Method and system for evaluating a tooth preparation surface

Abstract

A method and system of evaluating a tooth preparation surface is disclosed, including obtaining a digital oral situation and / or a portion thereof, including a preparation surface; evaluating an achievable thickness based on the preparation surface and the surrounding environment; and comparing the achievable thickness to a minimum thickness.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a system and method for evaluating a tooth preparation surface; in particular, a method and system for preparing a tooth preparation surface in a single appointment without the design of a dental prosthesis. BACKGROUND

[0002] Dental prosthetics is the branch of dentistry concerned with the design, fabrication and assembly of artificial replacements (prostheses) for teeth. In preparing a dental prosthesis, a dental practitioner can mill away an existing dentition to form a base for mounting the dental prosthesis. This is referred to as the preparation surface. A 3D model of the preparation surface and the surrounding environment can be obtained, and a suitable prosthesis can then be designed and fabricated and placed into the patient's mouth. Examples of dental prostheses include: crowns, inlays, onlays, bridges, etc.

[0003] The prosthesis can be designed digitally based on a digital 3D representation of the patient's oral situation. This digital 3D representation can be obtained, for example, by digitally scanning a physical impression, a cast thereof, or by directly using an intraoral scanner. The fabrication can also be digital, for example, where a computer generates a milling path, which can then be executed on a CNC mill. The dental prosthesis can be milled from a block or blank of ceramic or glass-ceramic material.

[0004] Sometimes, after the dental prosthesis has been fabricated, it can be found that it does not fit the preparation surface. In this case, one solution is to schedule another appointment with the patient and redo the preparation. Since this extra work is both costly and time consuming, it is often skipped. It can then be necessary to mill away the opposing teeth or the fabricated dental prosthesis, which is obviously a suboptimal solution. Furthermore, to prevent this, the dental practitioner can be inclined to remove more material from the prosthesis site. This in turn can result in unnecessary healthy tissue ablation and weakening of the prosthesis site. SUMMARY

[0005] The present disclosure comprises a computer-implemented method of evaluating a preparation surface, comprising:

[0006] A method for analyzing a dental preparation site, comprising: intraorally scanning at least part of a dentition, including a tooth preparation surface intended for mounting a dental prosthesis, creating a 3D digital model of the dentition, and analyzing the 3D digital model, wherein the analysis takes into account if the dental prosthesis is to be manufactured using a milling machine, and wherein the thickness that is reachable by the dental prosthesis is presented when the results of the analysis are presented prior to manufacturing the dental prosthesis.

[0007] The present disclosure can also comprise:

[0008] obtaining a digital oral situation comprising a preparation surface and / or a part thereof; evaluating at least one reachable thickness from the preparation surface and the surrounding environment; and

[0009] comparing the at least one achievable thickness to the at least one minimum thickness.

[0010] As mentioned above, a false tooth that does not match the prepared surface is both time and money consuming, and typically, the dental practitioner only has one session to prepare the prepared surface. Therefore, the dental practitioner often makes mistakes in preparing the prepared surface by removing too much tissue.

[0011] By considering not only the limitations of the available space for the false tooth, but also the limitations of the manufacturing method, this situation can be prevented. Furthermore, by using a digital false tooth and / or a second intraoral scan, any additional changes to the false tooth site can be made by the dentist in one visit. This avoids the cost of additional visits to the dentist, while reducing the likelihood of unnecessary material removal.

[0012] In a first aspect of the disclosure, a prepared surface is evaluated. First, a digital oral situation is obtained, which is a 3D digital model of the oral situation and / or a part thereof. This can be done directly by an intraoral scanner, or by scanning a physical model of the oral situation, for example. The 3D digital model can be based on voxels, a mesh, and / or a combination thereof, for example. The 3D digital model will typically have position values in three-dimensional space, allowing it to be placed relative to other 3D digital models. The digital oral situation comprises at least one prepared surface, a part of the oral situation that has been or is intended to be prepared for a false tooth. It can also comprise at least one prosthetic site, which comprises the prepared surface as well as the surrounding dentition and soft tissue.

[0013] The 3D digital model can be represented by different formats, such as by voxels, by a point cloud, by a mesh. A voxel representation uses a three-dimensional grid to represent a 3D object. Each voxel can be a cube in 3D space. If the object is present in the voxel, it is marked as present, and if not, it is marked as not present. A point cloud is a collection of points in 3D space, each point having x, y, z coordinates. A mesh is a collection of vertices, edges, and faces. Vertices are individual points that represent a surface, edges are lines connecting vertices, and faces are contiguous areas enclosed by vertices and edges. These can all be used to represent a digital dental model.

[0014] In some embodiments, the prepared surface is detected. In one embodiment, the dental practitioner can manually annotate the prepared surface, for example, by inspecting the 3D digital model of the oral situation using 3D modeling software and outlining the prepared surface with an associated marker, as is possible in the dental desktop software by 3Shape, for example. In an embodiment, the prepared surface can be detected - for example, by segmenting the oral situation to identify the teeth, and then identifying which teeth are the correct shape for the prepared surface, for example, by heuristics such as size and proportion, or more complex algorithms such as neural networks.

[0015] Next, at least one achievable thickness is calculated between the surrounding environment, i.e. the part of the digital oral situation that is not part of the preparation surface, and the preparation surface. The achievable thickness is the shortest distance between the preparation surface and the surrounding environment, and can take further restrictions into account, as described below. The achievable thickness can be calculated by finding a point on the prosthesis surface, finding a point on the surrounding oral situation, and calculating the distance between the two. This can be the closest point on the non-preparation surface part of the oral situation. The achievable thickness can be adjusted by a certain distance if the situation calls for it.

[0016] In some embodiments of the disclosure, the evaluation of the achievable thickness can take into account the space requirement resulting from the drilling compensation of the prosthesis inner surface and / or the desired distance from the prosthesis to the opposing and / or adjacent dentition. The non-zero desired distance between the prosthesis and the opposing dentition can be induced by the need to leave space for the enamel, i.e. the coating on the prosthesis. Another inducement for the non-zero distance to the opposing dentition can be to allow for natural tooth growth and movement. This can be influenced by, for example, the cement gap, the milling limit (e.g. drill radius), the external coating on the prosthesis. These will be discussed in more detail below.

[0017] One thing to take into account when looking at the achievable thickness is the marginal line where the preparation surface meets the non-preparation surface. Points within the distance corresponding to the minimum thickness along the marginal line should not be taken into account when calculating the achievable thickness.

[0018] The minimum thickness is the minimum distance between the preparation surface and the non-preparation surface required due to technical reasons, e.g. material strength. The minimum thickness can also be influenced by which part of the prosthesis is being evaluated and what the use of the prosthesis is. For example, the occlusal surface of the prosthesis typically requires a larger minimum thickness than the walls along the lingual or buccal side to take into account the forces resulting from occlusion. A crown typically requires a larger minimum thickness than a veneer.

[0019] The at least one achievable thickness is compared to the at least one minimum thickness. The minimum thickness can conflict with the achievable thickness, as the minimum thickness can require more space than the achievable thickness allows. In this case, the digital prosthesis, the preparation surface and / or the surrounding dentition can need to be adjusted, as described below.

[0020] The evaluation according to the disclosure can be performed on a computer. The computer can also be able to provide a visualization of the evaluation. The computer can also perform calculations related to establishing a digital 3D representation based on data from an intraoral scanner. The same display device can present data relevant during the scan and from the subsequent evaluation. The scanner can be connected to the computer by a cable, or wireless data transfer between the scanner and the computer can be provided.

[0021] One embodiment also includes generating an inner surface of the digital dental prosthesis based on the preparation surface.

[0022] The digital dental prosthesis is a 3D digital model of the dental prosthesis. An inner surface of the digital dental prosthesis can then be generated based on the preparation surface. For example, an initial inner surface can be generated by copying the shape of the prosthesis site. This inner surface can then be adjusted, for example, to accommodate manufacturing limitations, material limitations, cement gaps, etc. These adjustments are described in more detail below.

[0023] One embodiment also includes generating an outer surface of the digital dental prosthesis.

[0024] An outer surface of the digital dental prosthesis can be generated. For example, this can be a 3D mesh selected from a library or generated by a computer-implemented method, such as a neural network trained on tooth outer surfaces. The outer surface can be further adjusted, as described below.

[0025] One embodiment also includes:

[0026] defining a negative space around the preparation surface based on the digital oral situation; and

[0027] generating an outer surface of the digital dental prosthesis based on the negative space.

[0028] A negative space around the preparation site is defined, i.e. a blank space in which the dental prosthesis can fit. This can be done, for example, by checking the oral situation against adjacent teeth and / or gums, opposing teeth and / or gums, and other items in the oral situation that can limit the dental prosthesis. The outer bounds of the negative space can be defined as the area containing the oral situation relevant to manufacturing the dental prosthesis, for example, a portion of the oral situation within a 3 cm radius of the center of the prosthesis site.

[0029] Based on the negative space, an outer surface of the digital dental prosthesis can be generated. If the outer surface meets the constraints of the negative space, for example, does not overlap with adjacent teeth or opposing teeth, it can be used as the outer surface of the digital dental model.

[0030] The outer surface can also be changed to meet the constraints of the negative space. For example, it can be made taller or shorter, wider or narrower, or changed by some other parameter to make it more or less convex on a particular side. This can be done manually by a dental practitioner or as part of a computer-implemented method.

[0031] One embodiment also includes generating the digital dental prosthesis based on the inner surface and the outer surface.

[0032] A digital denture can be generated based on the inner surface and the outer surface. In one embodiment, both the inner surface and the outer surface are 3D meshes, and are connected at their nearest intersection. Both the outer surface and the inner surface are positioned in the digital oral situation; the inner surface can be positioned relative to the preparation surface, and the outer surface can be positioned based on the inner surface, achievable thickness, and / or negative space. The inner surface and the outer surface can then be connected at where they intersect, e.g., for each point on the mesh model of the initial outer surface, find the nearest point on the initial inner surface. If these points are lined up, anything outside of that line can be discarded, and on both the initial inner surface and the initial outer surface, the model can be stitched together at these points to generate the digital denture.

[0033] Some limitations are imposed on the digital denture around manufacturability. It can be useful to consider minimum thickness and achievable thickness when generating the digital denture.

[0034] The digital denture can be further changed, e.g., decimated and / or otherwise smoothed, to make it easier to machine or manufacture. For example, for some forms of processing, processing can be faster where there are fewer points on the mesh. Thus, removing points on the mesh that are very close to each other by decimation can allow for more efficient processing. Smoothing can also be used. For example, if the line where the inner surface and the outer surface are stitched together is jagged, smoothing the line by removing outlier points can allow for easier manufacturing and better fit. The digital denture can be adjusted by preprogrammed changes, or manually changed by a dental practitioner through, e.g., a sculpting application.

[0035] One embodiment also includes deriving the digital oral situation from an intraoral scanning device.

[0036] The digital oral situation can be obtained from an intraoral scanning device. Examples of intraoral scanners that can be used to obtain the digital 3D representation are the 3Shape Trios, Dentsply Sirona PrimeScan, and others. Using an intraoral scanning device is that subsequent scans allow for subsequent scans to be taken, enabling further changes to the digital denture and / or the oral situation, as described below.

[0037] One embodiment also includes adjusting the digital denture and / or the preparation surface by:

[0038] evaluating the digital denture and / or the preparation surface for at least one minimum thickness and at least one achievable thickness;

[0039] comparing the at least one minimum thickness and the at least one achievable thickness; and

[0040] adjusting the digital denture and / or the preparation surface where the at least one minimum thickness conflicts with the at least one achievable thickness.

[0041] One embodiment also includes iteratively adjusting the digital prosthetic and / or the preparation surface, and evaluating them against at least one minimum thickness and at least one achievable thickness. This can help reduce the amount of healthy tissue removed. Typically, when creating a preparation surface, the dental practitioner has only one session to prepare the preparation site, and then design the prosthetic. Thus, the dental practitioner often prefers to remove too much material, as making a return visit and / or manufacturing an ill-fitting prosthetic is expensive. Furthermore, the dental practitioner typically relies on their own visual judgment to create the preparation site. Removing more tissue than needed helps ensure that the prosthetic can be installed, but can remove healthy tissue and / or weaken the prosthetic site. Furthermore, in cases where there can not be enough tissue at the prosthetic site to support a crown, expensive procedures such as a core build-up can be required.

[0042] Using the methods in this disclosure, the dentist can reduce unnecessary dental tissue removal by removing a conservative amount of tissue, and then using the digital oral situation to make a more accurate assessment of the possible prosthetic - rather than just guessing. Furthermore, the digital oral situation allows the achievable thickness to be evaluated by software, better informing the dental practitioner's choices. For example, the dentist can determine that certain materials are not suitable for use.

[0043] The achievable thickness and minimum thickness of the digital prosthetic can be evaluated, and adjusted or rejected accordingly. In cases where the digital prosthetic is not feasible or otherwise undesirable, the dental practitioner can adjust the oral situation, including the preparation surface. For example, in cases where the preparation surface does not achieve a minimum thickness between it and its adjacent teeth, the dental practitioner can choose to further reduce the preparation surface or grind the adjacent teeth, depending on the situation. This adjustment can be further aided by displaying areas where the oral situation conflicts with other aspects of a good digital dental preparation, as described below.

[0044] Furthermore, given the speed of intraoral scanners, this can all be done in one patient session, rather than requiring the patient to return for a follow-up visit. This reduces costs and time for both the dentist and the patient.

[0045] One embodiment also includes displaying the digital preparation surface, the digital oral situation, and / or the digital prosthetic.

[0046] One embodiment also includes:

[0047] evaluating the preparation surface of the problem area based on at least one achievable thickness;

[0048] displaying the digital preparation surface, the digital oral situation, and / or the digital prosthetic; and

[0049] highlighting the problem area on the digital preparation surface, the digital oral situation, and / or the digital prosthetic.

[0050] For certain points on the preparation surface, the achievable thickness can not meet the minimum thickness requirement; these are problem areas. The preparation surface can be represented by a digital 3D model, a digital preparation surface. By evaluating the digital preparation surface of the problem areas, a computer-implemented method can help the dental technician to adjust the digital preparation surface.

[0051] In this case, the digital preparation surface, the digital oral situation and / or the digital dental prosthesis can be displayed on, for example, a computer screen, highlighting the problem areas. Highlighting here means that a certain area is to be paid special attention to. This can be done, for example, by displaying the problem areas in a different color, with a contour around them, in a different texture and / or with a different transparency. This can allow the dental practitioner to further correct the preparation surface, the surrounding environment and / or the digital dental prosthesis, as described below.

[0052] In an embodiment, the preparation surface can remain unchanged, but the problem areas on the surrounding environment can be highlighted. The problem areas can be displayed in both the preparation surface and the surrounding environment, thereby allowing the dental practitioner to decide which area to adjust.

[0053] An embodiment further comprises:

[0054] aligning the digital dental prosthesis with the digital oral situation and / or the digital preparation surface; and

[0055] displaying the digital dental prosthesis and the digital oral situation.

[0056] An embodiment further comprises aligning the digital dental prosthesis with the digital oral situation and / or the digital preparation surface and displaying, thereby allowing the dental practitioner to make a more informed choice regarding the production of the dental prosthesis. Here, both the digital dental prosthesis and the 3D digital model of the oral situation have Euclidean values, representing their position in 3D space. In case the initial inner surface of the digital dental prosthesis is based on the prosthesis site, the digital dental prosthesis can align the inner surface with the initial inner surface, thereby allowing adjustments to be made. Since the outer surface is generated with respect to the negative space in the digital oral situation, it can be aligned based on this.

[0057] Once the digital dental prosthesis is aligned, it can be displayed on, for example, a computer screen. This allows the dental practitioner to visually assess the potential dental prosthesis and make adjustments accordingly. This can be further aided by highlighting the problem areas, as described below. As mentioned above, displaying can be particularly useful as part of an iterative process.

[0058] An embodiment further comprises:

[0059] evaluating the aligned digital dental prosthesis and the problem areas of the digital oral situation;

[0060] displaying the aligned digital denture and digital oral situation; and

[0061] highlighting problem areas on the display.

[0062] One embodiment further includes evaluating the aligned digital denture and digital oral situation for problem areas and highlighting these problem areas on the display. Potential problem areas include: overlaps, e.g., where objects in the digital denture and oral situation occupy the same space, areas where there is a risk of overlap, areas that cannot be manufactured due to milling limitations, and / or areas where the digital denture fails to achieve a minimum thickness.

[0063] These problems can be displayed on a digital 3D representation, a color map, or other rendering. They can be displayed on a screen or in a virtual reality environment. The presentation can highlight problem areas on the digital oral situation and / or digital denture that are problematic in the sense of failing to achieve a minimum material thickness and / or any additional required space. The visualization can help to distinguish the areas. The visualization can use, for example, different colors to display the magnitude of the problem, e.g., the degree of violation of the minimum thickness.

[0064] In some embodiments, the problem areas can be displayed as portions of the inner surface of the proposed design of the prosthesis, where the design can be based on the drill direction, the cement space specifications, and the drill radius. In some embodiments, the problem areas can be visualized on the preparation site, i.e., as portions of the digital 3D representation. For example, the areas can be displayed as the intersection or projection of the drill geometry along the simulated milling path, or as the distance between the drill surface and the preparation surface at that location along the path. Such a distance can be larger than the cement gap when drill compensation occurs.

[0065] In some embodiments, the problem areas can be problem volumes visualized by volume rendering. The problem volumes can be the three-dimensional space in or on the preparation site that will be occupied by the drill during milling, where the drill touches the inner surface of the crown solely due to the need for drill compensation. In particular, the problem volumes that should be drilled away for the preparation so that there are no more problems can be highlighted. The problem areas can also be rendered as the surface of the problem volumes. The volume rendering can include slicing or employ different degrees of transparency.

[0066] In some embodiments, the evaluation can end by indicating that there are no problem areas.

[0067] One embodiment further includes generating the digital denture in a single patient visit.

[0068] Generating a digital denture in one patient visit by the above method can save time and money for both the dental practitioner and the patient. With only a few iterations needed to generate the digital denture, an initial model of the digital denture can be generated on the same day.

[0069] The method according to any one or more of the preceding items further comprises calculating an influence of at least one drill characteristic and adjusting the achievable thickness and / or inner surface based on the influence of the at least one drill characteristic.

[0070] One embodiment also includes considering the influence of at least one drill characteristic in the evaluation of the preparation surface and / or in the generation of the digital denture. For example, the drill characteristic can be drill radius, drill material, drill shape, drill cost, drill durability, drill direction, etc. One example of the effect of drill characteristics is drill compensation, i.e. measures taken to compensate for the radius of the drill. Drill compensation means that more of the inside of the prosthesis needs to be drilled during the manufacturing process than would be needed if only the surface of the prosthesis site offset by the space of the cement would be matched. Drill compensation can be needed when the corner radius of the prosthesis site is smaller than the drill radius of the milling machine used for the manufacturing in at least some areas.

[0071] The size of the drill bit can impose a limit on the geometry that can be milled. This can be particularly important on the inner surface of the prosthesis where the prosthesis is directly adjacent to the prosthesis site due to the need for a good fit. In typical digital design software, such as 3Shape Dental System, the drill compensated inner surface of the prosthesis can be calculated from the prosthesis site.

[0072] For example, the drill radius can indicate the radius of a globoid drill tip, or the edge radius of a drill tip that is rounded near the edge but flat at the center. The present disclosure is similarly applicable to other shapes of drills. While a milling machine typically has a set of drills, mathematically, the limit regarding the implementation of some small corner radius on the inner surface of the prosthesis is the smallest radius of all drills in the set.

[0073] The effect of drill compensation can be that prosthesis material that might otherwise have helped to meet the minimum thickness requirement is removed. Since the problem of a preparation edge radius being smaller than the milling machine drill radius is common, the need for drill compensation can also be common. Therefore, it is often not sufficient to only measure the distance from the prosthesis site to the opposite dentition when determining the ability of a potential prosthesis to meet the minimum thickness requirement. For more information on calculating the drill compensated inner surface of a denture, see, for example, EP 3,197,389 filed September 24, 2015; US20170273763A1 filed September 24, 2015.

[0074] The method according to any one or more of the preceding items further comprises calculating the effect of a plurality of drill radii on the at least one achievable thickness and / or inner surface; and selecting at least one drill radius based on the calculation of the effect of a plurality of drill radii.

[0075] In some embodiments, different radii of drills can be used to manufacture the dental prosthesis, and this can affect the achievable thickness, which in turn affects the digital dental prosthesis. For example, a smaller drill radius can be able to manufacture a dental prosthesis that meets the minimum thickness, while a larger one can not. On the other hand, the dental prosthesis can not need to use a more expensive smaller drill bit every time. By calculating the effect of a plurality of drill radii, the dental practitioner can be able to select a more accurate or cost-effective solution.

[0076] An embodiment further comprises selecting a drill by, for each of a plurality of drills, estimating a cost of drill wear to manufacture the dental prosthesis based on the digital dental prosthesis; and selecting a drill according to the estimated cost of drill wear.

[0077] In some embodiments, the drill can be selected based on a cost evaluation. A drill with a small radius such as 0.3 mm can be used for the manufacturing; however, such a drill is fragile and therefore expensive to use every time. Moreover, milling with a small radius drill takes more time. Therefore, the evaluation of the digital dental prosthesis can take into account which is cheaper and / or faster to manufacture, and adjustments that can be made to reduce the cost and / or time.

[0078] The evaluation according to the present disclosure can also take into account various drill radii, including combinations thereof. Such an evaluation can also include an evaluation of the cost. For example, a larger drill can be used for rough cutting, while a smaller drill is used to render finer details, and the cost is calculated by the expected number of hours of use of each drill multiplied by the expected cost per hour. The result of this can be presented to the dental practitioner. By avoiding the use of a drill with a small radius, a small change to the prosthesis site can allow for significant savings in manufacturing cost.

[0079] An embodiment further comprises selecting a drilling direction based on the at least one achievable thickness, the digital dental prosthesis, and / or the digital oral situation.

[0080] In embodiments of the present disclosure, a drilling direction can be identified. The drilling direction is the direction in which the drill approaches the inner surface of the prosthesis during the manufacturing process. For example, the drilling direction can be opposite to the insertion direction, as described below.

[0081] Different drilling directions can be considered for different parts of the inner surface, and as a generalization thereof, a continuous drilling direction can be considered. Situations with multiple drilling directions can arise if a 5-axis milling machine is to be used for manufacturing the dental crown, or if a non-linear insertion path is considered. In an embodiment of the present disclosure, a single drilling direction is used when calculating the drilling-compensated inner surface. If a 3-axis milling machine is to be used for manufacturing the dental crown, the drilling direction can be opposite the insertion direction. The insertion direction can specify the direction along which the dental crown will slide onto the preparation when it is installed. The insertion direction can be chosen so that undercuts on the preparation are reduced and / or minimized. Detailed examples of choosing the drilling direction are described below.

[0082] An embodiment further comprises detecting at least one undercut region in the preparation surface, and adjusting the achievable thickness, the inner surface, and / or the preparation surface in dependence of the undercut region.

[0083] An embodiment further comprises detecting the location and severity of undercut regions on the preparation surface, and making adjustments to mitigate the consequences of the undercut regions. To reduce the harm of the undercut regions, the achievable thickness, the inner surface, the preparation surface, and / or combinations thereof can be adjusted.

[0084] An undercut is a part of the preparation surface that is not visible when the preparation surface is seen as a front projection along the insertion direction. Thus, any choice of insertion direction defines an undercut region on the preparation surface. The choice of insertion direction is further discussed below. One way to assess whether a point on the preparation surface is undercut is to use ray tracing: a ray is emitted from the point on the preparation surface in a direction opposite the insertion direction. If the ray intersects the preparation surface at any other point than the point being assessed, the point is undercut.

[0085] Once undercut regions have been detected, there can be multiple embodiments for how to handle them. First is to adjust the dental crown and / or the digital dental crown so that it can be inserted. This can be done, for example, by adjusting the inner surface of the dental crown, for example by simply milling away the parts that would obstruct the insertion by removing the undercut. This is a quick and efficient way to do it, and can be useful in cases where the changes are small and the gap can be filled with cement.

[0086] However, in cases where the gap is large, the dental crown can be at risk of growing bacteria and damaging the underlying tooth. This is especially true at the margin line, where a good seal is important. A large undercut can also mean that the dental crown does not meet the minimum thickness requirement. One way to handle this second problem is to adjust the outer surface to compensate, possibly by moving it the necessary amount in a direction perpendicular to the surface.

[0087] In an embodiment, the preparation surface can be adjusted. If there are overhangs large enough to cause problems, the preparation surface can be ground down so that the undercut areas can be acceptably repaired with cement or by other means. The dental practitioner can use an intraoral scanner on the preparation surface to detect any such overhangs, and then scan again to determine if the overhangs are sufficiently ground down.

[0088] In an embodiment, a combination of adjusting the digital prosthesis and adjusting the preparation surface can be used. This can be useful where, for example, reducing an overhang on the preparation surface by an amount will allow the digital prosthesis to be adjusted so that the cement gap is acceptable.

[0089] The method according to any of the preceding claims, further comprising determining at least one undercut region based on the selected insertion direction.

[0090] The method according to any of the preceding claims, further comprising: evaluating a plurality of insertion directions for the undercut; and selecting the insertion direction based on the determined undercut from the plurality of insertion directions.

[0091] Selecting an insertion direction for the prosthesis so that there is no undercut near the marginal line can allow for a tighter fit; it can be necessary to fit tightly in this area to ensure that the interior of the prosthesis is sealed. One simple method is to select the insertion direction so that it maximizes the area-normalized sum of the dot products between the negative of the insertion direction and the face normals of each face: select the insertion direction so that it maximizes the area-normalized sum of these dot products. A possible implementation of this method is obtained by evaluating the area-normalized sum for each of a plurality of randomly selected candidate insertion directions and selecting the one that yields the maximum. Another embodiment is to select the insertion direction so that the undercut regions along the band along the marginal line are reduced, and if there is a direction so that there is no undercut in this band, select it so that the total undercut region is reduced under the constraint that there is no undercut in said band along the marginal line.

[0092] The method according to any one or more of the preceding items, further comprising: obtaining a coating distance for an external coating; and adjusting the inner surface, the outer surface, and / or the preparation surface based on the coating distance.

[0093] An embodiment further comprises adjusting the inner surface, the outer surface, and / or the preparation surface to account for an intended coating. Coating materials can be used to manufacture a prosthesis to improve the functional appearance, such as a porcelain coating on a cubic zirconia crown. However, coating a prosthesis with such a material increases the thickness of the prosthesis. One way to compensate for this is to adjust the inner surface, the outer surface, and / or the preparation surface of the digital prosthesis to account for the coating.

[0094] In one embodiment, the expected thickness of the coating can be obtained and used to calculate the coating distance that the surface should be moved. For a digital denture, the points on the outer surface and / or inner surface can then be moved in the opposite direction of the surface normal by the appropriate distance. In essence, the digital denture is caused to move its surfaces inwards and its overall volume is reduced to accommodate the expected coating. This allows the denture to be manufactured to still fit the oral situation, despite the addition of the coating.

[0095] The adjusted digital denture can also be re-evaluated for minimum and achievable thicknesses.

[0096] Furthermore, the preparation surface can also be adjusted to accommodate the expected coating, either alone or in combination with the adjustment of the inner and / or outer surfaces, e.g. to be ground down further.

[0097] One embodiment further comprises adjusting the digital denture by:

[0098] generating at least one parameter for the outer surface; and

[0099] adjusting the outer surface based on the at least one parameter.

[0100] In one embodiment, the outer surface can be further adjusted, e.g. for aesthetic and / or functional reasons. It can be useful to adjust it by parameters - a limited number of qualities of the outer surface shape. Parameters include features such as height and width, e.g. to make the crown higher to ensure that the crown meets the opposing tooth to achieve correct occlusion. It can also include features such as buccal ridge or cusp height. One embodiment uses the principal components from a principal component analysis of many outer surfaces as parameters, allowing the outer surface to be manipulated by these parameters. The digital denture can be re-evaluated for at least one minimum thickness and at least one achievable thickness as described above.

[0101] One embodiment further comprises allowing a user to sculpt the outer surface with a sculpting application.

[0102] Sometimes, a dental practitioner can wish to change the outer surface of the digital denture using their own judgement. In this case, the outer surface can be processed into a format usable by a sculpting application, e.g. a mesh or point cloud, if it is not already in such a format. The sculpting application can then allow a user to sculpt the surface. For example, the sculpting application includes programs such as Blender, Zbrush, or tools from sculpting tools in Dental Desktop from 3Shape.

[0103] One embodiment further comprises adjusting the inner surface by: obtaining a cement gap distance for a cement gap; adjusting the achievable thickness, the digital denture and / or the preparation surface based on the cement gap distance.

[0104] The assessment of the achievable thickness can take into account a cement gap between the preparation and the inner surface of the prosthesis. Dental cement is used to bond the prosthesis to the prepared surface. For example, a typical value for the gap to hold the cement can be in the range of 30 pm to 90 pm.

[0105] In an embodiment, for example, the achievable thickness can be reduced by a cement gap distance for a cement gap, and the assessment of the prepared surface is adjusted accordingly.

[0106] In an embodiment, the inner surface and / or the outer surface of the digital prosthesis can be offset by a cement gap distance in a direction perpendicular to the inner surface and away from the site of the prosthesis.

[0107] In an embodiment, the prepared surface itself can be adjusted to accommodate a cement gap distance for a cement gap.

[0108] The above embodiments can be used individually or in combination.

[0109] An embodiment further comprises selecting the at least one prosthesis material by: assessing the at least one minimum thickness based on each of a plurality of prosthesis materials; and selecting at least one of the plurality of prosthesis materials based on the assessment of the at least one minimum thickness.

[0110] An embodiment selects the prosthesis material by assessing a plurality of prosthesis materials to see which prosthesis material is more suitable for the situation. Potential prosthesis materials include: metal alloys, ceramic-based materials (such as lithium disilicate and zirconia), resins, porcelain, and / or combinations of the above materials.

[0111] As mentioned above, the minimum thickness can vary depending on the location where the material is to be used. Different materials can be suitable depending on the individual oral situation of the patient. For example, a lithium disilicate posterior crown also requires a minimum thickness of 1.5 mm at the cusps at the buccal and lingual regions as well as at the occlusal surface; however, zirconia requires 1.5 mm at the cusps at the occlusal surface and only 1.2 mm at the buccal and lingual regions. Thus, for an oral situation where the adjacent teeth are closer to the site of the prosthesis, it can make more sense to use zirconia. On the other hand, the patient can prefer the aesthetics of lithium disilicate. In assessing the digital prosthesis to meet the minimum thickness of different materials, it allows for the selection of a viable material, or it allows the dental practitioner to further modify the digital prosthesis to meet the minimum thickness requirement of the desired material.

[0112] An embodiment further comprises selecting the at least one prosthesis material by: estimating a cost of each of a plurality of prosthesis materials; and selecting at least one of the plurality of prosthesis materials based on the estimated cost.

[0113] The price of dental prosthetic material can vary greatly. Therefore, it can be useful to compare costs to allow a dental practitioner and / or a patient to decide which crown material to use. For example, the software can automatically select the least expensive viable material.

[0114] The method according to any one or more of the preceding statements, wherein the digital oral situation further comprises at least one opposing tooth, the method further comprising:

[0115] Identifying at least one opposing tooth surface in the digital oral situation;

[0116] Identifying a desired interocclusal distance; and

[0117] Adjusting the achievable thickness and / or outer surface based on the desired interocclusal distance and the at least one opposing tooth surface.

[0118] The interocclusal distance is the vertical distance between the occlusal surfaces of the upper and lower teeth when the mandible is in a resting position; in this context, the teeth can include teeth with prostheses. If the prosthesis is designed to leave a little space for the opposing tooth, the natural reaction of the body is to move the prosthesis towards the opposing tooth until resistance is encountered in occlusion. On the other hand, if the prosthesis is designed so that it is already connected with the opposing tooth when occluding, the body cannot naturally adjust the interocclusal distance. These geometries can cause excessive pressure on the prosthesis material. For this reason, it is better to allow a smaller interocclusal distance in the prosthesis design.

[0119] Here, at least one tooth surface opposite the preparation surface is found in the digital oral situation, for example by manual annotation or by a machine learning algorithm as described above.

[0120] The desired interocclusal distance is identified. This can be based on, for example, patient characteristics, technical requirements, and / or clinical requirements. For example, older patients can have less expected tooth growth than younger patients. On average, dentate patients have more occlusal space than partially edentulous patients. (See Montero & Dib, 2019, Abstract). For example, the interocclusal space can be as small as zero and as large as 10 mm where the opposing teeth are in contact. The average interocclusal space for dentate patients can be between 2 mm and 4 mm, but can vary further depending on where it is on the teeth.

[0121] In one embodiment, the achievable thickness can be adjusted based on the desired interocclusal distance. For a given value on the preparation surface, the achievable thickness can be reduced by a value based on the desired interocclusal distance required at that point. For example, this can be the desired interocclusal distance itself, the desired interocclusal distance adjusted for the angle of the achievable thickness, and / or the desired interocclusal distance adjusted for an expected bias.

[0122] In an embodiment, the digital denture can be adjusted by a desired interocclusal distance. For example, for a point on the outer surface, a closest point on the opposite surface can be found, and if the distance between the two does not comply with the desired interocclusal distance, the point on the outer surface can be moved to accommodate the desired interocclusal distance. As mentioned above, the desired interocclusal distance can be adjusted based on the situation.

[0123] The method according to any one or more of the preceding statements, wherein the oral situation further comprises at least one adjacent tooth, the method further comprising:

[0124] identifying at least one adjacent tooth surface;

[0125] identifying a desired interproximal distance; and

[0126] adjusting the achievable thickness and / or the outer surface based on the desired interproximal distance and the at least one adjacent tooth surface.

[0127] The interproximal distance is the distance between adjacent teeth. When a tooth is ground away to create a preparation surface, it removes the interproximal support it provided to its adjacent teeth. This can cause a small rotational movement of the adjacent teeth towards the center of the prosthetic site. To correct for this rotational movement, the denture can be designed to slightly protrude into the adjacent tooth surface at its closest point to the adjacent tooth. This ensures a tight interproximal fit when the prosthesis is installed. If such a protrusion into the adjacent tooth is needed, it can be achieved by adjusting the achievable thickness and / or the outer surface based on a desired interproximal distance.

[0128] Here, at least one tooth surface adjacent to the preparation surface is found in the digital oral situation, for example by manual annotation or by a machine learning algorithm as described above.

[0129] A desired interproximal distance is identified. This can be based on, for example, patient characteristics, technical requirements, and / or clinical requirements. The interproximal distance can vary depending on where it is on the tooth and the purpose of the treatment, as described below.

[0130] In an embodiment, the achievable thickness can be adjusted based on the desired interproximal distance. For a given value on the preparation surface, the achievable thickness can be reduced by a value that is based on the desired interproximal distance that is needed at that point. For example, it can be the desired interproximal distance itself, the desired interproximal distance adjusted for an expected rotation, and / or the desired interproximal distance adjusted for an expected bias.

[0131] In an embodiment, the digital dental prosthesis can be adjusted by a desired interproximal distance. For example, for a point on the outer surface, the closest point on the adjacent surface can be found, and if the distance between the two does not comply with the desired interproximal distance, the point on the outer surface can be moved to accommodate the desired interproximal distance. The desired interproximal distance can be adjusted based on the situation, as described above.

[0132] In an embodiment, the digital dental prosthesis can be designed to slightly overhang the adjacent teeth. Here, the outer surface can be adjusted by a small amount, e.g. 0.05-0.1 mm, at the points closest to the adjacent teeth in a direction perpendicular to the outer surface and outwards from it. This allows the final dental prosthesis to slightly overhang its neighbours. This can be achieved by geometric calculations, e.g. moving certain points outwards and smoothing - by manual correction of the digital dental prosthesis in a sculpting application, and / or by machine learning algorithms trained to make such movements, e.g. running a principal component analysis on the tooth outer surface and adjusting the tooth by changing the principal components.

[0133] The method according to any of the preceding items, wherein the prosthesis comprises: a crown, a bridge, a veneer, an inlay and / or an onlay.

[0134] Various dental prostheses can benefit from the described methods, including but not limited to: crowns, inlays, onlays, bridges and / or veneers. Using the described computer-implemented methods to assess digital oral situations and digital dental prostheses can be helpful in creating these.

[0135] A computer program product in a non-transitory medium configured to, at runtime, perform the method of one or more of the preceding items.

[0136] The present disclosure also includes computer program products that perform the methods described in the present disclosure, e.g. software or hardware with embedded programming.

[0137] A method of preparing a preparation surface with digital assistance during a preparation appointment, comprising:

[0138] preparing a preparation surface in an oral situation;

[0139] producing a first digital oral situation by intraorally scanning the oral situation;

[0140] assessing the first digital oral situation; and

[0141] returning a result.

[0142] In a second aspect of the disclosure, the preparation surface can be made with digital assistance. As discussed above, one reason for less than optimal preparation surfaces is the inconvenience of scheduling a second appointment to fix the preparation surface. By using an intraoral scanner and evaluating the preparation surface as described above, the preparation surface can be evaluated and corrected, if necessary, in a single appointment with the patient.

[0143] The dental technician can prepare the preparation surface in the patient's mouth, for example, by removing dental tissue to make room for the prosthetic, etching, milling, and / or other tooth preparation methods. The present disclosure allows the dental technician to be conservative in the tissue removal because the preparation site will be evaluated before the prosthetic is designed and / or manufactured.

[0144] Traditional crown procedures rely on taking dental impressions and sending them to a lab where a crown is generated from the dental impressions. In such a process, it is not practical to iterate between preparation and evaluation. Because of the use of an intraoral scanner and digital models in the present disclosure, unnecessary tissue removal can be reduced compared to traditional crown procedures.

[0145] The patient's mouth is then scanned intraorally as described above and a first digital mouth condition is generated. Because of the speed of the intraoral scanner (e.g., a typical 3Shape Trios scan can be as fast as 22 seconds, and typically takes less than 5 minutes), and the low incremental cost of another scan, multiple scans can be performed in a single appointment.

[0146] The first digital mouth condition can then be evaluated - for example, for various properties that are applicable to the prosthetic, such as the achievable thickness of the prosthetic, the minimum height of the preparation surface itself, potential undercuts, etc. As described above, this allows for a quick evaluation of potential problem areas, or for a quick evaluation of the preparation surface.

[0147] A result is then returned. For example, the result can be a confirmation that the preparation surface is likely acceptable, or a rejection because the preparation surface is not suitable. For example, the result can be returned as a sound in response to the scan, haptic feedback from the scanner, and / or as a visual display as discussed below.

[0148] By using an intraoral scanner and the computer-implemented methods described above, a preparation surface can be created, evaluated, and adjusted in a single patient session. Because the dental practitioner has more information during the scan, they can adjust the preparation surface in a matter of minutes, rather than waiting for lab results.

[0149] The method of the preceding statement further comprises evaluating the first digital mouth condition according to any one or more of the preceding statements.

[0150] The method discussed above in the first aspect of the disclosure describes several useful ways of assessing the prepared surface and / or the oral situation; these can also be used as part of the assessment of the digital oral situation in the second aspect of the disclosure.

[0151] The method of the second aspect, wherein the returned result further comprises displaying the first digital oral situation according to any one or more of the preceding statements.

[0152] The second aspect can further comprise an embodiment wherein the returned result is based on the display method discussed in the first aspect. As described above in the first aspect, this information can be communicated to the dental technician through a display. This allows the dental technician to decide how to proceed, for example, by letting them know that the prepared surface will allow for an effective dental prosthesis, or that more work needs to be done on the prepared surface, as described above and below.

[0153] An embodiment of the second aspect further comprises:

[0154] detecting at least one problem area in the first digital oral situation; and

[0155] adjusting the prepared surface according to the at least one problem area.

[0156] An embodiment of the second aspect further comprises detecting a problem area and adjusting the prepared surface based on the problem area. The problem area can be detected by the methods described above, and the prepared surface adjusted as described above.

[0157] The intraoral scan allows the dental technician to adjust the prepared surface according to the first digital oral situation. If the initial prepared site is lacking in some way, the dental technician can now make adjustments. For example, in the case where the achievable thickness fails to meet the minimum thickness, the dentist can adjust the prepared surface so that the minimum thickness can be met. Alternatively, as described above, the dental technician can decide to use another material with a smaller minimum thickness. This embodiment allows the dental technician to make decisions based on these multiple sources of information; in a traditional crown procedure, these decisions would be made by the lab, and adjustments would be limited to corrections in the prosthesis itself.

[0158] An embodiment of the second aspect further comprises:

[0159] generating a second digital oral situation comprising the oral situation of the prepared surface with the adjustments through the intraoral scan;

[0160] evaluating the adjusted prepared surface against the problem area; and

[0161] further adjusting the prepared surface where at least one problem area exists.

[0162] In an embodiment of the second aspect, the above process can also be repeated by scanning the oral situation with the adjusted preparation surface, evaluating, and adjusting as described above. As described above, since scanning and evaluation takes at most a few minutes, the preparation surface can be adjusted again relatively quickly. As described below, this adjusted surface can be scanned and evaluated again for further adjustment or confirmation. For example, the process can be repeated several times until the preparation site is found to be valid, or the dental practitioner considers the preparation site to be acceptable.

[0163] An embodiment of the second aspect further comprises:

[0164] detecting that no problem area is present in the first or second digital oral situation; and

[0165] returning a confirmation of the preparation surface.

[0166] An embodiment of the second aspect detects that no problem area is present in the first or second digital oral situation and returns a confirmation of the preparation surface, wherein the confirmation is an evaluation that no known problem was found. If the above method does not detect a problem area, a confirmation can be returned almost immediately. This allows the dental practitioner to have some confidence that the manufactured dental prosthesis will fit the preparation surface when manufacturing the dental prosthesis.

[0167] A system for verifying a preparation surface, wherein the system comprises an intraoral scanner for scanning an oral situation and / or a part thereof, including a preparation surface of a patient on which a dental prosthesis is intended to be placed, and a processor connected to the intraoral scanner for generating at least part of a digital oral situation during scanning, wherein the processor confirms the preparation surface during scanning, and wherein the processor performs a computer-implemented method for verifying the preparation surface during scanning, the computer-implemented method comprising the method according to any of the preceding statements, and wherein a result of comparing the at least one minimum thickness to the at least one attainable thickness determines a confirmation of the preparation site; and a display connected to the processor for visualizing at least part of the digital oral situation during scanning according to any one or more of the preceding statements.

[0168] In a third aspect of the present disclosure, a system for verifying a preparation surface comprises an intraoral scanner, a processor, and a display.

[0169] The system comprises an intraoral scanner for scanning an oral situation or a part thereof, similar to the intraoral scanner described above, similar to those described above in the first aspect. The oral situation or part includes a preparation surface intended for a dental prosthesis, similar to those described above in the first aspect.

[0170] The system also comprises a processor connected to the intraoral scanner. This can be, for example, a computer embedded in the scanner itself, a separate computer, a computer located on the cloud and accessible to the intraoral scanner, etc.

[0171] The processor can be used to verify the prepared surface during scanning - for example by any one or more of the computer-implemented methods described above in the first and / or second aspects. The processor can further be used to verify the prepared surface based on comparing the at least one minimum thickness and the at least one achievable thickness, as described above.

[0172] As described above, the system also comprises a display, for example a computer screen. The display is used to visualize at least a portion of the oral situation, and can use the visualization methods described above in the first and / or second aspects of the present disclosure.

[0173] The method according to any one or more of the preceding items, further comprising manufacturing a dental prosthesis based on the digital dental prosthesis.

[0174] The dental prosthesis can be manufactured using the methods and systems described in the above embodiments. The method of manufacturing the dental prosthesis comprises milling and / or 3D printing.

[0175] References

[0176] Montero, Javier, and Abraham Dib. “The effect of age and prosthodontic status on the clinical and electromyographic assessment of the interocclusal rest space.” The Journal of prosthetic dentistry 121.5 (2019): 791-796; Abstract.

[0177] Item

[0178] 1. A computer-implemented method of evaluating a dental prepared surface, comprising:

[0179] obtaining a digital oral situation and / or a portion thereof, including the prepared surface;

[0180] evaluating at least one achievable thickness based on the prepared surface and the surrounding environment; and

[0181] comparing the at least one achievable thickness to at least one minimum thickness.

[0182] 2. The method according to any one or more of the preceding items, further comprising generating an inner surface for a digital dental prosthesis based on the prepared surface.

[0183] 3. The method of any one or more of the preceding items, further comprising generating an outer surface for the digital prosthesis.

[0184] 4. The method of any one or more of the preceding items, further comprising:

[0185] defining a negative space around the preparation surface based on the digital oral situation; and

[0186] generating an outer surface for the digital prosthesis based on the negative space.

[0187] 5. The method of any one or more of the preceding items, further comprising generating the digital prosthesis based on the inner surface and the outer surface.

[0188] 6. The method of any one or more of the preceding items, further comprising deriving the digital oral situation from an intraoral scanning device.

[0189] 7. The method of any one or more of the preceding items, further comprising adjusting the digital prosthesis and / or the preparation surface by:

[0190] evaluating the digital prosthesis and / or the preparation surface against the at least one minimum thickness and the at least one achievable thickness;

[0191] comparing the at least one minimum thickness and the at least one achievable thickness; and

[0192] in the event of a conflict between the at least one minimum thickness and the at least one achievable thickness, adjusting the digital prosthesis and / or the preparation surface.

[0193] 8. The method of any one or more of the preceding items, further comprising displaying the digital preparation surface and / or the digital prosthesis.

[0194] 9. The method of any one of the preceding items, further comprising:

[0195] evaluating the preparation surface against the problem area based on the at least one achievable thickness;

[0196] displaying the digital preparation surface, the digital oral situation, and / or the digital prosthesis; and

[0197] highlighting the problem area on the digitized preparation surface, the digital oral situation, and / or the digital prosthesis.

[0198] 10. The method of any one or more of the preceding items, further comprising:

[0199] aligning the digital prosthesis with the digital oral situation and / or the digital preparation surface; and

[0200] Display the digital denture and the digital oral situation.

[0201] 11. The method of any one or more of the preceding items, further comprising:

[0202] evaluating the aligned digital denture and the digital oral situation for problem areas;

[0203] displaying the aligned digital denture and the digital oral situation; and

[0204] highlighting the problem areas on the display screen.

[0205] 12. The method of any one or more of the preceding items, further comprising:

[0206] evaluating the aligned digital denture and the digital oral situation for problem areas;

[0207] displaying the aligned digital denture and the digital oral situation; and

[0208] displaying the digital denture and the digital oral situation.

[0209] 13. The method of any one or more of the preceding items, further comprising generating the digital denture in a single patient visit.

[0210] 14. The method of any one or more of the preceding items, further comprising:

[0211] calculating an impact of at least one drill characteristic; and

[0212] adjusting the achievable thickness and / or inner surface based on the impact of the at least one drill characteristic.

[0213] 15. The method of any one or more of the preceding items, further comprising:

[0214] calculating an impact of a plurality of drill radii on the at least one achievable thickness and / or inner surface; and

[0215] selecting at least one drill radius based on the calculation of the impact to the plurality of drill radii.

[0216] 16. The method of any one or more of the preceding items, further comprising selecting a drill by:

[0217] for each of a plurality of drills, estimating a drill wear cost from manufacturing the denture based on the digital denture; and

[0218] selecting a drill according to the estimated cost of drill wear.

[0219] 17. The method of any one or more of the preceding items, further comprising selecting a drilling direction based on the at least one achievable thickness, the digital denture, and / or the digital oral situation.

[0220] 18. The method of any one or more of the preceding items, further comprising:

[0221] detecting at least one undercut region of the preparation surface; and

[0222] adjusting the achievable thickness, the inner surface, and / or the preparation surface according to the undercut region.

[0223] 19. The method of any one or more of the preceding items, further comprising determining at least one undercut region based on the selected insertion direction.

[0224] 20. The method of any one of the preceding items, further comprising:

[0225] evaluating a plurality of insertion directions of the undercut region; and

[0226] selecting an insertion direction from the plurality of insertion directions based on the determined undercut.

[0227] 21. The method of any one or more of the preceding items, further comprising:

[0228] obtaining a coating distance of the outer coating; and

[0229] adjusting the inner surface, the outer surface, and / or the preparation surface based on the coating distance.

[0230] 22. The method of any one or more of the preceding items, further comprising:

[0231] generating at least one parameter for the digital denture; and

[0232] adjusting the digital denture based on the at least one parameter.

[0233] 23. The method of any one or more of the preceding items, further comprising:

[0234] processing the outer surface into a format usable for a carving application; and

[0235] allowing a user to carve the outer surface using the carving application.

[0236] 24. The method of any one or more of the preceding items, further comprising:

[0237] obtaining a cement gap distance for a cement gap;

[0238] adjusting the achievable thickness, the digital denture, and / or the preparation surface based on the cement gap distance.

[0239] 25. The method of any one or more of the preceding items, further comprising selecting at least one prosthetic material by:

[0240] evaluating the at least one minimum thickness based on each of a plurality of prosthetic materials; and

[0241] selecting at least one of the plurality of prosthetic materials based on the evaluation of the at least one minimum thickness.

[0242] 26. The method of any one or more of the preceding items, further comprising selecting at least one prosthetic material by:

[0243] estimating a cost of each of a plurality of prosthetic materials; and

[0244] selecting at least one of the plurality of materials based on the estimated cost.

[0245] 27. The method of any one or more of the preceding items, wherein the oral situation further comprises at least one opposing tooth, the method further comprising:

[0246] identifying at least one opposing tooth surface in the digital oral situation;

[0247] identifying an interocclusal distance; and

[0248] adjusting the achievable thickness and / or outer surface based on the interocclusal distance and the at least one opposing tooth surface.

[0249] 28. The method of any one or more of the preceding items, wherein the oral situation further comprises at least one adjacent tooth, the method further comprising:

[0250] identifying at least one adjacent tooth surface;

[0251] identifying a desired interproximal distance; and

[0252] adjusting the achievable thickness and / or outer surface based on the desired interproximal distance and the at least one adjacent tooth surface.

[0253] 29. The method of any one of the preceding items, wherein the prosthetic comprises: a crown, a bridge, a veneer, an inlay, and / or an onlay.

[0254] 30. A computer program product in a non-transitory medium configured to perform the method of one or more of the preceding items at runtime.

[0255] 31. A method of preparing a surface for preparation with digital assistance during a pre- appointment, comprising:

[0256] preparing a prepared surface in the oral situation;

[0257] generating a first digital oral situation by intraorally scanning the oral situation;

[0258] evaluating the first digital oral situation; and

[0259] returning a result.

[0260] 32. The method according to item 30, further comprising evaluating the first digital oral situation according to any one or more of items 1-7, 14, 18, 21, 24, and / or 27-30;

[0261] 33. The method according to items 30-31, wherein returning the result further comprises displaying the first digital oral situation according to any one or more of items 8-12.

[0262] 34. The method according to items 30-32, wherein evaluating the first digital oral situation further comprises:

[0263] detecting at least one problem area in the first digital oral situation; and

[0264] adjusting the prepared surface based on the at least one problem area.

[0265] 35. The method according to any one of items 30-33, further comprising:

[0266] generating a second digital oral situation by intraorally scanning the oral situation including the adjusted prepared surface;

[0267] evaluating the adjusted prepared surface for the problem area; and

[0268] further adjusting the prepared surface where the at least one problem area is present.

[0269] 36. The method according to items 30-34, wherein evaluating the first and / or second digital oral situation further comprises:

[0270] detecting that no problem area is present in the first or second digital oral situation; and

[0271] returning a confirmation of the prepared surface.

[0272] 37. A system for verifying a prepared surface, wherein the system comprises an intraoral scanner for scanning an oral situation and / or a part thereof, a prepared surface of a patient on which a prosthesis is intended to be placed, and a processor connected to the intraoral scanner for generating at least part of a digital oral situation during scanning, wherein the processor verifies the prepared surface during scanning, and wherein the processor performs a computer-implemented method for verifying a prepared surface during scanning, the computer-implemented method comprising the method according to any of the preceding items, and wherein a result of comparing the at least one minimum thickness and the at least one achievable thickness determines the verification of the prepared site; and a display connected to the processor for visualizing at least part of the digital oral situation during scanning according to any one or more of the preceding items.

[0273] 38. The method according to any one or more of the preceding items, further comprising manufacturing a prosthesis based on the digital prosthesis. BRIEF DESCRIPTION OF DRAWINGS

[0274] The above and / or additional objects, features, and advantages of the disclosure will be further described by the illustrative and non-limiting detailed description of embodiments of the disclosure, described below, with reference to the

[0275] Figure 1 An oral situation to which the disclosure is applicable is shown;

[0276] Figure 2 A prepared surface with a prosthesis is shown;

[0277] Figure 3 A prepared surface with an undercut and a calculation of the inner surface in this case is shown;

[0278] Figure 4 Some relevant distances with respect to the surrounding dentition that can be evaluated and taken into account in the sense of the disclosure are shown;

[0279] Figure 5 A workflow in the sense of the disclosure is shown;

[0280] Figure 6 An embodiment of a workflow for generating a digital prosthesis is shown; and

[0281] Figure 7 A schematic view of a system according to an embodiment of the disclosure is shown. DETAILED DESCRIPTION

[0282] In the following description, reference is made to the accompanying drawings, which show by way of illustration how the disclosure can be practiced.

[0283] Figure 1 An oral situation to which the disclosure is applicable is shown;Figure 1 (a) shows the prosthesis site after the dentist has drilled away a portion of the tooth, leaving a prepared surface 120. Figure 1 (a) also shows the opposing tooth 140 and the adjacent tooth 150. There can be two adjacent teeth in other cases. The intra-oral situation at the time of scanning is represented by the digital 3D representation. Its 2D cross-section can also look similar to Figure 1 (a).

[0284] Figure 1 (b) shows elements of the intra-oral situation relevant for the evaluation of the digital 3D representation according to the present disclosure. As a first step, at least a portion of the prepared surface 120 is identified. When evaluating the space towards the opposing tooth 140 in the occlusal direction, it is not necessary to detail the border between the prepared and unprepared areas of the tooth - it is referred to as the marginal line.

[0285] For the embodiments described here, it is assumed that a single crown prosthesis is to be manufactured using a three-axis milling machine. For this case, the direction 130 in which the milling drill approaches the interior of the prosthesis is also determined during manufacturing. In the example described here, the drilling direction 130 can be chosen as the opposite direction of the insertion direction 131. In the present embodiment, the insertion direction can be calculated as the direction whose dot product with the normals of the facets of the mesh digital 3D representation representing the prepared surface, weighted by the area of the facets, is minimal.

[0286] Figure 1 (b) also shows a crown prosthesis adapted to the intra-oral situation, with an inner surface 110 and an outer surface 100.

[0287] Figure 2 The prepared surface with the prosthesis is shown.

[0288] Figure 2 (a) shows the prepared surface with the prosthesis and illustrates the effect of the drilling compensation when evaluating the thickness of the digital denture. For illustrative purposes, the prepared surface 120 is shown with a zero corner radius at the margin 121, where the margin is in 2D Figure 2 (a) is shown as a 2D point. The ideal inner surface 111 can be described as the ideal inner surface of the crown to be manufactured; the ideal inner surface 111 can be offset outwardly from the prepared surface 120 by the cement gap. Note that, again for illustrative purposes, Figure 2 The cement gap in (a) is large relative to the drill radius. As a value of the achievable thickness at the position where it is at its minimum, a simple evaluation of the crown thickness can reach a distance 192.

[0289] Figure 2(a) also shows a drill 180. Its spherical tip has a non-zero radius 181. It can be seen that 130 is likely a suitable drilling direction, as the drill can access all portions 111 of the ideal inner surface. The drill may not be part of a typical oral cavity situation, as milling is performed on an extraoral machine, but the figure includes a drill to illustrate its geometric relationship with the oral cavity portion. For example, crown material can be milled from a block such as a zirconia blank; that is, the crown can be a sub-volume of that block.

[0290] If drill 180 is to remove all material from the interior of the block until the ideal inner surface 111 of the crown to be milled, its head must move in direction 130 beyond the ideal surface 111. This means that the drill can remove additional material 190 from the block. Accordingly, the achievable thickness of the milled crown at its minimum position is a distance 191, which is a smaller value than distance 192.

[0291] Figure 2 (b) A schematic diagram of a digital prosthesis is shown, here representing a potential crown design for a given preparation section. The diagram illustrates how problems caused by a drill radius larger than the corner radius of the preparation surface are detected during evaluation and visualized on the preparation surface. For a given material, the crown may have a required minimum material thickness 195. To meet this requirement, the inner surface of the crown may need to be set inward from the outer surface 100 to at least surface 118. The software can highlight the problem area 140—at the intersection of surface 118 and preparation surface 120, i.e., where the minimum thickness requirement is not met. However, when considering the drill radius according to this disclosure, it is clear that area 141 could also be a problem area, on both faces of that corner of the preparation section, even if the required surface 118 is not within preparation surface 120. Therefore, it is appropriate to visualize both areas 140 and 141 as problem areas. The magnitude of the problem is the distance from surface 120 to drill bit 180 plus the required thickness of the cement gap (to avoid further complicating the diagram, Figure 2 (b) The adhesive gap area is not shown. The magnitude can be visualized using a color map.

[0292] If it must be manufactured as is Figure 2 (b) For the crown, drilling compensation may be required, such as in Figure 2 As shown in (a), the crown may therefore not achieve the required minimum thickness. However, due to the evaluation and visualization of this disclosure, dental practitioners can identify and resolve the problem before manufacturing the crown, for example by further grinding the preparation portion in region 141 to have an edge radius equal to the drill radius. The patient can then receive a crown with the required thickness that can be placed in place.

[0293] Figure 3The calculation of the preparation surface with undercuts and in this case the inner surface is shown.

[0294] Figure 3 (a) The preparation site 120 with a selected insertion direction 131 that creates an undercut region 122 is shown. Figure 3 (b) The calculation of the inner surface 110 in this case is shown. The undercut can require the removal of additional crown material in the region 179 so that the crown can be seated. Also in this case, the difference in the actual thickness of the crown and the distance between the preparation surface 120 and the outer surface of the crown 100 is greater than the cement gap value. It can be important to take into account the effect of the undercut in the evaluation, a simple evaluation of the crown thickness would lead to a false sense of security.

[0295] Figure 4 Some relevant distances relative to the surrounding dentition are shown, which can be evaluated and taken into account in the sense of the present disclosure. According to Figure 4 (a), when designing the outer surface of the crown, the relative part 140 of the patient's dentition should be taken into account. The minimum distance 160 from the inner surface 110 to the relative part 140 can need to be equal to or greater than the sum of the material-based minimum thickness and any desired distance to the relative surface. The minimum distance 160 can be calculated for the digital 3D representation and compared to the above requirement. Thus, without designing the outer surface of the prosthesis (which is therefore not shown in Figure 4 (a), the feasibility of the crown design can be determined. Similar reasoning would apply to the distance to the adjacent teeth.

[0296] If the actual minimum distance 160 is smaller than the required value, the dental practitioner can be informed that the preparation-to-opposite gap is insufficient. Preferably, the minimum distance 160 is calculated as the distance between the two closest points on the surfaces. It can also be approximated as the minimum distance between the two surfaces in the drilling direction or insertion direction.

[0297] Figure 4 (a) also shows the problem region 170, which is visualized in the 2D cross-section as a thick line, where the distance between the inner crown surface 110 and the relative dentition 140 can be smaller than the required distance. Figure 4 The visualization in (a) shows where the drill can touch the inner crown surface 110. Figure 4 (b) shows an alternative visualization, where the problem region 170 is drawn as the intersection of the drilling volume during drilling when the drill touches the inner surface and the prepared surface 120. Figure 4 The variant in (a) can be more illustrative, as it clearly shows that the problem is due to the drilling compensation. Figure 4 The variant in (b) can be easier to understand, as it contains only parts of the digital 3D representation obtained using the scanner. Note that the black and white Figure 4(a) and 4(b) are very simple visualizations. If color is available, it can be used to visualize the magnitude of the problem.

[0298] Figure 5 A workflow in the sense of the present disclosure is illustrated. A dental practitioner can prepare a preparation surface in step 200 and then scan the preparation surface and the surrounding environment using an intraoral scanner in step 210. The preparation surface can then be evaluated and visualized in step 220. If the preparation has problematic areas, the dental practitioner can be informed and return to steps 200 to 220 to further prepare the preparation surface, which is then scanned again. When the subsequent evaluation shows no more problematic areas, the scan can be used to design and manufacture a prosthesis in step 230.

[0299] Figure 6 An embodiment of a workflow for generating a digital denture is shown.

[0300] First, in step 610, the patient is scanned with an intraoral scanner. This generates a three-dimensional model of the patient's mouth situation. The 3D digital model can be based on, for example, voxels, meshes, and / or a combination of the above.

[0301] Next, in step 620, the preparation surface is detected. This can be done by manual annotation by the dentist. It can also be done with the help of or completely by software trained to make such annotations, for example, by detecting the edge between tooth and gum, segmenting the tooth scan, and detecting the preparation site.

[0302] Next, in step 630, the preparation surface is evaluated by calculating the distance between the detected preparation surface and the surrounding environment. This distance can be used as a basis for the at least one achievable thickness and / or negative space. This provides a set of physical constraints for the generated crown to fit in. The dentist can manually set deviations from other teeth, for example, to shave off a bit from an adjacent tooth to allow for a particularly tight fit. The preparation surface can also be evaluated by calculating the distance from one part of the preparation surface to another part of the preparation surface, for example, to ensure that the preparation surface at least meets a minimum diameter.

[0303] In step 640, an initial crown outer surface is generated for the preparation surface based on the at least one achievable thickness and / or negative space. This can be selected from a library, for example, or designed by an automatic algorithm, for example, a neural network trained to generate crown outer surfaces. At this point, it can still extend beyond the margin line, but it should satisfy the constraints imposed by the negative space and deviations.

[0304] For example, this can initially be generated from a library crown and then adjusted by at least one parameter of the outer surface, as described above.

[0305] The result is a digital 3D model of the outer surface of the crown.

[0306] In step 650, an initial inner surface of the crown is generated. This is based on the scan of the preparation site. It can be adjusted to allow for cement gaps, for example to allow for an extra 0.1 mm around the preparation surface. It can also be adjusted with respect to undercuts, for example to have more of the lower part under overhangs than the upper part, thus making insertion of the crown difficult. The inner surface can be based on the preparation surface, but adjusted so that undercut parts are straightened for insertion.

[0307] In step 660, the crown is generated. Both the initial outer surface and the initial inner surface are in the digital mouth situation, assigned certain values in Euclidean space. This means that they can be joined where they are interested, for example for each point on the mesh model of the initial outer surface, find the closest point on the initial inner surface. If these points are lined up, anything outside of that line can be discarded, and at these points the model can be stitched together on both the initial inner surface and the initial outer surface to generate the digital crown.

[0308] Alternatively, the edge lines can be detected by edge detection, and a line drawn there. Both the outer surface and the inner surface can be attached at the edge lines. Once the digital crown is generated through this process, it can be further processed to make it look better, i.e. to reduce and regularize its mesh, and to make the stitching smoother.

[0309] The digital crown can be inserted into the digital mouth situation and displayed, allowing both the dentist and the patient to see what it looks like. However, it can still need to be evaluated.

[0310] Step 670 is to evaluate the crown. In evaluating the digital crown, a minimum thickness can be calculated based on the material. The material can be chosen by the user, or alternatively, the thicknesses of different materials can be evaluated and the feasible options presented to the user of the software.

[0311] Likewise, the manufacturing method can also be evaluated by the choice of the user or by the software evaluating different options and suggesting the most feasible one based on criteria such as cost, strength, etc. The methods of manufacturing include milling and printing.

[0312] If the chosen manufacturing method is milling, then drilling compensation should also be considered at the evaluation.

[0313] In the case where certain minimum thicknesses are not met, for example between opposing teeth, the surrounding environment or the preparation surface can be adjusted in the 3D digital model.

[0314] As a further step, the dentist can make adjustments to the digital denture. This can be done, for example, by a sculpting application or by software trained to perform such adjustments.

[0315] The dentist can choose to re-evaluate the digital denture, or can choose to accept the digital denture as it is. It can need further evaluation against manufacturing specifications before manufacturing. Likewise, the digital denture can be rendered in the digital oral situation for viewing by the dentist and the patient.

[0316] If the digital denture is not valid in some areas, the dentist can also choose to change the digital oral situation due to a conflict between the negative space / achievable thickness and the digital denture.

[0317] The process can be iterated until an acceptable digital denture is found, i.e. steps 640 to 670 are repeated. Once an acceptable digital denture has been generated, it can be manufactured in step 680.

[0318] Figure 7 A schematic view of a system according to an embodiment of the disclosure is shown. The system 100 comprises a computer device 102 comprising a computer readable medium 104 and a processor 103. The system further comprises a display, here a visual display unit 107, an input unit such as a computer keyboard 105, and a computer mouse 106 for inputting data and activating virtual buttons in the visualizations on the visual display unit 107. The visual display unit 107 can for example be a computer screen.

[0319] The computer device 102 is capable of obtaining a digital representation of at least a portion of, for example, a patient's oral situation by means of an image capturing device 101 b. The obtained digital representation can be stored in the computer readable medium 104 and provided to the processor 103.

[0320] The computer device 102 is also capable of receiving a digital 3D representation of, for example, the surface of a patient's set of teeth and gums from a 3D scanning device 101 a, for example an intraoral scanner, such as a TRIOS intraoral scanner manufactured by 3shape TRIOS A / S, or of receiving scanning data from such a 3D scanning device and forming a digital 3D representation of a patient's oral situation based on such scanning data. The received or formed digital 3D representation can be stored in the computer readable medium 104 and provided to the microprocessor 103.

[0321] The system 100 is configured to allow an operator to design a custom denture using information obtained from a bone scan and / or a surface scan, and to set limitations based on predetermined design criteria. This can for example be achieved by displaying a digital representation of a patient's jaw bone on the visual display unit 107, on which the operator can then visualize his / her repair design with respect to the surface of the patient's jaw bone.

[0322] The system comprises a unit 108 for transmitting the digital design, e.g. the digital dental prosthesis, as output data to a manufacturing machine for generating a dental appliance, e.g. a custom dental restoration, to a computer-aided manufacturing (CAM) device 109, e.g. for manufacturing a custom dental restoration, or to another computer system, e.g. located at a milling or printing center where custom dental restorations are manufactured. The unit for transmission can be a wired or wireless connection, and the transmission can be done, e.g. using the internet or a file transfer protocol (FTP).

[0323] The 3D scanning of the patient's oral situation using the 3D scanning device 101a and / or the image capturing device 101b can be performed at the dentist's office, while the manufacturing of the custom dental restoration can be performed at a dental laboratory. In this case, the digital oral situation acquired from the scanning device and / or the digital dental prosthesis can be provided over an internet connection between the dentist and the dental laboratory.

[0324] The system 100 as shown is an illustrative example. For example, the computer device 102 can comprise more than one processor 103 and / or more than one computer readable medium 104, the visual display unit 107 can be integrated in the computer device 102 or separate from the computer device 102, etc.

[0325] Although some embodiments have been described and shown in detail, the present disclosure is not limited to them but can also be embodied in other ways within the scope of the subject matter defined in the appended claims. In particular, it is to be understood that other embodiments can be utilized and structural and functional modifications can be made without departing from the scope of the present disclosure.

[0326] In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that several means are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these means cannot be used to advantage.

[0327] A claim can refer to any one of the preceding claims, and "any" is understood to mean "any one or more of the preceding claims".

[0328] The term "obtaining" used in this specification can refer to physically acquiring, e.g. a medical image, using a medical imaging device, but it can also refer to, e.g. loading a previously acquired image or digital representation into a computer.

[0329] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0330] The features of the methods described above and below can be implemented in software and executed upon data processing systems or other processing apparatuses caused by the execution of computer executable instructions. The instructions can be program code means loaded in a memory, such as a RAM, from a storage medium or from a computer network. Alternatively, the described features can be implemented by hardwired circuitry, without software, or in combination with software.

Claims

1. A computer-implemented method for evaluating a prepared tooth surface (120), comprising: Obtaining digital oral conditions and / or a portion thereof, including a preparation surface (120), wherein the preparation surface is configured to receive digital dentures; Evaluate at least one achievable thickness, wherein the achievable thickness is configured as the distance between the preparation surface (120) and the surrounding environment, the surrounding environment including portions of a digital oral environment that are not part of the preparation surface (120); and The method compares the at least one achievable thickness with at least one minimum thickness according to the requirements of the digital denture, characterized in that the method includes detecting the preparation surface (120) by using trained software to identify teeth by segmenting the oral cavity and identifying the preparation surface (120) based on the shape of the teeth.

2. The method of claim 1, further comprising generating an inner surface (110) for the digital denture based on the prepared surface (120).

3. The method of claim 2, further comprising generating an outer surface (100) for the digital denture.

4. The method according to claim 3, further comprising generating the digital denture based on the inner surface (110) and the outer surface (100).

5. The method of claim 1, further comprising adjusting the digital denture and / or the preparation surface (120) by: The digital denture and / or the prepared surface (120) are evaluated for the at least one minimum thickness and the at least one achievable thickness. Compare the at least one minimum thickness with the at least one achievable thickness; and In the event of a conflict between at least one of the minimum thicknesses and at least one of the at least achievable thicknesses, the digital denture and / or the preparation surface (120) shall be adjusted.

6. The method of claim 1, further comprising displaying a digital preparation surface, the digital oral cavity condition, and / or the digital denture.

7. The method according to claim 6, further comprising: The problem area of ​​the prepared surface (120) is evaluated based on the at least one achievable thickness; Displaying the digital preparation surface, the digital oral cavity condition, and / or the digital denture; as well as Highlight the problem areas on the digital preparation surface, the digital oral cavity condition, and / or the digital denture.

8. The method according to claim 6, further comprising: Align the digital denture with the digital oral condition and / or the digital preparation surface; as well as The digital dentures and the digital oral cavity condition are displayed.

9. The method according to claim 2, further comprising: Calculate the impact of at least one drilling rig characteristic; as well as Based on the influence of the at least one drilling rig characteristic, adjust at least one of the at least one achievable thicknesses and / or the inner surface (110).

10. The method according to claim 2, further comprising: Calculate the effect of multiple drilling radii on the at least one achievable thickness and / or the inner surface (110); as well as At least one drilling rig radius is selected based on calculations of the impact on the plurality of drilling rig radii.

11. The method according to claim 2, further comprising: Detect at least one undercut region (122) of the prepared surface (120). as well as Based on the at least one undercut region (122), adjust at least one of the at least one achievable thickness, the inner surface (110), and / or the prepared surface (120).

12. The method of claim 1, further comprising selecting at least one prosthetic material in the following manner: The minimum thickness is evaluated based on each of a variety of prosthetic materials; and At least one of the various prosthetic materials is selected based on an evaluation of the minimum thickness.

13. The method of claim 1, further comprising selecting at least one prosthetic material in the following manner: Estimate the cost of each of the various prosthetic materials; and At least one of the various prosthetic materials is selected based on the estimated cost.

14. The method according to claim 3, wherein, The oral cavity condition also includes at least one opposing tooth, and the method further includes: Identify at least one opposing tooth surface in the digital oral cavity condition; Identify the interocclusal distance (160); and The at least one of the at least achievable thicknesses and / or the outer surface (100) is adjusted based on the occlusal surface distance (160) and the at least one opposing tooth surface.

15. The method according to claim 3, wherein, The oral cavity condition also includes at least one adjacent tooth (150), and the method further includes: Identify at least one adjacent tooth surface; Identify the desired neighbor distance; and Adjust at least one of the at least achievable thicknesses and / or the outer surface (100) based on the desired interproximal distance and the at least one adjacent tooth surface.

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