Dental opaquer composition

Abstract

To provide a dental opaquer composition.SOLUTION: The invention relates to a dental opaquer composition which can be used to increase an opacity of zirconium oxide ceramics. In addition, the invention relates to a process for producing a dental restoration, in which the opacity of the zirconium oxide ceramic is increased by using the opaquer composition. The opacifying effect of the composition can be limited to areas of the oxide ceramic near the surface, a desirable aesthetic effect for covering discolored stumps or dark implants can be attained even in thin-walled, highly aesthetic dental restorations.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a dental opacifying agent composition capable of increasing the opacity of dental oxide ceramics, particularly zirconium oxide ceramics.

Background Art

[0002] Zirconium oxide ceramics are widely used in the production of dental restorations due to their advantageous mechanical properties. Zirconium oxide materials based on tetragonal polycrystals stabilized with Y2O3 are particularly used as starting materials for dental restorations.

[0003] As also described in International Publication No. 2018 / 115529A1, the production of dental restorations from zirconium oxide usually includes two hot densification steps separated by a shaping step. In this process, usually, the starting material of zirconium oxide is first cast or mechanically compressed using pressure and then pre-sintered to an intermediate porous state to produce a blank. This blank is suitable for shaping or pre-forming, for example, by machining in a CAD / CAM process. The shaped blank can then undergo final hot densification in a further sintering step.

[0004] Dental restorations not only need to meet high requirements from the perspective of mechanical properties. It is also particularly important to mimic the complex appearance of natural teeth in a lifelike manner. This includes mimicking both translucency and coloring using respective gradients and 3D effects. This is particularly a problem for dental restorations made of zirconium oxide, and therefore, in particular in the anterior tooth region, other materials such as lithium silicate glass ceramics are preferred, although they often have inferior mechanical properties compared to zirconium oxide.

[0005] In dental practice, highly translucent zirconium oxide restorations may be used on dark implants such as titanium skeletons, or on discolored prepared root remnants. Due to the high translucency of the restoration, this can produce undesirable optical effects if the dark or discolored material is visible through the restoration. This problem is particularly relevant in areas where thin-walled zirconium oxide restorations are used, such as the neck region of the restoration.

[0006] Various procedures are known to prevent dark materials from being visible through zirconium oxide restorations.

[0007] For example, an opaque zirconium oxide framework is first fabricated using a complex procedure, then the surface is decorated with glass ceramic, and polished if necessary.

[0008] With the help of dental opacifying agents such as penetrating solutions, it is also possible to reduce or completely prevent the visibility of the material beneath the zirconium oxide ceramic. For this purpose, pre-sintered dental restorations are brought into contact with the penetrating solution by applying the solution to the restoration or by immersing the restoration in the solution. Penetrating solutions typically cause a white discoloration and increased opacity of the dental restoration, preventing darker materials from shining through the zirconium oxide restoration.

[0009] As a general rule, the penetrating solution is applied to the inside, i.e., the lumen, of the dental restoration. Applying the penetrating solution to the outside of the dental restoration is undesirable because it may cause undesirable interactions with the staining solution that has been applied or will be applied there, or it may completely prevent the use of the staining solution.

[0010] International Publication No. 2013 / 170705A1 discloses a coloring solution containing a combination of at least two coloring ions selected from the group consisting of Pr, Er, Ce, and Nd ions, as well as a solvent and additives. When this coloring solution is applied to zirconium oxide ceramics, the light transmittance of the dental restoration increases, i.e., its opacity decreases. Therefore, the coloring solution is not suitable for preventing the dark material from being visible through the dental zirconium oxide restoration.

[0011] European Patent Application Publication No. 3 575 277A1 describes a liquid composition for increasing the opacity of dental zirconium oxide ceramics. The opacifying agent composition contains a water-soluble aluminum or lanthanum compound, water, and an organic solvent. However, it is known, for example from European Patent Application Publication No. 3 575 277A1, that doping with Al or La alters the local sintering properties. Therefore, it is desirable to avoid the use of Al-containing and La-containing opacifying agent compounds in order to ensure low sintering distortion and thus high fit accuracy of the manufactured dental zirconium oxide ceramics.

[0012] International Publication No. 2019 / 146908 discloses a whitening agent composition that, when applied to zirconium oxide dental ceramics, also increases opacity. The whitening agent contains metal oxide nanoparticles and / or metal ion-containing components, as well as stabilizers. However, the use of metal oxide nanoparticles is costly due to the need for multi-step processing, and the use of hydrofluoric acid poses a high health risk to the user.

[0013] International Publication No. 2015 / 148215A1 discloses a phosphorus-containing composition for increasing the opacity of zirconium oxide ceramics. However, it is well known that treating zirconium oxide materials with phosphorus-containing compositions, such as phosphorus-containing acids, is undesirable because it adversely affects bonding to adhesives such as phosphoric acid-containing cement. Therefore, in order to ensure a strong bond between the inner surface of the dental restoration and the root remnant, the application of phosphate-containing compositions to the inner surface of the dental restoration, i.e., its lumen, should be avoided as much as possible. However, it is precisely for this reason that an opacification effect is desirable in order to reduce the visibility of discolored root remnants. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] International Publication No. 2013 / 170705A1 [Patent Document 2] European Patent Application Publication No. 3 575 277A1 Specification [Patent Document 3] International Publication No. 2019 / 146908 [Patent Document 4] International Publication No. 2015 / 148215A1 [Overview of the Initiative] [Means for solving the problem]

[0015] This invention is based on the problem of providing an agent that can increase the opacity of zirconium oxide ceramics. Zirconium oxide ceramics treated with this agent should exhibit advantageous properties not only in terms of aesthetic appearance but also in terms of mechanical properties and fit accuracy. The agent should be usable for thin-walled dental restorations. In addition, the agent should be harmless to health and allow for simple processing. Furthermore, the agent should have high stability during storage and long-term homogeneity.

[0016] Surprisingly, this problem is solved by the dental opacifying agent composition according to claims 1 to 13. The present invention also relates to a process for manufacturing a dental restoration according to claims 14 to 18 and to the use according to claim 19.

[0017] The dental opacifying agent composition according to the present invention comprises (a) an alkali silicate and (b) water, and is characterized in that here, the alkali silicate is at least partially dissolved in water.

[0018] Surprisingly, by using the composition according to the present invention, it has been found that a high opacity can be achieved in oxide ceramics, particularly zirconium oxide ceramics, without using opacifying metal ions such as ions of Al, La, Zr and / or Ti, or metal oxide nanoparticles containing, for example, Al, Ti and / or Zr.

[0019] The opacifying effect of the composition can be limited to the region of the oxide ceramic near the surface, enabling the achievement of a desirable aesthetic effect even in very thin and aesthetic dental restorations for covering discolored roots or dark implants.

[0020] Furthermore, surprisingly, the composition according to the present invention enables the production of dental restorations which, in addition to the desired aesthetic properties, also exhibit particularly advantageous mechanical properties. It is possible to obtain dental restorations having the desired opacity properties, characterized by strength and long-term stability, within the range of oxide ceramics, particularly zirconium oxide ceramics, which have not been treated with an opacifying agent composition.

[0021] Furthermore, the composition according to the invention can also be used to obtain dental restorations that are characterized not only by the desired opacity properties but also by high adaptation accuracy. The oxide ceramic treated with the composition has less sintering distortion during final high-density sintering and exhibits advantageous sintering behavior. Therefore, dental restorations with the desired aesthetic properties can be obtained and placed in the patient's mouth without additional steps to adjust the adaptation to the prepared root stump or implant interface. This application provides, for example, the following: (Item 1) (a) An alkali silicate and (b) Water A dental opacifying agent composition comprising, where the alkali silicate is at least partially dissolved in the water, the dental opacifying agent composition. (Item 2) The composition according to item 1, comprising a thickener, preferably an organic thickener. (Item 3) The composition according to any one of the preceding items, wherein the thickener is selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, polypropylene glycol, hydroxyethyl cellulose, ethyl cellulose, methyl cellulose, xanthan gum, carbomer, pectin, silica sol, starch, gelatin, alginate, and mixtures thereof, and particularly preferably polyvinylpyrrolidone, polyethylene glycol, or mixtures thereof. (Item 4) The composition according to any one of the preceding items, wherein the alkali silicate is selected from lithium silicate, sodium silicate, potassium silicate, and mixtures thereof, particularly sodium silicate. (Item 5) The composition according to any one of the preceding items, wherein the polyvinylpyrrolidone has a molecular weight in the range of 10,000 to 1,000,000 g / mol and the polyethylene glycol has a molecular weight in the range of 200 to 100,000 g / mol, each based on the weight average molecular weight. (Item 6) A composition according to any one of the preceding items, comprising 0.5 to 37% by weight, preferably 0.5 to 20% by weight, and particularly preferably 1 to 10% by weight of alkali silicate. (Item 7) A composition according to any one of the preceding items, comprising 63 to 99.5% by weight, preferably 80 to 99.5% by weight, and particularly preferably 90 to 99.0% by weight of water. (Item 8) A composition according to any one of the preceding items, comprising 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, and particularly preferably 0.5 to 20% by weight of a thickening agent. (Item 9) A composition according to any one of the preceding items, comprising 0 to 30% by weight, preferably 0.1 to 30% by weight, particularly 0.2 to 20% by weight, and especially preferably 0.5 to 10% by weight of polyvinylpyrrolidone. (Item 10) A composition according to any one of the preceding items, comprising 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, and especially preferably 0.5 to 20% by weight of polyethylene glycol. (Item 11) A composition according to any one of the preceding items, which exists in the form of a liquid, particularly in the form of a solution. (Item 12) A composition according to any one of the preceding items, having a pH value in the range of 7.5 to 12.5, preferably 8.5 to 12.5, and particularly preferably 9.5 to 12. (Item 13) 1 to 100s -1 The composition according to any one of the preceding items, having a viscosity in the range of 1 to 5,000, preferably 1 to 1,000, and particularly preferably 1 to 100 mPa·s, within the shear rate range. (Item 14) A process for manufacturing a dental restoration, comprising increasing the opacity of at least a portion of an oxide ceramic, particularly a zirconium oxide ceramic, by imparting the composition described in any one of the preceding items to the portion and subjecting it to heat treatment. (Item 15) The process according to any one of the preceding items, wherein the oxide ceramic is pre-sintered. (Item 16) The process according to any one of the preceding items, wherein the heat treatment involves high-density sintering of the oxide ceramic. (Item 17) The process according to any one of the preceding items, wherein treatment with an etching solution is performed on a portion of the oxide ceramic whose opacity has been increased. (Item 18) The process described in any one of the preceding items, wherein the dental restoration is a bridge, inlay, onlay, veneer, abutment, partial crown, crown, or facet. (Item 19) Use of any one of the preceding items to increase the opacity of oxide ceramics, particularly zirconium oxide ceramics, in the manufacture of dental restorations. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 shows high-density sintered zirconium oxide ceramics. The zirconium oxide ceramic on the left is treated with the opacifier composition of Example 3, the zirconium oxide ceramic in the center is treated with the opacifier composition of Example 4, and the zirconium oxide ceramic on the right is treated with the opacifier composition of Example 5. [Figure 2] Figure 2 shows a pre-sintered zirconium oxide ceramic treated with an opacifying agent composition. [Figure 3] Figure 3 shows a high-density sintered zirconium oxide ceramic following the procedures described for Examples 1 and 2. [Figure 4] Figure 4 shows the microstructure of a surface region treated with the compositions listed in Table 5. [Figure 5] Figure 5 shows exemplary 3D measurement results of specimens from Examples 9-11 after high-density sintering. [Modes for carrying out the invention]

[0023] The present invention relates to a dental opacifying agent composition that can be used to increase the opacity of zirconium oxide ceramics. Furthermore, the present invention relates to a process for manufacturing a dental restoration in which the opacity of zirconium oxide ceramics is increased by using the opacifying agent composition. For the purposes of this invention, the term “opacifying agent composition” refers to a composition suitable for increasing the opacity of oxide ceramics, particularly zirconium oxide ceramics. In this context, the increase in opacity occurs particularly after the oxide ceramic has come into contact with the composition and has also undergone heat treatment. The increase in opacity occurs not by imparting an opaque layer to the oxide ceramic, but particularly within the oxide ceramic itself. Opacifying agent compositions are particularly suitable for increasing the opacity of pre-sintered zirconium oxide ceramics made from tetragonal polycrystalline materials, preferably stabilized with Y2O3.

[0024] Opacity is the non-transparency to light and is inversely related to translucency, i.e., the light transmittance of a material. Translucency is the ratio of the intensity of transmitted light to the intensity of incident light. As a measure of opacity or translucency, the contrast value (CR value) can be determined according to British Standard 5612. The increase in opacity according to the present invention exists when the opacity increases in a portion of oxide ceramics, particularly zirconium oxide ceramics, such as high-density sintered dental restorations, which are treated with an opacifying agent composition and heat-treated as necessary, compared to another untreated portion of the oxide ceramic. If the entire oxide ceramic is treated with the composition, the comparative value can be determined using an untreated oxide ceramic prepared in the corresponding manner. The increase in opacity is also referred to as "opacification" for the purposes of this application.

[0025] For the purposes of this invention, the terms “color” and “colored” refer to the lightness and / or brightness of a material. Lightness and brightness can be determined by L*a*b values, particularly according to DIN EN ISO 11664-4, or according to shade guides commonly used in the dental industry. Colorimetric measurements can be performed using commercially available measuring instruments such as the CM-3700d spectrophotometer (Konica Minolta). Examples of shade guides include Vitapan classical® and Vita 3D Master® from VITA Zahnfabrik H. Rauter GmbH & Co. KG, and Chromascop® from Ivoclar Vivadent AG.

[0026] While not limited to any particular theory, it is thought that a thin glass phase may form on the oxide ceramic grains in the oxide ceramic after the opacifying agent composition is applied. The increase in opacity is thought to be due to the difference in refractive index between the oxide ceramic phase and the glass phase.

[0027] The alkali silicate is preferably selected from lithium silicate, sodium silicate, potassium silicate, and mixtures thereof, and especially from sodium silicate.

[0028] Preferably, the alkali silicate may be in the form of sodium water glass, potassium water glass, or lithium water glass, and especially sodium water glass. For the purposes of the present invention, sodium water glass is a water glass containing sodium silicate and optionally other alkali silicates, where sodium silicate represents the maximum weight proportion of silicate. Thus, potassium water glass and lithium water glass have potassium silicate and lithium silicate as the main weight proportions, respectively. Preferably, the density of sodium water glass is 1.34 to 1.38 g / cm³ 3 The density of potassium water glass is 1.23 to 1.27 g / cm³. 3 , especially 1.25 g / cm³ 3 The density of lithium water glass is 1.16 to 1.20 g / cm³. 3, especially 1.18 g / cm³ 3 That is the case.

[0029] In a preferred embodiment, the composition contains 0.5 to 37% by weight, preferably 0.5 to 20% by weight, and more preferably 1 to 10% by weight of alkali silicate.

[0030] The alkali silicate present in the opacifying agent composition can be detected, for example, by X-ray fluorescence analysis (XRF), Si-NMR, 13 The opacifier can be qualitatively detected or quantitatively determined by 13C-NMR, atomic absorption spectrometry (AAS), or Raman spectroscopy, and, if necessary, combined with further indirect analyses such as pH measurement of the dried or crystallized opacifier composition, ignition residue analysis, or scanning electron microscopy.

[0031] In a more preferred embodiment, the composition comprises 0.001 to 10% by weight, preferably 0.001 to 8% by weight, and particularly 0.001 to 5% by weight of Si (calculated as SiO2), and 0.0001 to 10% by weight, preferably 0.001 to 8% by weight, and particularly 0.01 to 5% by weight of an alkali metal (calculated as an alkali metal oxide).

[0032] The composition more preferably contains 63 to 99.5% by weight, preferably 80 to 99.5% by weight, and more preferably 90 to 99.0% by weight of water.

[0033] In a more preferred embodiment, the weight ratio of alkali silicate to water in the composition is in the range of 1:200 to 1:6, particularly 1:100 to 1:8.

[0034] It is even more preferable that the alkali silicate is completely dissolved in water.

[0035] In a more preferred embodiment, the alkali silicate exists in the form of water glass, where the weight ratio of Si (calculated as SiO2) to alkali metal (calculated as alkali metal oxide) is 1 to 6, preferably 1.5 to 6, and particularly preferably 2 to 6.

[0036] In another preferred embodiment, the composition according to the present invention comprises a thickener, preferably an organic thickener.

[0037] A thickening agent is understood to be an agent that can increase the viscosity of a solution, preferably an aqueous solution.

[0038] We found that the addition of a thickening agent can affect how deeply the opacifying agent composition penetrates the zirconium oxide ceramic. This is particularly advantageous when the opacifying effect of the composition is limited to areas near the surface. In this way, covering discolored root remnants or dark implants can be achieved even with thin-walled dental restorations without undesirable aesthetic effects on the outside of the restoration.

[0039] In preferred embodiments, the thickener is a polysaccharide. It is more preferable that the thickener is selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, polypropylene glycol, hydroxyethylcellulose, ethylcellulose, methylcellulose, xanthan gum, carbomer, pectin, silica sol, starch, gelatin, alginate, and mixtures thereof, and is particularly preferable to be polyvinylpyrrolidone, polyethylene glycol, or a mixture thereof. Particularly preferable is the thickener being polyvinylpyrrolidone.

[0040] In either case, polyvinylpyrrolidone preferably has a molecular weight in the range of 10,000 to 1,000,000 g / mol based on its weight-average molecular weight, and polyethylene glycol preferably has a molecular weight in the range of 200 to 100,000 g / mol.

[0041] Polyvinylpyrrolidone having a weight-average molecular weight of 10,000 to 500,000 g / mol, and particularly 10,000 to 100,000 g / mol, is especially preferred.

[0042] It has been found that the use of polyvinylpyrrolidone significantly facilitates the preparation of clear solutions of the compositions according to the present invention. In particular, the use of polyvinylpyrrolidone allows for faster preparation of the compositions to obtain clear solutions, and eliminates extensive dissolution and mixing procedures, such as the use of ultrasonic baths.

[0043] The use of polyvinylpyrrolidone has also proven advantageous in terms of the stability of the composition according to the present invention. The use of polyvinylpyrrolidone makes it possible to avoid adverse effects on the storage of the composition, such as phase separation or precipitation.

[0044] In particular, compositions containing polyvinylpyrrolidone have been shown to be less prone to forming undesirable turbidity and aggregation compared to compositions containing other thickeners. Since such turbidity and aggregation are visible to the naked eye, their formation can be monitored, for example, by observing the composition.

[0045] Polyethylene glycol having a weight-average molecular weight of 200 to 50,000 g / mol, and particularly 200 to 35,000 g / mol, is especially preferred.

[0046] The composition preferably contains a thickening agent in an amount of 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, and especially preferably 0.5 to 20% by weight.

[0047] In a preferred embodiment, the composition contains 0 to 30% by weight, preferably 0.1 to 30% by weight, particularly 0.2 to 20% by weight, especially preferably 0.5 to 10% by weight, and even more preferably 0.5 to 6% by weight of polyvinylpyrrolidone.

[0048] In a more preferred embodiment, the weight ratio of the thickener, particularly polyvinylpyrrolidone, to water in the composition is in the range of 1:200 to 1:10, particularly 1:100 to 1:12, and especially preferably 1:50 to 1:15.

[0049] It is also preferable that the weight ratio of the thickener in the composition, particularly polyvinylpyrrolidone to alkali silicate, is in the range of 1:20 to 5:1, and especially 1:15 to 1:4.

[0050] In another preferred embodiment, the composition comprises 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, and especially preferably 0.5 to 20% by weight of polyethylene glycol.

[0051] It has been shown that the penetration depth of opacifying agent compositions may be affected by the proportion of thickeners such as polyvinylpyrrolidone and polyethylene glycol, as well as the properties of the thickeners. In principle, for example, if the proportion of polyvinylpyrrolidone or polyethylene glycol is high, and the molecular weight of these components is high, the penetration depth may decrease, and the opacifying effect on the observer may be reduced.

[0052] In a preferred embodiment, the opacifying agent composition according to the present invention further comprises an organic solvent, preferably in an amount of 0.5 to 30% by weight, particularly 1 to 20% by weight. Suitable organic solvents are particularly miscible with water and are selected from the group consisting of methanol, ethanol, isopropanol, glycerol, ethylene glycol, acetone, 1,4-dioxane, and mixtures thereof. Advantageous wetting and drying properties of the opacifying agent composition can be provided, for example, by the addition of an organic solvent.

[0053] In preferred embodiments, the composition is substantially free of metal oxide nanoparticles. It is even more preferable that the composition is substantially free of Al, La, Zr, P, and Ti.

[0054] It is even more preferable that the opacifying agent composition contains an identification color. For the purposes of the present invention, the identification color is an agent that has a coloring effect on the composition without significantly affecting the color of the high-density sintered oxide ceramic, particularly zirconium oxide ceramic. Preferred identification colors are organic dyes, particularly triphenylmethane dyes such as Patent Blue V (E131). The identification color improves the visibility of the composition according to the present invention on pre-sintered oxide ceramic, thereby facilitating the accurate application of the composition.

[0055] The composition according to the present invention is more preferably in liquid form, particularly in solution form. This facilitates application to oxide ceramics, for example, using a brush or a suitable applicator. Particularly preferably, the composition is in homogeneous liquid form to ensure a certain opacification effect.

[0056] The composition is particularly preferably having a pH value in the range of 7.5 to 12.5, preferably 8.5 to 12.5, and especially preferably 9.5 to 12. In this way, the risk of acidic or alkaline burns to users of the opacifying agent composition is reduced. In particular, the occupational safety of dental technicians and dentists is improved compared to known opacifying agent compositions from the prior art having a pH value greater than 12.5.

[0057] In another preferred embodiment, the composition is heated at room temperature, i.e., 23°C, for 1 to 100 seconds. -1 The viscosity is in the range of 1 to 5,000, preferably 1 to 1,000, and particularly preferably 1 to 100 mPa·s, within the shear rate range. The viscosity can be determined, for example, using a CP50 measuring system (50 mm diameter cone plate) with an MCR302 rheometer manufactured by Anton Paar GmbH. Typically, compositions having a viscosity within the mentioned range have particularly advantageous properties in terms of processability.

[0058] The present invention further relates to a process for manufacturing dental restorations, wherein opacity is increased by applying the above-described composition according to the present invention to at least a portion of an oxide ceramic, particularly a zirconium oxide ceramic, and then subjecting it to heat treatment.

[0059] Preferably, the heat treatment is carried out at a temperature of at least 1 minute, and more preferably at least 10 minutes, preferably at 1000 to 1700°C, particularly 1000 to 1600°C, and more preferably 1000 to 1500°C.

[0060] It is preferable that the composition penetrates the oxide ceramic to a depth of 1 to 2000 μm, particularly 2 to 1000 μm, and especially preferably 5 to 500 μm. The penetration depth can be determined by treating the oxide ceramic with the composition, heat-treating it, then splitting it using, for example, a saw, and then measuring how far the composition has penetrated the oxide ceramic onto the surface accessible by the splitting using a microscope (e.g., Olympus SZX10).

[0061] It is also preferable to apply an opacifying agent composition to the lumen of the fabricated dental restoration.

[0062] In a preferred embodiment, opacity is increased in at least a portion of the oxide ceramic to which a barrier agent has been pre-applied and, if necessary, dried. A barrier agent is an agent that, after being applied to the oxide ceramic and, if necessary, after drying, can reduce the penetration depth of the opacifying agent composition in the oxide ceramic. In principle, the barrier agent forms a barrier layer in the oxide ceramic that prevents the penetration of the opacifying agent composition.

[0063] In preferred embodiments, the barrier agent comprises a solvent, particularly an organic solvent, and a polymer dispersed therein, particularly a thickener, and optionally an identifying color. Suitable thickeners are described in relation to opacifying agent compositions.

[0064] In another preferred embodiment, the same or a different composition according to the present invention is again applied to at least a portion of the oxide ceramic to which the opacifying agent composition has been applied. Preferably, the composition is first dried before repeated application, before the same or a different composition according to the present invention is again applied. By applying the opacifying agent composition multiple times, it is also possible to generate complex three-dimensional opacity gradients, in combination with selecting compositions with different properties, such as different penetration depths, as needed.

[0065] Oxide ceramics, particularly zirconium oxide ceramics, can be unsintered or pre-sintered when the composition according to the present invention is applied. Pre-sintering of the oxide ceramic is particularly preferred. Pre-sintered oxide ceramics typically exist in an open state with a density preferably 30 to 70%, particularly 40 to 65%, of the density of high-density sintered oxide ceramics. Generally, a lower density of pre-sintered oxide ceramics is associated with a greater penetration depth of the opacifying agent composition.

[0066] In a particularly preferred embodiment, the heat treatment involves high-density sintering of the oxide ceramic.

[0067] Typically, dental restorations with desirable properties can be obtained by high-density sintering. Oxide ceramics, particularly zirconium oxide ceramics, whose opacity is increased by the composition according to the present invention have been shown to exhibit favorable sintering behavior with less sintering distortion.

[0068] The process according to the present invention makes it possible to manufacture dental restorations having advantageous mechanical properties.

[0069] Preferably, a high-density sintered dental restoration manufactured according to the process of the present invention has a biaxial fracture strength of at least 500 MPa, particularly at least 600 MPa, and especially preferably at least 700 MPa, as determined in accordance with ISO 6872:2015.

[0070] It is also preferable that high-density sintered dental restorations manufactured according to the process of the present invention have a biaxial fracture strength of at least 70%, preferably at least 80%, and particularly at least 95%, in each case, determined based on the biaxial fracture strength of the corresponding high-density sintered dental restoration that has not been treated with an opacifying agent composition, in accordance with ISO 6872:2015.

[0071] It is also preferable that high-density sintered dental restorations prepared according to the process of the present invention exhibit high long-term stability. Particularly preferable, the high-density sintered dental restoration is characterized by passing a fatigue test in which the dental restoration is loaded at a load of at least 450 N, preferably at least 550 N, and particularly preferably at least 650 N, using a 5 kN servopneumatic 2-column benchtop tester manufactured by DYNA-MESS Prufsysteme GmbH, with hot water at 37°C and a sinusoidal frequency of 5 Hz (preload is 10% of the main load), for 2,000,000 test cycles.

[0072] Dental restorations manufactured according to the process of the present invention can be attached to the skeletal structure of a root remnant or implant by any known method (e.g., cementing, bonding, or screwing).

[0073] Chemical and mechanical methods for pre-treating zirconium oxide surfaces to enhance their bond to the root remnant or implant surface are known from the prior art.

[0074] In a preferred embodiment of the process, treatment with an etching solution is carried out on a portion of the oxide ceramic in which the opacity of the oxide ceramic has been increased. The treatment can be carried out on a portion of the opacified portion and may extend to the non-opaque portion of the oxide ceramic. Surprisingly, treatment with an etching solution has also been shown to lead to improved bonding with the root or implant in the area treated with the opacifying agent composition.

[0075] In a particularly preferred embodiment, the etching solution contains hydrofluoric acid.

[0076] In another preferred embodiment of the process, the dental restoration is a bridge, inlay, onlay, veneer, abutment, partial crown, crown, or facet.

[0077] The present invention further relates to the use of a dental opacifying agent composition according to the present invention for increasing the opacity of oxide ceramics, particularly zirconium oxide ceramics, in the manufacture of dental restorations.

[0078] All compositional definitions, process steps, and process parameters described in relation to the opacifying agent composition and process according to the present invention are also suitable for this use according to the present invention.

[0079] The present invention will be described in more detail below with reference to examples. [Examples]

[0080] Examples 1 and 2: Opaquer agent compositions according to the present invention.

[0081] The solution was prepared using the chemical composition shown in Table 1. Table 1 [Table 1]

[0082] Sodium water glass of "ultra-high purity" manufactured by Carl Roth GmbH (which, according to the manufacturer, contains no other alkali silicates other than sodium silicate) and polyvinylpyrrolidone (PVP) K30 of "ultra-high purity" manufactured by BASF SE and sold under the name Luviskol® K30 were used for the preparation of these and the following examples. According to the manufacturer, Luviskol® K30 consists of polyvinylpyrrolidone with a K value (Fikentscher, 1% in water) of 27.0 to 33.0 and a weight-average molecular weight of approximately 49,000 g / mol. The weight percentages of content shown in Table 1 and all subsequent tables and in the composition of each component correspond to the manufacturer's specifications.

[0083] Two pre-sintered zirconium oxide ceramics in the form of dental crowns were provided. The solutions of Examples 1 and 2 were applied to the inner surface of each crown with a brush and air-dried. The crowns were then sintered to high density at 1500°C for 120 minutes in an Ivoclar Vivadent AG Programat S1-1600 furnace.

[0084] After high-density sintering, opacity was observed in both crowns of the solution-treated surface region, and it increased compared to the untreated region. Examples 3 to 5: Opaquer agent compositions containing PVP K30, K90, and K360

[0085] The opacifying agent compositions were prepared using the chemical compositions shown in Table 2. Table 2 [Table 2]

[0086] Three pre-sintered zirconium oxide ceramics were provided in the form of dental crowns, which were then treated with the opacifying agent compositions of Examples 3 to 5 and heat-treated according to the procedures described for Examples 1 and 2.

[0087] High-density sintered zirconium oxide ceramics are shown in Figure 1. The zirconium oxide ceramic on the left was treated with the opacifying agent composition of Example 3, the zirconium oxide ceramic in the center was treated with the opacifying agent composition of Example 4, and the zirconium oxide ceramic on the right was treated with the opacifying agent composition of Example 5. To the observer, it is clear that the opacification effect of Example 3, i.e., the composition using polyvinylpyrrolidone K30, is the strongest. Example 6: Opaquer agent composition with identification color

[0088] Solutions having the chemical compositions shown in Table 3 were prepared and applied to pre-sintered zirconium oxide ceramics in the form of small plates, up to four layers thick. Table 3 [Table 3]

[0089] Figure 2 shows a pre-sintered zirconium oxide ceramic treated with an opacifying agent composition. The addition of a distinguishing color allowed the treated area of ​​the zirconium oxide ceramic to be clearly distinguished from the untreated area.

[0090] Zirconium oxide ceramics were sintered to high density according to the procedures described in Examples 1 and 2. The opacity of the high-density sintered zirconium oxide ceramic increased in the areas treated with the opacifying agent composition compared to the untreated areas. This is also evident from the zirconium oxide ceramic shown in Figure 3. Example 7: Determination of the penetration depth of the opacifying agent solution

[0091] Pre-sintered zirconium oxide ceramics in the shape of small plates were provided and treated with an opacifying agent solution having the chemical composition shown in Table 4 by applying approximately 3 μl of opacifying agent solution to the zirconium oxide ceramics. Table 4 [Table 4]

[0092] Zirconium oxide ceramics were sintered to high density according to the procedures described in Examples 1 and 2, and then cut to determine the penetration depth of the opacifying agent solution. A penetration depth of 0.14 mm was obtained by measurement using an Olympus SZX10 microscope. Example 8: Microstructure analysis using SEM

[0093] Pre-sintered zirconium oxide ceramics were treated with the opacifying agent compositions shown in Table 5. Table 5 [Table 5]

[0094] Zirconium oxide ceramics were sintered to high density according to the procedures described in Examples 1 and 2. Subsequently, the microstructure of the zirconium oxide ceramics was examined by scanning electron microscopy (SEM). Figure 4 shows the microstructure of the surface regions treated with the compositions shown in Table 5. It can be seen that the structure of the zirconium oxide ceramics is characterized by small grain sizes. Furthermore, no pores were observed. Examples 9 to 11: Test specimens for measuring biaxial fracture strength

[0095] To determine the biaxial fracture strength according to ISO 6872:2015, disc-shaped test specimens with a thickness of 1.2 mm and a diameter of 13.0 mm were fabricated from pre-sintered zirconium oxide.

[0096] A barrier agent containing 65.37% by weight of H2O, 18.247% by weight of PVP K30, 16.343% by weight of ethanol, and 0.04% by weight of Patent Blue V (E131) was applied to the test specimens of Examples 10 and 11 and dried.

[0097] Three opacifying agent solutions were prepared using the chemical compositions shown in Table 6. Table 6 [Table 6]

[0098] Each of the five specimens was treated with the opacifying agent compositions of Examples 9 to 11 by applying 3 μl of the opacifying agent composition to each specimen. All specimens were sintered to high density and placed on three concentrically arranged balls, with a load applied to the center until they broke.

[0099] Table 7 shows the average biaxial fracture strength of the specimens from Examples 9 to 11. Table 7 JPEG2022179425000007.jpg2992

[0100] No deformation was observed in the specimens of Examples 9 to 11 after high-density sintering. For illustrative purposes, the specimens were subjected to 3D measurement using an optical 3D scanner (Model ATOS Capsule, manufactured by GOM GmbH). An example of the 3D measurement results is shown in Figure 5. Example 12: Fatigue Test

[0101] Four 3-unit rear bridges were fabricated from zirconium oxide (e.max ZirCAD from Ivoclar Vivadent AG). The bridges had a wall thickness of 0.6 mm and a connector cross-section of approximately 3 mm x 3 mm.

[0102] The opacifying agent composition according to the present invention was prepared from 21.37 g of H2O, 1.125 g of PVP K30, and 2.5 g of sodium aqueous glass (33.6 to 37 wt% solution). The composition was applied to the entire luminal surface of two posterior bridges. The remaining two posterior bridges were not coated with the opacifying agent composition. All four posterior bridges were sintered to high density.

[0103] Next, the posterior bridge was attached to the polymethyl methacrylate (PMMA) root by first mechanically roughening the inner surface of the posterior bridge and the upper surface of the root retention by sandblasting, and then bonding them together with self-hardening glass ionomer cement (Vivaglass CEM from Ivoclar Vivadent AG).

[0104] Next, the rear bridge was subjected to fatigue testing in 37°C hot water at a sinusoidal frequency of 5 Hz (preload is 10% of the main load) with a load of 550 N for 2,000,000 cycles using a DYNA-MESS Pruefsysteme GmbH servo-pneumatic 2-column benchtop testing machine 5kN (2-column benchtop testing machine 5kN).

[0105] Both the two rear bridges treated with the opacifying agent composition and the two bridges not treated with the opacifying agent composition showed no visible damage after the completion of the fatigue test. Examples 13 and 14: Homogeneity of the composition

[0106] Two opacifying agent compositions having the chemical compositions shown in Table 8 were prepared. For this purpose, sodium aqueous glass was first homogenized with water at room temperature for about 15 minutes. Then, a thickener was added and another homogenization step was performed. A magnetic stirrer at a speed of 400 to 600 rpm was used for homogenization. Table 8 [Table 8]

[0107] The compositions were thoroughly examined for homogeneity immediately after their preparation. The compositions were then stored at room temperature and periodically re-examined for homogeneity over several weeks.

[0108] In the composition of Example 14, aggregation was observed immediately after preparation, and the amount of aggregates formed increased noticeably as storage time progressed. The aggregates settled at the bottom of the vial.

[0109] On the other hand, the composition of Example 13 was transparent immediately after preparation, and no aggregation was observed. The first aggregates were not visible until more than two weeks later, and aggregation was considerably slower than that of the composition of Example 14.

Claims

1. A dental opacifying agent composition comprising: (a) an alkali silicate and (b) water, wherein the alkali silicate is at least partially dissolved in the water.

2. The composition according to claim 1, further comprising a thickening agent, preferably an organic thickening agent.

3. The composition according to claim 2, wherein the thickening agent is selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol, polypropylene glycol, hydroxyethyl cellulose, ethyl cellulose, methyl cellulose, xanthan gum, carbomer, pectin, silica sol, starch, gelatin, alginate, and mixtures thereof, and particularly preferably polyvinylpyrrolidone, polyethylene glycol, or mixtures thereof.

4. The composition according to claim 1, wherein the alkali silicate is selected from lithium silicate, sodium silicate, potassium silicate, and mixtures thereof, particularly sodium silicate.

5. The composition according to claim 3, wherein the polyvinylpyrrolidone has a molecular weight in the range of 10,000 to 1,000,000 g / mol and the polyethylene glycol has a molecular weight in the range of 200 to 100,000 g / mol, each based on the weight average molecular weight.

6. The composition according to claim 1, comprising 0.5 to 37% by weight, preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight of an alkali silicate.

7. The composition according to claim 1, comprising 63 to 99.5% by weight, preferably 80 to 99.5% by weight, particularly preferably 90 to 99.0% by weight of water.

8. The composition according to claim 2, comprising 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, particularly preferably 0.5 to 20% by weight of a thickening agent.

9. The composition according to claim 3, comprising 0 to 30% by weight, preferably 0.1 to 30% by weight, particularly 0.2 to 20% by weight, particularly preferably 0.5 to 10% by weight of polyvinylpyrrolidone.

10. The composition according to claim 3, comprising 0 to 50% by weight, preferably 0.1 to 50% by weight, particularly 0.2 to 30% by weight, particularly preferably 0.5 to 20% by weight of polyethylene glycol.

11. The composition according to claim 1, which is in liquid form, particularly in the form of a solution. The composition according to claim 11, having a pH value in the range of 7.5 to 12.5, preferably 8.5 to 12.5, particularly preferably 9.5 to 12.

13. From 1 to 100 s －１ The composition according to claim 1, having a viscosity in the range of 1 to 5,000, preferably 1 to 1,000, particularly preferably 1 to 100 mPa·s, in the shear rate range of

14. A process for producing a dental restoration, wherein the opacity in at least a part of an oxide ceramic, particularly a zirconium oxide ceramic, is increased by applying the composition according to any one of claims 1 to 13 to this part and subjecting it to a heat treatment.

15. The process according to claim 14, wherein the oxide ceramic is pre-sintered.

16. The process according to claim 14, wherein the heat treatment involves high-density sintering of the oxide ceramic.

17. The process according to claim 14, wherein the treatment with an etching solution is carried out on the part of the oxide ceramic with increased opacity.

18. The process according to claim 14, wherein the dental restoration is a bridge, inlay, onlay, veneer, abutment, partial crown, crown or facet.

19. Use of the composition according to any one of claims 1 to 13 for increasing the opacity of an oxide ceramic, particularly a zirconium oxide ceramic, in the production of a dental restoration.

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