GB2495587A - X-ray opaque glass - Google Patents

Abstract

An X-ray-opaque glass is disclosed which is free of BaO and PbO except for at most impurities and has a refractive index nd of from 1.50 to 1.58 and a high X-ray opacity with an aluminium equivalent thickness of at least 300%. The glass is based on the system Si02 - Al203 - SrO - R20 with additions of La203 and Zr02. The glass has very good chemical resistance and can be used, in particular, as dental glass or as optical glass.

Description

X-ray-opaque barium-free glass and its use rihon The invention relates tea barium-arid lead-free X-ray-opaque glass and its use.

In the dental sector, polymerbased dental compositions are increasingly being used for tooth restoration. These polymer-based dental compositions usually consist of a matrix of organic resins and various inorganic fiflers. The inorganic fiflers consist predominantly of powders of glasses, (glass-)ceramics, silica or other crystalline materials (e.g. YbF3), sot-gel materials or Aerosils and are added as filler material to the polymer-based composition.

The use of polymer-based dental compositions seeks to avoid possible harmful secondary effects of amalgam and also to achieve an improved aesthetic irnpession. Depending on the choice of the polymer-based dental compositions, they can be used for various tooth restoration measures, for example for tootfi fillings and also for fixtures such as crowns, bridges and inlays, onlays, etc. The filler material as such is intended to minimize the shrinkage caused by polymerization of the resin, matrix during curing. If, for example there is a strong adhesion between tooth wall and filling, an excessively great polymerization shrinkage can lead to fracture Of the tooth walt. If the adhesion is insufficient, an excessively great polymerization shrinkage can bring about formtion of peripheral cracks between tooth wall and filling, which can promote secondary caries. In addition, the fillers have to meet particular physical and chemical requirements: The filler material has to be processed to produce very fine powders.. The finer the powder, the more homogeneous is the appearanceof the filling. At the same time the polishabiUty of the filling is improved, whch leads, by reducing the area exposed to attack, to improved abrasion resistance and thus to greater durability of the filling. For the powders to be able to be processed readily, it is also desk-able for the powcers not to agglomerate. This undesirable effect occurs, in particular, in the case of finer materials which have been produced by means of sol-gsl processes -Furthermore, it is advantageous for the filler to be coated with a functionalized silane since this makes formulation of the dental composition easier and improves the mechanical properfies. In this case, it is usually primarily the surfaces of the filler particles which are at least partly coated with the functionalized silane.

In addition, the polymer-based dental composition in its totality and thus also the filler should be matched as well as possible to the natural tooth material n terms of their refractive index and colour so that they are ideally virtually indistinguishable from the surrounding healthy tooth material. A very small çartkle size of the pulverized filler likewise plays a role foi this aesthetic criterion.

It is also important that the thermal expansion of the total system composed of polymer-based dental composition and the glass material present therein as filler is matched to that of the natural tooth material in the use range, i.e. usually from -30 °C tQ +70 °C, in order to ensure a sufficient thermal shock resistance of the tooth restoration measure. An excessively large temperature change can also result in cracks being formed between the polymer-based dental compositions and the surrounding tooth material, which can in turn represent preferential Øoints of attack for secondary caries. In general; fillers having a very.low coefficient of thermal expansion are used in order to compensate for the large thermal expansion of the resin matrix.

Good chemical resistance of the fillers towards acids, alkalis and waterand also good mechanical stability under load, e.g. due to chewing motion, can also contribute to a long life ot the tooth restoration measures. The fillers should likewise be resistant to treatment of the teeth with fluoride.

For the treatment of patients, it is also absolutely necessary for tooth restoration measures to be visible in an X-ray image, Since the resin matrix is generally invisible in the X-ray image, the fillers have to provide the necessary X-ray absorption. A filler of this type which absorbs X-radiation sufficiently is referred to as X-ray-opaque. Constituents of the filler, for example particular components of a glass, or additives are generally responsible for the X-ray opacity. Such additives are also referred to as X-ray opacifiers. A widely used X-ray opacifier is YbF3, Which can be added in crystalline, milled form.

The X-ray opacity of dental glasses or materials is reported according to DIN iSO 4049 relative to the X-ray absorption of aluminium as aluminium equivalent thickness (ALET). An ALET of 200% thus means that a glass plate having parallel surfaces and a thickness. of 2 mm produces about the same X-ray attenuation as an aluminium plate having a thickness of 4 mm. Analogously, an ALET.&f 500% means that a glass plate having parallel surfaces arid a thickness of 2 mm produces about the same X-ray attenuation as an aluminium plate having a thickness of 10 mm, Since the polymer-based dental composition is in use usually introduced into cavities from cartridges and modelled in the cavities, it should frequently be thixotropic in the uncured state. This means that its viscosity decreases on application of pressure, while it is dimehsiona.lly stable without the action of pressure.

Among polymerbased dental compositions, a further distinction should be made between dental cements and composites. In the case of dental cements, for example also referred to as glass ionomer cements, the chemical reaction of the fillers with the organic matnx leads to curing of the dental composition as a result of which the reactivity of the fUJers influences the curing properties of the dental composition and thus its processabiflty. A setting process which can be preceded by free-radical surface curing, for ox ample under the action of UV tight, is often involved here. The glass. can serve as a filler which triggers the chemical reaction or participates therein, or. else as inert particulate, material which does not participate in the reaction. The chemical reaction is then brought about by further fillers which are likewise present in the glass ionomer cement.

On the other hand, composites, also known as filling composites, contain further chemically largely inert fillers since their curing behaviour is determined by constituents of the resin matrix ftself and thus initially and a chemical reaction of the fillers and/or particulate materials is often undesirable here.

Since glasses represent a glass of materials having a variety of properties because of their different compositions, they are frequently used as fillers for poylmer-based dental compositions, Other Uses as dental material, either in pure form or as: component of a mixture, are likewise possible, for example for inlays, ontays, facing material for crowns and bridges, materlal for artificial teeth or other material for prosthetic, preserving and/or preventative tooth treatment.

Such glasses used as dental material are generally referred to as dental glasses.

Apart from the above-described properties of the dental glass, freedom from barium oxide (BaO) because of possible secondary effects which damage health and from the toxic lead oxide (PbO) is also desirable.

Furthermore, it is likewise desirable for the dental glasses to contain zirconium oxide (Zr02) as component. Zr02 is a widespread material in industrial applicaüons of tooth technology and optics. 7r02 is very biocompatible and is insensitive to temperature.fluctuation& It is used for many types of tooth care in the form of crowns, bridges, inlays, movement work and implants.

Dental glasses are thus. particularly high-quality glasses. Such glasses can likewise be used in optical applications in particular when the application profits from the X-ray opacity of The glass. Since the X-ray opacity means that the Qlass absorbs electromagnetic radiation in the region of the X-ray spectrum, such glasses are at the same time filters for X-radiation. Sensitive electronic components can be damaged by X-radiation. In the case of electronic image sensors, passage of an X-ray quantum can, for example, damage the corresponding region of the sensor or lead to an undesirable sensor signal which can be perceived, for example, as interference.in the image and/or noise pixels.

It is therefore necessary or at least advantageous in particular applications to protect the electronic components from X-radiation by filtering this out from the.

spectrum of the incident radiation by means of appropriate glasses.

Numerous dental glasses and other optical glasses having a sin, liar optical position or comparable chemical composition have been described in the prior art, but these glasses have considerable disadvantages in production andlor use. In particular, many of the glasses contain relatively large proportions of fluorides and/or Li20 which vaporize very easily during melting and rernelting, as a result of which precise setting of the glass composition i made difficult, US 5,976,999 and US 5827,790 relate to glass-like ceramic compositions in, inter alia, uses as dental porcelains. GaO and Li20 are necessarily present in proportions of at least 0.5% by weight and 0.1% by weight, respectively. Apart from the two main components from the group consisting of Zr02, Sn02 and Ti02, CaO in an amount of at least 0.5% by weight appears to be indispensible ther&n. These components result in an increased refractive index 11d and only a low X-ray opacity. The glasses of these two documents also necessarily contain at Feast 10% by weight of B203. The relatively high proportion of B203 in combination with the. alkali metal contents of at least 5% by weight, or at Feast 10% byweight leads to the chemical resistance qf the glass being unacceptably impaired and they are therefore unsuitable for dental glasses.

Chemically inert dental glasses for use as filler in composites are the subject matter of DE 198 49 388 Al. The glasses proposed there necessarily contain appreciable proportions of ZnO and F. The Fatter can lead to reactions with the resin matrix, which can in turn have effects on the polymerization behaviour thereof. In addition, the Sb2 content is limited to 20 -45% by weight, and therefore sufficient X-ray opabifiers and F can be present in the glass described.

WO 20051060921 Al describes a glass filter which is, in particular, said to be suitable for dental composites. This contains from 9 to 20 rno!% of alkali metal oxides. The objective of this document is to provide glass particles whose alkali metal ion concentration at the periphery of the particles is lower than in the middle thereof. This means that the glasses described cannot be chemi.cafly resistant since otherwise this concentration behaviour would not be able to be achieved It can be assyrned that the low chemical resistance required is achieved by means of the cited proportions of the alkali mets in the starting glass.

An alkali metal silicate glass which serves as filler for dental material is described in EP 0885606 Bi. The A1203 content of at Feast 5% by weight increases the viscosity in the glass having a high Si02 content and therefore leads to very high melting temperatures. Furthermore, the glasses necessarily contain fluorine. However, fluorides tend to vaporize easily during melting of the glass, which makes precise setting of the glass composition difficult and leads to inhomogeneity. In addition., the proportion of the component CaO, which in this system gives the glass its X-ray opacity, is from 0.5 to 3% by weight and therefore too low to achieve the required X-ray opacity with an ALET of at least 300%.

DE 4443173 Al concerns high-zirconiUm glass having a Zr02 content of more than 12% by weight and containing other oxides. Such fillers are. too reactive, in particular for very modern dental compositions based on epoxy which can cure too quickly and in an uncontrolled mannert Zirconium oxide in this amount tends to lead to devitrificaijon, It brings about phase separation., possibly with nucleation and subsequent crystallization. In addition, such glasses can only be produced, with high alkali metal contents in order to ensure a melting temperature which is not too high and would overstress the melting apparatuses.

However, such high alkali metal contents cad to a disadvantageously tow chemical resistance of the glasses.

DE 1,9945 517 Al likewise describes a high-zirconium glass which in appi'ications in the dental sector leads to the same prcblems as those associated with the glasses of the previously mentioned document.

JP 2004-002062 A discloses a giass substrate for flat screen displays.. The glasses disclosed contan SrO together w!th predominantly BaO and high proportions of A1203 and MgO. The components A1203, SrO, GaO and MgO are required as network transformers in oderto ensure'fus'ibility of the glass. These glasses, too, do not come into consideration for use as dental glasses because they can contain BaO or in the]ow-BaO variants do not have anywhere near the required X-ray opacity. Apart from this, the A1203 content leads to the viscosity of the high-S102 glass being increased and high melting temperatures therefore being required for production. High contents of MgO are disadvantageous in glasses for dental applications, which should have low refractive indices and at the same time high X-ray opacity. MgO does not increase the X-ray opacity to the same extent as the other alkaline earth metal oxides CaO, SrO and BaO.,,but makes Its presence known mainly in an increase in the refractive index nd'and canthus make ft difficult to achieve thedesired balance between low refractive ix and high X-ray opacity.

All the glasses mentioned in the prior art either have Ut, weatheting resIstance or are too: reactive and/br are' not)(-ray opaque or cqntairt componsits which damae'the:environrnent and/or health, it is an. object of the invention: tc: wovkle a barium-andl lead-fS:X-my-opaqtze glasshavfra relilively low reftatt'e Index; no of ftwn. t,50 to 1.58. The giiss' shopS be suitable as dental 9lass and as optical glass. It:should be lne)qsnsive to prSuce and nevertheless be of high qualitp and' compatible to:ffl hUman body and also be suitable før passive and active tooth protection and have advantageous properties' in respect of processábility, bonding behaviouy of surrounding polymer matrices and also tong-term stability and strength. to meet the requirements in modern tooth treatment and dental technology3 the glass according to the inventiop also' has to have eceIlent chemical reals a"e Furthermore, the base rna$x of the glass of the lnvenhion shouid, apart front at the: most irnpurities be free f: colour-imparting,pieia sS' as Fe CoO, P4101 GuO e, In order jo'ajlow'an optimal qolouc stwting point or possible matching to the tooth, øoloqr' and/or In H,:' case of opflcS appliatlon$ the ttansmisslOñ spect ni 0 the *cL,, agnetic radlatløn, In addjtion ft shoi Id be free Of a second glass phase, and/or cótour-lrnpatting particles thIch leadl to scattering and likewise altet the colour impffission. One or more further glass phases would reduce the stability Of the glasses.

The object is achieved by' the glass according to the independent claims.

Preferred embodiments and uses can be derived, from the dependent claims.

The glass of the invention has a refractive index nd of from 150 to 1.58. It is therefore matched very well to the available dental polymers and/or epoxy resins in this refractive index range, as a result of which it satisfies the aesthetic requirements in terms of a natural appearance required of a dental glass-polymer composite very well.

The glass of the invention achieves the properties of barium-and/or lead-containing dental glasses in respect of the X-ray absorption required without use of barium and lead and advantageously other substances which are problematical in terms of health Here, the expression "free of" means absence of these substances except for at most unavoidable contamination which can, for example, be caused by air pollution and/or impurities in raw materials used.

However, even contamination of the glass wth the undesirable materials must generally not exceed 100 ppm1 preferably not mpre than 50 ppm in the case of Fe203, 30 ppm iri the case of PbO, 5 ppm in the case of As2O3 20 ppm in the case of 8b203 and 100 ppm for others, BaO is always closely associated with the SrO in the raw material. Depending on the purity of the SrO raw materl, up to 0.37% by weight BaO can be present in the glass of the invention. These limits are encompassed by th.e formulation "free of.... except for at most impurities'.

Naturally, complete absence of the abovernentioned undesirable substances i,n the glass of the invention is particularly preferred.

The X-ray absorption and thus the X-ray opacity is, according to the invention, achieved mainly by means of the content of SrO and the further components Cs20 and/or La203 and/or Sn02 and/or 7r02, which are present in a combined amount of 10% by weight or more in the glass of the invention. In contrast to earlier dental glasses which attempted to achieve the X-ray opacity by means of the high content of an ideally highly absorbing component, the X-ray opacity according to the invention i preferably achieved by the suitable combination of these components which are effective for X-ray opacity. In this way, the parficularly strict demands made of the optical properties of the glass and also -la-the very good chemical resistance can be achieved. A total content of SrO and the further components Cs20 and/or La203 and/or 8n02 and/or Zr02 is preferably at Feast 11% by weight, in particular 12% by weight, particu'arly preferably at least 15% byweight.

SrQ is always present in the glass of the invention. Its content is from 4 to 17% by weight. Preference is given to the range from 4to 16% by weight, particularly preferably from 5 to 15% by weight, veryparti.cularly preferably frorr 6 to 14% by weight. In combinafiort with other X-rny opacifiers, SrO ensures, according to the invention, the good X-ray opacity of the glass. Although the X4ay absorption spectrum of SrO in glasses in the range of conventional tungsten X-ray tubes in the region of an operating voltage of 65 keV i suboptirnal, it has surprisingly been found that very good X-ray opacities can be achieved by the combination with the other substances described herein.

The glass of the invention has, inter alia as a result of these measures, an aluminium equivalent thickness ALET) of at least 300%, preferably at least 350%, particularly preferably at least 390%. This means that a glass plate composed of the glass of the invention and having parallel surfaces and a thickness of 2 mm brings about at least the same X-ray attenuation as an aluminium plate having a thickness ef 6 mm; As base component, the glass of the invention contains 8i02 in a proportion of frcm 55 to 75% by wght as glass-forming component. Higher contents of 3i02 can lead to disadvantageously high melting temperatures, while, in addition, the required X-ray opacity cannot be achieved. Lower contents.can have an adverse effect Gil the chemical resistance. A preferred embodiment of the glass of the invention provides for a content of from 56 to 74% by weight and parficularly preferably from 59 to 70% by weight of Si02. 11 -

B203, Is only optionally provided for in the glass of the Invention, It can be present In tht range from 0 to 9% by weigifl. B203 serves as' flw. Apart from the effect of lowering the rrelting temperature, the use of BO simultaneously teaS to an rnprvemen! in the cys*1Kzation stability of the 9lss, of tt!e invention.

Proportions of more than about % by weight ø$" not recommended In this system. in. order not to put thS very good, chemical retance at tin, B203 Is fS' used in a proportion gt from 10 tQ 7% by weight' and. particularly: prefe,*Wfcrn O:'to 4% bywelt If 820a *:P ent glass of'th& inv,on preference ts: given to' Ukvise: Introducing a small pr':': of rnore:than OM% by' weiót, f: alkali metal oxides Into the glass. fr order to avoid undesirable scáttiring at demixed' regionsanatog ous to the Tyndall effect.

In the glass of the inverdiori, AkQa is necessarily present it the range torn OJ to 4% by weight. AlQ, makes, inter aba, good chemical resistance possible.

However, an AbC3 content of about 4% by weight Should not be exceeded,1 so as not, to irtrease the viscosity of the glass, especially in the hot processing' region, to such an extent that the giase is difficult to The upper limit to: the A1203 sontett' is preferably a;s% by weight. partkularly preferably even bnly 3% by weight, very particularly preferably even only % by wól9ht.

Alkali' metal oxides, ean reee the Cbeni',cai resistance of a glass, but: on' the' other hand can be necessary to ena* the glass to be melted at all. Accotding to the invSdkh, the total conje 1 of the alkali metal' *xldes and/or N*20 and/or (2Q is from 0$ to 12%. by weight, preferably from 0.5 to tt% by weight, parflcujaily:preferablyftom 2 to 10% by weight, vety particularly preferablyfrom 3' to 9% by weight. The Innt'tk'n provides for a baLance of these alka'fl mess in the'spedfIàd ranges. In pattkular, alkali metal o4des from the group n&sting of LkOr and/or NazO and/or' tKzO can, in the glasses of the invention, counter demixlng of the glass matrix: and thus undesirable scatterIng analogous tp the Tyndall effect. A total amount' of at' leaSt 0.5% by Weight of the alkali metal oxides is' therefore present itt addition4 the alkali metal oxides togeTher with B203 aid melting of the Qlass at, acceptable temperatures. However. the maximum of 12% by weight of the alkali metal oxides mentioned should not be ex,'led, hi order to be able to achieve the veiy high resistance of the glass of the iflverflipn.

Speciflciøy, the onteflt. Of theSe alkali metal o4des Is, accoPding to the iIwentlor (ram 0 to 2% by weight of Li20, pre. ,ably' fn,m 0 tb t% by eigh patticula?Jy'preferab(y t-on üio {%: by weight The wry' low proportions of LkP help açh4$, the' very good S$miôat resistance. For This reason, a vwy partiQujarly preferred glass IS also free of lkQ except r,,most impurities.

The coAtent:of'Na20 can be higher than that of LiO. According to the inveq1ion N$aQ,s'present in art amount of from 0 to 7%by *ig, preferably from 0, to'5% by weight and particularly pie" rably from 0 to 4%: by weight and very'particularly preferabI from 0 to 3% by'weight.

1(20 tan. be present in an amount of from 0 to % by weight in the glass of the invention. Preference s given' to. the range from 0 to:8% by weight, pavttt,arly prefeçbly from 0 to 7% by wei9ht and very particularly prieferably'from 0 to 6% by weight U2O Na20 and,K20 can In partioular co"ftibute to beflqrrpefting: of an $i'and,ZtOrcontaining glassb Cs2O i&e"s corfl*s to irnpI3ving the' fUsJbilfty but. accorthn to the lpveniionatthe sarnetbie serves'to increasethe X-ray opadtyandtosetthe refractive Index' in syuergy with the other eornponems. According to the invention, Cs20 is present h' an amount of from, p. to 15% by weight preferabJy from 1 to 14% by weight and particularly preferably from 2 to 13% by weIght and very pau'ticulatly preferably' from 3 to 12% by weight, in a glass according to the invention. The alkali metaL Os' is less mobile in a glass matrix compared to the alkali metals Li. Na, K and Rb. It is therefore leached out to a lesser extent' and -13 -, therefore leads to a lesser deterioration in the chemical resistance than the aboverrentloned alkali metals.

The glass of the invention can contain a!i$d proportion of alkalfrte earth metals fmm the group consisting of CaO a!'d MgO. The proportion. of GaO is from 0 to 11% by weightA preferably from. tp 10% byweight and patticulady :pçefW from 0 to 8% by weight and ns preferably from 01*7% Py weght.

MgO is hkeiMseoptbnal and can be present &t an amoupt of fEon P to c 3% by weight preferably from Ot.c 21% by Weight and partkulady preferably from tat i%hy weight A very pamculady pre, ernbodimentprovldes férthe glass öt the invention to be free of M9Q except for at most impurities. As indicated above, MgO can be disadvantageous in glasses for dental applications with are Intended to have low refractive indices and at the same time a hrgh X-ray opacity MgO does not increase the X-ray opacity to the same extent as the other alkaline earth metal oxides GaO, SrO and BaO because the X-ray absorption edge of MgO is far below those of the other three and exetclses only a Sniafl Influence in the region of the tungsten X4ay tubes used in the medical sector. MgO would merely Increase the refrattWe Index Ønd thus make II harder to achieve the balance betwec n a low refrabtive Index and high X-ray opacity..

Furthernion, the mass of U invention necessarily tontains Oz a propprtipn offropn I to 11% by it This4rcon1um conterft ktProvesThur,efiajcal properties ip particutar the tent *engt?1I Ethd cornprssive strength, and also reduces the brittleness *fthO*lass. In addition, the Gomponent makes a tilar eprifribution to the X-ray opacity as the proportion of StO in the glass. 1-loWever, obPflehtS Which are too high can lead to the glass being reactive, in pa?ftcuir In the environment of dental pd mars. The glass sh6uld, on the other hand, be at least largely inert towards dental polymers, in particular composites, and, for example, not interfere in the polymerization behaylour thereof. Preference is given a Zr02 content of from 1 to less than 10% by Weight.. particulatly -14 -.

preferably from 2 to 9.5% by weight, very parlEcularly preferably from 2 to 9% by weight.

Since Zr02 is sparingly soluble in silicate glasses and demixing can therefore easily occur, the abovementioned proportion of Zr02 should not be exceeded.

Demixed regions which can be formed in the case of excessively high Zr02 contents., in particular in combination with likewise high proportions of 3i02, act as scattering centres for light passing through in a manner analogous to the Tyndall effect. In the case of dental glasses, these scattering centres can spofi the aesthetic impression, which is why dernixed glasses are generally undesirable in dental applications, and in an optical glass the scattering centres generally have a negative effect on the transmission and demixed glasses are therefore likewise undesirable in most optical applications. In addition, demixed glasses can, owing to the phases of various compositions and thus different leaching properties, lead to a reduction in the resistance.

La203 is present in the glass of the invention ir an amount of from Ito 10% by weight. As indicated, it ensures, optionally with SrO and Zr02 and optionally Cs20 and/or optionally Sn02, the X-ray opacity of the glass. The La203 content is preferably from 2 tO 8% by weight, particularly preferably from 3 to 7% by weight and very particularly preferably from 3 to.6% by weight.

Like 0520, 5n02 can be present in the glass of the invention as optional component in order to achieve a high X-ray opacity with an ALET of at least 300%.. In addition, this compOnent has the advantage that it does not, increase the refractive index to the same extent as La203 and/or Ta205. Sn02 therefore also helps to set the low refractive index of from 1.5 to 158 combined with a high X-ray opacity. It can therefore be present in an amount of from 0 to 4% by weight in the glass. It is preferably present in an amount of from 0 to 3% by weight in a glass according to the invention. -15-

The glass of the invention is optionally free of CeO2 and 1102, except for not more than impurities. Owing to their absorption in the UV range, CeO2 and 1102 shift the UV edge of the glass, so that an undesirable yellowish colouration can be obtained.

En order to achieve a high X-ray opacity and correspondingly: particularly high values for the aluminium equivalent thickness, preferred embodiments of the glass of the invention provide for SrO and Cs20 and La203 and Zr02 and/or Sn02 to be present in a total amount of more. than 18% by weight, preferably more than 20% by weight, particularly preferably more than 21% by weight, very particularly preferably more than ?2% by weiht, in the.glass.

To ensure that the glass does not decompose it can be preferred that the numerical value of the ratio Of the content of SIO2 to Zr02 is at least 65.

particularly preferably more than 7.

W03 and/or Nb205 and/or Hf02 and/or Sc203 and/or Y203 and/or Yb203 can preferably and optionally be additionally present either individually or in any combinations in an amount in each case of from 0 to 3% by weight, and Ta205 can optionally be presen.t n any combination in an amount of from 0 to 5% by weight.

The invention also provides for the glass of the invention to be free of B203 (except for at most unavoidable impurities).

As indicated, the glass. of the invention is free of the undesirable components BaO and PbO (except for at most the impurities described). The addition of other substances which damage the environment and/or health is preferably dispensed with.

To ensure particularly good melting properties of the glass, the invention likewise provides that the sum of the contents of MgO and/or CaO and/or SrO is less than 17% by weight. if the glass is difficult to meft, undue stress is placed on the melting apparatuses and the glass can only be melted with increased difficulty, generally making production no longer economical, The glass transformation temperature T of a glass according to the invention is preferably at least 570°C. The glass thus has a high heat resistance, which makes it suitable for other fields of application, in particular fields of application described below.

The coefficient of linear thermal expansion measured in the temperature range from 20°C to 30000 of the glass of the invention is preferably less than 7'1O K'. The low coefficient of thermal expansion enables the glasses of the invention, especially when used as filler material in polymers, to compensate for the naturally high thermal expansion of the polymers, so that the polymer-containing data composition has a resulting thermal expansion which is better matched to the natural tooth material..

As stated above, the glasses of the invention are particularly resistant to chemical attacks, La they are particulady chemically resistant. They preferably have an acid resistance S in accordance with DIN 121 16 of class 2 or better, an alkali resistance L in accordance with DIN ISO 695 of class 1 and a water resistance HGB in accordance with DIN Iso 719 of class 2 or better. The tests for the alkali resistance L and: acid resistance S are very much more demanding Than the test standards DIN ISO 10629 and ISO 8424 used hitherto so that the glasses of the invention have, in particular, an improved alkali and acid resistance.

The invention likewise Øtovides for the glasses of the invention to have very good resistance to attack by NaF. The test method is explained in more detail below In this text in relation to the examples. This test alms to test the resistance of the glasses to fluorine and/or fluorides. These materials can strongly attack glass, bMt. are often used Jn tooth cteaning mated's and/or for fluoridation and/or strengthening of healthy tooth material by, inter aBa, the dentist The glasses of' the invention, are thus all charaøtertzed by a vefl', 9b0d the mical resistaoce, which leads to a high inertness in r'spet of reaction' with t resin matrix and: thus leads to a,very long J1è Ot the' total 4tcerrpos1tiort a f'rther pieferred ttboøknefl.of the present li.,ntlon, the glass: of the invention is preferably alsa free of other components not mentioned iØ the claIms and/or this description, This' means that In such an embodiment, the glass consists essentially of the specified components. The expressjq consist essentially of means that' other components are' present at most as impurities, but are not deliberately added as individual, components to the glass composition.

However, t' invention also provi es for the gJ3st of the invention tg be' used as a basis for fUrther:aJaUesM which up to 5% by weight. of further components can be added to, the invePtlve glass described. In:suçji a case, the glass.

oon"ists, too ding to * hvefltion. of the glass described, to an e*tøtt of at least95%by. weight ft is of,4urse also possible to ifiodify the colour appearance of the glass y addiIin of oxides customary for this purpose. Oxides' suitable tot:tolourlng glasses'. are known to those skilled in the art mention may be made byway of earnpJe of CuO and CoO which for these purposes can preferably be added in an an)ount of from 0 to 0.5% by weight. In addition, the glass can be given' an antiseptic function by additIons of, for example', Ag20 in an amount of from 0 to 3% by weight.

The invention additionally encompasses glass powders composed of the glasses of the invention. The glass powders are produced by known methods, as described, for example, in DE 41 00 604 Cl. The glass powder according to the invention preferably has an average particle size of up to 50 fun, particularly preferably up to 20 trn. An average particle size of 0.1.tm can be achieved as lower limit, and smaller particle sizes are naturally also encompassed by the invention. The abovementioned glass powder can generally serve as starting material for use of the glasses of the invefltion as fillers and/or dental glasses.

In a preferred embodiment, the surface of the glass powder is silan.ized by customary rnethod& The silanization can improve the bonding of the inorganic fUlersto the polymer matrix of the polymer-based dental composition, The glass of the invention can, as described, preferably be used as dentsl glass.

It is preferably employed as a filler in composites for tooth restoration, particularly preferably for filling materials based on epoxy resin, which require largely chemically inert fUlers, The invention likewise provides for the use of the glass of the invention as X-ray opacifier in dental compositions, in particular polymer-based dental compositions, The glass of the invention is suitable for replacing expensive crystalline X-ray opacifiers such as YbF3. The glass of the invention is likewS suitable for and provided for use as filler in glass ionomer cements. It is Hkewise possible to use the glass of the invention as inert particulate material in glass lonomer cements, Particular preference is given to the use as inert particulate material in poiymer-reinforced glass ionomer cements. Polymer-reinforced glass lonomer cements are a class of materials which have been available for only a few years and which themselves display the curing reaction of a cement, which can take a very long time, but also contain a resin matrix like the above-described composites in order to be initially curable.

Accordingly, the glass of the invention is preferably used for producing a dental glass-polymer composite containing a dental polymer, where the dental polymer is preferably a UV-curable resin based on acr',date, methacrylate, 2r2biS-[4--(3 rnethacryloyloxy-2--hydro/propoxy)-p henyfl-propane (bis-GMA), triethylenglycol-melha.crylate (TEGDMA), urethane methacrylate (UDMA), *alkanediol dimethacrylate-or cyanoacrylate.

The invention lIkewise. encompasses the use of the glass of the invsnflon as optical element containing the glass of the invention, For the purpose of the present invention, optical elements are all objects and in particular components which can be used for optical applications. These ban be components through which light passes. Examples of such components are cover glasses and/or lens elements but also supports for other components such as mirrors and glass fibres.

Cover glasses are preferably used for protecting electronic components. These obviously likewise encompass optoelectronic components. The cpver glasses are usuafly in the form of glass plates having flat parallel surfaces and are preferably installed above. the electronic component so that the latter is protected from environmental influences but electromagnetic radiation such as light can pass through the cover glass and interact with the electronic component.

Examples cf such cover glasses are the inside of optical caps, for the protection of electronic image sensors, covering wafers in wafer Level packaging, cover glasses of photovoltaic cells and protected glasses fOr organic electronics.

Further applications of cover glasses are adequately known to those skilled in the art. Ft is likewise possible for optical functions to be integrated into the cover glass, for example when it is provided at least in regions with optical structures which can preferably have the form of lenses. Cover glasses provided with micro lenses are usually employed as cover glasses of image sensors fbi dEgital cameras, where the micro lenses usually focus light impinging obliquely on the image sensor onto the individual sensor elements (pixels), It is of course also -20 -possible to use the glass of the invention as substrate glass of electronic components, in which case the electronic components are embedded into the substrate glass and/or are applied thereto.

Owing to its optical properties, the glass of the invention can likewise be used for optical applications. Since it is largely chemically inert, it is suitable for uses as substrate glass and/or cpver glass in p.hotovoltaics, for example for covering photovoltaic cells based on silicon, organic photovoltaic cells and/or as support material for thn-filrn photovoltaic modules The X-ray absorption of the glass of the invention has, inter ella, particular advantages in the use of photovbltaic modules in spaceflight applications since these can be subjected to particularly intensive X-radiation outside the earth's atmosphere. In addition, the property of high X-ray absorption allows use quite generally as X-ray protection glass.

The glass of the invention has also found an excellent field of application as cover glass and/or substrate glass of OLEDs because of its properties. For example,. due to its chemical resistance also unwanted interactions between the gass and the OLED substances can be avoided, or at least supressed.

The glass of the invention is also suitable for use as cover glass and/or substrate glass for biochemical applications, in particular for molecular screening methods.

Owing to its high heat resistance, the glass of the invention is also suitable as Famp glass, in particular for use in halogen lamps and/or fluorescent tubes and related constructions. If X-radiatiOn is generated by the mechanisms of light generation in the lamp, it is a particular advantage of the glass of the invention that it can keep this away from the surroundings.

In addition, the invention encompasses vaporization of the glass of the invention by means of physical processes and depositing the vaporized glass on components. Such physical vapour deposition processes (PVD processes for. -21 -

short) are known to those skilled in the art and are described, for example, in DE 102 22 964 B4. In such processes, the glass of the invention serves as target to be vaporized. The components onto which the glass of the invention has been vapour-deposited can profit both from the chemical resistance of the glass and from its X-ray absorption.

It is likewise possible to use the glass of the invention as starting material for glass fibres. Here, the term gla ss fibres encompasses all Pipes of glass fibres, in particular fibres which consist only of a core and core-sheath fibres which have a core and at least one sheath which preferably completely surrounds the core along the outer circumferential surface, The glass of the invention can in this case be used as core glass and/or as sheathing glass. Within the composition range of the glass of the invention, the refractive index nd of the glass can be set so that a core glass according to the invention has a higher refractive index than a sheathing glass according to the invention, so that a step index fibre in which fight conduction occurs very efficiently as a result of total reflection at the interface of core and sheath is obtained. The term likewise encompasses side-emitting fibres as described, for example, in WO. 2009/100834 Al, In addition, the glasses of the invention are likeWise suitable as matrix material for the secure temporary and/or permanent storage of radioactive waste and also for the embedding of radioactive materials because of their high stability and also, if desired, due to their X-ray absorbance..

This glass also displays advantages in use as container glass or for packaging of pharmaceutical products. Owing to the high resisiance to surrounding media, interactions with contents can be virtually ruled out.

Owing to its good chemical resistance, another field of application is, in particular, use of the glass fibres according to the invention as reinforcement in -22 -composites and/or as concrete reinforcement andtor as optical waveguide fibres embedded in concrete.

Table 1 contains examples of glasses in the preferred composition range. All figures in respect of the composition are in per cent by weight.

All values of the ALET were determined by a method based on DIN ISO.4049 but using a digital Xray instrument. The grey values obtained thereby were further processed by means of image analysis software and the X-ray absorption was determined therefrom.

The glasses described in the examples were produced as follows: The raw materials for the oxides are weighed out without refining agents and subsequently mixed well. The glass mix is melted at about 1580°C in a discontinuous melting apparatus, then refined and homogenized. At a casting temperature of about 1600°C, the glass can be. cast and processed as ribbons or other desired dimensions. In a large-volume, continuous apparatus, the temperatures can be reduced by at least about 100 K. For further processing, the cooled glass ribbons were mifled to a glass powder having an average partide size of not more than 10 pm by means of the process known from DE 41 00 604 Ci The glass properties were determined on glass gobs which had not been milled to powders. All glasses display excellent chemical resistance to acids, alkalis, water and fluorine-containing substances such as NaF and NaF/acetic acid.

Table I also shows the refractive indices nj, the gl'ass transition temperature T2 and the coefficients of linear thermal expansion U(20..300) from 20 to 30.0 °C and uio...7o) from -30 to 70 °C. the latter is of particular interest for the use of the -2 glass of the invention as dental glass because the temperature range from -30 to °C can occur in use Also shown is the chemical resistance of the variants of the glass of the invention, which is quantified by the values achieved for the acid, alkah and water resistance. Here, .S. denotes the acid resistance class in accordance with DIN 12116 L denotes the alkali resistance class in accordance with lN ISO 695 and HGB denotes the water resistance class in accordance with DIN ISO 719.

To quantify the exceflent chemidal resistance of the glasses of the invention further, an even stricter test which tests, in particular, the resistance to fluorine and/or fluorides was carried out. The resistance to fluorine-couitaining components as often occur in tooth cleaning materials and serve to fluoridate and/or strengthen healthy tooth material was tested as follows by means of an NaP solution and an NaF/acetic acid solution: production of a composite from 50% of monomer and 50% of sHanized glass powder having an average particle size (d50) of 3pm measured by laser light scattering (CILAS 1064L instrument).

The test specimens are polished on both sides and are exposed to a 0,001 molar NaF solution and a 0.001 molar NaF solution and 4% acetic acid at temperatures of 37°C and 100 °C for sixteen hours, The surface of the polished specimens is examined by means of SEM before and after the resistance test.

Very good specimens displayed no changes. Good spedimens displayed only slight interfacial cracks between the monomer and the glass powder particles.

Poor specimens showed that the glass particles had been leached from the monomer matrix. Owing to the outlay for carrying out this test, the results of this test are not yet available for all variants of the glass according to the invention. 24 -

Air giasses shown in Table 1 have coefficients of thermal expansion a(20.300) in the range from 20 to 300°C of less than 71 O K and are free of BaO wrthin the limits of measurement accuracy of the analysis.

Cc mpared to BaO-c.ontaihing glasses, glasses shown in Table 1 have an X-ray opacity which is at least as good. In the examples presented, values of the ALET of from 399% to 763% are achieved.

The examples also demonstrate that the refractive indices nd of the glass system of the invention can be matched to the application, in particular in the range from.

1.53. to 1.56, without the required ALET suffering. As a result it can advantageously be used as, in particular, fillers in dental compositions but also for other applications which have demanding requirements in respect of, inter alia, the purity and the chemical and heat resistance. It can be produced industrially with adequate efforts.

Compared to the prior art, the glass of the invention has the additional advantage that it combines adaptability of the refractive indices and coefficients of expansion and also a constantly very good chemical stability with fficient X-ray absorption.

The glass of the invention is also comparatively easy to melt and therefore efficient to produce, -25

Table 1

Compositions of the X-ray-opaque giass in % by weight rExamplewo UIII2__ 4j 567 SO1 ________ 676916635 6585L6879 J 6935 6864 6857 B203 ______ _________ ____ pj203 097 -095095173 172 169 4j7_J LNZ0 ____ 114 16Q166 1<40 148 077 144 218 I 217 145 11 co __--__ lull --CaO ___ 684 509 345603 I 518 _510 465 M90 _____ SrO 740 1024 1 1312 742 739 727 719 F--------------r-------------------------------------H-------_____________ La203______ J-479 469 466 48 jLj 470 465 42_____J 809 705 j[7 _447 -3P 347 5n02 ______ 217 ______ ______ ______ ___ 154955 1,55291 155209 154131 153717 153391,53043 ___ 536 521 552 552 SAl 554 f.5.54 aN30711119K1 -478 -_____ 506 Tq [OC] ___ 722 -734 716 706 701 779 S[J L_ ______ I ____ 4 Licass1_--____ ___ ____ 1 tiPiClass1 --I -j 4_ 1 ALEJ3j 427 502 _j_ 49 399 -424 L 469 503 Resistance to-Very Very NaF/acetic add S_L ____ ___ -_____ -26 -Table I (continuation) ExampeNo. 8 9 10 ii 12 13 14 ___ _AQ. 673 - dilL Q]q 5991 8302 B70a_____ ____ ___ _____ -------r --------_----A1203 091 164 086 038 088 089 158 -LiO _____ -_____ ____ -. 0.40 _____ Na20 256 261 241 247 247 248 250 --.--------: I" ---,--------I --._ 1(20 _________ 2.67 1.74 288 4,20 3,84 3:85 4.21 Cs20 ___ 388 79 1095 748 750 753 1138 CaP 170 377 ___ 172j 097 287 SrO 1285 706 1189 1219 1222 1226 678 La203 449 457 422 433 434 435439_J 7r02_______ 759 341 713 731 733 736 321 Sn02 -_____ ______________ 1,55138 1,53004 1,54807 155489 1,54997_1,53781 1,53321 aoatf10SKJ 604 5% 648 1' 672681 r DOilij 5321 583J5 602 607 628 -T _..Q!!LL_Q.A?i..÷ $jClaas] 2....L ____,, 1 1 1 I tr'I 1 I 4 -r T' -t-'-----i-----

-I

HGBçIas4 L 2 --__ -1_ -___ 2 ALEfl%] --593 -546 --§9 683 Resistance to Very Very -Very I -Very NaF/aceie add L..,29pq L____ __ jpp,d laS I (continuation) EEmeNo 15 16 17Th 19' 61 37 _6J 28 _64 006220 6857 8203 2.98 fl i.8 M1JJ.6 7 L0 JQ4O ____ ra2o. 2.5 J2ij.26 K20 ______ 5.48. 2.11 2.12 3.11 1.1 Cs20 1137 1143 1069 515 6041 CaO ____ 2.87 2.88 2.13 3.31 4.65 TMgO -__ SrO 673 651 683 1072 719 44° 4.48 ________.I?l TL±7 1Sn02 _____ _____________ ______ ____ [flc _______ 1,55480 1,53199 1,52969 1,5531641,52997 [1O LL...4..J.64. 5.63 554 ___ 5.56 6.SYJ 666 679 SIC!assl... 1... . ___.... ..i ___ L1P±!li.. ____ -4. -J PicJ!i __...

ALET [%} -628 638 -617 626 503 Ress1ance to Very Very r Very Very aod L..2c.QJ good -28 -

Claims (8)

1. <claim-text>Claims 1.. X-ray-opaque g1as.SAng arefracthe indèi Rd *f from 1;5Q to tSB and an aluminium equiSent thickness:01 at Ieast 3OG°44 which Is free ofBaQ and PbO cept foitostbpqcftS, comprIsing in 46 byweigt-it.oti an oxide basis $102 55-75 B203 Q9 Mba 0$ -4 1-20 0-2 14*gO 04 1K20 0_v Cs2Q a-is 41T GaO Zc02 1_c1i 1-10 O4 Li2OtNSáO*K*O:Q.512 SlOt Qs2QtLQa* $144 ZC2 10 2. Xqay-opaque glass acqoitling to claIm 1, comprising in % by weight oty an oxide basis SiOz 56-74 BA 0-7 A12Q3 as -44 29 -1120 0-1 NazO 0-4 0-1 Cs20 1-14 $rQ 41B taO 0-10 M40 ZtQi 1c1O La203 2: fi 0-3.</claim-text> <claim-text>L120 t 19a20 +140 Ii $rO*QsO+LaaOs+$nO2+zro'2 3. X-ray-opaque glass according to at least one of the preceding claims, comprising In % by weighton an oxide basis :s02 >59-TO B203 0-4 41203 0.5-2. L120</claim-text> <claim-text>Na20 04 Cs20 3-12 SrO CaO 0-8</claim-text> <claim-text>MO</claim-text> <claim-text>ZrOz 2-g La203 3-6 SnO? 0-3 L120tNa20÷K20 3.9 t 30 StOt Cs20 + La2Oa+ 5fl02 +2r02, »= 15 4. X-ray-opaque glass according ta at least one:Of the preceding disirns, wherein the, surnof the tontents of Sit and CisO and La203ar4 $fl02 and ZrC2:in 4 by weigiton an oxide basts)lsflB%, preferably 2O% patularly prefnbly>Zi Va.t X-rayopaque glass accocdkng, ipat least one ef the precethn c1strns wherein the ratio *fl the contents of Si03.apd 2r02 is such that $1Q2I2rQ2»=6.5, preferably S1O2/ZtO 7..</claim-text> <claim-text>6. X-ray-opaque glass according to at least one of the preceding claims, which additionally comprisesp % by weight on an oxide basis one or mere of the Nb205 0-3 1-1102 0-3 Ta205" t. 5 $0205. G' 3 0-3 Yb205: 0-3 1. X,ray-opaque glass according to at least one of the preceding claims whioh is free of B203 and/or' tjsO and/or fluorides excEpt for$ mosttrce and preferably contains c544 (in% by weight on an oxide basis) of ThOr.ft X-ray-opaque glass according to at least one of the preceding claims having a coefficient of thermal expansion 2O3OO) of less than 71 O K1.9. X-ray-opaque glass. according to at least one of the preceding claims having an acid resistance S in accordance with DIN 12116 of class 2 or better, an aikaH resistance L in accordance with DIN ISO 10695 of class 1 and a water resistance FIGS in accordance with DIN ISO 719 of class 2 or better.10. X-ray opaque glass substantially as described herein.11. Glass consisting to an extent of at least 95% in % by weight on an oxide basi.s of the Xray-opaque glass according to at least one of the preceding claims.12. Glass powder comprising the X-ray-opaque glass according to at least one of the claims itolO.13. Use of an X-ray-opaque glass according to at least one of claims 1 to 11 as dental glass, in particular as a filler in composites for tooth restoration.14.. Use of an X-ray opaque glass according to at least one of cClairns Ito 11 as flUer or inert particulate. material in glass onorner cements preferably as inert particulate material in polymer-reinforced glass ionomer cements.15. Use of a glass accoiding to t least one of claims 1 to 11 as -32 -* -X-ray opacifier in polymer-based dental compositions and/or as -element for optical applications and/or as cover glass and/or substrate glass for electronic components, in particular sepsors, and/or as cover glass and/or substrate glass in display technology and/or as cover glass and/or substrate glass in photovoltaics and/or as cover glass and/or substrate glass for OLEDs and/or as -cover glass and/or substrate glass for biochemical applications and/or as -lamp glass and/or as -target material in PVD processes and/or as -core glass and/or sheathing glass of a glass. fibre and/or as -optical waveguide and/or as material for embedding radioactive rnaterias and/or as -container material for packaging of pharmaceutical products and/or as -reinforcing material in composites in particular in conacte,AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS1. X-ray-opaque glass having a refractive index n of from 1.50 to 1.58 and an aluminium equivalent thickness of at least 300%, which is free of Bab and PbO except for at most impurities of up to lOOppm in the case of BaO and 3oppm in the case of PbO, comprising in % by weight on an oxide basis S102 55 -75 B203 0-9 A1203. 0.5-4 L120.0-2 Na20 0-7 1<20 0-9 Cs20 0-15 SrO 4-17 CaO 0-11 MgO.Zr02 1-CU La203 1-10 Sn02 0-4 L120 + Na20 + 1(20 0.5-12 SrO + Cs20 + La203 + Sn02 + Zr02 »=. 10 * .* * ** * .
2. 2. X-ray-opaque glass according to claim 1, comprising in % by weight on an oxide basis S... * S ** Sb2 56-74 B203 0-7 A1203 0.5 -3.5 Li20 0-1 Na20 0-5 1<20 0-8 0520 1-14 SrO 4-18 CaO 0-10 MgO 0-<2 Zr02 1-<10 La?03 2-8 Sn02 0-3 Li20 + Na20 + K20 0.5-11 SrO + Cs20 + La2Oa + Sn02 + Zr02 »= 11
3. 3. X-ray-opaque glass according to at least one of the preceding claims, comprising in % by weight on an oxide basis Si02 >59 -70 8203 0-4 A(203 0.5-2 Li20 0-<1 Na20 0-3 K20 0-6 Cs20 3-12 SrO 6-14 GaO 0-S MgO 0 -*0* Zr02 2-9 La203 3-6 Sn02 0-3 L120+Na20+K20 3-9 SrO + Cs20 t La203+ SnOz Zr02 »= 15
4. 4. x-ray-opaque g(ass according to at least one of the preceding Sims, wherein the sum of the contents of SrO and Cs20 and La203 and Sn02 and Zr02 (in % by weight on an oxide basis) is >18%.
5. 5. X-ray-opaque glass according to claim 4 wherein the sum of the contents of SrO and Cs20 and La203 and Sn02 and Zr02 (in % by weight on an oxide basis) is> 20%.
6. 6. X-ray-opaque glass according to claim 5 wherein the sum of the contents of SrO and Cs20 and La203 and Sn02 and Zr02 (in % by weight on an oxide basis)is>21%.
7. 7. X-ray-opaque glass according to at least one of the preceding claims, wherein the ratio of the contents of SIC2 and Zr02 is such that: SiO?/Zr02»=6.5.8. x-ray-opaque glass according to claim 7 wherein the ratio of the contents of Si02 and Zr02 is such that: S1O2IZrO2»=7. * S9. x-ray-opaque glass according to at least one of the preceding claims, which 55* additionally comprises in % by weight on art oxide basis one or more of the following Nb205 0-3 1-002 0-3 Ta205 0-5 Sc203 0-3 Y203 0-3 Yb203 0-3 10. X-ray-opaque glass according to at least one of the preceding claims which is free of B203 and/or Li20 andfor fluorides except for at most traces to a level of lOOppm.11. X-ray-opaque glass according to at least one of the preceding claims which contains C 5% (in °Jo by weight on an oxide basis) of ZnO.12. X-ray-opaque glass according to at least one of the preceding claims having a coefficient of thermal expansion a(20-300)Of less than 7106 K1.13. X-ray-opaque glass according to at least one of the preceding claims having an acid, resistance S in accordance with DIN 12116 of class 2 or better, an alkali resistance L in accordance with DIN ISO 10695 of class I and a water resistance HGB in accordance with DIN ISO 119 of class 2 or better. * *14. Glass consisting to an extent of at least 95°fo in % by weight on an oxide basis of the X-ray-opaque glass according to at least one of the preceding *.*fl cIams.15. Glass powder comprising the X-ray-opaque glass according to at least one of the claims ito 13.16. Use of an X-ray-opaque glass according to at least one of claims I to 14 as dental gass.17. Use of an X-ray-opaque glass according to claim 16 as a filler in composites for tooth restoration.18. Use of an X-ray opaque glass according to at least one of claims I to 14 as filler or inert particulate material in glass ionomer cements..19. Use of an X-ray-opaque glass according to claim 18 as inert particulate material in polymer reinforced glass ionomer cements.20. Use of a glass according to at least one of claims ito 14 as -X-ray opacifier in polymer-based dental compositions and/or as -element for optical applications and/or as -cover glass and/or substrate glass for electronic components, in particular sensors, and/or as -cover glass and/or substrate glass in display technology and/or as -cover glass and/or substrate glass in photovoltaics and/or as -cover glass and/or substrate glass for OLEOs andlor as -cover glass and/or substrate glass for biochemical applications and/or as *t.-lamp glass and/or as * -target material in PVD processes and/or as -core glass and/or sheathing glass of a glass fibre andlor as -optical waveguide and/or as 4 p -material for embedding radioactive materials andlor as -container material for packaging of pharmaceutical products andlor as -reinforcing material in compositesand/or as -reinforcing material in concrete. . * **
8. S.... * * ** S.... * . * S*5 * C *5 ** * S S * S</claim-text>