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

a technology of mixed oxides and dental composites, which is applied in the field of dental composites based on x-ray-opaque mixed oxides prepared by flame spraying, can solve the problems of reduced transparency and aesthetics, high cost, and high cost of dental composites

Inactive Publication Date: 2008-07-03
BURTSCHER PETER +4
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides dental composites with good X-ray opacity, low intrinsic color, and a low organic content. The composites have a high degree of transparency and can be used for dental purposes such as cements, facing materials, and filling composites. The composites have a unique structure with a high degree of homogeneity and low solvent content. The mixed oxides used in the dental composites have a high index of refraction and can be adjusted to have a variable X-ray opacity, index of refraction, and thickening action. The mixed oxides are prepared by flame spraying, which allows for a more economical and simpler process compared to wet chemical methods. The particle size of the mixed oxides can be adjusted at a very small particle size. The invention also provides a method for producing the mixed oxides using a homogeneous solution or emulsion of metal oxide precursors and a fuel or solvent, which can be atomized to form fine droplets in a flame and then reacted to form the mixed oxides.

Problems solved by technology

The X-ray opacity of silicon oxide is very low, so that a composite based on this filler has only a low X-ray opacity, which makes dental diagnostics more difficult.
However, the simultaneous use of fillers having different indices of refraction reduces the transparency and thus the aesthetics.
In contrast, X-ray opaque composites based on nanofillers have a transparency which is too low.
The nanoparticulate fillers which are described in the above-cited prior art and in which SiO2 has been combined with an X-ray-opaque metal oxide contribute, as a result of their two-phase morphology (e.g. core / shell, doping, mixing of oxides) and the associated inhomogeneous element distribution in the solid and also the partially crystalline structure, only unsatisfactorily to transparent properties in the composite.
In addition, matching of the index of refraction of the fillers to that of the matrix is possible to only a limited extent.
Furthermore, the nanoparticulate, nonspherical fillers usually display an extremely high thickening action which is very difficult to influence.
A further disadvantage of wet chemical processes for preparing mixed oxides is that in the case of incomplete drying (complete drying is extremely difficult) small amounts of residual solvent always remain and these can then, during the subsequent calcination, lead to discoloration of the particles and thus also the dental composite.
Such discolored products can generally not be used for aesthetic reasons and thus constitute reject material.

Method used

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

Examples

Experimental program
Comparison scheme
Effect test

example 1

Synthesis of Mixed Oxides of the Elements Si and Yb

[0078]A two-fluid nozzle was used at a liquid inflow rate of 5 ml / min. The atomization gas was oxygen (5 l / min). The support flame was operated using premixed methane / oxygen (1.5 l / min / 3.2 l / min). The enveloping air stream was 5 l / min of oxygen. The precursors used for Si and Yb were tetraethoxysilane (TEOS) and ytterbium nitrate pentahydrate (Yb (NO)3.5H2O), respectively. To remove all water of crystallization from the Yb precursor, Yb(NO)3.5H2O was reacted in 18.75% by volume of acetic anhydride and 81.25% by volume of 2-ethylhexanoic acid at 107° C. under inert gas (N2). In this reaction, all oxides of nitrogen were driven off and the water was removed by reaction with acetic anhydride to form acetic acid. The solution formed in this way was mixed with 45.08% by volume of xylene and TEOS to give a total metal concentration of 0.5 mol / l. Various Yb / (Yb+Si) ratios could easily be set using this method. Solutions containing up to 50...

example 2

Evaluation of the Thickening Action of the Mixed Oxides of the Elements Si and Yb Prepared as Described in Example 1

[0081]To examine the thickening action, model composite pastes were prepared from 16.5% of Yb / Si mixed oxide of differing specific surface areas and 83.5% of a free-radically polymerizable monomer composition (41.82 parts of bis-GMA, 37 parts of UDMA, 20 parts of TEGDMA, 0.73 part of photoinitiator, 0.55 part of additives). 0.1 g of paste was loaded between two glass plates under a load of 120 g for a period of three minutes and the resulting diameter of the paste was determined. The thinner this “disc consitency” of the paste, i.e. the lower the thickening action, the greater the diameter obtained. The results demonstrate that the consistency of the pastes depends significantly on the specific surface area of the nanoparticle filler (Table 3).

TABLE 3Influence of the specific surface area of themixed oxide filler on the disc consistency of thecomposite pastesSpecific s...

example 3

Production of a Filling Composite Based on a Mixed Oxide of the Elements Si and Yb Prepared as Described in Example 1

[0083]A composite (composite A) was produced from 48% by mass of a light-curing monomer composition (41.82 parts of bis-GMA, 37 parts of UDMA, 20 parts of TEGDMA, 0.73 part of photoinitiator, 0.55 part) and 52% by mass of an X-ray-opaque Yb / Si mixed oxide having a Yb2O3 content of 30% by mass and a specific surface area of 125 m2 / g which had been prepared by flame spraying as described in Example 1. As a comparative example, a composite (composite B) was produced from 50% by mass of the same light-curing monomer, 35% by mass of silanized pyrogenic SiO2 OX-50 and 15% by mass of ytterbium fluoride, and the transparency and X-ray opacity were determined after curing of the composites:

TABLE 4Transparency and X-ray opacity of thecomposites from Example 3TransparencyMaterial(%)X-ray opacity (% Al)Composite A13.2180Composite B9.5150

[0084]The results show that an acceptable t...

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Abstract

The present invention relates to dental composites comprising at least one nanoparticulate mixed oxide (a) of SiO2 with X-ray-opaque metal oxides of one or more elements selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu which has been prepared by flame spraying.

Description

[0001]The present invention relates to the use of at least one nanoparticulate mixed oxide (a) of SiO2 with X-ray-opaque metal oxides of one or more elements selected rom 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 as X-ray-opaque filler in dental composites, to the resulting dental composites and to their production and use.DEFINITIONS OF TERMS[0002]Amorphous solids are homogeneous, noncrystalline solids in which the molecular building blocks are bound to one another by more or less pronounced short-range ordering similar to the situation in a crystal but do not have the long-range order, i.e. regular repetition of a unit cell, characteristic of crystals. In contrast to crystalline substances, such amorphous substances are fully isotropic. For the purposes of the present invention, amorphous substances are ones which have a crystallinity index of less than 0.1, preferably less than 0.05, in each cas...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C23C4/10A61K6/02A61K6/027A61K6/083A61K6/884
CPCA61K6/0073A61K6/083C08L33/00A61K6/71A61K6/887
Inventor BURTSCHER, PETERMADLER, LUTZMOSZNER, NORBERTPRATSINIS, SOTIRIS E.RHEINBERGER, VOLKER M.
Owner BURTSCHER PETER
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