JPH027922B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to radiopaque filler compositions and, in particular, to dental prosthetic compositions using such radiopaque filler compositions. Particulate reinforced polymer matrix composites are widely used as dental prosthetics, especially fillings and incisal edge repairs, inlays, etc. The inorganic filler phase is typically a siliceous material,
Examples include silica, quartz, refractory salts, glass or ceramic materials. Although these reinforced polymeric materials give acceptable results with respect to strength, coloration, non-toxicity and coefficient of thermal expansion, these materials are difficult to distinguish by X-ray analysis such as those used in dental diagnostics. suffers from this drawback. Therefore, many attempts have been made to obtain radiopaque dental compositions in which barium-containing glasses are used to replace some or all of the siliceous fillers. An example is US Pat. No. 3,808,170 (S.
Rogers), U.S. Patent No. 3801344, U.S. Patent No. 3826778
No. 3,911,581 (both E. Dietz) and US Pat. No. 4,032,504 (Lee Rharmaceuticals). However, glass fillers formulated to contain sufficient barium to achieve sufficient radiopacity may be difficult to achieve since the glass is fairly soluble in aqueous environments, particularly in the oral environment, and barium ions are leached from the glass. It suffers from the disadvantage of doing so.
There is very strong evidence that this form of barium presents a toxicity risk. Recently attempts have been made to replace barium glass with other radiopaque filler materials. These attempts have included, for example, the use of fairly insoluble barium salts such as barium carbonate and barium sulfate in combination with siliceous fillers. However, these reinforced ceramic materials were unsatisfactory in terms of the mechanical strength of the resulting composites. U.S. Pat. No. 3,959,212 (Rockett et al.) discloses the use of microcrystalline barium-containing silicates and, in particular, calcium barium silicate in crystalline form, a polymerizable binder, a catalyst system for polymerizing the binder, and at least a portion of which is radiopaque. The present invention teaches use in direct-fill dental composites containing finely divided inorganic fillers formed from crystalline calcium barium silicate. Although this composition provides some improvement with respect to the solubility of the barium component of the inorganic filler, it is not completely satisfactory with regard to the leaching properties of the barium component and the radiopacity of the composite material. Also, for example, US Pat. No. 3,971,754 (A.
Jurecic) and U.S. Pat. No. 3,973,972 and U.S. Pat.
No. 4017454 (both by G. Muller), it was proposed to utilize the high X-ray absorption ability of high atomic weight atoms. For example, U.S. Pat. No. 3,971,754 discloses ceramic filler compositions using X-ray absorbing atoms selected from lanthus in oxide, carbonate or fluoride form, strontium, and hafnium with minor additions to tantalum. teaching. According to this patent, the compound of X-ray absorbing atoms accounts for about 5-60% of the total molten glass composition, preferably 25-40%.
This composition is then incorporated into the repair matrix. U.S. Pat. No. 3,973,972 and U.S. Pat. No. 4,017,454 disclose transparent, colorless glass-ceramics with low expansion coefficients, high X-ray absorption capabilities, and suitable for use in dental filling compositions; The composition mainly consists of SiO ₂ , Al ₂ O ₃ , Li ₂ O, P ₂ O ₅ and
In addition to _the other glass components which are _ZrO2 , it contains about 10-20% by weight _La2O3 and up to about ₇ % _Ta2O5 . In this composition, La ₂ O ₃ is the main X-ray absorbing compound and tantalum oxide acts as a nucleating agent together with zirconium oxide. Additionally, U.S. Pat. No. 3,801,344 discloses the use of other radiopaque-forming oxides, such as strontium oxide or lanthanum oxide, and oxides of other rare earths of the lanthanide series, atomic numbers 57-71, such as samarium oxide, lanthanum oxide, etc. It has been suggested that dysprosium and terbium oxide can be used, although lanthanum oxide, like praseodymium oxide, generally imparts an undesirable color to tooth filling or porcelain compositions. In this regard, please refer to column 3, line 55 to column 4, line 2 of the patent. All of these solutions related to the various glasses mentioned above are different from the compositions described below. Manufacturing such glasses is difficult and expensive, and presents problems in matching the reflectance of the resin. In the present invention, the amount of high atomic weight X-ray absorbing rare earth elements is such that thorium oxide ( _ThO2 ) is used as substantially the only X-ray absorbing component in an inorganic particle filler composition such as silica, glass, etc. It has been found that this can provide all the necessary properties required of a filled polymeric resin composition for use in dental applications or other purposes where radiopacity is desired while at the same time substantially reducing radiopacity. Served. It has been known in the past to use the X-ray absorption ability of thorium in X-ray contrast agent liquids. For example, US Pat. No. 1,918,884 (R. Zellman) describes thorium dioxide sols for use as contrast agents in radiography. U.S. Patent No. 2065718 (T.
Menees and J. Miller) used an aqueous suspension of thorium hydroxide, and US Pat. No. 3,368,944 (S. Sandmark and E. Hagstam) reported that the Describes X-ray contrast agents. However, the inventors believe that thorium oxide alone has never been proposed or used as an X-ray absorbing component in dental filler compositions. The compositions of the present invention retain desirable mechanical and other physical properties in tooth repair composites. Accordingly, objects of the present invention are essentially colorless or transparent, available in microscopic form, and substantially completely insoluble in water or the oral environment. high x
It is an object of the present invention to provide filler compositions suitable for use in dental prosthetic composites containing a small proportion of at least one component capable of absorbing radiation. It is also a main object of the present invention to provide dental prosthetic composites from finely divided inorganic fillers that can be coupled with conventional polymeric resin binders, catalysts and binders therefor. Composites exhibit high absorption of short-wavelength X-ray radiation, such as those used in dental diagnostics, have a relatively low coefficient of thermal expansion, low toxicity, high mechanical strength, and an optical semicontrast that matches the porosity of the tooth. Has transparency. These and other objects of the present invention are of the type formed from a liquid polymerizable organic resin binder and finely divided inert inorganic filler particles; Approximately 3 to 10% by weight of
of thorium oxide (ThO ₂ ) or a mixture of thorium oxide (ThO ₂ ) and tantalum oxide (Ta ₂ O ₅ ). Accordingly, the present invention provides a polymeric resin binder, a catalyst for the binder and an insoluble material which is non-leaching and does not mechanically weaken the composite, and which uses thorium oxide and mixtures of thorium oxide and tantalum oxide. A radiopaque composite material particularly useful as a dental prosthetic material is provided, which contains a fine inorganic filler containing a small amount of a strong X-ray absorbing oxide selected from the following. The filler material is substantially free of soluble or exudable components such as barium and the like. Preferred embodiments of the present invention will be described below. The main part of the filler component of the composite is, for example, amorphous silica, fused silica, quartz, crystalline silica, soda glass beads, ceramic oxides, granular silicate glasses or synthetic crystalline materials, such as β-eucryptite (LiAlSiO ₄ ) may be virtually any siliceous filler particle material, such as. Thorium oxide alone, or a mixture of both oxides, can be added neat to the inorganic siliceous filler and easily mixed uniformly by any suitable compounding technique, including manual or mechanical mixers. The filler composition is in finely divided form that can pass through a 325 mesh screen, for example. Preferably, the filler particles have an average diameter of about 30 microns or less, more preferably about 2-5 microns or less. Unlike conventional radiopaque filler compositions using barium glass, which contain about 35% or more barium glass, the filler used in the present invention contains about 10% or more barium glass.
It is only necessary to contain a small amount of thorium oxide, by weight or less. This represents a substantial economic advantage. This is at least in part because the increased radiopacity of thorium and tantalum compared to barium makes oxides of the latter two elements more effective than barium oxide on a weight basis. For example, in terms of X-ray opacity
0.497 parts Ta ₂ O ₅ and 0.236 parts ThO ₂ in 1 part
Equivalent to BaO. For example, it has been discovered that 1 gram of thorium is equivalent to approximately 4.3 grams of barium in terms of its ability to absorb X-rays. This corresponds to 13.1 g of barium glass (32% barium by weight) per g of thorium oxide (ThO ₂ ) glass and 7.9 g of barium glass per g of Ta ₂ O ₅ . Therefore, the radiopaque compositions used in the present invention need only contain as little as about 3% by weight of thorium oxide, with the preferred range being that this is the only
When used as the line-absorbing component, it is about 3-5% by weight thorium oxide. Filler compositions containing the Combined with a coalescing binder. However, compositions with higher filling rates are particularly useful in dental prosthetic compositions. The weight ratio of filler to polymerizable and other reactive monomers in the binder system is preferably from about 1:1 to about 6:1, particularly from 3:1 to about 5:1. Optimally, the filler comprises about 65-85% by weight of the total filler and binder. There is a wide range of organic polymerizable monomers to choose from, but for dental prosthesis purposes in particular 2,2-propane bis[3(4-phenoxy)-], commonly referred to as BIS-O-MA,
Preferably, dimethacrylates such as 1,2-hydroxypropane-1-methacrylate are mixed with other dimethacrylates. Suitable resin materials include, for example, Jercic, Muller,
U.S. patents by Rockett, Rogers, Dietz et al., as well as U.S. Pat.
Lee, Jr. et al.). Other suitable systems in which tantalum oxide and/or thorium oxide X-ray absorbing filler particles can be used are e.g.
No. 3539533 (Johnson and Johnson), same no.
No. 3709866 (Dentsply Int.), No. 3730947, No. 3751399, No. 3766132, No. 3774305 (Lec Pharmaceuticals), No. 3835090,
No. 3845009, No. 3853962 (Johnson
and Johnson), No. 3860556 (3M Co.) and No. 3991008 (Temin). The composite resin compositions of the present invention contain polymerizable monomers and other reactive monomers (sometimes referred to as "reactive diluents" to reduce the viscosity of the binder to a processable paste); It consists of a liquid resin binder system containing a catalyst or initiator and a promoter or activator (the catalyst and promoter react to form free radicals that catalyze the polymerization reaction) and a finely divided inorganic filler. The binder system also contains stabilizers and UV absorbers to enhance the shelf life of the unpolymerized composite resin composition. The composite can be made, for example, by mixing each of the above components in any conventional manner, preferably after treating the filler with a suitable silane coupling agent, also in a manner well known in the art. Examples of suitable coupling agents include, for example, vinyltrichlorosilane, tris(2-methoxyethoxy)silane, tris(acetoxy)vinylsilane, 1-N-(vinylbenzylaminoethyl)aminopropyltrimethoxysilane-3,3-methacryloxy Includes propyltrimethoxysilane, etc. A silane coupling agent can also be added to the polymeric resin binder prior to addition of the inorganic particulate filler.
Additionally, any of the ingredients can be premixed prior to addition of the remaining ingredients. It is preferred to keep the catalyst and polymeric resin binder separated until just before using the composite. All of these techniques are well known in the art and do not themselves form any part of the present invention. Particular packaging systems are disclosed, for example, in US Pat. No. 3,926,906 (Lec, Jr. et al.). The dental prosthetic composite composition of the present invention comprises about 20 to 50 parts by weight of polymerizable monomer and other optically reactive monomers, about 0.1 to 3.0% by weight each of polymerizable and reactive monomers. of catalyst, about 0.1-2.0% by weight promoter, and about 0
~5% by weight, preferably about 1-4% by weight of a silane coupling agent, and about 20-80 parts by weight, preferably about 50-80 parts by weight of a fine filler composition;
The filler composition contains about 3-10% by weight thorium oxide ( _ThO2 ) or thorium oxide ( _ThO2 ) and _tantalum oxide ( _Ta2O5 ), preferably about 3-7% by weight thorium oxide (ThO2 ₎ . ) or about 3-5% by weight thorium oxide ( _ThO2 ) and about 1-7% by weight tantalum oxide _{( Ta2O5} ). The composite composition may also contain other ingredients, such as polymerization inhibitors, stabilizers, UV absorbers, the nature and amount of which will of course depend on the nature and amount of the polymeric resin binder and the composition. Pigments or dyes, such as iron oxide, cadmium yellow and orange, fluorescent zinc oxide, titanium dioxide, etc., are also used in the cured composite to more closely match the true color of the enamel of the tooth for which it is used. It can be contained in the required amount. EXAMPLES The present invention will be explained below with reference to Examples, but these are illustrative and do not limit the present invention. Example 1 To compare the rate and amount of elution of the radiopaque dental composite of the present invention with that of a conventional radiopaque dental composite using a barium-containing glass filler, a glass sample was a) PH with ammonium acetate
(b) in distilled water and (b) in distilled water. After 1 hour, the aqueous phase was removed and replaced with fresh aqueous phase. The resulting aqueous solution was subjected to atomic absorption spectrometry using a Perkin-Elmer Model 306AA instrument after removing the cured composite. The following results were obtained.

【table】

【table】

[Table] Example 2 Initially, water buffered to pH 7 (1000 g of water
Kimble's Ray in g of ammonium acetate)
When Sorb T-2000 was leached in the same way, the PH was
The temperature rose to 9.5, and more than 500 ppm of barium oozed out in one hour. Example 3 2.4 g ThO ₂ (obtained from JTBaker Chemical Co., Phillipsburg, New Jersey, USA, particle size 325 mesh) and 76.4 g IMSIL A
-10 (amorphous silica with a particle size less than 10 microns obtained from Illinois Minerals Co.) was prepared as a filler for radiopaque composite resins.
The mixture is mixed with a small amount (0.001
gram) of pigment. Using an electric mortar and pestle, apply 12.5 g of BIS-
GMA (purchased from Frecman Chemical Co.), 12.5
g of hexamethylene dimethacrylate (purchased from Sartomer Resins Co.) and 1.2 g of γ
- Thoroughly mixed with 26.2 g of a mixture consisting of methacryloyloxypropyltrimethoxysilane. The resulting paste was divided into two equal parts and 4% of the monomer weight of cumene hydroperoxide was added to one and 2% of the monomer weight of acetylthiourea (purchased from Eastwan Chemicals Co.) was added to the other. . The two pastes were divided into several small portions, thoroughly mixed with a spatula, and the mixture was placed in a Teflon mold to produce a cylinder for compressive strength measurements. Testing (Instron machine) showed that the cured composite test had an average compressive strength of about 3164 Kg/cm ² (45.000 psi). X-ray tests using commercially available dental X-ray equipment
The _ThO2- containing composite contains 50% by weight amorphous silica and 50%
It was shown to have X-ray transparency comparable to a composite material made of % Corning 7724 barium glass by weight.

Claims (1)

Claims: 1. A radiopaque dental prosthetic composite composition of the type made from a liquid polymerizable organic resin binder and fine inert inorganic radiopaque filler particles, comprising: a radiopaque filler; Substantially the only X of the particle
It is characterized by using thorium oxide (ThO ₂ ) or a mixture of thorium oxide (ThO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) in an amount of about 3 to 10% by weight of the total filler as a line-absorbing component. composition. 2 siliceous or ceramic filler particles containing 95 to 97% by weight of radiopaque filler particles; and 3 to 5
A composite composition according to claim 1, comprising % by weight of thorium oxide. 3 siliceous or ceramic filler particles containing 90 to 96% by weight of radiopaque filler particles and 3 to 5
A composite composition according to claim 1, comprising thorium oxide in weight percent and tantalum pentoxide in a range of 1 to 7 weight percent. 4. The composition of claim 1, which is inert and non-leaching in an aqueous environment and is substantially colorless or translucent.