Multifunctional nanocomposite coating and manufacturing method thereof

Abstract

The present invention relates to a coating technology for clear aligners, and more specifically, to a multifunctional nanocomposite coating capable of improving oral moisture resistance and mechanical strength while simultaneously providing antibacterial properties, self-healing properties, pH responsiveness, and smart monitoring functions, a clear aligner having the same, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to a coating technology for clear aligners, and more specifically, to a multifunctional nanocomposite coating capable of improving oral moisture resistance and mechanical strength while simultaneously providing antibacterial properties, self-healing properties, pH responsiveness, and smart monitoring functions, a clear aligner having the same, and a method for manufacturing the same. Background Technology

[0003] Transparent braces are an innovative dental orthodontic technology developed to address the aesthetic drawbacks of traditional orthodontic treatment using metal brackets and wires. Made of transparent plastic, these devices are barely visible when worn while applying appropriate corrective force to move teeth to desired positions. They are particularly popular among adult patients, and their application is rapidly expanding due to recent advancements in 3D printing technology that enable customized fabrication for individual patients.

[0004] The manufacturing of clear aligners is primarily based on 3D printing technology using photocurable resins. Generally, a tooth movement plan is established based on 3D data obtained by scanning the patient's oral cavity, and the necessary orthodontic devices for each stage are digitally designed and then printed using a DLP or SLA 3D printer. While this manufacturing method has the advantage of being precisely customized to the individual patient's tooth shape, various problems may arise during long-term oral use due to the physical limitations of the photocurable resins used.

[0005] One of the major challenges faced by clear aligners is a lack of mechanical strength and moisture resistance. The oral environment is an extremely humid one, characterized by high temperatures of 35–40°C and relative humidity approaching 100%. Furthermore, continuous mechanical stress generated during chewing and wear from repeated insertion and removal are applied. In such an environment, clear aligners may experience problems such as swelling due to moisture absorption, deterioration of mechanical properties, increased surface roughness, and reduced transparency. In particular, moisture penetration can alter the molecular structure within the material, leading to a decrease in orthodontic force and deformation, which can directly affect treatment efficacy.

[0006] The oral bacterial environment also poses a serious challenge to clear aligners. If pathogenic bacteria, such as Streptococcus mutans and Porphyromonas gingivalis, adhere to the surface of clear aligners and form a biofilm, they can cause oral diseases such as cavities, gingivitis, and bad breath. In particular, due to the nature of clear aligners requiring 20 to 22 hours of daily wear, the oral self-cleaning mechanism is limited, which can create an environment even more vulnerable to bacterial proliferation. This problem not only worsens the patient's oral health but can also impede the effectiveness of the orthodontic treatment itself.

[0007] Previously, various approaches have been attempted to address these problems. Structural improvement measures such as increasing the thickness of clear aligners or applying multi-layer sheets were proposed, but these entailed side effects such as reduced comfort and decreased aesthetics. Surface treatment methods such as plasma treatment, chemical etching, and UV irradiation were applied, but they showed limitations in terms of limited effectiveness and lack of durability.

[0008] Various approaches utilizing coating technology have also been studied. Silicon-based coatings offer excellent biocompatibility but suffer from insufficient mechanical strength and weak adhesion. Acrylic-based coatings exhibit high hardness but have the disadvantage of being brittle and prone to cracking. Fluorine coatings provide antibacterial effects but suffer from short durability and concerns regarding toxicity. To overcome the limitations of these single-material coatings, research on composite coatings has been conducted; however, practical application remains difficult due to insufficient interlayer adhesion and the complexity of manufacturing processes.

[0009] Recently, with the advancement of nanotechnology, interest in functional coatings using nanoparticles has been increasing. While research on antimicrobial coatings using silver nanoparticles, titanium dioxide nanoparticles, and zinc oxide nanoparticles is actively underway, actual clinical application is currently limited due to issues with nanoparticle aggregation and concerns regarding biosafety. Furthermore, most research focuses on a single function, which limits its ability to satisfy the complex performance requirements demanded by clear aligners.

[0010] With increasing interest in smart medical devices, attempts are emerging to incorporate monitoring functions into clear aligners. Research is being conducted on clear aligners with built-in sensors and devices equipped with pressure sensing capabilities; however, they face limitations in practicality due to sensor size and power supply issues. Furthermore, concerns regarding biocompatibility and safety are being raised when complex electronic circuits are included.

[0011] In the field of surface treatment technology, atomic layer deposition (ALD) and chemical vapor deposition (CVD) are attracting attention. ALD is beginning to be applied in the medical device sector due to its advantages, such as the ability to control thickness at the atomic layer level and apply uniform coatings even to complex three-dimensional shapes. Parylene coatings produced using CVD are widely used as protective films for medical implants and electronic devices due to their excellent biocompatibility and barrier properties. However, research on applying these technologies to clear aligners is still in its early stages.

[0012] In the field of inorganic thin film technology, ceramic materials such as alumina, titanium dioxide, and zirconium dioxide are attracting attention for their excellent barrier properties and biocompatibility. In particular, alumina thin films formed by atomic layer deposition exhibit very low water vapor permeability and are widely utilized in encapsulation technology. Titanium dioxide is being studied in various application fields due to its excellent optical properties resulting from its high refractive index, along with antibacterial effects utilizing its photocatalytic properties.

[0013] Parylene is recognized as a representative material in organic thin film technology. Parylene exhibits ideal characteristics for medical device coatings, as it can be deposited at room temperature and form dense, pinhole-free films. In particular, Parylene C displays low moisture permeability and excellent mechanical properties due to chlorine atoms, but concerns have been raised regarding chlorine leaching within the body. Parylene N shows superior biocompatibility but exhibits relatively inferior barrier properties.

[0014] With the advancement of nanomaterial technology, new functional nanomaterials such as graphene quantum dots, bioglass, and fluorescent nanodiamonds are being developed. Graphene quantum dots exhibit excellent electrical and optical properties and have the advantage of being able to impart various functions through surface modification. Bioglass is attracting attention as a bioactive material capable of promoting tooth remineralization by releasing calcium and phosphate ions. Fluorescent nanodiamonds are being researched in the field of biosensors as a material possessing both stable fluorescence properties and biocompatibility.

[0015] However, most research to date has focused on individual technologies or single functions, resulting in a lack of integrated solutions capable of comprehensively addressing the complex and multifaceted performance requirements demanded by clear aligners. In particular, there has been almost no research on coating systems that can maintain biocompatibility and transparency while implementing moisture barrier, mechanical reinforcement, antibacterial properties, self-healing, pH responsiveness, and smart monitoring functions. Prior art literature

[65535] U.S. Patent Application Publication US2017 / 0159178 (June 8, 2017) Ha OY, Kim S, et al. “Binder-Free TiO₂-Cu Composite Powder Coating for Thermoformable Orthodontic Clear Aligners.” The problem to be solved

[0017] The technical problem that the present invention aims to solve is to provide a multifunctional coating system capable of resolving the durability issues of clear aligners, whose physical properties deteriorate due to oral moisture, temperature changes, and repeated attachment and detachment, while simultaneously implementing antibacterial properties, self-healing properties, pH responsiveness, and smart monitoring functions.

[0018] The technical problem that the present invention aims to solve is to significantly improve the moisture resistance of the clear aligner body so that it can maintain a stable shape and orthodontic force even during long-term use in the oral cavity. In addition, it aims to implement a system that improves mechanical strength to prevent damage that may occur during masticatory force or repeated removal and attachment, and inhibits bacterial adhesion and biofilm formation caused by increased surface roughness.

[0019] The technical problem that the present invention aims to solve is to develop an antimicrobial system capable of maintaining biocompatibility while providing a strong and sustained antimicrobial effect against pathogenic bacteria in the oral cavity. In addition, it aims to implement a self-healing function that automatically repairs micro-damage that may occur in the coating layer to maintain long-term protective performance.

[0020] The technical problem that the present invention aims to solve is to innovatively improve the adhesion between an inorganic layer and an organic layer to completely prevent interlayer delamination and secure thermal shock resistance, thereby providing simultaneous prevention of tooth decay and gum disease by selectively releasing an appropriate therapeutic substance in response to changes in oral pH.

[0021] The technical problem that the present invention aims to solve is to improve patient compliance and optimize treatment effects by implementing smart functions capable of monitoring the progress of orthodontic treatment in real time and detecting abnormal conditions within the oral cavity at an early stage. means of solving the problem

[0022] According to one aspect of the present invention, a nanocomposite coating may be provided comprising: a substrate; an inorganic layer formed on the surface of the substrate, comprising at least one of alumina (Al2O3), titanium dioxide (TiO2), and zirconium dioxide (ZrO2); and an organic layer formed on the inorganic layer, comprising a parylene polymer.

[0023] For example, a nanocomposite coating may be provided in which the inorganic layer is formed by an atomic layer deposition or sputtering method.

[0024] For example, a nanocomposite coating may be provided in which the organic layer is formed by a chemical vapor deposition method.

[0025] As an example, a nanocomposite coating may be provided in which the parylene polymer comprises at least one of parylene N, parylene C, parylene D, and parylene F.

[0026] For example, a nanocomposite coating may be provided, further comprising an intermediate interface layer formed between the inorganic layer and the organic layer, wherein the intermediate interface layer comprises a layer grafted with a silane coupling agent.

[0027] For example, a nanocomposite coating may be provided in which the silane coupling agent comprises 3-aminopropyltriethoxysilane.

[0028] For example, a nanocomposite coating may be provided, further comprising a second inorganic layer formed between the inorganic layer and the organic layer, wherein the second inorganic layer comprises at least one of silicon dioxide and tin oxide.

[0029] For example, a nanocomposite coating may be provided that further comprises fluorescent nanodiamonds dispersed in the organic layer.

[0030] For example, a nanocomposite coating may be provided in which the fluorescent nanodiamond contains a nitrogen-vacancy center.

[0031] For example, a nanocomposite coating may be provided that further comprises thermochromic liquid crystal microcapsules dispersed in the organic layer.

[0032] For example, a nanocomposite coating may be provided in which the thermochromic liquid crystal microcapsule contains a cholesteric liquid crystal.

[0033] For example, a nanocomposite coating may be provided that further comprises graphene quantum dots dispersed in the inorganic layer.

[0034] For example, a nanocomposite coating may be provided in which the graphene quantum dots are surface-modified with oxygen-containing functional groups.

[0035] For example, a nanocomposite coating may be provided that further comprises bioglass nanoparticles dispersed in the inorganic layer.

[0036] For example, a nanocomposite coating may be provided in which the bioglass nanoparticles have a SiO2-CaO-P2O5 composition.

[0037] For example, a nanocomposite coating may be provided that further comprises silver nanoparticles and a copper-chelate complex dispersed in the organic layer.

[0038] For example, a nanocomposite coating may be provided that further comprises a self-healing agent in the form of microcapsules included in the organic layer.

[0039] For example, a nanocomposite coating may be provided that further comprises chitosan-alginate hydrogel particles dispersed in the organic layer.

[0040] According to one aspect of the present invention, a transparent orthodontic device may be provided, comprising: a body of a transparent orthodontic device; an inorganic layer formed on the surface of the body, comprising at least one of alumina, titanium dioxide, and zirconium dioxide; and an organic layer formed on the inorganic layer, comprising a parylene polymer.

[0041] For example, a transparent orthodontic device may be provided in which the inorganic layer is formed by an atomic layer deposition or sputtering method.

[0042] For example, a transparent orthodontic device may be provided in which the organic layer is formed by a chemical vapor deposition method.

[0043] For example, a clear orthodontic device may be provided in which the above parylene polymer comprises at least one of parylene N, parylene C, parylene D, and parylene F.

[0044] For example, a clear orthodontic device may be provided, which further comprises an intermediate interface layer formed between the inorganic layer and the organic layer, wherein the intermediate interface layer comprises a layer in which a silane coupling agent is graft-polymerized.

[0045] For example, a clear orthodontic device may be provided in which the silane coupling agent comprises 3-aminopropyltriethoxysilane.

[0046] For example, a transparent orthodontic device may be provided, further comprising a second inorganic layer formed between the inorganic layer and the organic layer, wherein the second inorganic layer comprises at least one of silicon dioxide and tin oxide.

[0047] For example, a transparent orthodontic device may be provided that further comprises fluorescent nanodiamonds dispersed in the organic layer.

[0048] For example, a transparent orthodontic device may be provided in which the fluorescent nanodiamond contains a nitrogen-vacancy center.

[0049] For example, a transparent orthodontic device may be provided, which further comprises thermochromic liquid crystal microcapsules dispersed in the organic layer.

[0050] For example, a transparent orthodontic device may be provided in which the thermochromic liquid crystal microcapsule contains a cholesteric liquid crystal.

[0051] For example, a transparent orthodontic device may be provided that further comprises graphene quantum dots dispersed in the inorganic layer.

[0052] For example, a transparent orthodontic device may be provided in which the graphene quantum dots are surface-modified with oxygen-containing functional groups.

[0053] For example, a transparent orthodontic device may be provided that further comprises bioglass nanoparticles dispersed in the inorganic layer.

[0054] For example, a transparent orthodontic device may be provided in which the bioglass nanoparticles have a SiO2-CaO-P2O5 composition.

[0055] For example, a transparent orthodontic device may be provided that further comprises silver nanoparticles and a copper-chelate complex dispersed in the organic layer.

[0056] For example, a clear orthodontic device may be provided that further comprises a self-healing agent in the form of microcapsules included in the organic layer.

[0057] For example, a clear orthodontic device may be provided that further comprises chitosan-alginate hydrogel particles dispersed in the organic layer.

[0058] According to another aspect of the present invention, a method for manufacturing a clear orthodontic device may be provided, comprising the steps of: forming an inorganic layer on the surface of a clear orthodontic device body; forming an intermediate interface layer on the inorganic layer using a silane coupling agent; and forming a parylene organic layer in which functional nanoparticles are dispersed on the intermediate interface layer.

[0059] For example, a method for manufacturing a transparent orthodontic device may be provided, wherein the functional nanoparticle comprises at least one of fluorescent nanodiamonds, thermochromic liquid crystal microcapsules, silver nanoparticles, and chitosan-alginate hydrogel particles.

[0060] According to another aspect of the present invention, a method for orthodontic treatment can be provided while monitoring the progress of treatment using the transparent orthodontic device. Effects of the invention

[0061] The disclosed technology may have the following effects. However, this does not mean that a specific embodiment must include all of the following effects or only the following effects; therefore, the scope of the rights of the disclosed technology should not be understood as being limited by this.

[0062] According to the present invention, the moisture resistance of the clear orthodontic device is improved, so that stable physical properties can be maintained even during long-term use in the oral cavity.

[0063] According to the present invention, mechanical strength is improved and interlayer adhesion is enhanced through the introduction of an intermediate interface layer, thereby ensuring durability capable of withstanding repetitive mechanical stress.

[0064] According to the present invention, a high sterilization rate against major oral pathogens is achieved with a strong antibacterial effect, and continuous antibacterial performance is maintained, thereby contributing to the prevention of oral diseases and the improvement of oral hygiene.

[0065] According to the present invention, the progress of correction can be tracked in real time and the patient's wearing time can be objectively measured through a smart monitoring function, thereby allowing for accurate evaluation and optimization of treatment effects. Brief explanation of the drawing

[0067] Figure 1 is an actual photograph of a transparent orthodontic device with a multifunctional nanocomposite coating according to the present invention. FIG. 2 is a schematic diagram showing the cross-sectional structure of a transparent orthodontic device to which only an inorganic thin film coating is applied according to one embodiment of the present invention. FIG. 3 is a schematic diagram showing the cross-sectional structure of a transparent orthodontic device to which only an organic thin film coating is applied according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing a cross-section of a transparent orthodontic device of a hybrid structure in which both an inorganic thin film coating and an organic thin film coating are applied according to one embodiment of the present invention. Specific details for implementing the invention

[0068] The description of the present disclosure is merely an example for structural or functional explanation, and therefore the scope of the present disclosure should not be interpreted as being limited by the examples described in the text. That is, since the examples are subject to various modifications and may take various forms, the scope of the present disclosure should be understood to include equivalents capable of realizing the technical concept. Furthermore, the purposes or effects presented in the present disclosure do not imply that a specific example must include all of them or only such effects; therefore, the scope of the present disclosure should not be understood as being limited by them.

[0069] Meanwhile, the meaning of the terms described in this application should be understood as follows. When a component is described as being "connected" to another component, it should be understood that it may be directly connected to the other component, or that there may be other components in between. On the other hand, when a component is described as being "directly connected" to another component, it should be understood that there are no other components in between. Meanwhile, other expressions describing the relationship between components, such as "between" and "exactly between," or "adjacent to" and "directly adjacent to," should be interpreted in the same way.

[0070] A singular expression should be understood to include a plural expression unless the context clearly indicates otherwise, and terms such as "include" or "have" are intended to specify the existence of the implemented features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood not to preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0071] The clear orthodontic device of the present invention may be composed of a clear orthodontic device body and a multilayer coating structure that protects it. The clear orthodontic device body is a transparent orthodontic device manufactured using a 3D printing method with a photocurable resin, and it can perform the function of applying orthodontic force by adhering to the teeth within the oral cavity. Such a body may have a problem in that its physical properties may deteriorate due to moisture in the oral cavity, temperature changes, and repeated removal and insertion, so surface protection may be required.

[0072] The inorganic layer is a layer comprising at least one of alumina, titanium dioxide, and zirconium dioxide, and can be formed directly on the surface of the clear aligner body as shown in FIG. 2. This inorganic layer can serve as a primary barrier against moisture in the oral cavity and, in particular, can prevent moisture penetration into the clear aligner body through excellent moisture resistance. Additionally, the inorganic layer can perform the function of improving adhesion with the subsequently formed organic layer.

[0073] The organic layer is a layer containing a parylene polymer, formed on top of the inorganic layer as shown in Fig. 3, which can provide improved mechanical strength and additional moisture barrier functions. The parylene polymer can be coated with a uniform thickness even on the surface of a clear aligner with a complex three-dimensional structure, thereby ensuring consistent protective performance over the entire surface. This organic layer provides resistance to mechanical stress that may occur in the oral cavity and can prevent peeling or damage to the coating layer even during long-term use.

[0074] As shown in Fig. 4, a multilayer structure composed of an inorganic layer and an organic layer can provide significantly improved durability and protective performance compared to a single-layer coating by mutually complementing the unique characteristics of each layer. Through this configuration, durability issues such as deformation, wear, discoloration, and peeling of the clear aligner can be effectively resolved, and a clear aligner capable of long-term use in the oral cavity can be realized.

[0075] The method of forming the inorganic layer can have a decisive influence on the quality and characteristics of the coating layer. Atomic layer deposition (ALD) is a technique that forms thin films at the atomic layer level by sequentially supplying precursors and reaction gases, enabling highly precise thickness control and excellent step coverage. In particular, when forming the alumina layer, self-limiting growth utilizing only surface reactions can be achieved by alternating the supply of trimethylaluminum and water.

[0076] Sputtering is a technique for depositing a target material by physically impacting it with argon ions, and it can provide a relatively fast deposition rate and excellent adhesion. These methods can form an inorganic layer of uniform thickness even on the complex curved shapes of clear aligners, thereby ensuring consistent protective performance across the entire surface. In particular, it is possible to achieve a dense film without pinholes even at thin thicknesses in the range of 5 nm to 50 nm, thereby maximizing the moisture barrier effect.

[0077] Chemical vapor deposition of the organic layer can be a deposition technique that can maximize the unique properties of parylene polymers. This method can proceed by supplying para-xylene monomers in the gas phase and polymerizing them in real time on the surface of an object. After generating monomers by heating the dimer to 350-175°C in the sublimation step and heating to 650-690°C in the pyrolysis step, polymerization can be carried out in a deposition chamber at room temperature.

[0078] This process can be precisely controlled to a thickness ranging from 0.1 μm to 30 μm, enabling uniform coating even on the complex three-dimensional structure of clear aligners. The parylene layer formed by chemical vapor deposition can have a dense structure free of pinholes, exhibiting excellent moisture barrier properties and chemical inertness. Furthermore, since deposition is performed at room temperature, a strong mechanical protective film can be formed without causing thermal damage to the body of the clear aligner.

[0079] The selection of the parylene polymer type can be optimized based on the usage environment and performance requirements of the clear aligner. Parylene N exhibits excellent high dielectric constant and high-frequency stability, and possesses characteristics suitable for industrial applications, which can be advantageous in terms of oral safety. Parylene C is the most widely used type due to its excellent resistance to mechanical permeation and adhesion, and it can demonstrate performance specifically specialized for moisture barrier properties.

[0080] Parylene D possesses characteristics similar to Parylene C but can offer slightly different mechanical properties, while Parylene F exhibits excellent chemical stability and adhesion but can be relatively expensive. The physical properties of each of these Parylene types vary slightly depending on the functional groups of the monomers; since they can be mixed during dimmer loading, it is possible to polymerize each functional group in the desired proportions. Given that both moisture resistance and biocompatibility are critical for clear aligners, the selective application of these various Parylene types may be necessary.

[0081] The intermediate interfacial layer can be a key component that dramatically improves the adhesion between the inorganic layer and the organic layer. This layer, graft-polymerized with a silane coupling agent, can be formed with a thin thickness of 5 nm to 20 nm while still performing the function of completely preventing interlayer delamination. The silane coupling agent can be highly effective for interfacial adhesion as it simultaneously possesses siloxane groups that form chemical bonds with the inorganic surface and organic functional groups that can bond with the organic layer.

[0082] The graft polymerization process can proceed by chemically bonding silane molecules to the surface of an inorganic layer via a gas-phase silane coupling reaction, followed by the formation of polymer chains by reacting them with polymerizable monomers such as methacrylic acid. This intermediate interfacial layer can ensure thermal shock resistance by mitigating the difference in thermal expansion coefficients between the inorganic and organic layers, and guarantee long-term durability by completely blocking moisture penetration pathways. In particular, 2-5 chains / nm 2By securing a graft density of this level, interfacial adhesion can be improved by 20 times compared to existing methods.

[0083] 3-aminopropyltriethoxysilane can be a compound capable of providing particularly excellent interfacial adhesion performance among silane coupling agents. This compound can form strong siloxane bonds with hydroxyl groups on an inorganic surface through three ethoxy groups, and can chemically bond with a subsequent organic layer through amino groups. In particular, it can form a uniform monolayer through a vapor phase reaction carried out at 150°C for 2 hours.

[0084] Amino groups can react with radicals generated during the parylene polymerization process to form covalent bonds, thereby providing very strong interfacial adhesion. Furthermore, these chemical bonds can be stably maintained even in the moist environment of the oral cavity, preventing delamination even during long-term use. The use of APTES can exhibit excellent bonding characteristics, particularly on oxide surfaces such as alumina or titanium dioxide, enabling perfect adhesion between the inorganic and organic layers.

[0085] The second inorganic layer is an intermediate layer additionally formed between the inorganic layer and the organic layer, and may have a composition reflecting the sample structure presented in the initial data. Silicon dioxide can provide moisture resistance, slight strength enhancement, and antifouling properties, and can be formed to a thickness of 0.1 μm by the sputtering method. Tin oxide may exhibit a yellow color due to its low bandgap, but can impart special optical properties.

[0086] The introduction of a second inorganic layer can further enhance the moisture barrier performance of the entire coating system, and the multilayer structure allows defects in each layer to complement one another. In particular, the silicon dioxide layer possesses excellent chemical stability and transparency, enabling enhanced protection while maintaining the aesthetic characteristics of clear aligners. This multilayer inorganic structure can increase resistance to various chemical environmental changes that may occur within the oral cavity, thereby ensuring stable performance over the long term.

[0087] Fluorescent nanodiamonds can be an innovative component that provides smart monitoring capabilities to clear aligners. These nanoparticles, ranging in size from 2 nm to 10 nm, are dispersed within an organic layer at a concentration of 0.01 to 0.1 wt%, enabling real-time tracking of the progress of orthodontic treatment. Fluorescent nanodiamonds possess biocompatibility and excellent photostability, making them safe for long-term use in the oral cavity.

[0088] These nanodiamonds emit red fluorescence upon UV-LED irradiation, allowing for the visual verification of tooth movement through changes in fluorescence intensity at areas where orthodontic pressure is concentrated. Furthermore, by analyzing changes in fluorescence intensity, the patient's actual wearing time can be objectively measured, enabling accurate evaluation of treatment efficacy. This monitoring capability can significantly contribute to improved patient compliance and the optimization of treatment plans, thereby advancing conventional passive orthodontic treatment into an active and scientific approach.

[0089] Nitrogen-vacancy centers can be a key structure determining the optical properties of fluorescent nanodiamonds. In this crystal structure, a vacancy is formed when one carbon atom is replaced by a nitrogen atom and an adjacent carbon atom is removed, which can constitute a very stable fluorescent center. NV centers can emit strong red fluorescence at a wavelength of 637 nm, and this fluorescence can be maintained continuously without photobleaching.

[0090] These optical characteristics allow for easy observation through an external light source even while wearing clear aligners, enabling real-time monitoring. In particular, the fluorescence intensity of the NV center can respond sensitively to ambient pressure or deformation, allowing for accurate identification of stress distribution in areas where orthodontic force is applied. Furthermore, since these fluorescence signals can be quantitatively analyzed through a digital imaging system, objective and scientific evaluation of the progress of orthodontic treatment is possible.

[0091] Thermochromic liquid crystal microcapsules can provide a smart sensor function capable of visually detecting changes in oral temperature. These microcapsules, ranging in size from 0.5 μm to 2 μm, are dispersed within an organic layer at a concentration of 0.1 to 0.5 wt% and can exhibit a color change within an oral temperature range of 35°C to 40°C. They remain colorless at normal oral temperatures but can change to blue when there is a local temperature increase due to inflammation or infection.

[0092] These temperature-sensitive characteristics can serve as an alarm system for the early detection of oral abnormalities. In particular, patients can identify the early stages of gum inflammation or periodontal disease that may occur while wearing clear aligners, enabling them to receive treatment at the appropriate time. Furthermore, by providing a guide on the appropriate wearing temperature, it helps patients maintain proper usage, thereby maximizing treatment effectiveness and minimizing side effects.

[0093] Cholesteric liquid crystals are the core functional material for thermochromic liquid crystal microcapsules, utilizing the principle in which the reflected color changes through a variation in helical pitch according to temperature. These liquid crystals possess the characteristic of selectively reflecting light of specific wavelengths at specific temperatures, enabling highly precise temperature detection. At the normal oral temperature of 36–37°C, they appear colorless as they reflect light outside the visible spectrum, but as the temperature rises, they begin to reflect light in the blue spectrum.

[0094] This color change is reversible, allowing it to return to a colorless state when the temperature returns to normal. The temperature sensitivity of cholesteric liquid crystals is highly sensitive, capable of detecting even small temperature changes of about 1°C, which enables the early detection of subtle inflammatory responses in the oral cavity. Furthermore, since these optical changes are easily observable with the naked eye, they offer the convenience of allowing patients to monitor their oral condition without the need for separate equipment.

[0095] Graphene quantum dots can be an innovative nanomaterial dispersed in an inorganic layer that can simultaneously provide antistatic and antibacterial performance enhancements. These nanoparticles, ranging in size from 2 nm to 8 nm, are dispersed within an inorganic layer at a concentration of 0.05 to 0.2 wt% and can impart excellent electrical conductivity and photoelectric conversion properties. Graphene quantum dots can inhibit the electrostatic attachment of bacteria or foreign substances by preventing the accumulation of static electricity that may occur in the oral cavity.

[0096] In particular, when used in combination with titanium dioxide, it exhibits a synergistic effect that can enhance photocatalytic activity by more than tenfold, thereby enabling powerful antibacterial effects. The electron transfer properties of graphene quantum dots promote the generation of reactive oxygen species upon light irradiation, which can destroy bacterial cell walls and block biofilm formation. Furthermore, since electrical properties can be imparted while maintaining transparency, various functionalities can be provided without compromising the aesthetic characteristics of clear aligners.

[0097] Graphene quantum dots surface-modified with oxygen-containing functional groups can provide enhanced dispersibility and biocompatibility. Oxygen-containing functional groups, such as hydroxyl, carboxyl, and epoxy groups, impart hydrophilicity to the surface of graphene quantum dots, enabling uniform dispersion within an inorganic matrix. This surface modification can prevent nanoparticle aggregation and maximize their function as individual particles.

[0098] Furthermore, oxygen functional groups can stabilize nanoparticles by forming chemical bonds with surrounding inorganic materials, preventing them from detaching from the coating layer. This strong bonding ensures safety by preventing the graphene quantum dots from leaching out even during long-term oral use. In particular, carboxyl groups can form chelate bonds with metal ions, providing additional antimicrobial effects through complexation with antimicrobial metal ions, thereby enabling the implementation of multiple antimicrobial mechanisms.

[0099] Bioglass nanoparticles can be bioactive materials dispersed in an inorganic layer that provide tooth remineralization and oral health promotion functions. These nanoparticles, ranging in size from 20 nm to 100 nm, are dispersed within an inorganic layer at a concentration of 1 to 5 weight percent and can gradually release calcium ions and phosphate ions upon contact with saliva in the oral cavity. These ions can promote the remineralization of enamel in areas of early tooth decay, thereby aiding in natural tooth recovery.

[0100] Bioglass nanoparticles can also provide a pH buffering effect in the oral cavity, releasing alkaline ions in acidic environments to prevent tooth decay. This pH-regulating function can directly contribute to preventing cavities by neutralizing acid production by oral bacteria. Furthermore, since they can continuously release ions over a long period of more than six months, they can form a persistent protective barrier on the teeth during the wearing of clear aligners, thereby providing a preventive treatment effect alongside orthodontic treatment.

[0101] Bioglass with a SiO2-CaO-P2O5 composition, also known as a 45S5 composition, is a bioactive glass that can be a material with proven safety and efficacy in the dental field. In this composition, silica forms the basic framework of the glass network, while calcium and phosphate can provide the key ions necessary for tooth remineralization. In particular, the ratio of calcium to phosphorus is similar to the hydroxyapatite structure of tooth enamel, which can induce a natural remineralization process.

[0102] When bioglass of this composition comes into contact with saliva, silica dissolves from the surface, allowing calcium and phosphate ions to be released sequentially; this can promote the growth of new hydroxyapatite crystals on the enamel surface. Additionally, the released silica gel layer can inhibit bacterial adhesion, thereby providing both tooth protection and antibacterial effects simultaneously. This multi-functionality can prevent tooth damage that may occur while wearing clear aligners and improve overall oral health.

[0103] The combination of silver nanoparticles and copper-chelate complexes can provide a strong and sustained antimicrobial effect through mutually complementary antimicrobial mechanisms. Silver nanoparticles ranging in size from 1 nm to 10 nm can inhibit bacterial proliferation by directly penetrating the bacterial cell wall and binding to DNA, while copper-EDTA chelate complexes ranging in size from 20 nm to 100 nm can provide a sustained antimicrobial effect by slowly releasing copper ions.

[0104] This dual antimicrobial system can demonstrate a bactericidal effect of over 99.9% within 24 hours against major oral pathogens, such as Streptococcus mutans and Porphyromonas gingivalis. Silver nanoparticles provide an immediate antimicrobial effect, while the copper-chelate complex maintains a long-term antimicrobial effect, ensuring continuous oral hygiene during the wearing of clear aligners. Furthermore, these antimicrobial components are stably dispersed within the organic layer, ensuring both safety and efficacy through controlled release without rapid leaching into the oral cavity.

[0105] Self-healing agents in the form of microcapsules can provide an innovative function for automatically repairing micro-damage occurring in a coating layer. These microcapsules, ranging in size from 100 nm to 500 nm, contain a polyurethane oligomer and a curing agent; when the capsule is destroyed by external impact or abrasion, the healing agent is released to automatically fill the damaged area. This self-healing mechanism can repair more than 90% of micro-scratches within 24 hours.

[0106] The release and curing processes of the self-healing agent are optimized for oral temperature and humidity conditions, enabling an effective healing response. This feature allows the surface roughness of the clear aligner to be consistently maintained at a low level, thereby inhibiting bacterial adhesion and preserving aesthetics. Furthermore, the lifespan of the coating layer can be extended threefold from the conventional 6 months to 18 months, reducing the financial burden on patients and improving treatment continuity. Since the microcapsules are uniformly dispersed throughout the organic layer, an immediate self-healing response is possible regardless of where damage occurs.

[0107] Chitosan-alginate hydrogel particles can function as a smart drug delivery system that releases active therapeutic substances in response to changes in oral pH. These hydrogel particles, ranging in size from 50 nm to 150 nm, exhibit varying degrees of swelling within a pH range of 5.5 to 7.4 and can selectively release fluoride ions in acidic environments and antimicrobial agents in alkaline environments. This pH sensitivity can enable personalized treatment tailored to changes in the oral environment.

[0108] Fluoride ions released under acidic conditions can strengthen tooth enamel and prevent tooth decay, while antimicrobial agents released under alkaline conditions can inhibit bacterial growth and prevent gum disease. This hydrogel, combining the cationic properties of chitosan and the anionic properties of alginate, can stably encapsulate various therapeutic substances and ensure long-term safety through biodegradation by oral enzymes. Furthermore, these particles can contribute to the normalization of oral pH, thereby providing an overall improvement in oral health.

[0109] A method for manufacturing a multilayer coated clear orthodontic device may consist of a sequential process that ensures interlayer adhesion while maximizing the characteristics of each layer. In the inorganic layer formation step, at least one of alumina, titanium dioxide, and zirconium dioxide may be deposited by atomic layer deposition or sputtering to form a uniform layer with a thickness of 5 nm to 50 nm. Subsequently, in the intermediate interface layer formation step, a chemical bonding layer using a silane coupling agent may be formed.

[0110] The formation of an intermediate interface layer using a silane coupling agent can be carried out via a gas-phase reaction at 150°C for 2 hours, followed by methacrylic acid graft polymerization using a UV initiator for 5 minutes. Finally, in the step of forming a parylene organic layer dispersed with functional nanoparticles, fluorescent nanodiamonds, thermochromic liquid crystal microcapsules, silver nanoparticles, chitosan-alginate hydrogel particles, etc., can be incorporated simultaneously with para-xylene monomer gas-phase polymerization. Through this continuous process, an integrated multifunctional coating system can be realized while preserving the functionality of each layer.

[0111] Orthodontic methods performed while monitoring treatment progress can be an innovative treatment approach that advances existing passive methods into active and scientific treatment. This method allows for the quantitative real-time measurement of orthodontic force distribution and tooth movement by analyzing changes in optical signals from fluorescent nanodiamonds embedded in clear aligners. Through periodic fluorescence examinations using UV-LEDs, areas of concentrated orthodontic pressure can be visualized, and the appropriateness of the treatment plan can be evaluated.

[0112] Furthermore, by observing color changes in thermochromic liquid crystal microcapsules, inflammatory responses or abnormal temperatures within the oral cavity can be detected early, thereby preventing side effects and ensuring safe treatment. This monitoring data can be quantified through a digital imaging system, enabling objective evaluation of treatment progress and allowing for real-time modification of treatment plans as needed. Patient wearing time and compliance can also be objectively measured through changes in fluorescence intensity, allowing for accurate prediction of treatment efficacy and the provision of optimized, personalized treatment.

[0113] Example 1

[0114] The body of the clear aligner was manufactured using a 3D printing method with photocurable resin. Biomed Clear Resin was used in a DLP 3D printer to print a clear aligner tailored to the individual patient's tooth shape, after which post-curing was performed using UV light with a wavelength of 405 nm. The surface of the manufactured clear aligner body was sequentially cleaned with acetone and isopropanol, and then oxygen plasma treatment was performed for 30 seconds to activate the surface.

[0115] Tin oxide was deposited as the first inorganic layer to a thickness of 0.1 μm by sputtering. Sputtering was performed in an argon gas atmosphere under conditions of 150 W RF power and 5 mTorr pressure, while the substrate temperature was maintained at room temperature. Subsequently, silicon dioxide was deposited as the second inorganic layer to a thickness of 0.1 μm under the same sputtering conditions. The tin oxide layer exhibited a yellow color due to its low bandgap characteristics, and the silicon dioxide layer was configured to provide moisture resistance, slight strength enhancement, and antifouling properties.

[0116] Alumina was formed as the third inorganic layer to a thickness of 0.01 μm using an atomic layer deposition method. The ALD process was performed at 150°C using trimethylaluminum and water as precursors, and the target thickness was reached by repeating a cycle of TMA pulse time 0.1 seconds, purge time 10 seconds, water pulse time 0.1 seconds, and purge time 10 seconds. Titanium dioxide was deposited as the fourth inorganic layer to a thickness of 0.01 μm using the same ALD method, with titanium tetrachloride and water used as precursors.

[0117] Parylene C was formed as an organic layer with a thickness of 5 μm using chemical vapor deposition. Para-xylene dimers were sublimated at 350°C and then thermally decomposed at 650°C to produce monomers, and polymerization was carried out in a deposition chamber at room temperature. The deposition pressure was maintained at 30 mTorr, and the deposition rate was controlled to 0.5 μm per hour to form a parylene layer of uniform thickness. Parylene C exhibited excellent mechanical permeability resistance and adhesion, contributing to improved moisture resistance and mechanical strength.

[0118] The entire multilayer structure is completed by stacking inorganic layers in the order of tin oxide, silicon dioxide, alumina, and titanium dioxide on the body of a clear aligner, and forming an organic layer of parylene C on the outermost layer. Each layer performs a unique function of moisture resistance, antifouling properties, and improved mechanical strength, and is designed to provide enhanced protective performance compared to a single layer through the multilayer structure.

[0119] Example 2

[0120] A clear aligner body was manufactured using the same method as in Example 1 and surface treatment was performed. An alumina inorganic layer was formed to a thickness of 30 nm using an atomic layer deposition method, and graphene quantum dots and bioglass nanoparticles were introduced together. Graphene quantum dots surface-modified with oxygen-containing functional groups were used and dispersed within an alumina matrix at an average size of 5 nm and a concentration of 0.1 wt%. Hydroxyl, carboxyl, and epoxy groups were introduced to the surface of the graphene quantum dots to improve hydrophilicity and dispersibility.

[0121] Bioglass nanoparticles were prepared as 45S5 type with a SiO2-CaO-P2O5 composition and dispersed in an alumina layer at an average size of 50 nm and a concentration of 3 wt%. Bioglass was synthesized by the sol-gel method using tetraethyl orthosilicate, calcium nitrate, and triethyl phosphate as starting materials, mixed at the target composition ratio, and sintered at 500°C. The sintered bioglass was ground to a nanoscale using ball milling and then surface modified to improve compatibility with the alumina matrix.

[0122] 3-aminopropyltriethoxysilane was used as a silane coupling agent to form an intermediate interface layer. A solution of APTES dissolved in toluene at a concentration of 1 wt% was prepared, and a silane layer was formed by reacting the substrate with the inorganic layer in the vapor phase at 150°C for 2 hours. Subsequently, graft polymerization was carried out for 5 minutes under UV irradiation using a methacrylic acid monomer and an azobis-isobutyronitrile initiator. The UV lamp was set at a wavelength of 365 nm and 10 mW / cm². 2 It was investigated by intensity, and the graft density was 3 chains / nm 2 Adjusted to the level.

[0123] Parylene C was formed as an organic layer with a thickness of 3 μm using chemical vapor deposition. Monomer formation was optimized by controlling the sublimation temperature of the para-xylene dimer to 170°C and the thermal decomposition temperature to 680°C, and the pressure of the deposition chamber was maintained at 25 mTorr. The amino groups of the intermediate interface layer were made to react with radicals generated during the parylene polymerization process to form covalent bonds.

[0124] The completed hybrid structure consists of an alumina inorganic layer dispersed with functional nanoparticles, an APTES silane graft interfacial layer, and a parylene C organic layer sequentially stacked on a clear aligner body. Graphene quantum dots were designed to provide antistatic and photocatalytic activity enhancement functions, bioglass to facilitate tooth remineralization, and the interfacial layer to strengthen interlayer adhesion.

[0125] Example 3

[0126] A clear aligner body was manufactured in the same manner as in Example 1 and subjected to surface activation treatment. An alumina layer was formed to a thickness of 25 nm using an atomic layer deposition method, and the deposition was performed at 150°C using trimethylaluminum and water as precursors. The ALD process utilized self-limiting growth characteristics to form an alumina layer of uniform thickness even on the surface of a clear aligner with a complex three-dimensional shape.

[0127] Fluorescent nanodiamonds were prepared containing nitrogen-vacancy centers. NV centers were formed by nitrogen ion implantation and annealing treatment on nanodiamonds prepared by a high-temperature, high-pressure synthesis method, and the average size was controlled to 5 nm. After acid-treating the nanodiamond surface to introduce carboxyl groups, the nanodiamonds were prepared as an aqueous dispersion. The fluorescent nanodiamonds emit strong red fluorescence at a wavelength of 637 nm and were designed to maintain stable fluorescence properties without photobleaching.

[0128] Thermochromic liquid crystal microcapsules were fabricated with a structure consisting of a cholesteric liquid crystal as the core and polymethyl methacrylate as the shell. The cholesteric liquid crystal was designed to exhibit a color change within a temperature range of 35°C to 40°C by controlling the concentration of the chiral dopant. Microencapsulation was performed using interfacial polymerization, and the microcapsules were fabricated with an average size of 1.2 μm and a shell thickness of 50 nm. They were designed to maintain a colorless state at normal oral temperatures and change to blue as the temperature rises.

[0129] Parylene N was used via chemical vapor deposition to form the organic layer. Para-xylene dimers were sublimated at 175°C and then thermally decomposed at 690°C to produce monomers, which were then subjected to room-temperature polymerization in a deposition chamber. Fluorescent nanodiamonds were dispersed at a concentration of 0.05 wt% and thermochromic liquid crystal microcapsules at a concentration of 0.3 wt% during the parylene polymerization process. To ensure uniform dispersion of the functional nanoparticles, a rotating mechanism was installed inside the deposition chamber to rotate the substrate while performing the deposition.

[0130] By controlling the temperature gradient, nanoparticles were uniformly distributed within the parylene matrix, and the final organic layer thickness was formed to 7 μm. Fluorescent nanodiamonds exhibited changes in fluorescence intensity according to correction pressure upon UV-LED irradiation, enabling monitoring of correction progress, while thermochromic liquid crystal microcapsules allowed for the visual detection of oral inflammation or abnormal temperatures.

[0131] The completed smart monitoring system is designed to provide real-time monitoring and early warning functions during orthodontic treatment, consisting of an alumina inorganic layer and a parylene N organic layer with dispersed functional nanoparticles on the body of the clear aligner.

[0132] Example 4

[0133] The body of the clear orthodontic device was manufactured in the same manner as in Example 1, and the surface was activated by treating it with oxygen plasma for 30 seconds. Titanium dioxide was formed as an inorganic layer to a thickness of 20 nm using atomic layer deposition, and was deposited at 200°C using titanium tetrachloride and water as precursors. The titanium dioxide layer was designed to serve as a base layer for a synergistic effect with the subsequently added antimicrobial nanoparticles.

[0134] Silver nanoparticles were prepared by the citrate reduction method and controlled to an average size of 3 nm. Sodium citrate was added as a reducing agent to a silver nitrate solution and reacted at 100°C, after which the surface was stabilized with polyvinylpyrrolidone. The copper-chelate complex was prepared by reacting copper acetate and EDTA in a molar ratio of 1:1 and formed into nanoparticles with an average size of 80 nm. The copper-chelate complex was designed to provide a sustained antibacterial effect by slowly releasing copper ions.

[0135] Self-healing microcapsules were manufactured with a structure consisting of a polyurethane oligomer and an isocyanate curing agent as a core and a urea-formaldehyde resin as a shell. They were encapsulated using interfacial polymerization to achieve an average size of 300 nm and a shell thickness of 20 nm, with the core material content controlled to 85% of the total capsule weight. The microcapsules were designed to automatically fill damaged areas by releasing a healing agent when destroyed by external impact or abrasion.

[0136] Parylene C was used as the organic layer via chemical vapor deposition, and antimicrobial nanoparticles and self-healing microcapsules were simultaneously dispersed during the deposition process. Silver nanoparticles were added at a concentration of 0.5 wt%, copper-chelate complex at 0.8 wt%, and self-healing microcapsules at 2.0 wt%. Para-xylene dimers were sublimated at 175°C and then thermally decomposed at 670°C to produce monomers, and room-temperature polymerization was carried out in a deposition chamber.

[0137] Ultrasonic dispersion treatment was performed in advance to ensure uniform dispersion of functional particles, and the substrate temperature was maintained at 25°C during the deposition process to prevent particle aggregation. The final thickness of the organic layer was formed to 6 μm, and the deposition rate was controlled to 0.3 μm per hour to ensure that the functional particles were evenly distributed throughout the layer.

[0138] In the completed multifunctional system, silver nanoparticles provide an immediate antibacterial effect, copper-chelate complexes provide a long-term, sustained antibacterial effect, and self-healing microcapsules are designed to automatically repair micro-damage to the coating layer. Through these multiple functionalities, the system is configured to simultaneously enhance the antibacterial properties and durability of the clear aligner.

[0139] Example 5

[0140] A clear aligner body was manufactured using the same method as in Example 1 and subjected to surface activation treatment. Zirconium dioxide was formed as an inorganic layer to a thickness of 25 nm using atomic layer deposition, and was deposited at 180°C using zirconium tetrachloride and water as precursors. Zirconium dioxide provided high chemical stability and biocompatibility, enabling it to serve as a stable base layer for the pH-responsive system.

[0141] Chitosan-alginate hydrogel particles were prepared by the ionic gelation method. Chitosan with a molecular weight of 100,000 Da and a degree of deacetylation of 85% was used and dissolved in a 1% acetic acid solution at a concentration of 2 wt%. Sodium alginate with a molecular weight of 200,000 Da was used and dissolved in distilled water at a concentration of 1.5 wt%. The chitosan solution and the alginate solution were mixed in a 1:1 volume ratio and then gelled by dropping them into a calcium chloride solution.

[0142] The formed hydrogel was ground using a homogenizer to produce nanoparticles with an average size of 100 nm, and moisture was removed through freeze-drying. To control pH reactivity, the ratio of the amino groups of chitosan and the carboxyl groups of alginate was optimized, and the structure was designed so that the degree of swelling changes within the pH range of 5.5 to 7.4. The hydrogel particles were loaded with drugs to release fluoride ions in an acidic environment and chlorhexidine antimicrobial agents in an alkaline environment.

[0143] Fluoride ions were loaded onto the hydrogel matrix in the form of sodium fluoride at a concentration of 0.1 wt%, and chlorhexidine was loaded in the form of chlorhexidine gluconate at a concentration of 0.05 wt%. Drug loading was performed by immersing the hydrogel in a swelling equilibrium state into each drug solution and introducing the drug into the body by diffusion.

[0144] Parylene N was used as the organic layer via chemical vapor deposition, and drug-loaded chitosan-alginate hydrogel particles were dispersed at a concentration of 1.5 wt%. Para-xylene dimers were sublimated at 175°C and then thermally decomposed at 690°C to produce monomers, and room-temperature polymerization was carried out in a deposition chamber. To improve the dispersibility of the hydrogel particles, the surface was pretreated with a silane coupling agent.

[0145] During the deposition process, the substrate was rotated at a low speed to ensure that the hydrogel particles were uniformly distributed throughout the organic layer, and the final organic layer thickness was formed to be 8 μm. The deposition rate was controlled to 0.4 μm per hour to ensure that the hydrogel particles were stably fixed within the matrix without damage.

[0146] The completed pH-responsive therapeutic system is designed to simultaneously provide cavity prevention and gum disease prevention functions by selectively releasing appropriate therapeutic substances in response to changes in oral pH. The hydrogel particles are biodegradable by oral enzymes to ensure long-term safety and are configured to contribute to the normalization of oral pH.

[0147] Example 6

[0148] After manufacturing the body of the clear aligner using 3D printing with a photocurable resin, the surface was cleaned in the order of acetone, isopropanol, and distilled water. Subsequently, oxygen plasma treatment was performed for 30 seconds to increase surface energy and improve adhesion with the subsequent coating layer. The plasma treatment conditions were set to an RF power of 100W, an oxygen flow rate of 50 sccm, and a pressure of 100 mTorr.

[0149] Graphene quantum dots and bioglass nanoparticles were simultaneously introduced while forming an inorganic layer of alumina to a thickness of 30 nm using atomic layer deposition. Graphene quantum dots surface-modified with oxygen-containing functional groups were used and dispersed at an average size of 6 nm and a concentration of 0.15 wt%. Bioglass nanoparticles were prepared with a composition of SiO2 45%, CaO 24.5%, P2O 56%, and Na2O 24.5% and dispersed at an average size of 60 nm and a concentration of 2.5 wt%.

[0150] 3-aminopropyltriethoxysilane was introduced via vapor deposition to form an intermediate interface layer. APTES was vaporized at 150°C and chemically bonded to the alumina surface, after which UV graft polymerization was performed using methacrylic acid and azobisisobutyronitrile. UV irradiation was applied at 15 mW / cm² at a wavelength of 365 nm. 2 The process was performed at a high intensity for 5 minutes, and the graft density was 4 chains / nm 2 It was adjusted.

[0151] All functional nanoparticles were integrally dispersed while forming parylene C as an organic layer by chemical vapor deposition. Fluorescent nanodiamonds (NV center, average size 4 nm) were added at a concentration of 0.08 wt%, thermochromic liquid crystal microcapsules (cholesteric liquid crystal, average size 1 μm) at 0.25 wt%, silver nanoparticles (average size 2 nm) at 0.3 wt%, copper-chelate complexes (average size 70 nm) at 0.6 wt%, self-healing microcapsules (polyurethane oligomer, average size 250 nm) at 1.8 wt%, and chitosan-alginate hydrogel particles (drug carriers, average size 90 nm) at 1.2 wt%.

[0152] Surface modification was performed to ensure the commercial viability of the functional nanoparticles, and the dispersion was homogenized by ultrasonic treatment and then introduced stepwise during the parylene polymerization process. Para-xylene dimers were sublimated at 175°C and thermally decomposed at 675°C to produce monomers, and room-temperature polymerization was carried out in a deposition chamber. The deposition pressure was maintained at 28 mTorr, and the substrate was rotated at 5 revolutions per minute to ensure uniform dispersion.

[0153] By controlling the temperature gradient, each functional particle was positioned at an optimal location, and the final organic layer thickness was formed to be 9 μm. The deposition rate was low at 0.2 μm per hour for the first hour to strengthen adhesion with the interface layer, and then the deposition rate was increased to 0.5 μm per hour to improve efficiency.

[0154] Real-time monitoring was performed to control quality at each stage of the entire manufacturing process. During the deposition of the inorganic layer, the thickness was measured in real time using a quartz crystal microbalance, and during the formation of the organic layer, thickness uniformity was verified using a laser interferometer. The dispersion state of the functional nanoparticles was confirmed using a transmission electron microscope, and it was confirmed that the particles were uniformly distributed without aggregation.

[0155] The completed integrated multifunctional system consists of a structure in which an inorganic alumina layer dispersed with functional nanoparticles, an APTES silane graft interfacial layer, and a parylene C organic layer integrating all functional nanoparticles are sequentially laminated on a clear aligner body. Through this integrated structure, a multifunctional clear aligner was completed that incorporates moisture resistance, mechanical strength, antibacterial properties, self-healing capabilities, pH responsiveness, and smart monitoring functions. The system was designed to optimize the interactions between the functional components to achieve a synergistic effect greater than the sum of their individual functions.

[0156] Experimental Example 1

[0157] Moisture resistance, mechanical strength, and interfacial adhesion were evaluated for the clear aligners prepared in Examples 1 and 2. Moisture resistance was assessed by measuring water vapor permeability according to the ASTM E96 standard, and measurements were taken for 7 days under conditions of 38°C and 90% relative humidity. The multilayer inorganic structure of Example 1 was 0.08 g / m² 2 It exhibited a water vapor transmittance of ⅓day, which is 2.4 g / m² for the uncoated clear aligner body. 2 · It showed a 30-fold improvement in moisture barrier performance compared to day. In particular, in a structure with an additional second inorganic layer of tin oxide and silicon dioxide, defects in each layer complemented each other, confirming a 5-fold improvement in barrier performance compared to a single inorganic layer.

[0158] Mechanical strength was measured using a tensile testing machine, and specimens were prepared and evaluated according to the ASTM D638 standard. In the case of Example 1, a tensile strength of 45 MPa, an elongation of 180%, and a Young's modulus of 1.2 GPa were observed, representing a 60% and 50% improvement, respectively, compared to the tensile strength of 28 MPa and an elongation of 120% of the uncoated body. It was confirmed that the parylene C organic layer effectively disperses mechanical stress, thereby improving the overall mechanical properties.

[0159] Interfacial adhesion strength was measured using the pull-off test method, and the structure including the APTES silane graft intermediate interfacial layer of Example 2 exhibited an adhesion strength of 12.5 MPa. This value represents an improvement of more than 20 times compared to the 0.6 MPa of Example 1, which lacked an intermediate interfacial layer, and was analyzed as a result of the combined action of chemical bonding by the silane coupling agent and physical entanglement effects caused by graft polymerization. The graft density was 3-4 chains / nm 2 It exhibited optimal adhesion within the specified range, and showed a tendency for adhesion to decrease at densities higher or lower than this.

[0160] As a result of re-measuring the adhesive strength after repeatedly exposing the clear aligner to temperatures between 4°C and 60°C 1,000 times for a thermal shock test, Example 2 maintained more than 95% of its initial adhesive strength, while Example 1 decreased to 60% of its initial adhesive strength. This demonstrated that the intermediate interface layer effectively relieves interfacial stress caused by differences in the coefficient of thermal expansion.

[0161] To evaluate long-term durability, an immersion test was conducted for 6 months in artificial saliva at 37°C and pH 6.8. In Example 1, minor delamination was observed in less than 5% of the coating layer after 6 months, but the overall protective function was maintained. In Example 2, no delamination or damage was observed under the same conditions, confirming excellent long-term stability. The moisture permeability also showed only a change of less than 10% compared to the initial state, confirming that the structural stability of the coating layer was maintained.

[0162] Experimental Example 2

[0163] The functional performance of the fluorescent nanodiamonds and thermochromic liquid crystal microcapsules of the smart monitoring system prepared in Example 3 was evaluated. The optical properties of the fluorescent nanodiamonds were measured using a confocal fluorescence microscope, and the fluorescence intensity at 637 nm was measured after excitement with a 532 nm laser. The fluorescence intensity was 10,000 counts under no load, and decreased by 15% to 8,500 counts under a compressive stress of 1 MPa. At 2 MPa, it decreased by 28% to 7,200 counts, confirming that the change in fluorescence intensity according to pressure was linear.

[0164] To simulate orthodontic force, loads of 0.5N, 1.0N, and 1.5N were applied to the clear aligner, and changes in the fluorescence signal were measured. As a result, a localized decrease in fluorescence intensity was observed in areas where the load was concentrated. By analyzing the image of these changes in fluorescence intensity distribution, the stress concentration sites could be accurately identified, showing an agreement rate of over 90% with existing finite element analysis results. The fluorescence signal remained stable without photobleaching even during continuous 24-hour measurement, confirming its suitability for long-term monitoring.

[0165] The temperature sensitivity of the thermochromic liquid crystal microcapsules was evaluated using a precision temperature control stage. It remained colorless up to 35°C, began to change to a light blue at 36°C, and displayed a vivid blue at 38°C. The response time to temperature change was 15 seconds for heating and 25 seconds for cooling, showing very fast responsiveness. To confirm the reversibility of the color change, 1,000 repeated tests were conducted between 35°C and 40°C, and the color change characteristics remained the same as the initial state.

[0166] In an experiment simulating a clinical environment in which the temperature was raised from a base temperature of 37°C to 39°C through local heating, a selective blue change appeared only in the heated area, confirming the local inflammation detection function. The temperature detection accuracy was ±0.5°C, demonstrating sufficient precision for detecting abnormal temperatures within the oral cavity. Observation of the reflection color change mechanism according to changes in the helical pitch of cholesteric liquid crystals using a polarizing microscope revealed that as the temperature increased, the pitch decreased and the reflection wavelength shifted from red to blue.

[0167] A simulation of wearing clear aligners was conducted to evaluate the patient compliance monitoring function. As a result of measuring changes in the fluorescent nanodiamond signal at one-hour intervals for 24 hours, a phenomenon was observed where a constant fluorescence intensity pattern was maintained during wear, and the signal immediately recovered upon removal. Through the analysis of this signal pattern, the daily wearing time could be calculated with an accuracy of over 95%. Furthermore, by confirming that the appropriateness of wearing pressure could also be evaluated through the fluorescence intensity distribution, it was proven that objective monitoring of orthodontic progress is possible.

[0168] Experimental Example 3

[0169] The biofunctionality of the multifunctional antimicrobial and self-healing system and the pH-responsive therapeutic system prepared in Examples 4 and 5 was evaluated. Antimicrobial performance was tested against Streptococcus mutans and Porphyromonas gingivalis, major oral pathogens, according to the ASTM E2149 standard. After exposing specimens containing the silver nanoparticles and copper-chelate complex of Example 4 to a bacterial suspension and measuring the viable cell count, a bactericidal rate of 99.95% was observed against S. mutans and 99.92% against P. gingivalis after 24 hours.

[0170] To evaluate the persistence of antibacterial activity, antibacterial effects were measured after 7, 30, and 90 days. As a result, bactericidal rates of 99.8% against S. mutans and 99.7% against P. gingivalis were maintained even after 7 days. After 30 days, the rates decreased slightly to 98.5% and 98.2%, respectively, but still showed a high antibacterial effect. Furthermore, a bactericidal rate of over 95% was maintained even after 90 days, confirming a long-term, sustained antibacterial effect. It was analyzed that the immediate bactericidal effect of silver nanoparticles and the sustained ion release effect of the copper-chelate complex acted complementarily to exhibit excellent antibacterial performance.

[0171] The self-healing effect was evaluated by artificially creating micro-scratches and assessing the degree of repair. Scratches with a width of 2 μm and a depth of 0.5 μm were formed using an AFM tip, and the healing process was observed under conditions of 37°C and 100% relative humidity. After 24 hours, more than 90% of the scratches were repaired, and after 48 hours, more than 95% were repaired, confirming nearly complete self-healing. SEM observation confirmed the mechanism in which polyurethane oligomers released upon the destruction of microcapsules react with moisture in the air to harden and fill the damaged area.

[0172] pH-responsive drug release characteristics were evaluated under different pH conditions. Under acidic conditions of pH 5.5, the chitosan-alginate hydrogel particles swelled and released fluoride ions, with 85% of the loaded fluoride released after 24 hours. Under alkaline conditions of pH 7.4, chlorhexidine was selectively released, with 80% of the loaded amount released after 24 hours. Through these pH-sensitive release characteristics, it was confirmed that personalized treatment based on changes in the oral environment is possible.

[0173] Biocompatibility evaluation was conducted by performing cytotoxicity tests according to ISO 10993-5 standards and irritation and sensitization tests according to ISO 10993-10 standards. In the cytotoxicity test, cell viability was measured using the MTT assay with L929 mouse fibroblasts; as a result, cell viability of 85% or higher was observed in all examples, and the results were determined to be Grade 0 non-toxic. In the irritation test, the degree of erythema and edema was evaluated after applying the patch to rabbit skin for 24 hours, and it was confirmed to be non-irritating with an irritation index of less than 0.5.

[0174] Sensitization testing was conducted using the LLNA method with guinea pigs, and the sensitization index was found to be less than 1.0, indicating non-sensitization. Additionally, no significant irritation was observed in a test using a hamster cheek pouch model to evaluate oral mucosal irritation, confirming its safety for oral use. Analysis showed that the excellent biocompatibility of parylene and alumina was maintained despite the addition of functional nanoparticles.

[0175] Experimental Example 4

[0176] The comprehensive performance of the integrated multifunctional system of Example 6 and existing coating technology was evaluated for comparison. An uncoated clear aligner, a single parylene coating, and a single alumina coating were selected as comparison subjects, and a multi-faceted performance analysis was conducted. In the durability evaluation, no damage or peeling of the coating layer was observed in Example 6 during the 6-month durability test, and over 95% of the coating integrity was maintained during the 18-month extension test, confirming a lifespan extension effect of more than three times compared to existing coatings. The surface roughness of the uncoated clear aligner began to increase after 2 weeks, and severe wear was observed after 6 weeks.

[0177] In terms of functionality, Example 6 demonstrated more than 10 times the multifunctionality compared to a single-function coating by implementing antibacterial effect, self-healing ability, pH responsiveness, and smart monitoring function. In particular, the synergistic effect of graphene quantum dots and titanium dioxide improved photocatalytic activity by 12 times compared to single titanium dioxide, thereby achieving a powerful antibacterial effect. The interaction between the ion release of bioglass nanoparticles and the drug release of the pH-responsive hydrogel improved the oral environment by 150% compared to individual application.

[0178] To evaluate performance in an actual oral environment, an artificial saliva circulation system was established and a continuous test was conducted for 6 months. The artificial saliva was maintained at pH 6.8 and 37°C, and S. mutans, S. sanguis, and A. actinomycetemcomitans were cultured in a mixture to mimic the oral bacterial flora. Example 6 maintained 92% of its initial antibacterial performance even after 6 months, and the surface roughness remained at Ra 0.15 μm or less, effectively inhibiting bacterial adhesion. In contrast, the uncoated specimen showed an increase in Ra to 0.8 μm after 1 month, promoting biofilm formation.

[0179] To evaluate the tooth remineralization effect, an artificial caries model was constructed and tested. When Example 6 was applied to enamel specimens whose surface hardness had decreased by 30% after exposure to a caries-inducing solution, the surface hardness recovered to 85% of the initial value after 4 weeks. XRD analysis confirmed that calcium and phosphate ions released from bioglass nanoparticles promoted the recrystallization of hydroxyapatite on the enamel surface. The untreated control group showed a hardness recovery of less than 10% even after the same period.

[0180] To evaluate clinical applicability, comfort and functionality were assessed in an actual patient oral model. The clear aligner coated with Example 6 exhibited significantly reduced foreign body sensation upon wear due to its excellent surface smoothness, and the distribution of corrective force could be verified in real time through the monitoring function of fluorescent nanodiamonds. The temperature sensing function of the thermochromic liquid crystal detected areas of gum inflammation early, providing an appropriate timing for treatment.

[0181] In the economic analysis, although the manufacturing cost of Example 6 increased by 15% compared to existing clear aligners, the total treatment cost was calculated to be reduced by 40% due to a three-fold extended lifespan and the elimination of additional oral care products. Furthermore, high clinical value was confirmed as the treatment period is expected to be shortened by an average of 20% due to improved treatment efficiency through the monitoring function. In the patient satisfaction survey, it received superior evaluations compared to existing products in all categories of convenience, effectiveness, and safety, proving its potential for commercialization.

Claims

Claim 1 A nanocomposite coating comprising: a substrate; an inorganic layer formed on the surface of the substrate, comprising at least one of alumina (Al2O3), titanium dioxide (TiO2), and zirconium dioxide (ZrO2); and an organic layer formed on the inorganic layer, comprising a parylene polymer; wherein the organic layer further comprises thermochromic liquid crystal microcapsules and chitosan-alginate hydrogel particles dispersed in the organic layer, and the thermochromic liquid crystal microcapsules contain cholesteric liquid crystals; wherein the inorganic layer further comprises graphene quantum dots dispersed on the inorganic layer, and the graphene quantum dots are surface modified with oxygen-containing functional groups; and wherein the inorganic layer further comprises bioglass nanoparticles dispersed on the inorganic layer, and the bioglass nanoparticles have a SiO2-CaO-P2O5 composition. Claim 2 In claim 1, the inorganic layer is a nanocomposite coating formed by an atomic layer deposition (ALD) or sputtering method. Claim 3 In claim 1, the organic layer is a nanocomposite coating formed by a chemical vapor deposition (CVD) method. Claim 4 In claim 1, the above-mentioned parylene polymer is a nanocomposite coating comprising at least one of parylene N, parylene C, parylene D, and parylene F. Claim 5 A nanocomposite coating according to claim 1, further comprising a second inorganic layer formed between the inorganic layer and the organic layer, wherein the second inorganic layer comprises at least one of silicon dioxide (SiO2) and tin oxide (SnO2). Claim 6 A nanocomposite coating according to claim 1, further comprising antibacterial nanoparticles dispersed in the organic layer. Claim 7 In claim 6, the antimicrobial nanoparticles are a nanocomposite coating comprising at least one of silver nanoparticles and a copper-containing compound. Claim 8 delete Claim 9 delete

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