Method for obtaining a 3D model of a patient's teeth

Abstract

A technique for constructing a 3D model of a patient's teeth in which 3D surface profile information of dental features of an upper and lower jaws in non-occlusion is manipulated using 3D surface profile information of dental features of the teeth in occlusion to compensate for variation in jaw shape, particularly the arch curvature of the lower jaw, between a non-occluded (mouth open) state and an occluded (mouth closed, bite) state.

Description

[0001] 008803488

[0002] 1

[0003] METHOD FOR OBTAINING A 3D MODEL OF A PATIENT’S TEETH

[0004] Field of the Invention

[0005] The invention relates to a computer-implemented method for obtaining a 3D model of a patient’s teeth and devices useful for implementing this method.

[0006] Background

[0007] For the fabrication of dental prosthetics, such as crowns, inlays, and bridges, a three-dimensional (3D) model of the teeth of the upper and lower jaw is often fabricated. The model may be a physical model or a computer model (virtual model). Thereby it is often required to record the relationship between the upper and lower teeth, especially in occlusion. It is also helpful to record how the teeth function in motion, for example during typical chewing motions or other jaw movements. A knowledge of the relationship between the upper and lower teeth, and as well as their relative movements allows a dentist or a dental laboratory technician to ensure that the dental prosthetic feels natural in the mouth and is not subject to undue stress.

[0008] The present invention has been devised in light of the above considerations.

[0009] Summary of the Invention

[0010] At its most general, the present invention relates to a technique for constructing a 3D model of a patient’s teeth in which 3D surface profile information of dental features of an upper and lower jaws in nonocclusion is manipulated using 3D surface profile information of dental features of the teeth in occlusion to compensate for variation in jaw shape (particularly the arch curvature of the lower jaw) between a nonoccluded (mouth open) state and an occluded (mouth closed, bite) state.

[0011] In a first aspect, a computer-implemented method for obtaining a 3D model of a patient’s teeth is provided. The method comprises steps a), b), c), and d). Step a) includes obtaining 3D surface profile information of dental features for an upper jaw in non-occlusion. Step b) includes obtaining 3D surface profile information of dental features for a lower jaw in non-occlusion. Step c) includes obtaining 3D surface profile information of buccal surfaces of the dental features of the upper and lower jaws in occlusion. Step d) includes calculating a 3D model (e.g. a digitised 3D volumetric model or a 3D surface mesh model) of the dental features in occlusion based on the 3D surface profile information obtained in steps a), b), and c). The calculating step d) may include determining, either implicitly or explicitly, a curvature of an arch of teeth of the lower jaw in the 3D model based on the 3D surface profile information obtained in step c).

[0012] It is known that the mandibular arch (or lower jaw) narrows due to flexion of the bone when the mouth is opened. It is thought that one source of this flexion occurs centred on the symphysis of the mandible (chin). The flexion is considered to be more pronounced the more the mouth is opened. Traditional 008803488

[0013] 2 impressions of the teeth of the lower jaw (putty / alginate in a dental tray) may exhibit this effect to lower degree because the patient almost closes their mouth after seating the impression tray, and allowing the material to set with the patient in the nearly-closed position (and therefore approximately correct mandibular arch width).

[0014] However, with the advent of intra-oral scanners, or in the case where a traditional impression tray is thicker, such closure is not possible. In these cases, a distorted arch-form will be recorded which can be corrected by the methods described herein.

[0015] The solution to this problem is to obtain the curvature of the arch of the teeth of the lower jaw in occlusion and using the curvature in occlusion for modelling the patient’s teeth on the upper jaw and on the lower jaw. Thus, the methods described herein adapt or correct any deviations between the curvatures of the arch of the teeth of the lower jaw that are recorded in non-occlusion and in occlusion (corresponding to steps b) and c), respectively).

[0016] The method thus advantageously rectifies a mismatch that can occur where separate 3D models of the upper jaw and the lower jaw obtained using non-occluded scan data are (virtually) brought into occlusion. For example, due to the flexion of the lower jaw when opening the mouth (i.e. in non-occlusion), the lower jaw as recorded in non-occlusion may have a narrower arch of the teeth of the lower jaw as recorded in occlusion. Thus, the 3D models of the upper jaw and the lower jaw cannot be perfectly brought into virtual occlusion because the virtual model of the lower jaw is too narrow for the virtual model of the upper jaw.

[0017] This issue is avoided with the methods described herein as the calculation of the 3D model includes 3D surface information about the relative position of teeth on the upper and lower jaw when in occlusion. The calculation of the 3D model may thus seek an optimal solution for the relative position of teeth both within each jaw and relative to the other jaw that fits with the obtained 3D surface scan data.

[0018] The 3D model of the patient’s teeth is generated by the computer implemented method described herein and may be used as a basis for producing prosthetics, such as crowns, inlay, and bridges, and / or orthodontic treatments. The 3D model may be a virtual model that can be displayed to a person by a computer device including a computer screen. The virtual 3D model may be used for virtually modelling prosthetics and / or orthodontic treatments as known by the skilled person. Alternatively or additionally, the 3D model obtained with the computer implemented method described herein may be used for producing a physical 3D model of the patient’s teeth, for example by milling a blank.

[0019] The 3D model may constitute a virtual mesh outlining and / or corresponding to the combined outer surface of the dental features. The 3D model may be a polygon mesh which is a collection of vertices, edges, and / or faces that defines the shape of the teeth and / or soft dental tissue of the patient.

[0020] Steps a), b), and c) may be executed in any order. The steps a), b) and / or c) may include using an intraoral scanner to collect 3D scan data from a user’s mouth. Alternatively or additionally, the steps a), b) and / or c) may include accessing pre-stored 3D scan data from a database, e.g. data that was previously measured for a patient. For example, the three pieces of 3D surface profile information may be simultaneously received by a computer implementing the methods described herein. The 3D surface 008803488

[0021] 3 profile information may be obtained by receiving or downloading the information from a dental scanner or other data storage device.

[0022] The three pieces of 3D surface profile information obtained in steps a), b), and c) can be considered as information or data obtained in separate or simultaneous scanning steps during which the upper jaw, the lower jaw, and the upper and lower jaw are scanned, respectively. For example, dental features of lingual surfaces of the teeth of the upper jaw and the lower jaw may be simultaneously recorded / scanned whereas dental features of buccal surfaces of the teeth of the upper jaw and the lower jaw may be recorded / scanned in separate steps.

[0023] The 3D surface profile information may be data that can be processed, stored, and / or sent by the computer device. In particular, the 3D surface profile information can be processed for generating a 3D model of the patient’s teeth. The 3D surface profile information includes information on dental features of the patient. For example, a piece of the 3D surface profile information may correspond to a pixel of a scan of a dental feature (e.g. a pixel of a scanned surface of a tooth), and describes the position, orientation, colour, material / tissue, etc of the dental feature corresponding to this pixel. Alternatively or additionally, the 3D data may correspond to a point cloud, including of 3D vertices (points) plus, optionally, any associated attributes such as orientation (e.g. normals), colour, curvature etc. A connected set of points can also be used - for example a triangular (or other polygon) mesh. Mathematical functions (such as Radial Basis functions) may also represent small regions of a scan (an example of 3D surface profile information).

[0024] The dental features may relate to any feature in the mouth of the patient that is visible to the human eye and / or can be recorded using optical measurement techniques. For example, the dental features may include buccal / facial surfaces of the patient’s teeth, lingual / palatal surfaces of the patient’s teeth, occlusal surfaces of the patient’s teeth, distal surfaces of the patient’s teeth (if visible), and / or mesial surfaces of the patient’s teeth. The dental features may also include buccal / facial surfaces of portions of the patient’s dental soft tissue (e.g. gum / gingiva, oral mucous membrane, etc) and / or portions of the patient’s dental soft tissue.

[0025] The dental features that are obtained in steps a), b), and c) may represent substantially all of the patient’s teeth. The 3D model may also include information of the soft tissue of the patient’s mouth. For example, the transition between a tooth and the gum is often required for modelling dental prosthetics, such as a crown or inlay.

[0026] The 3D surface profile information that is obtained in steps a), b), and c) may have been previously recorded using the same technique, which may include directly scanning the patient’s mouth using an intraoral dental scanner or obtaining an impression of the teeth, forming a model based on the impression, and scanning the model using a dental scanner.

[0027] The 3D surface profile information of the dental features that are recorded in occlusion may be considered a basis for calculating a buccal bite model. 008803488

[0028] 4

[0029] The 3D surface profile information that is obtained in steps a), b), and c) may be transmitted to the computer device using a wireless or wired communication.

[0030] For example, the dental scanner may be wireless coupled to the computer device or connected to the computer device by one or more wires such that the 3D surface profile information can be transmitted from the dental scanner to the computer device.

[0031] The computer device may include a processor and a memory which is configured to store an algorithm or program that can execute the computer device implemented method described herein. For example, the software may be configured to communicate with the dental scanner for obtaining the 3D surface profile information so that the computer device can obtain the 3D surface profile information in steps a), b), and c). Further, the software stored in the memory may be configured to control the processor for calculating the 3D model of the dental features.

[0032] The curvature of the arch of the teeth of the lower jaw may include or can be determined by the positions and / or orientations of all or a sub-set of teeth of the lower jaw. The curvature of the arch of the teeth of the lower jaw may be indicative of the flexion of the lower jaw. The calculation of the curvature of the arch of the teeth of the lower jaw may include modelling the lower jaw and / or its flexion due to the opening of the mouth.

[0033] In an optional embodiment, the steps a), b), and / or c) include obtaining a plurality of 3D scans of the dental features.

[0034] The 3D surface profile information may be in the form of a plurality of 3D scans. Each 3D scan may include the information on an area of patient’s mouth, such as a surface area of the one or more teeth and / or a gum. Each 3D scan may correspond to an “image” or “snapshot” taken by a scanner. Various techniques are known for providing a 3D scan, such as time-of-flight measurements or rendering a 3D image from a one or more 2D images that are taken by an optical scanner. The 3D scan may have the form of a mesh, a point cloud, and / or an organised point cloud.

[0035] Each 3D surface profile information can be considered a scan of the respective portion of the mouth of the patient. Thus, each 3D surface profile information or scan can be made from many partial 3D scans, i.e. 3D surface profile information for a subregion of the full arch. For example, a large number (e.g. greater than 500, preferably greater than 1000, such as 3000) partial 3D scans per full arch (corresponding to steps a) or b)) can be made. A similar number (e.g. greater than 500, e.g. 800) of partial 3D scans may be obtained for a buccal bite scan (e.g. 3D surface profile information of buccal surfaces of the dental features of the upper and lower jaws in occlusion, corresponding to step c)).

[0036] The 3D surface profile information recorded in connection with step c) may be considered a bite scan. The 3D surface profile information recorded in connection with step a) may be considered a scan of the upper jaw. The 3D surface profile information recorded in connection with step b) may be considered a scan of the lower jaw.

[0037] Thus, for calculating the 3D model of the dental features, the plurality of all the 3D scans needs to be brought into the correct spatial relationship which each other (e.g. by applying a best fit technique). 008803488

[0038] 5

[0039] Optional methods for correcting the spatial relationship include Iterative Closest Point and / or global optimisation. Iterative Closest Point may be used to align the individual scans. Global optimisation (graph optimisation) can be employed to globally optimise the many pair-wise alignments such that any accumulated errors are evenly distributed across all the scans. For example, the scans of the upper jaw can all be aligned at once (because the upper maxilla does not flex). The bite scans can then be aligned to the newly aligned upper scan. Alternatively, optimising the upper and the bite scans together can help to improve any bending in the occlusal plane of the upper arch (even when it should not theoretically be there). So this may help to improve the accuracy of the scan.

[0040] As explained above, the spatial relationship as obtained by the 3D scans of the teeth of lower jaw in the non-occlusion may differ to the spatial relationship in the 3D scans of the teeth of lower jaw in occlusion due to the flexing of the lower jaw. The method described herein is based on the idea that the arch of the teeth of the lower jaw is formed based on the 3D scans made in occlusion (corresponding to step c)) and the spatial relationship of all other 3D scans is aligned to this curvature. As described above all the pieces of the scan of the upper jaw and the bite scan may be simultaneously aligned, although they could both be aligned independently, for example if the scans were perfect or near-perfect. Standard graph optimisation may provide a mathematically optimal 'play' between pieces by minimising the shift between neighbours (so averaging any alignment error across the entire scan). A technique called fast global optimisation may be used, but any multi-way bundle adjustment-type algorithm can be employed. Basically any non-linear optimisation over many variables can be used and, for example, found in computer libraries such as Ceres. The techniques may use fitness scores (which can be based on squared distance error + / - modifiers such as Huber loss to handle noise)

[0041] The curvature of the arch of the teeth of the lower jaw may be represented by the buccal surfaces of the teeth of the lower jaw (recorded in occlusion). For example, the correct spatial relationship between the 3D scans of the buccal surfaces of the teeth of the lower jaw in occlusion may be used as a measure for the correct alignment of the teeth of the lower jaw to the teeth of the upper jaw.

[0042] There can be two distinct points to the above. Firstly, the curvature of the lower arch can be ‘corrected’ from the mouth-open lower arch scan (e.g. the scan of the lower jaw in non-occlusion), by using the curvature observed in the closed-mouth bite scan (e.g. the scan in occlusion). Secondly, an accurate occlusal relationship between upper and lower arches can be recorded directly, without requiring post-hoc artificial adjustment (such as collision detection, as is commonly used), meaning that the occlusion can be directly recorded, rather than approximating it and trying to ‘fudge’ it mathematically to look good.

[0043] A third real-world advantage can be the correction of the occlusal plane. This may apply for both the upper and lower arches / jaws. When a U-shape is scanned (which might also be the upper arch if the palate is not scanned), there is a risk that not only the width of the U is incorrect, but also the shape of the U in other planes can be warped (for example: a U-shaped piece of wire can hold the ends and bend it in various directions to warp it). The scan of the upper jaw in conjunction with the bite scan is optimised. This gives the upper arch more clues regarding the occlusal plane, compared to just optimising the scan of the upper jaw on its own. This is because the occlusal plane in the bite scan is more robust to warping 008803488

[0044] 6 because it contains data above and below the plane (upper and lower teeth) which locks the warpage in the upper-lower direction. By contrast, the ‘width’ warpage of the bite scan can be non-ideal, but this is held in place correctly by the upper arch scan (hence the simultaneous optimisation of upper and bite scans can be helpful).

[0045] In an optional embodiment, the calculating step d) includes simultaneously processing the 3D surface profile information obtained in steps a), b), and c).

[0046] For example, commonly known standard optimisation techniques can be used which simultaneously optimise the 3D surface profile information obtained in steps a), b), and c).

[0047] This means that this optional embodiment does not include initially generating a 3D model based on a 3D surface profile information on the dental features of the upper jaw in non-occlusion as well as a 3D model based on a 3D surface profile information on the dental features of the lower jaw in non-occlusion, and subsequently aligning these two models with respect to each other. Rather, this optional embodiment relates to globally processing the 3D surface profile information obtained in steps a), b), and c). In other words, none of the three pieces of 3D surface profile information may not be firstly processed. In other words, with this optional embodiment, rather than pre-calculating the upper and lower models and then aligning these two models to the bite scan, the whole dataset (all 3D surface profile information) is simultaneously processed. Thus, this optional embodiment relates to global processing the 3D surface profile information obtained in steps a), b), and c).

[0048] The advantage of this optional embodiment is that the actual arch-form of the lower arch is guided by the relationship between upper and lower teeth from the bite scan (i.e. the 3D surface profile information of buccal surfaces of the dental features of the upper and lower jaws in occlusion). Thus, the 3D model of the dental features is based on the non-flexed arch-form which provides a more accurate 3D model of the dental features in occlusion.

[0049] In an optional embodiment, the calculating step d) includes simultaneously processing all 3D scans obtained in steps a), b), and c).

[0050] With this optional embodiment, the spatial relationship between the plurality of the 3D scans is individually aligned with respect to the 3D model to be obtained. With reference to the above exemplary numbers of 3D scans, this can mean globally aligning 6800 3D scans, to create three 3D meshes or models(upper / lower / bite) simultaneously.

[0051] The fundamental idea of this optional embodiment can be compared to a 5000-piece jigsaw. With small pieces, and a tiny amount of uncertainty (play) at each link, the completed puzzle can be slightly distorted from an exact rectangle (i.e. the cumulative error of the tiny bit of play in each jigsaw piece means that the overall shape of the jigsaw can adopt many trapezoid / rhomboid shapes, not just a perfect rectangle). It is the same principle with 3D alignment of the many 3D scans. In order to guide the curvature of the arch of teeth of the lower jaw and / or the upper jaw, the bite scan (= 3D surface profile information of buccal surfaces of the dental features of the upper and lower jaws in occlusion) is used. For example, one of the 800 3D bite scans might see some of the upper right first molar and some of the lower right first 008803488

[0052] 7 molar. Their relative position in all 3 planes is thus recorded. The same can be done for the patient’s right side. If the lower (and upper) arch scan was kept rigid (and incorrectly too narrow), the alignment of the upper and lower arches cannot be reconciled to these two bits of the bite scan. If the arches are moved relative to each other to fit the right-hand side bite scan, the left hand bite scan can no longer fit together. However, if full optimisation of all arch-forms is simultaneously executed, the lower arch can adopt the correct (non-flexed) shape which maximises the fit of all 3D bite scans. This leverages the fact that 3D scans from an intraoral scanner are often small, so one can globally adjust the shape that they produce, for example using standard optimisation techniques.

[0053] In an optional embodiment, the calculating step d) includes simultaneously processing the 3D surface profile information obtained in steps a) and c) for generating an optimised 3D model of the 3D surface profile information of buccal surfaces (and optionally for generating an optimised 3D model of the 3D surface profile information of the dental features of the upper jaw), and then optimising the 3D surface profile information obtained in step b) using the optimised 3D model of the 3D surface profile information of buccal surfaces.

[0054] This optional embodiment may include optimising the scans of the upper jaw and the bite scan together, to pull the bite scan into the correct arch width, and / or simultaneously correcting any warpage of the occlusal plane in the upper arch. The optimisation of the scan of the upper jaw and of the bite scan may include optimising (varying / changing) the scan of the upper jaw and / or of the bite scan.

[0055] Then the now optimised bite scan may be considered rigid for optimising the scan of the lower arch, which will correct any occlusal plane warpage, but more importantly, correct any mandibular flexion (arch width) as described above. This means that, for optimising the scan of the lower jaw, the optimised bite scan may not be changed and can be considered “fixed”.

[0056] In the above-described optimisation / modelling processes, the bones of the upper jaw and / orthe lower jaw may be modelled as well (using commonly known techniques). However, it is also possible not to model the bones of the upper jaw and / or the lower jaw. For example, the bones may be regarded a rigid, but flexible material as a substitute for bone. In practice, this may keep things simple and provides good results.

[0057] In an optional embodiment, step a) includes generating a 3D model of the dental features of the upper jaw, step b) includes generating a 3D model of the dental features of the lower jaw, and / or step c) includes generating a 3D model of the dental features of the upper and lower jaws in occlusion.

[0058] Optionally, step d) includes varying the curvature of the arch of teeth of the lower jaw obtained in step b) with regard arch of teeth of the lower jaw obtained in step c). Further optionally, the step of varying the curvature includes simulating the symphysis of the lower jaw.

[0059] This optional embodiment is not based on the global processing of the 3D surface profile information as outlined above. Rather, as known with conventional techniques, a 3D model for the dental features of the upper jaw, a 3D model for the dental features of the lower jaw, and a 3D model of the dental features of the upper and lower jaws in occlusion are calculated. The curvature of the arch of the teeth of the lower 008803488

[0060] 8 jaw is obtained using a 3D profile information in non-occlusion (e.g. corresponding to step b)). Subsequently, the curvature of the arch of the teeth of the lower jaw is obtained using a 3D profile information in occlusion e.g. corresponding to step c)). As outlined above, the curvatures of the two models of the lower jaw differ depending on the degree of opening of the lower jaw with respect to the upper jaw when recording / scanning 3D put surface profile information forthe upper jaw and the lower jaw. However, unlike conventional techniques, any changes in the curvature of the arch of the teeth of the lower jaw is made by modelling or simulating the symphysis of the lower jaw. Roughly speaking, this means that the lower jaw is modelled to be substantially rigid except for a single joint corresponding to the symphysis. Thus, any change in the curvature of the arch of the teeth of the lower jaw may be based on a movement of a respective half jaw around the single joint corresponding to the symphysis. This may include that the spatial relationship between teeth away from the symphysis (e.g. molars and / or premolars) may not be changed and is fixed because the individual positions of the teeth away from the symphysis is only globally changed with respect to a rotation around the symphysis.

[0061] Unlike conventional techniques for aligning the model of the aperture to develop model of the lower jaw in occlusion, this optional embodiment may include setting one or more parameters forthe alignment method, e.g. fixing the relationship of one or more teeth with respect to each other for providing fixed sections of the dental arch and / or setting points with respect to which the fixed sections of the dental arch can move / rotate. This reduces the degrees of freedom for the alignment which can reduce the computational effort and / or produce better results because the alignment method mimics the physiological structure of the lower jaw.

[0062] In an optional embodiment, the step of varying the curvature includes using an As-Rigid-As-Possible alignment.

[0063] As-Rigid-As-Possible alignment are commonly known and may be adapted with regard to the fact that certain sections of the dental arch are rigid / fixed and other parts are flexible (e.g. the symphysis or a portion around the symphysis).

[0064] In an optional embodiment, the pieces of the 3D surface profile information obtained steps a) and b) are recorded when the upper and lower jaws are open by a predetermined degree with respect to the maximal opening of the lower jaw compared to the upper jaw, optionally by at least 28 % of the maximal opening of the upper and lower jaws.

[0065] The angle to which the lower jaw can be moved away from the upper jaw (the maximal opening of the jaws or the mouth) varies from patient to patient. Thus, the degree of mouth opening for inserting an intraoral dental scanner varies from patient to patient and with regard to the diameter of the intraoral dental scanner. However, for most patients and most intraoral dental scanners, the patients need to open their mouths by at least 28% of the maximum mouth opening. It has been discovered that the flexion of the lower jaw becomes relevant forthe generating of the 3D models if the mouth is opened by more than 28% of the maximum mouth opening. Thus, the methods described herein are regularly relevant when using an intraoral dental scanner for recording the 3D surface profile information. 008803488

[0066] 9

[0067] In an optional embodiment, the plurality of 3D scans obtained in steps a) and / or b) include dental features of one or more teeth and / or of dental soft tissue.

[0068] Thus, in this optional embodiment, the plurality of teeth 3D scans obtained in steps a) and / or b) allow to calculate a 3D model of the teeth and / or dental soft tissue of the upper jaw and the lower jaw, respectively.

[0069] In an optional embodiment, the plurality of 3D scans obtained in step c) include dental features of teeth only.

[0070] For example, the 3D scans obtained in step c) show dental features of the teeth of the lower jaw and / or the upper jaw. However, the plurality of 3D scans obtained in step c) may not include features of dental soft tissue (are free from dental features of soft dental tissue). In other words, the 3D surface profile information obtained in step c) may only show a surface area of the teeth in contact which each other. This is the relevant information for this 3D surface profile information. 3D surface profile information of dental soft tissue can be recorded in non-occlusion.

[0071] In a second aspect, a computer device is provided. The computer device comprises a processor and a memory which stores computer-readable instructions that, when executed by the processor cause the computer device to perform the method as described herein.

[0072] The computer device may include a commonly known computer or server. Further, the computer device may be implemented by a cloud solution. The computer device may be in data-communication with the dental scanner for obtaining the 3D surface profile information.

[0073] In a third aspect, a tangible non-transient computer-readable storage medium is provided. The tangible non-transient computer-readable storage medium has recorded thereon instructions which, when implemented by a computer device, cause the computer device to perform the method as described herein.

[0074] In a fourth aspect, a dental system is provided. The dental system comprises the computer device as described herein and a dental scanner configured to obtain the 3D surface profile information of dental features of an upper jaw and / or a lower jaw.

[0075] The dental scanner may include an intraoral scanner and / or a scanner for scanning physical 3D models, e.g. of an upper jaw and / or a lower jaw of a patient. The dental scanner may be configured to convert the scanned dental features into 3D surface profile information and send this 3D surface information to the computer device.

[0076] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided. 008803488

[0077] 10

[0078] Summary of the Figures

[0079] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0080] Fig. 1 is a schematic diagram of a dental system;

[0081] Fig. 2A is a schematic cross-sectional view of 3D models of dental features of the upper and lower jaw in occlusion, the 3D models being generated under ideal, non-realistic conditions in non-occlusion;

[0082] Fig. 2B is a schematic cross-sectional view of 3D models of dental features of the upper and lower jaw in occlusion, the 3D models being generated under realistic conditions in non-occlusion;

[0083] Fig. 3 is a block diagram of a first example of a method for obtaining a 3D model of a patient’s teeth; and Fig. 4 is a block diagram of a second example of a method for obtaining a 3D model of a patient’s teeth.

[0084] Detailed Description of the Invention

[0085] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0086] Fig. 1 is a schematic diagram of a dental system 10 which includes a computer device 12 and a dental scanner 14. The computer device 12 may include a conventional computer or server. The computer device 12 includes a processor 16 and a memory 18 which is configured to store computer readable instructions that can be executed by the processor 16. The processor 16 can be in data communication with the dental scanner 14 for the exchange of data. For example, a wireless communication can be provided between the dental scanner 14 and the computer device 12.

[0087] The dental scanner 14 may include an intraoral scanner. The dental scanner 14 may be configured to generate 3D scans of a surface area of a patient’s mouth. The dental scanner 14 may be configured to scan dental features in three dimensions and convert the recorded dental features into data, such as 3D surface profile information of the dental features. The data generated by the dental scanner 14 is of such a format that it can be processed by the computer device 12, in particular the processor 16.

[0088] The dental scanner 14 may be configured to record 3D surface profile information of the teeth and / or soft dental tissue of the upper jaw and the lower jaw in non-occlusion. For example, a part of the dental scanner 14 is inserted into the open mouth of the patient for scanning surfaces of the teeth and / or the dental soft tissue. Further, the dental scanner 14 can be configured to record 3D surface profile information of the teeth of the upper jaw and the lower jaw in occlusion. For example, a part of the dental scanner is inserted between the teeth and the cheek for scanning buccal surfaces of the teeth of the upper jaw and the lower jaw in occlusion.

[0089] The plurality of 3D scans which may each include 3D surface profile information of a section of a surface of one or more teeth and / or dental soft tissue may be transmitted to the computer device 12. The 008803488

[0090] 11 processor 16 can calculate 3D virtual models of the teeth and / or dental soft tissue of the upper jaw and the lower jaw. The processor 16 can also calculate a 3D virtual model of the teeth of the upper jaw and the lower jaw in occlusion. The processor 16 executes this calculation based on computer readable instructions (e.g. a software or algorithm) that are stored in the memory 18. The computer readable instructions provide a method for obtaining a 3D model of a patient’s teeth. This method will be described in more detail in the following.

[0091] The 3D virtual model of the patient’s teeth may be displayed to a dentist or a dental laboratory technician using a display or screen of the computer device 12 (not shown in the figures). Further, the 3D virtual model of the patient’s teeth may be used to virtually model prosthetics, such as crowns, bridges and / or inlays. The virtual models of the prosthetics can be produced using commonly known milling machines.

[0092] Fig. 2A and 2B show cross-sectional views of a 3D model of teeth of the upper jaw and teeth of the lower jaw. The teeth of the upper jaw and the teeth of the lower jaw were scanned with the mouth open, for example the mouth opening was more than 28 % of the maximum mouth opening. In ideal, non-realistic conditions as shown in Fig. 2A, the teeth of the lower jaw could be brought into perfect occlusion with the teeth of the upper jaw. However, under realistic conditions, the lower jaw flexes when opening the miles which results in a narrowing of the arch of the teeth of the lower jaw. In this case, as shown in Fig. 2B, the teeth of the lower jaw cannot be brought into occlusion with the teeth of the upper jaw because the curvature of the arch of the teeth of the lower jaw was narrower when the teeth were scanned (due to the opening of the mouth and the resulting flexion of the lower jaw) compared to the curvature of the arch of the teeth of the lower jaw that were scanned in occlusion.

[0093] In order to overcome this mismatch, the method of Fig. 3 can be employed. In step a), a plurality (approximately 3000) of 3D scans of dental features of the teeth and / or dental soft tissue of the upper jaw is recorded with the patient’s mouth open (i.e. in non-occlusion). Subsequently, the plurality of 3D scans of dental features of the teeth and / or dental soft tissue of the upper jaw is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the upper jaw. All 3D surface profile information of the upper jaw is transmitted to the computer device 12, in particular the processor 16, for further processing.

[0094] In step b), a plurality (approximately 3000) of 3D scans of dental features of the teeth and / or dental soft tissue of the lower jaw is recorded with the patient’s mouth open (i.e. in non-occlusion). Subsequently, the plurality of 3D scans of dental features of the teeth and / or dental soft tissue of the lower jaw is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the lower jaw. All 3D surface profile information of the lower jaw is transmitted to the computer device 12, in particular the processor 16, for further processing.

[0095] In step c), a plurality (approximately 800) of 3D scans of buccal dental features of the teeth of the upper and lower jaws is recorded with the patient’s mouth closed (i.e. in occlusion). This step may be considered a bite scan. Subsequently, the plurality of 3D scans of dental features of the teeth of the upper and lower jaws is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the teeth of the upper jaw and / orthe 008803488

[0096] 12 lower jaw in occlusion. All 3D surface profile information of the upper and the lower jaws is transmitted to the computer device 12, in particular the processor 16, for further processing.

[0097] In step d), all three pieces of 3D surface profile information obtained in step a), b), and c) is simultaneously processed for calculating the 3D model of the patient’s teeth. For example, all 3D scans obtained in step a), b), and c) are simultaneously processed. Thereby, the 3D surface profile information obtained in step c) is used to determine the curvature of arch of the teeth of the lower jaw. The resulting 3D model of the patient’s teeth may include a 3D model of the upper jaw (e.g. including the teeth of the upper jaw and / or soft dental tissue of the upper jaw), a 3D model of the lower jaw (e.g. including the teeth of the upper jaw and / or soft dental tissue of the lower jaw), and / or a 3D model of teeth the upper and lower jaws in occlusion (e.g. including the teeth of the upper jaw and the lower jaw).The model of the bite scan may be calculated but not displayed to the user.

[0098] An alternative embodiment of step d) includes simultaneously processing the 3D surface profile information obtained in steps a) and c) for optimising the occluded 3D scan data of step c). The optimised occluded 3D scan data is then used to process the 3D surface profile information obtained in step b) for optimising the 3D surface profile information obtained in step b).

[0099] Another exemplary method for obtaining a 3D model of a patient’s teeth is described in connection with Fig. 4. Similar to step a) of the method of Fig. 3, a plurality (approximately 3000) of 3D scans of dental features of the teeth and / or dental soft tissue of the upper jaw is recorded with the patient’s mouth open (i.e. in non-occlusion) in step a*). Subsequently, the plurality of 3D scans of dental features of the teeth and / or dental soft tissue of the upper jaw is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the upper jaw. All 3D surface profile information of the upper jaw is transmitted to the computer device 12, in particular the processor 16, which calculates a 3D model of the dental features of the upper jaw. The 3D model may include the teeth of the upper jaw and / or soft dental tissue of the upper jaw.

[0100] In step b*), a plurality (approximately 3000) of 3D scans of dental features of the teeth and / or dental soft tissue of the lower jaw is recorded with the patient’s mouth open (i.e. in non-occlusion). Subsequently, the plurality of 3D scans of dental features of the teeth and / or dental soft tissue of the lower jaw is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the lower jaw. All 3D surface profile information of the lower jaw is transmitted to the computer device 12, in particular the processor 16, which calculates a 3D model of the dental features of the upper jaw. The 3D model may include the teeth of the upper jaw and / or soft dental tissue of the upper jaw.

[0101] In step c*), a plurality (approximately 800) of 3D scans of dental features of the teeth of the upper and lower jaws is recorded with the patient’s mouth closed (i.e. in occlusion). This step may be considered a bite scan. Subsequently, the plurality of 3D scans of dental features of the teeth of the upper and lower jaws is converted into 3D surface profile information. For example, each 3D scan of a dental feature corresponds to one piece of 3D surface profile information of the teeth of the upper jaw and / or the lower jaw in occlusion. All 3D surface profile information of the upper and the lower jaws is transmitted to the 008803488

[0102] 13 computer device 12, in particular the processor 16, which calculates a 3D model of the dental features of the upper jaw and the lower jaw. The 3D model may include the teeth of the upper jaw and the lower jaw in occlusion.

[0103] In step d*), the 3D model of lower jaw as obtained in step b*) is aligned to the 3D model of lower jaw as obtained in step c*) using an As-Rigid-As-Possible alignment method. Thereby, the flexion of the lower jaw (which leads to the deviation of the two 3D models of the lower jaw) can be defined as only occurring at or near a point that corresponds to symphysis of the lower jaw. Thus, other parts of the lower jaw (e.g. the molars or pre-molars) can be modelled to be entirely rigid or substantially more rigid (compared to the simulated point of flexion) in the As-Rigid-As-Possible alignment. In this way, the As-Rigid-As-Possible alignment method is tailored to the physiological conditions of the lower jaw which can result in a more precise alignment (i.e. an alignment that matches the actual positions and / or orientations of the teeth in the lower jaw).

[0104] ***

[0105] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0106] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0107] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0108] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0109] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0110] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it 008803488

[0111] 14 will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

00880348815Claims1 . A computer-implemented method for obtaining a 3D model of a patient’s teeth, the method comprising: a) obtaining 3D surface profile information of dental features for an upper jaw in non-occlusion; b) obtaining 3D surface profile information of dental features for a lower jaw in non-occlusion; c) obtaining 3D surface profile information of buccal surfaces of the dental features of the upper and lower jaws in occlusion; and d) calculating a 3D model of the dental features in occlusion by determining a relative position of teeth both within each jaw and relative to the other jaw that represents an optimal fit with the 3D surface profile information obtained in steps a), b), and c).

2. The method of claim 1 , wherein the calculating step d) includes determining a curvature of an arch of teeth of the lower jaw in the 3D model based on the 3D surface profile information obtained in step c).

3. The method of claim 1 , wherein the steps a), b), and / or c) include obtaining a plurality of partial 3D scans that cover a subset of the dental features.

4. The method of any preceding claim, wherein the calculating step d) includes simultaneously processing the 3D surface profile information obtained in steps a), b), and c).

5. The method of any one of the claims 1 to 3, wherein the calculating step d) includes simultaneously processing the 3D surface profile information obtained in steps a) and c) for generating an optimised 3D model of the 3D surface profile information of buccal surfaces, and then optimising the 3D surface profile information obtained in step b) using the optimised 3D model of the 3D surface profile information of buccal surfaces.

6. The method of claim 1 , wherein step a) includes generating a 3D model of the dental features of the upper jaw, wherein step b) includes generating a 3D model of the dental features of the lower jaw, wherein step c) includes generating a 3D model of the dental features of the upper and lower jaws in occlusion, wherein step d) includes varying the curvature of the arch of teeth of the lower jaw obtained in step b) with regard arch of teeth of the lower jaw obtained in step c), and wherein the step of varying the curvature includes simulating the symphysis of the lower jaw.

7. The method of claim 6, wherein the step of varying the curvature includes using an As- Rigid-As-Possible alignment.008803488168. The method of any preceding claims, wherein the pieces of the 3D surface profile information obtained steps a) and b) are recorded when the upper and lower jaws are open by a predetermined degree with respect to the maximal opening of the lower jaw compared to the upper jaw, optionally by at least 28 % of the maximal opening of the upper and lower jaws.

9. The method of any one of the claims 2 to 8, wherein the plurality of 3D scans obtained in steps a) and / or b) include dental features of one or more teeth and / or of dental soft tissue.

10. The method of any one of the claims 2 to 9, wherein the plurality of 3D scans obtained in step c) include dental features of teeth only.

11. A computer device comprising a processor and a memory, the memory storing computer- readable instructions that, when executed by the processor cause the computer device to perform the method of any preceding claim.

12. A tangible non-transient computer-readable storage medium having recorded thereon instructions which, when implemented by a computer device, cause the computer device to perform the method of claims 1-10.

13. A dental system, comprising the computer device of claim 11 , and a dental scanner configured to obtain the 3D surface profile information of dental features of an upper jaw and / or a lower jaw.

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