Method and system for comparing dental digital 3D models

Abstract

A computer-implemented method for comparing digital 3D dental models is disclosed, the method comprising: receiving a first digital 3D dental model representing a dental condition at a first time; receiving a second digital 3D dental model representing the dental condition at a second time, the second time being later than the first time. Further, the method comprises generating a difference map based on the first and second digital 3D dental models, wherein generating the difference map comprises: obtaining values of geometric differences between the first and second digital 3D dental models; identifying a maximum value of the geometric differences from the values of the geometric differences; generating a color scale comprising a plurality of discrete colors associated with the values of the geometric differences, wherein colors in the plurality of discrete colors are separated by a color scale threshold, and wherein the color scale threshold is generated based on the maximum value of the geometric differences; and assigning the plurality of discrete colors to the values of the geometric differences. The method further comprises displaying the difference map to visually highlight the values of the geometric differences between the first and second digital 3D dental models.

Description

Technical Field

[0001] The present invention relates to a method and system for comparing digital 3D dental models that represent patient teeth at different points in time. Background Technology

[0002] The development of intraoral scanning technology has played a crucial role in the transformation to modern digital dentistry. Using a 3D intraoral scanner (IOS), dentists can accurately and quickly capture a patient's dental condition, which can then be visualized on a monitor as a digital three-dimensional (3D) dental model. The resulting digital 3D dental model can thus serve as a digital impression of the teeth and gums, offering numerous advantages compared to traditional physical dental impressions.

[0003] The significant advantages of using an intraoral scanner lie in the accuracy and precision of digital 3D dental models, which are far superior to traditional physical impressions. A series of digital 3D dental models of the same patient's dental condition can be obtained over a period of time. Therefore, the accuracy of these digital 3D dental models allows for highly precise comparisons between them, enabling the identification of various changes in the dentition, including the detection and tracking of changes in tooth and / or gingival movement and tooth shape over time.

[0004] These identified changes can be visually communicated to the user. One challenge currently faced by tools for identifying and presenting changes in digital 3D dental models is that these changes are presented according to predefined rules set in the software. Specifically, current tools and methods for visually representing the severity of identified changes are ill-suited to the specific circumstances of the digital 3D dental models being compared. Instead, these existing methods are based on predefined, rigid assumptions and generally perform suboptimally in diverse scenarios. In some cases, users may be able to adjust these tools to tailor existing solutions to their specific needs, but this requires ongoing execution over time and can be burdensome. Furthermore, users need a deep understanding of the tools to adjust the parameters of existing solutions. Moreover, existing solutions lack feedback mechanisms to inform users whether their manual adjustments are optimal, such as regarding scan data quality or the variability of digital 3D dental models. All these challenges can lead to improper parameter settings in comparison tools, preventing users from properly extracting clinically valuable information. These issues can result in suboptimal analysis of the compared 3D digital models or the omission of important changes.

[0005] This invention aims to address the aforementioned challenges and proposes an adaptive comparison tool for identifying and presenting relevant variations, specifically tailored for the digital 3D models being compared. The proposed solution provides a seamless user experience, eliminating the need for manual adjustments to comparison parameters. Furthermore, it delivers accurate and intuitive results for comparing digital 3D dental models in a time-efficient manner. Summary of the Invention

[0006] In one embodiment, a computer-implemented method for comparing digital 3D dental models is disclosed, the method comprising: - Receive a first digital 3D dental model representing the dental condition at a given moment; - Receive a second digital 3D dental model representing the dental condition at a second time point, where the second time point is later than the first time point; - Generate a difference map based on a first digital 3D dental model and a second digital 3D dental model, wherein the generated difference map includes: - Obtain the values ​​of the geometric differences between the first digital 3D dental model and the second digital 3D dental model; - Identify the maximum value of the geometric difference from the values ​​of the geometric differences; - Generate a color scale that includes multiple discrete colors associated with values ​​of geometric difference, wherein the colors in the multiple discrete colors are separated by a color scale threshold, and further wherein the color scale threshold is determined based on the maximum value of the geometric difference; - Assign multiple discrete colors to values ​​of geometric difference; and - Display a difference map to visually highlight the values ​​of geometric differences between the first and second digital 3D dental models.

[0007] In this disclosure, the term "3D" refers to the term "three-dimensional". The term "digital 3D dental model" refers to a computer-generated digital three-dimensional representation of a patient's dental condition. Such a digital 3D dental model can accurately correspond to the patient's actual dental condition. This means that dental objects such as teeth, tooth surfaces, restorations, and / or gingiva on the digital 3D dental model can correspond to objects in the actual dental condition.

[0008] Digital 3D dental models can be constructed by the processor of a dental scanning system based on scan data collected during intraoral scanning. During intraoral scanning, an intraoral 3D scanner can be used to scan a patient's dental condition, including teeth and gums. In this disclosure, the intraoral 3D scanner is also referred to as an intraoral scanner (IOS). Digital 3D dental models can be stored in the memory of a computer system, for example in Standard Trigonometric Language (STL) format or any other format used for displaying or printing 3D objects.

[0009] The processor can receive or access digital 3D dental models. Digital 3D dental models are typically displayed on the screen of a dental scanning system as a 3D mesh representing the surface of the teeth and gingival tissue in a dental condition. The 3D mesh can consist of individual facets, such as triangular facets, and each facet can, for example, include three interconnected vertices. Alternatively, digital 3D dental models can be displayed as a point cloud including points, a graph including nodes and edges, a volumetric representation including voxels, or any other suitable 3D representation.

[0010] The method may include receiving a first digital 3D dental model representing the dental condition at a first moment. For example, this first digital 3D dental model may be generated based on scan data obtained during a patient's first visit to a dental clinic. Features such as tooth shape and / or the relative positions of teeth can then be obtained and reflected in the first digital 3D dental model, which may also be referred to as a baseline model or baseline scan.

[0011] This method may include receiving a second digital 3D dental model representing the dental condition at a second time point, later than the first. For example, the second digital 3D dental model may be generated based on scan data obtained during subsequent visits to a dental clinic, such as within a timeframe of six months to one year after the initial visit. During this period, the shape of some teeth may have changed and / or the teeth may have moved compared to their baseline position at the time of the initial visit. Changes in tooth shape may be due to tooth wear, tooth fracture, and / or plaque accumulation. Furthermore, changes in soft tissue (gingival) movement may be observed at subsequent visits compared to the initial visit. These changes in gingival movement may be due to gingival inflammation or gingival recession, and it is important to record and accurately measure both.

[0012] The method may further include generating a difference map based on a first digital 3D dental model and a second digital 3D dental model. The difference map may include an overlaid digital 3D dental model for visualizing the differences between the first and second digital 3D dental models. The difference map may also include color scales to interpret the visualized differences on the overlaid digital 3D dental models.

[0013] Typically, a difference map of two 3D models is a visual representation used to compare two 3D datasets. Differences between two 3D models can be highlighted by calculating the differences in spatial or attribute values ​​at each point. This process generates a new map, or a new 3D model, showing the different locations and ways the two 3D models differ. A difference map can show the magnitude of the difference at each point in 3D space, and (if needed) the direction of the difference. This is often represented using color coding, where different colors are used to highlight areas of greater or lesser variation. By generating a difference map, the severity of the differences between a first and second digital 3D dental model can be assessed.

[0014] Generating a difference map may include obtaining the values ​​of the geometric differences between a first digital 3D dental model and a second digital 3D dental model. This can be done by subtracting the first and second digital 3D dental models from each other, i.e., subtracting the second digital 3D dental model from the first digital 3D dental model, or vice versa. The values ​​of the geometric differences may be represented only as positive numbers, or they may be represented as both positive and negative numbers, where negative numbers indicate the direction in which the difference / change occurs is opposite to the direction of the difference / change represented by positive numbers.

[0015] Furthermore, generating a difference plot may include identifying the greatest value among the geometric differences. The greatest value may be the global maximum value among the geometric differences. For example, if the differences are represented only as positive numbers, the greatest value may be the maximum value among the geometric differences. If the differences are represented as both positive and negative numbers, the greatest value may be the larger of the absolute maximum and absolute minimum values ​​among the geometric differences. Identifying the greatest value may include identifying the data boundary that contains the majority of the geometric differences. To do this, a portion of the geometric differences with excessively large absolute values ​​(outlier data) may be removed. Therefore, it is advantageous to identify outlier data to exclude it from the identification of the greatest value. This will be discussed further in this disclosure.

[0016] Generating the difference map may also include generating a color scale that includes multiple discrete colors associated with the values ​​of the geometric difference, wherein the colors among the multiple discrete colors are separated by a color scale threshold. The color scale threshold may be determined based on the maximum value of the geometric difference. The color scale threshold may be those values ​​of the geometric difference where the color transitions among the multiple discrete colors occur. The multiple discrete colors may be assigned to the values ​​of the geometric difference.

[0017] Generating difference maps in this manner allows for the creation of individually customized comparison tools for a specific pair of compared digital 3D dental models. The resulting difference maps provide an overview of the severity of geometrical differences for a specific situation and offer contextual information for the analyzed dental condition, thus possessing significant clinical value. Furthermore, the color-coding of the difference maps according to this disclosure eliminates the need for manual threshold recalibration, as the threshold is automatically set once the maximum geometrical difference is known. This significantly saves time and effort, allowing users to focus more on analyzing the results of the difference maps rather than spending time configuring suboptimal ones. In summary, the threshold settings and color assignments in the difference maps according to this disclosure are automatically adjustable and specific to each pair of compared digital 3D dental models. The adjustability of the difference maps according to this disclosure is another advantage, as users can use universal comparison tools regardless of the nature of the geometrical differences in the compared digital 3D dental models.

[0018] The method may also include displaying a difference map to visually highlight the values ​​of geometric differences between the first and second digital 3D dental models. This allows the severity of the assessment of the differences between the two digital 3D dental models to be communicated to the user.

[0019] In one embodiment, generating a difference map may include generating an overlaid digital 3D dental model by aligning a first digital 3D dental model and a second digital 3D dental model. Alignment may include global (scan level) alignment of the first and second digital 3D dental models, or local (tooth level) alignment of the first and second digital 3D dental models. As a result of local alignment, corresponding teeth in the first and second digital 3D dental models are more accurately aligned to each other compared to global alignment. Aligning the first and second digital 3D dental models may include, for example, using an Iterative Closest Point (ICP) algorithm and / or using a separate coordinate system for the teeth, referred to as tooth pose. Corresponding teeth in the first and second digital 3D dental models may refer to teeth with the same Universal Numbering System (UNN) dental markers.

[0020] Alignment can be understood as the rigid alignment of two digital 3D dental models in a common three-dimensional space.

[0021] The method may also include determining the value of the geometric difference between a first digital 3D dental model and a second digital 3D dental model on a superimposed digital 3D dental model. The geometric difference can be the distance between corresponding points in the first and second digital 3D dental models. A corresponding point can be the closest point between the first and second digital 3D dental models. These values ​​may be represented only as positive numbers, or they may be represented as both positive and negative numbers. For example, in some cases, a positive number may be more relevant to reflecting the change, such as when plaque accumulates on the teeth; or a negative number may be more relevant, such as when tooth wear leads to loss of tooth material.

[0022] Displaying a difference map may include showing a first digital 3D dental model, a second digital 3D dental model, or a combination of the first and second digital 3D dental models, to highlight the values ​​of geometric differences according to assigned color codes. It is preferable to display the second digital 3D dental model, or more generally, the most up-to-date digital 3D dental model, as this is likely to be most intuitive for the user.

[0023] In one embodiment, aligning a first digital 3D dental model and a second digital 3D dental model may include performing a global alignment, wherein the absolute value of the variation between the first and second digital 3D dental models can be determined. This global alignment may also be referred to as model-to-model alignment, scan-to-scan alignment, or jaw-to-jaw alignment. For example, this alignment can be performed by performing a best-fit transformation in which the centroids of corresponding teeth in the first and second digital 3D dental models overlap. The best-fit transformation is a rigid transformation that, when applied to the centroids of teeth in the first digital 3D dental model, minimizes the sum of squared distances to the centroids of teeth in the second digital 3D dental model. Because the best-fit transformation is computed at the jaw level rather than at individual tooth levels, it can be considered as jaw-to-jaw alignment. The obtained jaw-to-jaw alignment can be fine-tuned by performing an iterative nearest point (ICP) method considering selected teeth (e.g., molars) from both digital 3D dental models.

[0024] The absolute value of the variation between the first and second digital 3D dental models can be the variation in tooth movement and / or soft tissue (gingiva) movement. The absolute value of the variation can thus provide insight into whether the teeth are following the orthodontic prescription, or into the patient's gingivitis and / or gingival recession status.

[0025] When global alignment is performed, geometric differences can reflect variations in tooth positioning between the first and second digital 3D dental models. Additionally or alternatively, these geometric differences reflect variations in the gingival line (or margin line) between the first and second digital 3D dental models.

[0026] In one example, the maximum value of the geometric difference can be identified from the values ​​of the geometric differences based on the global alignment of the first and second digital 3D dental models. Since these values ​​can be only positive numbers, the maximum value of the geometric difference can be found by identifying the maximum value.

[0027] In another embodiment, aligning the first and second 3D dental models may include performing local alignment, wherein the teeth of the first 3D dental model are individually aligned with the corresponding teeth of the second 3D dental model. This can be achieved by aligning the tooth poses of all corresponding teeth in the first and second digital 3D dental models. Tooth pose refers to a coordinate system with the tooth centroid as the origin and its axes corresponding to the tooth principal axes. In this embodiment, the maximum value can be identified from the geometric differences based on the local alignment.

[0028] When performing local alignment, geometric differences can reflect the changes in tooth shape between the first digital 3D dental model and the second digital 3D dental model.

[0029] Typically, aligning a first digital 3D dental model and a second digital 3D dental model may involve using the Iterative Closest Point (ICP) algorithm. The ICP algorithm is an iterative algorithm that may involve multiple iterations, each iteration identifying corresponding tooth regions and minimizing the distance between the identified tooth regions, until the algorithm converges to the desired result.

[0030] The maximum value for identifying geometric differences can include: - Generate a frequency histogram of geometric difference values; - Calculate frequency variance based on frequency histogram; - Filtered values ​​of geometric differences are obtained by filtering the values ​​of geometric differences using at least a portion of the calculated variance; - Identify the minimum and maximum values ​​from filtered values ​​of geometric differences; and - Identify the absolute maximum value of the minimum and maximum values.

[0031] For example, the maximum value could be 0.6 mm, and the minimum value could be -0.65 mm. In this case, the absolute maximum value would therefore be -0.65. Thus, a frequency histogram can be used to identify outlier data. Once outlier data is identified, it can be filtered out, thus discarding it from the process of identifying the maximum geometric difference.

[0032] This filtering process can be performed to remove outliers and / or noisy data points, thereby finding filtered values ​​of geometric differences that represent useful boundaries of values. Filtering can be used only for the purpose of identifying the maximum geometric difference, while outlier data can still be displayed on the difference plot, for example, using the closest color on a color scale. For example, if value 2 is the maximum geometric difference and value 6 is an outlier, the area in the difference plot corresponding to the outlier can be displayed using the color on the color scale used to represent value 2.

[0033] Filtering the values ​​of geometric differences using at least a portion of the calculated variance may include excluding from the identification of the maximum value those values ​​of geometric differences that have a relevance probability below a first threshold. The first threshold may be at least a portion of the calculated variance. At least a portion of the calculated variance may be obtained as k * calculated variance, where the factor k is positive.

[0034] In one example, the color scales of the difference plot can be symmetrical. This means that the thresholds for the color scales can be determined within a range limited by the maximum value and the negative of the maximum value.

[0035] In one example, a color scale may include multiple subranges. These subranges are separated from each other by color scale thresholds. The step size within each of the multiple subranges may correspond to the measurement accuracy of an intraoral scanner used to scan dental conditions. The measurement accuracy of the intraoral scanner may be received, for example, by a processor used to perform the methods of this disclosure. The measurement accuracy of the intraoral scanner may be known in advance. All subranges within the multiple subranges may be equal, i.e., spanning the same range of values.

[0036] In one example, if the surface area covered by a sub-range among multiple sub-ranges on the difference map is greater than a second threshold, the number of sub-ranges can be increased. In some cases, sub-ranges may be wide, covering a large area of ​​the difference map, making it difficult to observe clinically significant differences on the difference map. To address this, the number of sub-ranges can be increased, for example, by further subdividing the sub-ranges into two or more sub-ranges. This ensures that a single sub-range represented by a single color among multiple discrete colors of the color scale does not obstruct the display of the severity representation of other relevant geometric differences. Therefore, the second threshold is related to the surface area of ​​the difference map. This second threshold can be predefined or can be adjusted by the user.

[0037] In one embodiment, the method may further include arranging a timeline in a graphical user interface (GUI) where overlaid digital 3D dental models are displayed. The timeline may indicate which digital 3D dental models are being compared, such as a first digital 3D dental model and a second digital 3D dental model. The timeline may be interactive and may allow the user to manually select the digital 3D dental models chosen for comparison.

[0038] The method disclosed herein may also include: - Receive user selections, which indicate additional digital 3D dental models for comparison; - Receive user selection, indicating a first or second digital 3D dental model for comparison with the additional digital 3D dental model; - Generate a difference map based on this additional digital 3D dental model and the first or second digital 3D dental model; and - Display a difference map to visually highlight the differences between this additional digital 3D dental model and the first or second digital 3D dental model.

[0039] The method may further include updating the color scale threshold based on the differences between the additional digital 3D dental model and the first or second digital 3D dental model. Thus, user selection of the digital 3D dental models for comparison triggers the generation of difference maps specifically tailored for those digital 3D dental models selected for comparison.

[0040] In one embodiment, a dental scanning system is disclosed, the system including a data processing device configured to perform the methods described in one or more embodiments of the present disclosure.

[0041] In another embodiment, a computer-readable storage medium is disclosed. This computer-readable medium (e.g., a non-transitory computer-readable medium) may carry instructions that, when executed by a computer, cause the computer to perform the methods described according to one or more embodiments of this disclosure.

[0042] Furthermore, according to this disclosure, a computer program product is disclosed that includes instructions that, when executed by a computer, cause the computer to perform any method according to this disclosure. Attached Figure Description

[0043] Figure 1 A first and second digital 3D model of the patient's teeth, which are to be compared, are shown. Figure 2 A flowchart of a method according to an embodiment of this disclosure is shown; Figure 3 A graphical user interface (GUI) is shown, which has a view of the difference diagram indicating the tooth shape changes between the first digital 3D dental model and the second digital 3D dental model; Figure 4 A graphical user interface (GUI) is shown, which has a view of the difference diagram indicating tooth movement and gum movement between a first digital 3D dental model and a second digital 3D dental model; Figure 5 A frequency histogram of geometric differences is shown in the difference plot used to identify outlier and / or noisy data; Figure 6 A graphical user interface (GUI) is shown, which has a view of the difference map of the teeth, indicating the changes in tooth shape between a first digital 3D dental model and a second digital 3D dental model; Figure 7 A dental scanning system according to this disclosure is shown; Figure 8 An example of a computer architecture for a computer capable of performing the methods of this disclosure is shown. Detailed Implementation

[0044] The following description will be made with reference to the accompanying drawings, which illustrate how the invention can be carried out.

[0045] Figure 1 A first digital three-dimensional (3D) dental model 100 of a patient's teeth and a second digital three-dimensional (3D) dental model 101 of the same patient's teeth are shown. The first digital 3D dental model 100 can be obtained by scanning the patient's teeth at a first time (e.g., during the first visit to a dental clinic) using a 3D scanner (e.g., using an intraoral 3D scanner 701). The second digital 3D dental model 101 can be obtained by scanning the patient's teeth at a second time later than the first time (e.g., during a subsequent visit to a dental clinic).

[0046] Between the first and second visits to the dental clinic, patients may have already developed dental conditions such as tooth wear, gum recession, or plaque buildup. Figure 1 In the second digital 3D dental model 101, the darker-colored surface 102 on the teeth represents the loss of tooth material due to tooth wear, with darker colors indicating more severe wear. Therefore, the surface geometries of the first and second digital 3D dental models 100 and 101 may differ. These differences in surface geometry may be due to changes in tooth anatomy caused by tooth wear, such as… Figure 1As shown. Additionally or alternatively, the differences in surface geometry between the first and second digital 3D dental models 100, 101 may be due to changes in soft tissue (gingival) movement and / or changes in tooth movement during the time interval from the first time to the second time. Gingival movement can be observed by watching the movement of the gingival margin (i.e., the distal edge of the gingiva that surrounds the tooth in a loop-like manner). Other dental conditions, such as the accumulation of plaque or tartar, may additionally cause changes in the geometry of the first and second digital 3D dental models 100, 101. Figure 1 Only the patient's maxilla is shown, but the first and / or second digital 3D dental models 100, 101 may additionally or alternatively include the mandible.

[0047] To accurately quantify and visualize changes in a patient's dental condition, it may be necessary to compare a first digital 3D dental model 100 and a second digital 3D dental model 101. This is required for diagnostic purposes, such as determining the presence or progression of dental conditions such as tooth wear, caries, plaque, tooth cracks, gingivitis, and / or gingival recession. Comparison of the two digital 3D dental models 100 and 101 may also be necessary to detect tooth movement for planning orthodontic treatment, assessing orthodontic progress, and / or planning other dental procedures.

[0048] Figure 2 A flowchart of a method for comparing digital 3D dental models according to an embodiment of the present disclosure is shown. In step 201, for example, a first digital 3D dental model 100 and a second digital 3D dental model 101 may be received by the processor of a dental scanning system 700. These two digital 3D dental models may be received based on user selection or may be automatically loaded into an algorithm for comparing digital 3D dental models. For example, after completing an intraoral scan, the method for comparing digital 3D dental models may be automatically triggered, during which scan data is collected to generate the second digital 3D dental model 101. At this time, the first digital 3D dental model 100 may already be stored in the memory of the dental scanning system 700.

[0049] exist Figure 2In step 202, a difference map can be generated based on the received first digital 3D dental model 100 and second digital 3D dental model 101. This difference map can also be called a difference color map because it uses multiple colors to visually highlight the differences between the compared digital 3D dental models. The difference map between the two 3D models can be generated by calculating the distance between corresponding points of the compared digital 3D dental models. For this purpose, the compared digital 3D dental models can be aligned with each other in a common digital 3D space. The difference map can show the magnitude of the difference at each point in the common digital 3D space, and can also show the direction of the difference if needed. Both the magnitude and direction of the difference can be visualized using color coding, where different colors highlight areas of greater or lesser variation.

[0050] Generating the difference map (step 202) may include sub-steps 202a to 202d, such as Figure 2 As shown. Sub-step 202a illustrates obtaining the value of the geometric difference between the first digital 3D dental model 100 and the second digital 3D dental model 101, for example, by subtracting the first digital 3D dental model 100 and the second digital 3D dental model 101 from each other. This means that the second digital 3D dental model 101 can be subtracted from the first digital 3D dental model 100, or the first digital 3D dental model 100 can be subtracted from the second digital 3D dental model 101.

[0051] Furthermore, in sub-step 202b, the maximum value of the geometric difference can be identified from the values ​​of the geometric differences. In sub-step 202c, a color scale 303 can be generated, which includes multiple discrete colors, the multiple discrete colors being determined by a color scale threshold (in...). Figure 3 The colors are separated by -t4 to t4. The threshold can be determined based on the maximum value of the geometric difference that can be identified. Discrete colors can be solid colors without any gradation. Color gradients can be used instead of discrete colors.

[0052] The effect of determining the color scale threshold based on the maximum value of the identified geometric differences is that color scale 303 is specific to the two digital 3D dental models 100 and 101 being compared. This is an advantage over existing color scales, which use preset thresholds that include preset minimum and maximum values. Such preset minimum and maximum values ​​do not provide an optimal solution for the various situations involving the digital 3D dental models to be compared. Therefore, such preset values ​​can confuse users and may lead to the inability to accurately locate and observe all clinically significant differences in each specific comparison case. In the solution disclosed herein, there is no pre-determined color scale, which could lead to the generation of non-optimized difference maps. Instead, the color scale of the difference map is specifically created and adjusted for the digital 3D dental models being compared. Figure 2 In sub-step 202d, multiple discrete colors can be assigned to values ​​of geometric difference.

[0053] exist Figure 2 In step 203, the difference map can be displayed, for example, on the display unit of the dental scanning system 700. This allows information about the determined differences between the two compared digital 3D dental models, along with an optimal indication of the severity of those differences, to be conveyed to the user.

[0054] Figure 3 A graphical user interface (GUI) 300 is shown, displaying a view of a difference map comparing corresponding teeth of a first digital 3D dental model 100 and a second digital 3D dental model 101. In this case, the difference map includes an overlaid digital 3D dental model 301 highlighting geometric differences in tooth shape between the teeth of the compared digital 3D dental models 100 and 101. These differences can be highlighted by applying a color overlay 302 to the areas in the overlaid digital 3D dental model 301 where differences are detected. Different colors can be applied depending on the value of the corresponding difference. The difference map may also include color bars 303 indicating colors used to represent the values ​​of geometric differences on the overlaid digital 3D dental model 301. Figure 3 In this case, the superimposed digital 3D dental model 301 shows the jaw in an occlusal state; however, the jaw may additionally or alternatively be shown in a state where the jaw is open so that the occlusal surface is displayed.

[0055] Figure 3 The superimposed digital 3D dental model 301 in the image shows the difference in tooth shape between two digital 3D dental models 100 and 101. Figure 3 The difference diagram does not show differences in tooth movement or gingival movement. This is because the first digital 3D dental model 100 and the second digital 3D dental model 101 are aligned at the level of individual teeth. Digital 3D dental models 100 and 101 can be segmented to identify dental objects, such as individual teeth. Subsequently, corresponding teeth in digital 3D dental models 100 and 101 can be aligned with each other. Corresponding teeth can be understood as teeth marked with the same Universal Numbering System / Notation (UNN).

[0056] Segmentation of digital 3D dental models 100 and 101 can be performed through a segmentation process that allows for the identification of different dental objects within the digital 3D dental models, such as individual teeth and / or surrounding gingiva. Individual teeth can be assigned tooth identifiers, for example, according to the Universal Numbering Notation (UNN), where the numbers 1 through 32 are assigned to human teeth. The segmentation process may include the use of algorithms such as Principal Component Analysis (PCA) or harmonic fields. The segmentation process may alternatively or additionally include the use of machine learning models.

[0057] To generate a color mark 303 for a superimposed digital 3D dental model 301, the following steps can be performed. The value of the geometric difference between a first digital 3D dental model 100 and a second digital 3D dental model 101 can be determined. Among these determined values, the maximum value of the geometric difference can be identified. For example, the maximum value of the geometric difference could be 2 mm, and the minimum value could be -1 mm. It can be agreed that a positive value of the geometric difference represents the accumulation of material on a single tooth, such as plaque accumulation over time. Furthermore, a negative value of the geometric difference can represent the loss of material on a single tooth, such as loss due to tooth wear or tooth fracture over time. Next, the absolute values ​​of the maximum and minimum values ​​can be compared. Then, the larger of the two can be selected as the maximum value of the geometric difference, and this can be selected as the highest threshold 304 of the color mark 303. Figure 3 The threshold t4 in the data. Therefore, in Figure 3 In the example, considering the aforementioned values ​​of 2 mm and -1 mm, the highest threshold 304 of color mark 303 can be assigned a value of 2 mm. The lowest value 305 of color mark 303 (threshold -t4) can be chosen as the negative of the highest value 304, which in this case can be a value of -2 mm. This makes color mark 303 symmetrical within its range, with the value 0 located at the center of color mark 303. Once the highest value 304 and the lowest value 305 are known, the other thresholds of color mark 303 (e.g., t3, t2, t1, t2, t3, t4, t5, t4, t5, t4, t5, t6, t7, t8, t9, t1, t2, t2, t3, t4, t5, t1, t2, t2, t3, t2, t3, t4, t5 ...6, t7, t8, t9, t1, t2, t2, t3, t2, t3, t2, t3, t4, t5, t2, t3, t2, t3, t4, t5, t2, t3, t4, t5, t2, t3, t4, t5, t2, t3, t4, -1 t -2 t -3 This can be automatically determined. The width of each sub-range 306 between the two thresholds in color stop 303 can be equal. The number of sub-ranges in color stop 303 can be predetermined. Figure 3 A total of 8 subranges 306 are shown. Instead of 8 subranges 306, 10 or more subranges can be used.

[0058] It can be observed that the highest value 304 and the lowest value 305 of color scale 303 are determined based on the geometric differences between the two compared digital 3D dental models, in this case, based on the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101. Therefore, the thresholds for color scale 303 are not predetermined. This characteristic offers several advantages. First, if the determined clinically significant differences fall outside the color scale range with preset boundaries, these values ​​can be captured and displayed on the difference map according to this disclosure. This allows users to identify and view serious conditions requiring their attention, thereby enhancing the clinical value of the difference map of this disclosure. Furthermore, once values ​​304 and 305 are determined, other thresholds between the highest value 304 and the lowest value 305 can be automatically determined. Therefore, these thresholds vary according to the aligned compared digital 3D dental models, eliminating any need for manual recalibration of the thresholds. This significantly saves time and effort, as users can focus more on analyzing the results of the difference map rather than spending time configuring the thresholds. Because the thresholds are determined for a specific pair of compared digital 3D dental models, the accuracy of data visualization and interpretation is improved. Furthermore, users can immediately see the relevant thresholds applied to the currently compared digital 3D dental models, making the graphical user interface 300 more intuitive overall.

[0059] exist Figure 3 On color scale 303, the two sub-ranges 306 surrounding the zero value represent the "no change" state, namely the sub-range between threshold 0 and t1, and the sub-range between threshold 0 and -t. -1 Subranges within these subranges. The positions on the superimposed digital 3D dental model 301 corresponding to the values ​​of geometric differences within these subranges may not be superimposed with color, but can instead be displayed in their corresponding natural colors. Alternatively, colors such as green can be used.

[0060] Figure 3 The color swatch 303 also makes the geometric difference greater than t4 and / or less than t. -4 The values ​​can be displayed on the difference graph, for example, using the colors corresponding to the uppermost subrange 306 or the lowermost subrange 306.

[0061] Figure 3A timeline 307 is also shown, with indicators 308 and 309 for the compared digital 3D dental models. Indicator 308 corresponds to the first digital 3D dental model 100 (S1 or scan 1), while indicator 309 corresponds to the second digital 3D dental model 101 (S2 or scan 2). Indicators 308 and 309 can be arranged chronologically, with older scans (here, S1) positioned to the left of timeline 307. This allows for a visual view of the compared digital 3D dental models and their corresponding timestamps. Users can hover over indicators 308 and 309 and, for example, in pop-up windows, obtain more information about the corresponding digital 3D dental model, including scan dates or an overview of dental conditions identified for a particular scan.

[0062] Users can decide to include other digital 3D dental models in the comparison tool according to this disclosure. Therefore, users can select additional digital 3D dental models for comparison with either the first digital 3D dental model 100 or the second digital 3D dental model 101. Users can make this selection by clicking indicator 308 or indicator 309. Based on user input (click), a library of available digital 3D dental models containing the additional model can be opened, allowing the user to select it. This additional digital 3D dental model can represent a dental condition at a different time, where the different time is later than the first time but earlier than the second time. This is just an example, as the different time could alternatively be earlier than the first time or later than the second time. Once the user selection is received, the overlaid digital 3D dental model 301 will be updated with the new data. Furthermore, as new maximum values ​​304 and minimum values ​​305 are determined, and other thresholds between the maximum and minimum values ​​304 and 305 are determined, the color scale 303 is updated accordingly. Timeline 307 can also be updated accordingly, showing which digital 3D dental models (scans) are being compared.

[0063] When a user selects a new pair of scans for comparison, color scale 303 can display an animated effect (typically lasting a few seconds) to indicate to the user that the threshold is being recalculated after the new scan is selected. This acts as a feedback mechanism to inform the user of the ongoing threshold adjustment process. This real-time or near real-time threshold recalculation can take into account the variability in the quality and / or geometric differences of the scan data. The variability in the size and / or geometric differences of the scan data increases the threshold calculation time.

[0064] In some cases, subrange 306 may be so wide that large surfaces of the difference map are covered by a single color, making it difficult to observe the distribution of the severity of geometric differences at a finer granular level. To address this issue, subrange 306 can be segmented; for example, each subrange 306 can be divided into two or more subranges. Figure 3 In the example, dividing subrange 306 into two subranges results in a total of eight new subranges on the portion of color swatch 303 with positive values ​​and eight new subranges on the portion of color swatch 303 with negative values. This ensures that a single subrange 306 represented by a single color does not represent a value across a geometric difference that crosses a threshold used to divide the subranges. This threshold used to divide the subranges may also be referred to as a second threshold and may be related to the surface area of ​​the superimposed digital 3D dental model 301. This second threshold may be predetermined. Alternatively, the threshold used to divide the subranges may be adjusted by the user.

[0065] Figure 4 A graphical user interface (GUI) 300 is shown, displaying a view of a difference diagram comparing a first digital 3D dental model 100 and a second digital 3D dental model 101 at the jaw level. The difference diagram may include an overlaid digital 3D dental model 301 highlighting geometric differences in tooth movement and / or gingival movement between the first and second digital 3D dental models 100 and 101. Figure 3 Similar to the difference map in the superimposed digital 3D dental model 301, these differences can be highlighted by applying a color overlay 302 to the locations where differences are detected. It can be seen that the color overlay 302 exists not only on the teeth of the superimposed digital 3D dental model 301 (representing tooth movement) but also on the soft tissue (gingiva) of the superimposed digital 3D dental model 301. Measurements of tooth movement can be associated with confirming patient occlusal function, diagnosing malocclusion, and monitoring orthodontic treatment progress. Measurements of soft tissue movement, such as gingival margin movement, can be associated with diagnosing gingival recession, gingivitis, or periodontal disease. Based on the identified values ​​of geometric differences, different colors in the color scale 303 can be applied to the superimposed digital 3D dental model 301. The superimposed digital 3D dental model 301 can be shown as being in occlusion, or as having one or both jaw occlusal surfaces displayed, such as... Figure 4 As shown in the example.

[0066] Figure 4 The superimposed digital 3D dental model 301 in the image shows the differences in tooth and / or gingival position between two digital 3D dental models 100 and 101. Figure 4The difference diagram does not show individual tooth shape differences. This is because, in this case, the alignment of the first digital 3D dental model 100 and the second digital 3D dental model 101 is performed at the scan level, which can be called global alignment. This global alignment can also be called model-to-model alignment, scan-to-scan alignment, or jaw-to-jaw alignment. For example, this type of alignment can be performed by performing a best-fit transformation in which the centroids of corresponding teeth in the first and second digital 3D dental models overlap. The best-fit transformation is a rigid transformation that, when applied to the centroids of teeth in the first digital 3D dental model, minimizes the sum of squared distances to the centroids of teeth in the second digital 3D dental model. This best-fit transformation can be considered as jaw-to-jaw alignment because it is calculated at the jaw level rather than at the level of individual teeth. The obtained jaw-to-jaw alignment can be fine-tuned by performing the Iterative Closest Point (ICP) method, considering selected teeth (e.g., molars) from both digital 3D dental models.

[0067] In order to generate Figure 4 The color mark 303 of the superimposed digital 3D dental model 301 in the example shown can be processed by performing the following steps. The value of the geometric difference between the first digital 3D dental model 100 and the second digital 3D dental model 101 can be determined. A maximum value and a minimum value can be identified from these determined values. For example, the maximum value could be 2 mm and the minimum value could be 0.4 mm. An agreement can be adopted that only the absolute value of the geometric difference is considered, thus generating a color mark 303 with only positive values ​​of geometric difference. Therefore, this maximum value is selected as the greatest value of the geometric difference. Therefore, the highest value 304 (t5) of the color mark 303 can be assigned a value of 2 mm. Once the highest value 304 is assigned, other thresholds of the color mark 303 (e.g., t4, t3, t2, t1) are automatically determined. In this case, the color mark 303 is not like... Figure 3 The case is symmetric about zero because only positive values ​​are considered. Each subrange 306 of the values ​​between two thresholds in color scale 303 can be equal. The number of subranges in color scale 303 can be predetermined (e.g., as shown below). Figure 4 (The five sub-ranges shown).

[0068] It can be observed that Figure 4 The threshold values ​​(e.g., t4, t3, t2, t1) for the highest value 304 and color scale 303 are determined based on the geometric differences between the two digital 3D dental models being compared. Therefore, they are not predefined. The advantages this feature enables are related to... Figure 3The advantages of this disclosure are similar. Even clinically significant differences that are identified and typically exceed the range of color scales with preset boundaries can be captured and displayed on the difference map according to this disclosure. This allows users to identify and view serious conditions that require their attention, thereby enhancing the clinical value of the difference map of this disclosure. Furthermore, once the maximum value 304 is determined, other thresholds between the maximum value 304 and zero can be automatically determined. These thresholds therefore vary according to the digital 3D dental models being compared, eliminating any need for manual recalibration of the thresholds. This significantly saves time and effort, as users can focus more on analyzing the results of the difference map rather than spending time configuring the thresholds. Since the thresholds are always correlated with the specific digital 3D dental model pair being compared, the accuracy of data interpretation is improved. In addition, users can immediately see the relevant thresholds adapted to the currently compared digital 3D dental models, making the graphical user interface 300 more intuitive.

[0069] Figure 4 On color scale 303, the subrange 306 defined by values ​​0 and t1 represents a "no change" state. The positions on the superimposed digital 3D dental model 301 corresponding to the geometric differences within these subranges may not be superimposed with color, but can instead be displayed in their corresponding natural colors. Alternatively, colors such as green can be used.

[0070] Figure 3 The color swatch 303 enables geometric difference values ​​greater than t5 to also be displayed on the superimposed digital 3D dental model 301, but instead of using a new color, it uses the color corresponding to the uppermost subrange 306.

[0071] Figure 4 It also displays timeline 307, which has indicators 308 and 309 of the digital 3D dental models being compared, and... Figure 3 The indicators are identical. Indicator 308 corresponds to the first digital 3D dental model 100 (S1 or scan 1), while indicator 309 corresponds to the second digital 3D dental model 101 (S2 or scan 2). Indicators 308 and 309 can be arranged chronologically, with older scans placed to the left of timeline 307. This allows for a visual comparison of the digital 3D dental models and their corresponding timestamps. Users can hover over indicators 308 and 309 and obtain more information about the corresponding digital 3D dental model, including the scan date, for example, in a pop-up window.

[0072] Users can decide to include additional digital 3D dental models in the comparison tool according to this disclosure. Therefore, users can select additional digital 3D dental models for comparison with either the first digital 3D dental model 100 or the second digital 3D dental model 101. Users can make this selection by clicking indicator 308 or indicator 309. Based on user input (click), a library of available digital 3D dental models containing the additional model can be opened, allowing the user to select it. The additional digital 3D dental model can represent a dental condition at a different time, where this different time is later than the first time but earlier than the second time. This is just an example, as the different time can alternatively be earlier than the first time or later than the second time. Once the user selection is received, the overlaid digital 3D dental model 301 will be updated with the new data. Furthermore, as a new maximum value 304 is determined, and other thresholds between the maximum value 304 and zero are determined, the color scale 303 is updated. Timeline 307 can be updated accordingly to show which digital 3D dental models (scans) are being compared.

[0073] When a user selects a new pair of scans for comparison, color scale 303 can display an animated effect (typically lasting a few seconds) to indicate to the user that the threshold is being recalculated after the new scan is selected. This acts as a feedback mechanism to inform the user of the ongoing threshold adjustment process. This real-time or near real-time threshold recalculation can take into account the variability in the values ​​of scan data quality and / or geometric differences, which will be explained below.

[0074] and Figure 3 Similar to the implementation described herein, sub-ranges can be segmented. For example, if the initially obtained sub-range 306 is too wide, making it difficult to accurately label differences (which should be clinically distinguishable) on the superimposed digital 3D dental model 301, then each sub-range 306 can be segmented into two or more sub-ranges. Figure 4 In the example, dividing subrange 306 into two subranges will produce ten new subranges on color stop 303. This ensures that a single subrange 306 represented by a single color does not represent a value across a geometric difference that crosses a threshold used to divide the subranges. This threshold used to divide the subranges (called the second threshold) can be compared with... Figure 3 The same as described in [the text].

[0075] on the whole, Figure 3 and Figure 4 The difference graph shown provides users with data that adapts to a wide variety of situations in the context of the compared digital 3D dental models.

[0076] Figure 5A frequency histogram 500 of the geometric difference values ​​is shown in the difference plot; this histogram is used to identify outliers and noisy data. Identifying the maximum value of the geometric difference among the geometric difference values ​​can be challenging due to the presence of noise and / or outliers. To address this, a filter can be set to remove outdated data and find usable boundaries. This filter can be set and used to calculate the maximum value of the geometric difference in the geometric difference dataset. However, the filtered data does not necessarily have to be completely excluded from the visualization. If the geometric difference values ​​exceed the obtained filtered boundaries, these values ​​can still be visualized on the overlaid digital 3D dental model 301 using the closest color on color scale 303.

[0077] The horizontal axis 501 of histogram 500 represents the identified values ​​of geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101, in millimeters. The probabilities on the vertical axis 502 of histogram 500 represent the frequency of occurrence of the values ​​on the horizontal axis 501, thus showing how frequently each value occurs within the entire dataset of geometric difference values. Figure 5 The probabilities on the vertical axis 502 shown have been normalized.

[0078] exist Figure 5 In the histogram 500, values ​​between -0.1 and 0.1 (representing areas of no change / no color) can be discarded because these values ​​may be below the measurement accuracy of the intraoral scanner 701. The processor can receive this measurement accuracy when the method of this disclosure is initiated. Figure 5 Histogram 500 in the histogram shows a normal distribution and two outliers with low probabilities (-1.2 and 1.15). Therefore, these two outliers can be excluded from the calculations required to determine the color scale thresholds. Once filtering is performed, the maximum value of the geometric difference can be identified. In histogram 500, the maximum value is 0.6 mm and the minimum value is -0.65 mm. The maximum value of the geometric difference can be determined by taking the absolute values ​​of the maximum value 304 and the minimum value 305 and determining the larger of the two. Thus, the remaining color scale thresholds can also be automatically determined, and optionally, color scale 303 can be made symmetrical. In this case, the maximum value 304 of color scale 303 is 0.65 mm, and the minimum value 305 of color scale 303 is -0.65 mm. Dividing the obtained range by the predetermined number of sub-ranges 306 yields the other thresholds for color scale 303.

[0079] Next, the variance of histogram 500 can be calculated. For Figure 5Histogram 500 in the dataset has a variance of 0.001958. Filtering can then be performed using either the calculated variance or a portion of it. This portion of the calculated variance can be obtained as: k * calculated variance, where k > 0. For example, in histogram 500, values ​​with geometric differences less than -1.2 and greater than 1.15 are filtered out because their probabilities of association are below 0.001958. It should be noted that these values ​​may still be available on the difference plot and can be assigned the same colors as the maximum value 304 and / or the minimum value 305.

[0080] Figure 6 A graphical user interface (GUI) 300 is shown, displaying a view of the difference maps generated for comparing individual teeth against a first digital 3D dental model 100 and a second digital 3D dental model 101. Figure 6 A magnified view of teeth in an overlaid digital 3D dental model 301 is displayed, where color overlay 302 is applied to locations where differences have been identified. Color scales 303 include color scale thresholds specifically calculated for the first digital 3D dental model 100 and the second digital 3D dental model 101. Color scales 303 can be divided into a predetermined number of sub-ranges 306 (e.g., eight sub-ranges as shown) to define which colors are applied to which geometric differences. A timeline 307 with indicators 308 and 309 indicates which two digital 3D dental models are being compared.

[0081] Figure 7 A dental scanning system 700 is illustrated, which may include a computer 710 capable of performing any of the methods disclosed herein. The computer 710 may include wired or wireless interfaces to a server 715, a cloud server 720, and an intraoral scanner 701. The intraoral scanner 701 may be equipped with various modules, such as fluorescence modules and / or infrared modules, thereby enabling it to record scan data including geometric information, natural color information, infrared information, and / or fluorescence information related to the patient's dentition.

[0082] The dental scanning system 700 may include a data processing device configured to perform the methods described according to one or more embodiments of the present disclosure. The data processing device may be part of a computer 710, a server 715, or a cloud server 720.

[0083] The data processing apparatus may include means for performing the method according to this disclosure.

[0084] The dental scanning system 700 may include a data processing device configured to: - Receive a first digital 3D dental model 100 representing the dental condition at a given moment; - Receive a second digital 3D dental model 101 representing the dental condition at a second time, where the second time is later than the first time; - Generate a difference map based on the first digital 3D dental model 100 and the second digital 3D dental model 101, wherein the generated difference map includes: - Obtain the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101; - Identify the maximum value of the geometric difference from the values ​​of the geometric differences; - Generate a color scale 303 comprising multiple discrete colors associated with values ​​of geometric difference, wherein the colors among the multiple discrete colors are separated by a color scale threshold, and further wherein the color scale threshold is determined based on the maximum value of the geometric difference; - Assign multiple discrete colors to values ​​of geometric difference; and - Display a difference graph to visually highlight the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101.

[0085] The dental scanning system 700 may include a non-transitory computer-readable storage medium. This non-transitory computer-readable medium may carry instructions that, when executed by a computer, cause the computer to perform the methods described according to one or more embodiments of this disclosure.

[0086] This non-transitory computer-readable medium may carry instructions that, when executed by a computer, cause the computer to: - Receive a first digital 3D dental model 100 representing the dental condition at a given moment; - Receive a second digital 3D dental model 101 representing the dental condition at a second time, where the second time is later than the first time; - Generate a difference map based on the first digital 3D dental model 100 and the second digital 3D dental model 101, wherein the generated difference map includes: - Obtain the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101; - Identify the maximum value of the geometric difference from the values ​​of the geometric differences; - Generate a color scale 303 comprising multiple discrete colors associated with values ​​of geometric difference, wherein the colors among the multiple discrete colors are separated by a color scale threshold, and further wherein the color scale threshold is determined based on the maximum value of the geometric difference; - Assign multiple discrete colors to values ​​of geometric difference, and - Display a difference graph to visually highlight the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101.

[0087] Furthermore, the dental scanning system 700 may include a computer program product. This computer program product may include instructions that, when executed by a computer, cause the computer to perform the methods described according to one or more embodiments of this disclosure.

[0088] The computer program product may include instructions that, when executed by a computer, cause the computer to: - Receive a first digital 3D dental model 100 representing the dental condition at a given moment; - Receive a second digital 3D dental model 101 representing the dental condition at a second time, where the second time is later than the first time; - Generate a difference map based on the first digital 3D dental model 100 and the second digital 3D dental model 101, wherein the generated difference map includes: - Obtain the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101; - Identify the maximum value of the geometric difference from the values ​​of the geometric differences; - Generate a color scale 303 comprising multiple discrete colors associated with values ​​of geometric difference, wherein the colors among the multiple discrete colors are separated by a color scale threshold, and further wherein the color scale threshold is determined based on the maximum value of the geometric difference; - Assign multiple discrete colors to values ​​of geometric difference, and - Display a difference graph to visually highlight the values ​​of the geometric differences between the first digital 3D dental model 100 and the second digital 3D dental model 101.

[0089] Figure 8 An example of computer architecture for computer 710 is shown, which is capable of performing the methods according to this disclosure.

[0090] The various components of computer 710 can communicate via bus 810. Computer 710 may include data processing device 820 (also referred to as processor or processing device). Data processing device 820 may be any central processing unit (CPU), microprocessor, microcontroller, computing or programmable device or circuit configured to execute instructions to perform one or more methods of embodiments of the present invention.

[0091] Computer program product 840, containing instructions for performing the methods of any one or more embodiments of the present invention, may be stored on data processing device 820. Alternatively or additionally, computer program product 840 containing instructions for performing the methods of any one or more embodiments of the present invention may be stored on computer-readable medium 830, more particularly, on non-transitory computer-readable medium 830. Examples of computer-readable medium 830 include magnetic storage media (e.g., magnetic disks or magnetic tapes), optical storage media (e.g., optical discs, optical tapes), machine-readable barcodes, solid-state electronic storage devices (e.g., random access memory (RAM), read-only memory (ROM)), or any other physical device or medium configured to store computer program product 840.

[0092] The computer 710 may also include input / output devices 850, such as a keyboard, touchscreen, microphone, mouse, display unit, graphical user interface (GUI), speakers, etc. The display unit of the computer 710 can be used to display the graphical user interface 300.

[0093] Computer 710 can be connected to server 715, cloud 720, and / or intraoral scanner 701 via interface device 860. Interface device 860 can be a wired and / or wireless communication interface device, including Wi-Fi, Bluetooth, local area network, etc.

[0094] It should be understood that, in addition to the above embodiments, other embodiments may be made, and structural and functional modifications may be made without departing from the scope of the present invention.

Claims

1. A computer-implemented method for comparing digital 3D dental models, the method comprising: - Receive a first digital 3D dental model representing the dental condition at a real time; - Receive a second digital 3D dental model representing the dental condition at a second time, wherein the second time is later than the first time; - Generate a difference map based on the first digital 3D dental model and the second digital 3D dental model; wherein, generating the difference map includes: a) Obtain the value of the geometric difference between the first digital 3D dental model and the second digital 3D dental model; b) Identify the maximum value of the geometric differences from the values ​​of the geometric differences; c) Generate a color scale including a plurality of discrete colors associated with the value of the geometric difference, wherein the colors among the plurality of discrete colors are separated by a color scale threshold, further wherein the color scale threshold is determined based on the maximum value of the geometric difference; d) Assign the plurality of discrete colors to the values ​​of the geometric differences; - Display the difference map to visually highlight the values ​​of the geometric differences between the first digital 3D dental model and the second digital 3D dental model.

2. The method according to claim 1, wherein, Generating the difference map includes generating an overlay of digital 3D dental models by aligning the first digital 3D dental model and the second digital 3D dental model.

3. The method according to claim 2, wherein, Aligning the first digital 3D dental model and the second digital 3D dental model includes performing a global alignment to determine the absolute value of the variation between the first digital 3D dental model and the second digital 3D dental model.

4. The method according to claim 3, wherein, The absolute value of the change represents the change in tooth movement and / or soft tissue movement between the first digital 3D dental model and the second digital 3D dental model.

5. The method according to claim 3 or 4, wherein, The maximum value of the geometric difference is identified based on the global alignment.

6. The method according to claim 2, wherein, Aligning the first digital 3D dental model and the second digital 3D dental model includes performing local alignment, wherein the teeth of the first digital 3D dental model are individually aligned with the corresponding teeth of the second digital 3D dental model.

7. The method according to claim 6, wherein, The maximum geometric difference of the teeth in the superimposed digital 3D dental model is identified based on the local alignment.

8. The method according to any one of the preceding claims, wherein, The maximum values ​​for identifying the geometric differences include: - Generate a frequency histogram of the values ​​of the geometric differences; - Calculate the frequency variance based on the frequency histogram; - The filtered value of the geometric difference is obtained by filtering the value of the geometric difference using at least a portion of the calculated variance; - Identify the minimum and maximum values ​​from the filtered values ​​of geometric differences; - Identify the absolute values ​​of the minimum and maximum values.

9. The method according to claim 8, wherein, Filtering the values ​​of geometric differences using at least a portion of the calculated variance includes excluding those values ​​of geometric differences with a correlation probability value below a first threshold from the identification of the maximum value.

10. The method according to claim 9, wherein, The first threshold is at least a portion of the calculated variance.

11. The method according to any one of the preceding claims, wherein, The color scale includes multiple sub-ranges, wherein the discrete step length within each of the multiple sub-ranges corresponds to the measurement accuracy of an intraoral scanner used to scan dental conditions.

12. The method of claim 11, further comprising: If the surface area of ​​the difference map covered by a sub-range among the plurality of sub-ranges is greater than a second threshold, the number of sub-ranges is increased.

13. The method according to any one of the preceding claims further comprises: - Receive instructions for comparison using additional digital 3D dental models selected by the user; - Receive user selection of the first or second digital 3D dental model as an instruction for comparison with the other digital 3D dental model; - Generate a difference map based on the additional digital 3D dental model and the first or second digital 3D dental model; and - Display the difference map to visually highlight the values ​​of geometric differences between the additional digital 3D dental model and the first or second digital 3D dental model.

14. The method of claim 13, further comprising: The color scale threshold is updated based on the differences between the additional digital 3D dental model and the first or second digital 3D dental model.

15. A computer-readable medium comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 14.

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