News Column

Patent Issued for Fillers and Composite Materials with Zirconia and Silica Nanoparticles

May 30, 2014

By a News Reporter-Staff News Editor at Health & Medicine Week -- 3M Innovative Properties Company (St. Paul, MN) has been issued patent number 8722759, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also 3M Innovative Properties Company).

The patent's inventor is Craig, Bradley D. (Lake Elmo, MN).

This patent was filed on October 9, 2009 and was published online on May 13, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Over the past several decades, there has been an increasing demand among dentists and dental patients for more aesthetic dental restorations. The dental industry's growing focus on aesthetic dentistry has led to the development of dental restorative compositions that more closely mimic the appearance of natural teeth. For example, tooth-colored, composite resin materials have been developed that can be used in place of, for example, metal amalgam fillings, to provide more natural looking dental restorations. In recent years, highly aesthetic composite materials containing silica and/or zirconia nanofillers have become available with shading systems and opacity options that make it possible for a dentist to create dental restorations so natural looking they are virtually undetectable to the casual observer.

"Natural tooth enamel has an opalescent quality to it in that it preferentially bends the shorter (blue) wavelengths of light, appearing bluish against a dark background, and more orange/yellow against a white background. Although opalescent dental composites have been developed, this property is often lacking from dental composites that use a silica-zirconia nanofiller system. Despite the many beneficial properties offered by silica-zirconia nanofillers, lack of opalescence may be seen as a drawback. Thus, there remains a need for filler systems, especially silica-zirconia nanofiller systems, that provide dental composites having opalescent properties to better mimic the appearance of natural teeth, while still maintaining suitable handling, radiopacity, clarity, translucence, and other desirable properties of dental composites."

Supplementing the background information on this patent, NewsRx reporters also obtained the inventor's summary information for this patent: "The present invention features fillers for use in composite materials. The fillers include clusters of zirconia and silica nanoparticles that provide opalescence and radiopacity, along with excellent optical clarity in both reflectance and transmission.

"The filler may be prepared by (a) providing a zirconia sol comprising preformed, crystalline zirconia nanoparticles with a diameter from about 3 nm to about 30 nm, (b) providing a silica sol comprising silica nanoparticles with a diameter from about 10 nm to about 100 nm, combining the zirconia sol and the silica sol to form a mixture of zirconia and silica nanoparticles, and (d) heating the mixture to a temperature from about C. to about C. and subsequently milling the resultant material to form a filler comprising silica-zirconia nanoclusters with a diameter from about 0.25 micron to about 50 micron.

"Typically, the nanozirconia sol is acid reduced prior to mixing with the nanosilica sol. In some implementations, the silica nanoparticles and zirconia nanoparticles are uniformly distributed in the resulting nanoclusters. Optionally, the method further includes a step of surface treating the silica-zirconia nanoclusters with, for example, a silane coupling agent or similar treatment to assist with incorporation into the resin component.

"The zirconia-silica fillers of the invention are useful in composite materials, including dental composite materials. Such composites typically include, a polymerizable component, such as a methacrylate or other ethylenically unsaturated compound, an initiator system, and a filler comprising the silica-zirconia nanoclusters. These composite materials typically have a C.sub.ab value of at least 15, more typically at least 18, and most typically at least 20.

"Typically, the dental composites of the invention have a refractive index from about 1.44 to about 1.65, more typically from about 1.50 to about 1.6, most typically from about 1.50 to about 1.56. The composites also typically exhibit excellent handling characteristics, radiopacity, low haze (typically less than 70, more typically less than 60, and most typically less than 55 haze units), and possess a directionally independent clarity or translucence, i.e. the clarity is less dependent on the angle of the transmitted light through the material, which make them useful in a variety of dental and orthodontic applications, including as dental restoratives (e.g. filling materials, flowable restoratives, preformed crowns and bridges, temporary restoratives), dental adhesives, dental cements, cavity liners, orthodontic adhesives, dental sealants, dental coatings, and the like. The compositions and related methods may be used to prepare dental articles by hardening to form, for example, dental fillings, dental mill blanks, dental crowns and bridges, dental prostheses, orthodontic devices, and the like.

"The above summary is not intended to describe each embodiment or every implementation of the invention. Other embodiments, features, and advantages of the present invention will be apparent from the following detailed description thereof, and from the claims."

For the URL and additional information on this patent, see: Craig, Bradley D.. Fillers and Composite Materials with Zirconia and Silica Nanoparticles. U.S. Patent Number 8722759, filed October 9, 2009, and published online on May 13, 2014. Patent URL:

Keywords for this news article include: Dentistry, Nanoparticle, Orthodontics, Nanotechnology, Emerging Technologies, 3M Innovative Properties Company.

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Source: Health & Medicine Week

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