Preparation method and device of PMMA dental repair crown and bridge

Abstract

The invention relates to a preparation method and device for a PMMA dental repair crown bridge, and belongs to the technical field of biomedical engineering industries. Methyl methacrylate monomers, a polymerization initiator, nano pigment powder and fumed silica filler are evenly mixed through mechanical stirring, a pre-mixed slurry is subjected to a polymerization reaction through a heating device, and the PMMA dental repair crown bridge is obtained. Detecting the system temperature when the premixed slurry is heated in the heating device in real time, and stopping heating when the system temperature exceeds a set value and rapidly rises; transferring the heated mold filled with the premixed slurry to a low-temperature environment to inhibit the polymerization reaction rate, and carrying out primary system uniform dispersion after the premixed slurry is subjected to primary polymerization reaction through ultrasonic waves; then the premixed slurry subjected to ultrasonic treatment is subjected to polymerization reaction through the heating device again, the system temperature of the premixed slurry heated in the heating device is detected in real time, bubble residues are reduced, stress cracks are avoided, the material density is improved, and filler and pigment are promoted to be evenly distributed and dispersed.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing PMMA dental restorative crowns and bridges, belonging to the field of biomedical engineering technology. Background Technology

[0002] In the prior art, polymethyl methacrylate (PMMA) materials occupy an important position in the field of dental restoration due to their good biocompatibility, realistic aesthetic effects and simple processing technology. For example, the patent document "A PMMA Resin Material for Dental Use and Its Application" with classification number A61K6 and application number 202110566719.1 specifically discloses the preparation process of PMMA materials.

[0003] With the continuous advancement of materials science and dental restoration concepts, the expectations of existing dental restoration technologies for restorations have been raised from basic morphological restoration and short-term use to a comprehensive demand for long-term durability, functional adaptability, and biomimetic properties. This has exposed the performance limitations of traditional powder-liquid thermoforming processes, making them a bottleneck for the materials to meet higher clinical needs.

[0004] Traditional powder-liquid hot pressing molding involves mixing PMMA prepolymer powder with methyl methacrylate monomer liquid in a specific ratio, filling the mold during the dough stage, and then heating and pressurizing it to polymerize and solidify. This traditional process has several limitations: First, the mixing and heating process cannot completely prevent air entrapment and incomplete monomer conversion, resulting in microscopic voids and residual monomers within the final profile. These voids become stress concentration points, significantly weakening the material's fatigue strength and fracture toughness. The residual monomers act as plasticizers, reducing the material's stiffness and hardness and potentially causing biocompatibility issues. Second, the polymer network formed under this process has limited molecular weight and cross-linking degree due to the characteristics of the prepolymer powder and the relatively mild polymerization conditions, resulting in generally low mechanical strength, elastic modulus, and creep resistance. More importantly, the material properties produced by this process are relatively singular and fixed. However, teeth in different locations within the oral cavity have different functions. For example, front teeth need to have a certain level of impact resistance and tear resistance, while also having extremely high aesthetic requirements. Back teeth need to withstand enormous and repetitive chewing pressure, placing stringent demands on the material's hardness, wear resistance, compressive strength, and deformation resistance. The one-size-fits-all performance model of traditional homogeneous PMMA materials is clearly unable to accurately adapt to these gradient biomechanical needs.

[0005] To break through the traditional powder-liquid hot pressing molding process, the research and development direction shifted to a more advanced preparation route—bulk polymerization. Bulk polymerization is a method that directly polymerizes monomers or oligomers with little or no solvent or dispersion medium through heat, light, or initiators to form solid polymers. Specifically, it uses a high-purity methyl methacrylate monomer system, completing the polymerization reaction under precise temperature, pressure, and light conditions. Bulk polymerization fundamentally reduces defects introduced by solvent evaporation or uneven mixing. Through pressure polymerization and other methods, it obtains polymer preforms with extremely dense structures and low porosity, while simultaneously achieving extremely high monomer conversion rates and reducing residual monomer content.

[0006] In the actual PMMA bulk polymerization manufacturing process, there are still some defects that need to be overcome. For example, the bulk polymerization process is prone to explosive polymerization, the curing rate is difficult to control, bubbles are difficult to eliminate, and the color distribution is uneven. The root cause is that the polymerization reaction of MMA monomers is an exothermic process. The accumulation of reaction heat will cause the system temperature to rise sharply, the system reaction will have a self-accelerating effect, and a vicious cycle will be formed, eventually leading to explosive polymerization. Defects such as bubbles, cracks, and uneven distribution will also occur. Therefore, how to stably control the PMMA bulk polymerization reaction process is the core difficulty in improving the PMMA bulk polymerization process. Summary of the Invention

[0007] In view of the problems of easy explosive polymerization, difficult curing rate control, difficulty in eliminating air bubbles, and uneven color distribution in the preparation process of PMMA materials mentioned above, the purpose of this invention is to provide a method and device for preparing PMMA dental restorative crowns and bridges, which can eliminate air bubbles and cracks and improve the stability of the material's mechanical properties.

[0008] According to an embodiment of the present invention, the first embodiment is provided as follows: a method for preparing a PMMA dental restorative crown and bridge, comprising the following steps: S1: Methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler are placed in a container and mechanically stirred to form a uniformly mixed premixed slurry; S2: After the premixed slurry is poured into the mold, it is placed in a heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry; S3: Obtain the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches the preset threshold, terminate the heating of the heating device. S4: Transfer the mold to a low-temperature environment and apply ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to be uniformly dispersed after undergoing one polymerization reaction. S5: Repeat steps S2-S4, each time steps S2-S4 are executed, the polymerization reaction of the premixed slurry is advanced once; S6: After the premixed slurry is fully cured, a PMMA composite is obtained.

[0009] Furthermore, the polymerization initiator is benzoyl peroxide, and the amount of benzoyl peroxide added is 0.3%-0.6% of the mass of methyl methacrylate monomer.

[0010] Furthermore, the nano-pigment powder includes nano-iron red powder, nano-iron yellow powder, nano-carbon powder, and nano-titanium dioxide powder.

[0011] Furthermore, the amount of fumed silica filler added is 1%-40% of the mass of methyl methacrylate monomer.

[0012] Furthermore, the heating device has a heating temperature range of 70-85℃ and a heating time of 15-25 minutes.

[0013] Furthermore, the ultrasonic treatment has a power of 100-500W, a frequency of 20-40kHz, and a processing time of 15-25 minutes.

[0014] Furthermore, the criterion for determining whether the premixed slurry has completely cured is that the system temperature of the premixed slurry stops rising.

[0015] Further, the process of obtaining the system temperature of the premixed slurry, and terminating the heating of the heating device when the system temperature exceeds the heating temperature of the heating device and the rate of temperature rise reaches a threshold, includes: The non-contact temperature measuring device performs real-time temperature detection on the interlocking surface area, adjacent surface area, and edge area of ​​the mold. When the temperature of any area in the interlocking surface area, adjacent surface area, or edge area exceeds the heating temperature and the temperature rise rate of the area reaches a preset threshold, the heating is terminated and the process proceeds to step S4.

[0016] Furthermore, the step of transferring the mold to a low-temperature environment includes: The mold containing the premixed slurry, after the heating is terminated, is fixed in the annealing furnace for annealing. The interlocking surface area is aligned with the heat preservation module inside the furnace, and the adjacent and edge areas are cooled by the cooling module. This achieves a differential annealing process where the cooling rate of the interlocking surface area is less than that of the adjacent and edge areas. This differential annealing process reduces internal stress defects caused by surface shrinkage and internal stretching and ensures the stability of the PMMA composite.

[0017] Furthermore, the steps of transferring the mold to a low-temperature environment and applying ultrasonic treatment include: Within the first time range of ultrasonic treatment, the highest power ultrasonic treatment is maintained to efficiently disperse the agglomerates of fumed silica filler, eliminate bubble nuclei generated by polymerization reaction, and promote the uniform dispersion of nano-pigment powder through ultrasonic cavitation effect and mechanical vibration. Within the second time range of ultrasonic treatment, the system temperature drop rate is monitored in real time. When the temperature drops below the heating-induced temperature, the system switches to a second low-power ultrasonic treatment and maintains a linear reduction rate of the second low power according to the temperature drop rate to ensure a stable temperature decrease and gentle heat dissipation.

[0018] Furthermore, the premixed slurry is poured into a continuous steel strip mold, the continuous steel strip moving continuously at an adjustable speed of 0.5-2 m / min; The speed of the continuous steel belt is reduced when the temperature of the premixed slurry exceeds the set heating temperature in the heating section and shows a rapid upward trend, so as to prolong the residence time of the premixed slurry in the heating section and the ultrasonic section. The system temperature is checked once every unit of time until the slurry is completely cured.

[0019] According to an embodiment of the present invention, a second embodiment is provided: a PMMA dental restorative crown and bridge preparation apparatus for applying a PMMA dental restorative crown and bridge preparation method, the preparation apparatus comprising: The premixing module places methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler in a container and mechanically stirs them to form a uniformly mixed premixed slurry. The heating module is used to pour the premixed slurry into the mold and then place it in the heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry. The temperature rise rate determination module obtains the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches a preset threshold, the heating of the heating device is terminated. The uniform dispersion module transfers the mold to a low-temperature environment and applies ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to undergo a uniform dispersion once after a polymerization reaction. The process of heating the module to the uniform dispersion module is repeated. Each time the heating module to the uniform dispersion module cycle is performed, the polymerization reaction of the premixed slurry is advanced once. After the premixed slurry is completely cured in the curing module, a PMMA composite is obtained.

[0020] Compared with existing technologies, the PMMA dental restoration crown and bridge preparation method and apparatus provided in this application have the following advantages: Methyl methacrylate monomer, polymerization initiator, nano-pigment powder, and fumed silica filler are uniformly mixed by mechanical stirring to ensure uniform dispersion of each component and form a stable premixed system. A heating device is used to induce polymerization of the premixed slurry, and the system temperature is monitored in real time. Heating is terminated when the system temperature exceeds a set value and rises rapidly. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to inhibit the polymerization rate. Ultrasonic treatment is then used to uniformly disperse the premixed slurry after one polymerization reaction. After undergoing another uniform dispersion through ultrasonic treatment, the ultrasonically treated premixed slurry is again subjected to polymerization by the heating device, with real-time monitoring of the system temperature. Heating is terminated when the system temperature exceeds a set value and rises rapidly. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization reaction rate. Then, ultrasound is used to make the premixed slurry uniformly dispersed after undergoing one polymerization reaction, reducing residual bubbles, dissipating reaction heat, avoiding stress cracks, increasing material density, promoting uniform dispersion of fillers and pigments, and ensuring consistent performance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] in: Figure 1 This is a flowchart illustrating a method for preparing a PMMA dental restorative crown and bridge in one embodiment; Figure 2 This is a flowchart of a PMMA dental restoration crown and bridge preparation apparatus in one embodiment. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Example 1 In the bulk polymerization manufacturing process of PMMA, there are problems such as easy burst polymerization, difficulty in controlling the curing rate, difficulty in eliminating bubbles, and uneven color distribution. The root cause is that the polymerization reaction of MMA monomers is an exothermic process. The accumulation of reaction heat will cause the system temperature to rise sharply, the system reaction will have a self-accelerating effect, and a vicious cycle will be formed, eventually leading to burst polymerization. Defects such as bubbles, cracks, and uneven distribution will also occur. Therefore, how to stably control the PMMA bulk polymerization reaction process is the core difficulty in improving the PMMA bulk polymerization process.

[0025] like Figure 1 As shown, in order to solve the above problems, this embodiment provides a method for preparing PMMA dental restorative crowns and bridges, including the following steps: S1: Methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler are placed in a container and mechanically stirred to form a uniformly mixed premixed slurry; In step S1, methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler are uniformly mixed by mechanical stirring to ensure uniform dispersion of each component and form a stable premixed system.

[0026] S2: After the premixed slurry is poured into the mold, it is placed in a heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry; In step S2, a heating device is used to cause the premixed slurry to polymerize.

[0027] S3: Obtain the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches the preset threshold, terminate the heating of the heating device. In step S3, the system temperature of the premixed slurry is monitored in real time during heating in the heating device. Heating is terminated when the system temperature exceeds the set value and rises rapidly. The system temperature refers to the real-time temperature of the premixed slurry as a whole during the preparation of PMMA dental restorative materials, reflecting the exothermic intensity and progress of the polymerization reaction.

[0028] S4: Transfer the mold to a low-temperature environment and apply ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to be uniformly dispersed after undergoing one polymerization reaction. In step S4, after heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization reaction rate. Then, ultrasound is used to make the premixed slurry uniformly dispersed after undergoing one polymerization reaction, reducing residual bubbles, dissipating reaction heat, avoiding stress cracks, increasing material density, promoting uniform dispersion of fillers and pigments, and ensuring consistent performance.

[0029] S5: Repeat steps S2-S4, each time steps S2-S4 are executed, the polymerization reaction of the premixed slurry is advanced once; In step S5, after undergoing one polymerization reaction through ultrasonic treatment, the system is uniformly dispersed once. The ultrasonically treated premixed slurry is then subjected to another polymerization reaction using a heating device. The system temperature of the premixed slurry is monitored in real time during heating. Heating is terminated when the system temperature exceeds a set value and rises rapidly. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization rate. Ultrasonic treatment is then used to uniformly disperse the premixed slurry once more after the first polymerization reaction, reducing residual bubbles, dissipating reaction heat, preventing stress cracks, increasing material density, promoting uniform dispersion of fillers and pigments, and ensuring consistent performance.

[0030] S6: After the premixed slurry is fully cured, a PMMA composite is obtained.

[0031] In step S6, by repeating steps S2-S4, each cycle advances a segment of the polymerization reaction. By advancing the polymerization reaction in a segmented and gentle manner, the accumulation of reaction heat is avoided. Multiple cycles ensure complete reaction, improve conversion rate, and further enhance uniformity. This reduces residual bubbles, dissipates reaction heat, prevents stress cracking, increases material density, promotes uniform dispersion of fillers and pigments, and ensures consistent performance.

[0032] It is worth noting that methyl methacrylate monomer, polymerization initiator, nano-pigment powder, and fumed silica filler are uniformly mixed by mechanical stirring to ensure uniform dispersion of each component and form a stable premixed system. A heating device is used to initiate the polymerization reaction of the premixed slurry. The system temperature of the premixed slurry during heating is monitored in real time. Heating is terminated when the system temperature exceeds the set value and rises rapidly. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization rate. Ultrasonic treatment is then used to uniformly disperse the premixed slurry after one polymerization reaction. After this second uniform dispersion through ultrasonic treatment, the ultrasonically treated premixed slurry is again subjected to a heating device to initiate the polymerization reaction. The system temperature of the premixed slurry during heating is monitored in real time. Heating is terminated when the system temperature exceeds the set value and rises rapidly. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization reaction rate. Then, ultrasound is used to make the premixed slurry uniformly dispersed after undergoing one polymerization reaction, reducing residual bubbles, dissipating reaction heat, avoiding stress cracks, increasing material density, promoting uniform dispersion of fillers and pigments, and ensuring consistent performance.

[0033] Specifically, the polymerization initiator is benzoyl peroxide, and the amount of benzoyl peroxide added is 0.3%-0.6% of the mass of methyl methacrylate monomer.

[0034] It should be noted that the reaction is stable and controllable, ensuring both efficient monomer conversion and avoiding thermal runaway.

[0035] Specifically, the nano-pigment powder includes nano-iron red powder, nano-iron yellow powder, nano-carbon powder, and nano-titanium dioxide powder.

[0036] It should be noted that nano-pigment powders include nano-iron red powder, nano-iron yellow powder, nano-carbon powder, and nano-titanium dioxide powder. They achieve color presentation through the selective absorption and reflection of visible light. Nano-pigments have a high specific surface area and quantum size effect, which allows them to mix with monomers more efficiently. They also avoid uneven light scattering caused by excessively large particles, unlike traditional micron-sized pigments which are prone to color spots. This enables precise color matching and a natural transition of semi-transparency.

[0037] Specifically, the amount of fumed silica filler added is 1%-40% of the mass of methyl methacrylate monomer.

[0038] It should be noted that fumed silica is a nanoscale amorphous powder with a high specific surface area. Its surface is rich in hydroxyl groups, which can form hydrogen bonds or chemical bonds with methyl methacrylate monomers, enhancing the interfacial bonding between the filler and the matrix. During the polymerization process, fumed silica acts as a rigid reinforcing phase.

[0039] Specifically, the heating temperature range of the heating device is 70-85℃, and the heating time is 15-25 minutes.

[0040] It should be noted that the polymerization initiator is benzoyl peroxide, which has a decomposition temperature range of 70-90℃. At 70-85℃, benzoyl peroxide can slowly decompose to generate free radicals, which can initiate the polymerization reaction of methyl methacrylate monomers. At the same time, it avoids the problem of excessive free radicals causing explosive polymerization due to excessively high temperature or insufficient initiation efficiency and low monomer conversion rate due to excessively low temperature.

[0041] Specifically, the ultrasonic treatment has a power of 100-500W, a frequency of 20-40kHz, and a treatment time of 15-25 minutes.

[0042] It should be noted that through ultrasonic treatment, the high-frequency vibration of ultrasound promotes molecular motion within the system, accelerates heat transfer, and breaks up localized heat accumulation areas. The cavitation effect of ultrasound strongly disperses bubble nuclei, and mechanical vibration promotes heat dissipation. Ultrasonic vibration breaks up agglomerates, ensuring uniform distribution of fumed silica and nano-pigments, thus guaranteeing consistent mechanical properties of the material.

[0043] Specifically, the criterion for determining whether the premixed slurry has completely cured is that the temperature of the premixed slurry system stops rising.

[0044] It should be noted that when the system temperature no longer rises, it indicates that the monomer has been completely converted into the polymer, and the reaction terminates.

[0045] Example 2 Based on Example 1, this example provides a further solution.

[0046] Specifically, the steps for obtaining the system temperature of the premixed slurry, and terminating the heating of the heating device when the system temperature exceeds the heating temperature of the heating device and the rate of temperature rise reaches a threshold, include: The non-contact temperature measuring device performs real-time temperature detection on the interlocking surface area, adjacent surface area, and edge area of ​​the mold. When the temperature of any area in the interlocking surface area, adjacent surface area, or edge area exceeds the heating temperature and the temperature rise rate of the area reaches a preset threshold, the heating is terminated and the process proceeds to step S4.

[0047] It should be noted that due to structural differences in thickness and shape, the occlusal, proximal, and edge areas of dental restoration crown and bridge molds exhibit uneven heat distribution during the polymerization reaction. The occlusal area, typically a thick-walled region, is prone to heat accumulation and exhibits a rapid rate of heat release during the reaction. The proximal and edge areas, while dissipating heat quickly, suffer from localized stress concentration, making them susceptible to cracking due to temperature fluctuations. By precisely detecting localized overheating through zoned temperature monitoring and timely intervention, a gentle reaction is achieved across the occlusal, proximal, and edge areas, preventing internal bubbles and cracks in the material.

[0048] Specifically, the steps for transferring the mold to a low-temperature environment include: The mold containing the premixed slurry, after the heating is terminated, is fixed in the annealing furnace for annealing. The interlocking surface area is aligned with the heat preservation module inside the furnace, and the adjacent and edge areas are cooled by the cooling module. This achieves a differential annealing process where the cooling rate of the interlocking surface area is less than that of the adjacent and edge areas. This differential annealing process reduces internal stress defects caused by surface shrinkage and internal stretching and ensures the stability of the PMMA composite.

[0049] It should be noted that the technical problems to be solved in this step are: A large interlocking surface thickness, such as 1-3 mm, results in high heat capacity. Cooling can prevent excessive temperature differences between the interior and surface, thus preventing internal stress cracks caused by surface shrinkage and internal stretching. Simultaneously, it meets the interfacial stress release requirements when the silica content is high, enhancing the bonding stability between the rigid filler and the matrix. A small thickness, such as 0.5-1 mm, in the adjacent and edge areas allows for rapid heat conduction and quick cooling for rapid shaping, avoiding warping deformation caused by prolonged high temperatures. Simultaneously, it meets the toughness maintenance requirements when the silica content is low, preventing overheating and softening of the matrix.

[0050] By precisely releasing localized stress, internal bubbles and cracks are eliminated, improving the yield rate; the fatigue resistance of the material is enhanced to meet the gradient biomechanical requirements of the anterior aesthetic zone and the posterior functional load-bearing zone. Defects are further reduced to ensure uniform material color and match the VITA shade guide. This process, through the control of structural and material adaptation, solves the residual stress problem of PMMA bulk polymer dental materials, resulting in a high production yield.

[0051] Further technical solutions are provided below.

[0052] Specifically, the steps of transferring the mold to a low-temperature environment and applying ultrasonic treatment include: Within the first time range of ultrasonic treatment, the highest power ultrasonic treatment is maintained to efficiently disperse the agglomerates of fumed silica filler, eliminate bubble nuclei generated by polymerization reaction, and promote the uniform dispersion of nano-pigment powder through ultrasonic cavitation effect and mechanical vibration. Within the second time range of ultrasonic treatment, the system temperature drop rate is monitored in real time. When the temperature drops below the heating-induced temperature, the system switches to a second low-power ultrasonic treatment and maintains a linear reduction rate of the second low power according to the temperature drop rate to ensure a stable temperature decrease and gentle heat dissipation.

[0053] It should be noted that the technical problem to be solved in this step is that the initial fixed power may not be able to fully disperse agglomerates or eliminate bubbles, and the high-intensity ultrasound in the later stage can easily cause microcracks in the polymerized parts, reducing the toughness of the material. In this embodiment, the ultrasound needs to achieve both dispersion and homogeneity and gentle heat dissipation in a low-temperature environment, but there are differences in different stages. In the first stage, high-power treatment is used when the polymerization reaction has just entered the low temperature stage. There are still incompletely dispersed fumed silica agglomerates, microbubble nuclei, and local heat accumulation areas in the system. At this time, high-power ultrasound is needed to strongly disperse agglomerates and bubble nuclei through cavitation effect, while using mechanical vibration to quickly transfer heat. The high power can be 300W. In the second stage, low-power treatment is used when the system temperature drops below the heating initiation temperature, such as 80°C. The reaction rate has been inhibited by the low temperature, and a steady cooling is required. At this time, the power needs to be reduced and linearly adjusted. The low power can be 100-200W to avoid high-power vibration causing new bubbles or material damage, while maintaining gentle heat dissipation to ensure that the temperature drops slowly. High-power ultrasound accelerates heat transfer, causing the system temperature to drop rapidly; low-power ultrasound maintains molecular motion, avoiding stress concentration caused by localized overcooling, and the low-temperature environment inhibits free radical activity, further reducing the reaction rate, ensuring stable temperature, and further improving material toughness; further reducing internal microcracks, the initial high power ensures uniform dispersion of nanofillers and pigments, and accurate color matching with the VITA shade guide, adapting to the needs of anterior tooth restoration; the later low power avoids structural damage and meets the impact toughness requirements of the anterior tooth area.

[0054] Further technical solutions are provided below.

[0055] Specifically, the premixed slurry is poured into a continuous steel strip mold, and the continuous steel strip moves continuously at an adjustable speed of 0.5-2 m / min; The speed of the continuous steel belt is reduced when the temperature of the premixed slurry exceeds the set heating temperature in the heating section and shows a rapid upward trend, so as to prolong the residence time of the premixed slurry in the heating section and the ultrasonic section. The system temperature is checked once every unit of time until the slurry is completely cured.

[0056] It should be noted that the technical problem to be solved in this step is that, under a continuous steel belt at a fixed speed, if the belt moves too fast, the premixed slurry will not stay in the heating section for long enough, resulting in incomplete reaction; if it moves too slowly, overheating will cause a self-accelerating effect, which can easily lead to explosive polymerization or insufficient curing, and there is a lack of dynamic feedback mechanism. By adjusting the speed to control the heat dissipation of the reaction, uniform curing is ensured, bubbles and cracks are eliminated, the stability of the material's mechanical properties is improved, production efficiency is increased, and formulations with different fumed silica contents are adapted to meet gradient performance requirements.

[0057] Example 3 See Figure 2 As shown, this embodiment provides a PMMA dental restorative crown and bridge preparation apparatus for applying a PMMA dental restorative crown and bridge preparation method according to Embodiment 1 or Embodiment 2 above. The PMMA dental restorative crown and bridge preparation apparatus of this embodiment includes: The premix module 100 places methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler in a container and forms a uniformly mixed premixed slurry by mechanical stirring. Heating module 200: After the premixed slurry is poured into the mold, it is placed in the heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry. The temperature rise rate determination module 300 obtains the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches a preset threshold, the heating of the heating device is terminated. The uniform dispersion module 400 transfers the mold to a low-temperature environment and applies ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to undergo a uniform dispersion once after a polymerization reaction. The step of heating the module to the uniform dispersion module is repeated. Each time the heating module to the uniform dispersion module cycle is performed, the polymerization reaction of the premixed slurry is advanced once. After the premixed slurry is fully cured in curing module 500, a PMMA composite is obtained.

[0058] It should be noted that the PMMA dental restoration crown and bridge preparation device provided in this embodiment uniformly mixes methyl methacrylate monomer, polymerization initiator, nano-pigment powder, and fumed silica filler by mechanical stirring to uniformly disperse the components and form a stable premixed system. A heating device is used to initiate the polymerization reaction of the premixed slurry. The system temperature of the premixed slurry during heating is monitored in real time. When the system temperature exceeds a set value and rises rapidly, heating is terminated. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to inhibit the polymerization rate. Ultrasonic treatment is then used to uniformly disperse the premixed slurry after one polymerization reaction. After undergoing another uniform dispersion through ultrasonic treatment, the ultrasonically treated premixed slurry is again subjected to a heating device to initiate the polymerization reaction. The system temperature of the premixed slurry during heating is monitored in real time. When the system temperature exceeds a set value and rises rapidly, heating is terminated. After heating is terminated, the mold containing the premixed slurry is transferred to a low-temperature environment to suppress the polymerization reaction rate. Then, ultrasound is used to make the premixed slurry uniformly dispersed after undergoing one polymerization reaction, reducing residual bubbles, dissipating reaction heat, avoiding stress cracks, increasing material density, promoting uniform dispersion of fillers and pigments, and ensuring consistent performance.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a PMMA dental restorative crown and bridge, characterized in that, Includes the following steps: S1: Methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler are placed in a container and mechanically stirred to form a uniformly mixed premixed slurry; S2: After the premixed slurry is poured into the mold, it is placed in a heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry; S3: Obtain the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches the preset threshold, terminate the heating of the heating device. S4: Transfer the mold to a low-temperature environment and apply ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to be uniformly dispersed after undergoing one polymerization reaction. S5: Repeat steps S2-S4, each time steps S2-S4 are executed, the polymerization reaction of the premixed slurry is advanced once; S6: After the premixed slurry is fully cured, a PMMA composite is obtained.

2. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The polymerization initiator is benzoyl peroxide, and the amount of benzoyl peroxide added is 0.3%-0.6% of the mass of methyl methacrylate monomer.

3. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The nano-pigment powders include nano-iron red powder, nano-iron yellow powder, nano-carbon powder, and nano-titanium dioxide powder.

4. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The amount of fumed silica filler added is 1%-40% of the mass of methyl methacrylate monomer.

5. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The heating device has a heating temperature range of 70-85℃ and a heating time of 15-25 minutes.

6. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The ultrasonic treatment has a power of 100-500W, a frequency of 20-40kHz, and a processing time of 15-25 minutes.

7. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The criterion for determining whether a premixed slurry has fully cured is that the temperature of the premixed slurry system stops rising.

8. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The steps for obtaining the system temperature of the premixed slurry and terminating the heating of the heating device when the system temperature exceeds the heating temperature of the heating device and the rate of temperature rise reaches a threshold include: The non-contact temperature measuring device performs real-time temperature detection on the interlocking surface area, adjacent surface area, and edge area of ​​the mold. When the temperature of any area in the interlocking surface area, adjacent surface area, or edge area exceeds the heating temperature and the temperature rise rate of the area reaches a preset threshold, the heating is terminated and the process proceeds to step S4.

9. The method for preparing PMMA dental restorative crowns and bridges according to claim 8, characterized in that, The steps for transferring the mold to a low-temperature environment include: The mold containing the premixed slurry, after the heating is terminated, is fixed in the annealing furnace for annealing. The interlocking surface area is aligned with the heat preservation module inside the furnace, and the adjacent and edge areas are cooled by the cooling module. This achieves a differential annealing process where the cooling rate of the interlocking surface area is less than that of the adjacent and edge areas. This differential annealing process reduces internal stress defects caused by surface shrinkage and internal stretching and ensures the stability of the PMMA composite.

10. The method for preparing PMMA dental restorative crowns and bridges according to claim 1, characterized in that, The steps of transferring the mold to a low-temperature environment and applying ultrasonic treatment include: Within the first time range of ultrasonic treatment, the highest power ultrasonic treatment is maintained to efficiently disperse the agglomerates of fumed silica filler, eliminate bubble nuclei generated by polymerization reaction, and promote the uniform dispersion of nano-pigment powder through ultrasonic cavitation effect and mechanical vibration. Within the second time range of ultrasonic treatment, the system temperature drop rate is monitored in real time. When the temperature drops below the heating-induced temperature, the system switches to a second low-power ultrasonic treatment and maintains a linear reduction rate of the second low power according to the temperature drop rate to ensure a stable temperature decrease and gentle heat dissipation.

11. The method for preparing PMMA dental restorative crowns and bridges according to claim 8, characterized in that: The premixed slurry is poured into a continuous steel strip mold, and the continuous steel strip moves continuously at an adjustable speed of 0.5-2m / min; The speed of the continuous steel belt is reduced when the temperature of the premixed slurry exceeds the set heating temperature in the heating section and shows a rapid upward trend, so as to prolong the residence time of the premixed slurry in the heating section and the ultrasonic section. The system temperature is checked once every unit of time until the slurry is completely cured.

12. A device for preparing PMMA dental restorative crowns and bridges, characterized in that, A method for preparing a PMMA dental restorative crown and bridge according to any one of claims 1 to 11, the preparation apparatus comprising: The premixing module places methyl methacrylate monomer, polymerization initiator, nano pigment powder, and fumed silica filler in a container and mechanically stirs them to form a uniformly mixed premixed slurry. The heating module is used to pour the premixed slurry into the mold and then place it in the heating device, which heats the slurry to initiate the polymerization reaction of the premixed slurry. The temperature rise rate determination module obtains the system temperature of the premixed slurry. When the system temperature exceeds the heating temperature of the heating device and the system temperature rise rate reaches a preset threshold, the heating of the heating device is terminated. The uniform dispersion module transfers the mold to a low-temperature environment and applies ultrasonic treatment. The low-temperature environment reduces the system temperature of the premixed slurry to suppress the polymerization reaction rate. The ultrasonic treatment allows the premixed slurry to undergo a uniform dispersion once after a polymerization reaction. The process of heating the module to the uniform dispersion module is repeated. Each time the heating module to the uniform dispersion module cycle is performed, the polymerization reaction of the premixed slurry is advanced once. After the premixed slurry is completely cured in the curing module, a PMMA composite is obtained.

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