System and method for determining patient-specific and tooth-specific limits for tooth movements in automated orthodontic treatment planning

Abstract

A system and method for determining patient-specific and tooth-specific limits for movement, including inclination and translation, to assist with the generation of a target dentition in an orthodontic planning system The method may leverage intra-oral scans or suitably digitized models of physical intra-oral impressions.

Description

SYSTEM AND METHOD FOR DETERMINING PATIENT-SPECIFIC AND TOOTH-SPECIFIC LIMITS FOR TOOTH MOVEMENTS IN AUTOMATED ORTHODONTIC TREATMENT PLANNINGFIELD OF THE INVENTION

[0001] The present invention relates to the field of orthodontic treatment planning, and more specifically, to automated planning of orthodontic treatment using a series of patientremovable appliances to reposition teeth.BACKGROUND TO THE INVENTION

[0002] Orthodontic treatment planning, especially for clear aligners, involves determining suitable target dentition for the patient. One of the key constraints in planning tooth movement is to ensure that the final teeth are not positioned in a manner that breaches the surrounding bony structure, known as the alveolar bone. The alveolar bone is a horseshoeshaped structure containing the roots of the teeth, and it constrains the range of movements in particular bucco-lingual (BL) translations and inclinations (proclination and retroclination). Excessive translation and / or inclination, either independently or combined, can lead to issues like dehiscence — the recession of the gum and bone leading to root exposure — or fenestration, where the root of a tooth creates a defect in the bone.

[0003] Current automated treatment planning systems sometimes use predefined numeric limits on tooth inclinations and translations, sometimes specific to each type of tooth, to guide treatment planning.SUMMARY OF THE INVENTION

[0004] The present invention proposes a system and method for determining patientspecific and tooth-specific limits for movement, including inclination and translation, for the purpose of automating the generation of an initial target dentition. This is achieved by leveraging intra-oral scans or suitably digitized models of physical intra-oral impressions.

[0005] The invention can take into account a patient's individual anatomy or the initial position of their teeth within the alveolar bone in an automated treatment planning system. For example, the invention may permit different movement limits to be applied to a tooth that is initially positioned eccentrically within the alveolar bone, closer to either the buccal or lingual bony margins, compared with a tooth that is centrally located. The result treatment plans are thus tailored for the patient, which cannot be achieved with the conventional approach of applying the same set of limits to all patients. By taking into account patientspecific information, the invention may thus minimize or eliminate the risk of generating a treatment plan that is suboptimal or even clinically unfeasible.

[0006] According to a first aspect of the invention, there is provided computer-implemented method for orthodontic treating planning, the method comprising: obtaining a digital model of a person’s dentition, wherein the digital model is segmented into components, and wherein the components include individual teeth and gum tissue; determining a translation movement limit for each of the individual teeth, where the translation movement limit corresponds to an amount of relative translational movement between tooth and gum tissue in the digital model before the tooth and gum tissue intersect in a manner indicative of fenestration or dehiscence; determining an inclination limit for each of the individual teeth, where the inclination movement limit corresponds to an amount of relative angular movement between tooth and gum tissue in the digital model before the tooth and gum tissue intersect in a manner indicative of fenestration or dehiscence; and storing the determined translation movement limit and inclination limit for each of the individual teeth for use in orthodontic treating planning.

[0007] Two primary types of breaches are considered during this process: (i) Fenestration, where the root of the tooth protrudes through the gum creating an isolated defect, and (ii) Dehiscence, where the tooth cuts into the gumline beyond a specific tolerance level.

[0008] Checking for dehiscence can be done without any information about the root of each tooth because the center of resistance can be estimated based on the crown height. However, it may desirable to obtain root information to have a fuller picture of the person’s dentition and to assist in checking if fenestration occurs. The digital model may therefore include a root representation that shows the position of the root for each of the individual teeth. In this example, the translation movement limit may correspond to a maximum amount of relative translational movement between tooth and gum tissue in the digital model before an intersection occurs between the root representation and gum tissue surface in a manner indicative of fenestration or dehiscence. Similarly, the inclination limit may correspond to a maximum amount of relative angular movement between tooth and gum tissue in the digital model before an intersection occurs between the root representation and gum tissue surface in a manner indicative of fenestration or dehiscence.

[0009] Roots may be incorporated into the digital model either as inferred from the intraoral surface (e.g. from tooth crown surfaces) or integrated directly by co-registering segmented root data obtained from a volumetric imaging modality (e.g. CBCT-Cone Beam Computed Tomography scans).

[0010] Each tooth from an initial position is virtually moved in a forward and backward direction, both in translation and in inclination about its center of resistance, until the tooth intersects the gum tissue, which is used as a proxy for the underlying jaw bone. The maximum permissible buccal and lingual translations, as well as inclinations (proclination and retroclination), are recorded. The translation and inclination may be considered as paired inputs, as the effect of each motion is not independent from the other; for example, the effect of a proclination movement may be mitigated by a simultaneous lingual translation motion.

[0011] In one example, the method may comprise: determining an arch curve of the person’s dentition, wherein determining a translation movement limit for each of the individual teeth comprises: calculating the magnitude of a translation of each of the individual teeth along a line normal to the arch curve at which the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration, and wherein determining an inclination limit for each of the individual teeth comprises: calculating the magnitude of a rotation of each of the individual teeth about the arch curve at which the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration.

[0012] The translation movement limit and the inclination limit may correspond respectively to the maximum amount of relative translational movement and maximum amount of relative angular movement possible before the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration.

[0013] For example, the method may include calculating an amount of relative translational movement between tooth and gum tissue in the digital model that would cause an intersection between a surface representing the gum tissue and a point on the tooth’s root representation that is spaced away from the tooth crown by a predetermined distance. This may represent the translational movement limit for fenestration.

[0014] Similarly, the method may include calculating an amount of relative angular movement between tooth and gum tissue in the digital model that would cause an intersection between a surface representing the gum tissue and a point on the tooth’s root representation that is spaced away from the tooth crown by a predetermined distance. This may represent the inclination limit for fenestration.

[0015] The method may include calculating an amount of relative translational movement between tooth and gum tissue in the digital model that would cause an intersection between the tooth and gum tissue to occur at a location beyond a predetermined distance from the gingival margin. This may represent the translational movement limit for dehiscence.

[0016] Similar, the method may include calculating an amount of relative angular movement between tooth and gum tissue in the digital model that would cause an intersection between the tooth and gum tissue to occur at a location beyond a predetermined distance from the gingival margin. This may represent the inclination limit for dehiscence.

[0017] Numeric limits may be further adjusted to correct for an average gingival offset, ensuring limits more accurately reflect distances / angles to the bony margins or, alternatively, the bony jaw structure may be obtained from CBCT data or inferred using artificial intelligence from intra-oral scan data and used in lieu of the gum surface to establish directly breaching of the bony envelope. The recorded numeric limits for tooth movement can be incorporated into the treatment planning process as penalties or weights in objective functions, as input parameters for dentition-building functions, or as filters used to validate proposed target dentitions.

[0018] This latter case may represent an independent second aspect of the invention, in which validation of a proposed target dentition is done by directly evaluating the prescribed motions of teeth against the boundaries of the intra-oral scan gum or the inferred, or actual, bone structures obtained from CBCT scans to ensure that no breach occurs. In other words, one can validate one or more proposed target dentitions by directly moving the teeth to the target positions and checking ‘on the fly’ for breaches of gum or bony tissue, rather than relying on precomputed numeric limits. According to this second aspect, there is provided a computer-implemented method for orthodontic treating planning, the method comprising: obtaining a digital model of a person’s dentition, wherein the digital model is segmented into components, and wherein the components include individual teeth and gum tissue; receiving a plurality of proposed target dentitions for the person; checking each of the plurality of proposed target dentitions for the occurrence of fenestration or dehiscence by: translating and inclining each of the individual teeth relative to the gum tissue in the digital model in a manner that moves them to the position in the proposed target dentition, and identifying any intersection between tooth and gum tissue that is indicative of fenestration or dehiscence, the method may include communicating one or more checked target dentitions to a user for selection, wherein the one or more checked target dentitions are obtained from the plurality of proposed target dentitions by excluding any proposed target dentition in which fenestration or dehiscence occurs.

[0019] According to a third aspect, the invention may provide a computer system comprising a processor and a memory storing computer-readable instructions, which are executable by the processor to cause the system to perform any of the methods described herein.

[0020] The proposed method allows for patient-specific and tooth-specific determination of movement limits, resulting in more tailored orthodontic treatment plans with reduced risk of producing results that are clinically unfeasible.

[0021] By taking into account the initial position of the teeth within the alveolar bone, the invention ensures that movements are anatomically viable, reducing the risk of complications such as dehiscence or fenestration.

[0022] The automated nature of this system facilitates efficient orthodontic treatment planning, reducing the need for clinician intervention and improving consistency in treatment quality.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Illustrations of example embodiments of a method employed by a system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning are shown in the accompanying drawings, in which:

[0024] Fig. l is a flow chart showing a method of determining a target dentition that involves pre-computed numerical limits based on tooth root data, where these limits are used as an input to a system tasked with generating a target dentition;

[0025] Fig. 2 is a flow chart showing a method of determining a target dentition that involves pre-computed numerical limits based on tooth root data, where these limits are used to filter a range of different pre-computed target dentitions;

[0026] Fig. 3 is a flow chart showing a method of determining a target dentition that involves pre-computed numerical limits based on tooth root data, where these limits are used to provide feedback about a user-designed target dentition;

[0027] Fig. 4 is a flow chart showing a method of determining a target dentition that involves performing direct dehiscence / fenestration checks on a range of different precomputed target dentitions;

[0028] Fig. 5 is a flow chart showing a method of determining a target dentition that involves pre-computed numerical limits based on tooth root data and jaw bony structure data, where these limits are used as an input to an automated system tasked with generating a target dentition;

[0029] Fig. 6 is a system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning that is an embodiment of the invention;

[0030] Fig. 7 is a system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning that is another embodiment of the invention; and

[0031] Fig. 8 is a system for using patient-specific and tooth-specific movement limits for determining a target dentition that is an embodiment of the invention.DETAILED DESCRIPTION OF THE INVENTION:

[0032] Fig. 1 illustrates an example embodiment of a method 100 employed by a system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning.

[0033] The method starts with a step 101 of obtaining a digital model of the patient's dentition. This would typically be in the form of a surface mesh (intraoral scan) obtained with the use of an intraoral scanner.

[0034] This is followed by a step 102 of preparing said model for digital planning. This would typically comprise identifying and / or separating teeth in the model from gums and / or other objects present in the model and identifying the type of / labelling each tooth (e.g. identifying a particular tooth as being the upper left canine). The result may comprise a series of separate surface meshes, each corresponding to one tooth crown, and additional surface meshes corresponding to the gum (gingiva) in each jaw. Model preparation may be fully automatic, partly automated (involving some user interaction) or fully manual (e.g. requiring the user to label each tooth).

[0035] The method then involves obtaining and integrating tooth root data (a representation of the patient's tooth roots), as this is absent from an intraoral scan. Various techniques may be used to obtain this tooth root data, which may differ in the level of accuracy of the resulting dataset.

[0036] In one example, the method includes a step 103A of obtaining an accurate representation of the patient's tooth roots from a CBCT image of the patient's dentition. The image may be aligned (co-registered) with the intraoral scan and segmented to obtain a surface mesh representation of the tooth roots. These surface meshes representing the patient's tooth roots may be combined with the corresponding tooth crown surface meshes, e.g. by merging them to obtain surface meshes representing whole teeth.

[0037] As an alternative to CBCT, the method may include a step 103B of inferring the tooth roots from the intraoral scan or the tooth crowns and / or gums that have been segmented from the scan, either algorithmically or with the use of an appropriately trained Al model. The resulting tooth root data may only approximate the patient's actual tooth roots, but this may be sufficient for the purposes of the described method. This tooth root data may have the form of surface meshes representing the predicted shape of the patient's tooth roots, or it may have a simplified geometrical form, e.g. axes, cylinders, cones, points (landmarks) and / or other geometrical construct(s).

[0038] Once tooth root data has been obtained and integrated, the method includes a step 104 of calculating tooth movement limits. These limits may dictate for each tooth the maximum amount of buccolingual translation and / or inclination, which if adhered to, should ensure that no fenestration nor dehiscence will occur during the orthodontic treatment being planned. These tooth movement limits may be calculated e.g. by computing an arch curve approximating the overall shape of the patient's dentition, translating each tooth (individually) along a line normal to that curve (approximating the buccolingual direction) until an intersection occurs between the tooth root’s representation (whether in the form of a surface mesh or in a simplified geometrical form) and the surface representing the gum (or a specific portion of the gum), or if their mutual interpenetration exceeds a certain predefined threshold. Separate checks may be performed for fenestration and dehiscence using different heuristics. Fenestration may be identified e.g. as any intersection between the tooth's root representation (moved) and the surface representing the gum (in its original position), where the portion of the root “outside” the gum is disconnected from the tooth crown. Dehiscence may be identified e.g. as any intersection which occurs above a certain distance from the original gingival margin. The measurement method may need to account for the fact that the surface of the tooth is in direct contact with the outer surface of the gum at the gingival margin (consequently, any tooth movement, however small, is bound to introduce an intersection between the surface representation of the moved tooth's root and the gum in its original position), e.g. by disregarding intersections that occur within a certain distance of the gingival margin, disregarding intersections which involve certain parts of the root (e.g. thepart which is within a certain distance of the gingival margin), disregarding occurrences of interpenetration below a certain threshold and / or using other heuristics. Pre-existing issues in patient dentition, such as gum recession may be identified beforehand, either manually or automatically (either algorithmically or with the use of an appropriately trained Al model), and these may be used to adjust (reduce) the predefined threshold. The amount of translation performed at the point where the intersection occurs or interpenetration reaches the threshold would dictate the corresponding movement limit. The measurement may be repeated independently in the lingual and buccal direction to obtain separate limits for each of these directions. The measurement may be repeated with each tooth being inclined, rather than translated, in order to obtain inclination limits. Combined inclination and translation limits may be calculated e.g. by interpolation of the maximum permitted (pure) inclination and maximum permitted (pure) translation. Prior to the measurement the tooth may be re-oriented (by inclination, angulation and / or rotation) to align with the arch curve, and this re-oriented position may be considered as the starting point for the measurement. The limits may be expressed as the maximum translation and / or inclination (e.g. a particular tooth may have a maximum buccal translation limits of 0.3 mm, a maximum lingual translation limit of 0.7 mm, a maximum buccal inclination limit of 5°, and a maximum lingual inclination limit of -9°) or they may be expressed as the maximum displacement of one or more points (landmarks) (e.g. a landmark approximating the root center or root tip may be constrained to move by a maximum of 0.6 mm in the buccal direction and 0.7 mm in the lingual direction). Alternatively, or in addition to the techniques described above, gum thickness may be calculated between the tooth root's representation and the buccal / lingual surface of the surrounding gum, and that thickness value may be used (either as is or adjusted) as the maximum movement limit.

[0039] Once movement limits have been calculated, they may be supplied as inputs to an automated (or semi-automated) system designed to carry out a step 105 of generating a proposed target dentition. These movement limits may serve as a constraint on tooth movements performed by the system when generating the target dentition. They would typically be accompanied by other constrains, e.g. that teeth should be aligned to follow a particular curve, not collide with one another etc., representing clinical and / or aesthetic requirements. The movements limits may e.g. identify a range of permitted tooth movements (e.g. a particular tooth may be constrained to inclinations between -5° and 7°), may prescribe a specific inclination amount for a given buccolingual translation amount (e.g. for a given tooth, given a translation of 0.3 mm, they may prescribe an inclination of -3°) or vice versa. The system used to generate the target dentition may utilize an objective function to evaluate suitability of a particular target dentition, in which case these tooth movement limits may be used to calculate weights or penalties for specific tooth movements.

[0040] The generated target dentition would typically form part of a treatment plan, which would be used to guide that patient's treatment. The method may comprise a step 106 ofproceeding with the treatment following the generated plan. The treatment would typically comprise manufacturing of a series of aligners, with the aim of aligning the patient's teeth as planned in the digital target dentition.

[0041] Fig. 2 illustrates a method 200 that is another embodiment of the invention. The method 200 is similar to the method 100 illustrated in Fig. 1. Identical steps are given the same reference number are and not described again. Method 200 differs in how the calculated tooth movement limits are employed.

[0042] Method 200 includes a step 205 of generating a range of different proposed target dentitions using an automated or semi-automated system. Although Fig. 2 shows step 205 following the step 104 of calculating tooth movement limits, the steps are not linked and can be performed in any order. That is, in this embodiment the tooth movement limits are not among the inputs to the system for generating the different proposed target dentitions.Consequently, these target dentitions may be generated after, at the same time as, or even before the movement limits have been computed.

[0043] Once both the tooth movement limits have been calculated and the target dentitions generated, the method includes a step 206 of filtering the generated proposed target dentitions. For example, the tooth positions in each target dentition may be analyzed and checked against these movement limits. Target dentitions where any teeth exceed the movement limits may be filtered out (excluded), and the remainder (or a subset of the remainder) displayed to the user. Tooth movement limits may be one of multiple criteria on which these target dentitions are filtered. Treatment difficulty and / or safety may be estimated by comparing the planned tooth movements to these movement limits. Those target dentitions where teeth are furthest from exceeding these limits (possibly in conjunction with other metrics or criteria) may be deemed easiest / safest, and this may be used as a basis for selecting a subset of these target dentitions to be shown to the user and / or provided to the user as feedback, in textual and / or graphical form, about the target dentition(s) shown.

[0044] The method then includes a step 207 in which a user selects one target dentition among those shown, which would form part of a treatment plan which would be used to guide the patient's treatment. The method may comprise a step 208 of proceeding with the treatment following the generated plan.

[0045] Fig. 3 illustrates a method 300 that is another embodiment of the invention. The method 300 is similar to the method 100 illustrated in Fig. 1. Identical steps are given the same reference number are and not described again. Method 300 differs in how the calculated tooth movement limits are employed.

[0046] Method 300 includes a step 305 of receiving from a user a proposed target dentition. The proposed target dentition may for example be designed by the user using one or more manual or semi-automated tools (e.g. using interactive manipulation widgets which allow the user to re-position teeth or graphical user interface elements such as sliders).

[0047] The method continues with a step 306 of evaluating this target dentition against the pre-calculated tooth movement limits. If one or more teeth are found to exceed the limits, the method include a step 307 of displaying appropriate feedback (e.g. in textual and / or graphical form) to the user. This may have a form of a warning informing the user that one or more teeth is at risk of fenestration or dehiscence. The warning may specifically identify the tooth or teeth in question. This feedback may be provided in real-time (or near real-time), especially if the tools for designing the target dentition also operate in real-time. The warning may be advisory in nature, allowing the user to continue even if a tooth movement limit is exceeded, or the system may enforce that the user resolves the issue(s) by making appropriate adjustments to the target dentition.

[0048] Once designed, the target dentition would form part of a treatment plan which would be used to guide the patient's treatment. The method may comprise a step 308 of proceeding with the treatment following the generated plan.

[0049] Fig. 4 illustrates a method 400 that is another embodiment of the invention. The method 400 is similar to the method 200 illustrated in Fig. 2. Identical steps are given the same reference number are and not described again.

[0050] Method 400 is similar to method 200 in that it includes a step 404 of generating a range of different proposed target dentitions using an automated or semi-automated system. This is similar to step 205 in Fig. 2. However, in this embodiment and differently from Fig.2, numerical tooth movement limits are not calculated, and therefore they are not among the inputs to the system.

[0051] In this embodiment, once the target dentitions have been generated in step 404, the method includes a step 405 of checking each of them for occurrences of dehiscence and / or fenestration. The techniques described above with respect to step 104, which in the previously described embodiments were used to calculate numerical tooth movement limits, may instead be used to directly check each of the generated target dentitions for presence of these issues. For example, a given target dentition may be checked for presence of fenestration by checking for intersections between any tooth root (in its proposed target position) against the surface of the gum in its original position.

[0052] The method 400 continues with a step 406 of excluding (e.g. filtering out) any target dentitions were dehiscence and / or fenestration has been identified. The method may include a step 407 of showing the remaining target dentitions to a user and receiving an input that selects one target dentition among those shown. The selected target dentition may then form part of a treatment plan which would be used to guide the patient's treatment. The method may comprise a step 408 of proceeding with the treatment following the generated plan.

[0053] Fig. 5 illustrates a method 500 that is another embodiment of the invention. The method 500 is similar to the method 100 illustrated in Fig. 1. Identical steps are given the same reference number are and not described again. In this embodiment, in addition to tooth root data, the patient's jaws' bony structure is also either obtained or inferred. For example,the method may include a step 504A of obtaining an accurate representation of the bony structure may be obtained from a CBCT image of the patient's dentition. The image may be aligned (co-registered) with the intraoral scan and segmented to obtain a surface mesh representation of the bony structure. The same image may be used to obtain both the tooth root data (in step 103A) and the bony structure.

[0054] As an alternative to CBCT, the method may include a step 504B of inferring the bony structure (algorithmically or using an appropriately trained Al model) from the intraoral scan, from the segmented teeth and / or gums and / or from the tooth root data. The inferred structure may only approximate the patient's actual bony structure, but this may be sufficient for the purposes of the described method. The resulting data may have the form of a surface mesh representing the predicted shape of the patient's bony structure, or it may have a simplified geometrical form, e.g. a curve, a polyline, a series of cylinders, a planar polygon (e.g. parallel to the occlusal plane) and / or other geometrical construct(s). The method 500 may combine one of steps 103A, 103B with either one of steps 504A, 504B.

[0055] The method may continue with a step 505 of calculating tooth movement limits in a comparable manner to that described above with respect to step 104, adapted to use the bony structure instead of (or in addition to) the gum surface to identify risk of fenestration or dehiscence. The movement limits may be calculated e.g. by identifying the amount of translation and / or inclination which introduces an intersection of a (moved) tooth root with a surface representation of the bony structure, or which leads to a particular point (landmark), e.g. root center, to be moved outside of a certain radius of a curve approximating the bony structure.

[0056] Once tooth movement limits have been calculated, the remainder of the method is identical to steps 105 and 106 in Fig. 1.

[0057] Fig. 6 shows an embodiment of a computer-implemented system 600 for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning. The computer-implemented system 600 may be implemented on a generally known computer comprising a processor and memory storing computer-executable instructions. The system 600 comprises a digital model generation module 604 configured to receive intra-oral scan data 602 or digitized physical impressions and generate a digital model of the patient dentition therefrom. The module 604 may also be configured to segment the model into distinct components, including teeth and gums. The digital model generation module 604 may provide (e.g. output) the digital model 606 to an inclination and translation module 608. The inclination and translation module 608 is configured to compute for each tooth within the digital model the amount of inclination and translation until the tooth intersects with the gum tissue, thereby determining the maximum allowable bucco-lingual translation and inclination. This information may be stored in a recording module 610 that is accessible to a treatment planning system (not shown) that is configured to use the maximum permissible translations and inclinations for each tooth in the manner discussed above.

[0058] Fig. 7 shows another embodiment of a computer-implemented system 700 for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning. The computer-implemented system 700 may be implemented on a generally known computer comprising a processor and memory storing computer-executable instructions. The system 700 comprises a digital model generation module 704 configured to receive intra-oral scan data 702 or digitized physical impressions and generate a digital model of the patient dentition therefrom. In this embodiment, the system 700 includes a root information module 705 configured to infer root position or otherwise obtain co-registered root information relating to the received intra-oral scan data 702 or digitized physical impressions. The digital model generation module 704 may be configured to integrate the inferred or co-registered root information into the digital model. The module 704 may also be configured to segment the model into distinct components, including teeth and gums. The digital model generation module 704 may provide (e.g. output) the digital model 706 to an inclination and translation module 708. The inclination and translation module 708 is configured to compute for each tooth within the digital model the amount of inclination and translation until the tooth intersects with the gum tissue, thereby determining the maximum allowable bucco-lingual translation and inclination. This information may be stored in a recording module 710 that is accessible to a treatment planning system (not shown) that is configured to use the maximum permissible translations and inclinations for each tooth in the manner discussed above.

[0059] Fig. 8 shows another embodiment of a computer-implemented system 800 for checking patient-specific and tooth-specific movement limits during orthodontic treatment planning. The computer-implemented system 800 may be implemented on a generally known computer comprising a processor and memory storing computer-executable instructions. The system 800 comprises a digital model generation module 804 configured to receive intra-oral scan data 802 or digitized physical impressions and generate a digital model of the patient dentition therefrom. The module 804 may also be configured to segment the model into distinct components, including teeth and gums. The digital model generation module 804 may provide (e.g. output) the digital model 806 to a target dentition validation module 808. The target dentition validation module 808 may be configured to receive one or more proposed target dentitions 810 e.g. from an external automated or manual treatment planning system (not shown). The target dentition validation module 808 is configured to validate one or more proposed target dentitions by directly moving the teeth to the target positions within the digital model and evaluating whether the target positions cause a breach of gum or bony tissue. In this embodiment, the validation is performed on the fly, rather than relying on predefined numeric limits for inclination and translation, to determine if the proposed target dentition is clinically viable. If the proposed target dentition passes validation, it may be communicated to a storage module 812 e.g. for display to a user.

[0060] Other embodiments may be envisaged which combine the various elements of the embodiments described above. For example, bony structure data may be incorporated intoany of the other embodiments described. Likewise, presence of fenestration and / or dehiscence may be determined by performing intersection / interpenetration checks on actual (planned) tooth movements without the need to precompute numerical tooth movement limits.

[0061] Aspects of the disclosure herein are expressed in the following numbered clauses, which form part of the description.

[0062] 1. A system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning, comprising: a digital model generation module configured to receive intra-oral scan data or digitized physical impressions and segment the model into distinct components, including teeth and gums; an inclination and translation module configured to compute for each tooth within the digital model the amount of inclination and translation until the tooth intersects with the gum tissue, thereby determining the maximum allowable bucco-lingual translation and inclination; and a recording module configured to record the maximum permissible translations and inclinations for each tooth.

[0063] 2. A system for determining patient-specific and tooth-specific movement limits for orthodontic treatment planning, comprising: a digital model generation module configured to receive intra-oral scan data or digitized physical impressions and segment the model into distinct components, including teeth, gums, and integrate inferred or co-registered roots; an inclination and translation module configured to compute for each tooth within the digital model the amount of inclination and translation until the tooth intersects with the gum tissue, thereby determining the maximum allowable bucco-lingual translation and inclination; and a recording module configured to record the maximum permissible translations and inclinations for each tooth.

[0064] 3. The system of clause 2, wherein the roots of the teeth are inferred from intra-oral scan data

[0065] 4. The system of clause 2, wherein the roots of the teeth are incorporated by coregistering root data obtained from CBCT scans.

[0066] 5. The system of clause 1 or clause 2, wherein a suitable gingival offset is applied to adjust limits.

[0067] 6. The system of clause 1 or clause 2, wherein a tolerance for gum recession allowed is incorporated into breach limits.

[0068] 7. The system of clause 6 wherein this tolerance may be decreased to reflect preexisting gum recession on a per tooth basis

[0069] 8. The system of clause 7 wherein this tolerance may be decreased based on automatically establishing gum recession on the patient’s tooth.

[0070] 9. The system of clause 1 or clause 2, further comprising incorporating a bony jaw structure either inferred from the intra-oral scan or obtained from segmenting patient CBCT data.

[0071] 10. The system of clause 5, wherein the movement simulation module uses boundaries of the bone rather than gum tissue boundary to determine limits.

[0072] 11. The system of clause 1 or clause 2, wherein the inclination and translation module is configured to virtually translate and incline each tooth within the digital model until the tooth intersects with the gum tissue, thereby determining the maximum allowable bucco-lingual translation and inclination.

[0073] 12. The system of clause 1 or clause 2, wherein the inclination and translation module is configured to find appropriate landmarks where the tooth would intersect with the gum tissue both in translation and inclination, and determining the distance or angles to these landmarks thereby determining maximum allowable bucco-lingual translation and inclination.

[0074] 13. The system of clause 1 or clause 2, wherein the maximum permissible translations and inclinations are presented to the user.

[0075] 14. The system of clause 1 or clause 2, wherein the maximum permissible translations and inclinations are used in an automated target dentition module.

[0076] 15. The system of clause 8, wherein the maximum permissible translations and inclinations are incorporated in automated target dentition module as penalties or weights in objective functions used to determine one or more clinically viable target dentitions.

[0077] 16. The system of clause 8, wherein the maximum permissible translations and inclinations are incorporated in automated target dentition module as ad-hoc filters to validate proposed target dentitions.

[0078] 17. The system of clause 8, wherein the maximum permissible translations and inclinations are incorporated in automated target dentition module as allowable ranges in the generation of target dentitions.

[0079] 18. A method for determining patient-specific and tooth-specific movement limits in orthodontic treatment planning, comprising: receiving intra-oral scan data or digitized physical impressions of a patient's dentition; segmenting the digital model into distinct components, including teeth, gums; virtually moving each tooth within the digital model in translation and inclination about its center of resistance until intersection with the gum tissue occurs; recording the maximum permissible bucco-lingual translations and inclinations for each tooth.

[0080] 19. The method of clause 18, further comprising adjusting the recorded movement limits based on an average gingival offset or estimated gum tissue thickness.

[0081] 20 The method of clause 18, wherein the bony jaw structure is inferred using artificial intelligence from intra-oral scan data or obtained directly from CBCT data.

[0082] 21. The method of clause 18, wherein two types of breaches are considered during movement limit determination: fenestration and dehiscence.

[0083] 22. A method for automated orthodontic treatment planning, wherein the proposed target dentition is evaluated directly against intra-oral scan gum boundaries or inferred or actual bone structures to ensure no breach occurs.

[0084] 23. A system for orthodontic treatment planning, comprising: a digital model generation module configured to receive intra-oral scan data or digitized physical impressions and segment the model into distinct components, including teeth, gums; and a target dentition validation module configured to validate one or more proposed target dentitions by directly moving the teeth to the target positions within the digital model and evaluating whether the target positions cause a breach of gum or bony tissue, wherein the validation is performed on the fly, rather than relying on predefined numeric limits for inclination and translation, to determine if the proposed target dentition is clinically viable.

Claims

CLAIMS1. A computer-implemented method for orthodontic treating planning, the method comprising:obtaining a digital model of a person’s dentition, wherein the digital model is segmented into components, and wherein the components include individual teeth and gum tissue;determining a translation movement limit for each of the individual teeth, where the translation movement limit corresponds to an amount of relative translational movement between tooth and gum tissue in the digital model before the tooth and gum tissue intersect in a manner indicative of fenestration or dehiscence;determining an inclination limit for each of the individual teeth, where the inclination movement limit corresponds to an amount of relative angular movement between tooth and gum tissue in the digital model before the tooth and gum tissue intersect in a manner indicative of fenestration or dehiscence; andstoring the determined translation movement limit and inclination limit for each of the individual teeth for use in orthodontic treating planning.

2. The computer-implemented method of claim 1 further comprising: determining an arch curve of the person’s dentition,wherein determining a translation movement limit for each of the individual teeth comprises:calculating the magnitude of a translation of each of the individual teeth along a line normal to the arch curve at which the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration, andwherein determining an inclination limit for each of the individual teeth comprises:calculating the magnitude of a rotation of each of the individual teeth about the arch curve at which the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration.

3. The computer-implemented method of claim 1 or 2, wherein the translation movement limit and the inclination limit correspond respectively to the maximum amount of relative translational movement and maximum amount of relative angular movement possible before the tooth and gum tissue intersect in a manner indicative of either dehiscence or fenestration.

4. The computer-implemented method of any one of claims 1 to 3, wherein the digital model includes a root representation that shows the position of the root for each of the individual teeth, and wherein:the translation movement limit corresponds to a maximum amount of relative translational movement between tooth and gum tissue in the digital model before an intersection occurs between the root representation and gum tissue surface in a manner indicative of fenestration or dehiscence; andthe inclination limit corresponds to a maximum amount of relative angular movement between tooth and gum tissue in the digital model before an intersection occurs between the root representation and gum tissue surface in a manner indicative of fenestration or dehiscence.

5. The computer-implemented method of claim 4 further comprising: obtaining root information for the person’s dentition;determining the root representation of each of the individual teeth; and integrating the root representations into the digital model.

6. The computer-implemented method of claim 5, wherein the root information is obtained from a CBCT scan of the person’s dentition.

7. The computer-implemented method of claim 5, wherein the root information is inferred from an intraoral scan of the person’s dentition or from the individual teeth and gum tissue components of the digital model.

8. The computer-implemented method of any one of claims 4 to 7 including: calculating an amount of relative translational movement between tooth and gum tissue in the digital model that would cause an intersection between a surface representing the gum tissue and a point on the tooth’s root representation that is spaced away from the tooth crown by a predetermined distance; andcalculating an amount of relative angular movement between tooth and gum tissue in the digital model that would cause an intersection between a surface representing the gum tissue and a point on the tooth’s root representation that is spaced away from the tooth crown by a predetermined distance.

9. The computer-implemented method of any one of claims 1 to 8 including: calculating an amount of relative translational movement between tooth and gum tissue in the digital model that would cause an intersection between the tooth and gum tissue to occur at a location beyond a predetermined distance from the gingival margin; andcalculating an amount of relative angular movement between tooth and gum tissue in the digital model that would cause an intersection between the tooth and gum tissue to occur at a location beyond a predetermined distance from the gingival margin.

10. The computer-implemented method of any one of claims 1 to 9, wherein the steps of determining a translation movement limit and determining an inclination limit include applying a gingival offset.

11. The computer-implemented method of any one of claims 1 to 10, wherein the steps of determining a translation movement limit and determining an inclination limit include applying a tolerance for permitted gum recession.

12. The computer-implemented method of claim 11 including adjusting the tolerance for a tooth to reflect pre-existing gum recession.

13. The computer-implemented method of any one of claims 1 to 12 further comprising:obtaining a jaw bone structure corresponding to the person’s dentition; and integrating a digital representation of the jaw bone structure into the digital model, wherein determining the translation movement limit further comprises calculating an amount of relative translational movement between tooth and gum tissue in the digital model before the tooth and jaw bone structure intersect in a manner indicative of fenestration or dehiscence, andwherein determining the inclination limit further comprises calculating an amount of relative angular movement between tooth and gum tissue in the digital model before the tooth and jaw bone structure intersect in a manner indicative of fenestration or dehiscence.

14. The computer-implemented method of any one of claims 1 to 13 further comprising:using the determined translation movement limit and inclination limit for each of the individual teeth to obtain a proposed target dentition for the person.

15. The computer-implemented method of any one of claims 1 to 13 further comprising:receiving a proposed target dentition for the person; andusing the determined translation movement limit and inclination limit for each of the individual teeth to validate the proposed target dentition for the person.

16. The computer-implemented method of any one of claims 1 to 13 further comprising:receiving a plurality of proposed target dentitions for the person; andusing the determined translation movement limit and inclination limit to filter the plurality of proposed target dentitions.

17. A computer-implemented method for orthodontic treating planning, the method comprising:obtaining a digital model of a person’s dentition, wherein the digital model is segmented into components, and wherein the components include individual teeth and gum tissue;receiving a plurality of proposed target dentitions for the person;checking each of the plurality of proposed target dentitions for the occurrence of fenestration or dehiscence by:translating and inclining each of the individual teeth relative to the gum tissue in the digital model in a manner that moves them to the position in the proposed target dentition, andidentifying any intersection between tooth and gum tissue that is indicative of fenestration or dehiscence.

18. The computer-implemented method of claim 17 further comprising: communicating one or more checked target dentitions to a user for selection, wherein the one or more checked target dentitions are obtained from the plurality of proposed target dentitions by excluding any proposed target dentition in which fenestration or dehiscence occurs.

19. A computer system comprising a processor and a memory storing computer-readable instructions, which are executable by the processor to cause the system to perform a method according to any one of claims 1 to 18.

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