Patent Description:
Many individuals have teeth that need to be straightened. Braces have been used to align or move the teeth. Brackets are connected by wires. Aligners on the other hand are a series of tight-fitting custom-made mouthpieces that slip over the teeth. Invisalign is the largest producer of clear aligners, but it's not the only brand. Others include Clear Correct, Inman Aligner, and Smart Moves.

The initial hours or days of wearing currently available plastic dental aligners (e.g. like Invisalign™) can be painful and uncomfortable for the patient. These aligners are purposely designed to exert relatively high levels of force on the teeth - so the aligners are often stiff and thick which also makes them difficult and painful to insert on the teeth. Patients go through this initial pain and discomfort many times during the teeth-straightening process because these processes involve the sequential use of several aligners - for example, <NUM> aligners over <NUM> months. Furthermore, discomfort and pain prompt many patients to remove the aligner more frequently, thus adding weeks or months to the treatment time. If one aligner step does not bring the patient fully to the next step in their sequence, a costly intervention called a "mid-course correction" is required to continue the prescribed alignment therapy.

The discomfort, pain and inefficiency come as a result of the plastic constructions currently used in the aligners. These have traditionally relied on hard, stiff plastics to provide the physical properties (primarily force) required for effective alignment. Traditional plastic constructions also exhibit suboptimal force creep - i.e., the force exerted by the aligner declines very rapidly as the polymer creeps early after insertion, particularly over the initial <NUM> hours. This creep reduces the effective force available to move the teeth through the remainder of that retainer sequence. Therefore, each retainer must be more aggressively designed to compensate for loss of force due to creep yet still remain effective in moving teeth. The materials used in these aligners offer limited force and creep design control. For the patient, this translates into higher pain and discomfort (particularly during the first hour or so of use), and it often results in the need for several visits to the dentist.

<CIT> discloses an orthodontic appliance for promoting development of a dental arch form in a patient who has an underdeveloped dental arch form. The appliance includes an arch-shaped base member that is made of a resiliently flexible material, and a teeth engaging member that encloses at least part of the base member. The teeth engaging member defines upper and/or lower dental arch receiving channels and is made of a resiliently flexible material that is softer than the base member and is deformable. The appliance has a resting form in which the resilient materials of the base member and the teeth engaging member are in their resting condition. The appliance can be flexed or deformed out of the resting form to fit the underdeveloped dental arch form into the dental arch receiving channel. When deformed the appliance exerts a return force that is directed to returning it to its resting form which in use urges the underdeveloped dental arch to expand into a developed dental arch form.

<CIT> discloses improved dental appliances and polymeric sheet compositions. The polymeric sheet compositions are useful for making dental appliances having outer layers comprised of a material having a modulus of from about <NUM>,<NUM> MPA to <NUM>,<NUM> MPA ("hard") and an inner core comprised of elastomeric material or materials having a modulus of from about <NUM> MPa to <NUM> MPa ("soft"), which exhibit improved flexibility and strength, and better stain and tear resistance than currently available materials and dental appliances.

Given the foregoing limitations there is an unmet need for dental aligners which address the shortcomings of the existing dental aligners. Keeping the foregoing need in mind, the instant invention provides a dental aligner that can be better tuned to deliver a specific and more stable (lower creep) force on the teeth while also being softer and thinner. Such an aligner would create a better experience for patients and give the medical practitioner greater control to customize the treatment based on a patient's therapeutic stage, discreet requirements, and pain tolerance. Using a retainer construction with a tunable force and creep profile can create a treatment process that likely results in better compliance, fewer mid-course corrections, less pain, and ultimately better treatment outcomes.

The invention provides a dental aligner comprising multiple layers of material, selected from a core or inner layer, and skin or outer layers wherein, the core layer has a hard/strong component made using a plastic material having a Rockwell R hardness greater than about <NUM> and less than about <NUM>, and is selected from polyethylene terephthalate glycol (PETG), rigid thermoplastic polyurethane (r-TPU), polysulfone, and combinations thereof; and the skin layers comprise a soft polymer having a Shore hardness from about 50A to about 60D, and is selected from thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof, wherein, the skin or outer layers make up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner.

Provided in a further preferred embodiment is a dental aligner wherein the outer soft layer makes up from about <NUM> % to about <NUM> % of the total thickness of the dental aligner.

A preferred embodiment provides a dental aligner having a total thickness of from about <NUM> to about <NUM>.

Another preferred embodiment provides a dental aligner wherein the dental aligner has a modulus ranging from about 1379Mpa (about <NUM>,<NUM> psi) but less than about 3347Mpa (about <NUM>,<NUM> psi) and applies an initial force ranging from about <NUM> (about <NUM> lbs) to about <NUM> (about <NUM> lbs).

Another embodiment of this aspect of the invention provides a dental aligner wherein incorporated within the plastic material are active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment(s). A preferred embodiment of this aspect provides a dental aligner wherein the plastic materials, over a period of time, release active ingredients and/or therapeutic compositions such as pain relief medicines, anti-bacterial agents, teeth whitening agents, or other agents that enhance dental treatment(s).

Another preferred embodiment provides a dental aligner wherein the dental aligner has a modulus of about 1379Mpa (about <NUM>,000psi) and less than about 3347Mpa (about <NUM>,000psi) and applies an initial force of about <NUM> (about <NUM> lbs) but less than about <NUM> (about <NUM> lbs).

Another embodiment of this aspect of the invention provides a dental aligner wherein incorporated within the outer soft layer are active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment(s). A preferred embodiment of this aspect provides a dental aligner wherein the outer soft layer, over a period of time, releases active ingredients and/or therapeutic compositions such as pain relief medicines, anti-bacterial agents, teeth whitening agents, or other agents that enhance dental treatment(s).

Provided in yet another preferred aspect of the present invention is a dental aligner of wherein, the soft/skin layer has a hard/core layer sandwiched between two soft plastic layers, wherein the thickness of the hard/core layer is about <NUM> and the thickness of each of the soft/skin layers is about <NUM>.

A dental aligner of the invention comprises multiple layers of material, selected from a core or inner layer, and skin or outer layers wherein, the core layer has a hard/strong component made using a plastic material having a Rockwell R hardness greater than about <NUM> and less than about <NUM>, and is selected from polyethylene terephthalate glycol (PETG), rigid thermoplastic polyurethane (r-TPU), polysulfone, and combinations thereof; and the skin layers comprise a soft polymer having a Shore hardness from about 50A to about 60D, and is selected from thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof, wherein, the soft/skin layer makes up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner. Another preferred embodiment provides a dental aligner wherein, the soft/skin layer makes up from about <NUM> % to about <NUM> % of the total thickness of the dental aligner. Yet another preferred embodiment provides a dental aligner of wherein, the core layer has a hard/strong component made using a plastic material having a Rockwell R hardness greater than about <NUM> and less than about <NUM>, and the soft/skin layer has a Shore hardness greater than about 50A and less than about 60D.

A further preferred embodiment provides a dental aligner wherein, the dental aligner has a modulus of about 1379Mpa (about <NUM>,000psi) but less than about 3347Mpa (about <NUM>,000psi), and applies an initial force of about <NUM> (about <NUM> lbs) but less than about <NUM> (about <NUM> lbs). Yet another further preferred embodiment provides a dental aligner wherein, the soft/skin layer has a hard/core layer sandwiched between two soft plastic layers, wherein the thickness of the hard/core layer is about <NUM> and the thickness of each of the soft/skin layers is about <NUM>.

Another embodiment provides a dental aligner wherein the dental aligner material comprises active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment. Another preferred embodiment provides a dental aligner wherein the dental aligner material, over a period of time, releases active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and other agents that enhance dental treatment.

Also described is a dental aligner comprising a mono layer consisting of a thermoplastic material having a Rockwell R hardness of greater than about <NUM> and less than about <NUM>, and wherein the thermoplastic material is selected from a family of homo and co-polymers of polysulfone and blends thereof.

A preferred embodiment of this aspect of the instant invention provides a dental aligner wherein the thermoplastic material having a total thickness of from about <NUM> to about <NUM>; and the thermoplastic homo and co-polymers of polysulfone has a modulus of elasticity from about 1379Mpa (about <NUM>,<NUM> psi) but less than about 3347Mpa (about <NUM>,<NUM> psi). Yet another preferred aspect provides a dental aligner wherein the thermoplastic homo and co-polymers of polysulfone has an elongation at break from about <NUM>% but less than <NUM>%; and wherein the mono layer based on the homo and co-polymers of polysulfone is at least <NUM>% better in stress relaxation than thermoplastic urethane and polyethylene terephthalate glycol in <NUM>% stress-relaxation test at room temperature for <NUM> hrs. Another preferred aspect provides a dental aligner wherein the mono layer based on the homo and co-polymers of polysulfone further comprises at least <NUM> wt% but less than <NUM> wt% of a bluing dye material.

Also described is a dental aligner comprising an outer layer and an inner layer, wherein the outer layer is hard and comprises a thermoplastic material having a Rockwell R hardness of greater than about <NUM> and less than about <NUM>, and wherein the thermoplastic material is selected from a family of polyethylene terephthalate glycol (PETG), rigid thermoplastic polyurethane (r-TPU), polysulfone, and combinations thereof; and the inner layer against the tooth is softer than the outer layer and consists of a thermoplastic material having a Shore hardness from about 50A to about 60D , and a thermoplastic material is selected from thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof.

Also described is a dental aligner wherein, the inner soft layer makes up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner; and wherein the inner soft layer makes up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner. Yet another preferred embodiment provides a dental aligner wherein, the dental aligner has a modulus of about 1379Mpa (about <NUM>,000psi) and less than about 3347Mpa (about <NUM>,000psi) and applies an initial force of about <NUM> (about <NUM> lbs) but less than about <NUM> (about <NUM> lbs). A preferred embodiment provides a dental aligner wherein the dental aligner material comprises active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment. Another preferred embodiment provides a dental aligner wherein the dental aligner material, over a period of time, releases active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and other agents that enhance dental treatment.

A dental aligner of the invention comprises multiple layers of materials, selected from a core or inner layer, and skin or outer layers wherein the core layer has a rigid thermoplastic material having a Rockwell R hardness of greater than about <NUM> and less than about <NUM>, and wherein the thermoplastic material is selected from a family of homo and co-polymers of polysulfone and blends thereof; and the skin layers comprise a soft thermoplastic polymer having a Shore hardness from about 50A to about 60D, and a thermoplastic material is selected from is thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof, wherein, the outer soft/skin layer makes up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner. Another preferred embodiment provides a dental aligner wherein, the soft/skin layer makes up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner. Yet another preferred embodiment provides a dental aligner wherein, the core layer has a rigid thermoplastic material having a Rockwell R hardness of greater than about <NUM> and less than about <NUM>, and the soft/skin layer has a Shore hardness greater than about 55A and less than about 60D. Yet another preferred embodiment provides a dental aligner wherein, the soft/skin layer has a hard/core layer sandwiched between two soft plastic layers, wherein the thickness of the hard/core layer is about <NUM> and the thickness of each of the soft/skin layers is about <NUM>.

A further preferred embodiment provides a dental aligner wherein the dental aligner material comprises active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment. Another preferred embodiment provides a dental aligner wherein the dental aligner material, over a period of time, releases active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and other agents that enhance dental treatment.

Yet in another aspect, which is not part of the invention, a dental aligner is provided comprising multiple layers of materials, selected from a core or inner layer, and skin or outer layers wherein: the core layer has a soft thermoplastic polymer having a Shore hardness from about 50A to about 60D, and a thermoplastic material is selected from is thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof; and the skin layers comprise a rigid thermoplastic material having a Rockwell R hardness of greater than about <NUM> and less than about <NUM>, and wherein the thermoplastic material is selected from a family of homo and co-polymers of polysulfone and blends thereof.

A preferred embodiment provides a dental aligner wherein the dental aligner material comprises active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and agents that enhance dental treatment. Another preferred embodiment provides a dental aligner wherein the dental aligner material, over a period of time, releases active ingredients and/or therapeutic compositions selected from pain relief medicines, anti-bacterial agents, teeth whitening agents, and other agents that enhance dental treatment.

The description, in one of its aspects, provides a dental aligner wherein the dental aligner is softer than the traditional dental aligner having a Shore D hardness of greater than <NUM> (><NUM>). In one embodiment of this aspect is provided a dental aligner that is softer than a traditional aligner capable of tuning the force applied on the teeth as required by the treatment regimen and a patient's tolerance for pain. In another embodiment is provided a dental aligner wherein the creep is minimized to improve the malocclusion treatment (i.e., the force applied by the material on the teeth is more uniform, especially during the initial <NUM> hours of wearing the aligner). A preferred embodiment of this aspect of the invention provides a dental aligner that is thinner than a traditional dental aligner, and further offers a lower coefficient of friction for easier insertion and removal from the teeth while still effectively gripping the teeth to apply corrective force.

The present invention provides dental aligners that utilize particular polymers or combination of polymers and thicknesses to achieve a desired force profile and to minimize creep - for example, the polymers are polysulfones alone or a combination of polyesters. The polyester blended materials are softer and could be used alone as a 'single layer' aligner, in an embodiment which is not an object of the invention, or combined with an outer elastomeric layer of TPU, PETG, or another co-polymer or terpolymer. The instant dental aligners include materials, in particular the softer materials, with the ability to incorporate slow-release capabilities. The slow release aspect enables the release/delivery of active ingredients and/or therapeutic compositions such as pain relief medicines, anti-bacterial agents, teeth whitening agents, or other agents that enhance dental treatment(s).

Also described is a single or mono layer dental aligner, which is not an object of the present invention, comprising a "comfort plastic" made by a single layer extrusion process or through additive manufacturing (3D printing). This single or mono layer dental aligner consists of materials selected from neat polymers or blends of relatively hard, strong TPU, PETG, PC, polysulfone, or all hard-segment, rigid TPU, and soft materials selected from neat polymers or blends of soft thermoplastic elastomeric urethanes, elastomeric polyesters, polyamides, styrenic block co-polymers, TPVs, EMAs, EBAs, and other TPEs, or TPOs. The soft component content of the dental aligner ranges from about <NUM>% to about <NUM>% of the total material of the dental aligner.

Another embodiment of this aspect provides a dental aligner consisting of material with a Shore Hardness of about 50D to about R100 and modulus of about > 1379Mpa (about <NUM>,000psi) to about less than 3347Mpa (<NUM>,000psi) and an initial force of about > <NUM> (about <NUM> lbs) and less than about <NUM> (about <NUM> lbs) at a total thickness of the aligner of about <NUM> mil. A further preferred embodiment provides a dental aligner consisting of material with a Shore Hardness of about 70D to about R100 and a force of about <NUM> (about <NUM> lbs) to about <NUM> (about <NUM> lbs).

The hard component will be the "working" part of the formula that moves the teeth while the soft component provides the softer, more compliant comfort aspect and more effective force transmission of the plastic to the teeth.

Also described is a dental aligner comprising two layers of comfort plastic. One embodiment of this aspect provides a dental aligner comprising an inner or base layer made of a strong, hard plastic such as PETG, PC, polysulfone, TPU and the like that provides the "working" part of the plastic sheet that moves the teeth. The skin or the outer layer comprises a soft polymer such as TPU, TPE, elastomeric co-polyester, EMA, EBA and the like that provides a layer of comfort from the hard, base layer and ability to conform to the tooth surface contour effectively gripping and transferring tooth movement forces.

Another embodiment, which is not an object of the present invention, of this aspect provides a dental aligner wherein the soft skin layer comprises about <NUM>% to about <NUM>% of the total thickness of the dental aligner. Yet another embodiment provides a dental aligner with a Shore hardness of the soft skin layer ranging from about 40A to about 50D. A further preferred embodiment, which is not an object of the present invention, provides a dental aligner consisting of material with a Shore Hardness of about 70D to about R100 and a force of about <NUM> (about <NUM> lbs) to about <NUM> (about <NUM> lbs).

Also described is a dental aligner with more than two layers of comfort plastic. One embodiment of this example provides a dental aligner comprising a core or inner layer consisting of a strong, hard plastic such as PETG, PC, polysulfone, TPU and others that provides the "working" part of the plastic sheet that moves the teeth. The outer or skin of this embodiment comprise a soft polymer such as TPU, TPE, elastomeric co-polyester, EMA, EBA and others that provides layers of comfort and force transmission from the hard, base layer.

This example presents a dental aligner, which is not an embodiment of the present invention, wherein the outer soft skin layers comprise about <NUM>% to about <NUM>% of the total thickness of the dental aligner. In another description is a dental aligner, which is not an embodiment of the present invention, with a Shore hardness of the soft skin layer ranging from about 40A to about 50D. A further such example provides a dental aligner, which is not an embodiment of the present invention, consisting of material with a Shore Hardness of about 70D to about R100 and a force of about <NUM> (about <NUM> lbs) to about <NUM> (about <NUM> lbs).

Yet another embodiment of this aspect provides multiple "soft" layers that balance comfort, conformance to tooth contours, grip and comfort for tuning and optimizing the dental and/orthodontic therapy.

Yet another embodiment of this aspect provides a dental aligner with a multilayer construction using a "working" plastic as the hard skin layers and a core layer of soft plastic (potential chemistries described above. ) The core layer comprises from about <NUM>% to about <NUM>% of the total thickness.

As used herein, the term "Dental Aligner" represents orthodontic devices that are generally transparent, made of plastic and are used to adjust teeth. Clear or transparent aligners are an alternative to traditional braces and are designed to help guide teeth into their proper position. Similar to braces, clear aligners use a gradual force to control tooth movement, but without metal wires or brackets. The dental aligners have been traditionally made of a strong plastic material and are fabricated to fit each individual's mouth. If a series of aligners are needed, each aligner moves the teeth in increments until the desired movement is achieved. The dental aligners of the instant invention are made of a combination of soft and hard plastic material, as discussed in the present specification.

The term "plastic material" as used herein represents materials used to make dental aligners. One example of plastic material is an elastic thermoplastic which when used to make dental aligners helps apply pressure to the tooth/teeth to move the tooth in a desired position.

The term "shore hardness" as used herein is a measure of the resistance a material has to indentation. There are different Shore Hardness scales for measuring the hardness of different materials. These scales were invented so that people can discuss these materials and have a common point of reference. The Shore <NUM> Hardness Scale measures rubbers and gels that are very soft. The Shore A Hardness Scale measures the hardness of flexible mold rubbers that range in hardness from very soft and flexible, to medium and somewhat flexible, to hard with almost no flexibility at all. Semi-rigid plastics can also be measured on the high end of the Shore A Scale. The Shore D Hardness Scale measures the hardness of hard rubbers, semi-rigid plastics and hard plastics.

The term "total thickness" is intended to represent the thickness of a dental aligner including the soft and rigid layers taken together.

The term "modulus" as used herein represents the elastic modulus of a material or device defined as the slope of its stress-strain curve expressed in pounds per square inch (psi).

The term "outer/skin layer" represents the outer part of a dental aligner which is generally softer than the layer it encompasses and is the portion that is in direct contact with the teeth/tooth, and also the tongue and inner part of one's cheek.

The term "inner component" as used herein represents a generally harder/rigid material of a dental aligner. The inner component is generally completely encompassed within the outer generally softer layer. Illustrative example is as shown in <FIG> portion B.

The term "hard/strong component" as used herein represents the inner component described above. Illustrative examples of a hard/strong component are plastic materials having a shore hardness component greater than about 55D and less than about R100, and is selected from polyethylene terephthalate glycol (PETG), polysulfone, thermoplastic polyurethane (TPU), and combinations thereof.

The term "TPE" represents a thermoplastic elastomer. The term "TPU" represents a thermoplastic polyurethane. The term "EMA" as used herein represents Ethylene Methyl Acrylate Co-polymer. The term "EBA" as used herein represents Ethylene Butyl Acrylate Co-polymer. The term "TPV" represents a thermoplastic vulcanizate.

The term "initial force" as used herein represents the initial force in pounds (lbs) exerted on the teeth when a dental aligner is placed on top of the teeth. This initial force is proportional to the kind of materials used to construct a dental aligner.

The term "Pain Relief Medicines", as used herein, represents medicines that are administered to an individual to reduce bodily pain including headaches, sore muscles, arthritis, or other aches and pains. There are many different pain medicines, and each one has advantages and risks. Some types of pain respond better to certain medicines than others. Each person may also have a slightly different response to a pain reliever. Illustrative examples of pain relief medicines are over the counter (OTC) medicines such as acetaminophen (Tylenol). Another example of a pain relief medicine is nonsteroidal anti-inflammatory drugs (NSAIDs). Examples of NSAIDs are Aspirin, naproxen (Aleve), and ibuprofen (Advil, Motrin).

The term "Anti-bacterial Agents" as used herein represents a group of materials that fight against pathogenic bacteria. Thus, by killing or reducing the metabolic activity of bacteria, their pathogenic effect in the biological environments can be minimized. Furthermore, these materials can prevent bacterial plaque accumulation in the oral environment and therefore, can reduce the prevalence of plaque-related diseases such as caries. However, it should be noted that antibacterial agents do not necessarily possess antiplaque accumulation properties. Illustrative examples of anti-bacterial agents are amoxicillin, doxycycline, cephalexin, ciprofloxacin, clindamycin, metronidazole, and azithromycin.

The term "Teeth Whitening Agents" as used herein are used to make teeth look whiter. The materials remove stains or other discoloration from the tooth surface. Hydrogen peroxide is the active ingredient most commonly used in tooth whitening products and is delivered as either hydrogen peroxide or carbamide peroxide. Baking soda is reported to be a low abrasive, and effective stain removal and tooth whitening agent.

The term "thermoplastic material" as used herein represents a plastic polymer material that becomes moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate by intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. In this state, thermoplastics may be reshaped and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendaring, and extrusion. Thermoplastics differ from thermosetting polymers (or "thermosets"), which form irreversible chemical bonds during the curing process. Thermosets do not melt when heated, but typically decompose and do not reform upon cooling.

The term "Rockwell R hardness" as used herein represents the hardness of the material by measuring the depth of penetration of an indenter under a large load compared to the indentation made by a pre-load. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number. Indenters can be diamond tips, steel or Tungsten Carbide balls. The Rockwell testing procedures used in the Plastic Industry are ASTM D785 and ISO2039-<NUM> and are outlined in https://omnexus. specialchem. com/polymer-properties/properties/hardness-rockwell-m?src=omproperty&utm_source=selection-resources&utm_medium=polymer-properties&utm_campaign=hardness.

The term "homopolymers of polysulfone" (PSU) is intended to represent a family of high-performance thermoplastics containing an aryl-SO<NUM>-aryl subunit. These polymers are known for their toughness and stability at high temperatures. Three polysulfones are used industrially, these are polysulfone (PSU), polyether sulfone (PES) and polyphenylene sulfone (PPSU). They can be used in the temperature range from -<NUM> to +<NUM> and are used for electrical equipment, in vehicle construction and medical technology. [<NUM>] They are composed of para-linked aromatics, sulfonyl groups and ether groups and partly also alkyl groups. Polysulfones have outstanding resistance to heat and oxidation, hydrolysis resistance to aqueous and alkaline media and good electrical properties as outlined in https://en. org/wiki/Polysulfone.

Polysulfones used herein include those that are rigid and have a Rockwell R hardness of from about <NUM> to about <NUM>. Illustrative examples and sources for the same as provided below:.

The term "co-polymers of polysulfone" is intended to represent di-hydroxy terminated polysulfone with other oligomers (low molecular weight polymers) or polymers such as polyethylene glycol or polydimethylsiloxane materials as outlined in https://www. sciencedirect. com/science/article/abs/pii/S0142961205006058 and https://onlinelibrary. com/doi/abs/<NUM>/pol. <NUM>, just to mention a few.

The abbreviation "MPa" represents the megapascal is a x1000000 multiple of the pascal unit which is the SI unit for pressure or force. <NUM> megapascal equals <NUM>,<NUM>,<NUM> pascals or <NUM> psi as outlined in https://en. org/wiki/Pascal_(unit).

The term "elongation at break" is intended to represent the material property which is determined from the ratio between changed length and initial length after breakage of the test specimen in tensile testing. It expresses the capability of a material to resist changes of shape without crack formation as outlined in https://www. org/wiki/Property:P5811.

Dental aligners of the present invention comprise soft components/layers/skins and hard/rigid layers/components as described above. The following examples illustrate the different dental aligners.

The following example illustrates a dental aligner with three layers, a soft component with a thickness of about <NUM> and hard component with a thickness of about <NUM>. The two <NUM> soft layers are on the outside and are in contact with the tooth/teeth and with the inner part of the cheek and tongue. The two soft layers can be distinct from one another in that they are on the opposite side of the aligner (one in direct contact with the tooth/teeth and the other with direct contact with the inner part of the cheek and tongue). These soft layers can have different thickness and taken together they entirely encapsulate the hard/rigid layer.

For all of the following examples, "R100" = Rockwell Hardness R100.

The soft layers can range in thickness from about <NUM> to about <NUM> each.

This example varies from Example <NUM> in that here the hard/rigid layer encapsulates the soft layer and the two rigid layers can be distinct from one another in that they are on the opposite side of the aligner (one in direct contact with the tooth/teeth and the other with direct contact with the inner part of the cheek and tongue). Specifics of the hard/rigid and soft layer/components are as follows. The thickness of each layer in this example is about <NUM>.

The following example illustrates a dental aligner with two layers, a soft component with a thickness of about <NUM> and hard component with a thickness of about <NUM>, where the soft layer is in contact with the teeth.

The following example illustrates a dental aligner with a single or mono layer with a hard/rigid component with a thickness ranging from about <NUM> to about <NUM>.

The following example illustrates a multi-layer dental aligner made with three layers. The first layer is about <NUM> to <NUM> thick and comes in contact with the tooth when placed in the mouth. It is made with an amorphous, clear, rigid co-polyester and blends thereof with bluing dye agents in amount ranging from about <NUM>% to about <NUM>% by total weight. The second layer (core layer) is about <NUM> to about <NUM> thick and comprises at least <NUM> Shore A aromatic polyether based thermoplastic urethane (TPU), COPE (co-polyether-ester), olefin functional elastomer, styrene butadiene block co-polymer. The third layer (aka outer "tensile" skin) is about <NUM> to about <NUM> thick and comprises clear high temperature polymers and blends thereof - selected from Polysulfone (PSU, PES, and PPSU) along with bluing dye agents in amount ranging from about <NUM>% to about <NUM>% by total weight.

As shown below, the outer skin layers (i.e. one of the outer skin layer against tooth, the other skin layer in contact with cheek and tongue) are selected from soft materials having a Shore A of about <NUM> and selected from aromatic polyether based TPU or co-polyether ester or olefin functional elastomer and the inner layer (aka core) is selected from Polysulfone (PSU, PES, and PPSU) along with bluing dye agents in amount ranging from about <NUM>% to about <NUM>% by total weight.

As shown below, the multi-layer Dental aligner wherein the outer layer (aka "outer tensile" skin) is selected from a hard material based on homo and co-polymers of polysulfone and their blends along with bluing dye agents and the inner layer against the tooth is selected from soft materials having a Shore A of about <NUM> selected from aromatic polyether based TPU or co-polyether ester or olefin functional elastomer.

The dental aligners provide enhanced sustained force at lower thicknesses, as well as reduced polymer creep (or stress relaxation), on the tooth and thereby help lower the overall time required to move the teeth with less pain and may help reduce the need for mid-course corrections. In some cases, it may also reduce the overall number or retainers required for a particular treatment.

Illustrative examples of dental aligners comprising therapeutic agents are provided below:.

It is understood that one or more therapeutic agent(s) can be incorporated in any one or more of the multiple layers of the dental aligner.

Background: <NUM>% Stress-Relaxation test (RT for <NUM> hours) was performed on the following samples per Bixby's internal procedures. All samples were <NUM> thick unless noted otherwise.

Results: Force/load (lbf) values are reported at time intervals specified in the table below.

Table I: Table I lists the stress relaxation for dental aligners with mono layers PSU, TPU (control), PETG A, PETG B each <NUM> thick. Also included is a three layer aligner with soft skin layers 85A hardness and center core rigid layer PETG B; a mono layer aligner made of <NUM> PSU and <NUM> thick; a three layer aligner with rigid PSU skins and a soft 85A TPU core at <NUM>; a two layer aligner with a PSU base and a 85A TPU skin; and a commercially available aligner with hard skins and a soft core. The column with "<NUM>" is time zero showing the starting force at time zero and the loss in the force over a period of time at intervals of quarter hour, half hour, three fourth hour, <NUM>, <NUM>, <NUM>,. <NUM> hours.

Graph I: Graph I depicts the stress loss profile over time for each of the aligners in Table I. The initial stress is along the Y axis and the loss of the stress is represented going from left to right along the X axis.

Table II: Table II lists the stress relaxation for dental aligners with mono layers PSU, TPU (control), PETG A, PETG B each <NUM> thick. Also included is a three layer aligner with soft skin layers 85A hardness and center core rigid layer PETG B; a mono layer aligner made of PSU and <NUM> thick; a three layer aligner with rigid PSU skins and a soft 85A TPU core at <NUM>; a two layer aligner with a PSU base and a 85A TPU skin; and a commercially available aligner with hard skins and a soft core. The column with "<NUM>" is time zero showing the starting force at time zero and the loss in the force over a period of time at intervals of quarter hour, half hour, three fourth hour, <NUM>, <NUM>, <NUM>,. <NUM> hours.

Graph/Chart II: Graph/Chart II represents the retained stress for aligners listed in Table II. The aligner with the least stress loss is on the left.

Table III: Table III lists the area under the curve calculated after performing the <NUM>% stress relaxation test (<NUM> hours) for dental aligners with mono layers PSU, TPU (control), PETG A, PETG B each <NUM> thick. Also included is a three-layer aligner with soft skin layers 85A hardness and center core rigid layer PETG B; a mono layer aligner made of PSU and <NUM> thick; a three layer aligner with rigid PSU skins and a soft 85A TPU core at <NUM>; a two layer aligner with a PSU base and a 85A TPU skin; and a commercially available aligner with hard skins and a soft core. Larger values of area under the curve represents the greater work performed by the material & construction, or the cumulative amount of force over time applied to move teeth over <NUM> hours.

Claim 1:
A dental aligner comprising multiple layers of material, selected from a core layer (B), and skin layers (A1, A2) wherein:
the core layer (B) has a hard/strong component made using a plastic material having a Rockwell R hardness greater than about <NUM> and less than about <NUM>, and is selected from polyethylene terephthalate glycol (PETG), rigid thermoplastic polyurethane (r-TPU), polysulfone, and combinations thereof; and
the skin layers (A1, A2) comprise a soft polymer having a Shore hardness from about 50A to about 60D, and is selected from thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), thermoplastic vulcanizates (TPV), elastomeric co-poly(ether or ester-ester), elastomeric co-poly (ether or ester-amide), co-polymers of ethylene-methyl (EMA)or ethylene-butyl acrylate (EBA) and combinations thereof, wherein, the skin layers (A1, A2) make up from about <NUM>% to about <NUM> % of the total thickness of the dental aligner.