Method of preparing a dental product, dental product obtainable by the method, arrangement comprising a dental product and method of treating a dental product

Abstract

The present invention relates to a method of preparing a dental product having an increased ductility, the dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, the method comprising the steps of printing a dental product from a resin composition; followed by subjecting the dental product to at least one of the following procedures: (i) storing the dental product in water and / or an alcohol for at least 30 seconds at a temperature of at least 50°C, and / or (ii) storing the dental product at a relative humidity of at least 60 % and / or in an aqueous and / or alcoholic solution for at least 24 hours. The present invention further relates to a dental product obtainable by the method, an arrangement comprising a dental product, a method of treating a dental product and the use of water and / or an alcohol as a plasticizer for a dental product.

Description

[0001] Method of preparing a dental product, dental product obtainable by the method, arrangement comprising a dental product and method of treating a dental product

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the field of dental products. In particular, the present invention relates to a method of preparing a dental product having an increased ductility, a dental product obtainable by the method, an arrangement comprising a dental product, a method of treating a dental product and the use of water and / or an alcohol as a plasticizer for a dental product.

[0004] BACKGROUND

[0005] Dental products, such as occlusal splints, night guards or dental aligners, are widely- used for aligning or protecting teeth of a person, for instance for protecting the teeth from damage caused by grinding overnight. To fulfill these tasks, the dental products must be made from a material which provides sufficient mechanical stability and robustness to protect or align the teeth, but also suitable tensile properties, such as a sufficient ductility or elongation at break to avoid brittling upon insertion and during application of the dental product in the mouth.

[0006] In recent years, dental products are more and more frequently manufactured by additive manufacturing methods, such as 3D printing. Among the known 3D printing methods, stereolithography (SLA) represents a very promising approach, since it attains a very high resolution that can hardly be attained with other techniques. This technique based on photopolymerization of liquid resins has a great potential for the manufacture of tailored shaped articles in the dental or orthodontic field where a high fitting accuracy is desired. However, the hitherto used materials in stereolithography do often not fulfill the required thermo-mechanical properties and are often brittle compared with other plastic materials.

[0007] Thus, there is still room for improvements in the manufacture of tailor-made dental products by 3D printing methods. In particular, there is a need for such dental products having improved mechanical or tensile properties, in particular ductility. OBJECT OF THE INVENTION

[0008] In light of the foregoing, the present invention aims at overcoming the above described problems and drawbacks of hitherto available dental products made by 3D printing methods.

[0009] Thus, an object of the present invention is to provide a dental product having improved tensile properties, in particular an improved ductility or elongation at break, and a respective manufacturing method involving a 3D printing approach.

[0010] SUMMARY OF THE INVENTION

[0011] The present inventors have made diligent studies for solving this object and have found that by manufacturing a dental product comprising a certain type of polymer, namely a polymer comprising a functional group capable of forming a hydrogen bond, and exposing the dental product to water and / or an alcohol or a high humidity atmosphere (and / or an atmosphere with high concentrations of alcoholic vapor) at high temperature and / or for a certain (relatively long) period of time, a significant increase in ductility or elongation at break may be achieved. Without wishing to be bound to any theory, the present inventors currently assume that the polymer material of the dental product may absorb or take up and bind water and / or the alcohol by means of the functional groups capable of forming a hydrogen bond. At the same time, initial hydrogen bonds between polymer chains may be broken or interrupted by the competing absorbed water and / or alcohol so that the polymer chains are allowed to move more freely resulting in an increase in elongation at break. The present inventors have in particular found that these improved tensile properties may not only be achieved by a harsh treatment at high temperature, but also under ambient temperature over a longer period of time. Moreover, the improved tensile properties may also be maintained over a long period of time by appropriate moist storage of the dental product and even when the dental product is in use, i.e. in a person's mouth due to the humidity provided by saliva.

[0012] Accordingly, the present invention relates to a method of preparing a (three- dimensional) dental product (having an increased ductility (improved tensile properties, elongation at break), the dental product comprising (or being made from) a polymer comprising a functional group capable of forming a hydrogen bond, the method comprising the steps of: printing a dental product from a resin composition (so as to obtain a printed dental product); followed by subjecting the (printed) dental product to at least one of the following procedures:

[0013] - storing (placing, putting) the (printed) dental product in water and / or an alcohol for at least 30 seconds, in particular for at least 1 minute, in particular for at least 5 minutes, in particular for at least 10 minutes, in particular for at least 15 minutes, at a temperature of at least 50°C, in particular at least 60°C, in particular at least 70°C, in particular at least 80°C, in particular at least 90 °C, in particular at least 100 °C, and / or

[0014] - storing the (printed) dental product at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %, and / or in an aqueous and / or alcoholic solution (e.g. water and / or an alcohol) for at least 24 hours, in particular for at least 48 hours, in particular for at least 72 hours, in particular for at least 7 days, for instance at a temperature of at least 10 °C, in particular at least 15 °C, in particular at least 20 °C, in particular at least 25 °C.

[0015] The present invention further relates to a (three-dimensional) dental product obtainable (or obtained) by the method as described herein.

[0016] Moreover, the present invention relates to an arrangement (package) comprising: a (three-dimensional, printed) dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, in particular a (three-dimensional) dental product as described herein; a wrapping (packaging) enclosing (in particular sealing) the (three-dimensional) dental product (in an gas-tight manner), wherein a relative humidity within the wrapping is at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 % (In other words, the dental product is kept within the wrapping at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %).

[0017] Still further, the present invention relates to a method of treating ((for) increasing the ductility (improving tensile properties, elongation at break) of) a (3D-printed) dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, the method comprising: subjecting the (printed) dental product to at least one of the following procedures: - storing (placing, putting) the (printed) dental product in water and / or an alcohol for at least 30 seconds, in particular for at least 1 minute, in particular for at least 5 minutes, in particular for at least 10 minutes, in particular for at least 15 minutes, at a temperature of at least 50°C, in particular at least 60°C, in particular at least 70°C, in particular at least 80°C, in particular at least 90 °C, in particular at least 100 °C, and / or

[0018] - storing the (printed) dental product at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %, and / or in an aqueous and / or alcoholic solution (e.g. water and / or an alcohol) for at least 24 hours, in particular for at least 48 hours, in particular for at least 72 hours, in particular for at least 7 days, for instance at a temperature of at least 10 °C, in particular at least 15 °C, in particular at least 20 °C, in particular at least 25 °C.

[0019] Furthermore, the present invention relates to the use of water and / or an alcohol as a plasticizer for a (3D-printed) dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond.

[0020] Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following detailed description of embodiments.

[0021] DETAILLED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, details of the present invention and other features and advantages thereof will be described. However, the present invention is not limited to the following specific descriptions, but they are rather for illustrative purposes only.

[0023] It should be noted that features described in connection with one exemplary embodiment or exemplary aspect may be combined with any other exemplary embodiment or exemplary aspect, in particular features described with any exemplary embodiment of a method of preparing may be combined with any exemplary embodiment of a dental product, an arrangement, a method of treating, a use, and vice versa, unless specifically stated otherwise.

[0024] Where an indefinite or definite article is used when referring to a singular term, such as “a”, “an” or “the”, a plural of that term is also included and vice versa, unless specifically stated otherwise, whereas the word “one” or the number “1”, as used herein, typically means “just one” or “exactly one”.

[0025] The expression “comprising”, as used herein, includes not only the meaning of “comprising”, “including” or “containing”, but may also encompass “consisting essentially of’ and “consisting of”.

[0026] Unless specifically stated otherwise, the expressions “at least partially”, “at least a partial” or “at least a part of’, as used herein, may mean at least 5 % thereof, in particular at least 10 % thereof, in particular at least 15 % thereof, in particular at least 20 % thereof, in particular at least 25 % thereof, in particular at least 30 % thereof, in particular at least 35 % thereof, in particular at least 40 % thereof, in particular at least 45 % thereof, in particular at least 50 % thereof, in particular at least 55 % thereof, in particular at least 60 % thereof, in particular at least 65 % thereof, in particular at least 70 % thereof, in particular at least 75 % thereof, in particular at least 80 % thereof, in particular at least 85 % thereof, in particular at least 90 % thereof, in particular at least 95 % thereof, in particular at least 98 % thereof, and may also mean 100 % thereof.

[0027] In a first aspect, the present invention relates to a method of preparing a dental product. The dental product may in particular be a three-dimensional dental product, such as a 3D-printed dental product. The method of preparing may in particular result in a dental product having improved tensile properties, an increased ductility and / or an increased elongation at break compared with a dental product where the process step of subjecting the dental product has been omitted.

[0028] The term “dental product”, as used herein, may in particular mean any product that is intended to put into the mouth of a human or animal being, but without being swallowed. Thus, a dental product does not represent a food or a medicament. Rather, a dental product within the meaning of the present application may include retainers, transitional prosthesis, teeth, drilling templates, dental prosthesis (dentures), brackets, dental aligners, transfer splints (for positioning and bonding brackets), crowns, stabilization splints, bruxism splints, snoring splints, sports splints, bridges, temporary dentures, bleaching splints. In an embodiment, the dental product is in particular intended to be placed in the mouth of a person for a certain period of time (for instance overnight) and basically serves to protect and / or align the teeth of the wearer, for instance a protection against damages caused by grinding or gnashing. In accordance therewith, the dental product may in particular be selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner.

[0029] The dental product comprises (or is made from) a polymer comprising a functional group capable of forming a hydrogen bond. The dental product may in particular comprise at least 60 wt.-%, in particular at least 70 wt.-%, in particular at least 75 wt.-%, in particular at least 80 wt.-%, in particular at least 85 wt.-%, in particular at least 90 wt.-%, in particular at least 95 wt.-%, of the polymer comprising a functional group capable of forming a hydrogen bond.

[0030] The term “hydrogen bond”, as used herein, has the commonly accepted meaning in chemistry. The functional group capable of forming a hydrogen bond may in particular be capable of forming a hydrogen bond with water and / or an alcohol so that initial hydrogen bonds between polymer chains may be broken or interrupted by the water and / or the alcohol so that the polymer chains are allowed to move more freely resulting in an increase in elongation at break.

[0031] In an embodiment, the functional group capable of forming a hydrogen bond may be part of the polymer backbone. Additionally or alternatively, the functional group capable of forming a hydrogen bond may be part of a substituent at the polymer backbone or grafted on the polymer backbone.

[0032] In an embodiment, the functional group capable of forming a hydrogen bond is already part of a monomer used for forming the polymer. In other words, the functional group capable of forming a hydrogen bond may already be present as such in a monomer used for forming the polymer. It might however also be possible that the functional group capable of forming a hydrogen bond is only formed in the course of polymerization, for instance by polymerizing appropriate monomers having functional groups that react to yield a functional group capable of forming a hydrogen bond.

[0033] In an embodiment, the functional group capable of forming a hydrogen bond is at least one of a urethane group (which may also be referred to as a carbamate group), a thiourethane group (which may also be referred to as a thiocarbamate group) and an amide group. These groups have proving particular suitable for allowing both printability of a respective resin composition and capability of forming a hydrogen bond with water and / or an alcohol such that the tensile properties are improved. Among them, a urethane group or a thiourethane group may be preferred.

[0034] The method of preparing a dental product comprises a step of printing a dental product from a resin composition (so as to obtain a printed dental product).

[0035] In an embodiment, the resin composition comprises at least one (monomer) compound comprising the functional group capable of forming a hydrogen bond. As discussed above, the functional group capable of forming a hydrogen bond may already be present as such in a monomer used for forming the polymer. In addition to the at least one monomer comprising the functional group capable of forming a hydrogen bond, the resin composition may or may not comprise at least one other monomer compound not comprising a functional group capable of forming a hydrogen bond. In case of a resin composition comprising at least one other monomer compound not comprising a functional group capable of forming a hydrogen bond, the resulting polymer is a copolymer wherein the density or amount of functional groups capable of forming a hydrogen bond can be easily adjusted by the ratio of monomers comprising a functional group capable of forming a hydrogen bond to monomers not comprising a functional group capable of forming a hydrogen bond. In case of a resin composition not comprising at least one other monomer compound not comprising a functional group capable of forming a hydrogen bond, a polymer can be obtained with a particularly high density or amount of functional groups capable of forming a hydrogen bond, whose tensile properties may therefore be influenced in a particularly pronounced manner by water and / or an alcohol.

[0036] In an embodiment, the resin composition comprises at least one (monomer) compound selected from the group consisting of a compound having at least one carboncarbon double bond, a compound having at least one terminal alkyne group, a compound having at least two thiol groups, a compound having at least two hydroxyl groups, a compound having at least two carboxyl groups, a compound having at least one hydroxyl group and at least one carboxyl group, a compound having at least two amine groups, a compound having at least one amine group and at least one carboxyl group, and a compound having at least two isocyanate groups (R-N=C=O). These monomers have proven particular suitable for allowing both printability of a respective resin composition and capability of forming or containing a functional group capable of forming a hydrogen bond with water and / or an alcohol such that the tensile properties are improved. For instance, a resin composition comprising a compound having at least one carboncarbon double bond and a compound having at least two thiol groups may undergo a thiolene reaction, which type of reaction is particularly suitable for stereolithography. A thiol-ene reaction is in particular advantageous in that it enables a high yield of conversion of monomers (i.e. resulting in low amount of residual monomers, which is in particular advantageous in terms of biocompatibility) and provides (photo)polymers exhibiting high ductility (which is an important characteristic for dental products). Similarly, a compound having at least one terminal alkyne group and a compound having at least two thiol groups may undergo a thiol-yne reaction, which type of reaction is also particularly suitable for stereolithography. Moreover, any one of a compound having at least one carbon-carbon double bond, a compound having at least one terminal alkyne group and a compound having at least two thiol groups may comprise a functional group capable of forming a hydrogen bond.

[0037] Moreover, a resin composition comprising a compound having at least two amine groups and a compound having at least two carboxyl groups or a resin composition comprising a compound having at least one amine group and at least one carboxyl group may in particular be suitable for forming polyamides. In this case, a functional group capable of forming a hydrogen bond does not need to be already present in a monomer, but a functional group capable of forming a hydrogen bond, more specifically an amide group, is formed upon polymerization of the monomers.

[0038] Likewise, a resin composition comprising a compound having at least two hydroxyl groups and a compound having at least two isocyanate groups may in particular be suitable for forming polyurethanes. In this case again, a functional group capable of forming a hydrogen bond does not need to be already present in a monomer, but a functional group capable of forming a hydrogen bond, more specifically a urethane or carbamate group, is formed upon polymerization of the monomers.

[0039] Similarily, a resin composition comprising a compound having at least two thiol groups and a compound having at least two isocyanate groups may in particular be suitable for forming polythiourethanes. In this case again, a functional group capable of forming a hydrogen bond does not need to be already present in a monomer, but a functional group capable of forming a hydrogen bond, more specifically a thiourethane or thiocarbamate group, is formed upon polymerization of the monomers. In an embodiment, the resin composition comprises at least one (monomer) compound comprising at least one functional group selected from the group consisting of a vinyl group, an allyl group, a methallyl group, an acryl(ate) group and a methacryl (ate) group. These monomer compounds are all compounds having at least one carbon-carbon double bond and my undergo a thiol-ene reaction with a compound having at least two thiol groups, which type of reaction is particularly suitable for stereolithography. A thiol-ene reaction is in particular advantageous in that it enables a high yield of conversion of monomers (i.e. resulting in low amount of residual monomers, which is in particular advantageous in terms of biocompatibility) and provides (photo)polymers exhibiting high ductility (which is an important characteristic for dental products). Moreover, these monomer compounds may all further comprise a functional group capable of forming a hydrogen bond, such as a urethane group, a thiourethane group and / or an amide group, which may as such become part of the polymer backbone after polymerization. The terms “vinyl”, “allyl”, “methallyl”, “acrylate” and “methacrylate” as used herein, correspond to the generally accepted meanings thereof. A vinyl may be represented by the general formula “H2C=CH- ”, an allyl may be represented by the general formula “H2C=CH-CH2-”, a methallyl may be represented by the general formula „H2C=C(CH3)-CH2-“, an acrylate may be represented by the general formula “H2C=CH-C(=O)-O-” and a methacrylate may be represented by the general formula “H2C=C(CH3)-C(=O)-O-”. A “(meth)acrylate” may encompass an acrylate and / or a methacrylate.

[0040] In an embodiment, the printing step is carried out by means of a three-dimensional printing method. The term “three-dimensional printing method”, as used herein, in particular denotes that the (dental) product of the printing method extends in three directions (for example, length, width and height). Thus, the product of a three-dimensional printing method may be in particular a three-dimensional object. The three-dimensional printing method may be in particular any one selected from the group consisting of stereolithography (SLA), two-photon absorption (TPA) polymerization, digital light processing (DLP), masked stereolithography, reactive laser sintering (RLS), solid ground curing (SGC), multi jet modeling (MJM) or a combination thereof. In view of its high resolution, stereolithography (SLA) may be preferred.

[0041] In an embodiment, the printing step comprises irradiating at least a part of the resin composition with an energy-carrying activation beam (which may also be referred to as an irradiation step or a curing step) so as to cause polymerization of the at least a part of the resin composition. By irradiating at least a part of the resin composition with an energy- carrying activation beam, a chemical reaction may be caused at the irradiated part of the resin composition (for instance a thiol-ene reaction in case of resin composition comprising a compound having at least one carbon-carbon double bond and a compound having at least two thiol groups) with the result that the monomers undergo a cross-linking or polymerization reaction at the irradiated part and consequently a polymer is formed at the irradiated part of the resin composition. The polymer thus formed may also be referred to as a photopolymer. The energy-carrying activation beam may in particular comprise electromagnetic radiation (in particular actinic radiation). In particular, the energy-carrying activation beam may be at least one selected from the group consisting of ultraviolet radiation (such as having a wavelength of from 10 to 380 nm, in particular from 200 to 380 nm, in particular from 250 to 380 nm) and visible light radiation (such as having a wavelength of from 380 to 780 nm).

[0042] In an embodiment, the printing step further comprises a step of heating the resin composition. This might be advantageous for instance if the viscosity of the resin composition is high, so that the viscosity of the resin composition may be lowered by heating, which may facilitate the printing process. For instance, the resin composition may be heated to a temperature within the range of from 40 °C to 120 °C, such as 50 °C to 100 °C.

[0043] In an embodiment, the printing step further comprises a step of rinsing the polymer, in particular during and / or after irradiating the at least part of the resin composition. For instance, the polymer may be rinsed by means of an alcohol, such as isopropanol. By taking this measure, the amount of residual monomers in the printed polymer may be lowered.

[0044] In an embodiment, the printing step further comprises a step of post-curing the polymer, in particular after irradiating the at least part of the resin composition and / or after a step of rinsing. Thus, the printing step may comprise, in particular after an irradiation step and / or a rinsing step, a step of post-curing, wherein the initially formed polymer is further or again provided with actinic energy. For instance, in case of stereolithography, the (initially) formed polymer may be further or again irradiated with ultraviolet radiation in a post-curing step. The post-curing may in particular carried out at an elevated temperature, for instance in a range of from 30 to 80 °C.

[0045] The method of preparing a dental product further comprises a step of subjecting the (printed) dental product in accordance with at least one of the following two embodiments: In an embodiment, the (printed) dental product is stored (placed, put) in water and / or an alcohol for at least 30 seconds, in particular for at least 1 minute, in particular for at least 5 minutes, in particular for at least 10 minutes, in particular for at least 15 minutes, and at a temperature of at least 50°C, in particular at least 60°C, in particular at least 70°C, in particular at least 80°C, in particular at least 90 °C, in particular at least 100 °C. It is also possible to store the (printed) dental product under elevated pressure (for instance under at least 1.5 bar, in particular at least 2 bar, in particular at least 3 bar, such as by means of a pressure cooker), which may allow temperatures exceeding 100 °C and thus shorter storage times. Thus, in this embodiment, the dental product is subjected to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) at a high temperature and for a relatively short period of time. By taking this measure, the tensile properties or ductility of the dental product may not only be improved within a short period of time, but also the microbial load of the dental product and / or the amount of residual monomers in the dental product may be significantly reduced by dissolution, which is particular advantageous in terms of biocompatibility of the dental product in view of its intended application site within a person's mouth.

[0046] In an additional or alternative embodiment, the (printed) dental product is stored at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %, and / or in an aqueous and / or alcoholic solution (e.g. water and / or an alcohol) for at least 24 hours, in particular for at least 48 hours, in particular for at least 72 hours, in particular for at least 7 days, for instance at a temperature of at least 10 °C, in particular at least 15 °C, in particular at least 20 °C, in particular at least 25 °C. Thus, in this embodiment, the dental product is subjected to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) for a certain (relatively long) period of time, but an elevated temperature is not required. Rather, the storage may be accomplished at room temperature for instance. The term “relative humidity”, as used herein, may include water vapor, alcoholic vapor and mixtures of water vapor and alcohol vapour. The relative humidity may be determined in accordance with ISO / TR 18931 :2001.

[0047] In an embodiment, the storing step comprises storing (placing, putting) the (printed) dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, and / or storing the (printed) dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution (water and / or an alcohol) for at least 7 days. These storing conditions have proven to be particularly effective for improving the ductility of the dental product. Advantageously, both storing conditions are combined, for instance storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, followed by storing the dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution for at least 7 days, optionally followed by another storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C.

[0048] In an embodiment, the storing may take place in a mixture of water (or an aqueous solution) and one or more alcohols (or an alcoholic solution). For instance, a ratio (by volume) of alcohol to water may be in the range of 1 :99 to 99:1 , in particular 2:98 to 98:2, in particular 5:95 to 95:5, in particular 10:90 to 90:10, in particular 15:85 to 85:15, in particular 20:80 to 80:20, in particular 25:75 to 75:25, in particular 30:70 to 70:30, in particular 40:60 to 60:40, in particular about 50:50.

[0049] In an embodiment, the alcohol and / or the alcoholic solution comprises an aliphatic alcohol. Suitable examples thereof include methanol, ethanol, 1-propanol, 2-propanol (isopropanol, isopropyl alcohol), 1-butanol, 2-butanol (sec-butanol), 2-methyl- 1-propanol (iso-butanol), glycol (ethylene glycol), diethylene glycol, propane-1 ,2-diol (propylene glycol), glycerol and combinations thereof. Among them, ethanol and 2-propanol may be preferred from the viewpoint of biocompatibility. In addition, these and other alcohols further exhibit disinfecting properties, which is advantageous in view of the intended application site of the dental product within a person's mouth where contamination of the dental product with any undesired or harmful microorganisms is to be avoided.

[0050] In an embodiment, the aqueous and / or alcoholic solution further comprises a biocide (biocidal agent). The term “biocide”, which may also be referred to as “biocidal agent”, “disinfecting agent” or “antimicrobial agent”, as used herein, may in particular denote a compound or mixture of compounds having an inhibitory (or antagonistic) effect on the growth of microorganisms, that is, compounds that are capable of at least reducing the growth rate (e.g. bacteriostatic agents with respect to controlling the growth of bacteria and / or virostatic agents with respect to controlling the replication of viruses) as well as compounds that cause toxic effects with regard to microorganisms (e.g. bactericide agents killing bacteria and / or virucide agents killing viruses). In particular in case of storing the dental product in an aqueous solution for a relatively long period of time and / or at room temperature, the presence of a biocide in the aqueous solution is advantageous to prevent microbial contamination of the dental product, all the more as the dental product is intended to be placed in the mouth of a person where contamination of the dental product with any undesired or harmful microorganisms is to be avoided. In case of an alcoholic solution, the alcohol may itself exhibit disinfecting properties, but the additional presence of a biocide may nevertheless be advantageous. Of course, prior to placing the dental product in the mouth, it is advantageous to rinse the dental product with for instance (pure) water so as to substantially remove any attached biocides. Suitable examples of the biocide include chlorhexidine (1 ,6-bis(4-chloro-phenylbiguanido)hexane), triclosan (2,4,4'-Trichloro-2 - hydroxydi phenyl ether), a quaternary compound, such as a quaternary ammonium compound and / or a quaternary phosphonium compound, as well as combinations thereof.

[0051] In a second aspect, the present invention relates to a (three-dimensional) dental product obtainable (or obtained) by the method of the first aspect. The dental product may in particular be selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner. The dental product may in particular exhibit improved tensile properties, an increased ductility, and / or an increased elongation at break compared with a dental product that has not been prepared by a method of the first aspect, in particular where the dental product has not been subjected to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) at a high temperature and for a relatively short period of time and / or to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) for a certain (relatively long) period of time, as exemplified in detail above.

[0052] In a third aspect, the present invention relates to an arrangement, which may also be referred to as a package.

[0053] The arrangement comprises a (three-dimensional) dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond. The dental product may in particular be selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner. Further details about the dental product as well as about the polymer comprising a functional group capable of forming a hydrogen bond can be found above with regard to the first aspect. In particular, the functional group capable of forming a hydrogen bond may be at least one of a urethane (carbamate) group, a thiourethane (thiocarbamate) group and an amide group. Moreover, the dental product may be prepared by an additive manufacturing method, for instance the dental product may be a printed dental product. In particular, the (three-dimensional) dental product may be a (three-dimensional) dental product according to the second aspect.

[0054] The arrangement further comprises a wrapping (packaging) enclosing (in particular sealing) the (three-dimensional) dental product. The term “wrapping”, which may also be referred to as “packaging”, “enclosure” or “envelope”, as used herein, may in particular denote an element or a group of elements that is capable of (substantially) completely surrounding or enclosing the (three-dimensional) dental product, preferably in a (substantially) water-tight and / or gas-tight manner. To this end, the wrapping may comprise or may be formed from a material having a very low water (and / or alcohol) permeability and / or gas permeability.

[0055] A relative humidity within the wrapping is at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %. In other words, the dental product is kept within the wrapping at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %. By taking this measure, the tensile properties or ductility of the dental product may be improved over time, for instance during storage and / or transportation, as explained in further detail above. If the tensile properties or ductility of the dental product have already been improved in advance before enclosing the dental product by the wrapping, for instance by subjecting the dental product to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) at a high temperature and for a relatively short period of time, as exemplified above, the (high) relative humidity within the wrapping at least maintains tensile properties or ductility at a high level or may even further improve the same. Moreover, a drying-out of the dental product and a potential deterioration of the tensile properties or ductility associated therewith may be substantially avoided by the (high) relative humidity within the wrapping.

[0056] To ensure a (high) relative humidity, as defined above, the dental product may be arranged (placed, put, stored) in water and / or an alcohol or an aqueous and / or alcoholic solution. The aqueous and / or alcoholic solution may further comprise a biocide (biocidal agent) to prevent microbial contamination of the dental product over time, for instance during (long-term) storage, as further exemplified in detail above.

[0057] Additionally or alternatively, a water and / or alcohol reservoir may be further enclosed within the wrapping to ensure a (high) relative humidity. For instance, a sponge or a fleece impregnated with water and / or an alcohol may be placed within the wrapping. By taking this measure, a (high) relative humidity may be maintained within the wrapping, for instance in case some water and / or alcohol is consumed or absorbed by the dental product in the course of improving its tensile properties or ductility, as exemplified in detail above, or in case the wrapping is not completely water- and gas-tight. The water and / or alcohol reservoir, such as a sponge or a fleece, may also contain an aqueous and / or alcoholic solution further comprising a biocide so as to avoid any undesired microbial load.

[0058] In an embodiment, the wrapping comprises aluminum, which has proven to be particularly suitable for maintaining the (high) relative humidity, in particular in view of its very low water (and / or alcohol) permeability and / or gas permeability. For instance, the wrapping may be embodied as a zipper bag comprising aluminum, which is advantageous in terms of ease of use and convenience, in addition to its advantageous very low water and / or gas permeability characteristics.

[0059] In a fourth aspect, the present invention relates to a method of treating a dental product. The dental product may in particular be a three-dimensional dental product, such as a 3D-printed dental product. The method of treating may in particular result in a dental product having improved tensile properties, an increased ductility, and / or an increased elongation at break compared with a dental product where the process step of subjecting the dental product has been omitted. Thus, the method of treating a dental product may represent a method for increasing the ductility, for improving tensile properties and / or for increasing the elongation at break of a dental product.

[0060] The dental product to be treated comprises a polymer comprising a functional group capable of forming a hydrogen bond. The dental product may in particular be selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner. Further details about the dental product as well as about the polymer comprising a functional group capable of forming a hydrogen bond can be found above with regard to the first aspect. In particular, the functional group capable of forming a hydrogen bond may be at least one of a urethane (carbamate) group, a thiourethane (thiocarbamate) group and an amide group. Moreover, the dental product may be prepared by an additive manufacturing method, for instance the dental product may be a printed dental product.

[0061] The method of treating comprises a step of subjecting the dental product in accordance with at least one of the following two embodiments: In an embodiment, the dental product is stored (placed, put) in water and / or an alcohol for at least 30 seconds, in particular for at least 1 minute, in particular for at least 5 minutes, in particular for at least 10 minutes, in particular for at least 15 minutes, and at a temperature of at least 50°C, in particular at least 60°C, in particular at least 70°C, in particular at least 80°C, in particular at least 90 °C, in particular at least 100 °C. Thus, in this embodiment, the dental product is subjected to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) at a high temperature and for a relatively short period of time. By taking this measure, the tensile properties or ductility of the dental product may not only be improved within a short period of time, but also the microbial load of the dental product and / or the amount of residual monomers in the dental product may be significantly reduced, which is particular advantageous in terms of biocompatibility of the dental product in view of its intended application site within a person's mouth.

[0062] In an additional or alternative embodiment, the dental product is stored at a relative humidity of at least 60 %, in particular at least 70 %, in particular at least 80 %, in particular at least 90 %, in particular 100 %, and / or in an aqueous and / or alcoholic solution (e.g. water and / or an alcohol) for at least 24 hours, in particular for at least 48 hours, in particular for at least 72 hours, in particular for at least 7 days, for instance at a temperature of at least 10 °C, in particular at least 15 °C, in particular at least 20 °C, in particular at least 25 °C. Thus, in this embodiment, the dental product is subjected to water and / or an alcohol or a high humidity atmosphere (or an atmosphere with high concentrations of alcoholic vapor) for a certain (relatively long) period of time, but an elevated temperature is not required. Rather, the storage may be accomplished at room temperature for instance.

[0063] In an embodiment, the storing step comprises storing (placing, putting) the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, and / or storing the dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution (such as water and / or an alcohol) for at least 7 days. These storing conditions have proven to be particularly effective for improving the ductility of the dental product. Advantageously, both storing conditions are combined, for instance storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, followed by storing the dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution for at least 7 days, optionally followed by another storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C.

[0064] In an embodiment, after the dental product has been subjected as defined in the foregoing and after the dental product has been stored at a relative humidity of less than 60 %, in particular less than 50 %, in particular less than 40 %, in particular less than 30 %, which may lead to a drying out of the dental product and, associated therewith, a deterioration of the tensile properties or ductility, the dental product is again (once more) subjected to at least one of the following procedures: (i) storing the dental product in water and / or an alcohol for at least 30 seconds at a temperature of at least 50°C, and / or (ii) storing the dental product at a relative humidity of at least 60 % and / or in an aqueous and / or alcoholic solution for at least 24 hours. By taking this measure, any interim deterioration of the tensile properties or ductility of the dental product may be reversed. In other words, the dental product (even if dried out in the interim) may be reactivated by subjecting the same to any one of (i) or (ii) so that the tensile properties or ductility may be increased again. This finding is very important because it obviates the need for a continuous storage at high humidity (or high concentrations of alcoholic vapor) from the place of manufacturing the dental product to the final user. Moreover, such reactivating treatment may be repeated several times.

[0065] In an embodiment, the alcohol and / or the alcoholic solution comprises an aliphatic alcohol. Suitable examples thereof include methanol, ethanol, 1-propanol, 2-propanol (isopropanol, isopropyl alcohol), 1-butanol, 2-butanol (sec-butanol), 2-methyl- 1-propanol (iso-butanol), glycol (ethylene glycol), diethylene glycol, propane-1 ,2-diol (propylene glycol), glycerol and combinations thereof. Further details about the alcohol can be found above with regard to the first aspect.

[0066] In an embodiment, the aqueous and / or alcoholic solution further comprises a biocide (biocidal agent). Further details about the biocide can be found above with regard to the first aspect.

[0067] In a fifth aspect, the present invention relates to the use of water and / or an alcohol as a plasticizer for a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond. The present inventors have in particular found that water and / or an alcohol may be used to increase the ductility, improve tensile properties and / or increase the elongation at break of a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond. Thus, water and / or an alcohol may act as a plasticizer for such a dental product. As explained above and without wishing to be bound to any theory, the present inventors currently assume that the polymer material of the dental product may absorb or take up and bind water and / or the alcohol by means of the functional groups capable of forming a hydrogen bond. At the same time, initial hydrogen bonds between polymer chains may be broken or interrupted by the competing absorbed water and / or the alcohol so that the polymer chains are allowed to move more freely resulting in an increase in elongation at break. The present inventors have in particular found that these improved tensile properties may not only be achieved by a harsh treatment at high temperature, but also under ambient temperature over time. Thus, water and / or an alcohol may be used in different ways as a plasticizer for a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond.

[0068] In an embodiment, a mixture of water and one or more alcohols may be used as a plasticizer for a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond. Thus, water and and an alcohol may be used in combination, which may involve additional effects, for instance a disinfecting effect by the alcohol.

[0069] In an embodiment, a ratio (by volume) of alcohol to water may be in the range of 1 :99 to 99:1 , in particular 2:98 to 98:2, in particular 5:95 to 95:5, in particular 10:90 to 90:10, in particular 15:85 to 85:15, in particular 20:80 to 80:20, in particular 25:75 to 75:25, in particular 30:70 to 70:30, in particular 40:60 to 60:40, in particular about 50:50.

[0070] In an embodiment, the alcohol comprises an aliphatic alcohol. Suitable examples thereof include methanol, ethanol, 1-propanol, 2-propanol (isopropanol, isopropyl alcohol), 1 -butanol, 2-butanol (sec-butanol), 2-methyl-1 -propanol (iso-butanol), glycol (ethylene glycol), diethylene glycol, propane-1 , 2-diol (propylene glycol), glycerol and combinations thereof. Among them, ethanol and 2-propanol may be preferred from the viewpoint of biocompatibility. In addition, these and other alcohols further exhibit disinfecting properties, which is advantageous in view of the intended application site of the dental product within a person's mouth where contamination of the dental product with any undesired or harmful microorganisms is to be avoided. Moreover, the alcohol may dissolve residual monomers and thereby reduce the amount of residual monomers in the dental product, which is also advantageous in terms of biocompatibility of the dental product in view of its intended application site within a person's mouth The dental product may in particular be selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner. Further details about the dental product as well as about the polymer comprising a functional group capable of forming a hydrogen bond can be found above with regard to the first aspect. In particular, the functional group capable of forming a hydrogen bond may be at least one of a urethane (carbamate) group, a thiourethane (thiocarbamate) group and an amide group. Moreover, the dental product may be prepared by an additive manufacturing method, for instance the dental product may be a printed dental product. In particular, the dental product may be a three-dimensional printed dental product.

[0071] The present invention is further described by the following examples, which are solely for the purpose of illustrating specific embodiments, and are not construed as limiting the scope of the invention in any way.

[0072] Examples

[0073] A photopolymer, i.e. a polymer which has been cured by irradiation with light, more specifically a thiol / ene methacrylate photopolymer, has been subjected to different conditions of exposure to water or alcohol, more specifically isopropanol and / or relative humidity (RH) at different temperatures and for different periods of time. The tensile properties, more specifically the Young's modulus (E modulus) and the elongation at break (tensile strength at break), of the photopolymer after each subjection have been determined in accordance with DIN EN ISO 527-1. The results are summarized in the following Table 1.

[0074] [Table 1]

[0075]

[0076] The following conclusions can be drawn from the above results:

[0077] The E modulus is reduced after exposure to water at 100 °C for 15 min — > water acts as a plasticizer

[0078] The elongation at break is significantly increased after exposure to water at 100 °C for 15 min.

[0079] The E modulus is also reduced and the elongation at break is also increased after exposure to isopropanol at 50 °C for 15 min. Thus, isopropanol has proven a similar effect as water, even though to a lesser extent which is presumably basically due to the lower temperature.

[0080] The elongation at break is reduced after storage at 30% RH for 7 days due to (i) aging of the photopolymer (in case of the photopolymer with or without previous exposure to water) and (ii) drying-out (in case of the photopolymer with previous exposure to water).

[0081] - After storage at 100% RH for 7 days, the elongation at break is increased (in case of the photopolymer without previous exposure to water) or is reduced to a minor extent compared with 30% RH for 7 days (in case of the photopolymer with previous exposure to water).

[0082] The difference in elongation at break (46.9% vs. 30.5%) after storage at 100% RH for 7 days is due to a dissolution of residual monomers (which may also act as a plasticizer) by the exposure to water at 100 °C. However, even if the elongation at break is inferior, the biocompatibility of the photopolymer is enhanced. In another experiment, it could be demonstrated that a reduced elongation at break after storage at 30% RH for 7 days due to drying out of a photopolymer previously exposed to water at 100 °C can be increased again by another exposure to water and / or an alcohol at 100 °C and / or for 7 days. Thus, even in case a photopolymer is dried out at a certain period of time, its tensile properties may be reactivated or increased again by exposure to water and / or an alcohol under the specific conditions defined herein. As mentioned above, this finding is very important because it obviates the need for a continuous storage of the dental product at high humidity or an atmosphere with high concentrations of alcoholic vapor (similar to an “uninterrupted humid chain”, in analogy to an uninterrupted cold chain required for deep-frozen food) from the place of manufacturing the dental product to the final user.

[0083] While the present invention has been described in detail by way of specific embodiments and examples, the invention is not limited thereto and various alterations and modifications are possible, without departing from the scope of the invention.

Claims

CLAIMS1. A method of preparing a dental product, the dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, the method comprising the steps of: printing a dental product from a resin composition; followed by subjecting the dental product to at least one of the following procedures: storing the dental product in water and / or an alcohol for at least 30 seconds at a temperature of at least 50°C, and / or storing the dental product at a relative humidity of at least 60 % and / or in an aqueous and / or alcoholic solution for at least 24 hours.

2. The method according to claim 1 , wherein the dental product is selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner.

3. The method according to claim 1 or 2, wherein the functional group capable of forming a hydrogen bond is at least one of a urethane group, a thiourethane group and an amide group.

4. The method according to any one of the preceding claims, wherein the resin composition comprises at least one compound comprising the functional group capable of forming a hydrogen bond.

5. The method according to any one of the preceding claims, wherein the resin composition comprises at least one compound selected from the group consisting of a compound having at least one carbon-carbon double bond, a compound having at least one terminal alkyne group, a compound having at least two thiol groups, a compound having at least two hydroxyl groups, a compound having at least two carboxyl groups, a compound having at least one hydroxyl group and at least one carboxyl group, a compound having at least two amine groups, a compound having at least one amine group and at least one carboxyl group, and a compound having at least two isocyanate groups,6. The method according to any one of the preceding claims, wherein the resin composition comprises at least one compound comprising at least one functional groupselected from the group consisting of a vinyl group, an allyl group, a methallyl group, an acryl group and a methacryl group.

7. The method according to any one of the preceding claims, wherein the printing step is carried out by means of a three-dimensional printing method, in particular stereolithography.

8. The method according to any one of the preceding claims, wherein the printing step comprises irradiating at least a part of the resin composition with an energy-carrying activation beam so as to cause polymerization of the at least a part of the resin composition.

9. The method according to any one of the preceding claims, wherein the printing step further comprises a step of heating the resin composition.

10. The method according to any one of the preceding claims, wherein the printing step further comprises a step of post-curing the polymer, in particular during and / or after irradiating the at least part of the resin composition.

11. The method according to any one of the preceding claims, wherein the storing step comprises storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, and / or storing the dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution for at least 7 days.

12. The method according to any one of the preceding claims, wherein the alcohol and / or the alcoholic solution comprises an aliphatic alcohol, in particular selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2- methyl-1-propanol, glycol, diethylene glycol, propane-1 , 2-diol and glycerol.

13. The method according to any one of the preceding claims, wherein the aqueous and / or alcoholic solution further comprises a biocide, in particular selected from the group consisting of chlorhexidine, triclosan, and a quaternary compound, such as a quaternary ammonium compound and / or a quaternary phosphonium compound.

14. A dental product obtainable by the method according to any one of claims 1 to 13.

15. An arrangement comprising:a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, in particular a dental product of claim 14; a wrapping enclosing the dental product, wherein a relative humidity within the wrapping is at least 60 %.

16. The arrangement according to claim 15, wherein at least one of the following features applies: the dental product is selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner; the functional group capable of forming a hydrogen bond is at least one of a urethane group, a thiourethane group and an amide group; and / or the dental product is arranged in an aqueous and / or alcoholic solution, optionally further comprising a biocide.

17. The arrangement according to claim 15 or 16, wherein a water and / or alcohol reservoir, such as a sponge or a fleece impregnated with water and / or an alcohol, is further enclosed within the wrapping.

18. The arrangement according to any one of claims 15 to 17, wherein the wrapping comprises aluminum, in particular a zipper bag comprising aluminum.

19. A method of treating a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond, the method comprising: subjecting the dental product to at least one of the following procedures: storing the dental product in water and / or an alcohol for at least 30 seconds at a temperature of at least 50°C, and / or storing the dental product at a relative humidity of at least 60 % and / or in an aqueous and / or alcoholic solution for at least 24 hours.

20. The method according to claim 19, wherein the dental product after having been subjected as defined in claim 19, and after having been stored at a relative humidity of less than 60 %, the dental product is again subjected to at least one of the following procedures: storing the dental product in water and / or an alcohol for at least 30 seconds at a temperature of at least 50°C, and / or storing the dental product at a relative humidity of at least 60 % and / or in an aqueous and / or alcoholic solution for at least 24 hours.

21. The method according to claim 19 or 20, wherein at least one of the following features applies: the dental product is selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner; the functional group capable of forming a hydrogen bond is at least one of a urethane group, a thiourethane group and an amide group; the storing comprises storing the dental product in water and / or an alcohol for at least 15 minutes at a temperature of at least 100 °C, and / or storing the dental product at a relative humidity of 100 % and / or in an aqueous and / or alcoholic solution for at least 7 days; the alcohol and / or the alcoholic solution comprises an aliphatic alcohol, in particular selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1 -propanol, glycol, diethylene glycol, propane-1 , 2-diol and glycerol; and / or the aqueous and / or alcoholic solution further comprises a biocide.

22. Use of water and / or an alcohol as a plasticizer for a dental product comprising a polymer comprising a functional group capable of forming a hydrogen bond.

23. The use according to claim 22, wherein at least one of the following features applies: the alcohol is an aliphatic alcohol, in particular selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, glycol, diethylene glycol, propane-1 , 2-diol and glycerol; the dental product is selected from the group consisting of a splint, in particular an occlusal splint, a night guard, and a dental aligner; and / or the functional group capable of forming a hydrogen bond is at least one of a urethane group, a thiourethane group and an amide group.

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