Multilayer temporary crown and bridge material and forming method thereof

Abstract

The invention discloses a multilayer temporary crown and bridge material and a forming method thereof.The forming method comprises the steps that shaping is conducted, specifically, mixed powder of polymethyl methacrylate and pigment is shaped, and a single-color solid sample block is obtained; and hot pressing: stacking more than two single-color sample blocks according to a preset sequence and carrying out hot pressing to obtain the multi-layer temporary crown and bridge material. According to the forming method of the multi-layer temporary crown and bridge material, the controllability of the shape of each layer in the multi-layer temporary crown and bridge material can be improved, the production efficiency is improved, meanwhile, the multi-layer temporary crown and bridge material higher in quality and more stable in performance is obtained, and the requirement of dental clinical application is met.

Description

Technical Field

[0001] The present invention relates to the technical field of dental material preparation, in particular to a multi-layer temporary crown and bridge material and a molding method thereof. Background Art

[0002] In the dental field, the production of temporary crown and bridge materials is of great significance for the restoration of oral function and the maintenance of aesthetics during treatment. In particular, multi-layered and multi-colored PMMA blocks have emerged to meet the needs of aesthetics. Currently, there are two main methods for the production of PMMA temporary crown and bridge resin blocks in China:

[0003] The first method involves direct powder application, where each layer is applied according to the desired color, resulting in a sample with a natural color transition. This direct powder application requires the use of specially designed powder application equipment that precisely controls the thickness and uniformity of each layer. Each layer is applied according to a pre-designed color transition scheme. For example, when simulating a color gradient from crown to root, a lighter white or off-white filler powder is applied first near the crown. As the number of layers increases, a slightly darker yellowish filler powder is applied, ultimately leading to a light pink filler powder closer to the gum color at the root. During the powder application process, each layer must be tightly bonded to avoid loose powder or separation. This requires appropriate compaction after powder application, with a moderate compaction force that neither disrupts the established color hierarchy nor ensures sufficient contact area and bonding strength between the powders. Furthermore, to achieve a more natural and smooth color transition, repeated experimentation and optimization are required regarding the order of powder application, the thickness of each layer, and the mixing ratio of the different color powders. This direct powdering and carefully controlled color transition method allows for the production of PMMA temporary crown and bridge resin blocks with a distinct color transition. This method can better meet patients' aesthetic requirements for the appearance of dental restorations, ensuring a more harmonious and consistent color and shape with the surrounding natural teeth. However, due to the high flowability of the powder during production, the controllability of each layer's shape is limited.

[0004] The second method involves mixing PMMA and MMA into a dough-like mixture, then slicing and further producing PMMA. This method leverages the interaction between PMMA as a base polymer and MMA monomers. The two are first thoroughly mixed according to a specific ratio and process requirements to form a dough-like state. In this mixed system, PMMA helps regulate the overall system viscosity and improve processing performance, while MMA monomers provide the raw material base for subsequent polymerization reactions. Once mixed into a dough-like state, the mixture is sliced ​​into suitable shapes and sizes to facilitate subsequent heating, pressurization, and other processing steps. This promotes further polymerization of the MMA monomer within the PMMA matrix, thereby optimizing product performance and achieving final product shape. However, this method does not produce resins with color gradient effects.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The object of the present invention is to provide a multi-layer temporary crown and bridge material and a molding method thereof, so as to obtain a multi-layer temporary crown and bridge material with a gradual change effect and capable of improving the controllability of the shape of each layer.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a method for forming a multi-layer temporary crown and bridge material, comprising:

[0009] shaping, shaping the mixed powder of polymethyl methacrylate and pigment to obtain a single-color solid sample;

[0010] Hot pressing: stack two or more single-color samples in a preset order and perform hot pressing to obtain multi-layer temporary crown and bridge materials.

[0011] In an optional embodiment, the setting temperature is 130° C.-220° C., and the time is 0.5 h-6 h.

[0012] In an optional embodiment, the setting temperature is 140° C.-200° C., and the time is 0.5 h-3 h.

[0013] In an optional embodiment, the molecular weight of the polymethyl methacrylate is between 300,000 and 1.2 million.

[0014] In an optional embodiment, the mass fraction of the pigment in the mixed powder is 0.005 wt%-10 wt%.

[0015] In an optional embodiment, the mixed powder is obtained by dry mixing polymethyl methacrylate and pigment.

[0016] In an optional embodiment, the mixing equipment is selected from at least one of a ball mill, a horizontal mold and a three-dimensional mixer, and the ball mill rotation speed is 200 r / min-800 r / min, and the time is 0.5h-1.5h.

[0017] In an optional embodiment, the hot pressing temperature is 120° C.-190° C., the hot pressing pressure is 5 MPa-10 MPa, and the hot pressing time is 0.5 h-3 h.

[0018] In a second aspect, the present invention provides a multi-layer temporary crown and bridge material prepared by the method described in any one of the aforementioned embodiments.

[0019] In an optional embodiment, the interface between adjacent layers of the multi-layer temporary crown and bridge material is a plane.

[0020] The present invention has the following beneficial effects:

[0021] The molding method of the multi-layer temporary crown and bridge material in this application can improve the controllability of the shape of each layer in the multi-layer temporary crown and bridge material, improve production efficiency, and obtain a multi-layer temporary crown and bridge material with higher quality and more stable performance, meeting the needs of dental clinical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 is a cross-sectional view of the multi-layer temporary crown and bridge material sample prepared in Example 1;

[0024] Figure 2 1. A top view of the multi-layer temporary crown and bridge material sample prepared in Example 1 (the upper layer is a transparent layer);

[0025] Figure 3 is a cross-sectional view of the multi-layer temporary crown and bridge material sample prepared in Comparative Example 1;

[0026] Figure 4 2 is a cross-sectional view of the multi-layer temporary crown and bridge material sample prepared in Comparative Example 1 (the upper layer is a transparent layer);

[0027] Figure 5 This is a diagram of the state of the powder after melting in Comparative Example 4;

[0028] Figure 6 A cross-sectional view of a dental crown and bridge material. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0030] Since polymethyl methacrylate powder has a low density and good fluidity, it is difficult to ensure that the interface between adjacent layers of the multi-layer temporary crown and bridge material is in a preset shape if the powder is directly spread, and the controllability of the multi-layer temporary crown and bridge material is low.

[0031] In order to solve the above problems, an embodiment of the present invention provides a method for forming a multi-layer temporary crown and bridge material, comprising:

[0032] shaping, shaping the mixed powder of polymethyl methacrylate and pigment to obtain a single-color solid sample;

[0033] Hot pressing: stack two or more single-color samples in a preset order and perform hot pressing to obtain multi-layer temporary crown and bridge materials.

[0034] The molding method of the multi-layer temporary crown and bridge material of the present application can improve the controllability of the shape of each layer in the multi-layer temporary crown and bridge material. Compared with the method of hot pressing after layered powdering, the present invention pre-dries and shapes each layer of powder before hot pressing, thereby improving the controllability of the shape of each layer in the multi-layer temporary crown and bridge material, improving product quality and stability, and being beneficial to making the dental temporary crown and bridge resin block more regular in structure, which helps to improve its adaptability and aesthetics in the oral cavity.

[0035] In this application, the shaping step ensures that each layer of powder has a certain shape and stability before stacking and hot pressing, reducing the adjustment time during the hot pressing process. At the same time, the parameters of each step are clear, which is convenient for operation and control, and improves the controllability and smoothness of the entire production process, thereby shortening the production cycle and being able to produce more qualified products in the same time, meeting the needs of dental clinical applications for temporary crown and bridge materials.

[0036] Furthermore, since the controllability of the shape of each layer in the multi-layer temporary crown and bridge material is improved, the product quality is more stable, and the output of waste products caused by the low controllability of the shape of each layer in the multi-layer temporary crown and bridge material or the unstable structure is reduced, thereby reducing the waste of raw materials and reducing production costs.

[0037] In an optional embodiment, the setting temperature is 130° C.-220° C., and the time is 0.5 h-6 h.

[0038] If the shaping temperature is too high, the mixed powder may melt and produce bubbles, which is not conducive to the aesthetics of the multi-layer temporary crown and bridge material and will also reduce the strength; if the shaping temperature is too low, the mixed powder will be difficult to form a block, and the controllability of the powdered mixed powder will be reduced during the hot pressing process, which will still lead to a reduction in the controllability of the shape of each layer in the multi-layer temporary crown and bridge material.

[0039] In some embodiments, the shaping step involves placing the color-adjusted mixed powder into a mold, spreading the powder, and then placing the mold in a heated environment for shaping. The heating method includes, but is not limited to, conduction heating, convection heating, radiation heating, etc., as long as the mixed powder can be heated. The mold shape can be selected as needed. A mold can be directly selected to match the shape of the multi-layer temporary crown or bridge material, or the mold can be formed and then cut or otherwise processed to match the shape of the multi-layer temporary crown or bridge material.

[0040] In an optional embodiment, the setting temperature is 140° C.-200° C., and the time is 0.5 h-3 h.

[0041] In an optional embodiment, the molecular weight of the polymethyl methacrylate is between 300,000 and 1.2 million.

[0042] In an optional embodiment, the mass fraction of the pigment in the mixed powder is 0.005 wt%-10 wt%.

[0043] Pigments include, but are not limited to, titanium dioxide, iron oxide series (iron oxide red, iron oxide black, iron oxide yellow, iron oxide brown), Ultramarine Violet V-5, Ultramarine Blue, metal oxide mixed phase pigments (MMO pigments), titanium chrome yellow, titanium chrome brown, titanium manganese brown, titanium nickel yellow, chrome copper black, cobalt blue, cobalt green, chrome cobalt green, titanium iron brown, bismuth pigments (such as bismuth vanadate), molybdenum pigments (such as molybdenum chrome red), tin pigments (such as zinc stannate), zirconium pigments (such as zirconium iron red), lithopone, calcium carbonate, and other inorganic pigments. Preferably, the pigment is an inorganic pigment that is harmless to the human body, such as iron oxide.

[0044] In an optional embodiment, the mixed powder is obtained by dry mixing polymethyl methacrylate and pigment. Preferably, the mixing method is dry mixing to reduce the use and residue of solvents.

[0045] In an optional embodiment, the mixing device is selected from at least one of a ball mill, a horizontal mold, and a three-dimensional mixer, the ball mill speed is 200 rpm to 800 rpm, and the time is 0.5 h to 1.5 h. The ball mill jar used for the ball mill can be made of zirconium oxide, polyurethane, nylon, and polyethylene, and the ball mill can use agate, polyurethane, stainless steel, or zirconium oxide grinding balls.

[0046] In an optional embodiment, the hot pressing temperature is 120° C.-190° C., the hot pressing pressure is 5 MPa-10 MPa, and the hot pressing time is 0.5 h-3 h.

[0047] An embodiment of the present invention further provides a multi-layer temporary crown and bridge material, which is prepared by the method described in any one of the aforementioned embodiments.

[0048] In an optional embodiment, the interface between adjacent layers of the multi-layer temporary crown and bridge material is a plane.

[0049] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0050] Example 1

[0051] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0052] Step (1): Add 1% by mass of inorganic pigment (including a mixture of multiple inorganic colorants) and 99% by mass of PMMA powder into a zirconia ball mill (using zirconia grinding balls), and dry-mix them at a speed of 300 r / min for 0.5 h to ensure uniform mixing and dispersion.

[0053] Step (2): Use a mold with the same size as the final hot pressing mold, pour the color-adjusted powder into the mold, fill it with powder and flatten it, then place it in a 180°C oven for 60 minutes to obtain a sheet-like solid sample.

[0054] Step (3): Place two solid samples of different colors into the hot pressing mold in order, and hot press them at 170℃ and 8MPa pressure for 1.5h. The final multi-layer temporary crown and bridge material is as follows: Figure 1-2 As shown, the interlayer interface has good flatness, smooth appearance, uniform color, and various performance indicators meet the requirements of dental temporary crown and bridge materials.

[0055] Example 2

[0056] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0057] Step (1): 5% by mass of inorganic pigment and 95% by mass of PMMA powder were placed in a polyurethane ball mill (using polyurethane grinding balls), and dry-mixed by ball milling at 350 r / min for 0.5 h to achieve sufficient mixing and dispersion.

[0058] Step (2): Use a preheated mold that is slightly smaller than the size of the hot pressing mold, fill it with powder and level the powder with the adjusted color, then place it in a 160°C oven for 80 minutes to obtain a sheet-like solid sample.

[0059] Step (3): Place two solid samples of different colors into a hot pressing mold and heat press them at 160°C and 9 MPa for 2 hours. The resulting multi-layer temporary crown and bridge material has tight interlayer bonding, natural color transition, and a smooth production process with high production efficiency.

[0060] Example 3

[0061] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0062] Step (1): put 1% by mass of inorganic pigment and 99% by mass of PMMA powder into a nylon ball mill (with stainless steel grinding balls), and dry-mix at 250 r / min for 1 hour.

[0063] Step (2): Using a preheated mold with a size similar to that of the hot pressing mold, fill the mold with powder and flatten it, then place it in an oven at 200°C for 100 minutes to obtain a sheet-like solid solid sample.

[0064] Step (3): Two solid samples of different colors are placed in a hot pressing mold in sequence and hot pressed at 180°C and 10 MPa for 1 hour. The resulting multi-layer temporary crown and bridge material has high parallelism between layers, bright and evenly distributed colors, and a low scrap rate during the production process, effectively saving raw materials.

[0065] Example 4

[0066] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0067] Step (1): 0.5% by mass of inorganic pigment and 99.5% by mass of PMMA powder were added into a zirconia ball mill (using zirconia grinding balls), and dry-mixed by ball milling at a speed of 400 r / min for 0.5 h to ensure uniform mixing and dispersion.

[0068] Step (2): Use a mold with the same size as the final hot pressing mold, pour the color-adjusted powder into the mold, fill it with powder and flatten it, then put it into a 140°C oven for 120 minutes to obtain a single-color solid sample.

[0069] Step (3): Two solid samples of different colors are placed in a hot pressing mold in sequence and hot pressed at 190°C and 7 MPa for 1 hour. The resulting multilayer temporary crown and bridge material has good interlayer interface flatness, a smooth appearance, and uniform color. All performance indicators meet the requirements of dental temporary crown and bridge materials.

[0070] Example 5

[0071] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0072] Step (1): 0.5% by mass of inorganic pigment and 99.5% by mass of PMMA powder were placed in a polyurethane ball mill (using polyurethane grinding balls), and dry-mixed by ball milling at 320 r / min for 0.5 h to achieve sufficient mixing and dispersion.

[0073] Step (2): Use a preheated mold that is slightly smaller than the size of the hot pressing mold, fill it with powder and level the powder with the adjusted color, then place it in a 150°C oven for 80 minutes to obtain a sheet-like solid sample.

[0074] Step (3): Two solid samples of different colors are placed in a hot pressing mold in sequence and hot pressed at 175°C and 6 MPa for 1.8 hours. The resulting multi-layer temporary crown and bridge material has tight interlayer bonding, natural color transition, and a smooth production process with high production efficiency.

[0075] Example 6

[0076] This embodiment provides a method for forming a multi-layer temporary crown and bridge material, which specifically includes the following steps:

[0077] Step (1): 0.5% by mass of inorganic pigment and 99.5% by mass of PMMA powder were placed in a nylon ball mill (with stainless steel grinding balls), and dry-mixed at 280 r / min for 0.5 h.

[0078] Step (2): Use a preheated mold with a size similar to that of the hot pressing mold, fill the powder and flatten it, then place it in an oven at 130°C for 160 minutes to obtain a sheet-like solid solid sample.

[0079] Step (3): Two solid samples of different colors are placed in a hot pressing mold in sequence and hot pressed at 165°C and 10 MPa for 2 hours. The resulting multilayer temporary crown and bridge material has good interlayer interface flatness, a smooth appearance, and uniform color. All performance indicators meet the requirements of dental temporary crown and bridge materials.

[0080] Comparative Example 1

[0081] This comparative example provides a molding method for a multi-layer temporary crown and bridge material. The main difference from Example 1 is that no shaping is performed, and two layers of powder are layered and then directly hot-pressed into a shape such as Figure 3-4 shown.

[0082] Comparative Example 2

[0083] This comparative example provides a molding method for a multi-layer temporary crown and bridge material. The main difference from Example 1 is that no shaping is performed and no layered powder spreading is performed. Instead, a layer of evenly mixed powder is directly spread and then hot-pressed to obtain a single-layer temporary crown and bridge material.

[0084] Comparative Example 3

[0085] This comparative example provides a molding method for a multi-layer temporary crown and bridge material. The main difference from Example 1 is that the molding temperature is 70°C, the time is 6 hours, and then two single-color solid sample blocks are stacked and hot-pressed.

[0086] Comparative Example 4

[0087] This comparative example provides a molding method for a multi-layer temporary crown and bridge material. The main difference from Example 1 is that the molding temperature is 230° C., the time is 6 hours, and then two single-color solid sample blocks are stacked and hot-pressed.

[0088] This test example tests the bending strength and flatness of the layered interface of the multi-layer temporary crown and bridge materials prepared in various embodiments and comparative examples. The test method is as follows:

[0089] Three-point bending strength: A universal testing machine (AGS, Shimadzu, Japan) was used to test the bending strength. The three-point bending test was performed at a loading rate of 1 mm / min with a specimen size of 18 × 4 × 2 mm. Strength in both the horizontal and vertical directions was tested.

[0090] Delamination: Delineate the delamination from the cross-sectional state of the multi-layer temporary crown and bridge material.

[0091] The test results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] In this application, the cross section of the multilayer temporary crown and bridge material obtained in Example 1 is as follows: Figure 1 As shown, the two layers of solid-state samples are both in the form of flakes, and the interface is flat and has no undulations. The stratification of Examples 2-6 is similar to that of Figure 1 Similarly, it shows that the shape of each layer of the multi-layer temporary crown and bridge material obtained in this application is well controllable; the multi-layer temporary crown and bridge material obtained in Comparative Example 1 is as follows Figure 3 、 4 As shown, the interface between the two layers of monochrome solid sample blocks is undulating, and the monochrome solid sample blocks have undergone uncontrollable deformation. The three-point bending strength of the multi-layer temporary crown and bridge materials obtained in Example 1 and Comparative Example 1 is not much different. Example 1 even has a slight advantage, indicating that the present application also has advantages in improving the three-point bending strength of the multi-layer temporary crown and bridge materials. In Comparative Example 3, the shaping temperature is too low, and the powder does not form a block (the powder is directly poured into the mold in layers for hot pressing), resulting in uncontrollable deformation of the monochrome solid sample blocks. In Comparative Example 4, the shaping temperature is too high, and the powder melts to produce, as shown in FIG. Figure 5Furthermore, the bending strength of the multi-layer temporary crown and bridge materials obtained in each embodiment in both directions is above 100 MPa, which meets the requirements for the production of oral restorations.

[0096] It should be noted that the monochrome solid sample blocks prepared in the various embodiments and comparative examples of the present application are in the form of sheets, which facilitates viewing the controllability of the layered shape in the multi-layer temporary crown and bridge material. In other application cases, the shape of the monochrome solid sample blocks can be selected as needed, for example, the layered interface can be wavy, serrated or other preset irregular shapes; furthermore, the colors and amounts of the pigments used in the various embodiments and comparative examples of the present application are relatively large, so that the interface shape and flatness can be seen. In other application cases, the amount and composition of the pigments can be adjusted as needed. For example, in dental crown and bridge materials, the amount and composition of the pigments can be adjusted on the basis of Example 1 to obtain a cross-section as shown in FIG. Figure 6 Materials shown.

[0097] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for forming a multi-layer temporary crown and bridge material, characterized in that: include: shaping, shaping the mixed powder of polymethyl methacrylate and pigment to obtain a single-color solid sample; Hot pressing: stack two or more single-color samples in a preset order and perform hot pressing to obtain multi-layer temporary crown and bridge materials.

2. The molding method of multi-layer temporary crown and bridge material according to claim 1, characterized in that: The setting temperature is 130° C.-220° C., and the time is 0.5 h-6 h.

3. The molding method of the multi-layer temporary crown and bridge material according to claim 2, characterized in that: The setting temperature is 140° C.-200° C., and the time is 0.5 h-3 h.

4. The molding method of multi-layer temporary crown and bridge material according to claim 1, characterized in that: The molecular weight of the polymethyl methacrylate is between 300,000 and 1.2 million.

5. The molding method of multi-layer temporary crown and bridge material according to claim 1, characterized in that: The mass fraction of the pigment in the mixed powder is 0.005 wt%-10 wt%.

6. The method for forming a multi-layer temporary crown and bridge material according to claim 1, characterized in that: The mixed powder is obtained by dry mixing polymethyl methacrylate and pigment.

7. The method for forming a multi-layer temporary crown and bridge material according to claim 6, characterized in that: The mixing equipment is selected from at least one of a ball mill, a horizontal mold and a three-dimensional mixer. The ball mill has a rotation speed of 200 r / min-800 r / min and a mixing time of 0.5 h-1.5 h.

8. The method for forming a multi-layer temporary crown and bridge material according to claim 1, characterized in that: The hot pressing temperature is 120℃-190℃, the hot pressing pressure is 5MPa-10MPa, and the hot pressing time is 0.5h-3h.

9. A multi-layer temporary crown and bridge material, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. The multi-layer temporary crown and bridge material according to claim 9, characterized in that: The interface between adjacent layers of the multi-layer temporary crown and bridge material is a plane.

Images