Method and system for identifying islands of interest

Abstract

According to an embodiment, a computer-implemented method for identifying an islanding (303) of interest on a 3D dental model (100, 300) is disclosed. The method comprises the steps of receiving at least first dental 3D scan data of the subject, generating a 3D dental model (100, 300) based on the received at least first dental 3D data of the subject. The method further comprises the step of identifying a plurality of regions on the 3D dental model (100, 300), each region of the plurality of regions indicating the presence of at least one dental condition. A severity factor value is determined for each of the plurality of regions, the severity factor value indicating a severity of the at least one dental condition. The method further comprises the step of marking each region of the plurality of regions with a visual indicator on the 3D dental model (100, 300), wherein the visual indicator is selected based on the determined severity factor value for the region. A plurality of islands (303) are then obtained by grouping the plurality of regions on the 3D dental model (100, 300), such that each island (303) comprises adjacent regions indicating the presence of at least one dental condition. The 3D dental model (100, 300) is then displayed.

Description

Technical Field

[0001] The present disclosure relates to a computer-implemented method and system for identifying islands of interest on a virtual 3D dental model, and more particularly, to obtaining a plurality of islands on a 3D dental model and displaying the 3D dental model. Background Art

[0002] It is known that there are various 3D scanning technologies, and a virtual 3D dental model reflecting the intraoral situation of a subject (patient) can be generated using known 3D scanning technologies. For example, by using an intraoral 3D scanner, 3D scanning data can be obtained, and a virtual 3D dental model is generated thereby, which accurately represents objects in the subject's mouth, such as teeth and gums. By processing the 3D scanning data, signs of dental conditions can be determined and presented on the generated 3D dental model. The 3D dental model can be displayed on, for example, a display together with the signs of dental conditions. A user (e.g., a dentist) can manually interact with the generated 3D model and visually inspect the determined signs of dental conditions. However, this inspection method relies on the manual work of the user, who needs to carefully search for signs of dental conditions on the 3D dental model. For example, signs of dental conditions may be scattered between multiple parts of the 3D dental model, and may even be located in a part that is not directly in the user's field of view. Therefore, it is very troublesome to manually identify and inspect all signs of dental conditions on the 3D dental model.

[0003] Based on the above, there is an obvious need to develop a method that allows for easy identification and overview of signs of dental conditions on 3D dental models. Summary of the invention

[0004] The invention is set out in the accompanying claims.

[0005] According to an embodiment, a computer-implemented method for identifying islands of interest on a 3D dental model is disclosed.

[0006] The term "3D dental model" in this disclosure refers to a virtual 3D dental model.

[0007] In the context of the present disclosure, the term "island" may be understood as a surface area, region of interest or volume on a 3D dental model that indicates the presence of a dental condition. An island on a 3D dental model may take any shape and may be characterized by its surface size or volume. An island may consist of a single surface or volume unit (further referred to as an area) of a 3D dental model. The method according to the present disclosure includes a step of receiving at least first dental 3D scan data of a subject. The data may initially be obtained by scanning the oral cavity of the subject with an intraoral scanner at a certain point in time. The first dental 3D scan data may be a series of 2D images for generating a 3D dental model. The first dental 3D scan data may include texture data, such as color data or fluorescence data. An example of an intraoral scanner is Trios 4 from 3Shape. Alternatively, at least first dental 3D scan data of a subject may be obtained by 3D scanning a dental cast created by taking a dental impression of the subject using a 3D scanner. A data processing unit may receive at least the first dental 3D scan data, which is further processed at the data processing unit.

[0008] The method also includes generating a 3D dental model based on at least the first dental 3D scan data of the subject received. The 3D dental model generated based on at least the first dental 3D scan data of the subject accurately represents the intraoral situation of the subject, which means that it accurately represents the upper and lower rows of teeth of the subject and the surrounding gums. The 3D dental model can be represented, for example, by a 3D mesh. The 3D mesh can be composed of a plurality of triangles or other mesh forming units. Each point on the 3D mesh is generally referred to as a vertex. Two vertices can be connected to each other by a straight line called an edge. Three edges can form a triangle of the 3D mesh, also referred to as a facet. In another example, the 3D dental model can be represented by a point cloud or any other way of representing a 3D object. The generated 3D dental model can be displayed to a user, for example on a display of a computer or tablet computer.

[0009] The method according to the present disclosure also includes the step of identifying multiple regions on the 3D dental model, wherein each of the multiple regions indicates the presence of at least one dental condition. Regions can be viewed as separate building elements of a 3D mesh, such as vertices or facets, which indicate the presence of a dental condition. Regions on the generated 3D dental model can indicate the presence of at least one dental condition that a subject may suffer from. Dental conditions in the context of the present disclosure may include tooth wear, caries presence, gingivitis, or any combination thereof. For example, if caries are present on a portion of a subject's maxillary canine teeth, the dental condition will be reflected in one or more regions on the generated 3D dental model corresponding to the actual diseased portion of the canine teeth. The first dental 3D scan data from which the 3D dental model is generated may include information about the type and location of the dental condition. The presence of at least one dental condition can be identified by a recognition function, as described below.

[0010] In addition, a severity factor value is determined for each of the multiple regions, wherein the severity factor value indicates the severity of the dental condition. In the presence of caries, the severity factor value can be obtained by a scoring function to determine a caries score. Here, the severity factor value can take the form of a scalar value of 0 to 6 according to the International Caries Detection and Assessment System (ICDAS) caries severity classification. In the case of tooth wear, the severity factor value can be expressed in cubic millimeters, indicating the volume of tooth mass loss. In the case of gingivitis, the severity factor value can be expressed using a Modified Gingival Index (MGI) classification with a scalar value of 0 to 4.

[0011] According to the method of the present disclosure, each of the multiple regions on the generated 3D dental model is marked with a visual indicator, wherein the visual indicator is selected based on the severity factor value determined for the region. For example, an area indicating the presence of caries can be visually marked with yellow on the 3D dental model, wherein the severity factor of the area has been determined to be low. According to the ICDAS scoring system, the determined severity factor value can be a scalar number 1 or 2, and this can also be referred to as "initial caries". Similarly, an area indicating the presence of caries can be visually marked with red on the 3D dental model, wherein the severity factor value of the area has been determined to be high. The purpose of such marking is to focus the user's attention on the portion of the 3D dental model that needs to be inspected. Therefore, the user can first focus on inspecting the portion of the 3D dental model where the identified area is marked with red (which may indicate a serious development of at least one dental condition). The user can interact with the 3D dental model via the user interface by rotating, translating, zooming in or out to obtain a clear and unobstructed view of the portion of interest in the 3D dental model. However, in the case where the area indicating the presence of at least one dental condition is scattered on the 3D dental model, the user may have to perform multiple manual operations of interacting with the 3D dental model in order to bring the area of ​​interest into the field of view for diagnosis. For this process, the user is likely not to notice the area at the periphery of the 3D dental model or the area blocked from the field of view by other parts of the 3D dental model. The field of view in the context of the present disclosure may be understood as a direction perpendicular to the display surface.

[0012] The method further comprises the step of obtaining a plurality of islands by grouping a plurality of regions on the 3D dental model such that each island includes adjacent regions indicating the presence of at least one dental condition. As previously mentioned, the term "island" may be understood as a surface area, a region of interest, or a volume on the 3D dental model. Thus, an island may be formed by a plurality of adjacent regions, all of which indicate the presence of at least one dental condition. For example, certain regions of an island may indicate the presence of caries, while other regions of the same island may indicate the presence of tooth wear. Alternatively, all regions of an island may indicate the presence of the same dental condition. A common feature shared by all regions of the same island is that they are adjacent to at least one other region of the island. For example, in the case where the 3D dental model is represented by a triangular mesh, at least two regions of the island share at least one common edge of a facet in the mesh. By grouping adjacent regions into islands, significant advantages may be obtained because global information about the subject's dental condition is created. This global information is superior to local information represented only by regions marked with visual indicators because the complexity of the 3D dental model is reduced, thereby allowing the user to more easily examine the dental condition.

[0013] In an embodiment, the method includes, in addition to receiving first dental 3D scan data of a subject, receiving second dental 3D scan data of the same subject, the second dental 3D scan data being obtained at a later time compared to the first dental 3D scan data. The second dental 3D scan data may be obtained by scanning the oral cavity of the subject using an intraoral scanner, or may be obtained by 3D scanning a dental mold created by taking a dental impression of the subject using a 3D scanner in an alternative manner. The second dental 3D scan data may be obtained a few days or months after the first dental 3D scan data is obtained. The second dental 3D scan data is typically obtained one year after the first dental 3D scan data is obtained. The second dental 3D data may be received by the data processing unit together with the first dental 3D scan data, or may be received separately. In this case, a 3D dental model may be generated based on the received first and second dental 3D scan data. For example, a first 3D dental model may be generated based on the first dental 3D scan data, and a second 3D dental model may be generated based on the second dental 3D scan data. The 3D dental model may then be generated by overlapping the first and second 3D dental models. It may also be said that the two 3D dental models are aligned with each other. This is particularly advantageous because the second dental 3D scan data can be directly compared to the subject's first dental 3D scan data. When displayed, the 3D dental model represents a direct comparison of first and second dental 3D scan data obtained at different times. The 3D dental model can visualize changes in the dental condition that occurred in the time between obtaining the first and second dental 3D scan data. In this case, the 3D dental model can be referred to as a scan comparison. For example, initial caries in a certain area determined from the first dental 3D scan data may develop into moderate caries in the area determined from the second dental 3D scan data. Another example is tooth wear, where changes in tooth wear can be indicated on the displayed 3D dental model. For specific areas on the 3D dental model, changes in tooth wear can be indicated with different colors depending on the degree of wear.

[0014] In addition, the method includes displaying a user interface in the form of a preview list, wherein the preview list includes a plurality of list members. Each list member is associated with an island from a plurality of islands, such that a user can switch between islands on the 3D dental model by navigating between the list members. This feature is particularly useful because it allows a user to simply access all identified islands on the 3D dental model because all islands are associated with the preview list members. In addition, via the user interface, by switching between the list members, the user can also switch between islands on the 3D dental model. As will be seen in further detail later, this feature allows a user to easily detect and examine at least one dental condition associated with the island. Thus, the user is reliably assisted in performing the task of interacting with the 3D dental model to examine the dental condition.

[0015] According to an embodiment, a preview list including a plurality of list members may be automatically generated. The plurality of list members may be created such that each list member is associated with an island from a plurality of islands. Thus, advantageously, the list members associated with the islands are generated without user interaction, wherein each island is determined by algorithmic analysis of the 3D dental model.

[0016] Furthermore, the method includes, when a user selects a list member in the preview list, automatically displaying the islands on the 3D dental model associated with the selected list member. The preview list may be displayed with toggle buttons, such as "previous" and "next" buttons, allowing the user to switch between different list members. The preview list may also be displayed in a manner that allows the user to click on different list members without using toggle buttons. Once the user presses the toggle button or clicks on a particular list member, the corresponding islands are automatically displayed on the 3D dental model. Alternatively or additionally, the user may switch between list members using a mouse "scroll" button or any other suitable user input method.

[0017] Automatically displaying the islands associated with the selected list members may include automatically adjusting the 3D dental model so that the associated islands are brought into the field of view. The field of view may be considered to be a direction perpendicular to the display surface. The islands may be brought into the field of view by fitting a plane to the vertices of the area constituting the islands, obtaining the normal of the plane and coinciding the normal with the field of view. Automatically adjusting the 3D dental model may include rotating, translating, enlarging at least a portion of the 3D dental model and / or making at least a portion of the 3D dental model transparent. The adjustment of the 3D dental model may be performed as follows. As a first step, a zoomout may be performed. Secondly, a rotation and / or translation movement may be performed, and finally, a zoom-in of a specific area of ​​interest may be performed. These steps may be performed automatically.

[0018] During the zoom-in step, transparency may be applied to the surfaces surrounding the islands. Similarly, during the zoom-out step, transparency may be removed so that the entire 3D dental model is viewed without transparency applied. The steps of adding or removing transparency may be performed automatically.

[0019] In an embodiment, the method further comprises automatically sorting the list members in the preview list based on a sorting criterion, wherein the sorting criterion may be an island surface area. Thus, the list member corresponding to the island with the largest surface area may appear as the first list member, the list member corresponding to the island with the second largest surface area may appear as the second list member, and so on. The sorting criterion may be an island importance factor value, which may be defined as a function of the island surface area and the severity factor value of the area constituting the island. The island importance factor value may be a scalar value. The list member corresponding to the island with the highest island importance factor value may appear as the first list member in the preview list. Additionally or alternatively, the sorting criterion may comprise the island surface area and the island importance factor value. Thus, the user is reliably assisted in performing the task of inspecting the most relevant region of interest in the most efficient manner. For example, the user may first inspect the island with the largest surface area, or the island with the highest island importance factor value. In this way, the efficiency of detecting a particular dental condition and designing an appropriate treatment plan is maximized.

[0020] The surface area of ​​an island can be calculated as the sum of the areas of the individual regions that make up the island. If the region is a triangle of a 3D mesh, and the coordinates of vertices A, B, and C are known, the area of ​​the region can be calculated using the common vector product formula for calculating the area of ​​a triangle:

[0021] The list members corresponding to the islands having the highest importance factor values ​​may be automatically identified, and the 3D dental model may be adjusted so that the islands corresponding to the identified list members are brought into the field of view. This means that the user can immediately view and examine the most severe dental condition represented in the 3D dental model of the subject's intraoral condition. For example, if there is severe caries on one of the molars, the 3D dental model will automatically be adjusted so that the islands representing caries on the molars are brought directly into the field of view of the user (e.g., a dentist). Alternatively, the list members corresponding to the islands having the largest surface areas may be automatically identified, and the 3D dental model may be adjusted so that the islands corresponding to the identified list members are brought into the field of view.

[0022] The method according to an embodiment may include, when a user selects a list member from the preview list, adjusting the 3D dental model so that an island corresponding to the selected list member is brought into the field of view. Additionally, it may include displaying an island surface value for an island corresponding to the selected list member. This feature allows the user to select a list member from the preview list, visually inspect the corresponding island on the 3D dental model, and obtain information about the island surface value, for example as a square millimeter value displayed next to the island.

[0023] In addition to the island surface value displayed in square millimeters, the tooth number and / or the sequence number of the island in the preview list can also be displayed. For example, the tooth number can be a number from 1 to 16. If the island is the first island in the preview list, the sequence number of the island can be number 1. The user can select a dental treatment based on the information about the island surface value.

[0024] Additionally or alternatively, a method according to an embodiment may include displaying at least one infrared (IR) image of one or more teeth associated with the displayed island.The at least one infrared image may be a 2D infrared image.

[0025] In an embodiment, marking each of the plurality of regions with a visual indicator comprises coloring each of the plurality of regions. For example, regions with high severity factor values ​​may be colored red. This is advantageous to the user because red regions on the 3D dental model that require priority inspection may be easily detected. Regions with lower severity factor values ​​may be colored different shades of red, or, for example, yellow or green. Other colors may also be used. Thus, an island may include regions with different severity factor values ​​and may therefore be colored a plurality of different colors or different shades of the same color.

[0026] However, if the user wishes to examine the islands in detail, the color may hinder viewing. Therefore, in one embodiment, displaying the islands further comprises removing the visual indicator from each region constituting the islands, so that the user can view the islands on the 3D dental model without obstruction.

[0027] In one embodiment, displaying the islands may include blurring a portion of the 3D dental model other than the displayed islands. This may be advantageous because it may help a user to examine the 3D dental model more efficiently. Alternatively, rather than blurring a portion of the 3D dental model other than the displayed islands, a portion of the 3D dental model other than the displayed islands may be rendered at a lower resolution than a portion of the 3D dental model corresponding to the displayed islands.

[0028] Alternatively or additionally, the automatically adjusted 3D dental model may include a portion of the 3D dental model other than the island being brought into view. The fading out may be achieved, for example, by changing the transparency of a portion of the 3D dental model other than the displayed island or by coloring this portion of the 3D dental model darker. This may be advantageous because it may help the user to examine the 3D dental model more efficiently.

[0029] Alternatively, instead of fading out a portion of the 3D dental model except for the island brought into the field of view, the island brought into the field of view may be colored a darker or lighter color than the rest of the 3D dental model.

[0030] Islands brought into the field of view can be configured to flash to draw the user's attention, thereby helping the user to examine the 3D dental model more efficiently.

[0031] In one embodiment, automatically adjusting the 3D dental model may include displaying only the outlines of the islands that are brought into the field of view. The displayed outlines may be colored according to the severity factor value determined for the islands.

[0032] According to an embodiment, if the determined severity factor value is above a first threshold, the severity of at least one dental condition may be a high severity. If the determined severity factor value is between the first threshold and the second threshold, the severity may be a moderate severity. If the determined severity factor value is below the second threshold, the severity may be a low severity. In the case of tooth wear as a dental condition, the severity factor value may directly represent the amount of tooth wear or the loss of tooth substance, expressed in cubic millimeters. Tooth wear may be observed on a 3D dental model generated by overlapping or aligning a first 3D dental model and a second 3D dental model. For example, a heat map superimposed on the 3D dental model may be used to visualize tooth wear or the loss of tooth substance from the first 3D dental model to the second 3D dental model. When the models are aligned, the heat map may indicate the distance between corresponding vertices of the first and second 3D dental models. In one example, the first threshold may be 0.8 mm, while the second threshold may be 0.3 mm. The severity factor value in the case of tooth wear may also be represented in an alternative manner. For example, the known Tooth Wear Index scoring (TWI) may be used, wherein a total score from 0 to 4 is assigned to each area.

[0033] In one embodiment, the method further comprises copying the island importance factor value into a digital dental chart. Additionally or alternatively, the method comprises copying the island surface area into the digital dental chart. The digital dental chart may, for example, be in the format of a universal numbering system, where teeth in the upper jaw are represented by numbers 1 to 16 and teeth in the lower jaw are represented by numbers 17 to 32. The island importance factor and / or island surface area of ​​a particular tooth in the 3D dental model may be copied into the corresponding tooth representation in the digital dental chart.

[0034] In one example, the method further comprises: when the user selects a list member from the preview list, the step of automatically adjusting the 3D dental model so that an island corresponding to the selected list member is brought into the field of view.

[0035] Furthermore, the method may include the steps of calculating an island volume difference value for the islands corresponding to the selected list member and displaying the island volume difference value for the islands corresponding to the selected list member. The island volume difference may be understood as a volume change of the islands on the 3D dental model, wherein the 3D dental model is generated based on the first 3D dental model and the second 3D dental model. Thus, when the first 3D dental model and the second 3D dental model are aligned, the island volume difference may indicate a loss or gain in tooth volume of a particular tooth. The island volume difference may be displayed in cubic millimeters. An example of a volume increase may be the presence of calculus or dental plaque, which is a form of hardened dental plaque, because the tooth volume increases over time due to calculus. Another example of a volume increase is a dental filling. Tooth wear is an example of a volume loss, because the tooth volume decreases over time due to tooth wear. One method of calculating the island volume difference is to calculate the signed volume of a tetrahedron formed by connecting the vertices of the triangular facets in the islands with arbitrary points. Summing the obtained volumes yields an expected value of the island volume difference. A heat map may be used to highlight the change in volume. Each vertex in an island can be shaded with a color based on its distance from the opposing surface. The colors on the individual facets can then be interpolated between the vertices to achieve full surface shading.

[0036] In an embodiment, the method may include calculating an island volume difference for islands corresponding to the selected list members. An island may represent a difference between surfaces of the aligned first 3D dental model and the second 3D dental model and may therefore be bounded by two island surfaces, namely an island on the first 3D dental model and an island on the second 3D dental model. An island volume difference metric may quantify the difference between the aligned first 3D dental model and the second 3D dental model. The value of this volume difference may be determined and may provide important insights into the severity of the patient's dental condition, for example it may indicate how much tooth volume has been lost due to caries or how much tartar has accumulated in the time span between obtaining the first 3D and second dental 3D scan data.

[0037] Generating a 3D dental model based on the received at least first and second dental 3D data of the subject may include:

[0038] - generating a first 3D dental model based on the first dental 3D scan data,

[0039] - generating a second 3D dental model based on the second dental 3D scan data,

[0040] - Overlaying the first and second 3D dental models.

[0041] Calculating the island volume difference may include identifying boundary facets of the islands on the second 3D dental model. These boundary facets may be identified as facets that do not have three neighbors but only one or two neighboring facets, indicating the presence of a dental condition.

[0042] In addition, for each identified boundary facet, a nearest facet on the first 3D dental model may be identified. The nearest identified facets on the first 3D dental model may be connected to each other to form a closed path that defines an inner surface and an outer surface on the first 3D dental model. The facets of the inner surface may be defined, for example, by running a Flood-Fill algorithm, in which facets within the inner surface are identified and the inner surface area is "flooded" until a closed path is reached.

[0043] Furthermore, the identified nearest facets on the first 3D dental model may be connected to corresponding boundary facets on the second 3D dental model to define a closed volume representing the desired island volume difference. The process of connecting facets may also be referred to as a "stitching" process.

[0044] In one example, "stitching" may include using a dynamic programming approach. For example, "a" is an array of all boundary facets on the inner surface of the first 3D dental model, and "b" is an array of all boundary facets on the islands of the second 3D dental model. In addition, if a[0] and b[0] are the closest pair of points between two boundaries, the two-dimensional recursive relationship of the dynamic programming approach can be given by the following formula:

[0045] f(i,j)=max(f(i-1,j)+dist(a[i-1],b[j]),f(i,j-1)+dist(a[i],b[j-1])),

[0046] When (i,j)≠(0,0) and dist(a[0],b[0]) when (i,j)=(0,0).

[0047] The result of the "stitching" process may be a closed volume defining the facets. To determine the expected island volume difference for the closed volume of the facets, the sum of the signed volumes of the tetrahedrons defined by the three vertices of each facet may be determined. The origin of the tetrahedron may be an arbitrary point. An advantage of this method is that the island volume difference may be accurately calculated even if one or more island surfaces on the first or second 3D dental model are relatively curved. This may be the case, for example, if the island includes the occlusal edge of an incisor.

[0048] To calculate the vertex The signed volume of a tetrahedron can be expressed as:

[0049]

[0050] In an embodiment, the island volume difference of the island corresponding to the selected list member can be determined in the following manner. For each vertex of the island in the second 3D dental model, the closest distance to the first 3D dental model can be identified in the direction of the vertex normal. In this way, the back surface is excluded. Then, for each small facet of the island in the second 3D dental model, the average distance can be calculated based on the identified closest distances of its three vertices, and the obtained value can be multiplied by the surface area of ​​the small facet. Finally, the obtained volumes can be summed to determine the island volume difference. This method is particularly suitable for volume calculation of islands identified on relatively flat tooth surfaces (such as buccal and / or lingual surfaces).

[0051] The island volume differential can provide users with valuable insights into a patient's overall oral health as it can accurately quantify changes in dental conditions over time. Based on this valuable information, dental professionals can assess the progression of a dental condition or its rate of change and subsequently design appropriate dental treatment.

[0052] In one example, the severity factor value determined for at least one of the plurality of regions may indicate an absolute change in at least one dental condition between a first dental 3D scan of the subject and a second dental 3D scan of the subject. For example, the change in tooth wear for a particular region expressed in cubic millimeters may be an absolute change. Alternatively or additionally, the severity factor value determined for at least one of the plurality of regions may indicate a rate of change in at least one dental condition between a first dental 3D scan of the subject and a second dental 3D scan of the subject.

[0053] In one example, at least a first 3D scan data of a subject is obtained by scanning the subject's oral cavity using an intraoral scanner. The data represents the teeth and gums of the subject and can be used to generate a 3D dental model.

[0054] In an embodiment, a method according to the present disclosure may include displaying annotations on the 3D dental model based on user input. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Various aspects of the present disclosure may be best understood from the following detailed description in conjunction with the accompanying drawings. These drawings are schematic and simplified for clarity, and they only show details to improve understanding of the claims, while other details are omitted. The individual features of each aspect may be combined with any or all features of the other aspects, respectively. These and other aspects, features and / or technical effects will be apparent and clarified from the drawings described below, in which:

[0056] Figure 1A 3D dental model of the mandible is shown;

[0057] Figure 2 A method according to the present disclosure is shown;

[0058] Figure 3 A 3D dental model with islands represented by a heat map is shown;

[0059] Figure 4 A digital dental chart is shown;

[0060] Figure 5 A dental scanning system is shown. DETAILED DESCRIPTION

[0061] In the following description, reference is made to the accompanying drawings, which show by way of illustration how the invention may be practiced.

[0062] Figure 1A 3D dental model 100 of a subject's jaw is shown, wherein individual teeth 101 and surrounding gums 102 are shown. The term 3D model may refer to a three-dimensional model of teeth and gums, and may include topological surface information. The 3D dental model may represent the lower jaw, the upper jaw, or the lower jaw and the upper jaw, and may be generated based on at least a first dental 3D scan data of the subject received. The first 3D scan data may be a series of 2D images. The first 3D scan data may include texture data (e.g., color data or fluorescence data) and may be obtained by scanning the subject's oral cavity (e.g., using an intraoral 3D scanner at a first point in time). This process may also be referred to as obtaining a first scan. In some examples, the series of 2D images may include at least one infrared 2D image. Then, a first 3D dental model may be generated based on the first 3D scan data. If the first scan is the only scan obtained, the generated 3D dental model is the first 3D dental model. As will be described in more detail later, a dental condition, such as caries, may be detected on the 3D dental model 100 generated from a single scan. The subject or patient may decide to obtain a second scan of the oral condition at a second time point that is later than the first time point (e.g., one year later than the first time point). In this case, second 3D scan data is obtained, and a second 3D dental model may be generated based on the second 3D scan data. In this case, the 3D dental model 100 is generated based on the first and second 3D scan data. The 3D dental model may be a combination of the first and second 3D dental models, such that the second 3D dental model is superimposed on the first 3D dental model. The first and second 3D dental models are aligned with each other. The 3D dental model 100 generated based on the first and second 3D scan data can be used to directly compare the scan data and detect dental conditions, such as caries and / or tooth wear. The 3D dental model 100 can also be generated based on more scans than just the first and second scans.

[0063] Using infrared light during dental scanning can be advantageous because teeth are highly transparent at infrared wavelengths. In addition, infrared light can be scattered by caries. This makes infrared light particularly suitable for detecting interproximal caries, which can otherwise only be detected by X-rays.

[0064] The 3D dental model 100 can be represented as a polygonal 3D mesh, most commonly a triangular mesh. A triangular mesh consists of points called vertices and edges connecting the vertices. The edges define faces or facets of the mesh, which can be triangular. Alternatively, the 3D dental model can be represented as a point cloud or any other format suitable for 3D object representation.

[0065] Figure 1Also shown is an island 103 with a dental condition, in which case tooth wear is visible on the molars and incisors. Tooth wear can be represented by a visual indicator, which can be, for example, Figure 1 1. The heat map shown. Different colors are used to indicate different severity of tooth wear. The vertical bar 106 can be used as a legend for reading the heat map and can indicate which color represents which degree of tooth wear. The value on the vertical bar 106 can be displayed in millimeters and represents the distance between the vertices of the aligned first and second 3D dental models.

[0066] Figure 2 The steps of a computer-implemented method for identifying islands of interest according to the present disclosure are shown. A first step 201 of the method comprises receiving at least first dental 3D scan data of a subject. The dental 3D scan data may be a series of 2D images acquired by an intraoral 3D scanner. The dental 3D scan data may include a depth map image having information related to the distance of the object from a viewpoint. The dental 3D scan data may also include texture data, such as color data and / or fluorescence data.

[0067] Then, in step 202, a 3D dental model 300 may be generated using at least the first 3D dental scan data. The process of generating the 3D dental model 300 representing the teeth and gums of the subject may include reconstructing a series of images into a three-dimensional form. If a second dental 3D scan data is received in addition to the first dental 3D scan data, the 3D dental model 300 is generated based on the first and second received dental 3D scan data. For example, a first 3D dental model may be generated based on the first dental 3D scan data, and a second 3D dental model may be generated based on the second dental 3D scan data. Then, the 3D dental model 300 may include a combination of the first and second 3D dental models overlapping each other.

[0068] In one example, such an overlap of the first and second 3D dental models can be achieved by applying a commonly used iterative closest point (ICP) algorithm, which iteratively minimizes the difference between the points (vertices) of the first and second 3D dental models. The algorithm iteratively modifies the translation and rotation transformations required to minimize the distance between the two 3D dental models. The input to the algorithm is the coordinates of the points from the first and second 3D dental models, i.e., the coordinates of the vertices, an initial estimate of the transformation, and a criterion for stopping the iteration. The output of the algorithm is an improved transformation, which produces a 3D dental model 300 consisting of the overlapped first and second 3D dental models.

[0069] Once the 3D dental model 300 is generated, a plurality of regions indicative of the presence of at least one dental condition are identified in step 203. The dental condition may be, for example, one of caries, tooth wear, tartar or gingivitis.

[0070] An intraoral 3D scanner 525 can be used to detect caries by scanning the teeth, recording the fluorescence emitted from the fluorescent material in the cariogenic area of ​​the teeth, and processing the obtained scan data. For example, the presence of more red light in a certain part of the tooth compared to the reference indicates the presence of caries. Once generated, the 3D dental 300 model stores texture data, such as fluorescence and / or color data, in the vertices of the 3D mesh. The areas with caries on the 3D dental model 300 can then be identified by comparing the fluorescence data in the 3D mesh vertices with the reference data indicating the absence of caries. Reference data can be obtained by sampling values ​​from the texture data for each vertex or facet in the 3D mesh and generating a texture value distribution (e.g., in view of a histogram of the sampled texture values). The texture value distribution can include areas with dental conditions and vertices or faces of the 3D mesh that do not have dental conditions (i.e., healthy). Filtering can be applied by defining a minimum threshold value for texture intensity values ​​(e.g., a scalar value of 15). This filtering discards areas with dental conditions because they are characterized by low texture values ​​and allows the reference data to be defined.

[0071] The 3D dental model 300 can be generated based on the first and second 3D dental models aligned in the same coordinate system. The first and second 3D dental models can be segmented into different objects, such as individual teeth. The respective corresponding objects of the first and second 3D dental models can be aligned using the mentioned ICP algorithm.

[0072] When the models are aligned, areas with dental conditions (e.g., tooth wear) can be identified by calculating the distance between corresponding vertices in the first and second 3D dental models. For example, if the Euclidean distance between corresponding vertices is above a distance threshold (e.g., 0.3 mm), tooth wear can be identified for the area on the 3D dental model 300 that includes these two vertices.

[0073] In step 204, a severity factor value is determined for each of the plurality of regions, wherein the severity factor indicates a severity of at least one dental condition. For example, the severity of caries or tooth wear may be initial (low), moderate (medium), or severe (high). In the case of tooth wear, the distance between corresponding vertices in the first and second 3D dental models expressed in millimeters may be used as the severity factor value. In the case of caries, the output of a scoring function applied to texture data (e.g., color or fluorescence) may represent a severity factor value. In one embodiment, the scoring function may be expressed as:

[0074] f(R,G)=(RG) / (R+G)

[0075] Wherein, R represents the value of the red channel, and G represents the value of the green channel of the region obtained from the texture data (e.g., the fluorescence data of the 3D dental model 300). In the above function, the higher the ratio, the higher the severity of caries in the corresponding region. Other scoring functions may be applied, such as including only a single texture component of the region, such as the green channel. In another embodiment, the scoring function may include texture data and reference data of the region with caries.

[0076] In step 204, each of the plurality of regions may be marked with a visual indicator (e.g., a color). A color layer may be superimposed on each region, wherein the color is associated with a severity factor value determined for the region. For example, regions having severity factor values ​​corresponding to an initial (low) severity of the dental condition may be represented by green. Regions associated with a moderate (medium) severity may be represented by orange, and regions associated with a high severity may be represented by red.

[0077] In step 205, a plurality of islands 303 are obtained by grouping a plurality of regions on the 3D dental model 300 so that each island 303 includes adjacent regions indicating the presence of at least one dental condition. The term "island" may be understood as a surface area, a region of interest, or a volume on the 3D dental model 300, and may be composed of adjacent regions. The islands 303 on the 3D model 300 may have any shape and be characterized by their surface size and / or volume. For example, some regions of the islands 303 may indicate the presence of caries, while other regions of the same island may indicate the presence of tooth wear. Alternatively, all regions of an island 303 may indicate the presence of the same dental condition (e.g., tooth wear or caries). A common feature shared by all regions of the same island 303 is that they are adjacent to at least one other region of the island 303. Therefore, two adjacent regions (which may be two facets of a 3D mesh) share common edges and / or common vertices. By grouping adjacent regions together into islands 303, significant advantages may be obtained because global information about the subject's dental condition is created. The algorithm for grouping multiple regions into islands is as follows. When a region indicating the presence of at least one dental condition is identified, the algorithm can check whether the vertices of the identified region belong to another adjacent region that also indicates the presence of at least one dental condition. The two regions can then be assigned to a common island.

[0078] In step 206, the 3D dental model 300 may be displayed, for example, on a display of a laptop or tablet computer. In one embodiment, the 3D dental model 100 (eg, Figure 1 as shown) so that the complete model fits the display size. Figure 1In the case of , the 3D dental model 100 is a model of the subject's jaw, with an occlusal plane view. In another embodiment, the display step may occur such that the 3D dental model 300 is automatically adjusted for a particular island or group of islands to be displayed to the user, such as Figure 3 shown.

[0079] The display may be any display suitable for rendering a 3D dental model. Examples include a liquid crystal display (LCD), a light emitting diode (LED) display, etc. The display may include a touch screen interface allowing a user to interact with the display.

[0080] Figure 3 An enlarged portion of the 3D dental model 300 is shown, in this case showing portions of the upper and lower jaws, with the anterior incisors of the upper jaw in focus. Figure 3 To indicate a preview list

[0081] The user interface is displayed in the form of a horizontal bar 301. The preview list 301 may include multiple list members.

[0082] 302 , wherein each list member 302 is associated with an island 303 of the plurality of islands, such that a user can switch between islands 303 on the 3D dental model 300 by switching between the list members 302 . Figure 3 Tooth wear is shown in the form of a heat map, where different severity of tooth wear is indicated by different colors. Vertical bars 306 relate the colors used in the heat map to the amount of tooth wear expressed in millimeters and can be used to interpret the severity of tooth wear.

[0083] like Figure 3 As shown, the user can switch between different list members 302 by clicking on a "Previous" or "Next" button. In this case, the selected list member 302' can correspond to an island 303' on the incisor of the 3D dental model 300. This correspondence between list members 302 and islands 303 is advantageous because a limited number of list members associated with each identified dental condition are presented to the user. By switching through and checking all list members 302, the user can be confident that there are no unchecked identified dental conditions. The user can also switch between different list members 302 using a mouse "scroll" button or any other suitable user input method.

[0084] If the user selects a list member 302', the 3D dental model 300 may be automatically adjusted so that an island 303' corresponding to the list member 302' is brought into the field of view. This means that the 3D dental model 300 may be rotated, translated, and parts thereof may be enlarged or reduced. In this way, the island 303' may be displayed. Furthermore, at least a portion of the 3D dental model 300 may be made transparent. This may be advantageous if certain portions of the 3D dental model 300 block the user's view of an island 303 corresponding to one of the list members 302.

[0085] The island 303' associated with the list member 302' can be brought into the field of view as follows. The island 303' can be composed of multiple individual building blocks or regions, each of which indicates the presence of at least one dental condition. The regions can be triangles or facets of a 3D mesh. All vertices of the regions in the island 303' are characterized by their coordinates in 3D space. Then, a plane fitting can be performed on all vertices in the island 303' including the region, for example by using a least squares method, and the normal of the resulting plane is identified. The 3D dental model 300 can then be adjusted so that the normal of the resulting plane coincides with a direction perpendicular to the display surface. In this way, the island 303' is brought into the field of view.

[0086] At least one infrared (IR) image of one or more teeth associated with the displayed island 303' may be displayed. This may be advantageous because a user may examine the at least one IR image for the presence of dental conditions such as caries, particularly interproximal caries formed between teeth.

[0087] The preview list 301 may include list members 302 sorted according to a sorting criterion. In one embodiment, the sorting criterion may be the surface area of ​​the island. The surface area of ​​the island may be calculated as the sum of the areas of the various regions included in the island 303. If the region is a 3D mesh triangle, the area of ​​the region is calculated according to a formula for calculating the area of ​​a triangle based on known coordinate points. Then, the list member 302 corresponding to the island 303 with the largest surface area may appear as the first list member, the list member 302 corresponding to the island 303 with the second largest surface area may appear as the second list member, and so on. Therefore, the island 303 with the largest surface area will be presented to the user first. This means that the island 303 with the largest surface area will be brought into the field of view. By switching the browsing list, such as clicking the "next" button once, the island 303 with the second largest surface area will be presented to the user.

[0088] The sorting criterion may alternatively be an island importance factor value, which may be defined as a function of the island surface area and the severity factor values ​​of the regions included in the island 303. The island importance factor value may be a scalar value. In one example, the severity factor value of the region in the island 303 may be the average distance between the vertices of the corresponding surfaces in the first and second 3D dental models. The average distance may then be multiplied by the surface area of ​​the region. This process may be repeated for all regions in the island 303. The island importance factor may then be derived as the sum of the resulting products of the average distance and the corresponding region surface. If the average distance is a negative value, tooth wear is indicated. In some examples, it may be beneficial to emphasize tooth wear, so the average distance with a negative value may be additionally multiplied by a weighting factor, such as a scalar value of 1.5. In another example, the island importance factor value may be obtained by multiplying the island surface area by the sum of the severity factor values ​​of the regions constituting the island 303.

[0089] The list member 302 corresponding to the island 303 having the highest island importance factor value may appear as the first list member. The list member 302 may be automatically identified, and the 3D dental model 300 may be adjusted so that the corresponding island 303 is brought into the field of view. The adjustment of the dental 3D model 300 may be performed automatically. The corresponding island 303 may be brought into the field of view by performing plane fitting on all vertices in the region included in the island 303 and identifying the normal of the obtained plane. The 3D dental model 300 may then be adjusted so that the normal of the obtained plane coincides with a direction perpendicular to the display surface.

[0090] In one embodiment, an optimized path of travel may be generated when adjusting the 3D dental model 300. In some cases, it may occur that consecutive list members 302 of the sorted preview list 301 correspond to islands 303 on the 3D dental model 300 that are relatively far away from each other. For example, an island 303 corresponding to a first list member 302 and an island 303 corresponding to a second list member 302 may be located on opposite sides of the 3D dental model 300. Switching between such list members 302 may be inefficient and confusing to the user because it may be difficult to track how the 3D dental model 300 is adjusted during the process. Similarly, switching between islands 303 on the 3D dental model 300 that are too close to each other may also be inefficient because the user may not notice how the 3D dental model 300 is adjusted. In this case, it may be necessary to first zoom out the 3D dental model 300 and then perform translation and rotation. Then, zoom in on the 3D dental model 300 so that the selected island 303 is brought into the field of view.

[0091] By having an optimized path of travel, the adjustment of the 3D dental model 300 may be improved. When the user switches between list members 302 by clicking a "next" button, the 3D dental model 300 may be adjusted so that the island 303 closest to the previously displayed island is brought into the field of view. This means that one or more list members 302 may be rearranged to avoid large adjustments to the 3D dental model, i.e. large rotations and translations. The optimized path of travel may be created by rearranging the list members 302 in the preview list 301. For example, the preview list 301 may be rearranged so that if the island 303 associated with the third list member 302 is closest to the island 302 on the 3D dental model 300 corresponding to the first list member 302, the second list member 302 and the third list member 302 swap positions in the preview list 301. This approach has the advantage of performing a minimal amount of adjustment of the 3D dental model 300, i.e. a minimal amount of rotation and translation between the individual switching steps. The rearrangement of the list members 302 may be performed automatically based on a rearrangement criterion. In the above case, the rearrangement criterion is the distance between the islands 303 on the 3D dental model 300 .

[0092] Figure 4 A digital dental chart 400 is shown. Parameters such as island importance factor values ​​or island surface areas may be copied into the digital dental chart 400. The digital dental chart 400 may include information about the identified dental conditions associated with the tooth representations 401. For example, island surface areas may be displayed, indicating surfaces affected by caries. Different tooth representations 401 in the digital dental chart 400 may be colored according to the colors used when marking the 3D dental model 300. The digital dental chart 400 is presented in the format of a universal numbering system, but other formats such as FDI World Dental Federation (ISO) symbols or Palmer notation may also be applied.

[0093] Figure 5 A dental scanning system 500 is shown that includes means for performing the method 200. The dental scanning system 500 may include a computer 510 that may have a wired or wireless interface to a server 515, a cloud server 520, and an intra-oral scanner 525.

[0094] The intraoral scanner 525 may be capable of recording at least first and second 3D dental scan data of a subject. The recorded at least first and second 3D dental scan data may include geometric and texture data of the teeth. The texture data may include color and / or fluorescence data.

[0095] In addition, the intraoral scanner 525 can be equipped with an infrared module and can record infrared data. The infrared module can include an infrared light source. The infrared data can be recorded at an infrared wavelength, such as a near-infrared wavelength of 800-2500nm. The infrared data can be in the form of an infrared 2D image.

[0096] The infrared 2D image may be associated with the 3D dental model 100 , 300 and may be displayed together with the display of the 3D dental model 100 , 300 .

[0097] The dental scanning system 500 may include a data processing device configured to perform the method according to one or more embodiments of the present disclosure. The data processing device may be part of a computer 510 .

[0098] The non-transitory computer-readable storage medium may include instructions, which, when executed by a computer, cause the computer to perform a method according to one or more embodiments of the present disclosure.

[0099] Additionally or alternatively, the non-transitory computer-readable storage medium may include instructions that, when executed by the computer, cause the computer to render a graphical user interface configured to load and visualize the 3D dental model 100, 300 having the plurality of islands 303. The computer may also render a preview list 301. The preview list 301 may include a plurality of list members 302, wherein each list member 302 is associated with an island 303 of the plurality of islands, such that a user may switch between islands 303 on the 3D dental model 300 by switching between the list members 302.

[0100] The computer program product may be implemented in a non-transitory computer readable medium. The computer program product may include instructions, which, when executed by a computer, cause the computer to perform a method according to any of the embodiments presented herein.

[0101] Although some embodiments have been described and shown in detail, the present disclosure is not limited to these details, but can also be implemented in other ways within the scope of the subject matter defined in the appended claims. In particular, it should be understood that other embodiments can be utilized and structural and functional modifications can be made without departing from the scope of the present invention.

[0102] A claim may refer to any of the preceding claims, and "any" should be understood to mean "any one or more" of the preceding claims.

[0103] It is contemplated that structural features of the apparatus described above (whether in the detailed description or in the claims) may be combined with steps of the method when appropriately substituted by corresponding processes.

[0104] Unless expressly stated otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms (i.e., have the meaning of "at least one"). It should also be understood that the terms "include", "comprises", "contains" and / or "comprising" when used in this specification specify the presence of stated features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0105] It should be understood that throughout this specification, references to "one embodiment" or "embodiment" or "aspect" or features included in a "possible" form mean that the specific features, structures, or characteristics described in connection with the embodiment are included in at least one embodiment of the present disclosure. In addition, specific features, structures, or characteristics may be combined in one or more embodiments of the present disclosure as needed. The previous description is provided to enable those skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects.

Claims

1. A computer-implemented method for identifying islands of interest (303) on a 3D dental model (100, 300), the method comprising the following steps: - receiving at least first dental 3D scan data and second dental 3D scan data of a subject, the second dental 3D scan data being acquired at a later time than the first dental 3D scan data; - generating a 3D dental model (100, 300) based on the received at least first dental 3D data and second dental 3D data of the subject; - identifying a plurality of regions on the 3D dental model (100, 300), each region of the plurality of regions indicating the presence of at least one dental condition; - determining a severity factor value for each of the plurality of regions, the severity factor value being indicative of a severity of the at least one dental condition; - marking each of the plurality of regions with a visual indicator on the 3D dental model (100, 300), wherein the visual indicator is selected based on the determined severity factor value of the region; - obtaining a plurality of islands (303) by grouping the plurality of regions on the 3D dental model (100, 300) such that each island comprises adjacent regions indicating the presence of the at least one dental condition; - displaying the 3D dental model (100, 300) having the plurality of islands (303); - displaying a user interface in the form of a preview list (301), the preview list (301) comprising a plurality of list members (302), wherein each list member (302) is associated with an island (303) of the plurality of islands (303), so that a user can switch between islands (303) on the 3D dental model (100, 300) by switching between the list members (302), and further comprising when a user selects a list member (302') from the preview list (301): - automatically adjusting the 3D dental model (100, 300) so that the island (303') corresponding to the selected list member (302') is brought into the field of view; - calculating the island volume difference value of the island (303') corresponding to the selected list member (302'), and -Displaying the island volume difference value of the island (303') corresponding to the selected list member (302').

2. The method according to claim 1, wherein: The at least one dental condition is caries, and wherein identifying a plurality of regions on the 3D dental model (100, 300), each region of the plurality of regions indicating the presence of caries, comprises: - Comparing the fluorescence data in the vertices of the 3D mesh of the 3D dental model (100, 300) with reference data indicating the absence of caries.

3. The method according to claim 2, wherein: The reference data indicating the absence of dental caries is obtained by: - For each vertex or facet in the 3D mesh, sample a value from the texture data; - generating a texture value distribution including areas with caries and healthy areas; - Define a minimum threshold for the texture value distribution to separate areas with caries from healthy areas.

4. The method according to claim 3, wherein: The minimum threshold for the texture value distribution is a scalar value of 15.

5. A method according to any preceding claim, wherein: The at least one dental condition is tooth wear, and wherein identifying a plurality of regions on the 3D dental model (100, 300), each region of the plurality of regions indicating the presence of tooth wear, comprises: - calculating the distances between corresponding vertices in the first 3D dental model and the second 3D dental model when the models are aligned; - If the Euclidean distance between the corresponding vertices is above a distance threshold, identifying tooth wear of a region on the 3D dental model (100, 300) including the corresponding vertices.

6. The method according to claim 5, wherein: The distance threshold is 0.3 mm.

7. A method according to any preceding claim, wherein: The area of ​​islands (303') indicates the presence of the same dental condition.

8. The method according to any one of the preceding claims 1 to 6, wherein: The areas of the islands (303') indicate the presence of different dental conditions.

9. A method according to any preceding claim, wherein: Grouping a plurality of regions on the 3D dental model (100, 300) such that each island (303') includes adjacent regions indicating the presence of the at least one dental condition, comprising: - identifying an area indicative of the presence of said at least one dental condition; - evaluating whether a vertex of the identified region belongs to another adjacent region also indicating the presence of said at least one dental condition; - The area and the adjacent areas are assigned to the island based on the evaluation (303').

10. A method according to any preceding claim, wherein: Automatically adjusting the 3D dental model (100, 300) includes fading out a portion of the 3D dental model (100, 300) except for the island (303') brought into the field of view.

11. A method according to any preceding claim, wherein: Automatically adjusting the 3D dental model (100, 300) includes configuring the islands (303') brought into the field of view to flash.

12. A method according to any preceding claim, wherein: Automatically adjusting the 3D dental model (100, 300) includes displaying the outline of the island (303') brought into the field of view.

13. A method according to any preceding claim, wherein: The island volume difference of the isolated island (303') indicates the volume change of the isolated island (303') on the 3D dental model (100, 300).

14. A method according to any preceding claim, wherein: Each region is a small face, and wherein the island volume difference of the island (303') is obtained by: - Calculate the signed volume of the tetrahedron formed by connecting the vertices of the facets in the island (303') with any point and sum the calculated volumes.

15. A method according to any preceding claim, wherein: Generating a 3D dental model (100, 300) based on at least first dental 3D data and second dental 3D data of a subject received comprises: - generating a first 3D dental model based on the first dental 3D scan data; - generating a second 3D dental model based on the second dental 3D scan data; - Overlaying said first 3D dental model and said second 3D dental model.

16. The method according to claim 15, wherein: Each region is a small face, and wherein calculating the island volume difference value of the island (303') includes: - identifying boundary facets of the island surface on the second 3D dental model; - for each identified boundary facet, identifying the closest facet on said first 3D dental model; - connecting the identified nearest facets to form a closed path defining an inner surface and an outer surface on said first 3D dental model; - facets defining said inner surface; - defining a closed volume of facets by connecting boundary facets on the second 3D dental model with corresponding nearest facets on the first 3D dental model; - for each facet in the closed volume of facets, calculate the signed volume of the tetrahedron defined by the three vertices of the facet; -Sum the signed volumes.

17. The method according to claim 16, wherein: Identifying boundary facets of the island surface on the second 3D dental model includes identifying facets having fewer than three adjacent facets indicating the presence of a dental indication.

18. A method according to claim 16 or 17, wherein: Defining the facets of the interior surface includes using a flood fill algorithm.

19. The method according to any of the preceding claims 14 to 18, wherein: The island (303') comprises the incisal or proximal tooth surface.

20. The method according to any one of the preceding claims 1 to 13, wherein: The calculation of the island volume difference value of the island (303') includes: - for each vertex of the island surface on the second 3D dental model, identifying the closest distance to the first 3D dental model; - for each facet of the island surface on the second 3D dental model, calculating an average distance based on the identified closest distances, and multiplying the average distance by the surface area of ​​the facet to obtain a unit volume; -Sum the unit volumes obtained.

21. A method according to any preceding claim, wherein: Automatically adjusting the 3D dental model (100, 300) includes rotating, translating, enlarging at least a portion of the 3D dental model (100, 300) and / or making at least a portion of the 3D dental model (100, 300) transparent.

22. The method according to any of the preceding claims, further comprising automatically sorting the list members (302) in the preview list (301) based on a sorting criterion, wherein: The ranking criteria are island surface areas and / or island importance factor values.

23. The method according to claim 22, wherein: The surface area of ​​the island is determined as the sum of the areas of the regions constituting the island (303).

24. The method according to claim 22 or 23, wherein: The island importance factor value is a function of the island surface area and the severity factor value of the region constituting the island.

25. The method according to any one of the preceding claims 22 to 24 further comprises automatically identifying a list member (302) corresponding to an island (303) having a highest importance factor value and adjusting the 3D dental model (100, 300) so that the island (303) corresponding to the identified list member (302) is brought into the field of view.

26. The method according to any one of the preceding claims 22 to 25, further comprising, when a user selects a list member (302') from the preview list (301): - adjusting the 3D dental model (100, 300) so that the island (303') corresponding to the selected list member (302') is brought into the field of view, and -Shows the island surface value for the island corresponding to the selected list member.

27. The method according to any of the preceding claims, further comprising copying the island importance factor value and / or the island surface area into a digital dental chart (400).

28. The method according to any of the preceding claims, further comprising displaying at least one infrared image of one or more teeth associated with the island (303').

29. The method according to any of the preceding claims, further comprising generating an optimized path of travel when adjusting the 3D dental model (100, 300).

30. The method according to claim 29, wherein: The optimized path of travel includes scaling down the 3D dental model (100, 300) prior to performing the translation and rotation.

31. The method according to claim 29, wherein: The optimized path of travel includes adjusting the 3D dental model (100, 300) so that the island (303') closest to the previously displayed island is brought into the field of view.

32. The method according to claim 29, wherein: The optimized path of travel includes rearranging the preview list (301) so that a minimum amount of adjustments to the 3D dental model (100, 300) are performed between each switching step.

33. The method according to claim 32, wherein: The rearrangement is performed automatically based on the rearrangement criteria.

34. The method according to claim 33, wherein: The rearrangement criterion is the distance between islands (303) on the 3D dental model (100, 300).

35. A computer program product embodied in a non-transitory computer readable medium, the computer program product comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 34.

36. A non-transitory computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 34.

37. A dental scanning system (500) comprising a data processing device configured to perform the method according to any one of claims 1 to 34.

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