Vacant space design method for edentulous space of bracketless invisible orthodontic appliance

Abstract

The present invention discloses a method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance, which solves the technical problem of low implementation rate of the movement of the bracketless invisible orthodontic appliance at the void shape in the edentulous space in the prior art. According to the clinical data of patients undergoing extraction orthodontics, the present invention determines the initial uniform reduction change amount at each step in the orthodontic treatment steps, and uses numerical means to calculate the movement mode, movement amount and tilt deflection amount of the target tooth position under the combined action of the periodontal ligament, attachments and the orthodontic appliance; the control of the shrinkage amount of the orthodontic appliance is transformed into the control of the internal contraction force, and the compensation amount of the orthodontic appliance on both sides of the void is adjusted to complete the control of the tooth space rotation angle, so as to achieve the balanced movement of the teeth. The present invention designs the orthodontic appliance based on numerical calculation and tooth movement compensation control, realizes the improvement of the controllability and predictability of orthodontic tooth movement by adjusting the shape of the void in the edentulous space during bracketless invisible orthodontics, and reduces the common "roller coaster effect" in bracketless invisible orthodontics.

Description

Technical Field

[0001] The invention belongs to the technical field of oral orthodontic equipment, and in particular relates to a method for designing cavitation bubbles in missing teeth spaces of a bracketless invisible orthodontic appliance. Background Art

[0002] For complex cases in orthodontics, such as tooth extraction cases, the designed movement realization rate of bracketless invisible orthodontics is low. Clinical studies have shown that compared with the initial correction design, the current bracketless invisible orthodontics has only a 30-50% realization rate for tooth movement in orthodontics. The realization rate data comes from Simon, Mareike, et al. "Treatment outcome and efficacy of an aligner technique-regarding incisor torque, premolar derotation and molar distalization." BMC Oral Health 14.1 (2014): 1-7; and Kravitz, Neal D., et al. "How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign." American Journal of Orthodontics and Dentofacial Orthopedics 135.1 (2009): 27-35. The main reasons are: 1) the bracketless invisible braces are in sliding contact with the tooth surface; 2) the mechanical properties of the materials used to make the braces; 3) errors in the manufacturing process of the braces.

[0003] Among the many complex orthodontic cases, tooth extraction is the most popular type of bracketless invisible orthodontic treatment. Currently, tooth extraction in bracketless invisible orthodontic treatment commonly results in the tilting and movement of teeth on both sides of the extraction space (e.g. Figure 1 , that is, the crown tilts toward the extraction gap, and the root moves less, or not at all, or moves in the opposite direction). Uncontrollable and unpredictable tooth tilting and movement is also one of the main reasons for poor orthodontic treatment results, prolonged treatment time, and restart of treatment design. At the same time, the "roller coaster effect" in invisible orthodontics has also attracted much attention: compared with the steel wire used in traditional fixed orthodontics to retract the anterior teeth, the invisible orthodontic appliance is limited by its material properties and has weaker rigidity. Therefore, when closing the extraction gap, the teeth before and after the gap tilt toward the gap and stretch at the same time, causing the anterior teeth to further deepen their overbite, affecting the orthodontic effect and course of treatment.

[0004] Existing research has tried to prevent such uncontrollable tilting movement of teeth and reduce the "roller coaster effect" by increasing and improving the quantity and shape of dental surface attachments (such as Figure 1 ). However, the current clinical effect is still not ideal enough.

[0005] Therefore, it has become a technical problem urgently to be solved by those skilled in the art to design a method for the design of the void shape in the edentulous space of a bracketless invisible aligner based on wedge load control, so as to further improve the controllability and predictability of the orthodontic movement of the teeth on both sides of the edentulous space in extraction cases, reduce the occurrence of the "roller coaster effect", and make up for the adverse reactions caused by the insufficient material properties of the invisible aligner. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: to provide a method for designing the void in the edentulous space of a bracketless invisible aligner, so as to solve at least some of the above technical problems.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for designing the void in the edentulous space of a bracketless invisible aligner, which determines the initial uniform contraction amount of the aligner according to the clinical data of the extraction orthodontic patients, and calculates the movement mode, movement amount and tilting and deflection amount of the target tooth position under the combined action of the periodontal ligament, attachments and the aligner by numerical means; converts the control of the aligner contraction amount into the control of the internal contraction force and adjusts the compensation amount of the aligner on both sides of the void to complete the control of the tooth space rotation angle, thereby realizing the balanced movement of the teeth.

[0009] Further, it includes the following steps:

[0010] Step 1, determination of the calculation working surface;

[0011] Step 2, calculation of the deflection amount;

[0012] Step 3, establishment of the void contraction model of the aligner in the edentulous space;

[0013] Step 4, compensation adjustment of the aligner;

[0014] Step 5, error control of the aligner.

[0015] Further, in the said step 1, taking the void area of the aligner in the edentulous space as the adjustment area, a calculation working surface is established according to the initial position of the tooth and the midline of the void.

[0016] Further, in the said step 2, according to the numerical calculation results, the displacements and height differences of the typical positions of the tooth root and the tooth crown are measured, and the deflection amount θ in different directions is calculated by using the following formula i :

[0017]

[0018] wherein, U topi is the displacement of the crown feature position in the i direction, and U boti is the displacement of the root feature position in the i direction, and h tooth is the height difference between the typical positions of the crown and the root; i is three different directions in three dimensions: the x direction, the y direction, and the z direction, that is, the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction.

[0019] Furthermore, in the step 3, according to the initial shortening amount Δ0 and the wedge load coefficient k, the cutting amount of the cavity along the center line direction is determined, the cavity of the edentulous space is cut to form a disconnection area at the geometric level, and spring units are established from the top to the edge of the appliance as a contraction model. The spring units are connected to both sides of the cut cavity, and the internal contraction force of each spring unit is calculated by the following formula according to the cutting length:

[0020]

[0021] F spring is the internal contraction force of the spring unit, Δ0 is the initial shortening amount, and h spring is the vertical height of the spring unit from the top of the cavity, E is the elastic modulus of the appliance, and A spring is the cross-sectional area of the spring unit.

[0022] Furthermore, in the step 4, a preliminary model calculation is performed with the initial shortening amount Δ0 to obtain the tooth angle matrix {Φ i}, and angle projection calculation is performed according to the working surface, which is divided into three parts: the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction. Based on this, the adjustment of both sides of the cavity of the appliance is carried out, and the internal contraction amount of the appliance in the initial edentulous space cavity area is designed, and the wedge coefficient {k} is adjusted.

[0023] Furthermore, in the mesiodistal direction along the dental arch, equal amount of contraction adjustment is performed on both sides of the cavity to calculate the wedge coefficient; in the buccolingual direction perpendicular to the dental arch, separate contraction and stretching adjustments are performed on both sides of the cavity to calculate the wedge coefficient; in the vertical direction, diagonal side contraction adjustment is performed; the compensation angle Φ i The calculation formula is:

[0024]

[0025] wherein, U topi is the displacement of the crown feature position in the i direction, and U boti is the displacement of the root feature position in the i direction, and h tooth is the height difference between the typical positions of the crown and the root.

[0026] Further, in the step 5, after the orthodontic appliance compensation adjustment in step 4, the final calculation results are summarized into the corresponding adjustment angles to control the orthodontic appliance error. The generation formula of the adjustment angle {ε} is as follows:

[0027] {ε} = {Φ - θ} (4);

[0028] Just process and manufacture the designed orthodontic appliance.

[0029] Further, the clinical data of patients with extraction orthodontics at least includes clinical imaging data, dentition data, and occlusal surface photo data.

[0030] Further, when the shrinkage control of the dental appliance is transformed into the control of the retraction force, the wedge load control method is used to establish the adjustment of the compensation amount of the dental appliance on both sides of the cavity according to the relative relationship between the tooth deflection angle and the midline of the cavity of the dental appliance.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention is scientifically and reasonably designed. Based on numerical calculation and tooth movement compensation control, the orthodontic appliance is designed to achieve real-time topological optimization of the void in the edentulous space during bracketless invisible orthodontics, improve the controllability and predictability of orthodontic tooth movement, and reduce the common "roller coaster effect" in bracketless invisible orthodontics. The present invention realizes an automatic method for optimizing the shape of the void in the edentulous space during bracketless invisible orthodontics based on mechanical simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the gap shape in the edentulous area after tooth extraction in the background technology (wherein, Figure a is a view of the gap and attachments in the edentulous area after tooth extraction, Figure b is a void in the shape of a tooth crown in the edentulous area on the bracketless invisible orthodontic appliance, and Figure c is a schematic diagram of the uncontrolled distal tilting movement of the canine tooth).

[0034] Figure 2 It is a flowchart of the method for designing the void in the edentulous space of the bracketless invisible orthodontic appliance of the present invention.

[0035] Figure 3 It is a schematic diagram for calculating the tooth deflection amount of the present invention.

[0036] Figure 4 It is a schematic diagram for establishing the spring unit from the top to the edge of the orthodontic appliance of the present invention (the main target tooth is shown in the figure, and the other teeth in the dentition are not shown).

[0037] Figure 5 It is a schematic diagram of the orthodontic appliance compensation adjustment method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0039] As Figure 2-5 shown, the objective of the present invention is to provide a method for designing voids in the tooth extraction gap of a bracketless invisible orthodontic appliance to improve the controllability and predictability of orthodontic tooth movement in extraction cases. The prior art has not involved any attempts to improve the void shape at the tooth extraction gap of invisible orthodontic appliances. The void shape only considers aesthetics and ease of processing, without any mechanical considerations. The present invention creatively proposes to optimize the mechanical results by changing the void shape at the tooth extraction gap, and the introduced optimization method makes the void shapes at the tooth extraction gaps of each orthodontic appliance inconsistent. Each void shape is automatically optimized based on the mechanical simulation results of the teeth in the current step, achieving an ideal mechanical design and obtaining ideal controllability and predictability of orthodontic tooth movement.

[0040] The present invention determines the initial uniform reduction amount of the orthodontic appliance based on the clinical data of patients undergoing extraction orthodontics, and uses numerical means to calculate the movement mode, movement amount, and tilt and deflection amount of the target tooth position under the combined action of the periodontal ligament, attachments, and orthodontic appliance; uses the wedge load control method to convert the control of the appliance shrinkage amount into the control of the internal contraction force, and adjusts the compensation amount of the orthodontic appliance on both sides of the void according to the relative relationship between the tooth deflection angle and the midline of the void in the orthodontic appliance, so as to complete the control of the tooth space rotation angle and achieve the parallel movement of the teeth. The clinical data of patients undergoing extraction orthodontics at least includes clinical imaging data, dentition data, and occlusal surface photo data.

[0041] As Figure 2 shown, the present invention includes the following steps:

[0042] Step 1: Determine the calculation working surface. Taking the void area of the tooth extraction gap of the orthodontic appliance as the adjustment area, establish a calculation working surface based on the initial tooth position and the midline of the void.

[0043] Step 2: Calculate the deflection amount.

[0044] As Figure 3 shown ( Figure 3 only the dentition segment of the canine tooth (tooth No. 3), the first premolar (tooth No. 4), and the second premolar (tooth No. 5) is taken as an example in the figure, and the anterior tooth row of the extraction gap is considered as a whole in actual cases), according to the numerical calculation results, measure the displacement and height difference of the typical positions of the tooth root and the tooth crown, and use the following formula to calculate the deflection amount θ in different directions i :

[0045]

[0046] Among them, U topi is the displacement of the crown feature position in the i direction, and U boti is the displacement of the root feature position in the i direction, and h tooth is the height difference between the typical positions of the crown and the root. i represents three different three-dimensional directions: the x-direction, the y-direction, and the z-direction, that is, the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction.

[0047] Step 3: Build a contraction model for the void in the tooth gap of the appliance.

[0048] Determine the cutting amount of the void along the center line according to the initial shortening amount Δ0 and the wedge load coefficient k, cut the void in the tooth gap to form a disconnected area at the geometric level, and establish spring elements from the top to the edge of the appliance as the contraction model (as Figure 4 shown). The spring elements are connected to both sides of the cut void. The internal contraction force of each spring element is calculated using the following formula according to the cutting length:

[0049]

[0050] F spring is the internal contraction force of the spring element, Δ0 is the initial shortening amount, h spring is the vertical height of the spring element from the top of the void, E is the elastic modulus of the appliance, and A spring is the cross-sectional area of the spring element.

[0051] Step 4: Compensatory adjustment of the appliance.

[0052] Perform preliminary model calculations with the initial shortening amount Δ0 to obtain the tooth angle matrix {Φ i}, perform angle projection calculations according to the working surface, divide it into three parts: the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction, and accordingly adjust both sides of the void in the appliance, design the internal contraction amount of the appliance in the initial tooth gap void area, and adjust the wedge coefficient {k}.

[0053] In the mesiodistal direction along the dental arch, both sides of the void are equally contracted and adjusted to calculate the wedge coefficient; in the buccolingual direction perpendicular to the dental arch, both sides of the void are respectively contracted and stretched to adjust and calculate the wedge coefficient; in the vertical direction, diagonal side contraction adjustment (as Figure 5 shown. In the figure, only tooth No. 3 is taken as an example, and in actual cases, the anterior teeth in the extraction gap are considered as a whole). The calculation formula for the compensation angle Φ i is:

[0054]

[0055] Among them, U topi is the displacement of the crown feature position in the i direction, and Uboti is the displacement of the root characteristic position in the i direction, h tooth is the height difference between the typical positions of the crown and the root.

[0056] Step 5. Appliance error control.

[0057] After the appliance compensation adjustment in Step 4, the final calculation results are summarized into the corresponding adjustment angles to control the appliance error. The generation formula for the adjustment angle {ε} is as follows:

[0058] {ε} = {Φ - θ} (4);

[0059] Just process and manufacture the designed appliance.

[0060] Compared with the existing design, the present invention can further improve the controllability and predictability of the orthodontic movement of the teeth on both sides of the edentulous space in extraction cases, reduce the occurrence of the "roller coaster effect", and make up for the adverse reactions caused by the insufficient material properties of the invisible appliance.

[0061] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be elaborated in detail again in combination with the following examples.

[0062] This example is a common clinical Class I, skeletal Class I, bimaxillary protrusion patient, and a clinical common orthodontic design of extracting 4 first premolars in the upper and lower jaws and retracting the upper and lower anterior teeth with strong anchorage to improve the protrusion. In this case, the specific extraction space compensation design method is as follows:

[0063] 1) Acquisition, storage of clinical data and determination of orthodontic design: According to the current bracketless orthodontic design requirements, obtain the patient's facial, dental arch photos, cephalometric films, maxillofacial CBCT data, and dental arch three-dimensional model data. Upload the above clinical data and design the orthodontic treatment plan. The orthodontic treatment plan includes the initial and final positions of the dental arch, attachment design, specific orthodontic steps, etc.

[0064] 2) Selection of orthodontic steps that require extraction space compensation design: Select the orthodontic steps in which distal movement of the anterior teeth and reduction of the extraction space are designed in all orthodontic steps to enter the subsequent extraction space compensation design link.

[0065] 3) Construction of the dental arch model and appliance model: Based on the patient's maxillofacial CBCT data, dental arch three-dimensional model data and orthodontic design plan, construct an overall calculation model of the upper and lower jaws, teeth, periodontal membrane, attachments and appliances. In this case, the upper dental arch is taken as an example. In this case, the dental appliance in the extraction space area adopts a tunnel-type design with the same cross-section, and mainly explains the inclination adjustment steps in the working plane. The extraction space area can also adopt designs including but not limited to the shape of the dental crown.

[0066] 4) Establishment of local coordinate system: For each tooth within the dental arch, a coordinate system is determined with the mesiodistal direction, buccolingual direction, and vertical direction as the axes.

[0067] 5) Determination of calculation working surface: Taking the mesiodistal direction as an example, with the edentulous space vacuole area of the appliance as the adjustment area, a calculation working surface is established based on the central axis of the initial position of the teeth before the extraction space and the mesiodistal midline of the extraction space vacuole.

[0068] 6) Calculation of deflection amount: In the aforementioned overall calculation model, the interaction between the appliance and the tooth crown is loaded, and the displacement movement of the teeth is calculated. Using the pre-set node numbers of the detection points on the tooth crown and root, the U topi and U boti values are quickly output, and combined with the tooth height, the deflection amount in the mesiodistal direction is calculated. The deflection amounts in the buccolingual direction and vertical direction can be obtained in the same way.

[0069] 7) Construction of the contraction model for the edentulous space vacuole of the appliance: According to the preset contraction amount of the extraction space vacuole, that is, the distal movement amount of tooth No. 3 in this step, which is 0.2 mm in this example, the initial shortening amount for this time is determined, and this value is used for both the cross-section and the gingival side at the vacuole. Set the wedge load coefficient k, and the stiffness of the spring element is obtained according to formula (2).

[0070] 8) Appliance compensation adjustment method and error control method: The wedge load coefficient k can be adjusted starting from 0 and gradually increased, which is convenient for iterative calculation. The calculation results of tooth displacement are obtained for each iteration. According to formula (3), the difference between the natural adjustment deflection of the root and the wedge adjustment of the vacuole is solved: When the differences in the three different directions reach the preset error, it can be considered that the compensation adjustment is completed. By superimposing the compensations in the three directions, the final optimized appliance design can be obtained.

[0071] 9) Fabrication of the appliance based on the optimized design: Based on the calculated compensation results, the corresponding tooth positions can be obtained for 3D printing of the dental arch model to fabricate a thermoformed appliance; or directly 3D print the appliance.

[0072] Currently, for aesthetic reasons, in the case of extraction cases, the shape of the appliance at the extraction space of the bracketless invisible appliance is generally a vacuole-like or tunnel-like shape similar to the tooth crown.

[0073] However, optimizing the edentulous space vacuole of the bracketless invisible appliance to improve the controllability and predictability of tooth orthodontic movement is still blank.

[0074] The objective of the present invention is to provide a method for designing the vacuole morphology in the tooth extraction gap of a bracketless invisible orthodontic appliance based on wedge load control, so as to improve the controllability and predictability of orthodontic tooth movement in extraction cases. The prior art has not involved any attempts to improve the vacuole morphology at the tooth extraction gap of invisible orthodontic appliances. The vacuole morphology only considers aesthetics and processing difficulty, without any mechanical considerations. The present invention innovatively proposes to optimize the mechanical results by changing the vacuole morphology at the tooth extraction gap, which is quite innovative. Moreover, the introduced shape adjustment calculation method makes the vacuole morphology at the tooth extraction gap of each orthodontic appliance inconsistent, and each is a shape automatically calculated based on the mechanical simulation results of the teeth in the current step, achieving an ideal design in terms of mechanics to obtain ideal controllability and predictability of orthodontic tooth movement.

[0075] In addition, the morphology of the vacuole in the tooth extraction gap can be changed according to requirements, and the optimization constraints include: ① the designed tooth movement; ② the vacuole morphology preference: including but not limited to tunnel-shaped or tooth-crown-shaped.

[0076] Doctors can modify the optimization constraints according to the above clinical actual requirements to obtain an ideal effect in terms of mechanics.

[0077] At present, all processes of bracketless invisible orthodontics, from the collection of patients' clinical data, the design of orthodontic steps, the processing and production of orthodontic appliances to clinical wearing and follow-up visits, are already very perfect. After completing the collection and uploading of routine clinical imaging data, dentition data, and occlusal surface photo data, routine computer-based orthodontic step design is carried out. The present invention provides an appliance design method for extraction cases in bracketless invisible orthodontics based on numerical calculation and vacuole shrinkage compensation control in the tooth extraction gap of bracketless invisible orthodontic appliances, which can achieve overall controllable movement of the target teeth during the correction process, reduce the common "roller coaster" effect in bracketless invisible orthodontics, that is, the phenomenon of out-of-control tooth inclination, and provide a basic support for the pre-orthodontic treatment plan.

[0078] After the user (usually an orthodontist) and the invisible orthodontic appliance company jointly complete the design of orthodontic steps, the computer automatically determines the direction, mode, and magnitude of the movement of each tooth in each step. Automatically select the steps with reduced tooth extraction gaps in the orthodontic steps and include them in the optimization sequence. The optimization goal is to make the orthodontic tooth movement in the simulation calculation results as consistent as possible with the designed ones, and to minimize the un-designed forward tooth elongation and inclined movement.

[0079] An orthodontic appliance design method based on numerical calculation and shrinkage compensation control of a bracketless invisible orthodontic appliance. According to the orthodontic steps, the initial uniform shrinkage change amount of the orthodontic appliance is determined. Numerical means are used to calculate the movement mode, movement amount, and tilt deflection amount of the target tooth position under the combined action of the periodontal ligament, attachments, and the orthodontic appliance. Using the wedge load control method, the shrinkage control of the dental appliance is transformed into internal contraction force control. Considering the relative relationship between the tooth deflection angle and the midline of the dental appliance void, an adjustment strategy for the compensation amount of the dental appliance on both sides of the void is established to complete the angle control of the tooth space rotation, and finally achieve the balanced movement of the teeth, reducing the "roller coaster" effect and the amount of tooth tilt movement caused by the existing orthodontic appliances.

[0080] The orthodontic appliance completed by the optimized design enters the conventional orthodontic appliance processing and manufacturing process. Subsequent clinical wearing and follow-up visits are the same as those of the existing invisible orthodontic appliances.

[0081] In addition, in order to avoid the problem that the adjacent teeth at the tooth loss gap of the optimized orthodontic appliance are prone to prolapse, attachments for strengthening retention can be placed at the tooth positions on both sides of the tooth loss gap, which is basically the same as the current conventional design.

[0082] Finally, it should be noted that the above embodiments are only the preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting it, and certainly not limiting the patent scope of the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; that is to say, any meaningless changes or touch-ups made on the main design idea and spirit of the present invention, as long as the technical problems solved are still the same as those of the present invention, should be included in the protection scope of the present invention; in addition, directly or indirectly applying the technical solutions of the present invention to other related technical fields shall also be included in the patent protection scope of the present invention by the same token.

Claims

1. A method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance, characterized in that, Determine the initial uniform retraction change amount of the appliance based on the clinical data of patients with extraction orthodontics. Use numerical means to calculate the movement mode, movement amount, and inclination and deflection amount of the target tooth position under the combined action of the periodontal ligament, attachments, and the appliance. Convert the appliance shrinkage amount control into internal retraction force control and adjust the compensation amount of the appliance on both sides of the void to complete the control of the tooth space rotation angle, thereby achieving balanced tooth movement. When converting the appliance shrinkage amount control into internal retraction force control, use the wedge load control method, and establish the adjustment of the compensation amount of the appliance on both sides of the void according to the relative relationship between the tooth deflection angle and the midline of the appliance void.

2. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 1, characterized in that, It includes the following steps: Step 1: Determine the calculation working surface; Step 2: Calculate the deflection amount; Step 3: Build the shrinkage model of the appliance tooth extraction gap void; Step 4: Adjust the appliance compensation; Step 5: Control the appliance error.

3. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 2, characterized in that, In the said Step 1, take the appliance tooth extraction gap void area as the adjustment area, and establish the calculation working surface according to the initial tooth position and the midline of the void.

4. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 2, characterized in that, In step 2, according to the numerical calculation results, displacements and height differences at typical positions of the tooth root and the tooth crown are measured, and the deflection amount θ in different directions is calculated using the following formula i : Among them, U topi is the displacement of the crown feature position in the i direction, and U boti is the displacement of the root feature position in the i direction, and h tooth is the height difference between the typical positions of the crown and the root; i is three different directions in three dimensions: the x direction, the y direction, and the z direction, that is, the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction. A corresponding coordinate system is established respectively according to the position of each tooth.

5. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 2, characterized in that, In the said Step 3, determine the cutting amount of the void along the center line according to the initial shortening amount Δ0 and the wedge load coefficient k, cut the tooth extraction gap void, form a disconnected area at the geometric level, and establish a spring element from the top of the appliance to the edge as the shrinkage model. The spring element is connected to both sides of the cut void. The internal retraction force of each spring element is calculated by the following formula according to the cutting length: F spring is the retraction force of the spring unit, Δ0 is the initial shortening amount, h spring is the vertical height of the spring unit from the tip of the air cavity, E is the elastic modulus of the appliance, A spring is the cross-sectional area of the spring unit.

6. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 2, characterized in that, In the step 4, a preliminary model calculation is performed with an initial shortening amount Δ0 to obtain a tooth angle matrix {Φ i}, and angle projection calculation is performed according to the working surface, which is divided into three parts: the mesiodistal direction along the dental arch, the buccolingual direction perpendicular to the dental arch, and the vertical direction. Based on this, the adjustment on both sides of the appliance void is carried out, the initial retraction amount of the appliance in the void area of the edentulous space is designed, and the wedge coefficient {k} is adjusted.

7. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 6, characterized in that, For the mesiodistal part along the dental arch, equal shrinkage adjustment is made on both sides of the void to calculate the wedge coefficient; for the buccolingual part perpendicular to the dental arch, separate shrinkage and stretching adjustments are made on both sides of the void to calculate the wedge coefficient; Vertical part, diagonal side contraction adjustment; compensation angle Φ i The calculation formula is: Among them, U topi is the displacement of the crown feature position in the i direction, and U boti is the displacement of the root feature position in the i direction. h tooth is the height difference between the typical positions of the crown and the root.

8. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 2, characterized in that, In the said Step 5, after the appliance compensation adjustment in Step 4, summarize the final calculation results into the corresponding adjustment angles to control the appliance error. The generation formula of the adjustment angle {ε} is as follows: {ε} = {Φ - θ} (4); Just process and manufacture the designed appliance.

9. The method for designing a void in the edentulous space of a bracketless invisible orthodontic appliance according to claim 1, characterized in that, The clinical data of patients with extraction orthodontics at least includes clinical imaging data, dentition data, and occlusal surface photo data.

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