RADIOPAQUE GLASS AND USE THEREOF

Abstract

The invention relates to a radiopaque glass having a refractive index n.sub.d of 1.480 to 1.561, this glass, apart from impurities at most, being free from SrO and PbO. The glass is based on the SiO.sub.2, Al.sub.2O.sub.3 and B.sub.2O.sub.3 system. The radiopacity can be adjusted using Cs.sub.2O in particular in combination with BaO and/or SnO.sub.2 optionally in conjunction with fluorine. The glass may be used in particular as dental glass or as optical glass.

Claims

1. Radiopaque glass, being free from PbO apart from impurities at most, wherein the glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%) which is greater than or equal to a minimum relative aluminium equivalent thickness (min. relative ALET) which is determined by the following equation:
min. relative ALET (%)=C*n.sub.dD, where C=11000 and D=16160.

2. Radiopaque glass according to claim 1, comprising (in wt % based on oxide) TABLE-US-00024 SiO.sub.2 35-75 B.sub.2O.sub.3 2-16 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-14 BaO 0-24 Cs.sub.2O 1-30 SnO.sub.2 0-15 F 0-8 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

3. Radiopaque glass according to claim 2, comprising (in wt % based on oxide) TABLE-US-00025 B.sub.2O.sub.3 4-15 K.sub.2O 0-10 BaO 0.6-24.sup. F 0.3-8.

4. Radiopaque glass according to claim 2, comprising (in wt % based on oxide) TABLE-US-00026 B.sub.2O.sub.3 4-15 K.sub.2O 0-10 BaO 0-24 F .sup.0-<0.3.

5. Radiopaque glass according to claim 2, comprising F with a proportion of not more than 5.5 wt % and/or La.sub.2O.sub.3 with a content of 0-19 wt % and/or B.sub.2O.sub.3 with a content of 5-15 wt %.

6. Radiopaque glass according to claim 5, comprising F with a proportion of not more than 2.5 wt % and/or La.sub.2O.sub.3 with a content of 0-16 wt %.

7. Radiopaque glass according to claim 2, comprising (in wt % based on oxide) TABLE-US-00027 SiO.sub.2 38-70 B.sub.2O.sub.3 6-15 Al.sub.2O.sub.3 1-7 K.sub.2O 0-7 BaO 0.8-20 Cs.sub.2O 1-28 SnO.sub.2 1-15 F 0.75-2.5.

8. Radiopaque glass according to claim 1, comprising BaO, Cs.sub.2O, SnO.sub.2 and/or F, wherein the sum of BaO and Cs.sub.2O and SnO.sub.2 and F (in wt % based on oxide) is 10% and wherein Cs.sub.2O is in the range 1-30 wt %.

9. Radiopaque glass according to claim 1, comprising SnO.sub.2 and F, wherein the molar ratio of SnO.sub.2 to F is 0.4-0.85.

10. Radiopaque glass according to claim 1, comprising Cs.sub.2O, BaO and SnO.sub.2, wherein the molar ratio of Cs.sub.2O to the sum of Cs.sub.2O+BaO+SnO.sub.2 is 0.05-0.48.

11. Radiopaque glass according to claim 1, wherein the glass, apart from impurities at most, is free from one component or more components selected from the group consisting of Na.sub.2O, Li.sub.2O, MgO, CeO.sub.2, TiO.sub.2, La.sub.2O.sub.3 and ZrO.sub.2.

12. Radiopaque glass according to claim 1, wherein the glass has a relative aluminium equivalent thickness ALET (%) which is less than or equal to a maximum relative aluminium equivalent thickness (max. relative ALET) which is determined by the equation:
max. relative ALET (%)=A*n.sub.dB, where A=11430 and B=16230.

13. Radiopaque glass according to claim 1, wherein assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is as follows: TABLE-US-00028 n.sub.d ALET min. ALET max. 1.480 to <1.490 120% 700% 1.490 to <1.510 260% 1000% 1.510 to <1.530 520% 1200% 1.530 to <1.550 780% 1500% 1.550 to 1.561 850% 1600%

14. Radiopaque glass according to claim 1, wherein assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is as follows: TABLE-US-00029 n.sub.d ALET min. ALET max. 1.480 to <1.490 120% 760% 1.490 to <1.500 240% 875% 1.500 to <1.510 360% 990% 1.510 to <1.520 475% 1105% 1.520 to <1.530 590% 1220% 1.530 to <1.540 705% 1335% 1.540 to <1.550 820% 1450% 1.550 to 1.561 935% 1565%

15. A dental glass comprising the radiopaque glass of claim 1.

16. A radiopacifier in a polymer-based dental composition, an element for optical applications, a cover glass and/or substrate glass in display technology or photovoltaics, a glass in X-ray tubes, or a material for embedding radioactive materials, comprising the radiopaque glass of claim 1.

17. Radiopaque glass, being free from PbO apart from impurities at most, wherein the glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%), wherein assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is as follows: TABLE-US-00030 n.sub.d ALET min. ALET max. 1.480 to <1.490 120% 700% 1.490 to <1.510 260% 1000% 1.510 to <1.530 520% 1200% 1.530 to <1.550 780% 1500% 1.550 to 1.561 850% 1600%

Description

FIGURES

[0113] The figures show:

[0114] FIG. 1 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table 1,

[0115] FIG. 2 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table 1 with advantageous upper and lower limits,

[0116] FIG. 3 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table G 1500 with advantageous upper and lower limits,

[0117] FIG. 4 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table G 1515 with advantageous upper and lower limits,

[0118] FIG. 5 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table G 1525 with advantageous upper and lower limits and

[0119] FIG. 6 the correlation between refractive index and relative aluminium equivalent thickness for the working examples of table G 1550 with advantageous upper and lower limits.

[0120] FIG. 1 shows in graph form the advantageous correlation between refractive index and relative aluminium equivalent thickness for the working examples AB1 to AB12:

[0121] It is advantageous if, within the claimed refractive index range from 1.480 to 1.561, the refractive index is assigned a relative aluminium equivalent thickness ALET (in %), as may be described by the following function:

Relative ALET (%)=(15480 to 15900)*n.sub.d(23015 to 22695).

[0122] According to a first advantageous variant of the invention, it is advantageous if the radiopaque glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%) which is greater than or equal to a minimum relative aluminium equivalent thickness (min. relative ALET) which is defined by the following equation:

min. relative ALET (%)=C*n.sub.dD, where C=11000 and D=16160.

[0123] It is further advantageous if the radiopaque glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%) which is less than or equal to a maximum relative aluminium equivalent thickness (max. relative ALET) which is determined by the equation:

max. relative ALET (%)=A*n.sub.dB, where A=11430 and B=16230.

[0124] For the radiopaque glasses, therefore, advantageously, every refractive index in the n.sub.d range 1.480 to 1.561 may be assigned an interval of the relative ALET which is bounded by a maximum relative ALET and a minimum relative ALET. A preferred radiopaque glass having a defined refractive index n.sub.d has a relative ALET which lies advantageously in the interval of the relative ALET, the interval being calculable by the equations stated above.

[0125] According to this first advantageous variant, the assignment (n.sub.d; relative ALET) is made by the establishing of two linear equations which define the advantageous upper and lower limits of the relative ALET in the n.sub.d range from 1.480 to 1.561 for preferred variants of glasses. FIG. 2 shows the graphs of the linear equations for AB1 to AB15. The graphs form what are called enveloping lines.

[0126] In the region between the upper enveloping line (maximum) and the lower enveloping line (minimum), the advantageous range of the relative ALET, which is assigned to the n.sub.d range from 1.480 to 1.561, is located for preferred variants of the glasses. As can be seen, the working examples are located between the enveloping lines.

[0127] According to a second advantageous variant of the invention, in the refractive index range between 1.480 and 1.561, the assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is made via the statement of the following intervals:

TABLE-US-00015 n.sub.d ALET min. and preferably ALET max. 1.480 to <1.490 120% and preferably 700% 1.490 to <1.510 260% and preferably 1000% 1.510 to <1.530 520% and preferably 1200% 1.530 to <1.550 780% and preferably 1500% 1.550 to 1.561 850%, and preferably 1600% preferably 910%

[0128] What this means, to give an example, is as follows: a radiopaque glass having a given composition in accordance with the invention and a refractive index which is within the n.sub.d range between 1.490 to <1.510 (e.g. n.sub.d=1.50) advantageously has a relative ALET which is at least 260% (corresponding to ALET min.). At maximum, the ALET of this glass may be preferably 1000% (corresponding to ALET max.). For radiopaque glasses which fall within other n.sub.d ranges, the other values indicated in each case for ALET min. and ALET max. are valid. ALET min. therefore defines a lower limit, and ALET max. an upper limit, for the relative ALET, referred to a defined n.sub.d range.

[0129] According to an alternative advantageous variant, in the refractive index range between 1.480 and 1.561, the assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is made via the statement of the following intervals:

TABLE-US-00016 n.sub.d ALET min. and preferably ALET max. 1.480 to <1.490 120% and preferably 760% 1.490 to <1.500 240% and preferably 875% 1.500 to <1.510 360% and preferably 990% 1.510 to <1.520 475% and preferably 1105% 1.520 to <1.530 590% and preferably 1220% 1.530 to <1.540 705% and preferably 1335% 1.540 to <1.550 820% and preferably 1450% 1.550 to 1.561 935% and preferably 1565%

[0130] What this means, to give an example, is as follows: a radiopaque glass having a given composition in accordance with the invention and a refractive index which is within the n.sub.d range between 1.480 to <1.490 (e.g. n.sub.d=1.485) advantageously has a relative ALET which is at least 120% (corresponding to ALET min.). At maximum, the ALET of this glass may be preferably 760% (corresponding to ALET max.). For radiopaque glasses which fall within other n.sub.d ranges, the other values indicated in each case for ALET min. and ALET max. are valid. ALET min. therefore defines a lower limit, and ALET max. an upper limit, for the relative ALET, referred to a defined n.sub.d range.

[0131] For gathering the data, glass bulks were produced from the glass compositions of the working examples, and the associated parameters were ascertained: the relative aluminium equivalent thickness (in %) was determined by the technique described above. The refractive index n.sub.d was determined in a known way. The number of samples per working example was 2. Each parameter was measured multiply, and the average values were calculated for the refractive index and the X-ray absorption. Linear regression allows the correlation between index of refraction and radiopacity to be represented for the radiopaque glasses according to the invention, e.g. for those glasses having the advantageous radiopacifier system of SnO.sub.2, BaO, Cs.sub.2O and F, as shown in FIG. 1.

[0132] For comparison, index of refraction and relative aluminium equivalent thickness are likewise plotted in FIG. 1 for the stated comparative examples, which are based on different radiopacifier systems. It can be seen that the working examples in the claimed refractive index range have a much higher X-ray absorption than the comparative examples (based on the respective refractive index). For the same index of refraction, X-ray absorption values achieved in the preferred glasses are substantially higherfor example, at n.sub.d=1.548, working example AB1 has a relative ALET of 1240%, while comparative example VB1 has only 763%, comparative example VB10 only 276%, and comparative example VB14 only 190%. In the low index of refraction range as well, at around 1.49, working example AB3 exhibits a relative ALET of 310%, whereas that of comparative example VB19 is only 80%. Accordingly, the X-ray visibility of the glasses preferred in the context of the invention, and of a polymer-based dental composition produced using them, is significantly increased. Accordingly, for the same thickness, optical elements (e.g. glass protective elements, etc.), comprising the preferred glass absorb more X-radiation as known optical elements or else, for the same X-ray absorption, can be made thinner, thereby allowing a weight saving to be made.

[0133] Especially in the case of glasses with low indices of refraction, it was hitherto difficult to raise the radiopacity, and possible only to raise it insufficiently, because increasing the proportion of radiopacifiers would have increased the index of refraction at the same time. With the advantageous radiopacifier system, comprising SnO.sub.2, BaO, Cs.sub.2O and F, a significant rise in the radiopacity is achieved even at low indices of refraction, and, in the higher index of refraction range, the aluminium equivalent thickness is improved very greatly relative to the known glasses.

[0134] In FIG. 2, working example AB15, in relation to the radiopacifier components Cs.sub.2O, BaO and SnO.sub.2, exhibits a similar composition and a similarly high relative ALET as working example AB7, but with a refractive index of 1.504 has a much lower refractive index than working example AB7 (n.sub.d=1.525). This is attributable to the advantageous influence of the fluorine component, allowing the refractive index to be adjusted specificallyand in this particular case, to be lowered. As a result it is possible specifically to produce a glass having a high relative ALET and a comparatively low refractive index.

[0135] A comparison of working examples AB13 and AB14, which are likewise shown in FIG. 2, makes it clear that through appropriate choice of the radiopacifiers in the preferred radiopacifier system, comprising SnO.sub.2, BaO, Cs.sub.2O and F, it is possible to produce glasses having approximately the same refractive index but having different relative ALETs.

[0136] The advantageous equations, graphs and intervals described above for correlating the refractive index of a glass and the relative aluminium equivalent thickness are correspondingly valid for the working examples of the invention which are mentioned in the tables G 1500, G 1515, G 1525 and G 1550 (see FIGS. 3 to 6). In these figures the advantageous upper and lower limits (enveloping lines) are indicated as well as comparative examples for comparison.

[0137] The invention may be additionally described by the following declarations as well: [0138] 1. Dental composition or dental material, comprising a radiopaque glass according to the invention as filler, for the treatment, more particularly for the filling, of cavities in human and/or animal teeth and/or for dental restoration. [0139] 2. Glass powder comprising powder particles composed of the radiopaque glass according to the invention. [0140] 3. Glass powder according to declaration 2, wherein the surfaces of the powder particles present are silanized. [0141] 4. Filler for polymer-based dental compositions for the treatment, more particularly filling, of cavities in human and/or animal teeth and/or for dental restoration, comprising the glass according to the invention. [0142] 5. Polymer-based dental composition comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. [0143] 6. Dental glass/polymer composite comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. [0144] 7. Dental glass/polymer composite according to declaration 6, wherein the dental polymer is preferably a UV-curable resin based on acrylate, methacrylate, 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane (bis-GMA), triethylene glycol dimethacrylate (TEGDMA or TEGMA, depending on what is meant here), urethane dimethacrylate (UDMA), alkanediol dimethacrylate or cyanoacrylate. [0145] 8. Dental glass/polymer glass ionomer cement comprising the radiopaque glass according to the invention or a glass powder composed of the glass according to the invention. [0146] 9. Use of a radiopaque glass according to the invention as dental glass for producing a dental glass/polymer dental composition comprising dental polymer for the treatment, more particularly filling, of cavities in human and/or animal teeth and/or for dental restoration. [0147] 10. Use of a radiopaque glass according to the invention as glass powder. [0148] 11. Use according to declaration 10, wherein the surfaces of the powder particles present are silanized. [0149] 12. Use according to declaration 10 or 11 in a dental glass/polymer dental composition comprising dental polymer. [0150] 13. Use of a radiopaque glass according to the invention as [0151] radiopacifier in a polymer-based dental composition and/or as [0152] element for optical applications and/or as [0153] cover glass and/or substrate glass in display technology for cathode ray tubes (CRT) and/or as [0154] cover glass and/or substrate glass in photovoltaics and/or as [0155] lamp glass in X-ray tubes and/or as [0156] material for the embedding of radioactive materials. [0157] 14. Radiopaque glass, being free from PbO apart from impurities at most, wherein the glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%) which is greater than or equal to a minimum relative aluminium equivalent thickness (min. relative ALET) which is determined by the following equation:

min. relative ALET (%)=C*n.sub.dD, where C=11000 and D=16160. [0158] 15. Radiopaque glass, being free from PbO apart from impurities at most, wherein the glass has a refractive index n.sub.d in the refractive index range between 1.480 and 1.561 and has a relative aluminium equivalent thickness ALET (%), wherein assignment between the refractive index n.sub.d of the glass and the relative aluminium equivalent thickness ALET (%) is as follows:

TABLE-US-00017 n.sub.d ALET min. ALET max. 1.480 to <1.490 120% 700% 1.490 to <1.510 260% 1000% 1.510 to <1.530 520% 1200% 1.530 to <1.550 780% 1500% 1.550 to 1.561 850% 1600% [0159] 16. Radiopaque glass having a refractive index n.sub.d of 1.480 to 1.561, being free from PbO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00018 SiO.sub.2 35-75 B.sub.2O.sub.3 2-16 Al.sub.2O.sub.3 0.8-7.5 K.sub.2O 0-14 BaO 0-24 Cs.sub.2O 1-30 SnO.sub.2 0-15 F 0-8 BaO + Cs.sub.2O + SnO.sub.2 + F 10, and preferably comprising La.sub.2O.sub.3 with a content of 0-19 [0160] 17. Radiopaque glass having a refractive index n.sub.d of 1.480 to 1.510, being free from PbO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00019 SiO.sub.2 40-70, in particular 50-65 B.sub.2O.sub.3 5-15, in particular 6-15 Al.sub.2O.sub.3 0.8-7.5, in particular 0.8-6 K.sub.2O 0-10, in particular 2-6 BaO 0-24, in particular 0-17 Cs.sub.2O 1-30, in particular 7-24 SnO.sub.2 0-15, in particular 0-3 F 0-8, in particular 0-6 La.sub.2O.sub.3 0-8, in particular 0-5 BaO + Cs.sub.2O + SnO.sub.2 + F 10, in particular 13-35 [0161] 18. Radiopaque glass having a refractive index n.sub.d of 1.505 to 1.520, being free from PbO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00020 SiO.sub.2 42-65, in particular 47-64 B.sub.2O.sub.3 5-15, in particular 6-15 Al.sub.2O.sub.3 0.8-7.5, in particular 0.8-6 K.sub.2O 0-10, in particular 2-6 BaO 0-15, in particular 2-10 Cs.sub.2O 5-30, in particular 6-26 SnO.sub.2 0-10, in particular 0-3 F 0-5, in particular 0-3 La.sub.2O.sub.3 0-9, in particular 0-7, 5 BaO + Cs.sub.2O + SnO.sub.2 + F 9, in particular 11-35 [0162] 19. Radiopaque glass having a refractive index n.sub.d of 1.519 to 1.542, being free from PbO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00021 SiO.sub.2 42-65, in particular 45-61 B.sub.2O.sub.3 5-15, in particular 7-15 Al.sub.2O.sub.3 0.8-7.5, in particular 0.8-6 K.sub.2O 0-14, in particular 1.5-7 BaO 0-18, in particular 6-14 Cs.sub.2O 5-25, in particular 6-19 SnO.sub.2 0-6, in particular 0-3 F 0-5, in particular 0-3 La.sub.2O.sub.3 0-19, in particular 0-17 BaO + Cs.sub.2O + SnO.sub.2 + F 8, in particular 10-35 [0163] 20. Radiopaque glass having a refractive index n.sub.d of 1.542 to 1.561, being free from PbO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00022 SiO.sub.2 37-56, in particular 40-53 B.sub.2O.sub.3 2-16, in particular 3-14 Al.sub.2O.sub.3 0.8-7.5, in particular 0.8-6 K.sub.2O 0-14, in particular 0-12 BaO 0-24, in particular 4-24, preferably 4-21 Cs.sub.2O 9-25, in particular 10-19 SnO.sub.2 0-6, in particular 0-3 F 0-5, in particular 0-3 La.sub.2O.sub.3 1-19, in particular 4-17 BaO + Cs.sub.2O + SnO.sub.2 + F 10, in particular 15-42 [0164] 21. Radiopaque glass having a refractive index n.sub.d of 1.480 to 1.561, being free from PbO and BaO apart from impurities at most, comprising (in wt % based on oxide)

TABLE-US-00023 SiO.sub.2 35-75, in particular 38-70 B.sub.2O.sub.3 2-16, in particular 5-15, preferred 6-15 Al.sub.2O.sub.3 0.8-7.5, in particular 0.8-6 K.sub.2O 0-14, in particular 0-10, preferred 0-7 Cs.sub.2O 1-30, in particular 6-28, preferred 7-24 SnO.sub.2 0-15, in particular 0-6, preferred 0-3 F 0-8, in particular 0-6, preferred 0-3 La.sub.2O.sub.3 0-19, in particular 0-16 BaO + Cs.sub.2O + SnO.sub.2 + F 10.

[0165] With the described radiopacifier combination (SnO.sub.2, BaO, Cs.sub.2O) and advantageously with the defined addition of fluorine it is possible to formulate a glass having on the one hand a desired index of refraction and on the other hand an extremely high X-ray absorption. In accordance with the invention, in the refractive index range from 1.480 to 1.561, it is possible to realize a range of the relative aluminium equivalent thickness from about 120% up to more than 1400%, e.g. up to 1600%.

[0166] The examples also demonstrate that the refractive indices n.sub.d of the glass system according to the invention, particularly in a range from 1.480 to 1.561, can be adapted to the intended application without detriment to the necessary ALETs. As a result, the system can be used advantageously in particular as a filler in dental compositions, but also for other applications which impose high requirements on factors including the purity and/or the chemical resistance and temperature stability. The glass system can be produced at favourable cost on an industrial scale.

[0167] The glass according to the invention, furthermore, is relatively easy to melt and therefore efficient to produce. Found in particular has been a glass system in which, through changes in the individual constituents within the stated limits, it is possible to adjust the refractive index in line with the requirements of the applicationfor example, requirements asked of a dental filling materialwith the resulting glass having an improved ALET. The variation of the possible refractive indices encompassed by the invention is relatively wide. This glass system permits especially rational industrial production of glasses within the glass system, especially since only a defined selection of raw materials need be held in stock, within which the proportions are varied in the stated amounts. Accordingly, the procedural regimes when melting the glasses within the glass system are also very similar.