KR20190093512A - Radiopaque glass and use thereof - Google Patents

Abstract

The present invention relates to a radiopaque glass having a refractive index (n_d) of 1.480 to 1.561. The glass does not contain SrO and PbO other than impurities and is based on a system of SiO_2, Al_2O_3 and B_2O_3. Radiopacity is adjusted by using Cs_2O with optional fluorine, in particular in combination with BaO and/or SnO_2. In particular, the glass can be used as dental glass or as optical glass.

Description

Radiopaque glass and its uses {RADIOPAQUE GLASS AND USE THEREOF}

The present invention relates to lead-free radiopaque glass and its use.

In the dental field, polymer-based dental compositions are increasingly used for dental restorations. Such polymer-based dental compositions are conventionally comprised of a matrix of organic resins and various inorganic fillers. Inorganic fillers consist primarily of powders of glass, (glass-) ceramic, quartz or other crystalline materials (eg YbF ₃ ), sol-gel materials and / or aerosols and are added as fillers to the polymer-based composition. .

The purpose of using polymer-based dental compositions is to prevent possible harmful side effects of amalgam and to improve aesthetics. Depending on the polymer-based dental composition chosen, it can be used for example for dental fillings or for various dental restoration measures with regard to inlays, onlays, etc., and also crowns and bridges.

Such fillers are intended to minimize shrinkage resulting from the polymerization of the resin matrix upon curing, while at the same time increasing wear resistance. For example, if there is a strong adhesion between the tooth wall and the filler, excessive polymerization shrinkage can cause the tooth wall to crack. If the adhesion is not sufficient for this purpose, excessive polymerization shrinkage can result in the formation of a marginal gap between the tooth wall and the filler, which can promote secondary caries.

In addition, certain physical and chemical requirements are imposed on the filler:

The filler must be processed to produce very fine powder. The finer the powder, the more homogeneous the appearance of the filling. At the same time there is an improvement in the polishing properties of the filling, which leads to improved wear resistance through the reduction of the open surface area which may be invasive, which allows the filling to maintain its durability for longer periods of time. Thus, it is preferable that the said powder is easy to process, and that powder does not advance aggregation.

It is also advantageous if the filler is coated with functionalized silanes, as this facilitates the formulation of the dental composition and improves the mechanical properties. The surface of the filler particles is at least partially covered with conventionally functionalized silanes.

In terms of its transparency and, where appropriate, the refractive index, the dental glass filler should fit as closely as possible to the resin matrix. Moreover, in its entirety, which also includes fillers, the polymer-based dental compositions apply aesthetically well to natural dental materials so as to be indistinguishable from the surrounding healthy dental materials. Powdered fillers of very small particle size can likewise play a role in aesthetic criteria.

The effective chemical resistance of the fillers, especially with regard to water, can also contribute to the long life of the tooth restorative means.

In addition, what can be seen in the X-ray image of the dental restoration means is absolutely essential for the treatment of the patient. Since the resin matrix is generally not visible in the X-ray image, the filler must ensure the necessary X-ray absorption. Fillers of this kind that provide adequate absorption of X-rays are referred to as radiopaque. The components of the filler are relevant for radiopacity, examples being glass, or certain components of additives. Such additives are also referred to as radiopaques. Conventional radiopaque agents other than dental glass fillers are YbF ₃ , which may be added in crystalline ground form. Such additives are also referred to as radiopaques. In addition to dental glass fillers, conventional radiopaque agents are YbF ₃ , which may be added in crystalline finely divided form.

According to DIN ISO 4049, the radiopacity of dental glass or dental materials is recorded as aluminum equivalent thickness (ALET) with respect to aluminum X-ray absorption. Relative ALET is based on a sample thickness of 2 mm. Thus, a relative ALET of 200% means that a glass plate with a parallel planar surface with a thickness of 2 mm causes the same attenuation of X-rays with an aluminum plate with a thickness of 4 mm. Similarly, a relative ALET of 500% means that a glass plate with a parallel planar surface of 2 mm in thickness causes the same attenuation of X-rays as a 10 mm thick aluminum plate. In the following, the radiopacity of the glass is reported in terms of relative ALET (unit%).

Since polymer-based dental compositions in applications are conventionally injected into the voids from the cartridge, when it is modeled, it is intended to be thixotropic in the frequently uncured state. It decreases its viscosity when pressure is applied, while without exposure to pressure it is stable in dimensions.

With regard to the filler material, inert compositions are distinguished from reactive dental compositions. Reactive dental compositions include dental cement. In the case of dental cement, an example is glass earomer cement, and the chemical reaction of the filler and organic acid causes curing of the dental composition, and the curing properties of the dental composition and thus its workability affect the filler's reactivity. Receive. The process related to this application is usually one of the settings that can be carried out, for example, by superficial radical curing under the action of ultraviolet light. The glass herein may act as a filler to induce or participate in a chemical reaction or as an inert additive not involved in the reaction. In this case, the chemical reaction is likewise determined by the additional filler present in the glass ionomer cement.

Apart from pure inert fillers and pure reactive fillers, there are various intermediate steps, which will not be listed in detail. As examples of intermediate steps, mention may be made of "compomers" and "resin modified glass ionomer cements" (RMGIC).

Composites, also referred to as filler composites, contain on the other hand additional fillers which are usually inert, the curing properties of which are determined by the components of the resin matrix and are thus initially determined and the chemical reaction of the fillers and / or additives. Is usually not preferred here.

Based on their different composition, they are usually used as fillers for polymer-based dental compositions because glass represents a class of materials with various properties. Applications other than dental materials, either in pure form or as a component of a substance mixture, may also include, for example, the preservative and / or protective properties of shaped, artificial dental materials or prostheses for inlays, onlays, and also crowns and bridges. It may be possible to relate to a material for treating teeth. In these applications, such as dental materials, such glass is generally referred to as dental glass.

Another preferred property of the dental glass other than that described above is that it does not contain toxic lead oxide (PbO).

Thus, dental glass particularly refers to high grade glass. Such glass can likewise be used in optical applications, in particular in the radiopaque advantages of glass. Since radiopacity means that the glass absorbs electromagnetic radiation in the region of the X-ray spectrum, it means that this glass is at the same time a filter for X-radiation. Sensitive electronic components can be damaged by X-radiation. In the case of an electronic image sensor, for example, the passage of both X-rays may damage the corresponding area of the sensor or may be undesired, for example, which may be received such as image interference and / or noise pixels. Can cause a signal. Thus, for certain applications, it is necessary or at least advantageous for the electronic component to be protected from X-radiation by filtering such radiation from the spectrum of incident radiation using the corresponding glass.

Numerous dental glasses and other optical glasses having similar optical positions or similar chemical compositions have been described in the prior art, but such glasses present significant disadvantages in manufacturing and / or use. In particular, many glasses contain a significant proportion of fluorides and / or Li ₂ O, which very easily evaporates during the melting and fusing process, thereby complicating the exact establishment of the glass composition.

Chemically inert barium-free dental glass for use as filler in composites is the subject of DE 198 49 388 A1. In the case of low index glass, the glass presented here necessarily contains a proportion of ZnO and F. The proportion of F can cause a reaction with the resin matrix, which in turn can be important for its polymerization behavior. In addition, the SiO ₂ ratio of 20-45% by weight restricts the described glass to contain sufficient radiopaque and F. In particular, for low ZnO and ZrO ₂ contents, the addition of up to 27% by weight of SrO is recommended.

WO2005 / 060921 A1 describes glass fillers which are particularly suitable for dental composites. It contains 9-20 mol% of alkali metal oxide. The purpose in this specification is to provide glass particles having a lower concentration of alkali metal ions at the edge of the particles than at their center. This means that the glasses described have intentional chemical instability, or otherwise this concentration behavior cannot be achieved. It can be assumed that essentially low chemical stability is achieved by the mentioned proportion of the alkali metals in the initial glass.

Alkali metal silicate glasses that act as fillers for dental materials are described in EP 0885606 B1. In glass with a high SiO ₂ content, the Al ₂ O ₃ ratio of at least 5% by weight increases the viscosity, resulting in very high melting temperatures. Sodium oxide and potassium oxide are included as essential components. In addition, the glass does not contain a substance which imparts radiopacity.

DE 4443173 A1 comprises a barium-free glass of high zirconium content with a ZrO ₂ content higher than 12% by weight and other oxides. Such fillers are particularly too reactive for current dental compositions based on acrylates which can cause uncontrolled curing, for example, overly rapidly. Zirconium oxide in this amount tends to devitrification. This possibly leads to phase separation with nucleation and subsequent crystallization. In addition, such glass can be made with a high alkali metal content, thereby ensuring that the melting temperature, which makes melting aggregation difficult, is not too high. However, in the end, such high amounts of alkali metal are detrimental to the chemical stability of the glass.

DE 199 45 517 A1 likewise describes glass of high zirconium content which presents the same problems as the glass in the above specification in application in the dental field.

DE 10 2005 051 387 B3 is a dental glass which is radiopaque and magnesium alumino having a high content of La ₂ O ₃ and / or Y ₂ O ₃ and also WO ₃ and ZrO ₂ to achieve a refractive index of 1.50 to 1.549. Silicate glass is described. Such glass does not contain barium, strontium and alkali metal oxides. In view of the high magnesium oxide content of this glass, it has a tendency for phase separation. Another disadvantage is the high crystallization sensitivity due to the content of WO ₃ and ZrO ₂ . This content further raises the melting temperature. La ₂ O ₃ is a very expensive raw material and should therefore be avoided.

DE 10 2009 008 951 A1 discloses its use as radiopaque, barium-free glass and dental glass which contain essentially zirconium oxide. In order to achieve a narrow refractive index range of 1.518 to 1.533, ZrO ₂ is used together with Cs ₂ O and / or La ₂ O ₃ . In order for these glasses to melt, a high K ₂ O ratio is also required. Likewise, here, the problem with such glass is the tendency of crystallization combined with the relatively high melting temperature and raw material cost caused by the La ₂ O ₃ used. Glass having a low refractive index is not described in the prior art.

DE 10 2011 084 501 B3 discloses barium-free, radiopaque glass with refractive indices of 1.50 to 1.58. The glass is based on a combination of SrO and La ₂ O ₃ and ZrO ₂ as radiopaque. In addition, Cs ₂ O may be added to increase radiopacity. The advantages of these glasses are their high melting temperature and crystallization tendency. La ₂ O ₃ described above is very expensive.

JP 2004-002062 A is a glass substrate for flat screens. The glasses disclosed other than SrO mainly contain BaO and also high proportions of Al ₂ O ₃ and MgO. Al ₂ O ₃ , SrO, BaO and MgO components are needed as network transformers to ensure the meltability of the glass. Such glasses are also not considered to be used as dental glass because they lack a considerable amount of radiopacity required. Separately, the content of Al ₂ O ₃ has a high SiO _{2 -} and to increase the viscosity of the content of the glass, and thus require a high melting temperature for the purposes of manufacture accordingly. The high content of MgO is a disadvantage in glass for dental applications, which is intended to have a low refractive index in combination with high radiopacity. MgO does not increase the radiopacity to the same extent as other alkaline earth metal oxides CaO, SrO and BaO instead of mainly indicating an increase in the refractive index (n _d ), and thus this provides a desirable balance between low refractive index and high radiopacity. It can be complicated.

A feature shared by all glasses identified in the prior art is that they have low hydrolysis resistance or are too reactive and / or radiopaque, or they contain ingredients that are harmful to health and / or the environment. Many known dental glasses also contain SrO, which significantly increases the melting temperature. In addition to these economic drawbacks, the high SrO ratio makes it difficult to control the crystallization operation in many glass manufacturing processes. Furthermore, using known radiopaque agents used alone or in known combinations (usually in combination with La ₂ O ₃ ), the attainable radiopacity cannot be increased arbitrarily and satisfactorily without too large an increase in refractive index. . Glass having a refractive index greater than 1.65 (as described, for example, in WO 2007/034258 A1) cannot currently be used satisfactorily as dental glass, fillers for polymer-based dental compositions and the like. In addition, a disadvantage of lanthanum oxide is that it is so expensive that it impairs the economics of the glass produced using it.

It is an object of the present invention to provide a relatively low refractive index lead-free, radiopaque glass having improved radiopacity.

In particular, it is also an object of the present invention for a glass system to be capable of producing glass having a refractive index exactly defined within a given refractive index range, and more easily improved radiopacity with respect to the refractive index, for improved easy manufacturing. To provide. The glass is preferably suitable for use in the medical field, in particular in the dental field as dental glass, and as optical glass. It must be reasonably productive and biocompatible, despite being high grade, and also suitable for passive and active dental protection, processability, setting behavior of the surrounding polymer matrix, and also long term stability and strength and Relevant characteristics should be relevant. In order to meet the requirements in modern dental treatment and dental technology, the glasses of the invention must also have at least good hydrolytic stability.

The figure shows:
1 is a correlation between refractive index and relative aluminum equivalent thickness for the examples in Table 1,
FIG. 2 is a correlation between refractive index and relative aluminum equivalent thickness for the Example of Table 1 with advantageous upper and lower limits,
3 is a correlation between refractive index and relative aluminum equivalent thickness for the example of Table G 1500 having advantageous upper and lower limits,
4 is a correlation between refractive index and relative aluminum equivalent thickness for the example of Table G 1515 with advantageous upper and lower limits,
5 is a correlation between refractive index and relative aluminum equivalent thickness for the example of Table G 1525 with advantageous upper and lower limits,
6 is a correlation between refractive index and relative aluminum equivalent thickness for the example of Table G 1550 with advantageous upper and lower limits.

The glass according to the invention in the base matrix should also contain no coloring components such as Fe ₂ O ₃ , CoO, NiO, CuO, etc. in addition to impurities or inflows and / or residual components which are difficult to avoid in industrial production, thereby tooth coloring. It allows for optimal starting pigmentation positioning for possible applications for and / or for optical applications, adaptation of the spectrum of electromagnetic radiation passing through. In addition, the glass should not contain colored particles that cause a second glass phase and / or scatter and similarly alter the perceived color. One or more additional glass phases will lower the resistance of the glass.

This object is achieved by the glass according to the independent claim. Preferred embodiments and applications are apparent from the dependent claims.

In particular, there is provided a radiopaque glass having a refractive index (n _d ) of 1.480 to 1.561 that does not contain PbO other than impurities, which includes (in weight percent based on oxide):

Cs ₂ O is always present as radiopaque in glass. In an advantageous embodiment, this ensures high radiopacity of the glass in combination with one or more additional radiopaque agents. Particularly advantageous variants include Cs ₂ O and at least BaO or SnO ₂ as radiopaque, wherein La ₂ O ₃ may also optionally be included. Advantageous SnO ₂ -containing radiopaque agents optionally include SnO ₂ in addition to Cs ₂ O and BaO with La ₂ O ₃ . Further advantageous embodiments include combinations of Cs ₂ O and La ₂ O ₃ which serve as radiopaque agents, wherein advantageous variants of this embodiment may not contain BaO.

Some advantageous variants of the radiopaque glass mentioned may comprise fluorine (fluorine-containing variants). Component fluorine may be included to better adjust the refractive index depending on the radiopaque agent used. If fluorine is included, the content can advantageously be at least 0.3% by weight, at least 0.5% by weight. The preferred upper limit may be 6% by weight, advantageously 5.5% by weight, preferably 2.5% by weight. Other advantageous variants have a significantly reduced fluorine content in the range of 0 to less than 0.3% by weight, ie such variants may be fluorine deficient (fluorine-deficient variants) or even contain no fluorine ( Fluorine-free variant).

Advantageous fluorine-containing embodiments of the present invention are radiopaque glasses having a refractive index (n _d ) of 1.480 to 1.561, which do not contain PbO other than impurities, which include the following.

For the purposes of the present invention, advantageous sub-modifications of the fluorine-containing variant are possible, namely advantageous SnO ₂ -containing sub-modifications and advantageous SnO ₂ -free sub-modifications. The SnO ₂ in an amount of 15% by weight beneficial SnO _2-contained sub-variant is advantageously greater than 0 - 15% by weight, preferably 0.3 - 15 wt.% Or 0.5 - 15% by weight, more advantageously 1 Include. Another advantageous SnO ₂ content is greater than 4-15 wt%. Alternatively, the fluorine-containing radiopaque glass may advantageously be SnO ₂ -free (SnO ₂ free sub-strain).

Advantageous fluorine-reducing embodiments (fluorine-deficient or fluorine-free variants) of the present invention are radiopaque glasses having a refractive index (n _d ) of 1.480 to 1.561, which do not contain PbO other than impurities only, which is ( In weight percent based on oxide):

For the purposes of the present invention, advantageous sub-modifications of the fluorine-reducing variant are possible, namely advantageous SnO ₂ -containing sub-modifications and advantageous SnO ₂ -free sub-modifications. Advantageous SnO _2-contained sub-variant is advantageously greater than 0 - 15% by weight, preferably 0.3 - 15 wt.% Or 0.5 - 15% by weight, more advantageously from 1 to - a SnO ₂ content of 15% by weight It includes. Another advantageous SnO ₂ content is greater than 4-15 wt%. Alternatively, the fluorine-deficient and / or fluorine-free radiopaque glass may advantageously be SnO ₂ -free (SnO ₂ free sub-modifications).

The glass according to the invention has a refractive index n _d (also referred to as refractive index) of 1.480 to 1.561. Thus, this applies very well to dental polymers and / or acrylate-based resins available within this refractive index range, whereby the aesthetic requirements imposed on polymer-based dental compositions, in particular dental glass / polymer composites, are natural. Is satisfied for appearance.

The glass according to the present invention achieves the properties of lead-containing dental glass associated with the required X-ray absorption without the use of lead or other materials that may be rejected for health reasons. The glass according to the invention does not contain lead. The term "free" in this context means, for example, the absence of such materials other than unavoidable contaminants that may be caused by air pollution and / or impurities in the raw materials used. However, also in particular for dental glass, contamination of the glass with undesired substances generally does not exceed 300 ppm for Fe ₂ O ₃ , preferably 100 ppm or less, and 30 ppm for PbO, As _2. for O ₃ does not exceed 100 ppm about 20 ppm, other impurities about 20 ppm, Sb ₂ O _3. SrO is always closely related to BaO in the raw materials. Depending on the purity of the BaO raw material, up to 0.7% by weight SrO may be present in the glass according to the invention. This limit is encompassed by the phrase "contains no impurities, but only impurities". Of course, the complete absence of the aforementioned unwanted substances from the glass according to the invention is particularly preferred. The SrO component is preferably not actively added to the glass according to the invention.

X-ray absorption and thus radiopacity is advantageously achieved through the combination of radiopaque agents.

According to an advantageous variant of the invention, radiopacity is advantageously controlled by the combination of Cs ₂ O, BaO and / or SnO ₂ , ie, through the presence of two or more of these components, advantageously the presence of these three components. Is achieved through. Unlike the earlier dental glass, which has been attempted to achieve radiopacity through the high content of one superabsorbent component or in combination with La ₂ O ₃ , which is usually possible radiopaque according to this variant of the invention Is achieved by a suitable combination of two or more of these BaO, SnO ₂ and / or Cs ₂ O components effective for radiopacity. In this way it is possible to achieve particularly stringent requirements for the optical properties of the glass and also to achieve very good hydrolysis resistance and / or chemical resistance. A total of at least 8% by weight, more preferably at least 10% by weight, more preferably at least 12% by weight relative to the contents for BaO, SnO ₂ and Cs ₂ O are most preferred. Very few of these components cause insufficient X-ray absorption. The higher the total sum of these radiopaques in the glass, the higher the radiopaque. An advantageous upper limit for the sum of BaO, SnO ₂ and Cs ₂ O is 51% by weight, preferably 49% by weight, more preferably 47% by weight, also preferably 45% by weight, further preferably 43% by weight. Can be.

In addition, with respect to advantageous fluorine-containing variants, the radiopaque glass contains a finite amount of fluorine, which serves to specifically adjust the refractive index of the glass according to the specific amount of radiopaque agent. This corresponds to the effect as a result of using a large amount of radiopaque in glass, while radiopacity is substantially increased, but at the same time the refractive index of the resulting glass is high. Through the addition of fluorine, it is possible to keep the increase in the refractive index within the threshold or even prevent the increase in the refractive index.

The combination of the radiopaque components BaO, Cs ₂ O, and / or SnO ₂ and optionally F has surprisingly proved to be particularly suitable for producing glasses with high radiopacity in the relatively wide refractive index range of 1.480 to 1.561. In the context of the present invention, for this purpose a total of BaO, Cs ₂ O, SnO ₂ and F in weight percent based on oxide is supplied at least 8% by weight or at least 9% by weight, preferably at least 10% by weight. . Advantageously, the total may be at least 11% by weight or at least 12% by weight, some advantageous variants may be at least 13% by weight or 14% by weight, and other advantageous variants may be at least 15% by weight or 16 weight percent or more, or 17 weight percent or greater. The advantageous upper limit of the sum of BaO, Cs ₂ O, SnO ₂ and F is 56% by weight, preferably 54% by weight, more preferably 52% by weight, also preferably 50% by weight, further preferably 48% by weight. May be%. Some advantageous variants may have an upper limit of 42% or 36% or 35% by weight relative to the total. It is generally known that glass with lower refractive index tends to achieve lower radiopacity and thus lower aluminum equivalent thickness than glass with higher refractive index. The reason for this is that only a relatively small amount of radiopaque can be used for low refractive index glass. If the proportion of radiopaque agent is increased, the refractive index will shift to a higher value. Through advantageous combinations of BaO, Cs ₂ O, and SnO ₂ with F in particular, it is possible to change the radiopacity and the corresponding aluminum equivalent thickness to a higher value than the full refractive index range of the present invention. It is possible for a given index of refraction to achieve a substantially higher X-ray visibility value than is possible so far here. It is also possible to specifically adjust the refractive index in radiopaque glass.

Particularly advantageous embodiments of radiopaque glass having an advantageous combination of fluorine and three radiopaque agents include:

In general, the present invention has succeeded in providing a glass system capable of precisely adjusting the refractive index of the glass to specific requirements by changing the proportion of components in the system described above, wherein the glass has improved radiopacity for a given refractive index. This simplifies the production of glass with high radiopacity which is refracted differently.

The following glass components are described for all glasses according to the invention and advantageous variants.

Basically, the glass according to the invention comprises SiO ₂ in a proportion of 35 to 75% by weight as the glass-forming component. The upper limit according to the invention is 75% by weight. Higher content of SiO ₂ can adversely lead to a higher melting temperature, while also the required radiopacity cannot be achieved. In the case of advantageous embodiments, 73% by weight, preferably 70% by weight, more preferably 68.5% or 65% by weight may be selected as the upper limit of SiO ₂ . Some advantageous variants have an SiO ₂ upper limit of 64% by weight, advantageously 61% by weight or 59% by weight or 56% by weight or 53% by weight. According to the invention, the lower limit is 35% by weight. Lower contents may have negative consequences on chemical resistance and devitrification tendency. In the case of advantageous glass compositions the lower limit of SiO ₂ may be 36% by weight, preferably 37% by weight, more preferably 38% by weight and further preferably 39% by weight. Some advantageous variants may comprise at least 40 wt%, preferably at least 42 wt% or at least 45 wt% or at least 47 wt% or at least 50 wt% SiO ₂ . One preferred embodiment of the glass according to the invention envisions an SiO ₂ content of 38 to 70% by weight, more preferably 39 to 70% by weight.

B ₂ O ₃ is provided in the glass according to the invention in an amount of 2 to 16% by weight, advantageously 4 to 15% by weight, preferably 5 to 15% by weight. It may advantageously be provided in the range of 6 to 15% by weight or 7 to 15% by weight. Some advantageous variants include 3 to 14 weight percent of such components. B ₂ O ₃ has a positive effect on glass formation and melting behavior. It also acts as a flux. In addition to the lowering effect on the melting temperature, the use of B ₂ O ₃ simultaneously leads to an improvement in the crystallization stability of the glass according to the invention. Thus, according to the invention, the lower limit is 2% by weight. For certain glasses, 3% or 4% by weight, advantageously 5% by weight, preferably 6% by weight, preferably 7% by weight may also be chosen as an advantageous lower limit for boron oxide. The upper limit for boron oxide according to the invention is 16% by weight, preferably 15% by weight. Higher ratios are not recommended for these systems in order not to impair chemical resistance. At most 14.5% by weight, preferably at most 14% by weight of boron oxide may also be advantageously included. If the content of B ₂ O ₃ is too high, cases of separation in the glass may occur, which in turn exhibits undesirable unevenness of the refractive index and also has side effects on chemical resistance.

The glass according to the invention essentially comprises Al ₂ O ₃ in the range from 0.8 to 7.5% by weight. It may advantageously be present in the range from 0.8 to 6% by weight or from 1 to 7% by weight. Al ₂ O ₃ improves the chemical resistance of the glass. Thus, according to the invention, in the glass it is present at least 0.8% by weight. Aluminum oxide at least 1% by weight, preferably at least 1.2% by weight, may also be used advantageously. However, it should not exceed about 7.5% by weight of Al ₂ O ₃ content so that it is difficult for the glass to melt, especially in high temperature process parts, so that the viscosity of the glass does not increase. In addition, excessively large amounts of aluminum oxide impair the devitrification tendency and also the resistance of the glass to acids. The upper limit of Al ₂ O ₃ is preferably 7% by weight, more preferably virtually only 6.5% or 6% by weight.

Alkali metal oxides from the group of Li ₂ O, Na ₂ O and K ₂ O are needed to allow the glass to melt at all. K ₂ O acts for the adjustment of the melting temperature and at the same time strengthens the glass network. Thus, according to the invention, it is present in the glass composition in a proportion of 0 to 14% by weight, advantageously 0 to 12% by weight, preferably 0 to 10% by weight. For K ₂ O, a range of 0 to 7% by weight is preferred, and a range of 0 to 5% by weight is particularly preferred for some advantageous variants. The upper limit of 14% by weight for K ₂ O according to the present invention should not be exceeded, since the content of alkali metal oxides lowers the chemical resistance. Also advantageously, 12% by weight or 11% by weight, preferably 10% by weight, preferably 7% by weight, preferably 6% by weight may be selected as the upper limit. Particularly advantageous variants include up to 5% by weight, more preferably up to 4% by weight of K ₂ O. For some advantageous variants, the advantageous lower limit for K ₂ O may be 0.5%, 1%, 1.5% or 2% by weight. In addition, embodiments that do not contain K ₂ O are possible for the purposes of the present invention.

Natium ions and lithium ions have a small size that allows for easier leaching out of the glass matrix, thereby reducing chemical resistance, in particular hydrolysis resistance. In one advantageous embodiment of the invention, the radiopaque glass does not contain Na ₂ O and / or Li ₂ O other than impurities.

Impurities may be introduced into the glass by contamination of the raw materials used for glass production and / or by contamination and / or corrosion of the melt aggregates used. Such impurities generally do not exceed a proportion of 0.2% by weight, in particular 0.1% by weight. Of course, this also includes the complete absence of the components discussed. Thus, "component free" means that the glass is essentially free of such components, that is, any such component is present as an impurity even if present in the glass, but it is not added as an individual component to the glass composition. .

The content of barium oxide is 0 to 24% by weight, preferably 0.6 to 24% by weight. The preferred range is 0.8 to 20% by weight, more preferably 1 to 18.5% by weight for some variants. Too high amounts of BaO cause a decrease in chemical resistance. Therefore, the upper limit of 24% by weight should not be exceeded. For some variations it is also possible to select, as upper limit, advantageously 22% by weight, or 21% by weight, more advantageously 20% by weight, preferably 18.5% or 18% by weight. Further advantageous upper limits can be 17%, 15%, 14%, 12% or 10% by weight. In an advantageous variant, there must be at least 0.6 wt.% BaO present in the glass in order to achieve X-ray absorption with other materials. BaO may advantageously be present in the glass at least 0.8% by weight, preferably at least 1% by weight, more preferably at least 1.1% by weight. Some advantageous variants may have a lower limit of BaO of 2%, 4% or 6% by weight. However, BaO-free radiopaque glass variants are also possible in the context of the present invention described below.

Advantageous embodiments of radiopaque glass may not contain BaO. In such glasses, the impermeability can be based only on Cs ₂ O. To produce higher X-ray absorption, La ₂ O ₃ and / or SnO ₂ may advantageously be used in the glass as radiopaque (s) other than the contained Cs ₂ O. Advantageous modifications of the radiopaque glass having a refractive index (n _d ) of 1.480 to 1.561 containing only PbO and BaO other than impurities include (in weight percent based on oxide):

With regard to BaO-free variants, the combination of components Cs ₂ O or Cs ₂ O and La ₂ O ₃ and / or SnO ₂ acting as a radiopaque agent is sufficient to produce the required radiopacity in the desired refractive index range. May be sufficient. For glass in medical applications, especially in the dental field, BaO-free variants are advantageous alternatives to known BaO-containing and / or SrO-containing radiopaque glasses. Advantageously, BaO-free variants also especially have a low fluorine content of less than 2% by weight, preferably less than 1% or less than 0.5% or less than 0.3% by weight. In addition, advantageous BaO-free variants may not contain fluorine.

Cs ₂ O according to the invention is likewise used for achieving X-ray visibility, but at the same time also contributes to improving meltability. According to the invention, Cs ₂ O is present in the glass composition at 1 to 30% by weight, preferably 1 to 28% by weight, more preferably 1.5 to 26% by weight and most preferably 2 to 25% by weight. Alkali metal Cs is more stationary in the glass matrix compared to alkali metals Li, Na, K and Rb. Thus, it leaches less severely, and less chemical resistance is impaired than the alkali metals described above. Because too little Cs ₂ O causes poor X-ray visibility and increased melting temperature, the lower limit according to the invention is 1% by weight. In the case of advantageous glass compositions, the lower limit can also be 1.5% by weight, more advantageously 2% by weight, preferably 2.5% by weight, very preferably 3% by weight. Some advantageous variants may contain at least 5 wt% or at least 6 wt% or at least 7 wt% Cs ₂ O. Another advantageous variant may have a lower limit of 9 wt% or 10 wt% Cs ₂ O. According to the invention, the Cs ₂ O present should be 30% by weight or less, otherwise the chemical resistance is impaired. Advantageously the glass composition contains up to 28 wt% Cs ₂ O, preferably up to 26 wt% Cs ₂ O, more preferably up to 25 wt% or up to 24 wt% Cs ₂ O. Some advantageous variants may contain up to 22 wt%, preferably up to 20 wt% or up to 19 wt% Cs ₂ O.

Advantageously SnO ₂ likewise serves to adjust the X-ray visibility. This contributes to high radiopacity and the refractive index increases less strongly than other radiopaque agents. Such components are present in the glass composition in a proportion of 1 to 15% by weight. Some advantageous variants of the glass according to the invention do not contain SnO ₂ .

In SnO ₂ -containing variants, SnO ₂ is 0.5 to 15% by weight, advantageously 1 to 15% by weight, advantageously 3 to 15% by weight, preferably 4 to 15% by weight, more preferably> 4 It is present in the glass composition in an advantageous proportion of from 15% by weight, very preferably 4 to 12% by weight, particularly preferably 4-10% by weight. Too small amounts of SnO ₂ can lead to poor X-ray visibility, so that these components are at least 0.1% or 0.3% by weight, advantageously at least 0.5% by weight or with respect to advantageous SnO ₂ -containing variants, or It should be present at least 1% by weight. SnO ₂ also improves and ensures chemical resistance of Cs ₂ O-containing glass. In addition, 3% by weight, preferably 4% by weight, more preferably> 4% by weight, may be advantageously provided as the SnO ₂ lower limit. Very high amounts of SnO _{2 lead} to severe devitrification and / or crystallization tendencies. Therefore, the upper limit of 15% by weight should not be exceeded. As an upper limit to be selected there may advantageously be 13% by weight, preferably 12% by weight, more preferably 10% by weight, very preferably also 9% by weight of SnO ₂ . Variants with less SnO ₂ may have an advantageous upper limit of 6% or 3% by weight.

In the context of an advantageous fluorine-containing variant of the invention, the radiopaque glass contains fluorine in a proportion of at least 0.3% by weight, preferably 0.5% by weight. Advantageously up to 8% by weight, preferably up to 5.5% by weight, preferably up to 5% by weight or-in some variants-up to 2.5% by weight of fluorine is present. Some variations have an upper limit for F of 6% or 3% by weight. The advantageous range for F in advantageous embodiments may also be 0.75 to 2.5% by weight, particularly advantageously 0.75 to 2.25% by weight, preferably 1 to 2% by weight. Fluorine is herein recorded in atomic form and referred to as mass in the composition. This serves to adjust the refractive index in interaction with the above-described combination of radiopaque agents and to improve the melting properties of the glass batch by lowering the melting temperature. Thus, it may be included in the composition at least 0.3% by weight, preferably at least 0.5% by weight. In addition to 0.75% by weight, preferably 1% by weight can be selected as an advantageous lower limit. The upper limit of 8% by weight, advantageously 6% by weight, preferably 5.5% by weight, preferably 5% by weight, should not be exceeded, otherwise the component may evaporate during the melting operation and the non-uniformity of the refractive index in the glass Because there can be a distribution. The fluorine may be present in some variants advantageously in proportions of up to 2.5% by weight, preferably up to 2.25% by weight and more preferably up to 2% by weight.

In a fluorine-deficient variant of the invention, less than 0.3% by weight of F is present. The fluorine-free variant does not contain F.

At this point, any of the above-mentioned upper and / or lower limits of one component may be arbitrarily combined with all of the above-mentioned upper and / or lower limits of another component in a manner encompassed by this description and apparent to those skilled in the art. You will know.

In one advantageous embodiment of the glass of the corresponding variant comprising SnO ₂ and F, the molar ratio of SnO ₂ to F is at least 0.4, preferably at least 0.45, more preferably at least 0.49 and very preferably at least 0.5. Is provided. In an advantageous embodiment, the molar ratio of SnO ₂ to F is preferably at most 0.85, preferably at most 0.79, more preferably at most 0.77, further at most 0.75, and also preferably at most 0.72, very preferably at most 0.7. . These measurements make it possible to accurately set the refractive index of the glass in combination with relatively high X-ray absorption. A further advantage is that the correct ratio ensures the meltability of the glass. Too high a value creates a non-uniform melt.

Further, in order to improve the adjustment of refractive index and radiopacity, ie high aluminum equivalent thickness in radiopaque glass, the molar ratio of Cs ₂ O to the above-mentioned impermeable Cs ₂ O, BaO and SnO ₂ is 0.05 or more, preferably Preferably it is at least 0.07, more preferably at least 0.1. It advantageously does not exceed the upper limit of 0.48, preferably 0.45, more preferably 0.41. Too small a ratio results in too low X-ray absorption. Too high a rain reduces chemical resistance.

The radiopaque glass may optionally contain ZrO ₂ in a proportion of 0 to 2% by weight, preferably 0 to 1% by weight. This zirconium content improves mechanical properties, in particular tensile and compressive strengths, and also lowers the brittleness of the glass. However, too high a content can produce glasses that become highly reactive, especially in the environment of dental polymers. Glass, on the other hand, is at least almost usually inert to dental polymers, especially composites, which do not interfere with their polymerization behavior, for example. In one advantageous variant, the glass does not contain zirconium oxide (ZrO ₂ -free).

One advantageous embodiment of the radiopaque glass may include alkaline earth from a limited proportion of CaO and MgO groups. The proportion of CaO may be 0-2 weight percent. MgO is likewise optional and may be present at 0 to 2% by weight. In one particular preferred embodiment, the glass according to the invention contains no MgO other than only impurities. MgO can be disadvantageous for glass in dental applications where a low index of refraction is combined with high radiopacity. MgO does not increase radiopacity to the same extent as other alkyl earth metal oxides CaO, SrO, and BaO, which is much lower than the X-ray absorption edge of MgO, and that of tungsten X-ray tubes used in medical applications. This is because only a slight effect is shown in the part. MgO only increases the refractive index, thereby complicating the balance between low refractive index and high radiopacity.

The glass according to the invention optionally does not contain CeO ₂ and TiO ₂ except only impurities. In view of their absorption in the UV region, CeO ₂ and TiO ₂ shift the UV edges of the glass, which may result in unwanted yellowish coloring. In one preferred embodiment, the glass according to the invention does not contain TiO ₂ .

One particularly preferred embodiment of the glass does not contain TiO ₂ and ZrO ₂ .

Preferably, ZnO and / or WO ₃ and / or Nb ₂ O ₅ and / or HfO ₂ And / or Ta ₂ O ₅ and / or Gd ₂ O ₃ And / or Sc ₂ O ₃ and / or Y ₂ O ₃ and / or Yb ₂ O ₃ may additionally be present at 0 to 2% by weight, either individually or in any combination.

In the context of the present invention, La ₂ O ₃ may advantageously be used in a proportion of 0 to 19% by weight, preferably 0 to 16% by weight or 0 to 15% by weight in order to adjust the desired radiopacity of the glass. . If La ₂ O ₃ is included, it will generally be present in the glass at least 0.1% by weight, preferably at least 0.2% by weight, preferably at least 0.5% or at least 1% by weight. Preferably, the La ₂ O ₃ -containing glass comprises more than 2% by weight of this component. Some advantageous variants have an appropriate lower limit of 4% by weight. The advantageous upper limit of La ₂ O ₃ may be 19% by weight or 18% by weight, preferably 17% by weight or 16% by weight or 15% by weight. Another advantageous variant may have a suitable upper limit for La ₂ O ₃ of 13 wt% or 11 wt% or 10 wt% or 9 wt% or 8 wt% or 7.5 wt% or 6 wt% or 5 wt%.

As an alternative to the La ₂ O ₃ -containing variant, the present invention includes advantageous variants with a significantly reduced content of La ₂ O ₃ . This variant contains up to 2 wt.%, Preferably up to 1.5 wt.% Or up to 1 wt.% La ₂ O ₃ (La ₂ O ₃ -deficient variant). If La ₂ O ₃ is present in this variant, 0.1% by weight may be an advantageous lower limit for it. The limitation on the La ₂ O ₃ content has the beneficial effect of not increasing the refractive index of the glass too much. One preferred embodiment of the glass does not contain _{La 2 O 3 (La 2 O} 3 - containing non-variant). This provides a cost advantage and enables the manufacture of low-index glass with high radiopacity.

Radiopaque glasses for industrial or optical applications are possible, for example, comprising one or more detergents selected from the group of chlorides or sulfates in a proportion of 0 to 2% by weight, advantageously 0 to 1% by weight. SnO ₂ can likewise also be used as possible detergents, such as As ₂ O ₃ and Sb ₂ O ₃ , and also detergents having the advantages for the chlorides and sulfates described above, and contamination by other detergents does not occur in the melt aggregate. This is advantageous when dental glass is likewise produced after industrial glass.

The linear coefficient of thermal expansion α (20-300) of the glass according to the invention, measured at a temperature interval of 20 ° C. to 300 ° C., is preferably less than 7 × 10 ⁻⁶ K ⁻¹ . As a result of the low coefficient of thermal expansion, the glass according to the invention can compensate for the inherent high thermal expansion of the polymer, especially when used as a filler material in the polymer, and thus is well suited to natural dental materials in polymer-based dental compositions. The thermal expansion applied is given.

As previously described, the glasses according to the invention are resistant to chemical attack-ie they are chemically stable. They preferably have a water resistant HGB according to DIN ISO 719, class 2 or better.

Thus, the glass according to the invention is noted for its chemical resistance, which results in a high degree of inertness in combination with the resin matrix and thus the overall long life of the dental composition.

According to a further preferred embodiment of the invention, the glass according to the invention also preferably does not contain other components mentioned in the claims and / or in this detailed description. This means that according to one such embodiment, the glass consists essentially of the above-mentioned components. The expression “substantially made” herein means that other components are present as impurities, but are not intentionally added to the glass composition as individual components.

Nevertheless, the invention also envisions the use of the glass according to the invention as a basis for further glass, wherein up to 5% by weight of further components can be added to the glass according to the invention as described. In this case, the glass consists of the glass described above according to the invention in the range of at least 95% by weight.

Of course, it is also possible to apply the colored appearance of the glass for optical or other industrial applications through the addition of conventional oxides for the purpose. Suitable oxides for coloring the glass are known to those skilled in the art, examples of which include CuO and CoO, which can be added preferably for 0 to 0.5% by weight for this purpose. In addition, the glass may be given a preservative function through the addition of Ag ₂ O, for example from 0 to 3% by weight.

The invention further encompasses a glass powder composed of glass according to the invention, and the use of a radiopaque glass according to the invention as a glass powder. Glass powders are prepared, for example, by the known methods described in DE 41 00 604 C1. The glass powder and / or powder particles according to the invention preferably have an average particle size of at most 50 μm, more preferably at most 20 μm. An average particle size of 0.1 μm can reach the lower limit, but of course smaller particle sizes are also included in the present invention. The glass powders described above can generally serve as starting materials for the use of the glass according to the invention as filler and / or dental glass. The radiopaque glass according to the invention provides advantageous uses in dental glass / polymer dental compositions comprising dental polymers. Dental compositions of this kind are for example dental filling materials, inlays, onlays, materials for dental cements, shapes for crowns and bridges, materials for artificial teeth, and / or prosthetic, conservative and / or Or as other materials for protective dental care.

In one preferred embodiment, the surface of the glass powder, ie the surface of the glass powder particles, is silanized by conventional techniques. Silanation makes it possible to improve the binding of the inorganic filler to the polymer matrix of the polymer-based dental composition.

The initially mentioned object is further achieved by means of a radiopaque glass according to the invention for use as a dental glass and / or for diagnostic purposes in the medical field, more particularly in the dental medical field. Diagnostic purposes include medical applications, examples of which are in contrast media.

The object mentioned earlier is also achieved by the radiopaque glass according to the invention for use as dental glass for treating voids in human and / or animal teeth and / or for dental restoration. Treatment generally includes complete or partial filling of voids, hollows, gaps, and the like in the teeth.

The glass according to the invention can preferably be used as described as dental glass. In this case, it is advantageous if the dental glass is in the form of powder particles. This is further advantageous if it is a component of a polymer-based dental composition comprising a dental polymer and more particularly forming a filler in powder form. The surface of the powder particles is preferably silanized. In one advantageous embodiment, additional components may be miscible with the dental composition in addition to the glass powder, examples of which may further increase radiopacity, barium and / or strontium and / or lithium aluminate glass-ceramic powders. Additives (eg yttrium trifluoride and / or yttrium fluoride), or fillers for adjusting the viscosity (more particularly fumed silica and / or wet-precipitated silica).

Dental glasses are preferably fillers in composites (also for acrylate polymers which require treatment, more particularly for filling dental voids and / or for dental repair, more preferably for fillers which are mainly chemically inert). Application as a filled composite). Likewise, the use of the glass according to the invention as a radiopaque agent in dental compositions, especially polymer-based dental compositions, is within the context of the present invention. The glass according to the invention is a suitable substitute for, for example, expensive crystalline radiopaque agents such as YbF ₃ . The glass according to the invention is also suitable for use as filler in dental cement, for example glass ionomer cement. It is likewise possible for the glass according to the invention to be used as an inert additive in glass ionomer cements. Particular preference is given to being used as an inert additive in polymer-reinforced glass ionomer cements. Polymer-reinforced glass ionomer cements include a class of materials that have been available for the past few years, which represent the cement curing reaction itself, which can take a very long time, but also resins such as the composites described above to initially cure. It also includes a matrix.

Thus, the radiopaque glass according to the invention is preferably used for producing dental glass / polymer composites comprising dental polymers. Dental polymers are preferably acrylates, methacrylates, 2,2-bis [4- (3-methacryloyloxy-2-hydroxypropoxy) phenyl] propane (bis-GMA), triethylene glycol UV-curable resins based on dimethacrylate (TEGDMA or TEGMA, as defined herein), urethane dimethacrylate (UDMA), alkanediol dimethacrylate or cyanoacrylate.

Likewise, the use of the glass according to the invention as an optical component comprising the glass according to the invention is encompassed by the invention. Optical components are understood to be all articles, in particular components, that can be used for optical applications. This may be a part through which light passes. Examples of such parts include support for cover glass and / or lens parts as well as other parts, such as mirrors and glass fibers, for example.

Cover glass is preferably used to protect electronic components. Of course, this also includes optoelectronic components. The cover glass is conventionally present in the form of a glass plate having a parallel planar surface and is preferably installed on the electronic component, thereby protecting it from environmental influences, for example electromagnetic radiation such as light and X-radiation It can pass through and interact with electronic components. However, for certain optoelectronic components, X-radiation can also be harmful. The cover glass made of radiopaque glass according to the invention can thus be used, for example, in the case of X-ray protective glass in medical devices.

A further possible application is the use of the radiopaque glass according to the invention as cover glass and / or substrate glass in display technology for cathode ray tubes (CRT).

Based on these optical properties, the glass according to the invention can likewise be used for optical applications. As it is usually chemically inert, it is suitable for applications as substrate glass and / or cover glass in photovoltaic cells, such as, for example, silicon-based solar cells, coverings of organic solar cells and / or support materials for thin film photovoltaic modules. . X-ray absorption of the glass according to the invention has particular advantages, among other things, in the use of photovoltaic modules in aerospace applications, since these modules can be exposed to certain intensity X-rays outside the Earth's atmosphere. . In addition, the property of high X-ray absorption allows the glass to be used very generally as an X-ray protective glass.

Due to their high temperature stability, the glasses according to the invention are also suitable as lamp glass, in particular for use in halogen lamps and / or fluorescent tubes and related structures. If the mechanism of light generation in the lamp causes X-radiation, a particular advantage of the glass according to the invention is that this radiation can be moved away from the environment. The glass according to the invention can also be used in X-ray tubes.

Vaporization of the glass according to the invention by physical methods and deposition of vaporized glass on the part is additionally included in the invention. Such physical vapor deposition processes, also referred to briefly as PVD processes, are familiar to those skilled in the art and are described in the examples of DE 102 22 964 B4. In this process, the glass according to the invention serves as a target to be vaporized. The glass vapor-coated parts according to the invention can be advantageous from both the chemical resistance of the glass and its X-ray absorption.

In addition, in view of its high stability, the glass according to the invention is likewise suitable as a matrix material for the safe temporary and / or permanent storage of radioactive waste and also for the embedding of radioactive material.

Such glasses also show advantages in applications as container glass or packaging for pharmaceutical products. In view of high stability with respect to the surrounding medium, the interaction with the components can be almost excluded.

Example

The invention is illustrated below with examples that illustrate the teachings of the invention, but is not intended to be limiting.

TABLE 1 Example (AB) in weight%

Table 1 includes examples of radiopaque glasses in the preferred composition range. All data on the composition are listed in weight percent. The glass comprises an advantageous radiopaque combination of Cs ₂ O, BaO and SnO ₂ and an additional defined amount of fluorine. The combination and fluorine mentioned together form an advantageous radiopaque system, in which its refractive index in the range of 1.480 to 1.561 and relative aluminum equivalent thickness in the range from about 120% up to more than about 1400% can be established.

All values for the relative aluminum equivalent thicknesses (ALET, unit%) listed in Table 1 corresponding to X-ray absorption (XRO, unit%) were determined in a method based on DIN ISO 4049. Gray values in the images were measured using image processing software and used to determine X-ray absorption. Table 1 further lists the refractive index (n _d ) and density of the examples.

The glass described in the examples was prepared as follows:

The raw materials for the oxides are weighed and then mixed thoroughly. The glass batch is melted into discrete melt aggregates at about 1580 ° C., then purified and homogenized. At a casting temperature of about 1600 ° C., the glass can be cast and treated as a ribbon or to other desired dimensions. In a solid continuous assembly, the temperature can be reduced to about 100K or more.

For further processing, the cooled glass ribbon could be milled by known methods from DE 41 00 604 C1 to form glass powders having an average particle size of 10 μm or less. Glass properties were determined for glass bulk not milled into powder. The glass has good chemical resistance with respect to water.

The chemical resistance of the variant of the glass according to the invention is further listed in Table 1. As an example for two examples, a hydrolysis resistance grade (HGB) according to DIN ISO 719 is given. However, the glass according to the invention achieves good values for acid resistance according to DIN 12116 and alkali resistance to DIN ISO 695.

Table G1500 below shows glass having a refractive index in the range of 1.50. The value is given in weight percent.

Table G1515 below shows glass having a refractive index in the range of 1.515. The value is given in weight percent.

Table G1525 below shows glass having a refractive index in the range of 1.525. The value is given in weight percent.

Table G1550 below shows glass having a refractive index in the range of 1.550. The value is given in weight percent.

The glasses shown in Tables G 1500, G 1515, G 1525 and G 1550 have been experimentally melted, and thus are completely or at least partly the materials of the invention. Accordingly, the corresponding embodiment is also an embodiment of the present invention.

TABLE 2 Comparative Example by Weight% (VB)

TABLE 3 Comparative Example (mol) in mol%

Tables 2 and 3 list the compositions, refractive indices and relative aluminum equivalent thicknesses in units of% (ie, X-ray absorption, XRO, unit%) of the comparative examples for comparison. Glass is a known dental glass and radiopaque glass and / or filler for use in a dental composition, where radiopacity is in each case various radiopaque systems (individual radiopaque and / or different radiopaque). The use of a combination of tasks).

1 shows in graphical form the advantageous correlation between refractive index and relative aluminum equivalent thickness for Examples AB1 to AB12:

Within the claimed refractive index range of 1.480 to 1.561, the refractive index is assigned to the relative aluminum equivalent thickness ALET in% as can be described as the following function:

Relative ALET (%) = (15480-15900) * n _d- (23015-22695).

According to a first advantageous variant of the invention, a radiopaque glass having a refractive index n _d in the refractive index range of 1.480 to 1.561 is at least a relative relative aluminum equivalent thickness (minimum relative ALET) defined by the following formula: It is advantageous to have aluminum equivalent thickness ALET (%):

Minimum relative ALET (%) = C * n _d -D, where C = 11000 and D = 16160.

It is further added that the radiopaque glass having a refractive index n _d in the refractive index range of 1.480 to 1.561 has a relative aluminum equivalent thickness ALET (%) that is less than or equal to the maximum relative aluminum equivalent thickness (maximum relative ALET) defined by the following equation. Advantageous to:

Maximum relative ALET (%) = A * n _d -B, where A = 11430 and B = 16230.

For radiopaque glass, therefore, advantageously, all refractive indices in the n _d range of 1.480 to 1.561 can be assigned to the interval of relative ALET bounded by maximum relative ALET and minimum relative ALET. Preferred radiopaque glasses with a defined refractive index n _d have a relative ALET which is advantageously in the interval of the relative ALET, which interval can be calculated by the above-described formula.

According to an advantageous first variant, the assigned value (n _d ; relative ALET) establishes two linear equations defining the advantageous upper and lower limits of the relative ALET in the n _d range of 1.480 to 1.561 for the preferred variant of the glass. It is done by 2 shows a graph of linear equations for AB1 to AB15. The graph forms a so-called "enveloping line". In the region between the upper enveloping line (maximum) and the lower enveloping line (minimum), an advantageous range of relative ALET assigned to the n _d range of 1.480 to 1.561 is found in the preferred variant of glass. As can be seen, embodiments are located between "enveloping lines".

According to a second advantage of the invention, in the refractive index range between 1.480 and 1.561, the assignment between the refractive index n _d of the glass and the relative aluminum thickness ALET (%) is made through the description in the following section:

By way of example, this means the following: radiopaque glass having a given composition according to the invention and a refractive index within the n _d range of 1.490 to <1.510 (e.g. n _d = 1.50) provides a relative ALET of at least 260%. (Corresponds to the minimum ALET). At the maximum, the ALET of this glass may preferably be 1000% (corresponding to the maximum ALET). For radiopaque glasses falling within different n _d ranges, other values shown in each case for "minimum ALET" and "maximum ALET" are also valid. Thus, for a relative ALET, "minimum ALET" defines a lower limit and "maximum ALET" defines an upper limit, which is referred to as the defined n _d range.

According to an alternative advantageous variant, in the refractive index range of 1.480 to 1.561, the assignment between the refractive index n _d of the glass and the relative aluminum thickness ALET (%) is made through the description in the following section:

By way of example, this means the following: radiopaque glass having a given composition according to the invention and a refractive index within the n _d range of 1.480 to <1.490 (eg, n _d = 1.485) results in a relative ALET of at least 120%. (Corresponds to the minimum ALET). At the maximum, the ALET of this glass may preferably be 760% (corresponding to the maximum ALET). For radiopaque glasses falling within different n _d ranges, other values shown in each case for "minimum ALET" and "maximum ALET" are also valid. Thus, for a relative ALET, "minimum ALET" defines a lower limit and "maximum ALET" defines an upper limit, which is referred to as the defined n _d range.

For data collection, glass bulks were prepared from the glass compositions of the examples and the relevant parameters were identified: the relative aluminum equivalent thickness (in%) was determined by the technique described above. The refractive index n _d was determined in a known manner. The number of samples was two per example. Each parameter was measured multiple times, and the average value was calculated for refractive index and X-ray absorption. The correlation between the refractive index and radiopaque can be found in the radiopaque glass according to the invention, for example in glass having an advantageous radiopaque system of SnO ₂ , BaO, Cs ₂ O and F as shown in FIG. 1. Can be expressed by linear regression.

For comparison, the refractive index and relative aluminum equivalent thickness are likewise plotted in FIG. 1 for the comparative examples mentioned, which are based on different radiopaque systems. It can be seen that the examples within the claimed refractive index range have higher X-ray absorption than the comparative examples (based on the individual refractive indices). For the same refractive index, the X-ray absorption value achieved in the preferred glass is substantially higher, for example at n _d = 1.548, Example AB1 has a relative ALET of 1240%, while Comparative Example VB1 is only 763. %, Comparative Example VB10 has only 276%, and Comparative Example VB14 has only 190%. Likewise, in the low refractive index range to approximately 1.49, Example AB3 exhibits a relative ALET of 310%, while that of Comparative Example VB19 is only 80%. Thus, the X-ray visibility of preferred glasses in the context of the present invention, and polymer-based dental compositions prepared using the same, is significantly increased. Therefore, for the same thickness, optical parts (eg glass protective parts, etc.) comprising the preferred glass will be made thinner by absorbing more X-radiation than known optical parts for the same X-ray absorption. As such, weight savings can be made thereby.

Especially for glass with a low refractive index, it has been difficult until now to increase radiopacity, possibly only insufficiently, since increasing the proportion of radiopaque increases the refractive index at the same time. to be. With advantageous radiopaque systems comprising SnO ₂ , BaO, Cs ₂ O and F, a significant increase in radiopacity is achieved even at low refractive indices, and at high refractive indices, aluminum equivalent thicknesses are very significant compared to known glass Is improved.

In FIG. 2, Example AB15 associated with the radiopaque component Cs ₂ O, BaO and SnO ₂ shows a similar composition to Example AB7 and similarly high relative ALET, however, a refractive index of 1.504 is shown in Example AB7 (n _d = 1.525). Have a lower refractive index than). This can contribute to the advantageous influence of the fluorine component, which allows the refractive index-in this particular case, to be specially adjusted to be lower. As a result, it is particularly possible to produce glasses with high relative ALET and relatively low refractive index.

A comparison of Examples AB13 and AB14, which can be seen in FIG. 2, has approximately the same refractive index but different relative indexes through the proper selection of radiopaque in a preferred radiopaque system comprising SnO ₂ , BaO, Cs ₂ O and F It is clear that it is possible to produce glass with ALET.

The advantageous formulas, graphs and intervals described above to correlate the refractive index of the glass with the relative aluminum equivalent thickness are thus valid for the embodiments of the invention mentioned in Tables G 1500, G 1515, G 1525 and G 1550. (See Figures 3-6). In this figure, advantageous upper and lower limits ("enveloping lines") appear as in the comparative example for comparison.

The invention can also be further described by the following description:

1. A dental composition or dental material comprising a radiopaque glass according to the invention as a filler for treatment, more particularly for filling voids in human and / or animal teeth and / or for tooth restoration.

2. A glass powder comprising powder particles composed of radiopaque glass according to the invention.

3. The glass powder according to description 2, wherein the surface of the powder particles present is silanized.

4. Fillers for polymer-based dental compositions comprising the glass according to the invention for treatment, more particularly for filling voids in human and / or animal teeth and / or for tooth restoration.

5. A polymer-based dental composition comprising a glass powder consisting of a radiopaque glass according to the invention or a glass according to the invention.

6. A dental glass / polymer composite comprising a glass powder composed of a radiopaque glass according to the invention or a radiopaque glass according to the invention.

7. In description 6, the dental polymer is preferably an acrylate, methacrylate, 2,2-bis [4- (3-methacryloyloxy-2-hydroxypropoxy) phenyl] propane (bis- GMA), triethylene glycol dimethacrylate (TEGDMA or TEGMA, as defined herein), urethane dimethacrylate (UDMA), alkanediol dimethacrylate or cyanoacrylate based UV-curable resins Dental glass / polymer composites.

8. Dental glass / polymer glass ionomer cement comprising a radiopaque glass according to the invention or a glass powder composed of the glass according to the invention.

9. Dental glass for the preparation of dental glass / polymer dental compositions comprising a dental polymer for treatment, more particularly for filling voids in human and / or animal teeth and / or for dental restoration. Use of radiopaque glass according to the invention as a.

10. Use of radiopaque glass according to the invention as glass powder.

11. The use of description 10, wherein the surface of the powder particles present is silanized.

12. Use according to description 10 or 11 in a dental glass / polymer dental composition comprising a dental polymer.

13. as radiopaque agent in polymer-based dental compositions, and / or

As components for optical applications, and / or

As cover glass and / or substrate glass in display technology for cathode ray tubes (CRT), and / or

As cover glass and / or substrate glass in photovoltaic cells, and / or

As lamp glass in an X-ray tube, and / or

As a substance for the embedding of radioactive material

Use of radiopaque glass according to the invention.

14. Contains the following components (in weight percent based on oxides) and preferably 0-19 weight percent La ₂ O ₃ , having a refractive index (n _d ) of 1.480 to 1.561, containing no PbO other than impurities only Radiopaque Glass Made:

15. Radiopaque glass comprising the following components (in weight percent based on oxides), having a refractive index (n _d ) of 1.480 to 1.510, containing no PbO but only impurities:

16. Radiopaque glass comprising the following components (in weight percent based on oxides) having a refractive index (n _d ) of 1.505 to 1.520, containing only PbO other than impurities:

17. Radiopaque glass comprising the following components (in weight percent based on oxides) having a refractive index (n _d ) of 1.519 to 1.542, containing no PbO other than impurities:

18. Radiopaque glass comprising the following components (in weight percent based on oxides) having a refractive index (n _d ) of 1.542 to 1.561, containing only PbO other than impurities:

19. Radiopaque glass comprising the following components (in weight percent based on oxides) having a refractive index (n _d ) of 1.480 to 1.561, containing only PbO and BaO other than impurities:

Using the described radiopaque combinations (SnO ₂ , BaO, Cs ₂ O) and advantageously defined additions of fluorine, it is desirable to formulate glasses with the desired refractive index on the one hand and extremely high X-ray absorption on the other hand. It is possible. According to the invention, it is possible to realize a range of relative aluminum equivalent thicknesses in the refractive index range of 1.480 to 1.561, from about 120% up to more than 1400%, for example up to 1600%.

This example also demonstrates that the refractive index n _d of the glass system according to the invention, in particular in the range of 1.480 to 1.561, can be applied to the intended application without inhibiting the required ALET. As a result, the system can be used not only as a filler, especially in dental compositions, but also in other applications that impose high requirements on factors including purity and / or chemical resistance and temperature stability. Glass systems can be manufactured at an advantageous cost on an industrial scale.

In addition, the glass according to the invention is relatively easy to melt and is thus efficient to manufacture. If a glass system is found in which the individual components change within the stated limits, the refractive index can be adjusted to the requirements for applications such as, for example, dental filler materials-requirements for glass with improved ALET. It is possible. The possible change in refractive index included in the present invention is considerably wide. Such glass systems make it possible in particular for the rational industrial production of glass, especially in the present glass system, since only a defined selection of raw materials needs to be maintained in the material within a range of proportions varying in the amounts described above. Thus, the procedural manner in the case of melting glass in the glass system is also very similar.

Claims (19)

A radiopaque glass having a refractive index (n _d ) of 1.480 to 1.561, containing only PbO other than impurities, wherein the radiopaque glass comprises the following components (in weight percent based on oxide):

The radiopaque glass according to claim 1, which has a refractive index (n _d ) of 1.480 to 1.561, which does not contain PbO except only impurities, wherein the radiopaque comprises the following components (in weight percent based on oxide): Glass:

The radiopaque glass according to claim 1, which has a refractive index (n _d ) of 1.480 to 1.561, which does not contain PbO except only impurities, wherein the radiopaque comprises the following components (in weight percent based on oxide): Glass:

A content according to any one of the preceding claims, wherein the content is F and / or 0-19% by weight, preferably 0-16% by weight, in a proportion of at most 5.5% by weight, preferably at most 2.5% by weight. A radiopaque glass comprising La ₂ O ₃ and / or B ₂ O ₃ in an amount of 5-15% by weight. The radiopaque glass according to claim 1 or 2, comprising the following components (in weight percent based on oxide):

The sum of the proportions of BaO and Cs ₂ O and SnO ₂ and F (in weight percent based on oxide) is ≧ 12%, preferably ≧ 14%, More preferably ≧ 17%. The molar ratio of SnO _{2 to} F is 0.4 or more, preferably 0.45 or more, more preferably 0.49 or more, very preferably 0.5 or more and / or 0.85 or less. , Preferably 0.79 or less, even more preferably 0.77 or less, still more preferably 0.75 or less, very preferably 0.72 or less, even more preferably 0.7 or less. 8. The method of claim 1, wherein Cs ₂ O + BaO + SnO ₂ The molar ratio of Cs ₂ O to the sum of is at least 0.05, preferably at least 0.07, more preferably at least 0.1 and / or at most 0.48, preferably at most 0.45, more preferably at most 0.41. The radiopaque glass according to claim 1, further comprising one or more of the following components (in weight percent based on oxide):

10. The method according to any one of the preceding claims, wherein the glass, other than impurities only, is Na ₂ O and / or Li ₂ O and / or MgO and / or CeO ₂ and / or TiO ₂ and / or La ₂ O ₃ and Radiopaque glass containing no ZrO ₂ . The glass of claim 1, wherein the glass having a refractive index n _{d in} the refractive index range of 1.480 to 1.561 is greater than the minimum relative aluminum equivalent thickness (minimum relative ALET) determined by the following equation. Radiopaque glass with or without relative aluminum equivalent thickness ALET (%):
Minimum relative ALET (%) = C * n _d -D, where C = 11000 and D = 16160. 12. The glass of claim 11 wherein the glass having a refractive index n _d in the refractive index range of 1.480 to 1.561 is less than or equal to the maximum relative aluminum equivalent thickness (maximum relative ALET) determined by the following equation: Radiopaque glass with (%):
Maximum relative ALET (%) = A * n _d -B, where A = 11430 and B = 16230. 11. The radiation according to any one of the preceding claims, wherein in the refractive index range of 1.480 to 1.561, the assigned value between the refractive index n _d of the glass and the relative aluminum equivalent thickness ALET (%) is shown in the table below. Impermeable glass:

11. The radiation according to any one of the preceding claims, wherein in the refractive index range of 1.480 to 1.561, the assigned value between the refractive index n _d of the glass and the relative aluminum equivalent thickness ALET (%) is shown in the table below. Impermeable glass:

A radiopaque glass made of the glass according to any one of claims 1 to 14, in the range of at least 95% (wt% based on oxide). 16. Radiopaque glass according to any one of the preceding claims for use as a dental glass and / or for diagnostic purposes in the medical field, in particular in the dental medical field. The radiopaque glass according to claim 1, for use as a dental glass for treatment, in particular for filling voids in human and / or animal teeth and / or for dental restoration. . 18. The dental glass according to claim 16 or 17, wherein the surface of the dental glass is preferably in the form of silanized powder particles, more particularly in the form of fillers of filler composites or fillers or inert additives in dental cement. A radiopaque glass which is part of a polymer-based dental composition comprising a dental polymer in a furnace, preferably in the form of an inert additive in a polymer-reinforced glass ionomer cement. As radiopaque in polymer-based dental compositions, and / or
As components for optical applications, and / or
As cover glass and / or substrate glass in display technology in the case of cathode ray tubes (CRT), and / or
As cover glass and / or substrate glass in photovoltaic cells, and / or
As a glass in an X-ray tube and / or
As a substance for the embedding of radioactive material
Use of a radiopaque glass according to any one of claims 1 to 15.

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