FILLERS FOR DENTAL COMPOSITES

Abstract

A powdery filler for dental materials consisting of particles of feldspar or feldspar derivatives having a mean particle diameter (d50) of from 0.25 to 5 m, said particles having a coating with a silicon compound containing reactive groups.

Claims

1. A powdery filler for dental filler materials comprising particles of feldspar or feldspar derivatives having a mean particle diameter (d50) of from 0.5 to 5 m, said particles having a coating with a silicon compound containing reactive groups said dental filler materials being composite materials.

2. The powdery filler according to claim 1, wherein said reactive groups comprise polymerizable groups.

3. The powdery filler according to claim 2, wherein said polymerizable groups comprise epoxy or vinyl groups.

4. The powdery filler according to claim 1, wherein said feldspar is selected from the group of plagioclase feldspars or alkali feldspars.

5. The powdery filler according to claim 1, wherein said feldspar is selected from perthite, albite, oligoclase, andesine, labradorite, bytownite, anorthite as well as SiO.sub.2-deficient feldspar derivatives, and mixtures thereof.

6. The powdery filler according to claim 1, wherein said feldspar has a mean particle diameter (d50) of from 0.5 to 3.5 m.

7. The powdery filler according to claim 1, wherein said feldspar is transparent.

8. The powdery filler according to claim 1, wherein said filler has a bimodal particle diameter distribution.

9. The powdery filler according to claim 8, wherein one peak of said bimodal distribution is within a range of from 0.5 to 1 m, and a second peak is within a range of from 1 to 3.5 m.

10. A process for preparing a powdery filler according to claim 1, with the following steps: grinding feldspar silanizing the particles with a reactive silicon compound.

11. A dental composite material containing from 60 to 90% by weight of a powdery filler according to claim 1; from 10 to 40% by weight of a polymerizable resin, wherein said polymerizable resin can react with the reactive groups.

12. The dental composite material according to claim 11, wherein said dental composite material can be cured by means of light.

13. A dental filler material containing a cured composite material according to claim 11.

14. A method of making a composite dental filler material, comprising: combining a powdery filler comprising particles of feldspar or feldspar derivatives having a mean particle diameter (d50) of from 0.5 to 5 m, said particles having a coating with a silicon compound containing reactive groups according to claim 1 with a polymerizable resin, wherein said polymerizable resin can react with the reactive groups.

15. The powdery filler according to claim 1, wherein said feldspar has a mean particle diameter (d50) of from 0.8 to 1.5 m.

16. The powdery filler according to claim 2, wherein said polymerizable groups comprise methacrylic or acrylic groups.

17. The powdery filler according to claim 5, wherein the SiO.sub.2-deficient feldspar derivative is nepheline.

18. The powdery filler according to claim 11, wherein the feldspar enables photoinitiated polymerization in a composite with light having a wavelength range of from 400 to 520 nm.

19. The powdery filler according to claim 1, wherein said feldspar is albite.

20. The powdery filler according to claim 1, wherein said feldspar is oligoclase.

Description

[0035] FIG. 1 shows a filler according to the invention in a grain size of 0.3 m.

[0036] FIG. 2 shows the filler according to the invention in a grain size of 3.5 m.

[0037] FIG. 3 shows a composite material obtained using the material according to the invention after curing and polishing the surface. The images are scanning electron micrographs.

EXAMPLE 1

[0038] A polymerizable synthetic resin containing Bis-GMA (2,2-bis[4-(2-hydroxy-3-methylacryloxypropoxy)phenyl]propane together with TEGDMA (2-methyl-2-propenoic acid) was prepared. Camphorquinone and 2-dimethylaminoethyl methacrylate were employed as photoinitiators.

[0039] A feldspar coated with -methacryloxypropyltrimethoxysilane served as the feldspar. The mixing of the polymerizable resin and the filler was effected by manual mixing. The following feldspar grain sizes were used:

[0040] a) Grain size 0.3 m

[0041] b) Grain size 0.8 m

[0042] c) Grain size 3.5 m

[0043] d) Mixture of fillers 0.8 m and 3.5 m in a weight ratio of 40:60

[0044] As Comparative Examples, there were employed:

[0045] C1: Barium glass, grain size 0.7 m (GM 39923 of the company Schott)

[0046] C2: Barium glass, grain size 1.0 m (GM 27884 of the company Schott)

EXAMPLE 2

[0047] The following composite materials were prepared:

[0048] Filler a) 60%, synthetic resin 40%

[0049] Filler b) 67%, synthetic resin 33%

[0050] Filler c) 73%, synthetic resin 27%

[0051] Filler d) 74%, synthetic resin 36%

[0052] Filler C1 68%, synthetic resin 32%

[0053] Filler C2 72%, synthetic resin 28%

[0054] The curing was effected with a Dentacolor XS (Heraeus Kulzer) for 180 s for a 6 mm test specimen.

[0055] Subsequently, various properties of the materials were examined. The results are shown in the following Table.

TABLE-US-00001 Bending Shear Vickers strength strength hardness Roughness.sup.1) [MPa] [MPa] [HV 5-20] Ra in [m] C1 0.7 m 115.6 22.6 47.0 n.d. C2 1.0 m 145.0 31.3 54.4 n.d. (a) 0.3 m 144.0 19.7 48.5 0.05 (b) 0.8 m 212.0 29.7 53.9 0.05 (c) 3.5 m 205.0 28.2 51.3 0.05 (d) bimodal 203.0 31.3 47.6 0.05 .sup.1)after grinding with: 1st stage: roughening the surface with a carbide cutter 2nd stage: CompoMaster Coarse (Shofu) 3rd stage: CompoMaster (Shofu) 4th stage: DirectDia Paste; Super Snap Buff Disk (Shofu) n.d.: not determined

[0056] As compared to usual dental filler materials based on strontium or barium glasses, the fillers according to the invention showed the same or in part improved mechanical properties. In the composite systems, very good curing results were achieved with the fillers according to the invention.

[0057] The linear shrinkage was from 1.4 to 1.7% and was thus better than in the prior art. High filler contents could be achieved, and nevertheless, a good workability of the composites according to the invention was found. The materials were highly transparent, so that they did not cause any change in color.