Fillers and composite materials with zirconia and silica nanoparticles
View Patent ↗Fillers containing silica-zirconia nanoclusters are disclosed. The fillers may be prepared by mixing a sol of silica nanoparticles with a sol of preformed, crystalline nanozirconia particles. The fillers provide desirable optical properties, such as opalescence, and are useful in dental compositions.
1. A method of making a filler for a composite material, the method comprising:
(a) providing a zirconia sol comprising preformed, crystalline zirconia nanoparticles with a mean diameter from about 3 nm to about 30 nm,
(b) providing a silica sol comprising silica nanoparticles with a mean diameter from about 10 nm to about 100 nm,
(c) combining the zirconia sol and the silica sol to form a mixture of zirconia and silica nanoparticles,
(d) heating the mixture to a temperature from about 400° C. to about 1000° C. and
(e) milling the heated mixture to form a filler comprising silica-zirconia nanoclusters.
2. The method of claim 1 , wherein the nanoclusters have a mean volumetric diameter from about 0.01 to about 100 micrometers.
3. The method of claim 1 , wherein the nanoclusters have a mean volumetric diameter from about 0.5 to about 10 micrometers.
4. The method of claim 1 , wherein the silica nanoparticles have a mean diameter from about 15 nm to about 35 nm and the zirconia nanoparticles have a mean diameter from about 5 nm to about 15 nm.
5. The method of claim 1 , wherein the silica nanoparticles and zirconia nanoparticles are uniformly distributed in the nanoclusters.
6. The method of claim 1 , further comprising lowering the pH of the silica sol to below 1.2 prior to mixing with the zirconia sol.
7. The method of claim 1 , wherein the silica-zirconia filler has a refractive index from about 1.44 to about 1.65.
8. The method of claim 1 , wherein the zirconia sol is acid reduced.
9. A hardenable dental composition comprising:
(a) a polymerizable component,
(b) an initiator system, and
(c) a filler comprising nanoclusters of zirconia nanoparticles and silica nanoparticles,
wherein the composition has a C ab value of at least 15 when measured according to the Opalescence Test Method.
10. The composition of claim 9 , wherein the silica nanoparticles have a mean diameter from about 15 nm to about 60 nm.
11. The composition of claim 9 , wherein the zirconia nanoparticles have a mean diameter from about 5 nm to about 15 nm.
12. The composition claim 9 , wherein the silica nanoparticles and zirconia nanoparticles are uniformly distributed in the nanoclusters.
13. The composition of claim 9 , wherein composition has a C ab value of at least 18 when measured according to the Opalescence Test Method.
14. The composition of claim 9 , wherein the composition has a haze measurement of less than 70 haze units.
15. The composition of claim 9 , wherein the nanoclusters are surface treated.
16. The composition of claim 9 , wherein the polymerizable component comprises an ethylenically unsaturated compound.
17. The composition of claim 16 , wherein the polymerizable component comprises a (meth)acrylate.
18. The composition of claim 9 , wherein the composition has a refractive index from about 1.44 to about 1.65.
19. A dental restorative material comprising the dental composite of claim 9 .
20. The dental restorative material of claim 19 , wherein the material is a filling material, preformed bridge or crown, a flowable restorative, or temporary restorative material.
21. The method of claim 1 , wherein heating the mixture occurs at a Temperature from about 450° C. to about 950°C.