JPS6347682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dental repair materials, and more particularly to dental repair compositions comprising a mixture of a polymerizable binder and a particulate filler.

Composites useful as dental repair materials consisting of liquid, organic, polymeric binders and finely divided inorganic solid fillers are well known.
See, for example, the compositions described in US Pat. No. 3,066,112 (Bowen).
17 to 34% by weight of a thermoset resin, such as a glycidyl methacrylate derivative of Bisphenol A, commonly designated as BisGMA, and 66 to 83% by weight of a filler, as disclosed by Bowen. agent [for example, No. 325 sieve (number 325 sieve) (44
Dental repair composites consisting of clear, colorless fused silica with a particle size fine enough to pass through microns) as a filling material for restorative dentistry (with compressive strengths up to 23,000 p.si) It is accepted.

By definition, these dental repair composites must repair both the function and appearance of defective teeth, thus placing a number of practical limitations on suitable materials. The organic polymerizable binder used in such composites must possess the property of rapid and complete polymerization under the conditions of the oral environment. The repair material must exhibit low polymerization shrinkage, low moisture absorption, low solubility in oral aqueous fluids, low toxicity and satisfactory strength characteristics.
Since these requirements cannot be completely met by the resin itself, repair materials are usually composites, ie reinforcing filler substances are added to the resin to derive a composite with the desired properties.

The addition of fillers to liquid organic binders improves dimension stability, abrasion resistance,
It leads to a repair composite that compares favorably with natural tooth crowns in color, translucency, and strength such that the material maintains its intact appearance and supports the remaining tooth structure during mastication. The translucency of the polymerized dental repair composite should be comparable to the natural translucency of the tooth. This requirement for repair composites is
For aesthetically pleasing restoratives, it is essential, especially in the anterior part of the teeth, where composites are mainly used.
A polymerized composite repair agent that is too translucent will appear as a glass window-like area on the tooth, and conversely a composite repair agent that is not sufficiently translucent or too opaque will appear as an opaque white spot on the tooth. Therefore, if a repair material cannot meet these basic requirements, it is unacceptable because it fails to repair or disguise the natural appearance of the tooth.

The basic physical and optical properties of the organic binders shown in US Pat. No. 3,066,112 are sufficient to lead to composites possessing suitable translucency for natural-like repair agents. The filling material used must have a refractive index that matches the refractive index of the polymerized bonding agent so that the translucency of the repair composite matches that of the natural tooth structure. This translucent property is a characteristic of dental silicate cements (Dental
A.D.A. for Silicate Cement)
Tested according to ADASpec. No. 9 and must provide approximately 35% opacity according to this test (Co. 70).

Accordingly, many of the commercially available dental repair composites are based on the organic binder systems disclosed in the Bowen patent, and many of them typically incorporate quartz particulate fillers. use. The polymer has a refractive index of 1.50 to 1.55, and the quartz filler also has a refractive index of about 1.50 to 1.55. According to some literature, for the best appearance there should be a slight difference between the refractive index of the resin and the filler (difference of about 0.005, but preferably no greater than 0.025).

However, recently, dental repair materials having improved compressive strength have become increasingly desirable. Generally speaking, compressive strength can be increased by increasing the amount of particulate filler present in the composition. Finally, in order to obtain a high filler loading, it is necessary that the filler be in a finely reduced state.

There are numerous patents that teach the use of finely divided particulate fillers in these repair compositions. For example, US Patent No. 3709866; No. 3452437
No. 3629187; No. 3539533; and No.
No. 3751399, reference. U.S. Pat. No. 3,792,531 (Rossi) takes care to exclude even the slightest presence of particles with a diameter of 0.7 microns or less (such particles adversely affect the translucency of the repair agent). teaches repair compositions in which the finely divided particulate filler has a particle size of 0.7 to 30 microns. DE 2403211 describes a dental composition in which all of the finely divided fillers have a diameter of less than 0.7 microns (and preferably smaller). German Patent Publication No. 2405578 has a filler of 0.7
Dental compositions are described that have a maximum particle size of microns. 25% by weight of the total filler, although it is noted that fine particulate glass (particle size less than 5 microns) may be present.
Exists in amounts of up to

Contrary to the prior art, in the present invention the material has a particle size distribution such that the filler-rich portion is in the range 0.7 to 25 microns, while the remainder of the filler is in the size range 0.2 to 0.7 microns. It has been found that by using as a finely divided particulate filler a significant increase in compressive strength can be obtained without sacrificing the desired translucency.

In accordance with the present invention, there is provided an improved dental repair material made by mixing and polymerizing a liquid, organic, polymerizable binder and a finely divided particulate filler; The improvement is that the filler contains 0.7 to 95% by weight of the particles.
25 microns and correspondingly have a particle size distribution such that 5 to 30% by weight of the particles are in the range 0.2 to 0.7 microns in diameter.

The dental restorative materials of the present invention exhibit superior compressive strength and desirable translucency compared to dental restorative materials having particulate fillers with different particle size distributions.

Since the advantages obtained by the present invention are attributable to the particle size distribution of the particulate filler used herein,
Any liquid, organic, polymeric binder can be used in the present invention. There are a wide variety of known useful polymeric binders. For example, the bisGMA type described in US Pat. No. 3,066,112 is quite useful and is currently preferred in the present invention. Such polymerizable binders preferably contain an amount of a reactive diluent (eg triethylene glycol dimethacrylate or tetraethylene glycol dimethacrylate) for the purpose of reducing their viscosity. The amount of diluent typically used for viscosity control is within the range of about 25 to 50% by weight of the polymerizable binder. Liquid polymeric binders are also described in US Pat. No. 3,539,533. Yet another type of useful polymerizable binder is the photopolymerizable type described in US Pat. No. 3,709,866. Other useful polymeric binders are well known in the art.

Finely divided particulate fillers useful in the practice of this invention are those in which 70 to 95% by weight of the particles are
It should have a particle size distribution such that it is in the range 0.7 to 25 microns and accordingly 5 to 30% by weight of the particles are in the range 0.2 to 0.7 microns. Particles larger than 25 microns in diameter are undesirable because they impart greater surface roughness than is desired and they also tend to reduce the compressive strength of the repair material. Particles with a diameter of 0.2 microns or less can be used as conventional thickening agents in dental repair formulations, but they greatly increase the viscosity of the binder prior to curing as well as after curing of the binder. Do not use more than about 5% by weight of filler as this will result in a reduction in the amount of filler which may give a concomitant reduction in compressive strength.

In the particle size distribution used in the present invention, the median particle size is in the range of 1 to 5 microns and is therefore smaller than that used in commercially available dental restorative materials. Others have previously recognized that large amounts of ultrafine particles (e.g., "Cab-O-Sil") can be included in dental restorative agents in addition to relatively larger particles (e.g., 1 to 30 microns). Although suggested, the presence of significant amounts of ultrafine particles also significantly increases the viscosity of the liquid polymerizable binder. After all, it is not possible to incorporate very high loadings of filler into the repair material. As a result, the repair material does not exhibit high compressive strength.

Surprisingly, however, with the wide particle size distribution used in the present invention and the small intermediate particle sizes produced, it is possible to incorporate large amounts of particulate filler into the dental restorative materials of the present invention; It has been found that correspondingly high compressive strengths are obtained. Thus, according to the invention, the particulate filler accounts for 75 to 90% by weight of the repair material. This is surprising in that the fine particles would be expected to greatly thicken the liquid polymerizable binder and thus limit the amount of particulate filler that can be incorporated into the repair agent. The desirable translucency of the dental restorative materials of the present invention is predicted by the presence of a significant amount of particulate filler having a diameter corresponding to the wavelength of visible light (approximately 0.7 microns) imparting significant opacity. This is surprising because it is.

Types of finely divided particulate fillers that can be used herein include those that are commonly available and preferably have a Mon's hardness of about 3 to 8, more preferably 5 to 7.
Useful materials therefore include crystalline quartz (so-called alpha quartz), fused silica, ground glass, synthetic silicic materials, which are currently preferred.
siliceous materials), aluminum oxide, and other fillers well known in the art.

In order to arrive at a dental repair material with suitable translucency (i.e., an optical density of 0.2 to 0.5 as measured by a transmission densitometer), curing, as is known in the art, is required. The refractive index of the particulate filler should be similar to that of the binder resin.

Although the usual technique for producing finely divided particulate fillers is to mill relatively large particles in a mill jar until the desired particle size is obtained, such techniques The use of conventional milling equipment to produce small particles, such as those made from quartz, is not completely satisfactory. Typical mill jars are made of ceramic and therefore have a high alumina content (eg, 70-80% alumina). For example, porcelain balls used in mill jars.
Common grinding media such as ball and borundum also have high alumina content.
flint commonly used as a grinding medium
pebbles) consists of silicon dioxide and also contains trace amounts of contaminants. During normal milling, the particles produced inevitably become contaminated with alumina or other contaminants that have a relatively high refractive index.

Although this contamination does not significantly change the refractive index of particles that are about 1 micron or larger in diameter, the refractive index of particles that are 0.7 microns in diameter (approximately the wavelength of visible light) is changed dramatically. Therefore, small particles produced by conventional ball milling are suitable for use in dental restorative agents because their refractive index differs from that of larger particles (i.e., particles larger than about 1 micron in diameter) of the same material. Highly undesirable for use.

To overcome the inherent drawbacks associated with conventional ball milling techniques, the present invention provides an improved technique whereby very small particles of materials such as quartz can be manufactured without undesirably changing their refractive index. be done. The improved technique is referred to as autogenous milling, ie the milling medium has the same chemical composition as the material being milled into small particles. Additionally, the inside of the mill jar is preferably lined with a strong durable organic coating (eg, polyurethane) free of pigments and other inorganic contaminants. Milling is done in a dry state since wet milling of the particles produces a narrower particle size distribution than required in the present invention. After milling is complete, the particles are heated at high temperatures to remove any possible contaminants.

Thus, for example, to produce quartz particles with a desired particle size distribution, quartz crystals (approximately
0.5 to 5 cm) is used as the grinding medium and crushed quartz foot is used as the feed material. placing the materials in a mill (preferably a vibratory mill with a lined interior as described above) and continuing the grinding in dry conditions for several hours, after which the finely divided particulate quartz is recovered; Then, it is heated to a high temperature (for example, 900 degrees Celsius).

The finely divided particulates used in the repair agent are preferably a keying agent to improve the bond between the filler and the binding resin and to reduce moisture sensitivity within the filler-resin. must be processed. There are a variety of known keying agents useful for this purpose. Preferred keying agents are ethylenically unsaturated organosilanes. See, for example, the locking agents and techniques described in U.S. Pat. No. 3,066,112 (Bowen). Other suitable locking agents are described in US Pat. No. 3,539,533.
Particularly preferred keying agents for use in the present invention include gamma-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane. Other useful locking agents are well known in the art.

One method of treating finely divided particulate fillers with a locking agent is described in U.S. Pat. No. 3,862,920, in which γ-methacryloxypropyltrimethoxysilane is dissolved in a water/acetone formulation. . The particulate filler is then mixed with the silane solution to form a slurry. Water and acetone are then removed at 100°C and the treated filler is then heated at 125°C for 2 hours. Other techniques for treating particulate fillers with locking agents include dissolving the silane in toluene (e.g., forming a 50% solution), then mixing the solution with the particulate filler, and subsequently forming a wet cake.
Includes drying at 115 degrees C.

The composite dental restorative materials of the present invention are typically provided as a two-part system. Preferably, the polymerizable binder is separated into two equal or approximately equal volume portions, and the desired particulate filler is also separated into two portions and then mixed with the binder to form two
Form two pastes. The catalyst for the polymerizable binder is contained in one paste part and the activator in another paste part. Thus, each of the two pastes is quite stable and can be packaged separately. At the time of use, equal volumes of both pastes are then thoroughly mixed together and placed into the cavity of the tooth to be filled. Curing of the bonding agent then occurs in situ to provide a dental repair with high compressive strength and desired translucency.

The invention is further illustrated by the following non-limiting examples, in which the word "parts" refers to parts by weight unless otherwise indicated.

Example 1 Crude alpha quartz is heated to 1000 degrees Celsius and then cooled by pouring the heated quartz into water. The resulting crushed frit is dried at 150°C and then cooled. This crushed frit is then used as a grinding medium.
pebbles) (0.5-5 cm in diameter) into a lined vibratory mill. The grinding mill itself is commercially available from Sweco, Inc. as the Model "DM-3".
Prior to use, the internal surfaces of the mill were coated with a tough polyurethane polymer (“Adiprene L”).
167“, commercially available from EIDupont and cured with MOCA]
It is lined with.

The crushed frits are ground for 48 hours to reduce particle size. The resulting powdered quartz is then heated to 900 degrees Celsius to remove organic impurities.

Cool the finely divided filler and heat it to 325
Pass through a mesh nylon sieve. The resulting powdered quartz has the following particle size distribution: Weight % finer than particle diameter (microns) 21 100 8.8 90 5.4 75 2.5 50 1.7 40 0.9 25 0.7 20 0.5 15 0.2 2 Example 2 of Example 1 A quantity of the quartz particles produced according to the method was added to 4% by weight (based on the weight of the quartz particles) of a colloidal silica thickener [“cab-O-sil”].
-Sil) M-5", Cabot
(commercially available from Powder Corporation) and fill it into a conventional powder blender. The materials were thoroughly mixed and then 8% by weight (based on the total weight of quartz particles and colloidal silica) γ in toluene.
-methacryloxypropyltrimethoxysilane
Add the 50% solution with further mixing. After thorough mixing, spread the resulting wet cake into a thin layer and mix 115
Dry for 1 hour at 50°C and then cool.

Example 3 A two-part paste dental restoration is prepared as follows: N,N-di-(2-hydroxyethyl)-p-
The resin binder (containing the activator therefor) is prepared by adding 2.5 g of toluidine to 48.8 g of triethylene glycol dimethacrylate and then mixing until a solution is obtained. The solution is then thoroughly mixed with 46.5 g of bisGMA (ie, the glycidyl methacrylate derivative of bisphenol A). 525 g of the treated particulate filler prepared in Example 2 are then slowly added with stirring until a homogeneous paste is obtained.

A resin binder (containing catalyst) is prepared by dissolving 1.1 g of benzoyl peroxide in 48.7 g of triethylene glycol dimethacrylate. Next, add 49.3g of BisGMA to the resulting solution.
Mix thoroughly. A small amount of polymerization inhibitor (eg, substituted phenol) is also added. Next, example 2
Slowly add 525 g of the treated particulate filler prepared in above with stirring until a homogeneous paste is obtained.

Example 4 A tooth cavity is repaired by first mixing equal volumes of the two pastes prepared in Example 3. Mixing is typically done with a small wooden, plastic or porcelain spatula and takes only about 20 seconds. The repair material is then placed into the tooth cavity where the binder polymerizes in situ (in approximately 2 minutes) to form a tooth repair with high compressive strength.

Add another sample of the hardened dental repair agent to water (37 degrees C).
Soak in water for 24 hours and then test for compressive strength.
A value of 55000p.si is observed.

Example 5 A test specimen of a dental repair agent is prepared as follows: Equal volumes of the two pastes of Example 3 are thoroughly mixed and a polyester film (250 microns thick) is prepared.
Ring mold (20mm diameter) placed on top of
immediately. The top of the annular mold was then covered with another piece of polyester film (250 microns thick).
Then the entire mold assembly
Place in the press. The device is then pressurized to 20,000 psi or more for 1 second or less and the pressure is maintained for at least 5 minutes. The pressure is then stopped and the test disc is removed from the mold. Mix the paste, put the mixture into the mold, and pour it
The step of applying pressure to 20,000 p.si or more must be carried out for one minute or less.

EXAMPLE 6 The test disc produced in Example 5 was tested using a conventional transmission densitometer (Macbeth type TD501) with an optical filter in the visible region (adjusted to zero reading) and also half of the dental restorative material. (adjusted to transparent range). Place it on the stage.

Measurement of the opacity of the test disc gave a reading of 0.25 optical density units (which means that the dental restorative has acceptable translucency).

Example 7 Crude alpha quartz was heated to 1000 degrees Celsius and cooled by pouring the heated quartz into water. The resulting crushed frits are loaded into a lined vibratory mill with quartz crystals as milling medium. The mill is also filled with the same weight of water as the crushed frits. Next to the crushed frit
Grind for 26.5 hours. The resulting slurry is pumped from the mill, dried in a forced air oven heated to 900 degrees Celsius, and then sieved through a 325 mesh nylon screen.
The powdered quartz produced has the following particle size distribution: Weight % finer than particle diameter (microns) 11 100 7.4 90 5.2 75 3.4 50 2.8 40 2.0 25 1.6 20 1.1 10 0.8 5 0.7 2 All described in Example 2 In this manner, ground quartz is blended with colloidal silica and treated with a silane coupling agent. Using the resin formulation of Example 1, it was observed that only 317 g of filler material in this example (compared to 525 g of filler in Example 3) could be incorporated into the resin. Attempts to incorporate additional fillers have resulted in dry mixtures unsuitable for use as dental restorative materials.

The test specimens were tested according to the American Dental Association specification for compressive strength.
Specification) No.9.
After storage for 24 hours at 37 degrees C., the test specimens crumbled and developed a compressive strength of 45,000 p.si. This polymerized dental repair composition gave a Barcol Hardness value of 80 after storage for 24 hours at 37 degrees Celsius in distilled water.

This example demonstrates that a narrow particle size distribution for a particulate filler inherently limits the amount of filler that can be incorporated into a dental restoration material (and thus has a lower compressive strength).

Claims (1)

Claims: 1. A composite dental restorative material produced by mixing and polymerizing a liquid, organic, polymerizable binder and a finely divided particulate filler, comprising: The filler accounts for 70-95% by weight of the particles
composite dental restorative material, characterized in that it has a particle size distribution such that 5 to 30% by weight of the particles are in the range 0.2 to 0.7 micron, and accordingly 5 to 30% by weight of the particles are in the range 0.2 to 0.7 micron. . 2. Clause 1, characterized in that 75-85% by weight of the particles are within the range of 0.7-20 microns and correspondingly 15-25% by weight of the particles are within the range of 0.2-0.7 microns. Composite dental restorative materials in accordance with. 3. A composite dental restorative material according to clause 1, wherein the particles are alpha quartz. 4. The particulate filler is about 75-90% by weight of the repair material.
A composite dental restorative material according to paragraph 1, consisting of: 5. A composite dental restorative material according to clause 1, wherein the polymerizable binder consists of a glycidyl methacrylate derivative of bisphenol A. 6. A composite dental restorative material according to clause 1, wherein the binder further contains a reactive diluent.