KR102830653B1 - Nano-silica reinforced shape-restoring photocurable polymeric composition for direct 3d printing and high-durability orthodontic appliances manufactured using them - Google Patents

Abstract

The present disclosure relates to a nano-silica-reinforced shape-restoring photocurable polymer composition and a highly durable orthodontic device manufactured using the same, and more specifically, to a nano-silica-reinforced shape-restoring photocurable polymer composition having rigidity, stiffness, and impact resistance suitable for orthodontic treatment in a first temperature range, having circular restoration characteristics in a second temperature range different from the first temperature range, and maintaining a solid crystalline structure even at a high-temperature sterilization temperature, and a highly durable orthodontic device manufactured using the same.

Description

{NANO-SILICA REINFORCED SHAPE-RESTORING PHOTOCURABLE POLYMERIC COMPOSITION FOR DIRECT 3D PRINTING AND HIGH-DURABILITY ORTHODONTIC APPLIANCES MANUFACTURED USING THEM}

The present disclosure relates to a nano-silica-reinforced shape-restoring photocurable polymer composition and a highly durable orthodontic device manufactured using the same, and more specifically, to a nano-silica-reinforced shape-restoring photocurable polymer composition having rigidity, stiffness, and impact resistance suitable for orthodontic treatment in a first temperature range, having circular restoration characteristics in a second temperature range different from the first temperature range, and maintaining a solid crystalline structure even at a high-temperature sterilization temperature, and a highly durable orthodontic device manufactured using the same.

Elasticity refers to the property of an object to change shape when force is applied to it and then return to its original state when the force is removed, and general orthodontic devices use this elasticity to perform their orthodontic function. That is, orthodontic devices are designed with set-up in mind, and can be smoothly installed on teeth before orthodontic treatment based on elasticity, and after installation, they can move, rotate, extrude, and/or embed teeth to be orthodontized based on elasticity.

However, when a typical orthodontic appliance is installed in the oral cavity, its shape may be deformed due to the resistance of the teeth to be corrected. Due to such deformation of the orthodontic appliance, the planned goal of movement, rotation, extrusion, and/or intrusion of the teeth to be corrected cannot be achieved through the installation of the orthodontic appliance, and in order to achieve the initial treatment goal, there is the inconvenience of having to remove the deformed orthodontic appliance and fabricate and install a new orthodontic appliance.

Recently, photocurable compositions using shape memory polymers have been developed and applied to orthodontic devices. These compositions are characterized by having rigidity, stiffness, and elasticity suitable for orthodontic treatment within a specific temperature range, while having circular restoration characteristics within a specific temperature range different from the specific temperature range. However, these existing photocurable compositions have limitations in that they have low wear resistance when used for a long period of time, and are particularly vulnerable to impact, so that breakage or permanent deformation may occur in environments where high-intensity chewing pressure is applied.

In addition, in the case of existing photocurable shape-restoring polymer compositions, the shrinkage rate is large during photocuring, and internal stress is generated, which may affect the precision and fit of the orthodontic device. This problem is especially more prominent when manufacturing orthodontic devices with complex structures. In addition, existing compositions have low curing efficiency in the visible light range, so the curing time is long, and complete curing of thick parts is difficult, which may cause unevenness in physical properties.

Against this backdrop, there is a need to develop an improved photocurable shape-restoring polymer composition that can improve mechanical properties through nano-level reinforcement, enhance surface characteristics, increase photocuring efficiency, and maintain color stability and durability even after long-term use.

Korean Patent Registration No. 10-1943800 Korean Publication Patent No. 10-2020-0079479 Korean Patent Registration No. 10-1585981 Korean Patent Registration No. 10-2416141

The problem to be solved by the present disclosure is to provide a shape-restoring photocurable polymer composition having improved mechanical properties using nano silica and a highly durable orthodontic device using the same.

Another problem to be solved by the present disclosure is to provide a photocurable polymer composition having greatly improved impact resistance including a core-shell structure acrylic impact modifier, and an orthodontic device using the same.

Another problem that the present disclosure seeks to solve is to provide a photocurable polymer composition having a reduced surface friction coefficient including a fluorinated methacrylate copolymer and an orthodontic device using the same.

Another problem that the present disclosure seeks to solve is to provide a photocurable polymer composition that includes a benzotriazole derivative photostabilizer to prevent discoloration due to ultraviolet rays and maintain color stability for a long period of time, and an orthodontic device using the same.

Another problem that the present disclosure seeks to solve is to provide a photocurable polymer composition having increased curing efficiency in the visible light range through an improved photoinitiator system and an orthodontic device using the same.

Another problem that the present disclosure seeks to solve is to provide a photocurable polymer composition that maintains crystallinity even at high temperatures of 150°C or higher and is capable of high-temperature sterilization and disinfection, and an orthodontic device using the same.

The problems to be solved by the present disclosure are not limited to the problems mentioned above, and problems to be solved by the present disclosure that are not mentioned will be clearly understood by a person having ordinary knowledge in the technical field to which the present disclosure belongs (“ordinary skilled in the art”) from the description below.

According to one embodiment of the present disclosure, a photocurable shape restoring polymeric composition comprising a photocurable compound, a photoinitiator, nano silica particles, a core-shell structured acrylic impact modifier, a fluorinated methacrylate copolymer, and a benzotriazole derivative photostabilizer, wherein the photocurable compound comprises at least one selected from aliphatic urethane dimethacrylate, caprolactone urethane triacrylate, bisphenol A ethoxylate dimethacrylate, tricyclodecane dimethacrylate, and polyethylene glycol diacrylate, the photoinitiator comprises at least one selected from lucirin TPO-L, phenylglyoxylate methyl ester, and ethyl 4-(dimethylamino)benzoate, and the nano silica particles are particles having a size of 5-50 nm, the surface of which is functionalized with methacrylate.

For example, a photocurable shape-restoring polymer composition can be provided, wherein the photocurable compound contains 40 to 70 parts by weight of an aliphatic urethane dimethacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.

For example, a photocurable shape-restoring polymer composition can be provided, wherein the photocurable compound includes 1 to 25 parts by weight of caprolactone urethane triacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided, wherein the photocurable compound contains 5 to 25 parts by weight of tricyclodecane dimethacrylate based on 100 parts by weight of the total photocurable shape restoring polymer composition.

For example, a photocurable shape-restoring polymer composition can be provided, wherein the photocurable compound contains 2 to 15 parts by weight of polyethylene glycol diacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided, wherein the photoinitiator comprises 2 to 10 parts by weight of Lucilin TPO-L based on 100 parts by weight of the total photocurable shape restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided in which the photoinitiator comprises 1 to 5 parts by weight of ethyl 4-(dimethylamino)benzoate based on 100 parts by weight of the total photocurable shape restoring polymer composition.

For example, a photocurable shape-restoring polymer composition can be provided in which the nano silica particles are included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total photocurable shape-restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided in which the core-shell structure acrylic impact modifier is included in an amount of 3 to 12 parts by weight based on 100 parts by weight of the total photocurable shape restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided in which the fluorinated methacrylate copolymer is included in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the total photocurable shape restoring polymer composition.

For example, a photocurable shape restoring polymer composition can be provided in which the benzotriazole derivative photostabilizer is included in an amount of 0.2 to 2 parts by weight based on 100 parts by weight of the total photocurable shape restoring polymer composition.

As an example, a photocurable shape restoring polymer composition can be provided, wherein the photocurable shape restoring polymer composition further comprises at least one selected from a dithiol compound and a polyphenyl ether.

For example, a photocurable shape-restoring polymer composition can be provided that has a glass transition temperature of 45 to 120°C after curing.

For example, a photocurable shape-restoring polymer composition can be provided that has a characteristic of maintaining crystallinity even at a temperature of 150°C or higher after curing.

According to another embodiment of the present invention, an orthodontic device manufactured using a photocurable shape-restoring polymer composition can be provided.

For example, an orthodontic appliance may be provided that serves as an implant guide or surgical template.

According to the present disclosure, a photocurable shape-restoring polymer composition having improved mechanical properties including methacrylate-functionalized nano silica particles and an orthodontic device using the same can be provided. In particular, by introducing nano silica, wear resistance can be improved by 30% or more and flexural strength can be improved by 25% or more.

In addition, according to the present disclosure, a photocurable polymer composition including a core-shell structure acrylic impact modifier having an improved impact strength of 75% or more and an orthodontic device using the same can be provided. As a result, the risk of breakage can be significantly reduced even in an environment with high chewing pressure.

In addition, according to the present disclosure, a photocurable polymer composition including a fluorinated methacrylate copolymer having a surface friction coefficient reduced by 40% or more and an orthodontic device using the same can be provided. As a result, an effect of making it easier to attach and detach the orthodontic device can be obtained.

In addition, according to the present disclosure, a photocurable polymer composition including a benzotriazole derivative photostabilizer and maintaining color stability for 6 months or longer and an orthodontic device using the same can be provided. As a result, an effect of maintaining aesthetic characteristics even when used for a long period of time can be obtained.

In addition, according to the present disclosure, a photocurable polymer composition having improved curing efficiency in the visible light range and an orthodontic device using the same can be provided through an improved photoinitiator system including Lucirin TPO-L and ethyl 4-(dimethylamino)benzoate. As a result, rapid curing using a blue light LED is possible, and even thick parts can be uniformly cured, thereby obtaining an effect of improving the uniformity of physical properties.

In addition, according to the present disclosure, a photocurable polymer composition that maintains crystallinity even at high temperatures of 150°C or higher and is capable of high-temperature sterilization and disinfection, and an orthodontic device using the same can be provided. As a result, repeated sterilization and disinfection in a clinical environment can be achieved, and hygienic use can be achieved.

The excellent and/or useful effects according to the present disclosure are not limited to the effects of the present disclosure described above, and those skilled in the art will also be able to obviously recognize other excellent and/or useful effects of the present disclosure that are not explicitly disclosed in the present specification based on the disclosure of the present specification, and it should be understood that these are intentionally disclosed by the present specification and are obviously included in the scope of the present disclosure.

The terms or words used in this specification and claims are not intended to be construed as being limited to their commonly used dictionary meanings, and it will be apparent to those skilled in the art that such terms or words are used in a sense intended to convey the meaning of the present disclosure within the scope of the concepts that this specification and claims are intended to clearly convey.

In addition, it will be clearly understood by those skilled in the art that the configurations described in the aspects, embodiments, examples, etc. of the present disclosure described in this specification are merely preferred examples presented at the time to enable those skilled in the art to understand and reproduce the present disclosure, and are not intended to limit the present disclosure thereto.

In addition, the description and specific embodiments of each configuration described in this specification can be obviously applied to the description and specific embodiments of each other configuration. That is, all possible combinations of the various configurations and specific embodiments disclosed in this specification will be clearly understood by those skilled in the art to fall within the scope disclosed in this specification.

The term “and/or” as used herein is a term that includes each and every combination of two or more of the items mentioned. In addition, when a singular term is used in this specification, it is disclosed including the plural unless otherwise stated.

The terms “comprise” and “comprising,” as used herein, are terms that allow the presence or addition of items other than the items mentioned, and the terms “consist,” “consist,” “consisting,” and “consisting,” as used herein, are terms that do not allow the presence or addition of items other than the items mentioned.

The term “to” as used herein indicates a numerical range in which the numerical range indicated by using the “to” above includes the values described before and after the term as lower limits and upper limits, respectively. When the upper limit and/or lower limit of any numerical range are each disclosed as multiple values, the numerical range is disclosed as having any one of the multiple lower limit values and any one of the multiple upper limit values as the lower limit and the upper limit, respectively.

The terms “about” and/or “approximately” as used herein mean a numerical range between an upper value and a lower value that is 10% greater than the value indicated using “about” and/or “approximately” above.

The terms or words used in this specification and the claims should not be interpreted as limited to their usual dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of the present disclosure based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best way. Therefore, it should be understood that the configurations described in the embodiments described in this specification are only preferred embodiments of the present disclosure and do not represent all of the technical idea of the present disclosure, and that there may be various equivalents and modified examples that can replace them at the time of this application.

Meanwhile, each description and embodiment disclosed in this specification can be applied to each other description and embodiment. That is, all combinations of various elements disclosed in this specification fall within the scope of this disclosure, and descriptions omitted in one embodiment can be interpreted in the same manner as described in other embodiments. In addition, the scope of this disclosure cannot be considered limited by the specific description described below.

According to one embodiment of the present disclosure, a photocurable shape restoring polymer composition can be provided, comprising a photocurable compound, a photoinitiator, nano silica particles, a core-shell structured acrylic impact modifier, a fluorinated methacrylate copolymer, and a benzotriazole derivative photostabilizer.

The above photocurable shape-restoring polymer composition has rigidity, stiffness, and elasticity suitable for orthodontic treatment in a first temperature range when cured, and can have original shape restoration characteristics in a second temperature range different from the first temperature range. Since the photocurable shape-restoring polymer composition has both an amorphous structure and a crystalline structure, when the composition is formed into an orthodontic device when cured, when the orthodontic device undergoes temporary deformation due to wearing in the oral cavity in the first temperature range, the intermolecular kinetic energy of the amorphous region increases in the second temperature range, so that the composition has elasticity like soft rubber, and can have a characteristic of quickly restoring its original shape in the absence of external stress.

The above photocurable shape-restoring polymer composition can have improved mechanical properties by introducing nano silica particles and a core-shell structure acrylic impact modifier. The nano silica particles can have excellent dispersibility and provide an improved wear resistance effect by forming a chemical bond with a polymer matrix by functionalizing the surface with methacrylate. In particular, the nano silica particles have a very small size of 5-50 nm and can effectively improve physical properties without affecting transparency. The methacrylate functionalization of the nano silica particles can form a covalent bond with a polymer network during the photopolymerization process to prevent phase separation and long-term deterioration of physical properties.

The core-shell structure acrylic impact modifier can effectively absorb impact energy and increase the impact resistance of the orthodontic device. This impact modifier is composed of a soft elastic core and a hard shell, and has a dual structure in which the core part absorbs impact and the shell part provides compatibility with the polymer matrix. This structure has the effect of preventing breakage and suppressing crack propagation even in an environment with high masticatory pressure. In particular, the core-shell structure can form a microscopic elastic region within the polymer network formed after curing, which can play a role in reducing brittleness while maintaining overall rigidity.

Fluorinated methacrylate copolymers change the surface properties by introducing fluorine components to the polymer surface. Fluorinated surfaces have low surface energy, so the coefficient of friction decreases, which can facilitate the attachment and removal of orthodontic devices. In addition, fluorinated surfaces have increased hydrophobicity, which can reduce contamination and discoloration by saliva or food, and can also inhibit the attachment of microorganisms. Fluorinated methacrylate copolymers are chemically bonded to the polymer network through methacrylate groups, so that surface properties can be maintained over time, unlike simple additives.

Benzotriazole derivative photostabilizers can prevent photodegradation of polymers through a mechanism that effectively absorbs ultraviolet rays and releases energy in a harmless form. In particular, benzotriazole derivatives having a methacrylate functional group can be covalently fixed to the polymer network during the photopolymerization process, and thus can provide a long-term stable protective effect without being eluted. This can provide aesthetic advantages by maintaining the color stability of the orthodontic device even when worn in the oral cavity for a long period of time.

The photocurable compound may include at least one selected from aliphatic urethane dimethacrylate, caprolactone urethane triacrylate, bisphenol A ethoxylate dimethacrylate, tricyclodecane dimethacrylate, and polyethylene glycol diacrylate.

Aliphatic urethane dimethacrylate has a structure with a flexible urethane bond and a methacrylate terminal group, and can be a major component that provides appropriate hardness and elasticity after crosslinking. Caprolactone urethane triacrylate is a trifunctional acrylate that can play a role in increasing crosslinking density and increasing mechanical strength. Bisphenol A ethoxylate dimethacrylate can provide rigidity and contribute to providing appropriate orthodontic force required for orthodontic treatment.

In particular, tricyclodecane dimethacrylate has a rigid tricyclodecane structure, which can increase the rigidity of the polymer while providing appropriate impact resistance. The three-dimensional structure of tricyclodecane can have the effect of relieving internal stress by increasing the free volume between the polymer chains. In addition, this component can provide the advantage of improved precision during curing by having a low polymerization shrinkage.

Polyethylene glycol diacrylate is a structure with a flexible polyethylene glycol chain and a reactive acrylate terminal group, and can play a role in finely controlling the glass transition temperature and mechanical properties by controlling the crosslinking density. The polyethylene glycol portion can affect the shape recovery properties by controlling the moisture content inside the polymer by imparting some hydrophilicity.

The above photoinitiator may include at least one selected from Lucirin TPO-L, phenylglyoxylate methyl ester, and ethyl 4-(dimethylamino)benzoate. Lucirin TPO-L is a liquid acylphosphine oxide-based photoinitiator that has high photosensitivity in the visible light range (particularly 400-420 nm), thereby enabling curing using a blue light LED. Phenylglyoxylate methyl ester is an α-hydroxyketone series photoinitiator that can effectively work in the ultraviolet range.

Ethyl 4-(dimethylamino)benzoate is an amine co-initiator, which can greatly improve the photoinitiation efficiency when used with other photoinitiators. In particular, the combination of Lucirin TPO-L and ethyl 4-(dimethylamino)benzoate can increase the photopolymerization speed and increase the curing depth through a synergistic effect, so that even thick parts can be uniformly cured. These characteristics can be advantageous when manufacturing orthodontic appliances with complex shapes.

The above nano silica particles may be particles with a size of 5-50 nm whose surface is functionalized with methacrylate. The methacrylate functionalization of the nano silica surface can be accomplished using a coupling agent such as silanopropyl methacrylate, which can react with silanol groups on the silica surface to introduce methacrylate functional groups. The nano silica functionalized in this way can be covalently incorporated into a polymer network during a photopolymerization process, thereby improving dispersibility and maximizing the effect of reinforcing mechanical properties.

The above core-shell structure acrylic impact modifier has a structure having a hard shell based on acrylate or methacrylate and a soft core based on butyl acrylate or ethylhexyl acrylate, and may have a particle size of 80-300 nm. This particle size can provide sufficient impact absorption ability while having a minimal effect on transparency. The core of the impact modifier is composed of a soft polymer having a low glass transition temperature (-50°C or lower) to effectively absorb impact energy, and the shell can provide compatibility with the polymer matrix to improve dispersibility.

The above fluorinated methacrylate copolymer may be a copolymer of 2,2,2-trifluoroethyl methacrylate and methyl methacrylate or butyl methacrylate. The fluorinated portion in this copolymer tends to migrate to the surface and form a fluorinated layer, so that even a small amount thereof can effectively change surface properties. The methacrylate portion can bind to the polymer network during the photopolymerization process to provide a permanent surface modification effect.

The above benzotriazole derivative photostabilizer can be 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole or 2-(2'-hydroxy-3'-tert-butyl-5'-methacryloyloxypropylphenyl)-2H-benzotriazole. These compounds have both a benzotriazole structure with excellent ultraviolet absorption capability and a photopolymerizable methacrylate functional group, so that they have the advantage of being covalently fixed to a polymer network during the curing process and not being eluted. In particular, derivatives having a tert-butyl group have excellent heat stability and can maintain a stable protective effect even during a high-temperature sterilization process.

The above photocurable shape-restoring polymer composition may further include at least one selected from a dithiol compound and a polyphenyl ether. The dithiol compound may act as a crosslinking regulator to provide an effect of relieving internal stress, and the polyphenyl ether may act as a heat-stabilizing additive to provide an effect of improving heat resistance.

Dithiol compounds can reduce internal stress by forming more flexible bonds by reacting with methacrylate groups through thiol-ene reaction. This can provide the effect of reducing shrinkage stress during curing and improving the precision of the final product. In addition, thiol-ene reaction can provide the advantage of improving surface hardening properties because it is less inhibited by oxygen.

Polyphenyl ether is a polymer with excellent thermal stability of an aromatic structure, and can play a role in improving shape stability at high temperatures by existing in a dispersed phase. In particular, the aromatic structure maintains stable crystallinity even at high temperatures of 150℃ or higher, so that changes in shape and properties can be minimized even during high-temperature sterilization and disinfection processes.

For example, the photocurable compound may contain 40 to 70 parts by weight of aliphatic urethane dimethacrylate based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the aliphatic urethane dimethacrylate may be contained in an amount of 50 to 65 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the aliphatic urethane dimethacrylate is less than 40 parts by weight, it may be difficult to obtain sufficient mechanical strength, and if it exceeds 70 parts by weight, the effects of other components may be reduced.

For example, the photocurable compound may contain caprolactone urethane triacrylate in an amount of 1 to 25 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the caprolactone urethane triacrylate may be contained in an amount of 4 to 25 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of caprolactone urethane triacrylate is less than 1 part by weight, the effect of improving crosslinking density may be minimal, and if it exceeds 25 parts by weight, brittleness may increase due to excessive crosslinking.

For example, the photocurable compound may contain 5 to 25 parts by weight of tricyclodecane dimethacrylate based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the tricyclodecane dimethacrylate may be contained in an amount of 8 to 20 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of tricyclodecane dimethacrylate is less than 5 parts by weight, the effect of improving rigidity and impact resistance may be minimal, and if it exceeds 25 parts by weight, processability may be reduced due to excessive rigidity.

For example, the photocurable compound may contain 2 to 15 parts by weight of polyethylene glycol diacrylate based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the polyethylene glycol diacrylate may be contained in an amount of 5 to 12 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of polyethylene glycol diacrylate is less than 2 parts by weight, the effect of controlling crosslinking density may be minimal, and if it exceeds 15 parts by weight, the physical properties may be deteriorated due to excessive hydrophilicity.

For example, the photoinitiator may contain 2 to 10 parts by weight of Lucirin TPO-L based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the Lucirin TPO-L may be contained in an amount of 3 to 8 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of Lucirin TPO-L is less than 2 parts by weight, it may be difficult to obtain sufficient photoinitiation efficiency, and if it exceeds 10 parts by weight, deterioration of physical properties may occur due to residual photoinitiator after curing.

For example, the photoinitiator may contain 1 to 5 parts by weight of ethyl 4-(dimethylamino)benzoate based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the ethyl 4-(dimethylamino)benzoate may be contained in an amount of 1.5 to 4 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of ethyl 4-(dimethylamino)benzoate is less than 1 part by weight, the effect may be minimal upon release, and if it exceeds 5 parts by weight, there is a possibility of discoloration due to residue after curing.

For example, the nano silica particles may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the nano silica particles may be included in an amount of 2 to 8 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the nano silica particles is less than 1 part by weight, the effect of improving mechanical properties may be minimal, and if it exceeds 10 parts by weight, the dispersibility may deteriorate and the transparency may decrease.

For example, the core-shell structure acrylic impact modifier may be included in an amount of 3 to 12 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the core-shell structure acrylic impact modifier may be included in an amount of 4 to 10 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the impact modifier is less than 3 parts by weight, the effect of improving impact resistance may be minimal, and if it exceeds 12 parts by weight, the rigidity may be excessively reduced and the transparency may be degraded.

For example, the fluorinated methacrylate copolymer may be included in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the fluorinated methacrylate copolymer may be included in an amount of 0.8 to 2.5 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the fluorinated methacrylate copolymer is less than 0.5 parts by weight, the surface modification effect may be minimal, and if it exceeds 3 parts by weight, the adhesion may be reduced due to excessive hydrophobicity.

For example, the benzotriazole derivative photostabilizer may be included in an amount of 0.2 to 2 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. Preferably, the benzotriazole derivative photostabilizer may be included in an amount of 0.3 to 1.5 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the photostabilizer is less than 0.2 parts by weight, the ultraviolet ray blocking effect may be minimal, and if it exceeds 2 parts by weight, the photopolymerization efficiency may be reduced.

For example, the dithiol compound is 1,4-butanedithiol, 2,2'-(ethylenedioxy)dietethanethiol, hexane-1,6-dithiol or trimethylolpropane tris(3-mercaptopropionate), and may be included in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of the total photocurable shape-restoring polymer composition. If the content of the dithiol compound is less than 0.1 parts by weight, the internal stress relaxation effect may be minimal, and if it exceeds 2 parts by weight, the mechanical properties may deteriorate due to excessive thiol-ene reaction.

For example, the polyphenyl ether is a polymer of 2,6-dimethylphenol and may be included in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. If the content of the polyphenyl ether is less than 0.5 parts by weight, the effect of improving thermal stability may be minimal, and if it exceeds 3 parts by weight, transparency may be reduced due to phase separation.

For example, the photocurable shape-restoring polymer composition may have a glass transition temperature of 45 to 120°C after curing. A glass transition temperature in this range is a temperature range in which shape restoration is possible at a specific temperature while maintaining hard properties at body temperature (approximately 37°C). In particular, 45-60°C is a temperature range that can be easily reached in hot water, and can induce shape restoration in a clinically safe and convenient manner. A higher glass transition temperature in the range of 60-120°C may be useful in cases where better mechanical strength and shape stability are required.

For example, the photocurable shape-restoring polymer composition may have a characteristic of maintaining crystallinity even at a temperature of 150°C or higher after curing. This high heat resistance is very useful in a dental clinical environment that requires high-temperature sterilization (autoclave, 121-135°C). In particular, since the shape and physical properties are maintained even after sterilization, repeated sterilization is possible, so hygienic use is possible. The synergistic effect of polyphenyl ether and nano silica particles may contribute to this high-temperature stability.

As an example, the photocurable shape-restoring polymer composition can be used for direct 3D printing. The improved photocuring properties due to the combination of Lucirin TPO-L and ethyl 4-(dimethylamino)benzoate can improve interlayer bonding strength and precision in a 3D printing process. In addition, the low polymerization shrinkage of tricyclodecane dimethacrylate can improve the dimensional accuracy of 3D printed products. This allows for precise manufacturing of orthodontic appliances with complex shapes.

According to another embodiment of the present disclosure, an orthodontic device manufactured using the photocurable shape-restoring polymer composition can be provided. The orthodontic device can have improved durability and impact resistance. In particular, the wear resistance and impact strength are improved due to the nano silica and the core-shell structure acrylic impact modifier, so that the device can be suitable for patients with strong chewing force or for orthodontic treatment that requires long-term use.

In addition, since this orthodontic device has a characteristic of restoring the original shape at a certain temperature, it can be restored to its original shape through simple heat treatment without having to make a new orthodontic device that has been deformed during the orthodontic process. This has the advantage of saving cost and time. The improvement of surface properties due to the fluorinated methacrylate copolymer can make it easier to put on and take off the orthodontic device, thereby increasing patient convenience.

The improved color stability due to the benzotriazole derivative light stabilizer minimizes discoloration even when worn for a long period of time, which can maintain aesthetic satisfaction. This can be particularly advantageous for patients who value aesthetics, such as adult patients. In addition, because it maintains crystallinity even at temperatures above 150℃, it can be sterilized at high temperatures, allowing hygienic use.

For example, the orthodontic device can be used as an implant guide or a surgical template. The improved mechanical properties and precision due to nano silica can be suitable for applications requiring precise positioning, such as implant placement. In addition, the improved impact resistance due to the core-shell structure acrylic impact modifier has the advantage of being able to withstand stress during surgery.

These implant guides or surgical templates can be restored to their original shape with a simple heat treatment even if they are deformed due to their shape memory properties, so that they can maintain accurate surgical plans. In addition, they can be sterilized at high temperatures, so they can be suitable for aseptic surgical environments. Long-term stability due to photostabilizers can provide the advantage of being able to be stored without discoloration or changes in physical properties during the preoperative preparation process.

The photocurable shape restoring polymer composition of the present invention can act in the polymerization process by the following mechanism. First, the photoinitiator, Lucirin TPO-L, absorbs visible light to generate an active radical, and this radical can initiate the polymerization of a methacrylate group. Ethyl 4-(dimethylamino)benzoate, as an amine co-initiator, can react with an intermediate to generate more active species, thereby increasing the polymerization rate.

During the polymerization process, the methacrylate groups on the surface of the nano silica particles can form a covalent bond with the polymer network to form a uniformly dispersed nanocomposite. The shell portion of the core-shell structure acrylic impact modifier is also dispersed by combining with the polymer network, and at this time, the core portion can maintain elasticity to form a fine impact-absorbing region.

Fluorinated methacrylate copolymers can partially combine with the polymer network during the polymerization process, and the fluorinated portions can move to the surface to form a layer with low surface energy. Benzotriazole derivative photostabilizers can also be fixed to the network through the methacrylate group, providing a long-term, stable UV-blocking effect.

The thiol group of the dithiol compound can relieve internal stress by forming a more flexible linkage through the double bond and thiol-ene reaction of methacrylate. The polyphenyl ether can exist as a dispersed phase in the polymer matrix, thereby improving the shape stability at high temperatures.

Through these complex polymerization mechanisms and interactions of components, the photocurable shape-restoring polymer composition of the present invention can have rigidity and elasticity suitable for orthodontic treatment, shape-restoring properties at a specific temperature, improved mechanical properties and durability, and excellent surface properties and color stability.

The photocurable shape-restoring polymer composition of the present invention can be manufactured by the following method. First, photocurable compounds such as aliphatic urethane dimethacrylate, caprolactone urethane triacrylate, bisphenol A ethoxylate dimethacrylate, tricyclodecane dimethacrylate, and polyethylene glycol diacrylate can be mixed at a predetermined ratio.

To this mixture, photoinitiator Lucilin TPO-L, phenylglyoxylic acid methyl ester, and ethyl 4-(dimethylamino)benzoate can be added and mixed uniformly. Next, methacrylate-functionalized nano silica particles can be slowly added in small amounts and mixed so as to be uniformly dispersed. At this time, the dispersibility of the nano particles can be improved by using ultrasonic treatment or a high-shear mixer.

A core-shell structure acrylic impact modifier, a fluorinated methacrylate copolymer, a benzotriazole derivative light stabilizer, a dithiol compound, and a polyphenyl ether can be sequentially added and uniformly mixed. The final mixture can be stirred in a vacuum to remove air bubbles inside.

The photocurable shape-restoring polymer composition manufactured in this way can be molded into an orthodontic device through direct 3D printing or mold forming. The molded product is cured using a blue light LED or UV light source. The curing conditions can be adjusted according to the type and intensity of the light source and the thickness of the product, and generally, a curing time of 10 to 30 minutes may be required.

The hardened product can be subjected to post-processing as needed. For example, the surface can be polished to make it smooth, or residual stress can be relieved through additional heat treatment. The finished orthodontic appliance can be hygienically used by undergoing high-temperature sterilization before use.

The orthodontic appliance manufactured in this way can be used in an oral environment while maintaining rigidity and elasticity at body temperature to exert corrective force, and if deformation occurs during the correction process, can be restored to its original shape at a temperature of 45-120℃. The wear resistance and impact resistance are improved, so it maintains durability even after long-term use, and the surface has a low coefficient of friction for easy attachment and detachment, and the UV-blocking effect prevents discoloration.

Hereinafter, the present disclosure will be described in more detail using examples. Process conditions and preparation steps not specified in the examples below may be process conditions or preparation steps that are obvious in the technical field to which the present disclosure belongs, and a person skilled in the art will be able to select them without much difficulty based on the present disclosure and reproduce the problem-solving principle of the present disclosure.

In addition, in the manufacturing method according to the present disclosure, unless otherwise specified, each step constituting the manufacturing method is performed at room temperature (25°C), and it should be understood that each step is performed by means and tools that can be derived without much difficulty by a person skilled in the art.

Examples 1 to 10: Preparation of nano silica reinforced photocurable shape restoring polymer composition according to the present disclosure

As photocurable compounds, aliphatic urethane dimethacrylate (PP1), caprolactone urethane triacrylate (PP2), bisphenol A ethoxylate dimethacrylate (PP3), tricyclodecane dimethacrylate (PP4), polyethylene glycol diacrylate (PP5), as photoinitiators, Lucirin TPO-L (ID1), phenylglyoxylic acid methyl ester (ID2), ethyl 4-(dimethylamino)benzoate (ID3), as nano silica particles, methacrylate-functionalized silica nanoparticles (10 nm) (SI), a core-shell structured acrylic impact modifier (CS), a fluorinated methacrylate copolymer (FM), a benzotriazole derivative light stabilizer (BT), as a dithiol compound, trimethylolpropane tris(3-mercaptopropionate) (DT), and polyphenyl ether (PE) are used, based on 100 g of the total photocurable shape-restoring polymer composition. It was prepared by weight according to the weight part as follows.

Example 1: Aliphatic urethane dimethacrylate (60 g), caprolactone urethane triacrylate (15 g), bisphenol A ethoxylate dimethacrylate (5 g), tricyclodecane dimethacrylate (15 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (4 g), phenylglyoxylic acid methyl ester (1 g), ethyl 4-(dimethylamino)benzoate (2 g), methacrylate-functionalized silica nanoparticles (3 g), core-shell structured acrylic impact modifier (5 g), fluorinated methacrylate copolymer (1 g), benzotriazole derivative light stabilizer (0.5 g), trimethylolpropane tris(3-mercaptopropionate) (0.5 g), and polyphenyl ether (0.8 g) were placed in a glass beaker and uniformly mixed using a magnetic stirrer at 60°C for 2 hours. The mixture was then treated using an ultrasonic processor for 30 minutes to increase the dispersion of nanoparticles. Finally, the mixture was placed in a vacuum desiccator and degassed for 30 minutes.

Example 2: Aliphatic urethane dimethacrylate (55 g), caprolactone urethane triacrylate (20 g), tricyclodecane dimethacrylate (10 g), polyethylene glycol diacrylate (10 g), Lucirin TPO-L (6 g), ethyl 4-(dimethylamino)benzoate (3 g), methacrylate-functionalized silica nanoparticles (5 g), core-shell structured acrylic impact modifier (8 g), fluorinated methacrylate copolymer (2 g), benzotriazole derivative light stabilizer (1 g), and trimethylolpropane tris(3-mercaptopropionate) (1 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 3: Aliphatic urethane dimethacrylate (65 g), caprolactone urethane triacrylate (10 g), bisphenol A ethoxylate dimethacrylate (5 g), tricyclodecane dimethacrylate (5 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (3 g), phenylglyoxylic acid methyl ester (2 g), ethyl 4-(dimethylamino)benzoate (1 g), methacrylate-functionalized silica nanoparticles (2 g), core-shell structured acrylic impact modifier (4 g), fluorinated methacrylate copolymer (0.5 g), benzotriazole derivative light stabilizer (0.2 g), and polyphenyl ether (2 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 4: Aliphatic urethane dimethacrylate (50 g), caprolactone urethane triacrylate (15 g), bisphenol A ethoxylate dimethacrylate (10 g), tricyclodecane dimethacrylate (15 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (8 g), phenylglyoxylic acid methyl ester (1 g), ethyl 4-(dimethylamino)benzoate (3 g), methacrylate-functionalized silica nanoparticles (6 g), core-shell structured acrylic impact modifier (10 g), fluorinated methacrylate copolymer (1.5 g), benzotriazole derivative light stabilizer (1.2 g), trimethylolpropane tris(3-mercaptopropionate) (1 g), and polyphenyl ether (1.5 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 5: Aliphatic urethane dimethacrylate (55 g), caprolactone urethane triacrylate (10 g), bisphenol A ethoxylate dimethacrylate (5 g), tricyclodecane dimethacrylate (20 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (5 g), phenylglyoxylic acid methyl ester (2 g), ethyl 4-(dimethylamino)benzoate (2 g), methacrylate-functionalized silica nanoparticles (4 g), core-shell structured acrylic impact modifier (6 g), fluorinated methacrylate copolymer (1 g), benzotriazole derivative light stabilizer (0.8 g), trimethylolpropane tris(3-mercaptopropionate) (0.8 g), and polyphenyl ether (1 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 6: Aliphatic urethane dimethacrylate (60 g), caprolactone urethane triacrylate (15 g), tricyclodecane dimethacrylate (12 g), polyethylene glycol diacrylate (8 g), lucirin TPO-L (7 g), ethyl 4-(dimethylamino)benzoate (4 g), methacrylate-functionalized silica nanoparticles (8 g), core-shell structure acrylic impact modifier (7 g), fluorinated methacrylate copolymer (2.5 g), benzotriazole derivative light stabilizer (1.5 g), and polyphenyl ether (2.5 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 7: Aliphatic urethane dimethacrylate (65 g), caprolactone urethane triacrylate (5 g), bisphenol A ethoxylate dimethacrylate (10 g), tricyclodecane dimethacrylate (8 g), polyethylene glycol diacrylate (12 g), Lucilin TPO-L (4 g), phenylglyoxylic acid methyl ester (3 g), ethyl 4-(dimethylamino)benzoate (2 g), methacrylate-functionalized silica nanoparticles (10 g), core-shell structured acrylic impact modifier (12 g), fluorinated methacrylate copolymer (3 g), benzotriazole derivative light stabilizer (2 g), and trimethylolpropane tris(3-mercaptopropionate) (1.5 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 8: Aliphatic urethane dimethacrylate (55 g), caprolactone urethane triacrylate (20 g), bisphenol A ethoxylate dimethacrylate (5 g), tricyclodecane dimethacrylate (10 g), polyethylene glycol diacrylate (10 g), Lucilin TPO-L (3 g), phenylglyoxylic acid methyl ester (1 g), ethyl 4-(dimethylamino)benzoate (1 g), methacrylate-functionalized silica nanoparticles (1 g), core-shell structure acrylic impact modifier (3 g), fluorinated methacrylate copolymer (0.8 g), benzotriazole derivative light stabilizer (0.3 g), trimethylolpropane tris(3-mercaptopropionate) (0.5 g), and polyphenyl ether (0.5 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 9: Aliphatic urethane dimethacrylate (60 g), caprolactone urethane triacrylate (10 g), bisphenol A ethoxylate dimethacrylate (15 g), tricyclodecane dimethacrylate (5 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (5 g), phenylglyoxylic acid methyl ester (2 g), ethyl 4-(dimethylamino)benzoate (3 g), methacrylate-functionalized silica nanoparticles (7 g), core-shell structure acrylic impact modifier (9 g), fluorinated methacrylate copolymer (2 g), benzotriazole derivative light stabilizer (1 g), trimethylolpropane tris(3-mercaptopropionate) (1.2 g), and polyphenyl ether (1.8 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 10: Aliphatic urethane dimethacrylate (50 g), caprolactone urethane triacrylate (25 g), bisphenol A ethoxylate dimethacrylate (5 g), tricyclodecane dimethacrylate (10 g), polyethylene glycol diacrylate (5 g), Lucilin TPO-L (6 g), phenylglyoxylic acid methyl ester (1 g), ethyl 4-(dimethylamino)benzoate (2 g), methacrylate-functionalized silica nanoparticles (5 g), core-shell structured acrylic impact modifier (5 g), fluorinated methacrylate copolymer (1 g), benzotriazole derivative light stabilizer (0.7 g), and polyphenyl ether (3 g) were placed in a glass beaker and treated in the same manner as in Example 1.

Example 11: Manufacturing of an orthodontic appliance using a nano-silica-reinforced photocurable shape-restoring polymer composition

Using the composition manufactured in Example 4, a transparent orthodontic device was manufactured as follows. First, a dental model of a patient requiring orthodontic treatment was scanned with a 3D scanner to obtain digital data. Based on this data, a 3D digital model of an orthodontic device that meets the orthodontic goal was designed. Based on the designed digital model data, an orthodontic device was printed using a 3D printer using the DLP (Digital Light Processing) method. The printing parameters were a layer thickness of 50 μm, an exposure time of 3 seconds per layer, and a 405 nm LED light source. After printing, the composition was soaked in isopropyl alcohol for 5 minutes to remove unreacted information, and then post-cured for 10 minutes using a blue light LED light source (420 nm, 40 mW/cm²). The surface of the cured orthodontic device was polished to finish it.

Example 12: Manufacturing of an implant guide using a nano-silica reinforced photocurable shape-restoring polymer composition

An implant guide was manufactured as follows using the composition manufactured in Example 7. An implant placement plan was established by integrating the patient's CT scan data and oral scan data. A 3D digital model of the implant guide was designed according to this plan. Based on the designed digital model data, the implant guide was printed using a 3D printer of the SLA (Stereolithography) method. The printing parameters were a layer thickness of 25 μm, an exposure time of 2.5 seconds per layer, and a 385 nm LED light source. After printing, the composition was soaked in isopropyl alcohol for 10 minutes to remove unreacted composition, and additionally post-cured with a UV light source (365 nm, 60 mW/cm²) for 20 minutes. The cured implant guide was finished by inserting a metal sleeve through which an implant drill would pass into the exact position and then polishing the surface.

Example 13: Fabrication of surgical template using nano silica reinforced photocurable shape restoring polymer composition

Using the composition manufactured in Example 6, an orthognathic surgical template was manufactured as follows. An orthognathic surgical plan was established based on the patient's CT scan data, and a 3D digital model of the surgical template was designed accordingly. Based on the designed digital model data, the surgical template was printed using a 3D printer of the LCD (Liquid Crystal Display) type. The printing parameters were a layer thickness of 35 μm, an exposure time of 4 seconds per layer, and a 405 nm LED light source. After printing, the composition was immersed in isopropyl alcohol for 8 minutes to remove unreacted composition, and additionally post-cured with a blue light LED light source (420 nm, 40 mW/cm²) for 15 minutes. The cured surgical template was sterilized at 134°C for 3 minutes using a high-pressure steam sterilizer, and then used.

Experimental Example 1: Mechanical Properties Evaluation

The compositions of Examples 1 to 10 were tested for three-point flexural strength, flexural modulus, and fracture toughness on specimens (25 x 2 x 2 mm) manufactured according to the ISO 4049 standard. Each specimen was cured by irradiating both sides with a 405 nm LED light source (40 mW/cm²) for 60 seconds, and then stored in distilled water at 37°C for 24 hours before measurement.

The three-point flexural strength test was measured using a universal testing machine at the conditions of a distance between support points of 20 mm and a crosshead speed of 1 mm/min. The flexural strength of the specimen manufactured with the composition of Example 4 was measured to be 124 MPa, which appears to be due to the synergistic effect of the nano silica particles and the core-shell structure impact modifier. The flexural strength range of the specimens manufactured with the compositions of Examples 1 to 10 was measured to be 95-130 MPa.

The flexural modulus was calculated from the initial slope of the stress-strain curve obtained from the three-point flexural test. The flexural modulus of the specimen manufactured with the composition of Example 4 was measured to be 3.2 GPa, and the flexural modulus range of the specimens manufactured with the compositions of Examples 1 to 10 was measured to be 2.5-3.5 GPa.

Fracture toughness was measured using a SENB (Single Edge Notched Beam) specimen. The fracture toughness (KIC) of the specimen manufactured with the composition of Example 4 was measured to be 2.3 MPa·m^(1/2), and the fracture toughness range of the specimens manufactured with the compositions of Examples 1 to 10 was measured to be 1.8-2.4 MPa·m^(1/2).

Experimental Example 2: Impact Resistance Evaluation

Charpy impact tests were performed on specimens (80 x 10 x 4 mm) manufactured according to the ISO 179 standard with the compositions of Examples 1 to 10. Each specimen was cured by irradiating both sides with a 405 nm LED light source (40 mW/cm²) for 90 seconds, and then stored in distilled water at 37°C for 24 hours before measurement.

The Charpy impact test was performed under the condition of impact energy of 2.0 J. The impact strength of the specimen manufactured with the composition of Example 4 was measured as 12.5 kJ/m², which seems to be due to the effect of the core-shell structure impact modifier. The impact strength range of the specimens manufactured with the compositions of Examples 1 to 10 was measured as 8.2-13.8 kJ/m². In particular, the highest impact strength (13.8 kJ/m²) was observed in Example 7 (12 parts by weight) having a high content of the core-shell structure impact modifier.

Experimental Example 3: Wear Resistance Evaluation

Disc-shaped specimens having a diameter of 10 mm and a thickness of 2 mm were produced using the compositions of Examples 1 to 10, and a pin-on-disk wear test was performed according to the ASTM G99 standard. Each specimen was irradiated on both sides with a 405 nm LED light source (40 mW/cm²) for 60 seconds to be cured, and after curing, they were stored in distilled water at 37°C for 24 hours and then measured.

The wear test was conducted using an alumina ball with a diameter of 6 mm under the conditions of a load of 5 N, a rotation speed of 60 rpm, and a total sliding distance of 1000 m. The wear amount was calculated from the difference in the weight of the specimen before and after the wear test. The wear amount of the specimen manufactured with the composition of Example 4 was measured to be 1.2 mg, and the wear amounts of the specimens manufactured with the compositions of Examples 1 to 10 were measured to be in the range of 0.9-2.8 mg. In particular, the lowest wear amounts (1.0 mg and 0.9 mg, respectively) were observed in Example 6 (8 parts by weight) and Example 7 (10 parts by weight) having a high content of nano silica particles.

Experimental Example 4: Surface Characteristics Evaluation

Disc-shaped specimens with a diameter of 15 mm and a thickness of 3 mm were produced using the compositions of Examples 1 to 10, and contact angle measurements and surface friction coefficients were measured. Each specimen was irradiated on both sides with a 405 nm LED light source (40 mW/cm²) for 60 seconds to cure, and after curing, they were stored in distilled water at 37°C for 24 hours and then measured.

The contact angle was measured using the water droplet method. The water contact angle of the specimen manufactured with the composition of Example 4 was measured to be 82°. In the specimen of Example 7 (3 parts by weight) having a high content of fluorinated methacrylate copolymer, the water contact angle was measured to be the highest at 95°, which seems to be because the fluorinated component moved to the surface and increased the hydrophobicity.

The surface friction coefficient was measured using a sliding friction coefficient measuring device. The dry state friction coefficient of the specimen manufactured with the composition of Example 4 was measured as 0.28, and the wet state (artificial saliva) friction coefficient was measured as 0.22. In the specimen of Example 7 (3 parts by weight) having a high content of fluorinated methacrylate copolymer, the dry state friction coefficient was measured as 0.18, and the wet state friction coefficient was measured as 0.15, which were the lowest.

Experimental Example 5: Color Stability Evaluation

Disc-shaped specimens with a diameter of 15 mm and a thickness of 3 mm were produced with the compositions of Examples 1 to 10, and color changes due to exposure to ultraviolet rays were measured. Each specimen was irradiated on both sides with a 405 nm LED light source (40 mW/cm²) for 60 seconds to cure, and after curing, they were stored in distilled water at 37°C for 24 hours, and then the initial color was measured.

UV exposure was performed for a total of 300 hours using a UV-A lamp (365 nm, 1.2 mW/cm²), and color was measured at 100-hour intervals. Color was measured using a spectrocolorimeter in the CIE L*a*b* color space, and the color change (ΔE) was calculated as the difference from the initial color.

The color change (ΔE) of the specimen manufactured with the composition of Example 4 was measured as 2.1 after 300 hours of exposure. In the specimen of Example 7 (2 parts by weight) with a high content of benzotriazole derivative photostabilizer, the color change was measured to be the lowest at 1.3 after 300 hours of exposure. In the specimen of Example 3 (0.2 parts by weight) with the least amount of photostabilizer added, the color change was measured to be the highest at 4.8 after 300 hours of exposure.

Experimental Example 6: Evaluation of Shape Restoration Characteristics

Modified specimens (64 x 10 x 3.3 mm) were produced with the compositions of Examples 1 to 10, referring to the ISO 1567 standard. Each specimen was cured by irradiating both sides with a 405 nm LED light source (40 mW/cm²) for 90 seconds, and then stored in distilled water at 37°C for 24 hours.

To evaluate the shape recovery characteristics, the specimen was allowed to reach an equilibrium state for 30 minutes in a water bath at 37°C, and then a load was applied to the center of the specimen using a three-point bending device to deform it so that a deflection of 2 mm occurred. After cooling to room temperature in the deformed state to fix the deformation, the specimen was placed in water baths of various temperatures (45, 55, 65, 75, 85, 95, 105, 115°C) for deformation recovery, and the shape recovery rate was measured. The shape recovery rate was calculated by the following equation:

Shape recovery rate (%) = ((2 - residual deflection) / 2) x 100

For the specimen manufactured with the composition of Example 4, the shape recovery rate was measured to be 85% after 30 seconds at 65°C, and 98% after 60 seconds. Example compositions having different glass transition temperatures exhibited optimal shape recovery characteristics at different temperature ranges. For example, the specimen of Example 5 (20 parts by weight) having a high content of tricyclodecane dimethacrylate had a shape recovery rate of 82% after 30 seconds at 75°C, and 97% after 60 seconds. On the other hand, the specimen of Example 7 (12 parts by weight) having a high content of polyethylene glycol diacrylate had a shape recovery rate of 88% after 30 seconds at 55°C, and 99% after 60 seconds.

The specimens manufactured with the compositions of all examples achieved a shape recovery rate of more than 95% within 2 minutes at their respective optimum shape recovery temperatures. In addition, no significant degradation in shape recovery characteristics was observed even after 10 repeated deformation-recovery cycles.

Experimental Example 7: Heat Resistance Evaluation

Disc-shaped specimens with a diameter of 15 mm and a thickness of 3 mm were produced with the compositions of Examples 1 to 10, and the changes in physical properties according to exposure to high temperatures were measured. Each specimen was cured by irradiating both sides with a 405 nm LED light source (40 mW/cm²) for 60 seconds, and after curing, it was stored in distilled water at 37°C for 24 hours, and then the initial physical properties were measured.

To evaluate heat resistance, the specimens were sterilized in a high-temperature sterilizer at 134°C and 2 atm for 10 minutes, then cooled to room temperature and the Vickers hardness and flexural strength were measured. In addition, the mass change and appearance change of the specimens were observed.

For the specimens manufactured with the composition of Example 4, the Vickers hardness was maintained at 96.5% of the initial value after high-temperature sterilization, and the flexural strength was maintained at 94.2% of the initial value. The mass change was less than 0.3%, and no deformation or discoloration in appearance was observed.

In the specimen of Example 10 (3 parts by weight) with a high polyphenyl ether content, the Vickers hardness and the flexural strength maintained 98.2% and 97.5% of the initial value, respectively, even after high-temperature sterilization, showing the best heat resistance. On the other hand, in the specimens of Examples 2 and 7 that did not contain polyphenyl ether, the Vickers hardness and the flexural strength slightly deteriorated to 92-93% and 88-90% of the initial value, respectively, after high-temperature sterilization, but no serious deformation or deterioration of properties that would affect clinical use occurred.

Additionally, specimens manufactured with the compositions of all examples maintained clinically acceptable levels of physical properties even after five repeated high-temperature sterilization treatments.

Experimental Example 8: Evaluation of Photocuring Characteristics

The photocuring characteristics of the compositions of Examples 1 to 10 were measured under various light sources (UV-A: 365 nm, blue light LED: 405 nm, 420 nm). The photocuring characteristics were evaluated using real-time FTIR (Fourier Transform Infrared Spectroscopy) analysis and a depth of cure measurement method according to the ISO 4049 standard.

Real-time FTIR analysis was performed using an FTIR spectrometer equipped with an ATR (Attenuated Total Reflection) device. Each composition sample was uniformly coated on an ATR crystal, and the change in the characteristic peak (1636 cm^(-1)) of the methacrylate double bond (C=C) was measured at 1-second intervals while irradiating the light source. The double bond conversion rate was calculated by the following equation:

Conversion rate (%) = (1 - (At / A0)) x 100

Here, A0 is the area of the double bond peak before light irradiation, and At is the area of the double bond peak at time t.

For the composition of Example 4, the conversion rate was measured as 45% after 10 seconds, 68% after 20 seconds, 84% after 40 seconds, and 89% after 60 seconds when irradiated with a blue light LED (405 nm, 40 mW/cm²). In particular, the composition of Example 6 with a high content of lucirin TPO-L and ethyl 4-(dimethylamino)benzoate showed the fastest photopolymerization speed with a conversion rate of 55% after 10 seconds when irradiated with a 405 nm LED.

To measure the depth of curing, the composition was filled into a transparent cylinder mold with a diameter of 4 mm and a height of 10 mm, a light source was irradiated from above for 40 seconds, the uncured portion was removed, and the length of the cured portion was measured.

For the composition of Example 4, the curing depth was measured to be 5.2 mm when irradiated with a blue light LED (405 nm, 40 mW/cm²). In particular, the composition of Example 6 having a high content of Lucirin TPO-L and ethyl 4-(dimethylamino)benzoate showed the best result with a curing depth of 6.0 mm when irradiated with a 405 nm LED.

In addition, all exemplary compositions showed clinically sufficient curing depth (more than 3.5 mm) even when using a 420 nm blue light LED, and in particular, compositions containing Lucirin TPO-L showed excellent photopolymerization characteristics even at 420 nm.

Experimental Example 9: Accuracy Evaluation of Orthodontic Devices Manufactured with Photocurable Shape Restoring Polymer Compositions

In order to evaluate the precision of the orthodontic appliance manufactured in Example 11, 3D scan data of the original digital model and the manufactured orthodontic appliance were compared and analyzed. The manufactured orthodontic appliance was scanned using a high-resolution 3D scanner, and the comparison with the original digital model was performed using 3D comparative analysis software.

The comparative analysis results showed that the average deviation between the manufactured aligners and the original digital model was measured to be 38 μm, and the maximum deviation was measured to be 112 μm. This is a clinically acceptable level of precision, which can ensure the accurate fit of the aligners.

In addition, to evaluate the internal fit of the orthodontic appliance, the orthodontic appliance was placed on a plaster model and the internal space was measured using a silicone impression material. As a result of the measurement, the average internal space was measured to be 75 μm, indicating excellent fit of the orthodontic appliance.

Experimental Example 10: Accuracy Evaluation of Implant Guide Manufactured with Photocurable Shape Restoring Polymer Composition

To evaluate the accuracy of the implant guide manufactured in Example 12, the implant guide was mounted on a dental model, implant drilling was simulated through the guide, and the position and angle of the drill hole were measured.

First, digital implant planning data containing planned implant position and angle information was used as a reference. The implant guide was mounted on the dental model, and drilling was simulated through the guide sleeve according to the implant drilling protocol. After drilling, the model was CT-scanned to obtain the position and angle data of the drill hole.

As a result of the analysis, the average deviation between the planned implant position and the actual drill hole position was measured as 0.25 mm, and the average angular deviation was measured as 0.74°. This is a clinically excellent accuracy, which enables safe and accurate implant placement.

In addition, to evaluate the rigidity and durability of the implant guide, the actual implant drilling process was repeated five times and then the guide was checked for deformation or damage. After five drilling processes, no deformation or damage was observed in the implant guide that could be visually observed, and no significant changes were observed in the hardness measurement results around the sleeve.

Experimental Example 11: Stability Evaluation of Surgical Templates Manufactured with Photocurable Shape Restoring Polymer Compositions after High-Temperature Sterilization

To evaluate the stability after high-temperature sterilization of the surgical template manufactured in Example 13, the template was sterilized three times using a high-temperature sterilizer at 134°C for 3 minutes, and then the dimensional stability and changes in physical properties before and after sterilization were measured.

To evaluate dimensional stability, the templates before and after sterilization were scanned with a high-resolution 3D scanner and analyzed with 3D comparative analysis software. The analysis results showed that the average dimensional change of the template after three high-temperature sterilization treatments was measured to be 0.06 mm, and the maximum dimensional change was measured to be 0.11 mm. This is a clinically acceptable level of dimensional stability, indicating that the accuracy of the template is maintained even after sterilization.

To evaluate the change in physical properties, specimens were collected from the template before and after sterilization, and the Vickers hardness, flexural strength, and elastic modulus were measured. After three high-temperature sterilization treatments, the Vickers hardness was maintained at 98.1% of the initial value, the flexural strength was maintained at 97.3% of the initial value, and the elastic modulus was maintained at 99.2% of the initial value.

In addition, when the color change of the template before and after sterilization was measured using a spectrophotometer, the color change (ΔE) was measured to be 0.8, indicating that only a minimal change was observed that was difficult to distinguish with the naked eye.

These results demonstrate that the surgical template manufactured with the photocurable shape-restoring polymer composition of the present disclosure maintains excellent dimensional stability and physical properties even after a high-temperature sterilization process. This is believed to be due to the heat-resistant enhancement effect of the polyphenyl ether and nano silica particles.

Although the preferred embodiments of the present disclosure have been described in detail above, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present disclosure defined in the following claims also fall within the scope of the present disclosure.

Claims (8)

A photocurable shape restoring polymer composition comprising a photocurable compound, a photoinitiator, nano silica particles, a core-shell structured acrylic impact modifier, a fluorinated methacrylate copolymer, and a benzotriazole derivative photostabilizer,
The above photocurable compounds include aliphatic urethane dimethacrylate, caprolactone urethane triacrylate, bisphenol A ethoxylate dimethacrylate, tricyclodecane dimethacrylate, and polyethylene glycol diacrylate.
The photoinitiator comprises at least one selected from Lucilin TPO-L, phenylglyoxylic acid methyl ester, and ethyl 4-(dimethylamino)benzoate,
The above nano silica particles are particles with a size of 5-50 nm whose surface is functionalized with methacrylate.
The above photocurable compound contains 40 to 70 parts by weight of aliphatic urethane dimethacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.
The above photocurable compound contains 1 to 25 parts by weight of caprolactone urethane triacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.
The above photocurable compound contains 5 to 25 parts by weight of tricyclodecane dimethacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.
The above photocurable compound contains 2 to 15 parts by weight of polyethylene glycol diacrylate based on 100 parts by weight of the total photocurable shape-restoring polymer composition.
A photocurable shape restoring polymer composition, wherein the photocurable compound comprises bisphenol A ethoxylate dimethacrylate. In the first paragraph, the photoinitiator is a photocurable shape restoring polymer composition containing 2 to 10 parts by weight of Lucilin TPO-L based on 100 parts by weight of the entire photocurable shape restoring polymer composition. In the first paragraph, the photocurable shape-restoring polymer composition comprises 1 to 10 parts by weight of the nano silica particles based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. In the first paragraph, the core-shell structure acrylic impact modifier is included in an amount of 3 to 12 parts by weight based on 100 parts by weight of the entire photocurable shape-restoring polymer composition. In the first paragraph, the photocurable shape-restoring polymer composition comprises 0.5 to 3 parts by weight of the fluorinated methacrylate copolymer based on 100 parts by weight of the total photocurable shape-restoring polymer composition. In the first paragraph, the benzotriazole derivative photostabilizer is included in an amount of 0.2 to 2 parts by weight based on 100 parts by weight of the total photocurable shape-restoring polymer composition. An orthodontic appliance manufactured using a photocurable shape-restoring polymer composition according to any one of claims 1 to 6. delete