Modular system for customized orthodontic appliances

Description of the invention

The present invention relates to a method of designing and manufacturing an individually fitted orthodontic bracket for a patient using a computer. The invention is useful generally in orthodontics. It can be used particularly advantageously in lingual orthodontics, i.e. where the orthodontic appliance is attached to the lingual surface of the teeth for aesthetic reasons.

A widely used method of straightening or aligning a patient's teeth is to secure brackets to the teeth and guide flexible rectangular wires through the bracket slots. Typically, the locks are a finished product. In most cases, brackets are designed for a particular tooth (e.g., the upper canine) but not for a particular patient's tooth. The bracket adapts to a particular tooth by filling the gap between the tooth surface and the bracket surface with glue to fix the bracket to the tooth in such a way that the bracket gap is in the horizontal plane when the teeth are in their final position, see U.S. Patent No. 4,243,386 (Kawaguchi). The orthodontic appliance disclosed by Kawaguchi includes a bracket that attaches to the base member. The tooth surface of the base element only generally corresponds to the shape of the labial surface of an average person's tooth. An adhesive is used to bridge any gap between the base member and the tooth surface. The base member has recesses in the form of blind holes to facilitate connection with the adhesive used to bond the base member to the tooth surface and to limit excess adhesive on the side and front of the apparatus.

The brackets position themselves on the teeth so that when the teeth move to their target position, the bracket slot lies in the horizontal plane. The arc provides the force to move the tooth to the desired target position. For lingual brackets, Thomas Creekmore developed a system with vertical zipper slots to facilitate wire insertion so that the wider side of the wire is vertical. Unitek has registered this locking system under the trade name CONSEAL ™.

US Patent Application No. US 2002/0010568 A1 describes a computer in which a three-dimensional virtual tooth model corresponding to the patient's dentition can be used to simulate tooth displacement and then display a virtual bracket on the virtual dentition. Adaptation of the bracket bases to individual needs is made by applying glue to the lock and milling a hardened drop of glue to fit the tooth surface. In addition, the bracket base is extruded to the desired shape, or the extruded base plate is milled to function as a positioning element for the tooth.

The international patent publication WO 01/80761 A2 describes the generation of a virtual model of the patient's dentition in a computer, the application of virtual brackets to the computer model and the determination of tooth displacement during orthodontic treatment. In order to optimize the displacement of the teeth into the desired position, an arch is provided which is adapted to exert a suitable force on the teeth by interacting with the slots of the brackets attached to the teeth. The individual locks are prefabricated.

U.S. Patent No. 5,454,717 discloses a computer aided manufacturing system for braces in accordance with data collected directly from the patient's teeth. In order to adapt to individual needs, a bracket semi-finished product is provided with a mounting surface intended for connection to the surface of the patient's tooth crown and an arch support extending from the mounting surface, whereby an arch slot is cut in the arch support under the control of a computer that stores the data. binding the mounting surface of each of the plurality of lock blanks when mounted on the bracket. In order to adjust the force applied to the individual teeth, a slit of an individual shape is cut in each lock having regard to the mounting surface of each lock, and accordingly, an arch fitted to the lock slots will exert the desired force on the locks.

U.S. Patent No. 5,533,895 relates to a method of prefabricating orthodontic appliances for different racial groups according to positions and inclinations common to members of the racial group by providing the appropriate dimensions and fit of the brackets to obtain the desired dentition.

US Patent No. 4,243,386 discloses an orthodontic bracket having a base with a roughness of 6 to 10 µm intended to receive a bonding cement.

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European patent application No. EP 1080697 deals with the problem of positioning malocclusion teeth to the desired end position using a lingual straight wire, with substantially no bends in the vertical or horizontal part, in combination with brackets attached to the teeth and to the wire.

The use of computers in orthodontics based on the design and manufacture of brackets individually fitted to a specific patient and the design and manufacture of a positioner for the installation of individually fitted brackets and arch has already been proposed. See U.S. Patent No. RE 35,169 (Lemchen et al.) And U.S. Patent Nos. 5,447,432, 5,431,562, and 5,454,717 (Andreiko et al.). The system and method of Andreiko et al. is based on a mathematical calculation of the target tooth position and the desired ideal dental arch. The method of Andreiko et al. it has not been widely used and has in fact had little effect in treating orthodontic clinic patients since it was first proposed in the early 1990s. This is due to many reasons, one of which is that proposed by Andreiko et al. a deterministic approach to calculating target tooth positions does not take into account unforeseen events during the course of treatment. Moreover, the methods proposed by Andreiko et al. they essentially eliminate the orthodontist from the treatment planning phase and attempt to replace the knowledge and qualifications of the orthodontist in the target tooth positioning phase with empirical calculations of tooth target positions.

Typically, the wires currently used in orthodontic treatment are finished, commercially available products. If individual fitting of the wires by the orthodontist is desired, the aim is to do so with the minimum possible modification. For this reason, brackets are designed so that, after treatment is complete, when the teeth are aligned, the bracket slots are positioned and oriented horizontally, which means that the wire lying passively in the gaps without any force being applied will lie flat. This method of treatment is known as the straight wire technique and is the dominant technique in orthodontics around the world. This technique is effective for both manufacturers and orthodontists. Individually fitted orthodontic appliances proposed by Andreiko et al. require the use of a flat wire, but with an individually tailored bend in the horizontal plane dictated by the shape of the desired ideal dental arch of the patient.

The so-called straight arch technique, still used in orthodontics, has some significant disadvantages from the point of view of patient comfort. The necessity to fill the gap between the bonding surface of the bracket and the tooth surface with glue always leads to a greater total thickness of the appliance, which is permissible for brackets glued from the labia-buccal side, because the labial surfaces of the teeth are very even in different patients and the gap to be filled is not significant. However, the lingual (lingual) surfaces of the teeth vary considerably from patient to patient. Thus, in order to achieve the goal of orienting the bracket so that the bracket gap is parallel to all other gaps after treatment, the thickness of the necessary adhesive layer is often 1-2 mm. It is clear that every fraction of a millimeter added to the thickness of the apparatus significantly increases the patient's discomfort. Especially in the case of lingual brackets (brackets glued to the lingual surfaces of the teeth), problems with articulation arise and the tongue is severely irritated for several weeks after sticking. The surfaces of the teeth near the glued bases of the brackets are difficult to clean, which causes bacteria to accumulate in these places, which is the cause of gingivitis. The farther the arc is from the tooth surface, the more difficult it is to obtain the exact final position of the individual teeth. A torch error (rotation around the axis of the wire) of as little as 10 ° can result in a vertical misalignment of the tooth of more than 1 mm.

Another significant disadvantage of thick brackets, especially in the case of brackets attached on the side of the tongue, is noticeable when the front teeth are crowded (which is a common cause of orthodontic treatment). As the lingual surface of the teeth is more limited due to the curvature of the jaw, not all brackets can be glued in one session. Rather, the orthodontist must wait until all the brackets are attached until the teeth are less crowded. The crowding of the teeth also causes problems for brackets placed on the labial surfaces of the teeth. Geometric considerations make the problem of limited area more serious as the combined thickness of the lock / lock base / adhesive layer increases.

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Another problem in orthodontics is determining the correct position of the bracket. At the time of sticking the bracket, the tooth can be positioned remotely from the desired position. Therefore, the task of placing the brackets in such a way that the belt arch moves the teeth to the correct position requires a lot of experience and spatial imagination. As a result, a lot of time is lost towards the end of the treatment for the necessary correction of the bracket position or the shape of the wire. This problem can be solved by creating an ideal treatment target, either virtually with three-dimensional dentition scan data, or in fact by dividing the dentition model into single-tooth models and embedding the tooth models in the wax base at an ideal position. Then, with this ideal tooth alignment, the brackets can be placed on the teeth in the optimal positions, such that a flat wire inserted into the bracket slots will move the teeth exactly to the ideal target position. This operation can also be performed virtually - on a computer or in real life. Then, the position of the bracket should be separately transferred for each tooth to the incorrect (original) bite. On the basis of this malocclusion situation, a bracket can be made for the transfer of brackets, which allows the brackets to be glued exactly in the place defined by the purpose of treatment. This technique is disclosed generally by Cohen in US Patent No. 3,738,005.

Published PCT patent application filed by OraMetrix Inc., WIPO International Patent Publication No. WO 01/80761 and U.S. Publication No. 2002/0010568 (Rubbert et al.) Discloses orthodontic wire treatment using general braces applications and individually tailored bends. The arc can have complex twists and bends and as such is not necessarily a flat wire running in a plane. The entire content of WO 01/80761 is hereby incorporated by reference into the present specification. This document also describes a scanning system for creating virtual three-dimensional models of dentition and an interactive computerized treatment planning system based on scanned dentition models. As part of the treatment planning, virtual brackets are positioned on the virtual teeth and the teeth moved to the desired position by the operator performing the clinical evaluation. A virtual three-dimensional model of the dentition with brackets in conditions of malocclusion is sent to a rapid prototyping device, where the actual model of the dentition with brackets is produced. A rail for carrying the brackets is then formed on the model. The actual brackets are placed in the rail in the places where the virtual brackets were, followed by the indirect gluing of the brackets to the teeth with the splint. This method, described in the international patent publication WO 01/80761, overcomes a number of problems inherent in the method of Andreiko et al.

The brackets may come off during treatment if, for example, the patient burns hard pieces of food. It is obvious that in this case the bracket carrying the brackets used to pre-bond the brackets will no longer fit as the tooth has already moved. While it is possible to replace the buckle by cutting the rail (as described in International Publication No. WO 01/80761) into parts and using only one part corresponding to the buckle that has fallen off, the reliability of this method is limited as a small piece of flexible material will not provide secure position of the lock. Accordingly, it may be necessary to make a new bracket transfer rail adapted to the actual position of the tooth in a costly laboratory process.

The methods and device described herein are improvements in lingual appliance therapy, but are also advantageous in labial appliance therapy.

A method of designing and manufacturing an individually tailored orthodontic bracket for a patient according to the invention by means of a computer, the bracket having wings having an arch slot and a base having a tooth-adjacent surface representing the three-dimensional surface of a patient's tooth in which a digital representation is recorded. parts of the patient's dentition on the computer, and providing a library of three-dimensional bracket wings on the computer; a tooth area is designated where the bracket base is attached to the tooth; the three-dimensional shape of the surface adjacent to the tooth of the bracket base is determined directly from the digital representation of the patient's dentition, the three-dimensional shape mapping the three-dimensional surface of the tooth, characterized in that a second surface of the bracket base is obtained, the second surface facing the surface adjacent to the bracket. tooth and has a three-dimensional shape corresponding to the surface adjacent to the tooth; obtaining virtual lock wings from this library and positioning the virtual lock wings with respect to the virtual lock base; connecting the virtual lock wings to the virtual lock base to form one unitary virtual three-dimensional object representing the lock; and exporting digital data representing the lock from the computer to the manufacturing system for manufacturing the lock.

Preferably, furthermore, the normal vector of each tooth adjacent surface element at the bracket base is created and each surface element is moved away from the tooth in the direction of the normal vector using a predefined offset value corresponding to the thickness of the bracket base.

Preferably, the surface element is a triangle.

Preferably, a lock base is used having a narrow rim and a thick central portion near which the lock wings are attached to the lock base.

Preferably, the virtual model of the lock wings is further modified.

Preferably, an accessory is added to these lock wings.

Preferably, the accessory is hooks.

Preferably, when connecting the virtual lock wings to the virtual lock base, a computer visual inspection of the plurality of virtual teeth and virtual lock bases attached to the teeth is performed and the position of the lock wings relative to their respective lock base is changed.

Preferably, furthermore, a portion of the virtual lock wings are removed, this portion including a portion that would protrude into the tooth when the lock wings are connected to the lock base.

Preferably, a manufacturing system is used which comprises a rapid prototype system producing a representation of the lock used as a positive mold, the lock being cast during manufacture.

Preferably, the lock is produced by laser sintering in the manufacturing step.

Preferably, the digital representation of the dentition is further modified using a computer to the desired target position, wherein the steps of obtaining virtual lock wings from the library and positioning the virtual lock wings with respect to the virtual lock base and connecting the virtual lock wings to the virtual lock base to form one unitary virtual three dimensional object representing the lock are performed after the teeth have virtually moved to the desired target position.

Preferably, furthermore, an actual model of the patient's teeth is made, the actual model is manipulated until the teeth are in the desired occlusion, the actual tooth model is scanned at the desired occlusion, and a digital representation is used including a three-dimensional representation derived from this scan.

Preferably, the tooth engaging surface and the second surface have a three-dimensional configuration corresponding substantially exactly to the corresponding three-dimensional tooth surface.

Preferably, information on the spatial position of the bracket and the slot of the bracket is transmitted to a wire bending robot to bend an individually tailored orthodontic arch for a given patient.

Preferably, the lock base includes an element forming a slot into which an arc is inserted, the slot being oriented approximately parallel to the lock base at the point where the element engages with the lock base.

Preferably, the lock further comprises a U-shaped insert in the slot of the lock.

Related to this method is a set of (one or more) brackets having a slot oriented with respect to the bracket base such that the orthodontic wire extends substantially parallel to the tooth surface, i.e. to that portion of the tooth surface adjacent to where the wire passes. by the lock as further explained in detail and as shown in the figure.

The brackets consist of a base for sticking the bracket to the tooth and wings with a slot into which a flat-sided ribbon arc is inserted (e.g. it will be a side of a rectangular, square, parallelogram or wedge-shaped wire) or, alternatively, a wire with a flat side. oval cross-section. The slots of the brackets are oriented approximately parallel to the respective brackets of the brackets such that when the bracket or set of brackets is placed on the patient's tooth or teeth and the arch is inserted into the slot, the arch will be bent or inclined obliquely with respect to the occlusal plane (analogous to the slope of the racetrack) on the bend). In the form where the arc has flat surfaces (arc with a rectangular, parallelogram, square, wedge, etc. cross-section) the flat side of the arc runs substantially parallel to the tooth surface at the point where the wire is inserted into the

The slits at an inclination with respect to the occlusal plane. In an embodiment where the arch has an oval cross-section, the major axis of the wire cross-section is oriented substantially parallel to the tooth surface and is inclined with respect to the occlusal plane.

In the case of front teeth, it is desirable to achieve a uniform wire inclination to avoid abrupt changes in the inclination (i.e., torque changes) of the wire passed through the successive slots to achieve smooth wire orientation changes. In rectangular or square cross-section wires, one pair of parallel opposite sides of the arch is oriented substantially parallel to the tooth surface. Usually it is a pair of parallel sides of greater width or height. This makes it possible to significantly reduce the overall thickness of the locks compared to the known art, since it does not require the build-up of an adhesive layer in order to achieve a horizontal alignment of the joint after gluing the lock, which is the case with the straight arc technique. The shape of the brackets and arch are particularly suitable for use in lingual braces.

This reduction in thickness of the bracket, bracket base and wire offers several significant advantages over the systems of the known art and satisfies the long felt need in the art for a more satisfactory lingual orthodontic system. These benefits include less articulation problems, a significant reduction in tongue irritation, a reduction in the risk of losing the bracket, greater control of target positioning, thanks to a shorter distance between the tooth and wire to increase the accuracy of tooth movement to the desired target position, increased patient comfort and better hygiene conditions.

One of the reasons why the basic shape of orthodontic wires is the shape in which the wire is shaped like a band is the ease of industrial manufacture. In order to reduce the thickness of the bracket, it is much more advantageous to run the wire parallel to the surfaces of the individual teeth. In most patients, the lingual surfaces of the anterior teeth are markedly sloped about the vertical axis. The wire that runs parallel from tooth to tooth is "slanted obliquely to take advantage of the parallelism of the slots of the bracket." Such a wire could not be produced using standard mass production techniques due to the very individual anatomy of each patient's teeth. Shaping the wire by hand to give it a bent shape is extremely difficult. Modern arch materials, such as shape memory feet, make this task even more difficult or even impossible to do by hand. However, in a preferred embodiment, the required wire geometry can be obtained in electronic format. The wire geometry may be determined by the spatial location of the bracket slots and / or the orientation of the brackets on the teeth in the desired clamp. The electronic format can be exported to modern, recently built, wire bending robots capable of bending wire and giving it any shape (including oblique). For example, digital data defining the wire geometry can be exported to wire bending devices, such as the 6-axis robot described in WO 01/80761, and cause the robot to bend and twist the wires at an oblique slope to the configuration described in this description. . Thanks to this, it is now possible to mass-produce profiled-shaped wires. A presently preferred wire bending robot is also described in a United States patent application filed on April 13, 2001.

It is possible to use an inclined curve. The wire may be of any cross-section giving at least one plane of the wire a flat, such as rectangular, or alternatively the wire may have an oval cross-section. The arc during manufacture is bent in such a way that, when made at rest, it has a shape such that the flat surface of the wire (or the major axis of the cross section of the oval wire) is bent with respect to the occlusal plane over a substantially arcuate segment. The bend of an arc occurs on those sections to be inserted into the brackets and serves to straighten two or more teeth. In an embodiment where the wire cross-section is rectangular or square, one side of the first or second pair of parallel sides of the wire extends substantially parallel to the tooth surface adjacent to the locations where the wire is to pass through the brackets of the two or more teeth.

A method of designing and manufacturing an individually fitted orthodontic bracket includes fabricating an arch. The method includes the step of defining the position of the set of latch slots in the set of brackets in a three-dimensional space by means of a computer. The bracket slots are oriented substantially parallel to the tooth surface at the locations where the brackets are to be glued to the teeth. A further step of the method is the step of providing the wire bending robot with information determining the position of a given set of slots of locks. Typically, such information is in the form of

A digital file representing the coordinates of the lock slots in three-dimensional space. Based on this information, the robot's control program can instruct the robot on how to bend the wire so that, under rest conditions, after making the wire, it has the shape defined by the slots of the locks. Accordingly, the next step in the method is the step of bending the arch by a wire bending robot and shaping it to correspond to the position of the slots of the brackets, wherein the arch is bent such that the arch is oriented substantially parallel to the tooth surfaces over a substantially arcuate segment. The wire may be bent continuously or, alternatively, it may form a series of bends intersected by straight sections corresponding to the slots of the locks as described in more detail in WO 01/80761 and in US Patent Application No. 09/834967.

Furthermore, the lock may have an improved base that makes the lock essentially self-aligning, i.e. the lock may be placed in a particular location and positioned on the tooth in the correct position using shape matching without the use of a positioner or other lock setting device, such as the splint disclosed by Cohen. in U.S. Patent No. 3,738,005, or the positioner from Andreiko et al. In particular, an improvement is made to a bracket having a base in which the bracket base has a tooth engaging surface with a spatial configuration corresponding substantially exactly to the spatial configuration of that tooth surface on which the bracket base abuts the tooth.

In one possible form, the spatial size of the base area adjacent to the lock is sufficiently large and much larger than that of the lock bases proposed in the prior art, so that the lock can easily be manually adjusted to a given position, which is the correct position of the lock on a given lock. tooth, due to the fact that the shape of the large area of ​​the bracket base corresponds to the shape of the tooth surface. The bracket can then be glued to the tooth in the right place without the use of bracket alignment tools such as a positioner. In a further possible embodiment, the bracket bonding surface comprises a bump or bump portion to allow the bracket to be positioned on the tooth at a particular particular location.

In addition, the lock may have a base that encloses a thin shell with the aim of reducing the overall thickness of the lock as much as possible. The base comprises a base surface on the tooth side of a shape corresponding to that of the tooth. In this embodiment, the opposite side of the tooth base has a shape that corresponds to the tooth-side base surface, the spatial configuration of which also corresponds to the spatial configuration of the tooth surface. A preferred way to create a thin bracket base on the computer is to draw a normal vector to each element of the tooth side of the bracket base surface (e.g. being a triangle, depending on how the surface is represented on the computer). Then, each surface element is "lifted above the tooth surface in a direction defined by the normal vector direction for a predetermined distance corresponding to the desired thickness of the bracket base. In this way, a thin shell is formed, the outer side of which has substantially the same surface and spatial configuration as the surface of the bracket base on the side adjacent to the tooth. Other methods can also be used. For example, the lock base may be thinner at the periphery (e.g. 0.1mm) and have a thicker central portion (e.g. 0.3mm) at the point where the lock leafs connect to the base. Suitable software may be used to vary the thickness over the lock base surface, such as programs that scale the normal vector with a variable depending on the distance of the normal vector from the edge of the lock base.

Thus, a method is provided to design and manufacture an individually fitted orthodontic bracket for a specific patient by means of a computer. The lock has a lock base. Three-dimensional models of the patient's teeth are saved in the computer's memory. The method includes the step of defining a tooth surface on which the bracket base is to be adhered to the tooth; defining the spatial shape of the bracket base surface to be adjacent to the tooth, conforming to the spatial shape of the tooth surface in question, and obtaining the spatial shape of the other side of the bracket base opposite the tooth adjacent surface. The virtual three-dimensional lock wing library is stored on the computer or is otherwise accessed by the computer. The next step in the method is to take the lock wings from the library and combine it with the lock base to form one virtual three-dimensional object representing the lock.

The shape of the second opposite side of the base, corresponding to the shape of the surface of the respective bracket base adjacent to the tooth, is obtained, for example, by using the previously described

The method of "lifting. The method may also include the optional step of modifying the virtual model of the lock lobes. For example, a portion of the lock wings may be removed to position the slot in the lock wings as close as possible to the lock base and eliminate that portion of the wings that would otherwise protrude into the tooth. As another example, the modification may include the addition of additional features such as hooks to the wings.

The computerized joining of the bracket wings to the bracket base may be performed simultaneously for a group of teeth in order to take into account the proximity of adjacent teeth and brackets. Therefore, the method may include the step of viewing a plurality of virtual teeth and virtual bracket bases attached to the teeth with a computer and repositioning the bracket wings relative to a given bracket base. The latter step will be performed, for example, to better position the wings on the base or to avoid collision of the wings with an adjacent or opposing tooth, for example during chewing or during tooth displacement.

The method of designing and manufacturing an individually fitted bracket includes the step of storing a digital representation of the corresponding portion of the patient's dentition on a computer. It may be a digital representation of the entire dentition or, alternatively, only those tooth surfaces to which the brackets are to be glued. The method's further steps are to provide access to a library of virtual three-dimensional bracket wings by, for example, saving the library to a computer and determining the shape and configuration of the bracket bases, in which the shape of the surfaces adjacent to the tooth corresponds substantially exactly to the spatial configuration of the respective tooth surfaces. The next step in the method is to combine the bracket wings taken from the wing library with the appropriate bases and thus create a set of individually fitted orthodontic brackets. From the computer, a file representing the individually fitted brackets is exported to the manufacturing system to produce individually fitted orthodontic brackets. The next step in the method is the step of manufacturing individually fitted orthodontic brackets using any of a number of known techniques, for example milling or one of the techniques detailed in this specification, such as casting.

There are other improvements to the fabrication of custom-fit brackets. A method of manufacturing an orthodontic bracket having wings with a slit and base comprises the step of defining the three-dimensional shape of the bracket and manufacturing the bracket from materials of at least two different hardnesses, one material or materials being / are relatively hard material (s) and serving to make the wings, and the second material or materials is / are relatively soft material (s) and serves to make the base. The strength of the zip materials is always a compromise. While the part in which the slit is formed should be as hard as possible to maintain a constant cross section of the slit, even under high mechanical stresses acting on the lock (e.g. when biting hard objects), the base part should be softer to facilitate removal. after the end of treatment. The base, if sufficiently soft, can literally be lifted from the tooth surface with an appropriate tool. Depending on the manufacturing technique, a variety of alloys can be used to achieve the above-described material configuration. Using the centrifugal casting technique, it is possible to first make a fracture-forming part from a defined controlled amount of hard alloy, and then fill the rest of the joint with a softer alloy (or the operations can be performed in reverse order). It is possible to control the amount of material needed to make a specific bracket part because the volume of each bracket element can be accurately determined from the three-dimensional model of the bracket. Other manufacturing techniques, such as laser sandwich sintering, may also be used, where the different layers may be made of powders of different alloys.

It is possible to use computer-aided modular design of individually tailored brackets designed for a specific patient. Libraries of virtual lock wings, virtual lock bases and possibly additional virtual elements such as hooks are stored on the computer. The user specifies or selects a bracket base and wings for a given tooth, then both of these virtual objects are combined to form a virtual bracket. Graphical software tools can be made available to the user to define how and where the base and the bolts of the lock are to be connected. The data representing the virtual lock can be exported to the rapid prototyping system, where the lock will be manufactured directly or a mold or model of the lock will be produced and then used

In the lock casting process. In one possible form, the configuration of the base surface of the bracket corresponds substantially exactly to the shape of the tooth surface.

The subject of the invention is illustrated in the exemplary embodiments in the drawing, in which fig. 1 shows a perspective view of an oblique inclined orthodontic arch, fig. 2 - partially sectioned, a group of teeth, brackets on these teeth and the arch of fig. 1, fig. 2A - oval. section of the arch, fig. 2B section of the arch from fig. 2A placed in the slot of the bracket oriented essentially parallel to the tooth surface and shows the major axis of the section of the arch at an angle to the occlusal plane, Fig. 3A - section of a tooth with the base of the bracket and the slot oriented essentially parallel to the tooth surface, Fig. 3B - section of the same tooth which is shown in Fig. 3A, but using a standard Ormco lingual bracket of the prior art in which the breach of the buckle corresponds to a belt arc lying in a horizontal plane that is not obliquely sloped as shown in Fig. 3A, Fig. 4 - perspective view of a computer model of two teeth with a bracket base perfectly fitted to the tooth surface and covering a large area of ​​the tooth, which is intended to allow the orthodontist to manually place the bracket in the correct position on the tooth without using a positioner or other bracket insertion tool, fig. 5 - view of additional elements in the occlusal plane that can be placed on the bracket base and glued to the tooth to prevent full closure of the maxilla and mandible, fig. 6A, 6B and 6C - standard shapes of the bracket wings that can be used to design individually fitted brackets orthodontic. These and other types of bracket wings are stored in the computer memory as a library of virtual bracket objects and used to design individually fitted orthodontic brackets as will be described in detail hereinafter, Fig. 7 - a top view of three lower anterior teeth showing, somewhat simplified, in how the position of the wings on the bracket base can be adjusted to account for crowding of the teeth. The adaptation shown in Fig. 7 it is simulated on a computer in which the bracket design program is installed and which allows the user to position the wings on the bracket base in any chosen position in order to optimize the position of the bracket wings in the dentition of a given patient. In the case of labial brackets, the ability to move the flaps away from the center of the base can be an advantage, for example, it is possible to move the flaps on the lower second premolar towards the gingiva similar to an Ormco Mini Diamond bracket^TM with gingival displacement. This solution provides a larger bonding surface without moving the gap too far towards the occlusal part of the tooth, fig. 8 Ormco Spirit ceramic bracket^TM MB with an insert in the bracket slot, - Fig. 9A shows a virtual tooth shown on a computer workstation screen, on which a bracket design software is installed, by which the user delimits the base of the bracket on the tooth surface by marking appropriate points on the tooth surface. Fig. 9B shows a curve defining the edge of the lock base, formed by joining the points marked in Fig. 9A with lines corresponding to the contour of the tooth surface, Fig. 10 - a group of virtual teeth shown on a computer workstation screen on which a bracket design software is installed, showing the user defined bracket bases boundaries for a given tooth group. It should be noted that the tooth surfaces covered by the base may include a significant area of ​​the lingual surfaces of the teeth, in this case about 60-75 percent of the tooth lingual surface, to assist the user in placing the bracket on the tooth in the correct position. The area of ​​the tooth coverage of the bracket base depends on the configuration of the tooth surface, and a relatively flat tooth surface requires a larger bracket surface area for the bracket to be properly positioned without the aid of a positioner. Where the bracket base covers part of the tooth cusp, the area of ​​coverage may be smaller, Fig. 11 - tooth surfaces to be covered by bracket bases. These surfaces are "cut or separated from the tooth models by performing a separation operation on a computer and shown as independent three-dimensional surfaces of the zero-thickness objects, Fig. 12 a tooth group view, partially sectioned, showing the bracket base covering the surface of the tooth and bracket wings. placed on the base, in an intermediate stage of the design of an individually fitted lock. The portion of the bracket projecting inwardly of the tooth will be finally removed as shown in Fig. 21, Figs. 13A and 13B - a perspective view of two representative bracket wings whose surfaces are shaped according to the surfaces of the teeth and wherein the slots are oriented substantially parallel to the tooth surface adjacent to it. the place where these wings are glued to the tooth, Fig. 14 - perspective view

With a digital representation of a group of teeth and bracket objects, Fig. 15A - prior art lingual bracket arrangement, Fig. 15B - same teeth but with individually matched brackets for bracket design. Comparing Figs. 15A and 15B, a significant reduction in the thickness of the buckle shown in Figs. 15B, Figs. 16 - combination of virtual bracket wings and a virtual bracket base at an intermediate stage of designing an individually fitted orthodontic bracket, in which the bracket base and bracket wings constitute two independent virtual three-dimensional objects that can be moved relative to each other, fig. 17 - an image on the screen of a computer workstation, on which software enabling the design of the lock is installed, by means of which the user combines the base and the lock wings shown in fig. 16 into one virtual object, fig. 18A and 18B - two views of the lock base and the lock wings combined into one virtual object, Fig. 19 - the base and wings of the bracket of Figs. 18A and 18B placed on a virtual tooth, Fig. twenty - the image on the screen of the computer workstation performing the operation of subtracting the object representing the tooth shown on the screen in red from the object representing the base / wings of the lock shown on the screen in green. This step is to remove that part of the bracket wings which would otherwise go inside the tooth, fig. 21A and 21B - two perspective views of the object showing the base / wings of the bracket after the subtraction shown in Fig. 20. Comparing Fig. 17 and Fig. 21B, it can be seen that that part of the bracket wings that would otherwise enter the tooth has been removed from an object representing the base / bolt of the lock.

The bracket gap is parallel to the tooth surface and the orthodontic arch is obliquely inclined

As mentioned previously, in the straight arch technique currently used in orthodontics, the basic shape of the arches according to the prior art is a tape arch. When the teeth are moved to the desired clamp, all the slots of the brackets lie in one plane. Therefore, the rectangular belt arc itself has a planar configuration. This is the case with the bows used with the previously mentioned CONSEAL ™ brackets. With the wire cross section oriented vertically (wider side of the wire vertical), the arc still forms a plane substantially parallel to the occlusal plane and this wire cross section orientation is maintained throughout the arc. The main reason for the use of such a solution is the ease of manufacturing on an industrial scale straight band curves arranged in one plane. A significant departure from straight belt curves is proposed.

In particular, it has been realized that in order to reduce the thickness of an orthodontic bracket, it is much more advantageous to structure the gap and the arch such that the arch will run substantially parallel to the surfaces of the individual teeth. In one embodiment, the slots of the orthodontic bracket are oriented such that the wire extends substantially parallel to the surface of each tooth. By this it is to be understood that when a wire with at least one side having a flat surface is inserted into the slots of the brackets, the flat side of the arch is inclined obliquely or tilted at an angle to the occlusal plane. For example, in the case of a rectangular or square wire, one pair of sides of the wire is oriented parallel to the tooth surface and is oblique to the occlusal plane. Similarly, when the wire has an oval cross-section, the longer axis of the wire cross-section (see Fig. 2B) is oriented substantially parallel to the tooth surface and is inclined at an angle with respect to the occlusal plane.

The lingual surfaces of the anterior teeth are markedly sloped. The wire running parallel from tooth to tooth, especially in the front tooth section, will have to be "obliquely inclined (analogous to the slope of a bend racetrack) with respect to the occlusal plane. Due to the individual anatomy of each patient's teeth, such wire could not be manufactured using standard mass production techniques. At the same time, it is very difficult to shape the wire by hand. The use of preferred materials such as shape memory alloys make this task even more difficult or even impossible to be performed by hand. The desired wire geometry may be available in electronic format. It is possible to transfer a data file defining the geometry of a given wire to a manufacturing device, such as the 6-axis wire bending robot described in WO 01/80761, in order to bend and twist the wire to obtain such a shape.

Fig. 1 shows a perspective view of an arc 10 with flat "obliquely sloped" sides. The arc as shown in the drawing has a rectangular cross-section and has two pairs of parallel sides. One of the pairs of parallel sides 12 is wider (in a direction perpendicular to the axis of the wire) than the other, at least in the case of non-square cross-section wires, and in this embodiment the pair of wider

The sides 12 are oriented substantially parallel to the tooth surfaces. This can be better seen in Fig. 2 showing an arch fitted in three brackets 14 on three of the front teeth 16. The brackets 14 consist of a bracket base 18 and bracket wings 20 including a slot 22 into which the arch is inserted. The bracket slots 14 are oriented approximately parallel to the respective bracket bases 18 and to the respective tooth surfaces. The slots 22 of the brackets are positioned such that when the brackets 14 are placed on the teeth 16 of a patient and the arch 10 is inserted into the slots 22, the arch 10 is inclined obliquely or tilted with respect to the occlusal plane. One of the pairs of opposing parallel sides of the arch (12 in Figures 1 and 2) is oriented substantially parallel to the tooth surface. This solution makes it possible to significantly reduce the overall thickness of the bracket compared to the prior art, which makes brackets and arches of this structure particularly suitable for use in lingual orthodontic appliances. The overall thickness of the bracket is also reduced by the use of the bracket base in which the configuration of the tooth surface and the counter surface corresponds to the three-dimensional configuration of the tooth surface. As a result, the base can be built as a thin coating (e.g. 0.3 mm thick) adapted to the anatomy of the tooth.

It should be noted that in Fig. 1, the oblique arc 10 is shown in "as-built" form. In other words, the wire has the shape shown in Fig. 1 when the teeth have been correctly positioned and the tooth is no longer subjected to corrective forces. When the arc shown in Fig. 1 is applied to the teeth in an abnormal bite, the wire will have a different shape due to a malocclusion, but since the brackets are glued to the teeth and the bracket slots 22 are oriented substantially parallel to the tooth surface, the arch 10 will also be oriented such that the sides 12 of the arch 10 will be parallel to the tooth surface, which has a number of advantages from a clinical point of view.

Fig. 2A shows an oval section of the arch 10. The section of the arch is oval with a major axis 11 and a minor axis 13. As shown in Fig. 2B, the slot 22 of the bracket is oriented substantially parallel to the tooth surface and the arch 10 is positioned in the slot of the bracket. such that major axis 11 is inclined obliquely or bent with respect to the occlusal plane 15.

Figures 3A and 3B illustrate the advantages of the lock structure and the obliquely inclined wire: they allow the overall thickness of the lock 14 to be significantly reduced. Figure 3A shows the structure of the lock 14 in which the slot 22 is oriented parallel to the tooth surface 16A. Fig. 3B shows a prior art bracket in which slot 22 is at a significant angle with respect to tooth face 16A. Bracket slot 22 is parallel to the occlusal plane. In the case of anterior teeth, this causes the bracket slot 22 to slope against the lingual tooth surface 16A at an angle of approximately 45 degrees. It should be noted here that the orientation of the slit 22 herein means the direction from the opening of the slit 22A to the bottom of the slit 22B, not a transverse direction parallel to the axis of the arc. Therefore, the slit shown in Fig. 3A is oriented parallel to the surface of the tooth 16A in Fig. 3A. All the brackets shown in Fig. 2 have the same orientation. In contrast, the slit in Fig. 3B is oriented approximately 45 degrees with respect to the tooth surface 16A. The slot 22 of the prior art arrangement shown in Fig. 3B is such that the flat surface of the in-plane wire is perpendicular to the occlusal plane and is not inclined at an angle as in the case of Figs. 3A and 2B.

The bracket base 18 shown in Figures 2 and 3A corresponds exactly to the shape of the tooth surface and consists of a thin coating. These aspects of the lock construction are detailed below.

The reduction in thickness allowed by the bracket design shown in Figures 2, 2B and 3A offers a number of significant advantages over the prior art bracket design shown in Figure 3B, particularly in lingual orthodontic appliances:

less problems with articulation, less irritation of the tongue, less risk of losing the buckle (the flatter the lock, the shorter the torque arm is when the patient taps the lock, and the less stress on the glued joint), better control of guiding to the correct position (the smaller is the distance between the arch and the tooth, the better the tooth "follows the arch", greater patient comfort, better hygiene conditions.

The orientation of the arch 10 on the molars may be vertical, as shown in Figure 1, thereby achieving a minimum overall thickness of the brackets on the molars, or alternatively, the orientation of the arch may be horizontal. The horizontal orientation of the arc increases the thickness of the lock (in the case of

For a typical 17x25 cross-section, this would be, for example, 0.635 mm (0.025 inch) per side instead of 0.4218 mm (0.017), but this enlargement is so slight that it would no doubt be acceptable if the performance or clinical considerations were would require such an orientation. Since the horizontal orientation of the slots is acceptable for molars and premolars, it would also be reasonable to mix known brackets with brackets described herein. For example, the brackets on molars and premolars may be known brackets, and the set of brackets described may be used on the front teeth and canines.

Therefore, a bracket and bracket set 14 with slots 22 have been described in which the slots 22 of each bracket 14 are oriented approximately parallel to the bases 18 of their brackets such that the bracket set is fitted over the patient's teeth 16 and the arch 10 is inserted into the slots. the arch 10 is sloped obliquely with respect to the occlusal plane to conform to the tooth surface at the point where the arch 10 enters the slot 22 so that the overall thickness of the bracket can be reduced.

As shown in Figures 2 and 3, the pair of sides 12 of the arch 10 are oriented substantially parallel to the lock base 18 in the region where the arc 10 enters the slots 22. As shown in Figures 2 and 3A, each lock base preferably has a lock base. the tooth surface 24 with a shape that corresponds exactly to the spatial configuration of the surface of a given tooth.

The invention is applicable to both labial and lingual brackets. The brackets in one of the possible forms are essentially self-aligning in the sense that they can be placed on the tooth in the correct position without the aid of a positioner or splint. In the form shown in Fig. 2, brackets 14 are lingual brackets and the base of each bracket covers a large portion of the tooth's lingual surface so that it is possible to manually position the brackets on the teeth in the correct tooth-specific position. Fig. 3A also shows a second, opposite surface 26 of the lock base, shaped to match the shape of the tooth surface 26 of the lock base to further reduce the thickness of the lock.

In one possible embodiment, the bracket set may include all brackets that treat the patient's dental arch. The bracket set, on the other hand, may include fewer than all brackets needed to treat a patient's dental arch, and may include at least one bracket, as the brackets described may be mixed with other known brackets. The set of brackets intended to be placed on the lingual surface of the patient's front teeth is one representative form. In addition, the bracket set may include one bracket subset for placement on the lower dental arch and a second bracket subset for placement on the upper dental arch.

As stated above, in one possible embodiment, the surface opposite the tooth surface of the bracket base has a shape that corresponds to the three-dimensional surface of the tooth. The thickness of the lock base may be the same over its entire surface (e.g. 0.3mm) or, alternatively, it may vary from, for example, 0.1mm at the edges of the lock base to 0.3mm in the center of the base. Such a form on the one hand provides the required stability of the bracket and on the other hand facilitates the detachment of the bracket base after treatment is completed. Moreover, the thinner the base of the bracket, the greater the patient's comfort. It is currently very difficult to cast a lock with a thickness of less than 0.3 mm, however, other manufacturing techniques such as milling or laser sintering can instead be used to make the lock base.

A detailed description of the construction and manufacture of the latches shown in Figures 2 and 3A is provided later in this description.

Self-aligning atrophy

If the bracket bases used are not individually designed, the "trace of the surface 24 of the bracket 14 adjacent to the tooth (" bracket base) is a compromise. It is clear that the smaller the bracket base is, the smaller there are differences between the bracket base surface and the tooth surface, and there is less need to close larger gaps. On the other hand, the larger the base area, the more stable the adhesive bond is and the lower the risk of the bracket falling off during treatment.

This compromise has been eliminated by exactly matching the shape of the bracket bases 18 (Figs. 2 and 3A) to the shape of the given tooth. The shape of the tooth surface 24 of the bracket base is a negative of the tooth 16 surface, so that no conflicts arise between the tooth surface and the bracket base surface. This allows you to design brackets as flat as possible and thus bring the arch closer to the tooth surface as close as possible. A very big advantage of this

As an approach, the bonding surface can be very large on teeth without significant surface curvatures in the bonding area or where the bonding surface can be shaped according to the cusp curvature of the tooth. This increases the adhesion force, and by covering a large part of the anatomical surface of the tooth, the shape of the bracket precisely determines the position of the bracket. Even without intermediate bonding, each lock is precisely positioned in the desired position. If the lock comes off, it can easily be put back in the desired position without any extra effort. Since the bracket base either covers a large area of ​​the tooth surface or is perfectly matched to the tooth surface curvatures such as cusps, the bracket can be positioned specifically for a given tooth by hand without the aid of any positioners or other bracket alignment tools. If the bracket falls off during treatment, with this type of bracket, manual restoration of the bracket position using surface matching is highly desirable and is indeed possible. However, a rail can be used for the initial simultaneous gluing of a greater number of locks.

Basically, the contact surface or coverage of the bracket base depends on the curvature of the tooth surface. For rather flat teeth, such as lower front teeth, an area as large as 50 percent or more of the tooth surface for lingual brackets and preferably 70 percent or more for labial brackets may be required. For lingual brackets, the coverage area of ​​the bracket base 18 may be 60 to 75 percent or more. The bracket bases may cover, at least in part, a portion of the cusps on the teeth, preferably where the cusps do not contact the opposing teeth during engagement or chewing. Covering the tooth cusp by the bracket base even better allows you to manually adjust the bracket and precisely and individually adjust the bracket to the tooth.

Fig. 4 shows an example of lingual brackets 14 in which the bracket base 18 covers more than 50 percent of the tooth surface. The bracket base has a spatially shaped surface 24 adjacent to a tooth (Fig. 3A, not shown in Fig. 4) that is the negative of the tooth surface, and a second surface 26 that also has the same spatial configuration as the tooth surface. The design of the surfaces 24 and 26 is described in more detail below. It should be noted that in this embodiment, the slots of the brackets need not be parallel to the tooth surface. It should also be noted that the bracket 18 for tooth 16B covers a portion of the tubercle in area 30.

Designing a lock

The brackets for this orthodontic appliance system have to be manufactured individually for each patient, which would be time consuming and costly in the laboratory process. Also, designing the slots of the brackets with optimal orientation is difficult. It is possible to solve this problem by designing the locks, including the geometry of the lock base, including by a computer that operates virtual three-dimensional lock bases, virtual lock wings, and virtual ancillary equipment such as hooks.

The design of the bracket is carried out by means of a computer in which a virtual three-dimensional model of the patient's dentition is stored, and preferably a treatment planning software with which the teeth in the virtual model are moved to the desired target position. Such computers are known. See, e.g., International Patent Publication WO 01/80761 and Chisti et al., United States Patent No. 6,227,850 and United States Patent No. 6,217,325. Design of brackets may be performed by the user at an orthodontic clinic or remote bracket fabrication site.

The geometry data of the bracket base 18 can be taken directly from a digital representation of the patient's teeth to produce bracket bases with shapes substantially matching the conformation of the bracket surfaces. To this end, the shape and size of the bracket base are determined individually for each tooth. This can be done manually with a computer program that makes it possible to determine the desired surfaces on each tooth model by, for example, drawing virtual lines on the tooth models or marking the corresponding surfaces with color. A three-dimensional graphics program such as Magics^TM, which is widely used to manipulate spatial models, defined as a set of related triangles (STL format), allows you to select triangles by clicking on them with the mouse.

Another possibility is to use a software algorithm that automatically or semi-automatically calculates the appropriate bracket base by analyzing the curvature of the tooth surface and determining a surface that will be large enough to cover significant irregularities in the tooth curvature.

The PL 208 345 B1 enabled correct manual positioning of the bracket on the tooth surface. For example, the execution of such an algorithm can start with a predefined size of the lock area. The tooth surface covered by a base of this size will form a virtual "hillock having at least one portion higher than the surrounding anatomical tooth surface, since a completely flat tooth surface would not be suitable for positioning the bracket in a particular individualized position. The volume of such a mound can be calculated using any known method, provided that the edges of the base are connected by a continuous surface. The smaller the curvature of the lock surface, the flatter the mound will be and the smaller its volume will be. If the computed cumulus volume does not exceed a certain predetermined value, the bracket base will automatically increase by a predetermined amount as the larger volume is more likely to cover the corresponding higher tooth irregularities. After such an operation, the volume of the "mound" is recalculated. This algorithm loop is repeated until the minimum volume of each lock base is achieved. Of course, this is only an example of such an automatic calculation algorithm. Other algorithms can be easily developed based on the principles outlined in this specification.

A preferred method of designing the shape of the lock base will now be described in more detail below.

Once the base surface 18 is defined, the tooth shape in this portion accurately defines the desired shape of the portion of the bracket base adjacent to the tooth. There are several options for determining the shape of the exterior of the lock base. The best method of obtaining a thin bracket base is to derive a vector normal to each surface element (e.g. a triangle) describing the surface area of ​​the bracket base adjacent to the tooth and "lift each such element toward the normal vector by a predetermined offset amount corresponding to the desired thickness of the bracket base. This creates a thin shell of the bracket base with the outer surface having the same shape (albeit displaced) as the side adjacent to the tooth. Alternatively, the thickness of the lock base may vary, being smallest (e.g. 0.1mm) at the edges and largest (e.g. 0.3mm) in the center.

The remainder of the bracket, i.e. the wings 20 with the slot 22 and other auxiliary elements enabling the wire to be secured in the slot ("ligating), can be saved in the computer as predefined virtual models, since the wings do not have to be individually adapted to the anatomy of the patient's teeth. Typically, a lock-wing library is created and saved on the computer. Fig. 6A-6C are perspective views of virtual three-dimensional bracket wings stored in the bracket wing library 20 and used to design brackets individually tailored to the anatomy of the patient's teeth. Alternatively and equivalently, the lock-wing library may be stored elsewhere with remote access. Various wings can be placed in such a library for different malocclusions and different treatment plans (high / medium crowding, extraction / non-extraction case, etc.). You can also add virtual assistants downloaded from the library of such elements to the locks. If, for example, lifts are needed to apply forces along an arc (closing a space, etc.), hooks may be added. If the patient has a severe deep bite and it is desired to prevent the patient from completely closing the jaws, a so-called occlusal planes. Illustrative of this are the accessory pieces 32 shown in Figure 5. The accessory pieces 32 are not brackets but are only worn to provide an occlusal plane, preventing complete occlusion.

It is even possible to modify the wingtip models to meet the needs of the orthodontist. Another benefit is that the experience from the treatment plans can be transferred almost instantly to the bracket structure of the wing library.

Once the shape of the bracket base has been defined (including the tooth adjacent surface 24 and the opposite surface 26) and the user has selected the wings 20 to be used with the bracket base in question, the next step is to connect the bracket wings 20 to the bracket base 18. Commonly known software computer-aided design (CAD) gives you several possibilities to design freeforms and connect them together. One particular method is described in detail below. Preferably, the user determines how the lock wings are to be connected to the lock base to result in an individually fitted lock with the desired configuration.

PL 208 345 B1

Since the exact spatial relationship of the wings and the bracket base can be defined using existing 3D graphics programs, one can, for example, take into account the crowding of the anterior teeth: the bracket wings can be moved slightly to the left or right to avoid collisions with the teeth and / or adjacent brackets. at the start of treatment or during the movement of the teeth during treatment. This situation is illustrated in Fig. 7. Note that bracket wings 20A on left tooth 16A and bracket wings 20B on right tooth 16C have been moved toward the edge of base 18 to avoid bracket-tooth collision at the start of treatment. Likewise, the bracket wings can slide up and down to avoid collisions with the opposing teeth. Alternatively, you can simply increase the area of ​​the lock base.

It was also considered to provide the user with the possibility of designing, by means of a computer, a virtual bracket individually tailored to the patient's dental anatomy. The user may use a library containing a number of available virtual lock bases, virtual lock wings and, optionally, virtual aids. The geometric shape of the lock base may be predefined (i.e. may have a specific configuration) or may be defined in three dimensions such that the shape of the bracket base exactly matches the spatial configuration of the patient's tooth surfaces, as will be described in detail below. For example, the orthodontist will be able to order a specific bracket base for the upper left canine (e.g. base 0023 from the list of available bracket bases where base 0023 has a predetermined shape), connect it to specific bracket wings (e.g. wings number 0011 selected from the list of available wing types) and equip the lock with hook number 002. The user can determine the method (as described in this description) of connecting the lock base with the wings or leave it to the manufacturer. In one possible form, the user specifies the lock base, lock wings, and lock support components, views these components as virtual objects on a computer monitor, and combines them to obtain an individually fitted lock. The lock data is then exported to a manufacturing system (e.g. a rapid prototyping system) where the lock is either manufactured directly or a mold or model is produced for manufacturing the lock by casting.

Making a lock

After combining the base and the bolts of the lock into one spatial object, the data representing that object can be exported, for example in STL format, which enables the lock to be manufactured directly by means of rapid prototyping devices. A number of well-known suitable rapid prototyping technologies already exist. These include SLA (stereolithography) technology, LOM (Laminated Object Manufacturing), SLS (Selective Laser Sintering), FDM (Fused Deposition Modeling), SGC (Solid Ground Curing), IJP (Ink Jet Printing). These methods are known to those skilled in the art.

In one of the possible ways you can use the so-called 'A wax printer to produce wax models of the teeth which then form the cores in the casting process. Wax models are cemented and then smelted. Locks may be gold or other alloy cast. You can also make stereolithographic models and use them as mold cores. Other technologies, such as milling in high-speed machine tools, can be used to directly manufacture the brackets. Technologies such as laser sintering (SLS), in which powdered substances are hardened by a numerically controlled laser beam, can be used. Using this technology, the powdered substance can be the plastic from which the mold cores are made, or the metal, and the locks are then produced directly.

In most rapid prototyping systems, objects are produced in layers, which typically causes steps where the modeled surface is not parallel to the layers. Depending on the thickness of such layers, the steps may be almost imperceptible, however, the surface of the gap 22 should be smooth. One possibility is to accept the steps involved in manufacturing with a rapid prototyping system and to mechanically smooth the gaps in the final manufacturing step. A better solution is to eliminate steps by orienting the spatial models in the Rapid Prototyping system such that the gaps of the brackets are aligned parallel to the layers. In this case, the required height of the joint must correspond to the thickness of the layer, in other words the height of the joint must be a full multiple of the thickness of the technological layer.

PL 208 345 B1

Another possibility of obtaining a smooth surface of the slit is to make the slit larger than its target size and to insert a U-shaped insert into it, machined or cast to form the proper slit. This is often done with ceramic brackets to reduce friction between the wire and the gap. This is illustrated in Fig. 8, where a U-shaped insert 40 is positioned in the slot 22.

The strength of the material of the buckle 14 is always a compromise. While the slit portion 22 should be as strong as possible in order to maintain the slit cross-section even when the lock is subjected to high mechanical stress (e.g. when biting hard objects), the base portion 18 should be softer, which makes it easier to remove the slide after removal. the end of treatment. If the bracket base is soft enough, it can literally be lifted off the tooth surface with a suitable tool. Depending on the manufacturing technology, different alloys may be used to achieve this lock material configuration. With centrifugal casting, you can first use a certain controlled amount of hard alloy to make the part where the gap is, and then fill the remainder of the lock mold with a soft alloy (or you can perform these operations in reverse order). It is possible to control the amount of material needed to produce a specific bracket part because the volume of each bracket part can be accurately determined from the spatial model of the bracket. If laser sintering technology is used, different layers can be made of powders of different alloys, provided that the functions of the producing device allow it.

Modular design usually allows the height of the gap to be determined to exactly match the wire cross section. The better the slit matches the wire thickness, the less the wire will play in the slit and the more precise the positioning of the tooth after treatment. It would be possible to adjust the size of the gap to the specific batch of wires to be inserted.

The more clearly the lock / wire system is defined, the fewer problems arise in the equalization phase and the less time it takes to deal with such problems, which overall leads to a shorter treatment period.

The method described below has already been tested with a positive result. It is evident from the comments in the foregoing section of the description that many variations of this method are possible. The description below is illustrated in Figs. 2, 3A and 9A-15.

First, a spatial digital representation of the patient's dentition is created or otherwise obtained. One possibility is to generate an abnormal bite representation from an abnormal bite scan (in vivo or from a model scan), in which case the digital tooth models obtained from the digital representation of the dentition are shifted to the desired target position by means of a computer treatment planning program. This method has been extensively described in WO 01/80761. Another possibility is to create the desired target position manually in a laboratory process in which single tooth models are cut from the plaster models and the teeth are then positioned correctly ("visible treatment target) in the wax plate. Then, a digital representation of the ideal target tooth alignment is created by scanning a real model with an industrial laser scanner. This method is also known in the art, see for example the previously cited patents of Chisti et al.

As soon as a digital representation of the ideal target tooth position is created, the size and shape of the bracket for each tooth are determined. This and the following steps were performed with a ready-made 3D computer graphics program called Magics^TM, developed by Materialize. The use of other computer programs for this purpose is of course possible.

The coverage area of ​​the bracket base 18 is selected for each tooth using the cutout function. This is shown in Figures 9A and 9B. By clicking with the mouse on a series of points 50 on the tooth surface, the desired contour of the bracket base is determined. In this way, the part of the tooth model on which the bracket base will be attached to the tooth is determined. The points 50 are automatically connected with lines 52. The resulting space polygon is smoothed and the surface closed with a line. The computer then converts the surface to an independent surface body. Fig. 10 shows a method carried out for a group of four teeth. Tooth surfaces 54 are transformed into independent bodies as shown in Fig. 11 providing a zero thickness three-dimensional coating. The surfaces 54 will be the bracket base surfaces adjacent to the tooth.

The Magics Offset Part function is then performed. The "Create Thickness" option is activated, which uses the normal vectors of the triangles making up face 54 to shift the shell, thus creating a second shell representing the opposite face 26 of the base 18 of the bracket. These surfaces are then joined by closing the gap between their edges and form a continuous surface. In this way, the spatial shape of the lock base 18 is defined. Current casting techniques require that the base thickness is typically 0.3 mm.

A bracket wing model suitable for the tooth is then selected from the virtual bracket library. Typically, the molars, premolars, and canines will have different wings. Fig. 12 shows the insertion of the lock wings 20 taken from the library on the base 18 at the location 56 (Fig. 11) of the lock in this intermediate step of the method.

The portion of each lock wing 20 that connects to the base 18 is deliberately designed to be much longer than necessary so that, when properly oriented relative to the tooth, the portion will protrude beyond the tooth-adjacent surface of the base. This is illustrated in Figure 12. This is of course undesirable and the portion of the lock extending inwardly beyond the lock base should be eliminated.

In order for the lock to be as thin as possible (e.g. in lingual appliances), the slot 22 should of course be positioned as close to the base 18 as possible, without however causing a collision between the base itself and the slot or wire inserted in the slot.

A portion 20 that projects from the base towards the interior of the tooth is cut using the remodeled tooth model. The Magics ™ program performs Boolean operations, including summation and subtraction functions, whereby all portions of the bracket wings 20 inside the tooth model 16 are removed as described below and illustrated in Figs. 16-21. As a result, some of the bolts of the lock 20 are also shaped exactly to the surface of the tooth and have the same shape as the surface of the base. Figures 13A and 13B show two bracket wings whose surfaces 58 have been modified to reflect the surface of a tooth.

Boolean operations are then performed again to combine the base 18 and lock wings 20 into one virtual spatial object. The object representing the sprue is placed on the lock (in the case of a cast character) and is also linked to the lock model.

This method is repeated for each lock. Fig. 14 shows virtual spatial models of a set of orthodontic brackets of the lingual apparatus for the lower dental arch.

A variation on the above-described method is as follows. First, the bracket wings are taken from the wing library and placed in the correct position relative to the tooth surface. The tooth is then "subtracted from the sum of the flaps and the tooth to remove a portion of the flaps that would otherwise protrude into the tooth. The bracket base is then created by assigning a specific thickness to a surface cut or taken from the tooth surface as performed with respect to surface 54 in the method described above. Then, the modified lock wings are connected to the lock base.

It is possible to use the latch wings as thin as possible, designed and stored in the computer. Essentially, such lock wings will include a slot and little or no more. The user aligns the virtual lock wings at the virtual lock base with a small gap between the lock wings and the lock base. The lock design program has a feature to generate a smooth surface between the base and the bolt of the lock. Software that allows you to generate a smooth surface connecting two virtual objects of any cross-section exists, an example can be a spatial design program sold under the trademark Rhino3D^TM.

Another factor influencing the selection of the bracket wings appropriate for a given tooth is the degree of tooth misalignment. For example, a tooth with a significant angulation should be fitted with a bracket with a wide base to provide satisfactory control of tooth guidance, and a tooth not requiring angulation with a very narrow base should be fitted with a tooth torque that is not required for a given tooth.

Hence, from the foregoing description, it is recognized that a variety of methods for designing and manufacturing the brackets of the invention have been contemplated. People qualified in this field

Still other methods may be selected. The method of producing brackets applies to all the teeth in the dental arch in need and, if desired, the method applies to brackets of the opposing dental arch.

The spatial models of the individually finished brackets are exported to the wax printer in STL format. A wax printer is built similarly to an inkjet printer and builds objects from very many thin layers. First, the bottom layer is printed: a thin stream of liquid wax is sprayed onto the base plate. Parts of the manufactured object are printed with high-melting wax, while the remaining parts are filled with low-melting wax. Then, the surface of the first layer is milled so as to obtain a layer with a precisely defined thickness. All subsequent layers are applied in the same way. After building the object, the low-melting wax parts are removed with a heated solvent.

The wax patterns of all brackets are then cemented with the glands not completely cemented with cement. After the cement has hardened, the molds are heated to remove the molten wax cores, thereby forming hollow molds. A gold-based alloy is poured into the molds, then the molds are destroyed and after removing the inlets, the locks are ready for use.

The resulting individually fitted brackets can be glued individually, but it is more efficient to place them on a plaster malocclusion pattern, fix them with a drop of liquid wax or water-soluble glue, and mimic the entire assembly in silicone to provide a splint for carrying brackets.

Of course, it is also possible to use an OraMetrix bracket for carrying brackets, using the SLA representation of the bracket teeth as described in the international patent publication WO 01/80761.

After completing the bracket design phase for the entire dental arch, the positions of the bracket slots throughout the dental arch are saved as data files and exported to the wire bending robot to bend the orthodontic arch. A six-axis robot described in International Patent Publication WO 01/80761 is suitable for the production of orthodontic wires. The following ewaz location and orientation of each lock are known, and therefore know the location and orientation of each slot can be generated control files robot, comprising a spatial data of each slot, and to use these files to bend the wire into a curve with the configuration shown in FIG. 1 .

Magics ™ allows the user to export the coordinates of individual objects as files in their own format. These are ASCII files with the UCS extension. Such files can be imported into conversion programs and converted into files in the CNA format used by a robot described in the international patent publication WO 01/80761, processing binary transformation matrices. It is obvious that if the whole method of virtual definition of treatment target and virtual bracket design and placement is done by our own wire bending system software, the above-described conversion will not be needed as the CNA files will be generated directly.

Fig. 15A shows prior art lingual brackets using the straight wire technique. Attention is drawn to the large size of the brackets, causing great patient discomfort, articulation problems and other problems discussed earlier. Please compare Fig. 15A with Fig. 15B showing a set of brackets. The locks are much less thick. The advantages of the latch and wire system shown in Fig. 15B are outlined above.

Turning now to Figs. 16-21, the presently preferred method of connecting lock wings 20 to lock base 18 of the computer will be described below. Fig. 16 shows virtual bracket wings 20 connected to virtual bracket base 18 during an intermediate step of designing an individually fitted orthodontic bracket, wherein bracket base 18 and bracket wings 20 constitute two independent virtual spatial objects and the two independent virtual spatial objects can be moved with respect to each other. In the situation shown in Fig. 16, slot 22 is positioned on the lock base 18 in a position as desired by the user, but lock wing portion 60 protrudes beyond the tooth contacting surface of the lock base, which is undesirable.

Fig. 17 shows a window on a computer screen implementing the lock design operations described herein, by which the user combines the base and wings of the lock of Fig. 16 into one virtual object. On the user's computer screen, the base 18 is shown as an object in red and the wings as an object in green. The Magics ™ program has

The link operation icon 62. When the user clicks OK, on ​​screen 64 the two objects 20 and 18 will be combined into one virtual spatial object. Figures 18A and 18B show two views of the base and lock wings combined into one virtual object.

Then an object representing the tooth is taken and an object representing the wings // the base of the bracket is applied to the tooth. Fig. 19 shows the base 18 and the bracket wings 20 of Figs. 18A and 18B positioned on virtual tooth 16.

Then, remove part 60 from the buckle (fig. 18). Fig. 20 shows a screen image of a computer performing a subtraction operation in which an object 16 representing the tooth shown in red is subtracted from an object representing the base 18 of the bracket / latch 20 shown in green. This step is needed to remove the portion 60 of the bracket wings that would otherwise protrude into the tooth. The user selects the operation of subtracting the red object (tooth) from the green object (base / lock wings) by selecting option 66 on the screen and clicking on OK.

Figures 21A and 21B show two views of the wings / base of the bracket after the removal of Figure 20 has been performed. Comparing Figure 17 to Figure 21B it can be seen that the portion 60 of the bracket wings which would otherwise protrude inwardly from the tooth has been removed from the tooth. the object representing the bracket base / wings and the bracket surface 24 adjacent to the tooth is an accurate representation of the tooth surface.

As stated above, it is possible to move the virtual lock wings away from the virtual lock base according to the desired spatial relationship and fill the space between the two objects with suitable computer graphics tools such as Rhino3D to thereby connect the lock wings to the lock base. Alternatively, the lock wings can be snugly fitted to the lock base using 3D computer graphics tools, without having to remove any part of the lock wings. In such a situation, the two virtual objects intersect in such a way that the lock wings only protrude into the inside of the base (e.g., to a depth of intersection of the lock wings and the lock base of, for example, 0.1 mm). Alternatively, two objects can be joined as described above and a portion that would otherwise protrude into the tooth may be removed, as shown in Figures 16-21.

The arcs used can be made of any suitable material known in the art or later. Relatively soft, heat-treated alloys have been found to be particularly suitable. It has been found that such wires are also ideal for bending with a wire bending robot. One such material that is a preferred material in such cases is the cobalt-chrome alloy sold under the trademark BLUE ELGILOY ™ by Rocky Mountain Orthodontics. The composition of this particular orthodontic wire material is as follows: 40% Cobalt, 20% Chromium, 15% Nickel, 7% Molybdenum, 2% Manganese, 0.15% Carbon and the rest iron. A similar alloy sold under the AZURLOY trademark^TM can be purchased from Ormco. These materials are particularly well suited for processing in the six-axis wire bending robot with heated arm grips described in WO 01/80761. Cobalt-chromium alloys are rather soft, which is especially desirable for treatment with lingual braces. Moreover, importantly, these alloys require very little bending to achieve the desired wire bend, which is particularly advantageous from a wire bending point of view, since bending the wire to the desired shape after bending is complete is a process that is difficult to precisely control.

Cobalt-chrome alloy wires are preferably heat treated after bending to increase the strength of the wire. The heat treatment of the wire can be performed by the resistance heating method with robot arm grips described in WO 01/80761, immediately after each wire section has been bent. Alternatively, the wire may be annealed after the entire wire has been bent by placing the wire in a furnace or, alternatively, the wire may be placed in a wire annealing apparatus as described in US Patent No. 6,214,285. The wire is heated at a temperature of about 260 ° C (500F). The purpose of the heat treatment, which in this case is to increase the strength of the wire, is different from that of the heat treatment of the nickel titanium wire and other shape memory wires described in WO 01/80761. The purpose of heat treatment of nickel titanium wires is for the material to conform to the robot bent configuration, while in this case the cobalt chromium wire takes on a bent shape even without heat treatment, and the heat treatment is in this case to increase the strength of the wire.

PL 208 345 B1

These relatively soft wires, especially those of cobalt-chrome alloys, requiring very little bending, are particularly suitable as a bracket material for the lingual braces and oblique curves described herein. The arc forming can be done by a wire bending robot wherein the wire comprises a cobalt-chromium alloy which is then heat treated, for example in a wire bending robot arm, as described in WO 01/80761. The bending and heat treatment of the arc includes the steps of providing the arc to a wire bending robot, bending the arc with a wire bending robot to achieve a predetermined configuration for a given orthodontic patient, and heat treating the arc while the arc remains in the wire bending robot handle. The arc includes cobalt chrome wire, but other alloys requiring heat treatment after bending may be used. The bending and heat treatment step may include making a series of bends of the arc and annealing the wire after making each bend of the series of bends.

It describes how to design locks using a computer and Magics software^TMwherein the surface elements of the lock base, lock tooth, and clips are depicted as triangles. However, there are other acceptable mathematical methods for representing any spatial shapes in a computer, including volumetric annotations (IGES format) and NURB splines that can be used. Although the representation of planar elements with triangles (SLA format) works well for this solution, software based on NURB, such as QuickDraw3D ™, can also be used. NURB software is starting to gain an advantage as it offers a way to represent free-form shapes while maintaining a high degree of mathematical accuracy and distribution independence, allowing complex shapes to be represented with very little data. The methods and software used to design brackets represent one of several possible techniques.

As another example, the manufacturing techniques used to manufacture the brackets are not critical and may differ from the techniques disclosed.

It is understood that reference to arcs of rectangular, square, or the like in this specification includes arcs having substantially the sections listed, but having slightly rounded edges, and, as such, not being exactly rectangular or square sections. Likewise, reference to an arc having flat side planes is intended to embrace an arc having substantially flat side planes, regardless of the roundness of the edges joining the sides of the wire.