Design and manufacturing methods for custom orthodontic brackets

Abstract

To reduce occurrence of variations in designed objects due to skill, knowledge, experience and proficiency of operators in design work, improve manufacturing efficiency, reduce a cost required for the manufacture, and perform customization processing to be applied to each bracket with minimum labor and time.SOLUTION: A design and manufacturing method of orthodontic brackets includes: manufacturing brackets of ready-made shape (collectively manufacturing large quantities); collectively converting shape data of attachment surfaces and attachment sites of tooth surfaces of patients set in the design based on tooth rows and tooth surface shapes of the patients, into a coordinate system of a customized processing tool; creating processing data such as NC data on the coordinate system; and customizing each bracket attachment surface by customizing the manufactured base part of ready-made shape, while improving manufacturing efficiency.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a method for designing and manufacturing a custom bracket for orthodontics having an attachment surface adapted to the tooth surface shape unique to each patient. 【Background Art】 【0002】 In orthodontic treatment using brackets, there are cases where brackets of a ready-made shape are used and cases where custom brackets are used, in which the shape of the attachment surface is processed according to the individual dentition state and tooth surface shape for each patient. In the present invention, a custom bracket refers to an orthodontic bracket whose attachment surface shape is processed according to the unique tooth surface shape and dentition shape for each patient. Customization of a bracket means processing an orthodontic bracket into a shape corresponding to the unique tooth surface shape in the orthodontic bracket attachment part in a patient's oral cavity. 【0003】 In orthodontic treatment, it is necessary to appropriately bend the wire so that the optimal force in each treatment process is applied to the dentition in the intended direction according to the condition of the patient's dentition. However, when using a ready-made shape bracket, since the position and orientation of the slots and holes are determined by the patient's tooth surface, it is necessary to bend the wire so as to apply the force required for treatment and to perform additional bending to pass the wire through each slot and hole. However, in many cases at present, it is difficult to balance the patient's dentition condition and the force application for treatment. Therefore, in many cases, it is often necessary to perform treatment steps that require labor, such as dividing the treatment steps that can usually be advanced in one step into several steps and replacing the wire each time. 【0004】 As described above, even in cases where there are significant restrictions on the attachment position and direction in the ready-made shape, by using custom brackets whose attachment surface shape of each bracket is processed and adjusted along the patient's tooth surface shape, it becomes possible to perform a design that separately considers the dentition condition and the position and orientation of the slots and holes. Therefore, the degree of freedom in the attachment position and direction to the patient's tooth surface increases, and it becomes easier to adhesively fix in the desired direction at the necessary parts for treatment. 【0005】 Patent Document 1 describes a method for customizing orthodontic brackets, in which shape data for the bracket body having a slot for receiving a wire is prepared in advance in a computer. This article describes a technique in which the shape of the bracket's tooth surface bonding surface is calculated directly from the patient's tooth surface shape, exported to a high-speed prototype creation device to produce a wax prototype, and then alloy is injected to form the orthodontic bracket. Indeed, designing in this way allows for the bonding surface to be positioned and bonded to the correct location on the patient's unique tooth surface, and furthermore, it is possible to design a shape in which the slot is directed to the desired position and direction. However, in order to uniquely and correctly position the orthodontic bracket on a tooth surface that is composed almost entirely of curved surfaces, the surface area of ​​the adhesive surface of the orthodontic bracket must be considerably large. As a result, after the orthodontic bracket is bonded and fixed in place, the patient experiences a strong feeling of discomfort that can be directly felt on the tooth surface. Furthermore, during the design phase, the operator needs to determine the outline of the adhesive surface (the contour of the adhesive area) when creating the data for the adhesive surface. This requires experience and knowledge, placing a significant burden on the operator. This can lead to increased design time and the fact that the validity of the customized design depends on the operator's skill, making it impossible to completely eliminate the possibility of compromising the stability of quality. Furthermore, a manufacturing challenge is that the customized design process is difficult to standardize and automate, making mass production difficult. Additionally, there is a time lag between taking an impression of the patient's oral cavity and fitting the device. As a result, manufacturing costs can be high. Furthermore, attaching these custom brackets to the designated position on the patient's tooth surface is difficult and time-consuming, placing a significant burden on both the practitioner and the patient. When using light-curing adhesives with metal brackets, there are many problems, especially in areas with large bonding surfaces such as molars, where light may be blocked, potentially preventing curing. [Prior art documents] [Patent Documents] 【0006】 [Patent Document 1] Patent No. 5492965 [Overview of the project] [Problems that the invention aims to solve] 【0007】 This invention reduces variations in designs caused by the skill, knowledge, experience, and expertise of the designer during the design process, thereby improving manufacturing efficiency, reducing manufacturing costs, and enabling customized processing of each bracket with minimal effort and time. [Means for solving the problem] 【0008】 The above problem is solved by manufacturing pre-shaped brackets (in bulk quantities), converting the shape data of the bonding surface and the area on the patient's tooth surface to the coordinate system of a customization jig, creating machining data such as NC data on that coordinate system, and then customizing the manufactured pre-formed base part, thereby improving manufacturing efficiency while customizing the bonding surface of each bracket. 【0009】 Instead of manufacturing a shape that replicates the individual patient's adhesive surface shape in advance, the process is divided into creating a pre-existing shape first and then performing custom processing. This allows for more efficient productivity and customization compared to conventional methods, enabling faster and more accurate custom processing. 【0010】 The present invention relates to a method for designing and manufacturing orthodontic brackets, a) A process for manufacturing a pre-shaped bracket having an upper part with a slot or hole for passing a wire through, and a base part that is post-processed into a three-dimensional shape corresponding to the patient's unique tooth surface shape. b) Based on the dental arch shape data obtained by scanning the patient's dentition, or by measuring a model obtained by replicating the patient's dentition, A process of adjusting the shape data of the pre-shaped bracket and the tooth shape data on a computer to a positional relationship desirable for orthodontic treatment. c) A process on a computer to divide the data obtained in step b into individual teeth while maintaining the positional relationship between the pre-shaped bracket and the patient's tooth surface data. d) A step of using a computer to align the data obtained in step c with the coordinate system of the processing machine and to calculate NC data for processing the base portion into a three-dimensional shape corresponding to the tooth surface shape of the patient. e) A method characterized by including the step of using a machining tool to machine the base portion of a pre-formed bracket into a three-dimensional shape corresponding to the patient's unique tooth surface shape, based on the NC data. [Effects of the Invention] 【0011】 By manufacturing pre-designed brackets with pre-created data and then customizing them, the effort required for design work is reduced, design time is shortened, and customization can be achieved with minimal processing after the manufacturing of the pre-designed brackets. Rather than simply adding the time required for manufacturing the pre-designed brackets and the time required for customization, by proceeding with the manufacturing of the pre-designed brackets and customization in parallel, custom brackets can be manufactured in a significantly faster time compared to manufacturing pre-designed brackets and performing customization each time an order is received. As a result, it is expected that the time from the patient's initial consultation to bracket placement will be shortened, and treatment can be started earlier. 【0012】 Since the prefabricated shape brackets have limited shape variations, it is easy to mass-produce them at low cost regardless of fluctuations in demand. In cases where customization is not required, prefabricated shape brackets can be supplied, enabling both mass production of off-the-shelf products and production of brackets for customization with limited facilities at the same time. This allows for flexible response to sudden changes in the trend of orthodontic treatment demand. This has many advantages for manufacturers, such as reducing the variety of inventory, saving storage space, reducing the need for prefabricated shape brackets with few usage opportunities included in the lineup, and reducing the number of varieties. 【0013】 Furthermore, it is possible to mass-produce prefabricated shape brackets that do not require customization and orthodontic brackets with customized shapes using the same facilities up to a certain point, which can greatly contribute to building a system that allows manufacturers to efficiently and flexibly utilize and supply according to demand. 【Brief Description of Drawings】 【0014】 [Figure 1] It is a schematic diagram showing a series of processes of the present invention. [Figure 2A] It is a schematic diagram showing the process of converting from the coordinates of patient dentition data to the coordinates of the processing device. A schematic diagram of positioning a prefabricated shape bracket on a patient dentition model. [Figure 2B] It is a schematic diagram when rotating and moving the reference plane of the processing jig from the slot part of the positioned prefabricated shape bracket to the reference plane of the processing jig while referring to the reference plane. [Figure 2C] An image diagram when the prefabricated shape bracket is set on the processing coordinates. [Figure 2D] A diagram showing an example of the positional relationship before and after coordinate conversion. [Figure 3A] Figure 3 is a schematic diagram showing the state where the off-the-shelf bracket is positioned and the state where the bracket after customization is returned to the coordinates on the patient dentition model. Figure 3A is an example of the display of the patient's dentition data. [Figure 3B] [Figure 3A] is an example of the display of the state where the brackets are arranged at preferable positions for each tooth on the dentition. [Figure 3C]After positioning and arranging each bracket in [Figure 3B], the dental data of the patient is hidden. [Figure 3D] This is an example showing the custom - processed brackets arranged and displayed at the positions of each bracket in [Figure 3C]. [Figure 4] This is a schematic diagram showing an example of a state where a plurality of brackets are connected by a runner. [Figure 5A] Figure 5 is a schematic diagram showing an example of an off - the - shelf bracket manufactured deep enough so that shapes such as grooves remain even after customization. Figure 5A is a schematic diagram of an off - the - shelf bracket with a groove formed in the base part. [Figure 5B] A schematic diagram of the off - the - shelf bracket after custom - processing Figure 5A. [Figure 5C] A schematic diagram of an off - the - shelf bracket with a groove shape different from that of Figure 5A. [Figure 5D] A schematic diagram of the off - the - shelf bracket after custom - processing Figure 5D. [Figure 6] This is a schematic diagram showing the structure of an off - the - shelf bracket. 【Explanation of Reference Signs】 【0015】 1 Dental data of the patient 2 Off - the - shelf bracket data in a state where positioning is performed for each tooth 3 Fixture for fixing the off - the - shelf bracket 4 Cross - section of the dental surface data of the patient 5 Bracket after customization 6 An example of a reference plane for grasping and positioning the difference between the coordinates on the dental arch and the coordinates on the processing machine 9 Upper part of the off - the - shelf bracket 10 One piece of tooth data constituting the dental data 20 One piece of off - the - shelf bracket data 21 Bracket data in a state of being positioned on the dental arch 30 Off - the - shelf bracket 60 Runner shape connecting a plurality of off - the - shelf brackets 70 A pre-shaped bracket with a groove formed in the base. Standard shaped bracket after custom machining of 71 70 A pre-formed bracket with a groove shape different from the 80 70 example. Standard shaped bracket after custom processing of 81 80 90 Base part of pre-shaped bracket 201 Pre-shaped bracket fixed to a machining jig [Modes for carrying out the invention] 【0016】 According to the design and manufacturing method of custom orthodontic brackets of the present invention, a pre-shaped bracket is manufactured comprising a base portion having a slot and / or hole for passing a wire through, and the opposite side having sufficient volume to allow a surface to be attached to the patient's specific tooth surface to be formed by post-processing. Data obtained by directly scanning the patient's oral cavity with an intraoral scanner, or data obtained by scanning a model obtained by filling a negative mold obtained from an impression of the patient's oral cavity with plaster and hardening it using an intraoral scanner, a stationary contact type, or a non-contact scanner, and the data of the pre-shaped brackets mentioned above are aligned to the positional relationship desired for orthodontic treatment, and while maintaining the positional relationship between each pre-shaped bracket and the surface shape data of each of the patient's teeth, the slot-side point of the pre-shaped bracket data, which has a uniquely determined direction and position, is aligned with the coordinate system on the custom processing jig, and the orientation of the patient's tooth surface data is moved to a direction suitable for post-processing, and customized processing data that can be used for processing under the coordinate system during customized processing is calculated. By placing a pre-shaped bracket in a jig for custom processing and using the aforementioned processing data to customize the surface that attaches to the patient's tooth surface, We design and manufacture custom orthodontic brackets that feature customized processing to accommodate the unique oral conditions of each patient. 【0017】 The pre-formed bracket of the present invention has an upper part having a slot or hole for passing a wire through, and a base part that is post-processed into a three-dimensional shape corresponding to the patient's unique tooth surface shape. (Figure 6) The upper part is the part for attaching the wire, and the base part of the pre-formed bracket is the part that is processed (customized) using a processing machine to create a three-dimensional shape corresponding to the patient's unique tooth surface shape. 【0018】 It is preferable that the base of a pre-shaped bracket has irregularities during manufacturing. The depth of the irregularities should be such that they remain even after custom processing, and these irregularities include grooves, grids, fine patterns, textured surfaces, notches, and other shapes. By having irregularities on the base of a pre-shaped bracket, when bonding the bracket to the tooth surface, the light required to cure the light-curing adhesive can reach deeper into the tooth surface more easily. In addition, it is expected that the adhesive will spread more evenly into the grooves of the bracket, contributing to improved bonding strength. Furthermore, it becomes easier to insert a removal tool when removing the bracket from the tooth surface after treatment is complete. 【0019】 Methods such as mold molding, machining, and additive manufacturing using 3D printers can be used to manufacture pre-shaped brackets. Furthermore, the materials used for orthodontic brackets can include metals, cured resins, ceramics such as zirconia and alumina, porcelain, and materials obtained by mixing, blending, or combining two or more of these materials. From the viewpoint of processability, it is preferable to create the shape of a pre-shaped bracket by layering ceramic slurry, then sintering it before custom processing, or to form a pre-shaped bracket using additive manufacturing of resin or ceramic slurry. It is also preferable to manufacture a pre-shaped bracket using ceramic slurry and then sinter it after custom processing. 【0020】 Pre-formed brackets may be manufactured individually, or in groups directly connected or joined with runners. They can be configured to facilitate subsequent surface treatment and customization processes, and to allow for easy identification. For example, it is preferable to arrange multiple brackets in series and connect adjacent brackets with rod-shaped runners, or to connect them with flat runners that have notches that can be easily broken off by hand. In addition, the product can be manufactured by arranging an appropriate number of units in an appropriate shape, such as 7 units in 4 rows, in a rectangular grid pattern to facilitate handling or to prevent breakage, and then using additive manufacturing, casting, cutting, grinding, or a combination of these methods as appropriate. 【0021】 By connecting multiple brackets in this way and handling them as a single unit, surface treatment can be performed all at once, making it more efficient. Individual brackets do not need to be identified after barrel polishing. Set-up during custom processing is easy and reliable. Furthermore, it allows for management and work on each patient's set as a single shape, or each pre-existing shape as a separate shape. 【0022】 Furthermore, it is preferable to design the runner to be appropriately sized and shaped so that it can be used as a positioning guide to attach the bracket to the correct position during treatment. It is even preferable to make the positioning guide thin and slender so that it can be easily broken off by hand to make it easier to achieve its intended purpose. This is expected to shorten treatment time and reduce the time burden on the operator and the patient, as well as the burden on the patient associated with treatment. 【0023】 The slot for receiving the wire of a pre-formed orthodontic bracket may be uniquely oriented, installed, and fixed to a post-processing positioning jig having a shape that fits into the slot portion and the groove for receiving the wire, so that it can be easily positioned on a fixing shaft installed in a post-processing device when the bonding surface for bonding to the patient's tooth surface is customized. 【0024】 CAD data for pre-shaped brackets, used to position pre-shaped bracket data appropriately on patient dentition data within a CAD application, can be pre-registered in the CAD library. 【0025】 After positioning the brackets using a CAD application, it is also preferable to design the core to be used in the setup process. In this case, by combining the patient's tooth data and the positioned bracket data using a logical OR operation, and then offsetting only the shape data of the part to be formed as the core outward by a certain width to create a three-dimensional shape, a high-precision positioning core can be designed simply, quickly, and efficiently. The designed core can be manufactured by additive manufacturing, casting, machining, grinding, or by using a combination of these methods as appropriate. The material of the core is not particularly limited, as long as the bracket can be set in the correct position on the patient's tooth surface and the core can be easily removed after adhesive fixation. 【0026】 To customize a pre-shaped bracket, a fixing jig is used to position it correctly and orient it. Then, the slot portion is clamped and fixed from both sides, or from three or more directions, to prevent movement due to stress during processing. The jig may be equipped with multiple brackets, as long as it does not interfere with the customized machining process. For example, a set of brackets for one patient can be fixed to the jig and machined together. Following this procedure ensures that the exact set of brackets required for each patient is assembled and shipped without errors or omissions, thereby increasing work efficiency. Furthermore, it is possible to prepare a sub-jigly with a set of brackets for one patient fixed in a single row, and then mount multiple sub-jigs onto a single main jig for processing. 【0027】 After using a jig to customize a pre-shaped bracket, a guide shape may be used to position it correctly and orient it, and then a light-curable resin may be poured into the slot and cured by light irradiation to temporarily fix the pre-shaped orthodontic bracket in place. The hardened resin can be removed after custom processing by methods such as scraping, chipping, or heating to melt it away. These methods can also be used when temporarily attaching a custom-processed bracket to the core. 【0028】 When customizing pre-shaped brackets, appropriate equipment and methods can be selected from cutting machines, lathes, laser processing machines, water jet processing machines, etc., taking into consideration the bracket material, the number of units to be processed, the acceptable processing cost, processing time, and processing accuracy. In implementing the present invention, the post-processing equipment and methods are not limited to those listed herein, and appropriate equipment and methods can be freely selected and used as long as they do not impair the purpose. 【0029】 By manufacturing pre-designed brackets with pre-created data and then customizing them, the effort required for design work is reduced, design time is shortened, and customization can be achieved with minimal processing after the manufacturing of the pre-designed brackets. Instead of simply adding the time required for manufacturing the pre-designed brackets and the time required for customization, the manufacturing of the pre-designed brackets and the customization can be carried out in parallel. Compared to manufacturing pre-shaped brackets and then performing custom processing each time an order is received, custom brackets can be manufactured in approximately half to one-tenth of the time. This is expected to shorten the time from the patient's initial consultation to bracket placement, allowing treatment to begin earlier. 【0030】 Because standard-shaped brackets have limited shape variations, they can be easily mass-produced and stockpiled at low cost regardless of fluctuations in demand. Since standard-shaped brackets can be supplied for cases that do not require custom processing, both standard product manufacturing and bracket manufacturing for custom processing can be done simultaneously with limited equipment. This allows for flexible responses to rapid changes in the demand for orthodontic treatment. This offers manufacturers several advantages, including a reduction in the variety of items in stock, saving storage space, and a decrease in the need to include less frequently used, pre-shaped brackets in the product lineup, thus reducing the number of product variations. For example, while it was previously necessary to prepare 8 to 12 types of pre-shaped brackets for each part (up, down, left, right, etc.) as a single product group, the flexibility provided by custom processing allows for advantages such as requiring only 4 to 6 types of shapes. Furthermore, if pre-shaped brackets are manufactured using molds, the number of molds required can also be reduced, potentially saving tens of millions of yen in mold production costs per shape, depending on the number of molds produced. In addition, storage space for molds, maintenance costs, and labor can be reduced. [Examples] 【0031】 We designed six types of pre-shaped brackets to match the morphological characteristics and sizes of each part of the tooth, and created data that can be handled by computer applications such as CAD and CAM. Here, the six types of shape data are designated for the maxillary central incisors, maxillary lateral incisors and canines, mandibular anterior teeth, upper and lower premolars, and upper and lower molars, respectively. Zirconia powder TZ-3Y-E (manufactured by Tosoh Corporation) was dispersed in a binder resin to prepare a zirconia slurry with a powder-to-liquid ratio of 50:50. Using this zirconia slurry, the six types of pre-shaped brackets mentioned above were fabricated with a layer thickness of 50 μm using a ceramic 3D printer SZ-2500 (SK Fine Co., Ltd.). After washing away excess slurry from the fabricated objects with water and manually removing the supports, the zirconia was sintered using a DEKEMA664i furnace (manufactured by DEMEKA DENTAL-KERAMIKOFEN), and then the surface was polished using a barrel polishing machine (Chipton Co., Ltd.) to complete the pre-shaped brackets. Using a 3Shape intraoral scanner, we scanned an orthodontic case model that mimicked the patient's oral cavity to obtain STL data of the patient's dentition. Using Rhinoceros (manufactured by Robert McNeel & Associates), a general-purpose 3D CAD software, we selected the appropriate location data from the aforementioned pre-shaped bracket data for each tooth based on this data and performed positioning. During positioning, there are points where tooth surface data and bracket shape data intersect. By using logical calculations to remove the pre-existing bracket shape data from this overlapping area, a curved shape that matches the patient's unique tooth surface is formed, generating a customized shape. On the other hand, the sides and vertices of the pre-shaped bracket that have slots or holes are defined during the design phase as specific points for positioning. By setting and fixing these specific points for positioning to coincide with the positioning reference points of the custom machining jig, the orientation and direction of the pre-shaped bracket data and the actual object will coincide at the machining origin. After custom machining, the position and orientation were aligned to match the specific points used for positioning in the data when returning to the original coordinate system. For coordinate transformation, commonly available commands in CAD and CAM, such as move and rotate commands, were used in appropriate combinations. This allowed the brackets, with their custom shape and position as designed in CAD, to be reproduced as actual orthodontic case models and custom brackets. Surface deviation analysis using GOM Inspect (manufactured by GOM), an application that can overlay two different data sets and display their degree of agreement, confirmed that the dimensional difference between the design data and the actual object was 50 μm or less, indicating sufficient accuracy for practical use. [Industrial applicability] 【0032】 According to the design and manufacturing method for custom orthodontic brackets of the present invention, custom orthodontic brackets can be manufactured with high efficiency, in a short time, and at low cost.

Claims

[Claim 1] A method for designing and manufacturing orthodontic brackets, a) A process for manufacturing a pre-shaped bracket having an upper part with a slot or hole for passing a wire through, and a base part that is post-processed into a three-dimensional shape corresponding to the patient's unique tooth surface shape. b) Based on the dental arch shape data obtained by scanning the patient's dentition, or by measuring a model obtained by replicating the patient's dentition, A process of adjusting the shape data of the pre-shaped bracket and the tooth shape data on a computer to a positional relationship desirable for orthodontic treatment. c) A process on a computer to divide the data obtained in step b into individual teeth while maintaining the positional relationship between the pre-shaped bracket and the patient's tooth surface data. d) A step of using a computer to align the data obtained in step c with the coordinate system of the processing machine and to calculate NC data for processing the base portion into a three-dimensional shape corresponding to the tooth surface shape of the patient. e) A process of using a machining tool to machine the base portion of a pre-shaped bracket into a three-dimensional shape corresponding to the patient's unique tooth surface shape, based on the aforementioned NC data. A method characterized by including the following. [Claim 2] Step d is, A step of aligning any three points on the upper part or any surface on the upper part of the shape data of the pre-formed bracket with the coordinate system on the processing jig, and moving the orientation of the patient's tooth surface data in a direction suitable for post-processing. The shape data of the base portion of the aforementioned pre-shaped bracket and the patient's tooth surface data are logically calculated, A process of calculating NC data for processing a 3D shape corresponding to the patient's unique tooth surface shape, or NC data for processing a curved surface shape resulting from the intersection of the patient's tooth surface data and the shape data of the pre-made bracket. The method according to claim 1, characterized by including the following: [Claim 3] The method according to claim 1, characterized in that the base portion of the pre-shaped bracket in step a is given an uneven surface, and the uneven surface remains after processing in step e. [Claim 4] The method according to claim 1, characterized in that, in step a, a plurality of the pre-formed brackets are arranged at appropriate intervals and a shape is manufactured by connecting adjacent pre-formed brackets with runners. [Claim 5] The method according to claim 1, characterized in that, in step e, data for a single pre-formed bracket or data for a shape in which multiple pre-formed brackets are connected by a runner is further provided with jig shape data that serves as a positioning guide for attaching to the correct position on the patient's tooth surface, and a shape in which the bracket shape and positioning guide defined by this data are integrated, or a shape in which the bracket shape, positioning shape and runner shape are integrated.

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