Visible light ray-curable monomeric composition for fastening loose teeth

Abstract: A visible light ray-curable monomeric composition for fastening loose teeth, comprising: a filler component consisting of fine, solid particles having an average size of 0.01 to 100 µm and in an amount of 40% to 85% based on the weight of the total weight of the composition; a polyfunctional monomer component consisting of a radical-polymerizable, polyfunctional monomer; a monofunctional monomer consisting of a radical-polymerizable, monofunctional monomer; and a photopolymerization initiator; having a viscosity of 1,000 to 500,000 cps at a temperature of 25°C, and contained in a light-shielded container.

Description: The present invention relates to a visible light ray-curable (hardenable)monomeric dental adhesion composition. More particularly, the present invention relates to a visible light ray-curable monomeric composition for fastening or fixing loose natural tooth structures to each other or natural tooth structures to dental restoration materials, for example, metallic materials, organic polymeric materials and ceramic materials, with a high adhesion or bonding strength and an aesthetically pleasing appearance. It is known in the field of dentistry that carious tooth structures and defective tooth structures can be restored by using various types of dental restorative materials including metallic materials, for example, gold, silver, platinum, alloy and amalgam materials; organic polymeric materials, for example, polymethylmethacrylate, polycarbonate, cured polyfunctional vinyl polymer, and composite resin materials; and ceramic materials, for example, bore-selenium and other implant materials. The above-mentioned materials do not have a property of an inherent adhesion to the natural tooth structures, and therefore, many attempts have been made to provide dental adhesion (bonding) agents containing at least one monomeric adhesive compound having a polar radical and capable of adhering dental restoration materials to natural tooth structures therethrough. Some of the conventional adhering agents can effect the above-mentioned adhesion by curing an adhesive monomeric component in the presence of a redox curing agent (which is a mixture of an organic peroxide compound and an amine compound) or a photopolymerization initiator. Alternatively, other conventional adhering agents can be cured by mixing an adhesive monomeric component with a powdery filler immediately before application thereof, and curing the resultant mixture in the presence of a redox curing agent. Where a loose tooth structure, e.g., one which is not firmly fixed to an alveolus dentalis due to an alveolitis, for example, pyrrhea alveolaris, is fastened to an adjacent tooth structure, an adhering agent is prepared by mixing and kneading an adhesive monomeric component with a powdery filler comprising an inorganic powder or an organic polymeric powder, outside of the mouth, inserted into gaps between the natural tooth structures, and solidified (hardened) to fix the tooth structures to each other. Where a tooth structure is fixed to an orthodontic device, for example, a metallic orthodontic device, the adhering agent prepared in the above-mentioned manner is inserted into gaps between the tooth structures and the orthodontic device and solidified (cured), and the orthodontic device is further fixed to the tooth structure by a binding wire. When the conventional adhering agent is practically used, however, the mixing of the monomeric component and the powdery filler must be carried out immediately before the application thereof, and outside of the mouth. Thus, the conventional adhering agent is disadvantageous in that, since the mixture of the monomeric component and the filler is easily hardened (cured) within about 4 to about 7 minutes, the mixing operation must be carried out quickly within a very short time. This rapid mixing operation, however, causes the formation of a number of air bubbles in the resultant adhesive layer, and thus this resultant adhesive layer exhibits a poor mechanical strength. Usually, a loose tooth structure is spaced from an adjacent tooth structure through a gap having a relatively large thickness, and to fasten the loose tooth structure to the adjacent tooth structure, the gap must be filled with an adhering agent. Namely, the adhering agent must form a thick adhering layer between the tooth structures. To ensure the formation of such a thick adhering layer, the adhering agent must have a high viscosity. It is difficult to obtain a conventional adhering agent consisting of an adhesive monomeric component alone and exhibiting a high viscosity. Also, even if a high viscosity adhering agent can be prepared by mixing a powdery filler into the adhesive monomeric component, it is very difficult to use the resultant adhering agent having a high viscosity in the mouth, and thus such an agent can be employed only by very skilled dentists. Even if a thick adhering agent layer can be formed from the conventional adhering agent, the resultant thick adhering agent layer exhibits an unsatisfactory poor mechanical strength and surface hardness. In a liquid-powder mixture type conventional adhering agent, the mixing ratio of the liquid component (adhesive monomeric component) to the powder component (filler) can be varied, but an increase in content of the liquid component results in a lower mechanical strength of the resultant adhering layer, whereas the adhesive strength of the resultant adhering layer to the natural tooth structures or artificial devices is increased. Also, an increase in the powder component content results in a lowered adhesive strength of the resultant adhering agent to the tooth structures or artificial devices, whereas the resultant adhering layer exhibits a high mechanical strength. Document US-A-4 762 863 discloses a photopolymerizable dental composition consisting of a composite filler obtained by non-catalytically polymerizing a carboxylic acid monomer with a vinyl monomer in a polymerization system having an inorganic compound disposed therein; a monomer mixture composed of 2,2-bis-[4-(methacryloxyethoxy)phenyl]propane, at least one hexafunctional urethane methacrylate and an ethylenic vinyl monomer diluent. Accordingly, there is an urgent need for the provision of a dental adhering agent having a high adhesive strength to natural tooth structures and artificial dental devices and capable of forming an adhering layer having a high mechanical strength. Preferred embodiments of the present invention may provide: a visible light ray-curable monomeric dental adhesion composition, which composition comprises a monomeric component, a filler and a curing agent, all premixed together, and can be hardened (cured) by irradiating visible light rays thereto with an easy and simple operation; and/or provide a visible light ray-curable monomeric dental adhesion composition, which composition has an enhanced wetting property for the surfaces of natural tooth structures and tooth-restoration material and can finally adhere the natural tooth structures to each other and the natural tooth structure to tooth-restoration materials; and/or provide a visible light ray-curable monomeric dental adhesion composition, which composition forms an adhesive layer having an high mechanical strength and an aesthetically pleasing appearance, between the tooth structures or the tooth structures and the tooth-restoration materials. A visible light ray-curable monomeric composition dental adhesion according to the present invention comprises: (a) a filler component consisting of at least one type of fine, solid particles having an average size of 0.01 to 100 µm, and in an amount of 40% to 85%, based on the total weight of the monomeric composition; (b) a polyfunctional monomer component consisting of at least one type of radical polymerizable, polyfunctional monomer; (c) a monofunctional monomer component consisting of at least one type of radical polymerizable, monofunctional monomer; and (d) a photopolymerization initiator; said monomeric composition having a viscosity of 1,000 to 500,000 cps at a temperature of 25°C; characterized in that; (i) the radical polymerizable, polyfunctional monomer of the polyfunctional monomer component is selected from 2,2-bis[4-(methacryloxyethoxy) phenyl]propane and a hexafunctional urethane acrylate compound of the formula: wherein X is a group of the formula: n is an integer of 1 to 10, and R¹ and R² are each selected from a hydrogen atom and a methyl radical; and the monofunctional monomer component (c) being present in an amount of from 1% to 80% based on the total weight of the polyfunctional monomer component (b) and the monofunctional monomer component (c), and the polyfunctional monomer component (b) and the monofunctional monomer component (c) being present in a total amount of from 15% to 60% based on the total weight of the monomeric composition.-- The monomeric composition of the present invention, wherein all the components (a) to (d) are evenly mixed together, is preferably contained in a container, particularly a light-shielded container. DESCRIPTION OF THE PREFERRED EMBODIMENTS The adhesive monomeric composition of the present invention can be used (hardened) by irradiation of visible light rays and comprises a filler component (a), a polyfunctional monomer component (b), a monofunctional monomer component (c), and a photopolymerization initiator, all evenly mixed together. The filler component (a) preferably comprises at least one-member selected from the group consisting of inorganic powdery materials, for example, metallic elements of Groups I, II, III, IV and V and transition metal elements, and oxides, hydroxides, halides, sulfates, sulfites, carbonates, phosphates, and silicates of the above-mentioned elements; and organic powdery materials, for example, polymethylmethacrylate, polystyrene, epoxy resin, and polyester resin powders. Preferable inorganic materials for the filler component (a) are barium sulfate, barium fluoride, silicon dioxide, aluminum oxide, titanium dioxide, quarty and glass powders, glass beads, glass fibers, silica gel, and amorphous silica. Most preferable inorganic materials are a quartz powder and amorphous silica powder. A preferable organic material for the filler component (a) is a polymethylmethacrylate powder. The solid particles in the filler component (a) preferably have a size of from 0.1 to 100 µm, more preferably from 0.5 to 30 µm. In the adhesive monomeric composition of the present invention, the content of the filler component (a) is from 40% to 85%, preferably from 50% to 85%, based on the total weight of the monomeric composition. When the content of the filler component (a) is less than 40%, the resultant adhesive layer exhibits an unsatisfactory mechanical strength. Also, when the content of the filler component (a) is more than 85%, the resultant monomeric composition has an excessively high viscosity and exhibits an unsatisfactory adhesive strength to the tooth structure and artificial restoration devices. Preferable monomer compounds for the polyfunctional monomer component (b) are 2,2-bis[4-(methacryloyloxyethoxy)phenyl]propane and the monomeric compounds of the formula (I) (u-6HA) wherein n is 6, R¹ is a hydrogen atom, and R² is a methyl radial. Those monomer compounds effectively enhance the mechanical strength of the resultant adhering layer. Preferable monomer compounds for the monofunctional monomer component (c) are 2-hydroxyethylmethacrylate, benzylmethacrylate and 2-methacryloyloxyethylphosphate. Those monomer compounds contribute to the enhancing of the wetting property of the resultant monomeric composition at a surface of a tooth structure or artificial device to be adhered. In the monomeric composition of the present invention, the content of the monofunctional monomer component (C) is preferably from 1 to 80%, more preferably 5 to 60%, based on the total weight of the polyfunctional and monofunctional monomer components (b) and (c). Also, the total content of the polyfunctional and monofunctional monomer components (b) and (c) is preferably from 15 to 80%, more preferably 15 to 60%, based on the total weight of the monomeric composition. The photopolymerization initiator (d) usable for the present invention can comprise any conventional ultraviolet ray-polymerization-initiating compounds, for example, benzophenone, and any conventional visible light ray-polymerization-initiating compounds, but the photopolymerization initiator (d) preferably comprises at least one compound which can initiate the photopolymerization by an irradiation of visible light rays having a wave length of 350 to 1200 nm, which are excluded from a harmful near ultraviolet ray band. Therefore, the photopolymerization initiator (d) preferably comprises a combination of at least one photosensitizing agent which can be excited by radiation rays having a wave length of 350 to 1200 nm, with at least one reducing agent. The photosensitizing agent preferably comprises at least one α-diketone compound, for example, camphorquinone, benzil and diacetyl, which exhibit a high photosensitizing activity and thus are useful for the present invention. In the photopolymerization initiator (d) usable for the present invention, the above-mentioned photosensitizing agent is preferably employed in combination with a reducing agent consisting of at least one tertiary amine compound which effectively enhances the photopolymerization-initiating activity of the photosensitizing agent. The tertiary amine compound can be selected from the group consisting of aliphatic tertiary amine compounds, for example, trimethylamine, triethylamine, and tripropylamine; and aromatic tertiary amine compounds, for example, isoamyl 4-(N,N-dimethylamino)benzoate, hexyl 4-(N,N-dimethylamino)benzoate, heptyl 4-(N,N-dimethylamino)benzoate, octyl 4-(N,N-dimethylamino)benzoate, 4,4-bis(dimethylamino)benzophenone, 4,4′-bis(diethylamino)benzophenone, and 4,4′-bis(dibutylamino)benzophenone. Preferably, the tertiary amine compound is selected from aromatic tertiary amine compounds, more preferably isoamyl 4-(N,N-dimethylamino)benzoate and 4,4′-bis(diethylamino)benzophenone, and those amine compounds are employed preferably in combination with camphorquinone. This combination exhibits an excellent photopolymerization-initiating activity. In the photopolymerization initiator (d), the amounts of the photosensitizing agent and the reducing agent are variable, depending on the types thereof. In the combination of camphorquinone with isoamyl 4-(N,N-dimethylamino)benzoate, preferably the camphorquinone is in an amount of 0.01% to 25%, more preferably 0.05% to 15%, and the isoamyl 4-(N,N-dimethylamino)benzoate is in an amount of 0.05% to 30%, more preferably 0.1% to 25%, based on the total weight of the polyfunctional and monofunctional monomer components (b) and (c). Also, in the combination of camphorquinone with 4,4′-bis(diethylamino)benzophenone, preferably the camphorquinone is in an amount of from 0.005% to 30%, more preferably 0.03% to 20%, and the 4,4′-bis(diethylamino)benzophenone is in an amount of from 0.01% to 25%, more preferably 0.05% to 20%, based on the total weight of the polyfunctional and monofunctional monomer components (b) and (c). To harden the monomeric composition of the present invention in a short time, visible light ray irradiation sources able to generate and irradiate visible light rays having a wave length of from 350 to 1200 nm, for example, a halogen arc lamp, xenon arc lamp, mercury arc lamp, and luminescent discharge lamp, are preferably utilized. To the adhesive monomeric composition of the present invention is optionally added at least one member selected from a polymerization inhibitors comprising at least one member selected from, for example, hydroquinone, methoxybenzophenone, methylphenol, and hydroquinonemonomethylether; antioxidants; ultraviolet absorbing agents, for example, benzophenone; pigments, for example, iron oxides and titanium dioxide; and dyes, if necessary. The adhesive monomeric composition of the present invention has a viscosity of 1,000 to 500,000 cps, preferably 5,000 to 400,000 cps, at a temperature of 25°C. The viscosity can be controlled by controlling the type and content of the filler component (a). If the viscosity is less than 1.000 cps or more than 500,000 cps, the resultant monomeric composition exhibits a poor handling property. In the adhesive monomeric composition of the present invention, all of the components (a), (b), (c) and (d) must be evenly mixed together, and the mixture is preferably contained in one container. The container is shielded from the entry of light therein. There is no limitation to the shape and size of the container, but the container must be able to directly and easily feed the monomeric composition to a tooth structure to be treated. Therefore, the container is preferably compressible or capacity-variable and has a sealable feed opening having an inside diameter of 1 mm to 5 mm. The compressible or capacity-variable container can be a selected from containers, for example, tubes, cylinders, bags and bottles, in which at least a portion of the container wall is made of a flexible or elastic material and which can be easily compressed by the fingers to reduce the inside capacity thereof; and other containers, for example, a cylinder or bottle, having a movable bottom which can be moved toward the inside of the container to push the content in the container toward the feed opening of the container. Note, the container for containing the monomeric composition of the present invention is not limited to the above-exemplified containers. In the conventional adhesive monomeric compositions for fixing natural tooth structures to each other or a natural tooth structure to an artificial restoration device, two or more components must be mixed outside the mouth immediately before applying the composition. The monomeric composition of the present invention, however, does not require this premixing operation and can be directly applied to an object to be fixed, and is easily hardened by irradiating harmless visible light rays thereto. EXAMPLES The present invention will be further illustrated by way of specific examples, which are representative and do not restrict the scope of the present invention in any way. In the examples, the adhering property and adhesive strength of a monomeric composition were tested in the following manner. (1) A fresh cattle anterior tooth was cut by a precision cutter (available under a trademark of Isomet, from Bühler Co) immediately after extraction to expose a fresh enamel surface, and the exposed enamel surface was polished with a water-proof abrasive paper (JIS, No. 1000) under a flow of water. (2) The polished enamel surface was treated with a phosphoric acid type etching agent (made by GC Dental Industry Co.), washed with water, and then air-dried. (3) A circular cylinder-shaped silicon ring having an inside diameter of about 5 mm, a height of about 5 mm and a thickness of about 3 mm (and able to be opened at one side) was placed on the enamel surface, and the inside space of the silicone ring was filled with a monomeric composition. (4) A visible light-irradiation apparatus (available under the trademark (G.C. Light, from GC Dental Industry Co.) was arranged in such a manner that a irradiating opening of the apparatus was close to the upper face of the monomeric composition-filled silicone ring, the visible light was irradiated toward the monomeric composition for 60 seconds to cure (harden) the monomeric composition, the monomeric composition-filled silicon ring was then left to stand for 60 seconds to cure (harden) the monomeric composition, and the monomeric composition-filled silicone ring was then left to stand for about 10 minutes. Then the silicone ring was removed from the resultant adhesive resinous layer to provide a tooth test piece with an adhesive resinous layer. (5) The test piece was stored in water at a temperature of 37°C for a predetermined time, and then a bar consisting of a methylmethacrylate resin and having the same diameter as that of the adhesive resinous layer was adhered to the adhesive resinous layer by a high-speed polymerizing resin (available under the trademark Uni First, from GC Dental Industry Co.). (6) The resultant test piece was subjected to a tensile test under the following conditions, to measure the adhering strength. Tensilometer: Tensilon (Trademark of Toyo Baldwin Co.) Speed of cross head (Stretching speed): 0.5 mm/min Speed of chart: 10 mm/min Full scale: 20 kgw (7) Flexural strength test A stainless steel frame-shaped mold having a length of 30 mm, a width of 2 mm, and a height (thickness) of 2 mm was placed on a horizontal glass plate, filled with an adhesive monomeric composition, and covered by a horizontal glass plate. The visible light irradiation apparatus was arranged so that the light irradiating opening of the apparatus was spaced 1 mm from the covering glass plate, and the light was irradiated to the adhesive monomeric composition through the covering glass plate for 30 seconds. The same procedures as mentioned above were carried out through the bottom glass plate. The resultant hardened resinous test piece was immersed in water at a temperature of 37°C for 24 hours, and then subjected to a flexural strength test under the following conditions. Tester: Bending tester (trademark: IS-500, made by Shimazu Seisakusho) Speed of cross head: 1.0 mm/min Speed of chart: 200 mm/min Span length: 20 mm Full scale: 10 kgw (8) Viscosity measurement A viscosity of the adhesive monomeric composition was measured at a temperature of 25°C in a constant temperature vessel by using a B-type viscometer (type: B8R, made by Tokyo Keiki K.K.) Examples 1 to 5 Preparation of monomeric compositions L-1 to L-8 In Examples 1 to 5, 5 different monomeric compositions L-1 to L-5 were prepared by evenly mixing the filler component (a), the polyfunctional monomer component (b), the monofunctional monomer component (c) and the photopolymerization initiator (d), each consisting of the compounds in the amounts as shown in Table 1, in a dark room using a universal mixer. The resultant compositions exhibited the viscosities at a temperature of 25°C as shown in Table 1. Each of the monomeric compositions L-1 to L-5 was charged in an amount of 3 g in a light-shielded flexible cylinder consisting of a polyethylene resin and having a length of 6 cm and provided with a top opening having an inside diameter of 0.3 cm, and the top opening was closed by a cap. The sealed cylinder was then stored in a thermostatic room at a temperature of 25°C for 3 months. Thereafter, the viscosity of the stored monomeric composition was measured to establish the stability of the monomeric composition during storage. The results are shown in Table 1. Table 1 clearly indicates that all of the monomeric compositions L-1 to L-5 of the present invention exhibited an excellent stability during storage. Adhering strength test and flexural strength test In each of Examples 1 to 5, the adhesive monomeric composition as indicated in Table 2 was subjected to a test of the adhering strength thereof to an enamel surface of a cattle tooth and a flexural strength test of the cured resinous test pieces in the manner mentioned above. The results are shown in Table 2. Comparative Examples 1 to 4 Preparation of comparative adhering monomeric compositions L-6 to L-9 In comparative Examples 1 to 4, four different comparative adhering monomeric compositions L-6 to L-9 of a filler component (a), a polyfunctional monomer component (b), and a photopolymerization initiator (d), each consisting of the compounds in the amounts as shown in Table 3, were tested in the same manner as in Example 1. The viscosities of the resultant compositions are shown in Table 3. Adhering strength test In each of comparative Examples 1 to 4, the comparative monomeric composition as indicated in Table 4 was subjected to the adhering strength test in the manner described above. The results are shown in Table 4. Comparative Examples 5 to 10 Preparation of comparative adhesive monomeric compositions L-10 to L-15 In Comparative Examples 5 to 10, six different comparative monomeric compositions L-10 to 15 were prepared from a filler composition (a), polyfunctional and monofunctional monomer components (b) and (c), and a photopolymerization initiator (d), each consisting of the compounds in the amounts indicated in Table 5, in the same manner as in Example 1. Adhering strength test and flexural strength test The comparative compositions L-10 to L-15 were subjected to the adhering strength test and the flexural strength test, in the above-described manner. The results are shown in Table 6. Examples 6 to 8 In Examples 6 to 8, 3 different adhesive monomeric compositions L-16 to L-18 were prepared, in the composition shown in Table 7, in the same manner as in Example 1. The resultant compositions exhibited the viscosities shown in Table 7. Adhering strength test and flexural strength test The compositions L-16 to L-18 were subjected to the adhering strength test and the flexural strength test. The results are shown in Table 8.

Claims: A visible light ray-curable monomeric dental adhesion composition comprising: (a) a filler component consisting of at least one type of fine, solid particles having an average size of 0.01 to 100µm and in an amount of 40% to 85% based on the total weight of the monomeric composition; (b) a polyfunctional monomer component consisting of at least one type of radical polymerizable, polyfunctional monomer; (c) a monofunctional monomer component consisting of at least one type of radical polymerizable, monofunctional monomer; and (d) a photopolymerization initiator; said monomeric composition having a viscosity of 1,000 to 500,000 cps at a temperature of 25°C; characterized in that; (i) the radical polymerizable, polyfunctional monomer of the polyfunctional monomer component is selected from 2,2-bis[4-(methacryloxyethoxy) phenyl]propane and a hexafunctional urethane acrylate compound of the formula: wherein X is a group of the formula: n is an integer or 1 to 10, and R¹ and R² are each selected from a hydrogen atom and a methyl radical; and (ii) the radical polymerizable monofunctional monomer of the monofunctional monomer (C) is selected from 2-hydroxyethyl methacrylate, 2-methacryloyloxyethyl phosphate, benzyl methacrylate, and 2-ethylhexyl methacrylate; the monofunctional monomer component (c) being present in an amount of from 1% to 80% based on the total weight of the polyfunctional monomer component (b) and the monofunctional monomer component (c), and the polyfunctional monomer component (b) and the monofunctional monomer component (c) being present in a total amount of from 15% to 60% based on the total weight of the monomeric composition.-- The monomeric composition as claimed in claim 1, wherein the filler (a) comprises at least one member selected from quartz powder, amorphous silica powder, and polymethylmethacrylate resin powder. The monomeric composition as claimed in any preceding claim wherein the photopolymerization initiator (d) comprises a combination of at least one photosensitizing agent which can be excited by radiation rays having a wave length of 350 to 1200 nm, with at least one reducing agent. The monomeric composition as claimed in claim 3, wherein the photosensitizing agent comprises an α-diketone compound. The monomeric composition as claimed in claim 4, wherein the α-diketone compound is selected from camphorquinone, benzil and diacetyl. The monomeric composition as claimed in claim 3, 4 or 5 wherein the reducing agent comprises at least one tertiary amine. The monomeric composition as claimed in claim 6 wherein the tertiary amine is an aromatic tertiary amine. The monomeric composition as claimed in claim 7, wherein the aromatic tertiary amine is selected from isoamyl 4-(N,N-dimethylamino)benzoate, hexyl 4-(N,N-dimethylamino)-benzoate, heptyl 4-(N,N-dimethylamino)benzoate, octyl 4-(N,N-dimethylamino)benzoate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4,4'-bis(dibutylamino)benzophenone. The monomeric composition as claimed in any preceding claim wherein the photopolymerization initiator comprises 0.01 to 25% of camphorquinone and 0.05 to 30% of isoamyl 4-(N,N-dimethylamino)benzoate, based on the total weight of the polyfunctional and monofunctional monomer components (b) and (c). The monomeric composition as claimed in any preceding claim wherein the photopolymerization initiator comprises 0.005 to 30% of camphorquinone and 0.01 to 25% of 4,4'-bis(diethylamino)benzophenone.

Inventors: IGE HITOSHI, MAKINO TAKAYUKI, MUKAI NOBUHIRO, IGE, HITOSHI, MAKINO, TAKAYUKI, MUKAI, NOBUHIRO
Applicants: MITSUBISHI RAYON CO, MITSUBISHI RAYON CO., LTD.
Application year: 1989
Main classification: A61K6
IPC codes: A61K6, A61C13