Dental composites based on X-ray-opaque mixed oxides prepared by flame spraying

1. A dental composite comprising at least one nanoparticulate mixed oxide (a) of SiO 2 with X-ray-opaque metal oxides of one or more elements selected from the group consisting of Y, La, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu which has been prepared by flame spraying and wherein the mixed oxides have at least one of the following features:

a) an amorphous structure,

b) a homogeneous element distribution,

c) a very low organic content,

d) an X-ray opacity which can be varied,

e) an index of refraction which can be varied, and

f) a shperical particle shape.

2. A dental composite as claimed in claim 1 , wherein the mixed oxides (a) are mixed oxides of SiO 2 with an X-ray-opaque metal oxide of Yb, in particular SiO 2 /Yb 2 O 3 .

3. A dental composite as claimed in claim 1 , comprising one mixed oxide (a).

4. A dental composite as claimed in claim 1 , wherein (a) from 5 to 90% by weight, based on the composition, of mixed oxides are present.

5. A dental composite as claimed in claim 1 which has an X-ray opacity of from 50 to 800% A1, and in which the mixed oxides (a) have a mean primary particle size of from 3 to 100 nm, determined by measurement of the BET surface area, have an index of refraction of from 1.46 to 1.70, and/or have an organic content of less than 0.5% by mass, of oxidizable carbon.

6. A process for producing dental composites which comprises

(i) preparing nanoparticulate mixed oxides (a) of SiO 2 with X-ray-opaque metal oxides of one or more elements selected from the group consisting of Y, La, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu by flame spraying,

(ii) dispersing the mixed oxides (a) in suitable polymerizable matrix resins,

(iii) adding a polymerization initiator (c),

(iv) if desired, mixing the dispersion with further constituents matrix monomer (b), further fillers (d), colorants (e) and/or further additives (f) and

(v) subsequently curing the dispersion by thermal or light-induced polymerization.

7. A method for filling, surface sealing or restoring teeth, said method comprising applying the dental composite as claimed in claim 1 to teeth.

8. A dental prosthesis, dental bridge or similar tooth replacement piece comprising a dental composite as claimed in claim 1 .

9. A method for filling, surface sealing or restoring teeth, wherein the dental composite as claimed in claim 1 is introduced into a mold, and cured and applied to teeth.

10. An adhesive, cement and/or facing material cement for dental applications comprising the composite as claimed in claim 1 .

11. A dental composite prepared by the process of claim 6 .

12. A method for filling, surface sealing or restoring teeth comprising applying the dental composite prepared by the process of claim 6 to teeth.

13. A dental prosthesis, dental bridge and/or similar tooth replacement piece comprising a dental composite prepared by the process of claim 6 .

14. A method for filling, surface sealing or restoring teeth, wherein the dental composites prepared by the process of claim 6 are introduced into a mold and cured and applied to teeth.

15. An adhesive, cement and/or facing material cement for dental applications comprising the dental composite prepared by the process of claim 6 .

16. A dental composite comprising:

nanoparticulate mixed oxides (a) of SiO 2 with X-ray-opaque metal oxides of one or more elements selected from the group consisting of: Y, La, Ta, Ce, Pr, Nd,

Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, prepared by flame spraying,

suitable polymerizable matrix resins,

polymerization initiator (c), and optionally,

further constituents matrix monitor (b), further fillers (d), colorants (e) and/or further additives (f).

17. A dental composite as claimed in claim 1 , wherein the mixed oxides (a) are SiO 2 /YbO 3 mixed oxides.