FI102946B - Prepreg, a process for its preparation, a composite based on the aforementioned prepreg and its use - Google Patents

Description

This invention relates to a process for the preparation of a polymer pre-impregnated fiber product, namely a prepreg. The invention further relates to a novel prepreg and a process for making fiber reinforced composite products using said prepreg, novel composites and their use.

The publications and other material used to explain the background of the invention, in particular the individual cases detailing the practice, are disclosed in the references.

10 Polymeric products used in dentistry are easily damaged by oral conditions. For example, cracking of removable dentures after using the prosthesis for a few years is common (1-4). Due to the great need for prosthetic repair, it should be possible to use the reinforcement used in the prostheses 15 both for the repair of the old prosthesis and for the manufacture of the new prosthesis. Today, dentures are reinforced with metal bodies, such as wires and beams (5-7), which are placed in the denture polymer. However, metal reinforcements have not been able to increase the prosthetic strength sufficiently and the development of a new easy-to-use fiber reinforcement has been studied. Prior to the present invention, there has been no fiber reinforcement meeting the requirements of dentistry and dental technology, although a fiber tape product is sold for this purpose (RibbondR, Ribbon Inc., Seattle, WA, US 5,176,951).

Known polymer-fiber composite materials (composites) for dental prosthetic use have been prepared by dipping a bundle of fiber, tape or tissue, methyl methacrylate (MMA) monomer, or a mixture of polymethyl methacrylate (PMMA) powder and MMA. However, the composite thus prepared for dental prosthetic use is unsuitable because: 102946 2 1) insufficient adhesion between the fibers and PMMA, especially cold-polymerized PMMA used for prosthetic repair (8), 2) fibers not sufficiently wetted with PMMA (9 - 11), 5) 3) the fibers spread in the prosthesis during the manufacture of the prosthesis where they may be detrimental (12), 4) the fibers are difficult to use in the dental laboratory (13), and 5) the fibers on the surface of the prosthesis can mechanically damage the soft tissues of the oral cavity.

The fiber bundle or tissue may be pre-moistened with a polymer. Such a prepreg is called a fiber-polymer prepreg. At least three methods for preparing a thermoplastic fiber prepreg are described in the literature (15): 1) in situ polymerization in which monomer is injected into the pulp, 2) a film compression method wherein the fibers are compressed between polymeric laminates, and 3) a fiber powder coating process wherein the fibers are thermoplastic powder before melting the powder to the fibers.

However, the methods described above do not meet the dental requirements for the preparation and use of prepreg. Due to the cure shrinkage of the polymer 25, in situ polymerization causes the fibers to remain trapped in the cavity, which is filled with saliva and microbes in the mouth. In the film pressing process, the degree of wetting of the fibers by the polymer is low, which also causes voids in the composite structure and weakens the composite. In the powder-30 coating process, the thermoplastic powder is melt-bonded to the fibers to form a dense composite material that is difficult to plasticize in the manufacture of a prosthesis. Thus, none of the fiber composite fabrication methods commonly used in plastic technology are suitable for the manufacture or repair of dentures.

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Clinical dentistry and dental technology requirements for prosthetic reinforcement prepreg are: 1) the prepreg must be easily deformable to shape the anatomical structures of the oral cavity, i.e., the prepreg must be plastic at room temperature when used in the manufacture or repair of the prosthesis; 3) the polymer of the prepreg should polymerize while the polymer surrounding it is polymerized; 4) the polymer matrix of the prepreg must react chemically with either the so-called "polymer" matrix. and (5) the fibers in the prepreg must adhere to both the so-called "cold" and "hot" polymerizable polymer;

15 cold polymerizable so-called. heat-polymerizable polymer.

One of the objects of the invention is to satisfy the above requirements 1) to 5).

Another object of the invention is to use the invented prepreg 20 in the manufacture of a fiber composite. Such composites can be used in technology and in particular in medicine and dentistry.

The features of the invention are apparent from the independent claims.

In one aspect, the invention relates to a process for the preparation of a polymer impregnated fiber product or prepreg. According to this method, either: (i) (a) the fibers are pulverized with a powder containing at least one thermoplastic polymer and optionally an agent capable of initiating the polymerization reaction of said polymer at a later desired time, (b) adding a solvent capable of dissolving said polymer but incapable of initiating a polymerization reaction of said polymer; and c) evaporating the solvent; or ϋ) a) dissolving a powder containing at least one thermoplastic polymer and optionally an agent capable of initiating the polymerization reaction of said polymer; at a later desired time, in a solvent capable of dissolving said polymer but incapable of initiating the polymerization reaction of said polymer; and b) contacting the fibers with the solution obtained in the preceding step; and c) evaporating the solvent.

Although the prepreg can be made into a continuous ribbon shape, in many applications of the prepreg, it is desirable to prepare the prepreg in the shape required for the intended use, such as a toothed arch. In this case, the intermediate obtained in step a) is placed in the mold of the desired shape before the solvent is added. After evaporation of solvent 20, the prepreg is removed from the mold.

According to a preferred embodiment, the surface of the fibers is pretreated to facilitate adhesion of the polymer to the fibers, after which the surface-treated fibers are covered with polymer powder. Preferably, the fiber surface is treated with a substance that aids in bonding the polymer to the fibers before the fibers are coated with polymer powder.

In another aspect, the invention relates to a prepreg for use in medicine or dentistry, which is porous and easy to form at room temperature after the addition of a plasticizer, said prepreg consisting of fibers and a thermoplastic polymer. It is characterized in that the polymer is present between the individual fibers and that it is applied between the fibers in the form of a solution in which a solvent which is capable of dissolving 35 of said polymers but which is not capable of initiating the polymerization reaction.

In a particularly preferred embodiment, the fiber of the prepreg is glass fiber and the polymer is polymethyl methacrylate (PMMA), ethylene glycol dimethacrylate (EGDMA), 2,2-bis [4-5 (2-hydroxy-3-methacryloxy) phenyl] propane (BIS GMA), or hydroxyethylene methacrylate. (HEMA) and the fiber surface is treated with a silane compound, preferably gamma-meta-cryloxypropyltrimethoxysilane.

In yet another aspect, the invention relates to a process for making a fiber reinforced composite, wherein the composite consists of a cured polymer mass and a prepreg. The method utilizes the prepreg of the present invention. In this case, the manufacturing process comprises the following steps: - adding a plasticizer to said optionally preformed prepreg, - shaping the plasticized prepreg into the desired shape, - covering the prepreg with a non-cured polymer or a mixture of said polymer and monomer, and simultaneously. Characterized in that a prepreg according to any one of claims 1 to 10 is used.

The reinforced composite can be used as such or alternatively it can be used as a bulk product for the production of pieces of the desired shape. Composite bulk material can be used to process dental fillings and dental implants.

In yet another preferred embodiment, the uncured polymer of the composite is the same as the polymer used in the prepreg.

The invention further relates to a fiber reinforced composite consisting of a cured polymer mass and a prepreg, wherein said prepreg is plasticized by wetting it with a monomer, formed into the desired shape and covered with a non-cured polymer of the composite, and polymerized in the prepreg. Characterized in that said prepreg is a prepreg according to any one of claims 1 to 10.

Said composite can be used in various technical applications. However, it is particularly suitable for medical or dental applications such as prosthetic, orthodontic or orthopedic products; removable prosthesis body parts, prosthetic clips or precision clips; permanent or temporary fixed prostheses including dental and implant-borne prostheses; dental or medical implants; tooth root canal fillings; roots, pillars, fillings, crowns, mouth guards or the like.

Figures IA-1C illustrate the use of a prepreg in repairing an entire denture,

Figures 2A and 2B show two examples of fiber orientation in repaired dentures (Figure 2A is a complete denture and Figure 2B is a partial upper tooth prosthesis), and Figure 3 shows the flexural strengths of the GF-PMMA composite.

Fibers suitable for use in the present invention are either organic or inorganic fibers. The choice of fibers is highly dependent on the application of the composite. Fibers that have already been tested for dental applications include electrical glass (10), high strength glass (16), carbon / graphite (12, 17, 18), aramid fibers. (19) and polyethylene (ultra-high-modulus polyethylene) fibers (8, 13, 20-23). The use of carbon / graphite fibers in dentistry is problematic due to the black color of the fibers. Organic 7102946 fibers have been reported to have poor adhesion to polymers used in dentistry (8). Fiberglass appears to best meet the cosmetic and adhesive requirements of dentistry.

5 The fibers may take different forms. Examples include fiber bundles, woven fiber bundles, woven rugs, other fiber rugs, reinforcing particles and fiber particles (fillers). The choice of fiber type depends on the application of the composite.

Combinations of different fiber types can also be used in the com-10 position.

Any thermoplastic polymer may be used as the polymer for Prepreg. It is desirable that the polymer used in the prepreg is the same as the uncured polymer surrounding the prepreg. The preferred polymer for dental use is polymethyl methacrylate (PMMA), either hot or cold polymerizable PMMA. Heat-curing PMMA is polymerized in a 70-100 ° C water bath. The polymerization is initiated by an initiator such as benzoyl peroxide (24). The heat-polymerizable PMMA can also be polymerized by microwave energy. Autopolymerizing PMMA (Cold Polymerizing PMMA) is polymerized at a lower temperature (35-50 ° C) than heat-polymerizing PMMA and therefore, an activator such as dimethylparatoline (24) is required to initiate the reaction. Other suitable poly-25 mers are, for example, ethylene glycol dimethacrylate (EGDMA), 2,2-bis [4- (2-hydroxy-3-methacryloxy) phenyl] propane (BIS GMA), polyethylene terephthalate glycol (PETG), poly-1,4- cyclohexylene dimethylene terephthalate glycol (PCTG), hydroxyethylene methacrylate (HEMA), or the like.

The amount of fibers and polymer in the prepreg must be chosen such that the prepreg has a sufficiently porous structure after evaporation of the solvent used in the preparation. The high porosity of the prepreg is advantageous because it allows the solution used to plasticize the prepreg to rapidly penetrate the entire prepreg. When using glass fibers and PMMA, suitable porosity for the prepreg is obtained when the amount of fiber and the amount of PMMA are equal.

If necessary, the fiber surface may be treated to adhere to the polymer used in the composite. The coupling agent is selected according to the type of fiber and the chemical composition of the polymer matrix. In dentistry, silane compounds are commonly used as adhesives to increase adhesion between glass fibers and PMMA. A particularly suitable silane compound for this application is gamma-methacryloxypropyltrimethoxysilane (MPS). The adhesion of carbon / graphite fibers to the polymer matrix can be improved using oxidation, irradiation or silanization techniques. Attempts have been made to increase the adhesion of polyethylene fibers to the polymer matrix by the so-called "surface" of fibers. plasma treatment. However, results have been modest (21).

According to a preferred embodiment of the invention, the adhesive-20 precursor is prepolymerized on the fiber surface before the fiber is treated with polymer powder. The prepolymerization of the material on the surface allows good adhesion with both hot and cold polymerizable PMMA. In the known processes **, the polymerization of the silane on the fiber surface occurs simultaneously with the polymerization of the heat-polymerizable PMMA. There are no reported data on the successful use of silane with cold polymerized PMMA.

The initiator of the polymerization reaction, the initiator, is added to either the polymer in the prepreg or the fluid (plasticizer) used to plasticize the prepreg. Suitable initiators are any chemical that initiates the polymerization reaction. The most common initiators are peroxides such as benzoyl peroxide.

The solvent used in the preparation of Prepreg may be any solvent which is capable of dissolving the polymer but which does not initiate the polymerization reaction. Tetrahydrofuran (THF) is an example of a suitable solvent. The dissolution of the polymer and subsequent evaporation of the solvent ai-5 provide a highly wetted fibrous product which, as described in the following examples, gives excellent strength properties to the final composite. Preferably, the solvent must be volatile as it allows the porous structure of the prepreg to be formed.

Before molding the prepreg, a monomer of the polymer in the prepreg or another monomer may be used. Preferably, the same monomer is used. When the polymer is PMMA, a suitable monomer is methyl meth-15 tacrylate (MMA).

The invention will now be described by way of example. The examples illustrate the use of the invention in dental prosthetic applications, although the invention has other applications in medicine and technology.

Example 1

Preparation of Prepreg

Continuous E-glass fiber bundles (Ahlström, Karhula, Finland) were purified with 1.5 mol / L sulfuric acid (H2SOA), rinsed with distilled water and dried at + 22 ° C for 48 25 hours.

The fiber surface was treated with gamma-methacryloxypropyltrimethoxysilane (MPS) (A174, Union Carbide Chemicals, Versoix, Switzerland) to increase adhesion between the fibers and the polymer (PMMA). Diluted MPS (30% MPS, 70% 30 methanol) was prepolymerized on the glass fiber surface at +100 ° C for two hours. Alternatively, commercial surface-treated glass fibers may be used.

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The silanised glass fibers were pulverized with a heat-polymerizable polymethyl methacrylate (PMMA) powder (Pro Base Hot, Ivoclar, Schaan, Liechtenstein) to which the manufacturer had added a benzoyl peroxide initiator to initiate the polymerization-5 reaction. The amount of PMMA powder in the prepreg was as high as the glass fiber.

The desired amount of powdered glass fibers was placed in an open mold having a shape of indentation similar to that of the prepreg to be manufactured. The pulverized glass fibers were wetted with tetrahydrofuran (THF), a solvent that dissolves PPMA but does not initiate the PMMA polymerization reaction. At this point, the PMMA that was bonded bound the individual glass fibers together to form a rigid prepreg of the desired shape. The solvent (THF) was allowed to evaporate and finally the prep-15 reg was removed from the mold and packed for use.

According to another method, a prepreg can be prepared by dissolving the desired amount of PMMA in THF, dipping the fiber bundle or woven product into the mixture, or pulling the fiber bundle or woven product through the mixture. The ratio PMMArTHF 20 should be optimized to provide a porous glass fiber PMMA prepreg that can be readily wetted and plasticized with MMA when the prepreg is used.

Similarly, Prepreg was prepared from PMMA (Pro Base Cold, Ivoclar, 25 Schaan, Liechtenstein) autopolymerizing.

Example 2 Using Prepreg as a Prosthetic Reinforcement in the Production of a New Prosthetic

The acrylic resin denture was made from hot-polymerizable PMMA by acrylic dough extraction technique. The weaknesses of the prosthesis were reinforced with the prepreg of Example 1 as follows: 102946 11 1) After the test pressing of the PMMA dough, a dent in PMMA was pressed with a plastic strip the size of the pre-preg.

2) The prepreg was plasticized by moistening it with a thermoplastic PMMA monomer liquid, followed by placing the prepreg in an indentation in an acrylic resin.

3) The final pressing of the acrylic resin dough in the mold was done by conventional prosthetic technique (25).

4) Prepreg's PMMA was polymerized in a water bath, whereby the 10 prepreg's PMMA cured simultaneously with the PMMA dough. The end product was a denture which was reinforced with a continuous and highly targeted fiber reinforcement covered with a layer of uncured PMMA.

Example 3 Using Prepreg for Prosthetic Repair

A gypsum model was made from a split denture as described in the literature. The prosthesis (Figures 1A-1C) was then milled into a groove 10 20 of a prepreg 11 made of cold-polymerizable PMMA and fiberglass to the desired reinforcement site. Prepreg 11 was plasticized (Figure 1C) by moistening cold polymerizable PMMA with monomer fluid and the plasticized prepreg was placed in a milled groove. The groove was filled with cold polymerized PMMA dough, which was allowed to polymerize in a water bath while the PMMA in the prepreg was polymerized. A repaired prosthesis with a directed fiber reinforcement was obtained (see Figures 2A-2B).

Example 4

Using Prepreg as a Graft Protein Backbone Material 30 Prepreg was plasticized with the polymer matrix monomer fluid contained therein and placed over an insulated gypsum model in the area within which the desired graft prosthesis body extends. The fibers of Prepreg were oriented perpendicular to the probable fracture lines of the prosthesis. The surface of Prepreg was coated with uncured PMMA powder. Alternatively, the surface of the prepreg could be covered with a mixture of PMMA powder and MMA liquid (i.e., PMMA dough). The template was then placed on a polymerization machine for PMMA polymerization. After polymerization, the composite body was ready for conventional further preparation of a graft prosthesis.

Example 5

Use of Prepreg as a removable prosthesis coating

The prepreg, which was made of tooth colored PMMA and prepared to the correct shape according to the dentition in question, was plasticized with the monomer fluid corresponding to the prepreg polymer matrix (PMMA). The plasticized prepreg was placed on the surface of the prosthetic retention tooth and the shaft portion of the clip was extended to the saddle portion of the prosthesis where the clip was attached. Prepreg was coated with a thin layer of tooth-colored PMMA powder prior to polymerization of PMMA. Alternatively, the prepreg could be coated with a tooth colored PMMA paste prior to polymerization.

Example 6

Use of Prepreg in the manufacture of permanent, long-term temporary and temporary bridge prosthesis. A prepreg consisting of colorless or tooth colored PMMA (or alternatively polybutyl methacrylate or polyethyl methacrylate, etc.) was softened with monomer fluid. The plasticized prepreg was placed in a silicone bridge prosthesis mold half filled with a mixture of PMMA powder and monomer fluid.

t ', The plasticized prepregs were covered in a mold with the layer em.

acrylic powder-liquid mix and the mold was placed on a sanded gypsum model 102946 13. After PMMA polymerization, the bridge prosthesis was completed by conventional dental laboratory techniques.

The bridge prosthesis consists of either unidirectional continuous fiberglass fibers which reinforce the intermediate teeth of the bridge, or alternatively fiberglass or short fiberglass fibers which reinforce the crown units of the bridge.

Example 7

Properties of Fiber Composite Made from Prepreg Prior to the present invention, the use of fibers in dental prostheses achieved a low degree of fiber wetting (impregnation) with PMMA. The degree of fiber impregnation is defined as the ratio of the number of fibers surrounded by PMMA to the total fiber content of the composite. In the process described in the literature 15, where the fiber bundle is moistened with a mixture of monomer liquid and polymer powder, an impregnation degree of from 0.4 to 0.8 is achieved. The lower the degree of impregnation of the fiber bundle, the more fibers there are in the polymer. Using a prepreg of the present invention to produce a composite consisting of E-glass fiber and PMMA, a degree of impregnation of 0.91 was obtained in heat-polymerizable PMMA and 0.98 in cold-polymerized PMMA. The degree of impregnation was not affected by the amount of fibers in the polymer.

Unidirectional continuous fibers made by a conventional method and a prepreg of the invention. The mechanical properties of the reinforced dental PMMA composite in bending are shown in Table 1 and Figure 3. The fiber contents of the test specimens used correspond to the maximum fiber contents that can easily be used in the conventional method and the inventive prepreg method.

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The fatigue strength of a fiberglass reinforced removable partial prosthesis in a bend simulating chewing activity (150 N force every 300 ms at +37 ° C in water) was 15 times greater than the fatigue strength of a conventional metal reinforced prosthesis 5. The impact strength of the PMMA glass fiber composite prepared by the method described herein was 70 kJ / m2 (Charpy type test, WPM Leipzig, Leipzig, Germany). The impact strength is significantly higher than that of PMMA reinforced with wire. The occlusal force required to break an acrylic bridge prosthesis of three dental units was 91 N. When a similar bridge prosthesis was strengthened with the prepreg described in the invention, the force required to break the bridge increased to 350 N.

The conversion of the MMA monomer to the polymer (PMMA) (degree of conversion) in the prepreg-strengthened and non-reinforced moieties was equal when the amount of residual monomer was measured (HPLC-liquid chromatography method according to ISO 1567). The cured PMMA's water absorbency and Liu slope were also ISO standard.

Table 1 Bending Strength (MPa) and Bending Module (GPa) of a test piece reinforced by a conventional technique and a prepreg according to the invention. The tests are performed in accordance with ISO 1567 as a three-point bend test.

Bending Strength Bending Module 25 Unhardened PMMA 89.1 2.83 GF-PMMA Composite (Conventional Technique) 231.2 7.12 GF-PMMA Composite (Prepreg Technology) 335.0 12.56 It will be understood that The methods can be applied in many forms, only a few of which are described herein. It will be apparent to one skilled in the art that other uses exist and do not depart from the scope of the invention. The embodiments described are thus illustrative in nature and do not limit the invention.

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102946 17 11. Williamson DL, Boyer DB, Aquilino SA, Leary JM. Effect of polyethylene fiber reinforcement on strength of denture base resins polymerized by microwave energy. J Prosthet Dent 1994; 72: 635-8.

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Claims (16)

102946 19 Patent Claims ET A process for preparing a polymer pre-impregnated fiber product, i.e. a prepreg, wherein said prepreg is porous and easy to form at room temperature after the addition of a plasticizer, characterized in that either 5 i) a) is covered with a powder containing at least one thermoplastic polymer and optionally having the ability to initiate the polymerization reaction of said polymer at a later desired time, bj adding a solvent 10 capable of dissolving said polymer but incapable of initiating said polymerization reaction to the composition obtained in a), and c) evaporating the solvent, or ϋ) 15 a) dissolving a powder containing at least one thermoplastic polymer and optionally an agent having the ability to initiate a polymerization reaction of said polymer at a later desired time in a solvent capable of dissolving said polymer but not capable of dissolving said polymer. ynnistämään polymerization reaction of said polymer, and b) contacting the fibers with the previous step. and c) evaporating the solvent. Process according to Claim 1, characterized in that the product obtained in step i) a) is placed in a mold before the addition of a solvent. Method according to claim 1 or 2, characterized in that the surface of the fibers is treated to facilitate the adhesion of the polymer 30 to the fibers, after which the surface-treated fibers are covered with polymer powder. Method according to claim 1, 2 or 3, characterized in that the fiber is glass fiber. 102946 20 5 GMA), or hydroxyethylene methacrylate (HEMA), and the fiber surface is treated with a silane compound, preferably gamma-methacryloxypropyltrimethoxysilane 11a. Process according to one of Claims 1 to 4, characterized in that the polymer is polymethyl methacrylate (PMMA), ethylene glycol dimethacrylate (EGDMA), 2,2-bis [4- (2-hydroxy-3-methacryloxy) phenyl] propane (BIS). 6. A prepreg for use in medicine or dentistry, which is porous and easy to form at room temperature after the addition of a plasticizer, said prepreg consisting of fibers and a thermoplastic polymer, characterized in that the polymer is present between the individual fibers and spread between the fibers. in the form of a solution in which the solvent which is capable of dissolving said polymer but which is not capable of initiating the polymerization reaction of the polymer is evaporated off. A prepreg according to claim 6, characterized in that it contains a substance which has the ability to initiate the polymerization reaction of said polymer at a later desired time. A prepreg according to claim 6 or 7, characterized in that the fibers have the form of fiber bundle, woven fiber bundle, woven mat, other fiber mat, short fibers, reinforcing particle or particle, or a mixture of the above. . A prepreg according to claim 6, 7 or 8, characterized in that the fiber surface is treated to promote binding of the polymer. Prepreg according to any one of claims 6 to 9, characterized in that the fiber is a glass fiber, the polymer is polymethyl methacrylate (PMMA), ethylene glycol dimethacrylate (EGDMA), 2,2-bis [4- (2-hydroxy-3-methacryloxy) phenyl]. 21l] -propane (BIS GMA), or hydroxyethylene methacrylate (HEMA), and that the silane compound, preferably gamma-methacryloxypropyltrimethoxysilane, is cured on the fiber surface. A method of making a fiber reinforced composite, wherein the composite consists of a cured polymer mass and a prepreg, comprising: - adding a plasticizer to said, optionally preformed, prepreg, - shaping the plasticized prepreg into the desired form, 10. coating the prepreg with unhardened polymer and - administering a polymerized combination of the polymer in the prepreg and the uncured polymer in the composite, characterized in that the prepreg according to any one of claims 1 to 10 is used. Method according to claim 11, characterized in that the composite obtained in the second step is processed into one or more pieces of the desired shape. 13. A process according to claim 11 or 12, characterized in that the plasticizer is a monomer of the polymer used in the prepreg. Method according to Claim 11, 12 or 13, characterized in that the unhardened polymer of the composite is the same as the polymer used in the prepreg. 15. A fiber-reinforced composite consisting of a cure. polymer mass and prepreg, wherein said prepreg is plasticized by wetting it with a monomer, formed into the desired shape and covered with a composite uncured polymer, and the polymer in the prepreg and the uncured polymer in the composite are simultaneously polymerized, characterized in that said prepreg 10 of the prepreg. 102946 22 Use of a composite according to claim 15, characterized in that it is used for medical or dental applications such as prosthetic, orthodontic or orthopedic products; removable prosthesis body parts, prosthetic clips or precision fasteners; permanent or temporary fixed prostheses, including dental and implant-based prostheses; dental or medical implants; tooth root canal fillings; 10 on rootstocks, columns, fillings or crowns; large shields or the like. 102946 23