GB2618519A

GB2618519A - A method of manufacturing an orthodontic aligner and a system for manufacturing an orthodontic aligner

Info

Publication number: GB2618519A
Application number: GB2204669.2A
Authority: GB
Inventors: Georges Young Philippe; Smigaj Wojciech
Original assignee: Vitaware Ltd
Current assignee: Vitaware Ltd
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-11-15
Anticipated expiration: 2042-03-31
Also published as: GB202204669D0; GB2618519B

Abstract

A method of manufacturing an orthodontic aligner which includes gathering a digital representation of an initial arrangement of at least a subset of adjacent teeth of a patient’s jaw and manufacturing the orthodontic aligner which covers the subset of teeth. The method includes (a) gathering a digital representation of an initial arrangement of a least one subset of adjacent teeth of a patient’s jaw; (b) preparing a treatment plan which comprises at least one arrangement for the or each subset of teeth; and (c) producing the orthodontic aligner based on the subset of adjacent teeth for the at least one arrangement. The aligner covers only a subset of teeth to provide a more comfortable aligner which may be cheaper given a reduction in material and manufacture time compared to a full aligner. Also disclosed is a system for manufacturing an orthodontic aligner. The aligner may be moulded around a 3d printed mould or directly 3d printed.

Description

A method of manufacturing an orthodontic aligner and a system for manufacturing an orthodontic aligner

FIELD OF THE INVENTION

The invention relates to a method of manufacturing an orthodontic aligner, which comprises gathering a digital representation of an initial arrangement of teeth of a patient's jaw, preparing a treatment plan, preparing a mould, and forming the orthodontic aligner over the mould.

The invention further relates to a system for manufacturing an orthodontic aligner which comprises an imaging device, a processing device, and a manufacturing device.

BACKGROUND TO THE INVENTION

Clear aligners are orthodontic devices that are a transparent, plastic form of dental braces used to adjust the posture (position and/or the orientation) of teeth.

Treatment using aligners usually begins with capturing the patient's bite, teeth, and gums via a bite registration and physical impressions (e.c. polyvinyl siloxane impressions) or an Intra-oral digital scanner. Due to improvements of digital scanning technology, the latter method has greatly increased in popularity. Dental impressions are scanned in order to create a digital 3D representation of the teeth. The targeted teeth (i.e. the teeth to be moved using the aligner) are moved in the digital representation to the desired posture. Six or more aligners may be needed as each aligner moves teeth 0.23 to 0.33 millimetres.

The objective of the invention is to provide improved orthodontic aligners.

SUMMARY OF THE INVENTION

The technical objective is solved by the subject matter of the independent claims. Optional embodiments of the invention are defined in the dependent claims.

At its most general, the present invention relates to manufacturing an orthodontic aligner which includes gathering a digital representation of an initial arrangement of at least a subset of adjacent teeth of a patient's jaw and manufacturing the orthodontic aligner which covers the subset of teeth.

A method for manufacturing an orthodontic aligner comprises steps a), b), and c). Step a) relates to gathering a digital representation of an initial arrangement of a least a subset of adjacent teeth of a patient's jaw. Step b) relates to preparing a treatment plan which comprises at least one arrangement for the subset of teeth. The treatment plan is for moving one or more of targeted teeth teased from the subset of teeth from the initial arrangement towards a final arrangement. Step c) includes producing the orthodontic aligner based on the subset of adjacent teeth for the at least one arrangement. The aligner covers (only) the subset of teeth.

In an optional embodiment, step c) includes steps cl) and/or c2). Step cl) includes preparing a mould associated with at least a subset of adjacent teeth for the at least one arrangement. Step c2) comprises forming the orthodontic aligner over the mould. The aligner covers the subset of teeth.

A system for manufacturing and orthodontic aligner comprises an imaging device, a processing device, and a manufacturing device. The imaging device is configured to image at least a subset of adjacent teeth of a patient's jaw and/or a cast of the subset of adjacent teeth of the patient's jaw. The processing device is electronically coupled to the imaging device. The processing device is configured to generate a digital representation of an initial arrangement of the subset of teeth. The processing device is further configured to prepare a treatment plan which comprises at least one arrangement of the subset of teeth. The treatment plan is for moving one or more targeted teeth of the subset of teeth from the initial arrangement towards a final arrangement. The manufacturing device is electronically coupled to the processing device. The manufacturing device is further configured to prepare a mould associated with at least the subset of adjacent teeth for the at least one arrangement. Alternatively or additionally, the manufacturing device is configured to directly produce the orthodontic aligner The orthodontic aligner can be a clear aligner which may include a transparent, plastic form of dental braces used to adjust the posture (position and/or the orientation) of the targeted teeth. The orthodontic aligner may be free of metal parts and/or may be removable from the teeth. In other words, the orthodontic aligner may be worn during certain periods of a day (for example during night) and removed during other time periods of a day (for example when eating). Usage of the orthodontic aligner of this invention may be similar to the usage of commonly known clear aligners.

The difference of the aligner of this invention compared to commonly known clear aligners is that the aligner of this invention can be regarded a partial aligner which covers only the subset of teeth whereas commonly known clear aligners are designed to fit over the dentition of the whole mandible and/or maxilla (lower and/or upper jaw dentition) right to the back molars. This requires impressions to be obtained for the whole dentition (either using intra-oral digital scanners or physical impressions) and these are then used as the basis for digital treatment planning; that is defining target dentition (desired final postures (positions and/or orientation) of all the teeth) and the different intermediate stages/steps to progressively move teeth towards this target.

The aligner of this invention covers not all teeth of a patient's jaw, but only a subset of teeth. For example, the number of targeted teeth (the teeth to be moved by the aligner) is smaller than the number of the subset of teeth which, in turn, is smaller than the number of all teeth in a patient's jaw.

Some of the possible advantages of this invention's partial aligner approach are: The partial aligner may be more comfortable to wear which may result in greater acceptance by the patient. It can be expected that by covering only a portion of the full dental arch/teeth (i.e. a subset of teeth), the aligners will be somewhat less intrusive to the patient. Where motion of only the back teeth is desired and the aligners cover only the molars and pre-molars, the aligners will be hardly visible and presumably will impact speech to a lesser degree.

The partial aligner may be cheaper to manufacture. A not insignificant portion of the total costs of providing aligners is the cost of manufacturing the aligners themselves based on the digital treatment plan moulds/models. This may involve the 3D printer time to manufacture the moulds, the 3D printer material costs, the cost of the discs/sheets of aligner material used to vacu/thermo form the aligners onto the moulds and the time/costs of manually or automatically trimming the aligners. Aligners with eight or ten front teeth have a substantially reduced platform and volume compared to full arch aligners (with regard to the required mould) which can lead to significantly reduced use of material and the ability to print substantially more aligner stages or moulds per build resulting in a potential 65-6 decrease in manufacturing time per aligner and 64% decrease in material cost per aligner for the case explored. In addition, the shorter/partial arches are less likely to require support structures with reduced attendant cost in materials and needing less effort and time to remove them. The shorter/partial aligners may also require less aligner material; it should be possible to vacu form more for the same sheet size.

The partial aligner may simplify impression collection.

Because partial aligners only cover a portion of the teeth during the whole treatment plan then only a partial impression of the patient's intra-oral tissue covering those teeth would be required. Where the teeth to be covered by the aligner consist of just the front eicht or ten teeth, this may in turn open the possibility of collecting the impression data using a conventional imaging device (possibly a camera or a smartphone camera) Or a less intrusive partial physical impression tray without requiring specialist intervention as these teeth are somewhat less challenging to scan than the back molars.

Indeed, it may even be possible to self-scan, which could dramatically reduce the overall cost of the process. The treatment process may result in the creation of the partial aligner, which may be manufactured using additive technology, e.g. 3D printing.

The orthodontic aligner is intended to move the targeted teeth, i.e. one or more teeth of the subset of teeth. The movement of the teeth may result in a change of the posture of the targeted teeth. The posture includes the position and/or the orientation of the targeted teeth. The aligner may effect laterally moving, tipping (inclination), tilting (angulation), and/or rotating. For example, targeted teeth may firstly be laterally moved to provide space for tipping/tilting/rotating a particular one of the targeted teeth.

The digital representation may be a dataset which can be processed resulting in an 3D image that may be displayed to the patient and/or the person treating the patient such as a dentist or orthodontist.

This processing may be executed by the processing device which can include a display or screen. The processing device may include a computer or other electronic processing means for analysing a dataset indicative of the initial arrangement of the subset of teeth.

The processing device is electronically coupled to the imaging device and the manufacturing device. The electronic coupling allows data transfer and/or data exchange between the processing device, the imaging device, and/or the manufacturing device. For example, the processing device, the imaging device, and/or the manufacturing device are electronically coupled via a wireless connection, LAN connection and/or the internet. The imaging device and the processing device may be located in a dental surgery or orthodontic practice while the manufacturing device may be remote to the dental surgery or the orthodontic practice.

The imaging device is any device which allows imaging a subset of teeth in the patient's mouth or a model or a cast of the patient's teeth. The imacing device may be configured to image all teeth of a patient's jaw or of both jaws of the patient. The imaging device may be configured to further image patient's bite and/or and the gums. The imaging device may include an optical sensor for converting the visual information of the light reflected by the teeth/gums into electronic information (e.g. dataset). The imaging device may include optical components (e.g. lenses) for focusing the light beams coming from the teeth/gums onto the optical sensor.

The manufacturing device is configured to manufacture or generate a physical model of the subset of teeth or all teeth of one or both jaws of the patient. The manufacturing device may include a means for rapid prototyping such as 3D printing and/or stereolithography. The manufacturing device may also include a milling machine which is configured to mill a model or mould of the subset of teeth.

The mould or model is used to manufacture the aligner.

This may be done by forming the orthodontic aligner over the model or mould. Discs/sheets of aligner material can be vacu/thermo formed onto the moulds/models to manufacture the aligner.

The initial arrangement of the subset of teeth includes the posture (i.e. the position and/or orientation) of each teeth of the subset of teeth. Thus, the initial arrangement includes the posture of the targeted teeth that is to be changed by wearing the aligner.

The final arrangement includes the postures of each teeth of the subset of teeth whereby the targeted teeth are in the desired position while the non-targeted teeth have the same posture in the final arrangement as in the initial arrangement. This means that the postures of the targeted teeth in the final arrangement are different to the postures of the targeted teeth in the initial arrangement. This change in the postures of the targeted teeth may be implemented virtually i.e. using a digital representation of the final arrangement. For example, the processing device includes an input device for selectively changing the posture of each targeted teeth. Alternatively or additionally, a software simulation may be used for generating the final arrangement based on the initial arrangement. The patient may be consulted for finally deciding the final arrangement of the teeth, especially the targeted teeth.

An aligner may move targeted teeth by 0.25 to 0.33 millimetres. Thus, one aligner may not be sufficient for moving the subset of teeth from the initial arrangement to the final arrangement. Rather, intermediate arrangements between the initial arrangement and the final arrangement may be necessary. These intermediate arrangements may be automatically computed by the processing device using a software or algorithm which essentially divides the movement of the targeted teeth in one or more steps or intermediate arrangements. The treatment plan includes the initial arrangement, none, one or more, intermediate arrangements, and the final arrangement. The intermediate arrangements include postures of the targeted teeth whereby the respective postures are between the respective postures in the initial arrangement and the respective postures in the final arrangement.

Each aligner corresponds to a respective intermediate or final arrangement. Thus, the targeted teeth are stepwise moved with each aligner. The treatment plan refers to the generation of the intermediate arrangements and the final arrangement. Further, the treatment plan may refer to the time period when the aligner associated with each intermediate or final arrangement is produced and worn by the patient.

The initial arrangement, the intermediate arrangement, and/or the final arrangement may include the subset of teeth or more teeth of the jaw of a patient, for example all teeth of a jaw of a patient.

The teeth of a subset of teeth are adjacent teeth, for example each tooth of the subset of teeth is in contact with an adjacent tooth. However, it is also possible that the subset of teeth covers a number of teeth arranged in line of the jaw whereby one or more teeth are missing. Nevertheless, the subset of teeth does not refer to a random selection of teeth in the jaw of the patient. Rather, the subset of teeth can be covered by a single aligner in such a way that the aligner does not cover teeth that are not included in the subset of teeth.

It is also possible to create two or more partial aligners using a single digital representation of the teeth, a single treatment plan, and/or a single mould. For example, two partial aligners per jaw can be used at the same time: one on the left molars and premolars and another on the right ones.

In this case, the digital representation and/or the mould may include more teeth than the number of teeth of the two or more subset of teeth. For example, the digital representation and the mould include all teeth of a jaw.

One or more moulds or models each corresponding to a respective one of the intermediate arrangements and/or the final arrangement are manufactured, for example using the manufacturing device. The mould includes at least the subset of teeth, optionally the mould includes only the subset of teeth. Thus, the number and the type of teeth in the mould correspond to the teeth in the patient's jaw that the aligner to be produced will cover. However, it is also possible that the mould or model includes 811 teeth of the jaw. Further, it is also possible that the mould or model includes both jaws of the patient.

The moulds or models each corresponding to a respective one of the intermediate arrangements and/or the final arrangement can be manufactured in one go after completing the treatment plan. It is also possible to create a model or mould corresponding to the first intermediate arrangement. After the aligner corresponding to the first intermediate arrangement is worn, steps a) to c) are repeated. In this embodiment, only one mould associated with the next arrangement can be manufactured in step cl) or (more generally) only one aligner is produced in step c).

The mould or model manufactured in step cl) includes the postures of the targeted teeth that differ from the respective postures of the targeted teeth in the initial position thereby effecting a movement of the targeted teeth.

The orthodontic aligner is manufactured using the mould or model, for example using known techniques. Discs/sheets of aligner material are vacu/thermo formed onto the moulds or models to manufacture the aligners. Thus, the aligner provides a cavity for receiving the subset of teeth which has a shape that deviates from a shape of a cavity created by taking a physical impression of the subset of teeth of the patient's jaw. This deviation is intentional for effecting the movement of the targeted teeth. Once the targeted teeth have finished moving (i.e. have reached their respective postures according to the intermediate alignment or final alignment based on which the aligner is made), the shape of the cavity of the aligner would correspond to the shape of the cavity when taking a physical impression of the subset of teeth.

Step c), for example step c2), may also include manually or automatically trimming the aligners.

Each aligner prepared according to the treatment plan covers the subset of teeth but not all teeth.

In an optional embodiment, step a) includes gathering a digital representation for more teeth than the subset of teeth.

For example, teeth adjacent to the subset of teeth may also be included in the digital representation and/or teeth on the other jaw may also be included in the digital representation. Teeth on the other jaw may be important for determining occlusion. The inclusion of further teeth in the digital representation may improve the treatment plan for example by providing more data for the simulation for moving the teeth from the initial arrangement to the final arrangement.

In an optional embodiment, step cl) includes preparing the mould associated with more teeth than the subset of teeth.

For example, the mould or model includes teeth of the opposing jaw which may help to provide a better occlusion. For example, if a correction of the lower (mandibular) four incisors is desired, the upper maxilla may also be scanned/imaged so that, during digital planning, it can be ensured that the target positions of the lower incisors to be corrected were suitably positioned with regards to upper incisors both functionally and aesthetically. Further, the mould can include one or more additional tooth on each end of the subset of teeth.

In an optional embodiment, the subset of teeth includes the front six, eight, or ten teeth.

These number of teeth for the subset of teeth may be used if the targeted teeth are incisors. For example, the subset of teeth may include six teeth if the targeted teeth are two incisors. Eight or ten teeth for the subset of teeth may be used if three or four incisors are the targeted teeth.

In an optional embodiment, the subset of teeth includes one, some, or all molars of 6 branch of a jaw.

Where movement of only the back teeth is desired and the aligners cover only the molars and the premolars, the aligners are hardly visible and may impact speech to a lesser degree.

This may encourage patients to wear the aligners for a longer period of time.

The extent of teeth covered by the partial aligners (the subset of teeth) can be varied not just depending on which teeth are to be corrected as part of the whole treatment plan but on a stage-by-stage basis. For example, the invention may be applied to the initial treatment with back partial aligners (back four teeth) to effect movement (e.g. distalisation) of the molars followed by partial aligners covering the front eight teeth for subsequent stages of the treatment to correct canines and incisors. So that even where treatment extends to correction of anterior and posterior teeth, partial aligners can be used at different stages of the treatment.

In an optional embodiment, the digital representation includes an indentation for mechanically engaging with an attachment attachable to one of the teeth of the subset of teeth.

The attachment may be permanently attached to one or more teeth of the subset of teeth, in particular to the non-targeted teeth. The attachment may be fixed to the tooth using an adhesive. The attachment may have any form and protrudes from the tooth to which it is attached. Commonly known attachments may be used.

The indentation may be provided in the digital representation by imaging the subset of teeth which already includes the attachment. The shape of the indentation may match the shape of the attachment.

Partial aligners for the front teeth, providing the first pre-molars are included, usually have sufficient grip/retention to stay on the teeth and partial aligners on just the back four molars may also have sufficient retention as these teeth have more marked undercuts. However, due to the more limited number of teeth being covered by a partial aligner, the aligner may be more prone to come off/disengage with the subset of teeth, particularly where only front teeth are involved (as these have less pronounced undercut profiles than molars and hence may provide less grip/hold for the aligner).

To counteract this, the attachment and indentation are provided. By placement of the attachment onto the tooth -possibly on pre-molars or canines -onto which the clear aligners, manufactured with suitable matching indentation, could snap into thereby providing an additional retention mechanism. In other words, the indentation provides a releasable mechanical interlock with the attachment for providing additional retention of the aligner on the subset of teeth.

In an optional embodiment, step b) includes repositioning and/or re-orientating the indentation with respect to the attachment.

Thus, the indentation does not perfectly match the position and/or orientation of the attachment. This slight mismatch effects a lateral and/or rotational bias. Thus, a small discrepancy between the attachment position and/or orientation and the matching attachment indentations in the aligner could be deliberately introduced, to further ensure good fit, for example over the front teeth. In one embodiment, assuming a rectangular attachment on the outside (buccal) faces of the canines, rotation of the attachment pocket/indentation on the aligner (e.g. anti-clockwise on the upper right and lower left half-arch or clockwise on the upper left and lower right half-arch) vis a vis the position of the attachments may cause a positive moment and rotation of the aligner onto the front teeth (incisors) ensuring a 'snug' fit.

In other words, the deliberate discrepancy is made to enhance the attachment of the aligner to the subset of teeth in contrast to known techniques where the attachment and the indentation are provided to effect difficult desired tooth motions without suitable grip e.g. rotation/torque of canines.

In an optional embodiment, step b) includes at least locally narrowing the digital representation of the tooth which has an undercut (as seen in a direction of placing the aligner on the subset of teeth) at the undercut.

This embodiment corresponds to profiling the aligners so they would constrict/pinch on the undercuts of teeth. In effect, the digital arch and tooth model (digital representation) from which the 3D print used for the aligner manufacture can be digitally altered/modified. Rather than exactly duplicating the teeth and gums in their target posture at each intermediate and/or final arrangement, the respective digital representations can be adapted so that, where the teeth profiles are narrow, these undercut profiles would be designed to be fractionally narrower at a position below the undercut when seen in a direction the aligner is placed onto subset of teeth. The effect of which may be a tighter fit of the aligner and better retention. The principal advantage of this retention imp rovement is that this may obviate the need to place an attachment on the tooth which may entail a clinical visit in person to a dentist or orthodontist.

The narrowing of the digital representation of a tooth may be achieved by reducing a perimeter of the tooth, by enhancing the undercut and/or by locally narrowing or indenting the digital representation of the tooth. This improvement of retention may work best with teeth which already have an undercut such as molars or premolars. Further, this may be applied to more than one tooth, especially the non-targeted teeth.

The narrowing of the digital representation of a tooth may be done to portions of the undercut. In other words, the already present undercut is increased, or an artificial undercut is provided in the digital representation of a tooth. In an optional embodiment, step c2) includes at least locally increasing the thickness of the aligner material compared to a standard aligner material.

The aligner material may be a foil or disc made of a plastic material that is rigid at room temperature or body temperature and flexible when heated.

Usually, the aligner material has a standard thickness which is used for most applications of the aligner. To enhance the application of forces or moments, the thickness of the aligner material may be locally increased, for example at locations where more force or moment needs to be transmitted. Alternatively, the thickness of the complete aligner material may be increased compared to the standard case. The thickness may be between 0.5 mm and 1 mm. Both scenarios allow a better application of force/moment on the targeted teeth.

As the partial aligner is anchored on less teeth compared to commonly known aligners, less force or moment may be applied to the targeted teeth in exceptional circumstances potentially resulting in a shortfall in the desired movement (target rotations and translations) achieved over the course of treatment with partial aligners.

Based on simulations performed by the inventors, this effect appears not to be significant in most instances with, in the worst cases, about 75% of full aligner results achieved and in most cases over 90% (It should be noted that even complete aligners do not achieve full target rotations and translations). Further, the local increase of the thickness counteracts a potential loss of force or moment.

In an optional embodiment, step b) includes preparing a virtual final arrangement. The virtual final arrangement may include a posture of one or more targeted teeth which are moved beyond the posture of the one or more targeted teeth in the final arrangement with respect to the posture of the one or more targeted teeth in the initial arrangement.

This means that the virtual final arrangement includes a movement of the postures of the targeted teeth beyond the respective postures in the final arrangement. In other words, if the targeted teeth are moved according to the virtual final arrangement, the targeted teeth would have been moved further with respect to the final arrangement. For example, if the final arrangement includes a rotation of the teeth by 5° with respect to the posture in the initial arrangement, the virtual final arrangement might include a rotation of the teeth by 7°.

This example equally applies for lateral movements, tilting and/or tipping.

The virtual final arrangement is made with the idea in mind that aligner does not effect a full change in the posture according to the virtual final arrangement but only to a certain degree, such as 90°. Thus, taken into account the discrepancy between the posture according to the virtual final arrangement and the effected posture, the targeted teeth end up at the posture of the final arrangement.

The virtual final arrangement may be computed based on simulations similar to the ones for preparing the intermediate arrangement(s) and/or the final arrangement.

In an optional embodiment, step b) includes equally distributing the difference between the posture in the virtual final arrangement and the respective posture in the final arrangement over the respective arrangements.

Thus, not only the final arrangement may be amended into the virtual final arrangement, but any intermediate arrangement can be re-calculated in view of the virtual final arrangement. In other words, a new treatment plan is generated based on the virtual final arrangement in which the virtual intermediate arrangements are steps from the initial arrangement towards the virtual final arrangement, as described above in connection to the final arrangement and the intermediate arrangements, respectively. Thereby, each intermediate arrangement may be amended by the same amount so that the differences between the intermediate arrangements and their corresponding virtual intermediate arrangements add up to the difference between the final arrangement and the virtual final arrangement. In the above example, if the final arrangement includes a rotation of the teeth by 5°, the virtual final arrangement might include a rotation of the teeth by 7°. Then, assuming five intermediate arrangements, each intermediate arrangement would result in a rotation of 1° while each virtual intermediate arrangement has a rotation of 1° + (7° -5°)/5 = 1.2°.

Thus, this embodiment refers to increasing the target rotations and/or translations per stage (e.g. where 3 stages with 2°-rotation steps are required/desired to achieve a 10° total rotation then 5 stages of 2.2 degrees could for example be prescribed) -although this would lead in principle to an 11 degree final rotation. However, this overshoot could be in practice used to compensate for observed shortfalls in reaching the target rotation/translation.

In an optional embodiment, step c) includes step c3) of directly producing the orthodontic aligner using additive manufacturing.

Additive manufacturing may include 3D printing. Thus, in this embodiment, the partial aligner is produced based on one of the arrangements of the treatment plan. The partial aligner is produced to match the arrangement of the subset of teeth in the treatment so that the aligner produced in this way can be placed on the subset of teeth for moving one or more targeted teeth. The additive manufacturing thus uses the digital information of the arrangement of the subset of teeth of the treatment plan. In this embodiment, no mould is necessary since the aligner is directly produced.

Suitable 3D printing materials have been developed allowing the aligners to be printed directly on 3D printers thereby obviating the need to generate a mould and then varuform on this mould. The present invention may also be useful in the case of direct printing of aligners since it offers similar benefits in terms of increased number of aligners per build, attendant decreased time to print and material costs per aligner, and/or other benefits such as patient comfort/acceptance. Further, the features, characteristics, and/or optional embodiments of the aligner produced using the mould also apply for this embodiment of directly printing the aligner. In particular, the manufacturing device is configured to directly produce the orthodontic aligner, i.e. is configured to 3D print the aligner based on the data generated in the treatment plan.

In an optional embodiment, step a) to c) are executed for a first subset of teeth and steps a) to c) are repeated for a second subset of teeth.

The first subset of teeth and the second subset of teeth may include a common tooth or common teeth. For example, the first subset of teeth includes the molars, and the second subset of teeth includes the front six, eight, or ten teeth.

In an optional embodiment, gathering the digital impression includes scanning the subset of teeth using an oral scanner.

The oral scanner may be an example of the imaging device. The oral scanner has a light source, a light sensor, and/or optical components for redirecting and/or focusing light. The oral scanner generates light using the light source which is directed onto the one or more teeth and/or gum using the optical components e.g. lenses, mirrors, etc. The light reflected by the one or more teeth and/or gum is focused on the light sensor and using the optical components. The light sensor converts the information in the reflected light into a dataset. Commonly known oral scanners may be used.

In an optional embodiment, gathering the digital impression includes taking a physical impression of the subset of teeth, preparing a cast of the physical impression, and scanning the cast using an oral scanner.

The oral scanner may be the same oral scanner as described above. Taking a physical impression and preparing a cast based on the physical impression is well known in the

field such that further descriptions are omitted.

In an optional embodiment, gathering the digital impression includes imaging a subset of teeth using a camera.

The camera is an example of the imaging device. The camera may be a standard camera or a camera of a mobile device. Using a camera may be sufficient for imaging a subset of teeth especially if the subset of teeth refers to the front teeth. This is not possible with commonly known aligners because, there, a digital impression of all teeth is necessary. Imaging the molars with a camera is usually not possible.

The processing device is configured to create the digital impression based on images and/or videos taken by the camera and/or the oral scanner. This is also known in the field.

In an optional embodiment, step b) includes simulating the forces and/or moments applied to the subset of teeth and/or including heuristics gathered in previous treatments and or simulations.

This is done to evaluate undesirable forces/moments and potential permanent tooth motions in adjacent teeth due to reaction forces on the teeth used as anchorage for targeted tooth movements. It should be noted that these undesirable forces are not altogether avoidable, but it can be ensured that they are below threshold loads. If so, the non-targeted teeth in the subset of teeth may move relatively insignificantly (if at all) so that spreading these forces over several non-targeted/adjacent teeth will minimise the effect.

Possible approaches to minimising loads on neighbouring teeth could include having the partial aligner cover additional/more teeth for cases where computed loads on non-targeted teeth are too high. This could he determined either by heuristics collated from analyses on the predicted loads from particular treatment cases or from patient specific analyses of load distribution for different aligner stages.

As mentioned above there is no requirement for partial aligners to cover the same teeth at each stage so this could vary depending on desired tooth movement for a given stage.

A further approach to minimising loads on neighbouring teeth could include profiling aligner fit on adjacent non-targeted teeth so as to better spread anchorage loads. In effect the digital aligner mould would be altered using again either heuristics or patient and treatment stage specific analyses to better spread load on neighbouring teeth.

Thus, in an optional embodiment, step b) includes checking whether the determined forces and/or moments are above a predetermined threshold and, if so, adding one or more teeth to the subset of teeth and/or changing the aligner fit to spread loads on the subset of teeth.

The predetermined threshold may be based on clinical experiments and/or simulations. The one or more teeth to be added to the subset of teeth are optionally adjacent to the subset of teeth.

The simulations for estimating the forces and/or moments on the non-targeted teeth may include finite-element simulations. The simulations may include the following tooth movement: tipping (inclination), tilting (angulation) or rotation. The number of targeted teeth in the simulation may vary from 1 to 4. An exemplary simulation is described in S. Barone et al: "Computational design and engineering of polymeric orthodontic aligners", Int J Numer Method Biomed Eng. 2017 Aug;33(8).

In an optional embodiment, the subset of teeth includes targeted teeth and non-targeted teeth, wherein the subset of teeth includes two non-targeted teeth on either side of each targeted teeth.

This configuration can reliably ensure that a replacement of full aligners by partial ones does not decrease the forces and moments exerted on targeted teeth to a significant degree.

Further, the inventors found that partial aligners typically achieve at least 802 of the orientation correction produced by full aligners. When multiple teeth need to be moved in the same direction, partial aligners are -in some scenarios -less effective than full aligners, but in all scenarios, they achieve at least 75% of the orientation correction of full aligners. In fact, in most configurations tested by the inventors, this ratio exceeds 90i5.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention are discussed below with reference to the accompanyinc drawings, in which: Fig. 1 is a schematic diagram of a system for manufacturing an orthodontic aligner; and Fig. 2 is a block diagram depicting steps of a method of manufacturing an orthodontic aligner.

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES Fig. 1 is a schematic diagram of a system for manufacturing an orthodontic aligner. The system 10 includes an imaging device 12, a processing device 14, and/or a manufacturing device 16. The imaging device 12, the processing device 14, and/or the manufacturing device 16 are electronically coupled with each other to exchange data for example via a LAN connection or via the internet.

The imaging device 12 may include an oral scanner and/or a camera and is configured to scan or image a subset of teeth in a jaw of the patient. The imaging device 12 can be configured to scan or image directly in the mouth of the patient or image or scan a cast made from a physical impression of the subset of teeth.

The processing device 14 may include a computer or other processing means for executing an algorithm or software. The processing device 14 may include a processor and a memory on which an algorithm or software is stored which can create a digital impression of the subset of teeth taken by the imaging device 12. The processing device 14 may further include a display or screen to display the digital impression of the subset of teeth.

The processing device 14 may also store a program, algorithm, and/or software with which a treatment plan for moving one or more targeted teeth in the subset of teeth can be generated. The treatment plan includes zero, one, or more intermediate arrangements of the subset of teeth and a final arrangement of the subset of teeth. The final arrangement includes the desired postures of the targeted teeth. The intermediate arrangements, if present, include intermediate postures between the postures of the targeted teeth in the initial arrangement and the postures of the targeted teeth in the final arrangement. An aligner may be manufactured for each of the intermediate arrangements and the final arrangement. The aligners associated with the intermediate arrangements may be necessary since the movement of a tooth that can be effected by a single aligner is limited such that several aligners are necessary for moving the targeted teeth from the initial posture to the final posture.

Further, the processing device 14 may include an input device for manually changing the final posture, e.g. a keyboard, mouse, and/or touchscreen. The input device can be used for determining the final posture. Alternatively, the processing device 14 may include an algorithm, software, and/or program for determining the final arrangement based on the initial arrangement. The input device may be used to readjust the final arrangement that is automatically generated by the algorithm, software, and/or program.

The manufacturing device 16 may include a 3D printer capable of manufacturing a mould associated with or corresponding to the intermediate arrangement and/or the final arrangement. Thus, for each intermediate arrangement and the final arrangement a respective mould is manufactured using the manufacturing device 16. The aligner is manually or automatically formed on the mould as it is commonly known.

A method for manufacturing an orthodontic aligner will be discussed in conjunction with Fig. 2.

At first, a digital representation of an initial arrangement of a subset of adjacent teeth of a patient's jaw is created, for example by scanning or imaging a subset of teeth using the imaging device 12 and then processing the dataset taken using the processing device 14 to create the digital representation. For example, the subset of teeth includes the front six, eight, or ten teeth. Alternatively, the subset of teeth includes the molars. Further, the digital representation may not be limited to the subset of teeth but can include more teeth than the subset of teeth or all teeth of a jaw or of both jaws of the patient. More generally, the subset of teeth includes at least one, optionally two or more, non-targeted teeth on at least one side, optionally on both sides, of the targeted teeth. The targeted teeth are those teeth of the subset of teeth which are intended to be moved by the aligner.

Based on the digital representation of the initial arrangement of the subset of teeth, the processing device 14 can be used for preparing a treatment plan. The treatment plan can include one or more intermediate arrangements and the final arrangement as described above.

In order to enhance the retention of the aligner on the subset of teeth, the digital representation of one or more teeth in the subset of teeth may be locally narrowed below an undercut of one or more teeth. This provides a better grip of the aligner at the undercut. This local narrowing may be manually done using the input device or automatically by the software or program.

An alternative method for increasing the retention of the aligner on the subset of teeth is attaching an attachment to one or more teeth of the subset of teeth, in particular to a non-targeted tooth. If this is done before gathering the digital representation, the digital representation already includes an indentation matching the shape of the attachment.

The aligner then also includes the indentation so that the indentation mechanically engages or interlocks with the attachment. When processing the digital representation, the position and/or orientation of the indentation may be slightly varied so that the interaction between the indentation and the attachment provides a biasinc force which, for example, presses the aligner further onto the targeted teeth.

It has been observed that the movement of the targeted teeth does not exactly follow the aligner. In other words, the targeted teeth may not be in a posture corresponding to the posture in the final arrangement. To counteract this, the final arrangement may be replaced by a virtual final arrangement in which the postures of the targeted teeth is moved beyond the respective postures in the final arrangement.

In this case, the difference between the posture in the virtual final arrangement of the targeted teeth and the respective postures of the targeted teeth of the application of the final aligner results in that the postures of the targeted teeth actually correspond to the respective postures in the final arrangement.

To this end, the intermediate arrangements may be computed based on the virtual final arrangement. In particular, the difference between the virtual final arrangement and the final arrangement is equally distributed over the intermediate arrangements.

Further, when preparing the final arrangement, the forces and/or moments applied to the subset of teeth may be simulated or determined using heuristics. If the determined forces and/or moments are above respective thresholds, further teeth are added to the final arrancement so that the aligner covers more teeth than the subset of teeth. In this way, the forces and/or movements can be better distributed over the non-targeted teeth since more non-targeted teeth are available. Alternatively or additionally, the final arrangement may be changed so that the forces and/moments are better distributed over the non-targeted teeth of the subset of teeth.

As a next step, a mould associated with the subset of teeth is prepared for each intermediate arrangement and final arrangement. Alternatively, each mould is prepared prior to the application of the respective aligner so that not all moulds are prepared at the same time. The mould or models may be prepared using the manufacturing device 16.

The mould may include more teeth than the subset of teeth. This may increase the precision of forming the aligner on the mould.

As a last step, the aligner is formed on the respective mould and trimmed and/or further processed if necessary. This step is repeated for each mould prepared in the previous step. The aligner is produced by heating up the aligner material, such as a disc or sheet, and pressing the heated-up aligner material against the subset of teeth in the mould.

The production of the aligner may include locally increasing the thickness of the aligner material compared to standard aligner. Alternatively, a thicker aligner material than what would be prescribed/recommended for a full aligner as discussed above, can be selected. An increased thickness of the aligner material provides an increased strength for generating more force and/or moment.

The above steps may be repeated for a second subset of teeth. For example, the first subset of teeth may include the molar for changing the orientation of the molars, whereas the second subset of teeth includes the front six, eight, or ten teeth. Thus, the molars and the incisors may be separately moved by two different treatment plans and two different sets of partial aligners.

In a further embodiment, the manufacturing device 16 is configured to directly produce or 3D-print the orthodontic aligner. So, in this embodiment, no mould is manufactured. Rather, the information prepared in the treatment plan, e.g. the arrangement of the subset of teeth, is used to produce the aligner that matches the subset of teeth. The aligner produced in this way mechanically engages with the subset of teeth to provide retention and to move the one or more targeted teeth.

Claims

CLAIMS1. A method of manufacturing an orthodontic aligner, the method comprising a) gathering a digital representation of an initial arrangement of at least a subset of adjacent teeth of a patient's jaw, b) preparing a treatment plan which comprises at least one arrangement of the subset of teeth, the treatment plan being for moving one or more targeted teeth of the subset of teeth from the initial arrangement towards a final arrangement, and c) producing the orthodontic aligner based on the subset of adjacent teeth for the at least one arrangement, the aligner covering the subset of teeth.
2. The method of claim 1, wherein step c) includes cl) preparing a mould associated with at least the subset of adjacent teeth for the at least one arrangement, and c2) forming the orthodontic aligner over the mould, the aligner covering the subset of teeth.
3. The method of claims 1 or 2, wherein step a) includes gathering the digital representation for more teeth than the subset of teeth, and/or step cl) includes preparing the mould associated with more teeth than the subset of teeth.
4. The method of any one of the preceding claims, wherein the subset of teeth includes the front six, eight, or ten teeth.
3. The method of any one of the claims 1 to 3, wherein the subset of teeth includes molars.
6. The method of any one of the preceding claims, wherein the digital representation includes an indentation for mechanically engaging with an attachment attachable to one of the teeth of the subset of teeth.
7. The method of claim 6, wherein step b) includes re-positioning and/or re-orientating the indentation with respect to the attachment.
8. The method of any one of the preceding claims, wherein step b) includes at least locally narrowing an undercut portion of the digital representation of a tooth for enhancing grip and/or retention.
9. The method of any one of the claims 2 to 8, wherein step c2) includes at least locally increasing the thickness of the aligner material compared to a standard aligner material.
10. The method of any one of the preceding claims, wherein step b) includes preparing a virtual final arrangement, the virtual final arrangement including a posture of one or more targeted teeth which are moved beyond the posture of the one or more targeted teeth in the final arrangement with respect to the posture of the one or more targeted teeth in the initial arrangement.
11. The method of claim 10, wherein step b) includes equally distributing the difference between the posture in virtual final arrangement and the posture in final arrangement over the respective arrangements.
12. The method of any one of the claims 1, 3 to 8, 10, and 11, wherein step c) includes step c3) of directly producing the orthodontic aligner using additive manufacturing.
13. The method of any one of the preceding claims, wherein steps a) to c) are executed for a first subset of teeth and steps a) to c) are repeated for a second subset of teeth.
14. The method of any one of the preceding claims, wherein gathering the digital impression includes scanning the subset of teeth using an oral scanner, or taking a physical impression of the subset of teeth, preparing a cast of the physical impression, and scanning the cast using an oral scanner, or imaging the subset of teeth using a camera.
15. The method of any one of the preceding claims, wherein step b) includes simulating the forces and/or moments applied to the subset of teeth and/or including heuristics gathered in previous treatments and/or simulations.
16. The method of claim 15, wherein step b) includes checking whether the determined forces and/or moments are above a predetermined threshold and, if so, adding one or more teeth to the subset of teeth and/or changing the final arrangement to spread loads on the subset of teeth.
17. The method of any one of the preceding claims, wherein the subset of teeth includes targeted teeth and non-targeted teeth, wherein the subset of teeth includes at least one non-targeted teeth on either side of the targeted teeth.
18. A system for manufacturing an orthodontic aligner, comprising an imaging device for imaging at least a subset of adjacent teeth of a patient's jaw and/or a cast of the subset of adjacent teeth of a patient's jaw, a processing device electronically coupled to the imaging device, the processing device configured to generate a digital representation of an initial arrangement of the subset of teeth and to prepare a treatment plan which comprises at least one arrangement of the subset of teeth, the treatment plan being for moving one or more targeted teeth of the subset of teeth from the initial arrancement towards a final arrangement, a manufacturing device electronically coupled to the processing device, the manufacturing device configured to prepare a mould associated with at least the subset of adjacent teeth for the at least one arrangement and/or configured to directly produce the orthodontic aligner.