the measurement chamber of a particle size analyzer (Coulter LS130 or Beckman Coulter LS13320) and measured while circulating the aqueous dispersion to be measured.

[0133] Measurements were carried out in tap water. Evaluation was carried out according to the Fraunhofer diffractive optics model.

[0134] Lyophilization: The diluted solution was freeze-dried using a ZIRBUS Technology "Sublimator VaCo 5'" freeze-dryer.

[0135] Flexural strength (FS): The bending strength was measured according to ISO9917‐2:2010 at a feed rate of 0.8 mm / min.

[0136] Compressive strength (CS): Compressive strength was measured according to ISO9917-1:2010 at a feed rate of 1 mm / min.

[0137] Fracture toughness (K Ic ): The powder and liquid were mixed on a pad using a spatula at a specific mixing ratio within 1 minute and then filled into a mold with dimensions of length L = 50 mm, height H = 4 mm, and width W = 3 mm. After 1 hour at 37 °C and a relative humidity of > 95, the specimens were removed from the mold and stored in distilled water at 37 °C for an additional 23 h ± 1 h. The specimens were scored on one side with a 3 mm width using a low-speed saw (Buehler Isomet, Boma diamond cutting disc D46 / 54, thickness 0.20 mm). The depth of the score was approximately 0.7 mm.

[0138] The width and height of the specimen were measured using calipers. The specimen was placed face down on a three-point bending apparatus (ZwickRoell Z2.5) of a universal testing machine (spacing between supports S = 20 mm) so that the notch was located directly under the force transmission wedge. The maximum force to fracture (Fmax) of the specimen was measured at a feed rate of 0.8 mm / min.

[0139] Images of the cross-section of the fractured specimens were recorded using a digital camera (Leica DFC295) under a microscope (Leica Leitz DMRX). The indent depths a1, a2, and a3 were identified in three locations using evaluation software (Leica Application Suite V3). The average value a was formed from the three values ​​according to the formula: The measurements were used to calculate the fracture toughness (stress intensity factor K) according to a specific formula: Ic ) was calculated.

[0140]

number

[0141] [Example 1] Synthesis of PU particles with anionic groups:

[0142] A solution of 10 g of PTHF, 13.9 ml of acetone, 5.25 g of H12MDI, and 0.02 ml of catalyst (dimethyltin dineodecanoate in toluene, 50% by weight) was heated at 60°C for 4 hours (reflux condenser, drying tube) and then cooled to room temperature (RT). The isocyanate group content was determined by titration and was 2.96% by weight.

[0143] Next, 1.65 g of hydroquinone monosulfonic acid potassium salt (DMSO solution, 10 wt % ratio) was added at room temperature (approximately 23°C), and the mixture was heated at 60°C for 4 hours, then at 70°C for 1.5 hours, and cooled to room temperature. The isocyanate group content was 0.43 wt %.

[0144] The mixture was then heated to 50°C and 38.3 ml of deionized water was added dropwise over approximately 35 minutes. A milky white cloudiness developed. The acetone was removed on a rotary evaporator. The remaining dispersion had an average particle size of Z average = 77 nm and an average zeta potential = -31 mV.

[0145] The dispersion was purified by dialysis. For this purpose, a dispersion containing approximately 20% by weight of polyurethane particles was diluted with deionized water. 100 ml of the diluted dispersion was dialyzed against 8 liters of deionized water (dialysis tubing made of regenerated cellulose ("Zellutans", Carl Roth, molecular weight cutoff = 6000-8000)) for 5 days. The water was changed four times during this time. The solids content of the dispersion was determined by freeze-drying and was found to be 0.97% by weight.

[0146] [Example 2] Synthesis of PU particles with cationic groups:

[0147] A solution of 10 g of PTHF, 13.9 ml of acetone, 5.25 g of H12MDI and 0.02 ml of catalyst was heated at 60°C for 4 hours and then cooled to room temperature. The content was 3.25% by weight.

[0148] 0.956 ml of N-methyldiethanolamine was added and the mixture was heated at 60° C. for a further 4 hours and cooled again.

[0149] Next, 1.94 ml of glacial acetic acid and 47 ml of acetone were added, the mixture was heated to 40° C., and then 35 ml of deionized water was added dropwise over approximately 35 minutes. A milky white cloudiness developed.

[0150] The acetone was removed on a rotary evaporator. The remaining clear dispersion had an average particle size of Z average = 35 nm, an average zeta potential of 69 mV, and a solids content of 22.2 wt%.

[0151] [Example 3] Synthesis of PU particles without ionic groups:

[0152] Batch 1: H12MDI 0.04 mol Butane-1,4-diol 0.005 mol Terathane 650 0.005 mol PEG600 0.01 mol DABCO 1 Spatula Tip DBTDL 3 drops S Acetone

[0153] Batch 2: H12MDI 0.2 mol PolyTHF250 0.1 mol PEG350 0.1 mol DABCO 1 Spatula Tip DBTDL 3 drops S THF

[0154] The diisocyanate and two diol components were each dissolved in a specific solvent (S). Additionally, 1,4-diazabicyclo[2.2.2]octane (DABCO) and dibutyltin dilaurate (DBTDL) were added as catalysts to the reaction solution. The solution was stirred for 24 hours to achieve complete reaction. The resulting prepolymer was added dropwise to an excess of water with vigorous stirring. During this process, particles were immediately formed. The resulting aqueous particle suspension was purified three times by ultrafiltration using water. The residue from the ultrafiltration was redispersed in several milliliters of water each time. The resulting dispersion was gravimetrically analyzed for solids content and subsequently used to prepare a liquid for glass ionomer cement. The size of the resulting particles was determined using a particle size analyzer.

[0155] Batch 1: Solid content in dispersion: 18.6% by weight Particle size: 300nm

[0156] Batch 2: Solid content in dispersion: 16.3% by weight Particle size: 165nm

[0157] [Example 4] Manufacturing of the kit components:

[0158] Powder: 18.2 parts of polyacrylic acid (PAA) and 81.8 parts of FAS B were mixed together.

[0159] liquid: The liquid of the present invention was prepared by mixing deionized water and the dispersion obtained in Example 3.

[0160] Preparation of water-setting dental cement:

[0161] Powder and liquid were mixed in the weight ratios in Tables 1 and 2 to form specimens and determine the fracture toughness. The fracture toughness values ​​K1c and standard deviation (SD) are given.

[0162] [Table 1]

[0163] [Table 2]

[0164] [Example 5] Manufacturing of kit components (powder and liquid)

[0165] Powder: 47.5 parts of FAS A, 31.7 parts of FAS B, and 20.8 parts of PAA were mixed together.

[0166] The liquid was prepared by mixing deionized water, tartaric acid, and the dispersions obtained in Examples 1 and 2. The composition of the liquid is shown in Table 3.

[0167] [Table 3]

[0168] [Example 6] Preparation of water-setting dental cement:

[0169] 2.4 g of powder and 0.38 g of liquid were mixed on the pad using a spatula within 1 minute in each case to form the test specimens. The compressive strength (CS), flexural strength (FS) and fracture toughness (K) of the mounted test specimens were measured. Ic ) was determined as described.

[0170] [Table 4]

[0171] The mass fractions of ionic PU particles in the water-setting dental cement were 0.06 wt% and 0.09 wt%. The addition of small amounts of these polyurethane particles significantly improved the fracture toughness (stress intensity factor K Ic) (see Figure 1), while the addition had no effect on the compressive strength and flexural strength (see Figures 2 and 3).

[0172] Example 7: Synthesis of PMMA particles

[0173] A 250 ml three-neck flask equipped with a precision glass stirrer and two septa was initially charged with 150 ml of ultrapure water. The contents were heated to 90 °C under a nitrogen stream. After 45 min, the nitrogen stream was shut off, and 15 ml (141 mmol) of methyl methacrylate was added through the septa. To initiate the polymerization, the mixture was heated at 90 °C for an additional 30 min, followed by the addition of 5 ml (1.8 mmol) of a 10% aqueous potassium peroxodisulfate solution as an initiator. Additionally, the solution was previously flushed with nitrogen for 10 min at 90 °C. The reaction solution was stirred at 400 rpm using a precision glass stirrer. To monitor the reaction, 0.1 ml of the reaction solution was withdrawn through the septa every 30 min and dried in air on a glass substrate. After the reflection color of the dried film no longer changed, the solution was stirred for an additional 30 min at 90 °C. To terminate the reaction, the septa were removed, and the suspension was stirred in air for an additional 20 min. For purification, the reaction solution was warmed and filtered to remove crude impurities. The filtrate was then centrifuged. Initially, centrifugation was performed at least twice at 4000 rpm for 5-10 minutes to remove the colorless precipitate. The solution was then centrifuged for 30-90 minutes until a clear solution formed above the iridescent precipitate. The liquid phase was decanted, and the precipitate was redispersed in 60 ml of distilled water. This procedure was repeated 3-4 times to completely remove the low-molecular-weight residual polymer. The product was stored as a 5%-20% aqueous suspension. The particle size of the resulting product was determined using a Beckman Coulter particle size analyzer to have an average particle size of 342 nm.

[0174] Example 8: Synthesis of PMMA-co-n-butyl MA particles (80:20)

[0175] The synthesis was carried out similarly to Example 7 - Synthesis of PMMA Particles. However, 12 mL (113 mmol) of methyl methacrylate and 4.5 mL (28 mmol) of n-butyl methacrylate were added. The size of the resulting particles was determined to be an average diameter of 323 nm.

[0176] Example 9: Synthesis of PMMA-co-n-butyl MA particles (60:40)

[0177] The synthesis was carried out in the same manner as in Example 7 - Synthesis of PMMA Particles. However, 9 mL (84.6 mmol) of methyl methacrylate and 9 mL (56 mmol) of n-butyl methacrylate were added. The size of the resulting particles was determined to be an average diameter of 345 nm.

[0178] Example 10: Synthesis of PMMA-co-n-butyl MA particles (40:60)

[0179] The synthesis was carried out in the same manner as in Example 7 - Synthesis of PMMA Particles. However, 6 mL (56 mmol) of methyl methacrylate and 13.6 mL (85 mmol) of n-butyl methacrylate were added. The size of the resulting particles was determined to be an average diameter of 332 nm.

[0180] Example 11: Synthesis of core-shell particles (PnbutylMA-PMMA)

[0181] The synthesis was initially carried out in the same manner as in Example 7 - Synthesis of PMMA Particles. However, 13.6 mL (85 mmol) of undistilled n-butylmethyl methacrylate was added first. After the reflection color of the dried film no longer changed, 6 mL (56 mmol) of methyl methacrylate was added through a septum, and then the reaction was continued again as in Example 7. The size of the resulting particles was determined to be an average diameter of 380 nm.

[0182] [Example 12] Kit Components

[0183] The powder consisted of a homogeneous mixture of fluoroaluminosilicate glass B (FAS B) and polyacrylic acid in a ratio of 4.51:1. The liquid consisted of demineralized water for the reference system or an aqueous particle dispersion for the particle-reinforced glass ionomer cement. The particle dispersions were both prepared by redispersing the appropriate amount of polymer particles in demineralized water. The individual particle contents of the aqueous particle dispersions are shown in Table 5.

[0184] [Example 13] Glass ionomer cement manufacturing

[0185] Glass ionomer cement was mixed from the kit components using a spatula on the pad. The individual mix ratios are shown in Table 5.

[0186] [Table 5]

[0187] When 0.25 wt % to 0.75 wt % of the polymer particles of Examples 7 to 11 were added to the aqueous dispersion, the fracture toughness of the glass ionomer cement (reference) was significantly improved.

Claims

1. A water-setting dental cement comprising an acid-reactive powder, a polyprotonic acid, water and dispersed polymer particles.

2. 2. The water-setting dental cement of claim 1, wherein the water-setting dental cement is a glass ionomer cement, more preferably a conventional glass ionomer cement.

3. 3. The water-setting dental cement according to claim 1, wherein the polymer particles have an average particle size of less than about 1 μm, more preferably 5 to 500 nm, and even more preferably 5 to 100 nm, as determined by dynamic light scattering in an aqueous dispersion (in water).

4. 4. The water-setting dental cement according to claim 1, wherein the polymer particles are dispersed in an aqueous solution before the water-setting cement is hardened.

5. 5. A water-setting dental cement according to any one of claims 1 to 4, characterized in that the proportion of dispersed polymer particles in the cement is 0.005% to 10% by weight, more preferably 0.005% to 3% by weight, even more preferably 0.01% to 1% by weight, even more preferably 0.01% to 0.5% by weight, and most preferably 0.01% to 0.3% by weight, based on the overall composition of the cement before hardening.

6. The water-setting dental cement according to any one of claims 1 to 5, comprising one or more of the following components in the following quantitative proportions based on the overall composition of the cement before hardening: 20% to 90% by weight, preferably 40% to 85% by weight, of an acid-reactive powder; 4.9% to 40% by weight, preferably 7.4% to 25% by weight, of a polyprotonic acid, and / or 4.9% to 40% by weight, preferably 7.4% to 25% by weight, of water.

7. 7. A water-setting dental cement according to any one of claims 1 to 6, characterized in that the acid-reactive powder is selected from metal oxides, metal hydroxides, mineral trioxide aggregates, hydroxyapatites, bioactive glasses, in particular acid-reactive glasses, and mixtures thereof.

8. 8. A water-setting dental cement according to any one of claims 1 to 7, characterized in that the acid-reactive powder is selected from a first amount of glass particles having an average particle size of 5 μm to 20 μm, more preferably 5 μm to 15 μm, and a second amount of glass particles having an average particle size of 1 μm to 5 μm, more preferably 2 μm to 3 μm.

9. 9. A water-setting dental cement according to claim 1, wherein the polyprotonic acid is selected from polyacids and phosphoric acids.

10. 10. The water-setting dental cement according to any one of claims 1 to 9, characterized in that the water-setting dental cement contains further additional components selected from the group consisting of complexing agents, inorganic and organic fillers, inorganic and organic colorants, and mixtures thereof.

11. A method for producing a water-setting dental cement, comprising mixing at least an acid-reactive powder, a polyprotonic acid, water, and dispersed polymer particles.

12. A kit for making a water-setting dental cement comprising the following components: a) dispersed polymer particles; b) an acid-reactive powder; c) a polyprotonic acid, and d) water.

13. The kit according to claim 12, characterized in that it contains one or more of the following components in the following quantitative proportions based on the overall composition of the kit before hardening of the dental cement: 0.005% to 5% by weight, preferably 0.005% to 3% by weight, more preferably 0.01% to 1% by weight, even more preferably 0.01% to 0.5% by weight, and most preferably 0.01% to 0.3% by weight of dispersed polymer particles; 20% to 90% by weight, preferably 40% to 85% by weight, of an acid-reactive powder; 4.9% to 40% by weight, preferably 7.4% to 25% by weight, of a polyprotonic acid, and / or 4.9% to 40% by weight, preferably 7.4% to 25% by weight, of water.

14. 14. A kit according to any one of claims 11 and 13, characterized in that the kit is composed of at least two components, among which the components of the kit are divided.

15. Use of the water-setting dental cement according to any one of claims 1 to 9 as a filling or luting cement.

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