Radiopaque, low visual opacity dental composites containing non-vitreous microparticles
AssigneeMinnesota Mining and Manufacturing Company
InventorRonald M. Randklev
Life of this patent
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Abstract
Radiopaque, low visual opacity dental composites and non-vitreous microparticles for use therein, the microparticles individually containing amorphous silica microregions interspersed with radiopacifying polycrystalline ceramic metal oxide microregions, the microparticles being substantially free of visually opacifying inclusions such as crystalline microregions having diameters greater than about 0.4 micrometers.
Claims20
Radiopaque dental composite, comprising a mixture of:
- (a) polymerizable resin suitable for use in the oral environment, and
- (b) non-vitreous microparticles, said microparticles individually comprising:
- (i) a plurality of amorphous microregions comprising oxide of silicon, substantially uniformly interspersed with
- (ii) a plurality of crystalline microregions comprising radiopacifying polycrystalline ceramic metal oxide,
- said microparticles being substantially free of visually opacifying inclusions.
Radiopaque dental composite, comprising a one-part visible light-cure resin bonded ceramic containing a mixture of:
- (a) up to 30 volume percent polymerizable resin suitable for use in the oral environment, and
- (b) at least 70 volume percent non-vitreous microparticles having diameters less than about 50 micrometers and an index of refraction less than 1.60, said microparticles individually comprising:
- (i) a plurality of amorphous microregions comprising silica, substantially uniformly interspersed with
- (ii) a plurality of crystalline microregions comprising tetragonal zirconia,
- said microparticles being substantially free of visually opacifying inclusions.
Non-vitreous microparticles having a diameter less than about 50 micrometers, said microparticles individually comprising:
- (a) a plurality of amorphous microregions comprising oxide of silicon, substantially uniformly interspersed with
- (b) a plurality of crystalline microregions comprising radiopacifying polycrystalline ceramic metal oxide,
- said microparticles being substantially free of visually opacifying inclusions.
A process for making a radiopaque dental composite, comprising the steps of:
- (a) filtering an aqueous or organic dispersion or sol of amorphous silica through a microfine filter having a pore diameter less than 0.4 micrometers;
- (b) filtering an aqueous or organic dispersion, sol, or solution of radiopacifying ceramic metal oxide, or a precursor organic or inorganic compound which is calcinable thereto, through a microfine filter having a pore diameter less than 0.4 micrometers;
- (c) combining and gelling the filtered products of steps (a) and (b);
- (d) heating the resulting gelled product at a temperature and pressure sufficient to remove the water or solvents therefrom without causing boiling thereof, to form a green state powder;
- (e) milling said green state powder to reduce the particle size thereof;
- (f) firing the resulting milled powder to convert said ceramic metal oxide or precursor compound to polycrystalline ceramic metal oxide, while preventing the growth or formation of crystalline microregions having a diameters greater than about 0.4 micrometers;
- (g) milling the resulting fired powder to form microparticles which individually comprise
- (i) a plurality of amorphous microregions comprising oxide of silicon, substantially uniformly interspersed with
- (ii) a plurality of crystalline microregions comprising radiopacifying polycrystalline ceramic metal oxide;
- (h) silane treating said microparticles to facilitate wetting thereof by polymerizable resin;
- and
- (i) mixing the resulting silane-treated microparticles with polymerizable resin suitable for use in the oral environment to form said composite.
Dependencies are inferred from the claim text.