PROCESS FOR FABRICATING A DENTAL APPLIANCE AND ACCOMPANYING USE CASES

Abstract

For improving the functionality and bio-compatibility of dental appliances (2), a novel process is described for making a thermoplastic functional foil (1), from which such dental appliances (2) may be obtained by thermoforming the functional foil (1). A carrier liquid (9) containing an organic and preferably bio-based polymer (6) is enriched with an agent (7) and applied onto a solid thermoplastic core foil (13). After evaporating of a solvent contained in the carrier liquid (9), a uniform and highly homogenous functional coating (5) is obtained on the core foil (13). After thermoforming of the foil (1), the dental appliance (2) thus features an outer protective coating (5) offering enhanced functionality. Moreover, it is possible to reload the agent (7) into the coating (5) of the appliance (2) using a reload-liquid (23).

Claims

1. A process for making a thermoplastic functional foil (1) comprising a core (3) of thermoplastic material (4) and a thermoplastic coating (5) at least partially covering the core (3), the process comprises the following steps: providing a carrier liquid (9) comprising an organic polymer (6); adding an agent (7), releasable from the thermoplastic coating (5) in aqueous environment, to the carrier liquid (9) prior to forming the thermoplastic coating (5); and applying the carrier liquid (9) as the thermoplastic coating (5) onto the core (3).

2. The process according to claim 1, wherein the agent (7) is derived from a renewable biological resource comprising a material of non-fossil origin produced by a living organism.

3. The process according to claim 1, wherein the agent (7) comprises at least one of: an essential oil, an extract of an essential oil, cinnamaldehyde, lime, thymol, eugenol, linalool, carvacrol, nutmeg, pimenta berry, rosemary, petitgrain, coffee, or anise.

4. The process according to claim 1, wherein at least one of a) the organic polymer (6) is derived from a renewable biological resource, b) the organic polymer (6) is a cellulose-based material, or the organic polymer (6) is cellulose acetate butyrate (CAB).

5. The process according to claim 1, wherein the coating (5) provides antimicrobial protection.

6. The process according to claim 1, wherein a melting temperature T.sub.m,core of the core (3) and a melting temperature T.sub.m,coating of the coating (5) differ by at least 20° C.

7. The process according to claim 1, wherein the core (3) is made from Polyethylenterephthalat (PET).

8. The process according to claim 1, wherein the agent (7) comprises a combination of essential oils as follows: Limonene or cinnamaldehyde and methyl salicylate or trans-anethole;

9. The process according to claim 1, wherein a glass transition temperature T.sub.g,coating of the coating (5) is from 80-165° C., and at least one of a) a decomposition temperature T.sub.d,agent of the agent (7) is at least 10° C. above a melting temperature T.sub.m,coating of the coating (5), b) a corresponding melting range of the coating (5) is from 120-200° C., or c) the organic polymer (6) used for the coating (5) has a number average molecular weight of more than 12.000 g.

10. The process according to claim 1, wherein the carrier liquid (9) is a carrier solution (11), and the core (3) is a core foil (13).

11. The process according to claim 1, further comprising, forming the coating (5) by a physical coating process including at least one of spin coating, blade-based coating, spray coating, or by roll-to-roll coating.

12. The process according to claim 1, wherein a glass transition temperature T.sub.g,core of the core (3) and a glass transition temperature T.sub.g,coating of the coating (5) differ by less than 80° C.

13. The process according to claim 1, wherein the carrier liquid (9) is a carrier solution (11) obtained by dissolving the organic polymer (6) in a solvent (12), and at least one of a) the solvent (12) modifies a surface of the core (3) such that the core (3) and the coating (5) interlock on a nanometer scale, resulting in improved adhesion of the coating (5) on the core (3), or b) the solvent (12) comprises at least one of acetone, methyl acetate, ethyl acetate, methylethyl ketone, isopropyl acetate, butyl acetate, ethyl lactate, cyclohexane, diacetone alcohol, butyl lactate or suitable mixtures thereof.

14. The process according to claim 1, wherein the agent (7) is a liquid or the agent (7) is added to the carrier liquid (9) by dissolving or emulsifying the agent (7) in an aqueous or oil-based solution and mixing the solution with the carrier liquid (9).

15. The process according to claim 1, wherein a ratio between the agent (7) and the organic polymer (6) is between 0.01/99.99 and 30/70 by weight.

16. The process according to claim 1, further comprising forming a dental appliance (2) from the thermoplastic functional foil (1) by thermoforming the foil (1) after application of the coating (5) to the core (3), after thermoforming, the organic polymer (6) forms a conformal functional coating (5), and the agent (7) embedded in the coating (5) provides antimicrobial or regenerative functionality for teeth and gingiva or a flavor to the dental appliance (2).

17. A dental appliance (2), comprising: the thermoplastic functional foil (1) fabricated with the process according to claim 1, wherein the dental appliance (2) consists entirely of the foil (1) or the dental appliance is 3D-printed from a liquid precursor comprising an organic polymer and loaded with a releasable agent (7).

18. A dental appliance (2), comprising: a core (3) of thermoplastic material (4), a thermoplastic coating (5) at least partially covering the core (3), and an agent (7) embedded in the coating (5) and releasable from the coating (5) in aqueous environment.

19. A method for non-therapeutic protecting of at least one of teeth or gingiva from gingivitis and/or parodontitis, the method comprising: covering both teeth and parts of the gingiva adjoining to the teeth with the dental appliance according to claim 18, wherein the dental appliance (2) provides antimicrobial protection through the agent comprising a releasable antimicrobial agent (7).

20. A method for loading or re-loading a dental appliance (2) with a releasable agent (7), the method comprising: providing a reload-liquid that contains the agent (7), and immersing the dental appliance (2) in the reload-liquid to load the agent (7) into the dental appliance (2).

21. The method according to claim 20, wherein the reload-liquid (23) is an aqueous solution containing a solvent or an oil-based liquid.

22. The method according to claim 21, wherein the reload-liquid (23) is obtained by dissolving a solid tablet (25) containing the agent (7) in a liquid.

23. The method according to claim 22, wherein at least one of the reload-liquid (23) or the tablet (25) comprises a surfactant for homogenously distributing the agent (7) within the reload-liquid (23).

24. The method according to claim 23, wherein at least one of a) a concentration of the surfactant c.sub.s in the reload-liquid (23) is c.sub.s>1.1 g/l, or b) a ratio of a concentration c.sub.s of the surfactant and a concentration c.sub.a of the agent (7) in the reload-liquid (23) is c.sub.s/c.sub.a<100.

25. The method according to claim 24, wherein the agent (7) is at least one of an antimicrobial agent (7), derived from a renewable biological resource, a combination of the following essential oils: Limonene or cinnamaldehyde and methyl salicylate or trans-anethole.

26. A method for initially loading a dental appliance (2) with a releasable agent (7), the method comprising: embedding the releasable agent (7) in a thermoplastic coating (5) of the dental appliance (2) by immersing the dental appliance (2) in a reload-liquid (23) that contains the releasable agent (7), thereby loading the releasable agent (7) into the thermoplastic coating (5); or embedding the releasable agent (7) in a 3d-printed body of the dental appliance (2) by immersing the dental appliance (2) in a reload-liquid (23) that contains the releasable agent (7), thereby loading the releasable agent (7) into the 3d-printed body.

27. The dental appliance of claim 17, wherein the releasable agent (7) is at least one of: a) releasable from the dental appliance (2) during intra-oral use, or b) reloadable into a cap layer of the dental appliance (2) using a reload-liquid (23).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] With reference to the accompanying drawings, where features with corresponding technical function are referenced with same numerals even when these features differ in shape or design

[0081] FIG. 1 is a schematic overview of a fabrication process according to the invention,

[0082] FIG. 2 illustrates the definition of non-fossil carbon content and bio-based content used herein to describe bio-based materials,

[0083] FIG. 3 schematically illustrates a method for loading an agent into a dental appliance using a reload-liquid according to the invention,

[0084] FIG. 4 shows measurement data of concentrations of a particular agent loaded into different thermoplastic materials, and

[0085] FIG. 5 depicts further experimental data of calorimetric measurements.

DETAILED DESCRIPTION

[0086] FIG. 1 provides an overview of a fabrication process according to the invention: An organic polymer 6, namely cellulose acetate butyrate (CAB), is dissolved in a solvent 12, namely acetone, to form a carrier solution 11. The carrier solution 11 is next mixed with an agent liquid 8 containing cinnamaldehyde, which is a bio-based antimicrobial agent 7, to form a carrier liquid 9, in which the agent 7 and the CAB are homogenously mixed. This carrier liquid 9 is then applied by clip coating onto a core foil 13 of a thermoplastic material 4. After evaporation of the solvent 12, a solid thermoplastic coating 5 is obtained on both sides of the core-foil 13, which thus completely covers the core 3 of the resulting functional foil 1 (c.f. the cross-section visible in FIG. 1).

[0087] The foil 1, in fact, constitutes a multi-layer structure with a core 3 made from glykol modified Polyethylenterephthalat (PETG) with a thickness of 200 μm and top and bottom functional coatings 5 which each have a thickness (after solidification) of less than 20 μm, thus resulting in a total thickness of the thermoplastic functional foil 1 of less than 250 μm.

[0088] As a next step, using a 3D-model of an oral cavity of a patient, a pre-form 15 is formed from the functional foil 1 by thermoforming, applying heat 14 from both sides to the foil 1 and thus distorting the core 3 and the coatings 5 together in one step. In other words, the coating 5 is already firmly linked to the core 3 prior to thermoforming. The underlying reason is that the acetone 12 modifies the surface of the PETG core 3 leading to a softening of the PETG surface such that the CAB molecules 6 can interlock on a nanometer scale at the interface 17 (cf. FIG. 1) with the PETG of the core 3. As a result, there is already a high adhesion of the coating 5 on the core 3 prior to thermoforming.

[0089] As the glass transition temperatures T.sub.g,core of the PETG-core 3 and T.sub.g,coating of the coating differ by less than 60° C., during thermoforming the adhesion of the coating 5 on the core foil 13 is further improved, as a thermal interlocking is achieved through thermal fusion of the CAB-coating 5 with the PETG.

[0090] Finally the pre-form 15 is cut such that the resulting dental appliance 2 visible on the bottom left of FIG. 1 covers both teeth and adjoining parts of the gingiva. As visible, the dental appliance 2 further features multiple cavities 16 designed for taking up single teeth and which are matching the natural positions of the teeth of the user. Thus, the user experiences no forces on his teeth when wearing the dental appliance 2 on his teeth. As the appliance 2 is very thin, highly conformable and offers a soft and highly deformable functional coating 5, which, due to the CAB used, even softens when getting into contact with saliva and offers antimicrobial protection due to the embedded cinnamaldehyde, the appliance 2 is ideally suited to be worn overnight or while smoking, even for hours. In such non-therapeutic use-cases, the user can benefit from the protection provided by the appliance 2 against cigarette smoke, as the appliance 2 is impermeable to smoke, but also from gingivitis and parodontitis, due to the antimicrobial effect that is produced when the cinnamaldehyde 7 is slowly released from the coating 5 into the oral cavity of the user.

[0091] The CAB used for the coating 5 encapsulating the core 3 as illustrated on the right of FIG. 1 is in fact a bio-based material 10, as it is produced by blending organic materials derived from fossil sources with organic material, in particular cellulose, derived from non-fossil natural sources such as plants. Therefore, the complete outer surface 18 of the appliance 2 is formed from bio-based materials 10. Any mechanical abrasion from this surface 18 will thus not be harmful for the user wearing the appliance 2 in his mouth.

[0092] Likewise, the agent 7 embedded in the coating 5 can be derived from natural sources such as essential oils extracted directly from non-fossil plants. This allows use of agents such as lime, thymol, eugenol, linalool, carvacrol, nutmeg, pimenta berry, rosemary, petitgrain, coffee, anise, to name a few. Hence the appliance 2 can deliver both flavor and antimicrobial protection and still be highly biocompatible and non-harmful to wear.

[0093] As FIG. 2 illustrates schematically, “bio-based material” as understood herein may mean that the organic polymer 6 as well as the agent 7 used for the coating 5 may contain a significant portion of non-fossil carbon content 19, for example at least 40%. This non-fossil carbon content 19 is characterized in that it contains the carbon isotope 14C in a detectable fraction (e.g. more than 10 ppq or even more than 100 ppq). There may also be a fossil carbon content 20 (cf. FIG. 4), which is based on fossil sources and containing the isotope .sup.12C but no detectable fraction of .sup.14C any more, as the .sup.14C has been diminished by radioactive decay over thousands of years. As illustrated in FIG. 4, there can be defined a further quantity namely the so-called bio-based content 21. This fraction of the material 5 comprises the non-fossil carbon content 19 as well as all hydrogen H-, oxygen O-, and nitrogen N-atoms 22 bound to the non-fossil carbon content 19.

[0094] FIG. 3 illustrates the formation and use of a reload-liquid as proposed herein: In a first step, a highly concentrated liquid precursor 24 containing the agent 7 and a surfactant are first dispensed in water using a low-cost pipette 26; alternatively, a tab 25 containing the agent 7 and a surfactant may be dissolved in the water. By both ways, a reload-liquid 23 may be formed. In a second step, the reload-liquid 23 is shaken to allow thorough mixing of the liquid precursor 24 with the water and/or full dissolving of the tab 24 in the water. In a third step, the dental appliance 2 is immersed and soaked in the formed reload-liquid 23 for a duration of 15-30 minutes. Finally, in a fourth step, the dental appliance 2 is taken out of the reload-liquid 23 and is now loaded with the agent 7 and ready for use in the mouth, where the agent 7 can be released from the dental appliance 2, for example for producing a pleasant taste and/or an antimicrobial effect.

[0095] FIG. 4 displays experimental data obtained by first loading four different thermoplastic materials with an agent 7 (cinnamaldehyde) by immersing the respective thermoplastic material in a reload-liquid 23 (comprising 12 g of a surfactant and 0.56 g of the agent 7 dissolved in 100 ml of water) for a time period of 60 min, respectively. Afterwards, the materials were immersed repeatedly in fresh ethanol-solution, which was used as an extraction medium for extracting the agent 7 from the materials, and the concentration of the agent 7 in the respective ethanol-solution was measured each time. In other words, at different points in time, fresh ethanol-solutions were used for extracting the agent from the respective thermoplastic material. The graph displays the measured concentration of the agent 7 in the respective solution for each material for an extraction time of 0.7 h, 7 h, and 70 h, respectively.

[0096] As the graph shows (note the logarithmic scale on both axes!), the proposed material system (upper two symbols), comprising a cellulose-based cap layer (materials NA750 and NA550, respectively) applied onto a core of a thermoplastic material, can initially load more of the agent 7 from the same reload-liquid 23 and additionally can store the agent 7 for a much longer period of time (thus offering a lower release rate of the agent 7 over time), as compared to a poly-urethane (PU) based thermofoil (Zendura) or a pure PETG-based thermofoil (both without any coating). In bare numbers, the approach according to the invention allows for an increase in release rate by a factor of 2 . . . 6 after a reload time of only 60 minutes; the period of time during which a significant release of the agent is maintained (and thus the desired anti-microbial functionality of the dental appliance) is extended by about six times. The uptake of the cellulose-based cap layers is at least a factor of 2 . . . 4 higher, as compared to the pure core materials PETG and PU.

[0097] FIG. 5 displays experimental data obtained in a second experiment in which dental appliances according to the invention, each time comprising a cellulose-based cap layer, was loaded with 7 different types of agents 7 for time periods ranging from 10 to 1440 min (=24 h). The graph shows the concentration of each agent 7 in 40% ethanol-water-solution, which was used as an extraction medium over a period of 24 hours. Depending on the chemical side group (in particular its polarity) of the particular agent, the capacity to interact with the dental appliance (through storage and release) can vary by a factor of up to 10000, as can be seen by comparing the data for Carvacrol and Cinnamaldehyde. As a result, Cinnamaldehyde appears as an agent that is particularly suited for the applications described herein.

[0098] Finally, additional calorimetric experiments were performed to measure the capability of different agents of suppressing the growth of bacteria such as Streptococcus mutans and Streptococcus mitis. The different agents 7 were applied as a solution containing a single essential oil component at a concentration of 0.1% in BHI. As figure of merits, the lag phase, defined as the postponement in time of the growth of the bacteria and measured in hours, and the growth rate (increase in number of bacteria/time), measured in J/h, of the Streptococcus populations were determined as follows:

TABLE-US-00001 growth rate lag phase (h) of S. agent (J/h) of S. mutans mutans growth Limonene 0 >24 cinnam aldehyde 0 >24 trans-anethole 0.03 >24 methyl salicylate 1.2  5 Eucalyptol 1.3  5

TABLE-US-00002 growth rate lag phase (h) of S. agent (J/h) of S. mitis mitis growth methyl salicylate 0.4 23 trans-anethole 0.13  6.4 cinnam aldehyde 0.15  6.2 Limonene 0.11  3 Eucalyptol 0.14  2

[0099] As can be seen from these data, in particular Limonene and cinnamaldehyde produce lag phases exceeding 24 hours without any measurable growth w.r.t. Streptococcus mutans. With respect to Streptococcus mitis, methyl salicylate offers the best protection due to a lag phase of 23 hours at a moderate growth rate of 0.4 J/h.

[0100] In addition, the difference between non-polar and polar agents should be noted here, since the polarity of the agent 7 will define the reload speed into the cellulose-based (e.g. CAB) coating of the dental appliance 2 as well as the extraction speed in the saliva of the patient. Furthermore the polarities of the agents 5 impact their respective interaction when combined together in one reload-liquid 23 and thus influence the reload speed of each single agent 7, depending on the ratio to each other and the ratio to the surfactant (if present in the reload-liquid 23).

[0101] As cinnamaldehyde is polar, while limonene and methyl salicylate are non-polar, cinnamaldehyde is particularly suited as an anti-microbial agent 7 to be used with a material system as proposed herein with a cellulose-based cap layer, because cinnamaldehyde offers similar anti-microbial protection but superior reload speed.

[0102] For achieving best protection against both Streptococcus mutans and Streptococcus mitis, a combination of Limonene or cinnamaldehyde and methyl salicylate or trans-anethole is proposed to be used as the agent 7 in the reload-liquid 23 described previously and thus as the antimicrobial agent 7 to be delivered by the dental appliance 2 to the user.

[0103] In summary, for improving the functionality and bio-compatibility of dental appliances 2, a novel process is proposed for making a thermoplastic functional foil 1, from which such dental appliances 2 may be obtained by thermoforming the functional foil 1. A carrier liquid 9 containing an organic and preferably bio-based polymer 6 is enriched with an agent 7 and applied onto a solid thermoplastic core foil 13. After evaporating of a solvent 12 contained in the carrier liquid 9, a uniform and highly homogenous functional coating 5 is obtained on the core foil 13. After thermoforming of the foil 1, the dental appliance 2 thus features an outer protective coating 5 offering enhanced functionality (c.f. FIG. 1). Moreover, it is possible to reload the agent 7 into the coating 5 of the appliance 2 using a reload-liquid.

LIST OF REFERENCE NUMERALS

[0104] 1 thermoplastic functional foil [0105] 2 dental appliance [0106] 3 core [0107] 4 thermoplastic material [0108] 5 thermoplastic coating [0109] 6 organic polymer [0110] 7 agent [0111] 8 agent liquid [0112] 9 carrier liquid [0113] 10 bio-based material [0114] 11 carrier solution [0115] 12 solvent [0116] 13 core foil [0117] 14 heat applied [0118] 15 pre-form [0119] 16 cavities (for taking up single teeth) [0120] 17 interface [0121] 18 outer surface [0122] 19 non-fossil carbon content (containing .sup.14C) [0123] 20 carbon content based on fossil sources (containing no detectable [0124] fraction of .sup.14C any more) [0125] 21 bio based content (i.e. non-fossil carbon content plus hydrogen, [0126] nitrogen, and oxygen bound to this content) [0127] 22 hydrogen, nitrogen, and oxygen bound to non-fossil carbon [0128] 23 reload-liquid [0129] 24 liquid precursor [0130] 25 tablet [0131] 26 pipette