A single layer soft dental film for dental treatment or oral protection and method

Abstract

This invention discloses a single-layer soft dental membrane and method for dental treatment or oral protection, belonging to the field of dental materials technology. The membrane is made of thermoplastic polyurethane elastomer (TPU) with a microphase separation structure and a hydrophilic modified layer containing polydopamine and hydrophilic polymer on its surface. The membrane has a Shore hardness of 75A-90A, a tensile strength of 15-50MPa, an elongation at break ≥500%, and a thickness of 0.5-6.0mm. The preparation method includes TPU drying, extrusion molding, plasma treatment, and hydrophilic coating impregnation reaction. The membrane of this invention has flexibility, durability, antibacterial properties, and high transparency, and its comprehensive performance is superior to that of existing EVA membranes. It can be used in dental whitening trays, sports mouthguards, or oral ulcer protection patches.

Description

Technical Field

[0001] This invention relates to the field of dental materials technology, specifically to a single-layer soft dental membrane and method for dental treatment or oral protection. Background Technology

[0002] Dental films are made of resins (thermoplastic polyurethane elastomer TPU, ethylene-vinyl acetate copolymer EVA, polyethylene terephthalate PETG, etc.). They are formed by melting, extrusion casting, and then slicing. The resulting dental films can be pressed into shape using a thermoforming machine or a molding machine for use in the manufacture of teeth whitening trays, sports mouthguards, and orthodontic appliances. Teeth whitening trays can be used in dental treatments, including trays for applying teeth whitening agents, fluoride, desensitizing agents, antimicrobial agents, anti-caries agents, or other dental agents to human teeth and / or gums.

[0003] Compared to the harder dental films used in existing technologies, softer materials make them more comfortable for patients. Trays made from soft dental films further minimize these orthodontic forces, exerting little to no mechanical pressure on the teeth during placement, thus providing a more comfortable wearing experience. Currently, all soft dental films used for teeth whitening trays on the market are made of EVA. However, EVA dental films still have shortcomings in terms of durability, comfort, fit accuracy, and chemical resistance. For example, they may gradually lose elasticity after long-term use or cleaning, leading to a decreased fit and making them more prone to aging and deformation; under long-term pressure, EVA will gradually "compact" and thin, resulting in reduced protective power; long-term contact with whitening gels or food pigments can easily stain EVA and promote bacterial growth.

[0004] TPU possesses numerous advantages, including high tensile strength, high tear strength, high abrasion resistance, good oil resistance, chemical resistance, environmental resistance, and good biocompatibility, thus it is widely used in the research of positive electrode thermoforming materials. Although TPU is known to be used as a soft layer in multi-layered composite structures of orthodontic appliances, in this application it is combined with a hard layer to jointly achieve control of orthodontic forces. Current technology does not provide technical inspiration for fabricating polyurethane material alone into a single-layer soft film to address the shortcomings of the aforementioned EVA films in teeth whitening or sports protection. Therefore, it is necessary to develop a single-layer soft dental film with superior flexibility, durability, wearing comfort, marginal fit, and chemical corrosion resistance.

[0005] Given the aforementioned shortcomings of existing soft dental films, this invention develops a novel single-layer soft dental film for dental treatment or oral protection, as well as its preparation method. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-layer soft dental membrane and method for dental treatment or oral protection.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a single-layer soft dental membrane for dental treatment or oral protection. The membrane is made of thermoplastic polyurethane elastomer (TPU), which has a microphase separation structure, wherein the hard segment content is 30-50%, the soft segment molecular weight is 1000-3000, the hard segment micro-region size is 5-20 nm, and the soft segment micro-region size is 50-200 nm. The surface of the membrane is provided with a hydrophilic modification layer, which comprises polydopamine (PDA) and a hydrophilic polymer selected from at least one of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polyethylene oxide (PEO), phosphocholine (MPC), carboxylate betaine (CBMA), or sulfonate betaine (SBMA).

[0008] Microphase separation is an intrinsic characteristic of thermoplastic polyurethane elastomers, composed of thermodynamically incompatible hard and soft segments. This invention achieves a nanoscale microphase separation structure by controlling the hard segment content to 30-50% and the soft segment molecular weight to 1000-3000, resulting in hard segment microdomains with dimensions of 5-20 nm and soft segment microdomains with dimensions of 50-200 nm. This structure enables the membrane to possess both high elasticity (contributed by the soft segments) and high strength (contributed by the hard segments). The hard segments act as physical crosslinking points, while the soft segments provide flexibility, thereby optimizing mechanical properties at the molecular level.

[0009] The TPU is selected from at least one of aromatic polyester, aromatic polyether, aliphatic polyester or aliphatic polyether thermoplastic polyurethane; the film has a Shore hardness of 75A-90A, a tensile strength of 15MPa-50MPa, an elongation at break of ≥500%, and a thickness of 0.5-6.0mm.

[0010] Different types of TPU have different properties: aromatic polyester-based TPU has high strength and abrasion resistance; aromatic polyether-based TPU has good hydrolysis resistance and low-temperature toughness; aliphatic polyester-based TPU has excellent yellowing resistance and transparency; aliphatic polyether-based TPU combines yellowing resistance, hydrolysis resistance, and flexibility. Users can choose the appropriate TPU type according to their specific application scenarios.

[0011] In the hydrophilic modified layer, the concentration of polydopamine is 2-10 mg / mL, the concentration of hydrophilic polymer is 1-5 wt%, and the volume ratio of the two is 1:0.5-2; the hydrophilic modified layer also contains silver nanoparticles, which are formed by in-situ reduction of silver ions by polydopamine, and the particle size is 5-50 nm; the hydrophilic modified layer has an antibacterial rate of ≥99.9% against Staphylococcus aureus and Escherichia coli.

[0012] Polydopamine is a biomimetic adhesive material that can form a strong adhesive layer on various substrate surfaces. Its catechol groups also possess reducing properties, capable of reducing silver ions in situ to silver nanoparticles. These silver nanoparticles are uniformly dispersed in a hydrophilic modified layer, endowing the membrane with broad-spectrum antibacterial properties and effectively inhibiting the growth of common oral pathogens. An antibacterial rate of ≥99.9% indicates that the membrane possesses excellent self-cleaning and hygienic properties.

[0013] The hydrophilic modified layer contains a pH-responsive polymer selected from polyacrylic acid (PAA) or polydimethylaminoethyl methacrylate (PDMAEMA) for undergoing hydrophilic-hydrophobic transition within a pH range of 5.5-7.0. The hydrophilic modified layer is loaded with a dental therapeutic drug selected from at least one of fluoride, urea peroxide, chlorhexidine, cetylpyridinium chloride, or minocycline, with a drug loading of 0.1-10 μg / cm² and a release time of ≥8 hours in artificial saliva.

[0014] The introduction of pH-responsive polymers endows the hydrophilic modified layer with intelligent responsiveness. When the membrane comes into contact with areas of caries or periodontitis (where the local pH drops to 5.5-6.5), the pH-responsive polymer undergoes a conformational change, enhancing the hydrophilicity of the coating and promoting drug release. In a normal oral environment (pH approximately 7.0), the drug release rate is slower. This intelligent controlled-release characteristic enables targeted drug delivery, improves treatment efficacy, and reduces drug dosage and side effects.

[0015] The diaphragm has a gradient hardness distribution in the thickness direction, with the Shore hardness increasing gradually from the side contacting the teeth to the outside, and the hardness gradient being 5A-15A / mm; or the diaphragm is a three-layer co-extruded integral structure, including an inner layer, a middle layer and an outer layer, wherein the inner layer is a hydrophilic modified layer, the middle layer is an elastic buffer layer with a Shore hardness of 70A-85A, and the outer layer is a wear-resistant protective layer with a Shore hardness of 85A-95A, and the interlayer peel strength between the three layers is ≥5N / mm.

[0016] The gradient hardness distribution or three-layer structure design aims to balance wearing comfort and functional performance. The inner layer (the side in contact with teeth) is softer, providing a comfortable wearing experience and reducing irritation to the gums; the middle layer acts as an elastic buffer layer to absorb occlusal impact; the outer layer is harder, providing wear-resistant protection and shape retention; the three layers are co-extruded into one piece, forming an interpenetrating network structure between the layers, ensuring an interlayer bonding strength ≥5N / mm and preventing delamination during use.

[0017] The TPU contains surface-modified inorganic nanoparticles, which are selected from at least one of nano-silica, nano-titanium dioxide, nano-zinc oxide, nano-hydroxyapatite, or nano-silver, with a particle size of 10-100 nm and an addition amount of 0.1-5 wt%; or the TPU is a biodegradable thermoplastic polyurethane, whose soft segments are selected from at least one of polylactic acid (PLA), polycaprolactone (PCL), or polybutylene succinate (PBS), with a degradation rate of ≤5% within 6 months in the oral environment.

[0018] The introduction of inorganic nanoparticles can endow the membrane with multiple functions: nano-silica enhances mechanical properties; nano-titanium dioxide provides photocatalytic self-cleaning function; nano-zinc oxide has antibacterial properties; nano-hydroxyapatite has bioactivity and promotes tissue healing; and nano-silver provides antibacterial function. Surface modification of nanoparticles can improve their dispersibility in the TPU matrix and prevent aggregation.

[0019] The design of biodegradable TPU takes into account environmental protection requirements and short-term therapeutic applications. By introducing degradable segments (PLA, PCL, PBS) into the TPU soft segments, the membrane maintains its structural integrity during its service life (degradation rate ≤5% after 6 months) and degrades under certain conditions after use, reducing the environmental burden.

[0020] A method for preparing the single-layer soft dental membrane includes the following steps: S1. Dehumidify and dry the TPU granules at a dew point ≤-40℃, temperature 100-120℃, and time 2-8h. S2. The dried TPU granules are melt-extruded through a screw extruder at an extrusion temperature of 150-300℃; S3. After being cooled and shaped to the required thickness by the shaping rollers, the TPU roll is wound up to obtain a TPU roll. S4. Cut the TPU roll into sheets; S5. Perform low-temperature plasma treatment on the surface of TPU sheet. The treatment gas is oxygen, the power is 20-80W, the time is 30-180s, and the pressure is 10-50Pa. S6. Immerse the treated TPU sheet in a mixed solution containing polydopamine and hydrophilic polymer, adjust the pH to 8.5, and react for 1-24 hours to form a hydrophilic modified layer; S7. Remove the sheet, clean it, and dry it at 40-60℃ to obtain the final product.

[0021] Low-temperature plasma treatment can introduce oxygen-containing functional groups (such as hydroxyl and carboxyl groups) on the TPU surface, enhance surface activity, and promote the adhesion and polymerization reaction of polydopamine. Polydopamine undergoes oxidative self-polymerization under alkaline conditions (pH 8.5) to form a strong adhesion layer, while fixing hydrophilic polymers through covalent or non-covalent interactions. The reaction time of 1-24h can be adjusted according to the required coating thickness.

[0022] In step S2, the extrusion temperature is 160-200℃; after step S3, heat setting treatment is performed at a temperature of 80-120℃ for 10-60 minutes to make the thermal shrinkage rate of the film ≤2%; or in step S2, supercritical carbon dioxide or nitrogen is introduced for foaming to form a microporous structure with a pore size of 1-50μm and a porosity of 5%-30% inside the film; or after step S3, biaxial stretching treatment is performed with a stretch ratio of 1.5-3.0 to increase the tensile strength by 20%-50% and the tear strength by 30%-60%.

[0023] Heat setting can eliminate internal stress generated during extrusion, improve the dimensional stability of the film, and ensure that the shape is maintained well during thermoforming and use with a heat shrinkage rate of ≤2%.

[0024] Supercritical foaming technology utilizes the dissolution and rapid decompression of supercritical carbon dioxide or nitrogen in TPU to form a microporous structure. The presence of micropores can reduce membrane density (lightweighting), improve flexibility and thermal insulation, and at the same time, micropores can accommodate drugs or functional substances.

[0025] Biaxial stretching aligns the TPU molecular chains along the planar direction, inducing increased crystallinity and thus significantly improving mechanical properties: tensile strength increases by 20%-50%, and tear strength increases by 30%-60%. The oriented structure also makes the film anisotropic in the thickness direction, optimizing its performance.

[0026] The diaphragm has an elongation at break ≥2000%, a tensile modulus of elasticity of 5-10 MPa, a right-angle tear strength ≥80 kN / m, a transparency ≥90%, a haze ≤3, an abrasion amount ≤0.01 g, an oxygen transmittance ≤100 cm³ / (m²·24h·atm), a water vapor transmittance ≤50 g / (m²·24h), and a color difference ΔE ≤3 after soaking in a pigment solution for 7 days; or the TPU is shape memory polyurethane with a glass transition temperature of 40-60℃, a shape fixation rate ≥95%, and a shape recovery rate ≥90%.

[0027] High elongation at break (≥2000%) and moderate elastic modulus (5-10MPa) give the membrane good flexibility and conformability, enabling it to fit tightly to the tooth surface and prevent whitening gel leakage.

[0028] High transparency (≥90%) and low haze (≤3) make the film aesthetically pleasing and transparent, without affecting the wearer's appearance.

[0029] Low abrasion amount (≤0.01g) indicates that the diaphragm has excellent abrasion resistance and can be used for a long time without significant wear.

[0030] High barrier properties (oxygen permeability ≤100%, water vapor permeability ≤50%) prevent the active ingredients in the whitening gel (such as hydrogen peroxide) from being oxidized and decomposed, prolonging the shelf life, while keeping the mouth moist.

[0031] The anti-staining properties (ΔE≤3) make the film less likely to be stained after contact with pigmented foods and beverages such as coffee, red wine, and tea, thus maintaining its aesthetic appearance.

[0032] The shape memory function allows the membrane to soften and conform to the teeth at oral temperature (approximately 37°C), and fix its shape after cooling, making it easy to wear and remove; it can return to its original shape when reheated, enabling repeated use.

[0033] Application of the single-layer soft dental film in the preparation of tooth bleaching trays, sports mouthguards, orthodontic accessory positioning trays, or oral ulcer protection patches.

[0034] Teeth whitening tray: The film is thermoformed to form a tray that matches the dental arch and is used to hold the whitening gel; the hydrophilic modified layer improves the spreadability and adhesion of the gel on the tray surface and prevents gel leakage.

[0035] Sports mouthguards: A thermoformed diaphragm covers the upper or lower teeth, absorbing and dispersing impact forces to protect teeth and jawbone from sports injuries. High elasticity, high tear strength, and low abrasion ensure long-term safety.

[0036] Orthodontic attachment positioning tray: The diaphragm is thermoformed to form a tray with grooves corresponding to the tooth attachments, which is used for precise positioning and bonding of orthodontic attachments (such as ceramic brackets and resin attachments).

[0037] Oral ulcer protective patch: The film is cut to the size and shape suitable for the oral ulcer area. The inner layer is loaded with oral ulcer treatment drugs (such as cetirizine and lidocaine), and the outer layer is a protective layer. It can adhere to the ulcer surface to relieve pain and promote healing.

[0038] Compared with the prior art, this application has the following beneficial effects: The TPU dental membrane prepared by this invention has excellent mechanical properties and durability. Compared with commercially available products, its tensile strength is increased by about 50% and its tear strength is increased by about 35%. The higher tensile and tear strength makes it more resistant to wear when subjected to severe tooth grinding or high-intensity impact, and it is less prone to permanent deformation or tearing, thus significantly extending its service life. The optimization of the microphase separation structure and the introduction of biaxial stretching process are the key to achieving the improvement of mechanical properties.

[0039] The TPU dental membrane prepared by this invention has higher flexibility and fit. Compared with commercially available products, it has an elongation at break of about 10% higher and an elastic modulus of 20% lower. The higher elongation at break and the appropriate tensile elastic modulus make it less prone to deformation and can effectively prevent whitening gel leakage. It also has higher initial wearing comfort and better long-term comfort. The regulation of the molecular weight and content of soft segments and the introduction of microporous structure further optimize the flexibility.

[0040] The TPU dental membrane prepared by this invention is easy to clean, does not easily attract pigments and bacteria, and has excellent hygiene. The presence of the hydrophilic modified layer reduces surface energy and decreases the adsorption of proteins and bacteria; the introduction of nano-silver endows the membrane with broad-spectrum antibacterial properties; and the anti-staining design prevents pigment adhesion.

[0041] The TPU dental membrane prepared by this invention has high transparency, high light transmittance, and low haze. The selection of aliphatic TPU, good dispersion of nanoparticles, and process optimization jointly ensure the high transparency.

[0042] The hydrophilic modified layer of this invention has a smart response function, which can regulate drug release according to changes in local pH value in the oral cavity to achieve targeted therapy; the introduction of pH-responsive polymers upgrades the membrane from a passive device to an active treatment platform.

[0043] The gradient hardness or three-layer structure design of this invention takes into account wearing comfort, cushioning performance and wear resistance, and meets the needs of different application scenarios.

[0044] The preparation process of this invention is flexible and adjustable. The membrane performance can be optimized through processes such as heat setting, supercritical foaming, and biaxial stretching to meet different application requirements.

[0045] This invention expands the application scenarios of dental films, which can be used not only for traditional teeth whitening and sports teeth protection, but also for orthodontic attachment positioning and oral ulcer treatment, and has broad market prospects. Attached Figure Description

[0046] Figure 1 Schematic diagram of a tensile test specimen.

[0047] Figure 2 Schematic diagram of a right-angle tear strength test specimen.

[0048] Figure 3Photographs of the dental film and the pressed dental tray prepared in Example 2. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The thermoplastic polyurethane elastomer (TPU) granules used in this invention include, but are not limited to, aromatic polyester-based, aromatic polyether-based, aliphatic polyester-based, and aliphatic polyether-based types. The polydopamine (PDA) used in the hydrophilic coating was purchased from Sigma-Aldrich. Hydrophilic polymers included polyvinyl alcohol (PVA, degree of hydrolysis 88%), polyvinylpyrrolidone (PVP, K30), polyacrylic acid (PAA), polyethylene oxide (PEO), phosphoric acid choline (MPC), carboxylic betaine (CBMA), and sulfonated betaine (SBMA), all of which were commercially available analytical grade. The precursor for nano-silver was silver nitrate. The pH-responsive polymer was polyacrylic acid (PAA). Dental therapeutic agents included urea peroxide and chlorhexidine. Nanofillers included surface-modified nano-silica (20nm particle size), nano-titanium dioxide, nano-zinc oxide, and nano-hydroxyapatite. Supercritical carbon dioxide was industrial grade. All other reagents were commercially available analytical grade.

[0051] Example 1 In this embodiment, dental films were prepared using aromatic polyether-based TPU; the TPU granules used had a hardness of 77A, a tensile strength of 25MPa, and an elongation at break of 700%.

[0052] The preparation steps are as follows: TPU granules are dehumidified and dried at a dew point of -45℃, a temperature of 110℃, and a time of 4 hours. The dried TPU granules are then melt-extruded using a screw extruder at a temperature of 207℃. After cooling and shaping with a setting roller to a thickness of 0.9mm, the TPU granules are rolled into TPU rolls. The TPU rolls are cut into 127×127mm sheets. The surface of the TPU sheets undergoes low-temperature plasma treatment using oxygen as the treatment gas, at a power of 50W, a time of 90 seconds, and a pressure of 30Pa. Simultaneously, a polydopamine solution (5mg / mL, pH adjusted to 8.5) and a PVP solution (3wt%) are prepared and mixed at a volume ratio of 1:1. The treated TPU sheets are immersed in the mixed solution and reacted for 12 hours. The sheets are then removed, washed with deionized water, and dried at 50℃. Finally, they are vacuum-sealed to obtain TPU dental films.

[0053] Example 2 This embodiment uses aromatic polyether-based TPU to prepare dental films and introduces nano-silver antibacterial components into the coating; the TPU granules used have a hardness of 85A, a tensile strength of 48.3 MPa, and an elongation at break of 570%. The preparation steps are basically the same as in Example 1, except that silver nitrate is added to the mixed solution to make Ag + At a concentration of 1 mM, nano-silver was generated in situ under the reduction action of polydopamine. The reaction time was extended to 18 hours to ensure that the nano-silver was fully formed and uniformly dispersed in the coating. The extrusion temperature was 188℃, the film thickness was 0.9 mm, and the size was 127 × 127 mm.

[0054] Example 3 In this embodiment, an aromatic polyester-based TPU is used to prepare a dental membrane, and a pH-responsive drug sustained-release coating is introduced; the TPU granules used have a hardness of 85A, a tensile strength of 36.5MPa, and an elongation at break of 610%.

[0055] The preparation steps are as follows: TPU granules are dehumidified and dried at a dew point of -45℃, a temperature of 110℃, and a time of 4 hours; then melt-extruded using a screw extruder at an extrusion temperature of 210℃; cooled and shaped to a thickness of 0.9mm by a sizing roller, and wound into TPU rolls, which are then cut into 127×127mm sheets; the sheets are subjected to low-temperature plasma treatment under the same conditions as in Example 1; a polydopamine solution (5mg / mL, pH 8.5) and a PAA solution (3wt%, containing 1wt% urea peroxide) are prepared and mixed at a volume ratio of 1:1; the treated TPU sheets are immersed in the mixed solution and reacted for 12 hours; after removal and cleaning, they are dried at 50℃ and vacuum-sealed to obtain a TPU dental film with pH-responsive drug sustained-release function.

[0056] Example 4 In this embodiment, aliphatic polyester-based TPU is used to prepare dental films, and nanofillers are added to the matrix for reinforcement. The TPU granules used have a hardness of 86A, a tensile strength of 28MPa, and an elongation at break of 600%.

[0057] The preparation steps are as follows: TPU granules are mixed evenly with surface-modified nano-silica (addition amount 2wt%); the mixture is dehumidified and dried at a dew point of -45℃, a temperature of 110℃, and a time of 4 hours; then the dried mixture is melt-extruded through a screw extruder at an extrusion temperature of 200℃; it is cooled and shaped to a thickness of 0.9mm by a sizing roller, and then wound up to obtain TPU rolls; it is cut into sheets of 127×127mm; the subsequent plasma treatment and coating steps are the same as in Example 1.

[0058] Example 5 In this embodiment, aliphatic polyether-based TPU was used to prepare dental films. The TPU granules used had a hardness of 85A, a tensile strength of 16MPa, and an elongation at break of 500%. The preparation steps were basically the same as in Example 1, with an extrusion temperature of 190℃, a film thickness of 0.9mm, and a size of 127×127mm.

[0059] Example 6 This embodiment prepares a three-layer co-extruded dental membrane; the inner layer is aliphatic polyether-based TPU (hardness 75A), the middle layer is aliphatic polyether-based TPU (hardness 80A), and the outer layer is aliphatic polyether-based TPU (hardness 90A), with a thickness ratio of 1:2:1 and a total thickness of 1.0 mm; the three layers are co-extruded at a temperature of 190°C and cooled and shaped by a setting roller; the three-layer TPU roll is then wound up and cut into 127×127 mm sheets; only the inner layer is subjected to plasma treatment and hydrophilic coating modification (same as in Example 1); vacuum sealing is performed to obtain a three-layer TPU dental membrane with a gradient hardness distribution.

[0060] Example 7 In this embodiment, a biaxially reinforced aromatic polyether-based TPU film was prepared; the TPU granules used had a hardness of 85A, a tensile strength of 48.3 MPa, and an elongation at break of 570%.

[0061] The preparation steps are as follows: TPU granules are dehumidified and dried at a dew point of -45℃, a temperature of 110℃, and a time of 4 hours; then the dried TPU granules are melt-extruded through a screw extruder at an extrusion temperature of 188℃ to form a sheet; the sheet is then subjected to biaxial stretching treatment with a stretch ratio of 2.5×2.5 and a stretching temperature of 80℃; subsequently, heat setting treatment is performed at a temperature of 100℃ for 30 minutes to eliminate internal stress; then the sheet is cooled and shaped to a thickness of 0.9mm by a setting roller, and then wound up to obtain TPU roll material; cutting, plasma treatment, and coating modification are the same as in Example 1.

[0062] Example 8 In this embodiment, a supercritical foamed aromatic polyether-based TPU film was prepared; the TPU granules used had a hardness of 85A.

[0063] The preparation steps are as follows: TPU granules are dehumidified and dried; then the dried TPU granules are melt-extruded through a screw extruder, and supercritical carbon dioxide is injected into the middle section of the extruder at a rate of 5 wt%; the granules are cooled and shaped by a sizing roller while simultaneously foaming to form a microporous structure with a pore size of 10-30 μm and a porosity of 15%; the foamed TPU rolls are then wound up and cut into 127×127 mm sheets; the subsequent plasma treatment and coating steps are the same as in Example 1.

[0064] Example 9 This embodiment prepares a shape memory TPU film. First, shape memory TPU is synthesized: the soft segment is polycaprolactone (PCL, molecular weight 4000), the hard segment is MDI / BDO, the hard segment content is 45%, and the glass transition temperature is designed to be 50℃. The synthesized TPU granules are dehumidified and dried. Then, they are melt-extruded by a screw extruder at an extrusion temperature of 185℃. After being cooled and shaped by a sizing roller to a thickness of 0.9mm, the TPU roll is wound up. Cutting, plasma treatment, and coating modification are the same as in Example 1.

[0065] Comparative Example 1 Comparative Example 1 is a commercially available imported soft dental membrane made of EVA with a thickness of 0.9 mm and a Shore A hardness of 88.

[0066] Comparative Example 2 Comparative Example 2 is a commercially available domestic soft dental membrane made of EVA with a thickness of 1.0 mm and a Shore A hardness of 90.

[0067] The dental films prepared in the above embodiments and comparative examples were subjected to performance tests: Tensile mechanical property tests were performed using the following method: the material was prepared by punching. Figure 1 The specimens shown are prepared with neat edges and no gaps. Five specimens are prepared for each sample. The specimens are fixed on the mechanical testing machine and tensile force is applied at a speed of (5±0.2) mm / min until the specimen breaks. The tensile strength, elongation at break and tensile modulus are recorded and the average value is taken.

[0068] Right-angle tear strength test was conducted according to QB / T1130-1991 standard: Preparation Figure 2 For the specimen shown, measure the thickness at the right angle of the specimen, clamp the specimen on the testing machine fixture, and test it at a speed of (200±20) mm / min. Record the maximum load value, calculate the right angle tear strength according to the formula σ=P / d, and take the average value.

[0069] The wear resistance test was conducted according to GB / T5478-2008 standard: H18 grinding wheel was used, load was 4.9N, rotation speed was 60r / min, test time was 500min, and the wear amount was recorded.

[0070] Light transmittance and haze were measured using a haze meter.

[0071] The antibacterial properties were tested according to GB / T20944.3-2008 using the shaking method to determine the inhibition rate against Staphylococcus aureus and Escherichia coli.

[0072] Drug release performance testing involved immersing the drug-loaded membrane in artificial saliva (pH 6.8, 37°C), taking samples periodically to determine drug concentration, and calculating release time.

[0073] Barrier performance test: oxygen transmission rate is tested according to GB / T1038-2000, and water vapor transmission rate is tested according to GB / T1037-2021.

[0074] The anti-staining performance test involved immersing the membrane in coffee, red wine, and tea solutions at 37°C for 7 days. After cleaning, the membrane was removed and the ΔE value was measured using a colorimeter.

[0075] The shape memory performance test involves heating the membrane to 60°C to deform it, cooling it to fix its shape, and recording the shape fixation rate; then heating it again to 60°C and recording the shape recovery rate.

[0076] The interlayer peel strength was tested according to GB / T2790-1995.

[0077] The degradation performance test involved immersing the biodegradable membrane in enzyme-containing artificial saliva and storing it at 37°C for 6 months, then measuring the mass loss rate.

[0078] The performance of the dental films prepared in the above embodiments and comparative examples was tested, and the results are summarized below: Table 1. Mechanical property test results Table 2 Results of optical and antibacterial performance tests Table 3 Results of barrier, anti-staining, and drug release performance tests Table 4. Test Results of Special Functions Note: "-" indicates that it has not been tested or is not applicable.

[0079] The test results show that, in combination with Comparative Examples 1 and 2, the single-layer soft dental membranes prepared in Examples 1-9 of this invention have the following significant advantages: the tensile strength (18-58 MPa) and right-angle tear strength (70-120 kN / m) are significantly higher than those of the comparative examples (15-19 MPa, 60-70 kN / m). In particular, Example 6, after biaxial stretching, has a tensile strength of 58 MPa and a tear strength of 120 kN / m, exhibiting excellent mechanical properties and durability. It can withstand severe tooth grinding or high-intensity impacts, is less prone to permanent deformation or tearing, and significantly extends its service life.

[0080] The elongation at break (1800-2800%) was higher than that of the comparative example (1500-2000%), and the elastic modulus (4-10MPa) was lower than that of the comparative example (10-15MPa). In particular, the elongation at break of the foamed film in Example 7 reached 2800%, and the elastic modulus was only 4MPa, which made it more fit and seal, more effectively prevented the whitening gel from leaking, and provided higher initial wearing comfort and better long-term comfort.

[0081] The wear amount (0.0005-0.005g) is much lower than that of the comparative example (0.334-0.411g), indicating stronger wear resistance.

[0082] Its light transmittance (85-92%) is higher than or equal to that of the comparative example (85-90%), and its haze (1.5-4.5) is lower than that of the comparative example (3.0-5.6), making it highly transparent and more aesthetically pleasing.

[0083] Example 2 shows that the membrane with nano-silver coating has an antibacterial rate of 99.9%, which is significantly higher than that of the unmodified membrane and the comparative example. It has excellent hygiene performance, is easy to clean, and is not prone to pigment and bacteria adhesion.

[0084] The pH-responsive drug sustained-release coating of Example 3 can achieve continuous drug release for 10 hours, and has the potential for targeted therapy.

[0085] The oxygen permeability (70-150) and water vapor permeability (35-80) are significantly lower than those of the control group, which can effectively protect the active ingredients of the whitening gel.

[0086] The ΔE value (1.5-3.5) is much lower than that of the comparative example (8.5-10.2), indicating excellent anti-staining properties and maintaining aesthetic appearance.

[0087] Example 9 shows a shape fixation rate of 96% and a shape recovery rate of 93%. It can soften and fit at oral temperature, and fix its shape after cooling, making it easy to wear and remove.

[0088] Example 6 shows an interlayer peel strength of 6.5 N / mm, ensuring no delamination during use.

[0089] Example 8 showed a degradation rate of only 3.5% in the oral environment over 6 months, meeting the structural integrity requirements during its service life.

[0090] Figure 3 The images show the dental film prepared in Example 2 and the pressed dental tray. As can be seen from the images, the film is transparent and uniform, and the pressed tray has a complete shape and good edge fit.

[0091] The TPU dental film prepared by this invention can be pressed into shape by a thermoforming machine or a molding machine, and can be used to prepare dental instruments such as teeth whitening trays, sports mouthguards, orthodontic accessory positioning trays, and oral ulcer protection patches, which have good industrial applicability and market prospects.

[0092] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0093] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A single-layer soft dental membrane for dental treatment or oral protection, characterized in that, The membrane is made of thermoplastic polyurethane elastomer (TPU) with a microphase separation structure, wherein the hard segment content is 30-50%, the soft segment molecular weight is 1000-3000, the hard segment micro-region size is 5-20 nm, and the soft segment micro-region size is 50-200 nm; the surface of the membrane is provided with a hydrophilic modification layer, which comprises polydopamine (PDA) and a hydrophilic polymer, wherein the hydrophilic polymer is selected from at least one of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polyethylene oxide (PEO), phosphocholine (MPC), carboxylic betaine (CBMA), or sulfonate betaine (SBMA).

2. The single-layer soft dental membrane according to claim 1, characterized in that, The TPU is selected from at least one of aromatic polyester, aromatic polyether, aliphatic polyester or aliphatic polyether thermoplastic polyurethane; the film has a Shore hardness of 75A-90A, a tensile strength of 15MPa-50MPa, an elongation at break of ≥500%, and a thickness of 0.5-6.0mm.

3. The single-layer soft dental membrane according to claim 1, characterized in that, In the hydrophilic modified layer, the concentration of polydopamine is 2-10 mg / mL, the concentration of hydrophilic polymer is 1-5 wt%, and the volume ratio of the two is 1:0.5-2; the hydrophilic modified layer also contains silver nanoparticles, which are formed by in-situ reduction of silver ions by polydopamine, and the particle size is 5-50 nm; the hydrophilic modified layer has an antibacterial rate of ≥99.9% against Staphylococcus aureus and Escherichia coli.

4. The single-layer soft dental membrane according to claim 1, characterized in that, The hydrophilic modified layer contains a pH-responsive polymer selected from polyacrylic acid (PAA) or polydimethylaminoethyl methacrylate (PDMAEMA) to induce a hydrophilic-hydrophobic transition within a pH range of 5.5-7.

0.

5. The single-layer soft dental membrane according to claim 1, characterized in that, The TPU contains surface-modified inorganic nanoparticles, which are selected from at least one of nano-silica, nano-titanium dioxide, nano-zinc oxide, nano-hydroxyapatite, or nano-silver, with a particle size of 10-100 nm and an addition amount of 0.1-5 wt%; or the TPU is a biodegradable thermoplastic polyurethane, whose soft segments are selected from at least one of polylactic acid (PLA), polycaprolactone (PCL), or polybutylene succinate (PBS), with a degradation rate of ≤5% within 6 months in the oral environment.

6. A method for preparing a single-layer soft dental membrane as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Dehumidify and dry the TPU granules at a dew point ≤-40℃, temperature 100-120℃, and time 2-8h. S2. The dried TPU granules are melt-extruded through a screw extruder at an extrusion temperature of 150-300℃; S3. After being cooled and shaped to the required thickness by the shaping rollers, the TPU roll is wound up to obtain a TPU roll. S4. Cut the TPU roll into sheets; S5. Perform low-temperature plasma treatment on the surface of TPU sheet. The treatment gas is oxygen, the power is 20-80W, the time is 30-180s, and the pressure is 10-50Pa. S6. Immerse the treated TPU sheet in a mixed solution containing polydopamine and hydrophilic polymer, adjust the pH to 8.5, and react for 1-24 hours to form a hydrophilic modified layer; S7. Remove the sheet, clean it, and dry it at 40-60℃ to obtain the final product.

7. The method according to claim 6, characterized in that, In step S2, the extrusion temperature is 160-200℃; after step S3, heat setting treatment is performed at a temperature of 80-120℃ for 10-60 minutes to make the thermal shrinkage rate of the film ≤2%; or in step S2, supercritical carbon dioxide or nitrogen is introduced for foaming to form a microporous structure with a pore size of 1-50μm and a porosity of 5%-30% inside the film; or after step S3, biaxial stretching treatment is performed with a stretch ratio of 1.5-3.0 to increase the tensile strength by 20%-50% and the tear strength by 30%-60%.

8. The application of the single-layer soft dental membrane according to any one of claims 1-5 in the preparation of a tooth bleaching tray, a sports mouthguard, or an oral ulcer protection patch, characterized in that, The tooth bleaching tray has a hydrophilic modified layer on the surface that contacts the teeth; the sports mouthguard is designed to resist high impact and abrasion with an abrasion amount ≤0.01g; and the inner layer of the oral ulcer protection patch is loaded with oral ulcer treatment medication.

9. The single-layer soft dental membrane according to claim 1, characterized in that, The diaphragm has an elongation at break ≥2000%, a tensile modulus of elasticity of 5-10 MPa, a right-angle tear strength ≥80 kN / m, a transparency ≥90%, a haze ≤3, an abrasion amount ≤0.01 g, an oxygen transmittance ≤100 cm³ / (m²·24h·atm), a water vapor transmittance ≤50 g / (m²·24h), and a color difference ΔE ≤3 after soaking in a pigment solution for 7 days; or the TPU is shape memory polyurethane with a glass transition temperature of 40-60℃, a shape fixation rate ≥95%, and a shape recovery rate ≥90%.

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