Dental instrument

Abstract

The embodiment of the utility model provides a dental instrument which comprises a shell-shaped body, the shell-shaped body is provided with a plurality of tooth containing cavities and a traction part, the traction part is of a cavity structure formed by protruding and extending from the surface of the shell-shaped body to the far-tooth direction, and the traction part and the edge of the shell-shaped body are arranged in a spaced mode; the side surface of the traction part is provided with an opening structure used for hanging a traction piece, the side surface of the traction part is further provided with a reinforcing ridge formed by protruding or recessing part of the side surface, one end of the reinforcing ridge is adjacent to the free end of the traction part, the other end of the reinforcing ridge is far away from the free end of the traction part, and the whole reinforcing ridge is roughly arranged in the protruding and extending direction. Through the arrangement, the anti-bending section coefficient of the side surface of the traction part under the action of traction force can be effectively improved, so that the deformation resistance of the side surface of the traction part in the traction direction is improved.

Description

Technical Field

[0001] This application relates to the field of orthodontic technology, and in particular to a dental instrument. Background Art

[0002] In clinical orthodontic treatment, functional attachments are sometimes used to enhance the orthodontic effect when using shell-type orthodontic appliances. Common functional attachments include traction structures, which suspend traction components so that traction force is applied to the corresponding areas. In many cases, such as anterior tooth intrusion, tooth elongation, gap adjustment, eruption traction, and tooth rotation, traction structures are needed for auxiliary treatment.

[0003] In existing technologies, one method involves creating a small notch (i.e., a traction hook) at the edge of the tooth cavity corresponding to the tooth requiring traction in the clear aligner. When wearing the aligner, the traction element is hooked onto the traction hook for retention, while the other side is hooked onto another traction hook or a lingual clip to achieve traction between the teeth. However, when the traction force is too great, this method can cause the edge of the aligner to flip outward, forming a raised edge. Not only will the traction element slip off, but the raised edge can also easily scratch the oral mucosa. Another approach involves extending a raised structure outward from the surface of the clear aligner away from the edge, with an opening on the side surface of the raised structure for attaching the traction device. While this structure avoids edge curling, during traction, the raised structure itself is a hollow structure, and the opening further compromises its integrity. Therefore, if the traction force is slightly too large, the side surface of the raised structure will deform, causing the actual direction of the traction force to deviate from the preset direction, thus failing to achieve the desired treatment result. Furthermore, if the side surface of the raised structure is excessively bent and deformed, the traction device may detach from the opening, causing the raised structure to completely lose its traction function, and the treatment plan cannot be effectively implemented. Utility Model Content

[0004] The purpose of this application is to provide a dental instrument that can effectively improve the deformation resistance of a traction-functional protrusion, thereby providing a more stable traction force during orthodontic treatment and improving the orthodontic effect.

[0005] To achieve the above objectives, embodiments of this application provide a dental instrument, including a shell-shaped body having multiple tooth receiving cavities and a traction portion. The traction portion is a cavity structure formed by protruding from the surface of the shell-shaped body toward the distal tooth, and the traction portion is positioned at a distance from the edge of the shell-shaped body. The side surface of the traction portion has an opening structure for suspending traction components, and the side surface of the traction portion also has a reinforcing ridge formed by a portion of the side surface protruding or recessed, wherein one end of the reinforcing ridge is adjacent to the free end of the traction portion, and the other end is positioned away from the free end of the traction portion.

[0006] Preferably, the angle between the long axis of the projection of the reinforcing ridge onto the longitudinal section of the traction part and the protruding direction of the traction part is greater than or equal to 0° and less than or equal to 60°.

[0007] Preferably, the height of the opening structure in the protruding direction does not exceed 1 / 2 of the height of the traction part in the protruding direction.

[0008] Preferably, the protrusion height of the traction part in the extension direction is between 1.5mm and 2mm.

[0009] Preferably, the highest point of the reinforcing ridge in the convex direction exceeds the opening structure.

[0010] Preferably, the length of the reinforcing ridge in the convex direction is greater than or equal to half the height of the traction part in the convex direction.

[0011] Preferably, the traction portion is located on at least one of the tooth receiving cavities.

[0012] Preferably, the lowest point of the traction portion in the gingival-occlusal direction does not exceed the occlusal plane.

[0013] Preferably, the shell-shaped body further includes an extension portion connected to the tooth receiving cavity, wherein when worn, the extension portion corresponds to the gingival region, and the traction portion is located on the extension portion.

[0014] Preferably, the side surface where the opening structure is located is the first surface, and the surface on the traction part that is opposite to the first surface is the second surface. The projection of the end of the first surface near the extension part in the traction direction is the first projection, and the projection of the end of the first surface away from the extension part in the traction direction is the second projection. The first projection is closer to the second surface than the second projection.

[0015] Preferably, the direction in which the first surface extends from the end near the extension to the end away from the extension is the first direction, and the angle between the first direction and the traction direction is greater than 90° and less than or equal to 150°.

[0016] Preferably, the first surface and the second surface are arranged parallel to each other.

[0017] The dental instrument with traction function provided by this utility model has at least the following advantages compared with the prior art:

[0018] The purpose of this technology is to improve the structural morphology of the traction unit in existing invisible aligners to enhance its tensile strength. The traction unit on the surface of the invisible aligner has a protruding cavity structure with traction function. To achieve more stable traction force, the side surface of the cavity structure has an opening for suspending the traction element. Addressing the issue of deformation at stress concentration points during traction, the side surface of the cavity structure also has reinforcing ridges formed by partial protrusions or recesses to improve its deformation resistance. One end of the reinforcing ridge is adjacent to the free end of the traction unit, while the other end is away from it, so that the reinforcing ridge is generally aligned with the protrusion direction. This arrangement effectively increases the bending section modulus of the side surface of the traction unit under traction force, thereby improving its resistance to deformation in the traction direction. Especially when the direction of the traction force is approximately perpendicular to the protrusion direction, the reinforcing ridge's overall alignment with the protrusion direction further enhances the bending section modulus of the side surface of the traction unit under traction force, thus improving its resistance to deformation in the traction direction. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0020] Figure 1 This is a schematic diagram of the structure of a shell-shaped orthodontic appliance with traction function in the prior art;

[0021] Figure 2 This is a schematic diagram of the protruding structure used for traction on a shell-shaped orthodontic appliance in the prior art;

[0022] Figure 3 These are structural diagrams of dental instruments in some embodiments of this application;

[0023] Figure 4 yes Figure 3 A magnified view of a portion of region A in the middle;

[0024] Figure 5 These are schematic diagrams of the traction unit in some embodiments of this application;

[0025] Figure 6 yes Figure 5 A schematic diagram of the central traction unit from another perspective;

[0026] Figure 7 These are schematic diagrams of the traction unit in other embodiments of this application;

[0027] Figure 8 These are schematic diagrams of the traction unit in other embodiments of this application;

[0028] Figure 9 yes Figure 8 A schematic diagram of the projection of the central traction unit onto its longitudinal section;

[0029] Figure 10 These are structural diagrams of dental instruments in other embodiments of this application;

[0030] Figure 11 These are schematic diagrams of the traction unit in other embodiments of this application;

[0031] Figure 12 These are schematic diagrams illustrating the wearing of dental instruments in some embodiments of this application;

[0032] Figure 13 These are schematic diagrams illustrating the wearing of dental instruments in other embodiments of this application;

[0033] Figure 14 These are schematic diagrams illustrating the wearing of dental instruments in other embodiments of this application;

[0034] Figure 15 These are schematic diagrams illustrating the wearing of dental instruments in other embodiments of this application;

[0035] Figure 16 yes Figure 15 A magnified view of a portion of region D in the middle;

[0036] Figure 17 yes Figure 15 A magnified view of a portion of region D. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this application to enable readers to better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0038] Shell-type orthodontic appliances are invisible and aesthetically pleasing mechanical devices for teeth straightening, designed and manufactured using computer-aided 3D modeling. They are typically worn on the teeth and are made of polymer materials such as TPU, PETG, or a combination of both. These appliances exert forces that cause changes in the malocclusion of the jawbone, misaligned teeth, and periodontal tissues, promoting normal dentofacial growth and development. Shell-type appliances utilize biomechanical principles to correct malocclusion. Through a system consisting of a series of shell-type appliances, gentle and sustained biomechanical forces are applied to gradually move the teeth back to their correct positions and align them properly. During treatment, additional attachments or unique structures are often incorporated into the shell-type appliances to apply extra corrective forces to the teeth.

[0039] In the prior art, in order to save costs and reduce processing difficulty, reference is made to... Figure 1 and Figure 2 As shown, when applying traction on a shell-shaped orthodontic appliance, a one-piece molded shell-shaped appliance 100 with traction function is typically used. The shell-shaped appliance 100 has a raised structure 200 that communicates with the tooth cavity. The side surface of the raised structure 200 has a partial opening 300 for suspending the traction element. Although this method is simple to manufacture, because the raised structure 200 itself is a hollow structure, and the opening structure 300 disrupts the integrity of the raised structure 200, during traction, the portion bearing the traction force is only the connection point 400 of the non-opening portion on the side surface. The connection point 400 itself has limited load-bearing capacity. When the traction force is too large, the connection point 400 will deform. Furthermore, when the direction of the traction force is tilted away from the teeth, the portion of the raised structure 200 not connected to the tooth cavity will lift under the action of the traction force. All of these problems ultimately lead to the deformation of the raised structure 200, rendering it unusable.

[0040] The various embodiments of this application will now be described with reference to the accompanying drawings.

[0041] refer to Figures 3 to 5As shown, an embodiment of this application provides a dental instrument, including a shell-shaped body 1. The shell-shaped body 1 has multiple tooth receiving cavities 11 and a traction part 12. Preferably, the multiple tooth receiving cavities 11 of the shell-shaped body 1 cover all the teeth on the maxilla or mandible. The traction part 12 is a cavity structure that protrudes from the surface of the shell-shaped body 1 toward the distal tooth direction. The traction part 12 is spaced apart from the edge of the shell-shaped body 1 to prevent deformation at the edge of the shell-shaped body 1 during traction. The side surface of the traction part 12 has an opening structure 121 for suspending the traction element. The side surface of the traction part 12 also has a reinforcing ridge 122 formed by a partial protrusion or recess of the side surface. One end of the reinforcing ridge 122 is adjacent to the free end 12a of the traction part 12, and the other end is disposed away from the free end 12a of the traction part 12. This arrangement makes the reinforcing ridge 122 generally arranged along the protrusion direction L, increasing the resistance of the traction part 12 to deformation under traction force. Specifically, since the direction of the traction force is set approximately perpendicular to the extension direction L, setting the reinforcing ridge 122 approximately along the extension direction L can effectively improve the bending section modulus of the side surface of the traction part 12 under the action of the traction force, thereby improving the deformation resistance of the side surface of the traction part 12.

[0042] In some embodiments, the angle α between the major axis of the reinforcing ridge 122 projected onto the longitudinal section of the traction portion 12 and the protruding direction L of the traction portion 12 is greater than or equal to 0° and less than or equal to 60°. See details. Figures 5 to 7 As shown, the angle α between the major axis direction P of the projection of the reinforcing ridge 122 onto the longitudinal section of the traction part 12 and the protruding direction L of the traction part 12 is greater than or equal to 0° and less than or equal to 60°, preferably greater than or equal to 0° and less than or equal to 30°. The advantage of this design is that it avoids the major axis direction P of the projection of the reinforcing ridge 122 onto the longitudinal section of the traction part 12 being the same as the direction of the traction force (i.e., the stretching direction of the traction member 3 in the figure), which would prevent the cavity structure from failing to resist deformation under traction force. In other words, the major axis direction P of the projection of the reinforcing ridge 122 onto the longitudinal section of the traction part 12 is as perpendicular as possible to the traction direction, thereby effectively improving the cavity structure's resistance to deformation.

[0043] In some embodiments, reference Figure 8 and Figure 9 As shown, the protrusion height H1 of the traction part 12 along the protrusion direction L is between 1.5mm and 2mm. The traction part 12 protruding from the surface of the shell-shaped body 1 allows for a larger overall size compared to a traction part 12 directly cut from the surface of the shell-shaped body 1, thus providing greater traction strength. However, the protrusion height of the traction part 12 should not be too high; a protrusion height H1 between 1.5mm and 2mm can reduce the abrasion of the traction part 12 on the oral mucosa and improve orthodontic comfort.

[0044] In some embodiments, continue to refer to Figure 8 and Figure 9 As shown, the height H2 of the opening structure 121 in the protruding direction L does not exceed half of the height H1 of the traction part 12 in the protruding direction L. The opening structure 121 is positioned closer to the shell-shaped body 1. This arrangement allows the traction force to be positioned closer to the shell-shaped body 1 after the traction member is suspended, enabling the area where the traction part 12 is connected to the shell-shaped body 1 to jointly bear the traction force, thus reducing the likelihood of deformation of the traction part 12. Furthermore, referring to… Figure 7 As shown, when the direction of the traction force is not perpendicular to the protrusion direction L, especially when it is tilted away from the tooth, the opening structure 121 is set closer to the shell-shaped body 1, which makes the part of the traction part 12 that is away from the shell-shaped body 1 relative to the opening structure 121 (the part located at the free end of the traction part 12) larger in size and less likely to deform under the action of the traction force, thereby ensuring the structural stability of the traction part 12 during the traction process.

[0045] In some embodiments, continue to refer to Figure 8 and Figure 9 As shown, the reinforcing ridge 122 is provided on the side surface of the traction part 12 that does not have the opening structure 121. This is because the opening structure 121 disrupts the structural integrity of the traction part 12. During traction, when the traction member is suspended by the opening structure 121, the side surface of the traction part 12 that does not have the opening structure 121 is the main part bearing the traction force. Therefore, providing the reinforcing ridge 122 in this area effectively improves the deformation resistance of this area. Furthermore, the highest point C of the reinforcing ridge 122 in the convex direction L exceeds the opening structure 121, so that the portion of the traction part 12 that is farther from the shell-like body 1 relative to the opening structure 121 (the portion located at the free end of the traction part 12) also has a reinforcing ridge 122. The advantage of this design is that it improves the deformation resistance and torsional resistance of the portion of the traction part 12 that is farther from the shell-like body 1 relative to the opening structure 121. During traction, when the direction of the traction force is not perpendicular to the protrusion direction L, especially when it is tilted away from the teeth, it avoids the problem that the portion of the traction part 12 that is farther from the shell-like body 1 relative to the opening structure 121 will be lifted up under the action of the traction force, causing the traction part 12 to lose its traction function. Further preferred, refer to... Figure 9 As shown, the length H3 of the reinforcing ridge 122 in the extension direction L is greater than or equal to half the height H1 of the traction part 12 in the extension direction L. This arrangement ensures that the dimensions of the reinforcing ridge 122 in the extension direction L cover as much as possible the height of the traction part 12 in the extension direction L, thereby ensuring the deformation resistance of the traction part 12.

[0046] In some embodiments, reference Figure 3As shown, the traction part 12 is disposed on the tooth receiving cavity 11 of the shell-shaped body 1, and the traction part 12 is located on at least one of the tooth receiving cavities 11. The cavity structure of the traction part 12 communicates with the interior of the tooth receiving cavity 11. In order to reduce the foreign body sensation of the traction part 12 in the mouth, the overall size of the cavity structure is smaller than the size of a single tooth receiving cavity 11. Reference Figure 10 As shown, depending on the requirements of different orthodontic positions, the cavity structure of the traction unit 12 can be located on a single tooth receiving cavity 11 or between two tooth receiving cavities 11. Similarly, depending on different traction directions, the traction unit 12 can be located on the labial / buccal side and / or lingual side of the tooth receiving cavity 11.

[0047] In some embodiments, the major axis of the cross-section of the traction part 12 perpendicular to the traction direction is parallel to the traction direction. It is understood that the overall shape of the traction part 12 is a cylinder (elliptical cylinder), frustum (elliptical frustum), prism, or frustum. When the cross-sectional shape is perfectly circular, it is not considered in this embodiment. The cross-sectional shape having one and only one major axis is the focus of this embodiment. For a more preferred embodiment, refer to... Figure 11 As shown, the overall shape of the traction unit 12 is a frustum ellipse, and the cross-sectional shape of the traction unit 12 is elliptical. The major axis Q of the ellipse is parallel to the traction direction (i.e., the stretching direction of the traction member 3 in the figure). Within a certain dimensional range, how to design the shape of the traction unit 12 to ensure the provision of traction force is also a key consideration in this application. Setting the major axis of the cross-sectional shape parallel to the traction direction can effectively improve the overall resistance to deformation of the traction unit 12 during the traction process, thereby providing stable traction force during use and improving the orthodontic effect.

[0048] Further optimization, reference Figure 12 As shown, the lowest point of the traction part 12 in the gingival-maxillary direction does not exceed the occlusal plane. In the gingival-maxillary direction ( Figure 1 The lowest point of the traction part 12 in the gingival direction (Y direction) can be the direction of the long axis of the tooth at the corresponding position, or the direction perpendicular to the protrusion direction L of the traction part 12. The fact that the lowest point of the traction part 12 in the gingival direction does not exceed the occlusal plane O ensures that the lowest point of the traction part 12 in the gingival direction does not contact the opposing teeth during occlusion, thus not affecting the normal occlusal relationship of the teeth. Therefore, the lowest point of the traction part 12 in the gingival direction does not contact the opposing teeth during occlusion, thereby reducing occlusal interference that may occur when the traction part 12 is installed. Furthermore, in the embodiments of this application, the lowest and highest points of the traction part 12 are mainly defined as the point on the traction part 12 closest to the gingiva, which is called the lowest point, and the point on the traction part 12 away from the gingiva and adjacent to the opposing teeth, which is called the highest point.

[0049] In some embodiments, reference Figure 13 and Figure 14As shown, the shell-shaped body 1 also includes an extension portion connected to the tooth receiving cavity 11. When worn, the extension portion corresponds to the gingival region, and the traction portion 12 is located on the extension portion, that is, the traction portion 12 is positioned corresponding to the gingival region. Of course, in some other embodiments, the traction portion 12 can be positioned both on the tooth receiving cavity 11 and on the extension portion.

[0050] In some embodiments, reference Figure 15 and Figure 16 As shown, when the traction part 12 is disposed on the extension part, the side surface where the opening structure 121 is located is the first surface 123, and the surface on the traction part 12 opposite to the first surface 123 is the second surface 124. The first surface 123 can be a surface near the tooth, a surface away from the tooth, the mesial surface of the traction part 12, or the distal surface of the traction part 12. When the side surface of the traction part 12 is a cylindrical or frustum-shaped side surface, the first surface 123 is a partial side surface, and the second surface 124 is the remaining partial side surface. The projection of the end of the first surface 123 near the extension part in the traction direction X is the first projection, and the projection of the end of the first surface 123 away from the extension part in the traction direction X is the second projection. The first projection is closer to the second surface 124 than the second projection. See details. Figure 16 As shown, the first projection is point M, and the second projection is point N. Point N is closer to the second surface 124 than point M. This arrangement allows the first surface 123 to tilt towards the extension, thus preventing the traction member from detaching from the traction part 12. This avoids the risk of the traction member detaching from the traction part 12 during use, which would prevent the traction force from being ineffectively applied, and also avoids the risk of the traction member being swallowed by the patient after detachment. In this case, the reinforcing spine 122 is preferably located on the second surface 124 to further improve the deformation resistance of the traction part 12.

[0051] Further preferred options, refer to Figure 17 As shown, the direction in which the first surface 123 extends from the end near the extension to the end away from the extension is the first direction E, and the angle β between the first direction E and the traction direction X is greater than 90° and less than or equal to 150°. This arrangement ensures that the traction member can enter the area formed between the first surface 123 and the extension during assembly, and also ensures that the end of the first surface 123 away from the extension has a certain limiting effect on the traction member during the traction process.

[0052] Further selections will continue to be considered. Figure 17As shown, when the first projection is closer to the second surface 124 than the second projection, the first surface 123 and the second surface 124 are arranged parallel to each other. In one case, the first surface 123 and the second surface 124 are parallel planes. In another case, the first surface 123 and the second surface 124 are parallel curved surfaces. This design ensures that the portion of the traction part 12 connected to the extension part has a larger dimension, preventing deformation of the traction part 12 under the action of traction force during use.

[0053] In other embodiments, the opening structure 121 on the traction part 12 can be generated during the orthodontic appliance manufacturing process by importing the patient's dental model data into the system to generate a dental model for each step. The system places a virtual traction part 12 on each dental model according to the medical treatment plan. The side surface of the virtual traction part 12 has protruding or recessed reinforcing ridges 122. During placement, the bottom surface of the traction part 12 contacts and fuses with the tooth surface or gingiva, and the opening direction is opposite to the traction direction. After obtaining the shape of the orthodontic appliance by 3D printing the dental model and pressing the diaphragm onto the solid dental model, the opening structure 121 is obtained through a cutting process. Preferably, the opening structure 121 is an arc-shaped opening to reduce the problem of stress concentration during traction that could lead to deformation of the traction part 12.

[0054] It should be noted that the above embodiments can be freely combined as needed to form different new implementation schemes without causing contradictions. All implementation schemes formed by such combinations are within the protection scope of this utility model. In order to save space in the application text, they will not be described in detail here.

[0055] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

[0056] Similarly, the above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A dental instrument comprising a shell-like body having a plurality of tooth receiving cavities and a traction portion, characterized in that, The traction part is a cavity structure formed by protruding from the surface of the shell-shaped body in the direction of distal teeth, and the traction part is set at a distance from the edge of the shell-shaped body; the side surface of the traction part is provided with an opening structure for suspending the traction member, and the side surface of the traction part is also provided with a reinforcing ridge formed by a portion of the side surface protruding or recessed, wherein one end of the reinforcing ridge is adjacent to the free end of the traction part, and the other end is set away from the free end of the traction part.

2. The dental instrument according to claim 1, characterized in that, The angle between the long axis of the projection of the reinforcing ridge onto the longitudinal section of the traction part and the convex direction of the traction part is greater than or equal to 0° and less than or equal to 60°.

3. The dental instrument according to claim 1, characterized in that, The height of the opening structure in the protruding direction does not exceed 1 / 2 of the height of the traction part in the protruding direction.

4. The dental instrument according to claim 3, characterized in that, The height of the traction part in the extension direction is between 1.5mm and 2mm.

5. The dental instrument according to claim 3, characterized in that, The highest point of the reinforcing ridge in the convex direction exceeds the opening structure.

6. The dental instrument according to claim 1 or 5, characterized in that, The length of the reinforcing ridge in the convex direction is greater than or equal to half the height of the traction part in the convex direction.

7. The dental instrument according to claim 1, characterized in that, The traction unit is located on at least one of the tooth receiving cavities.

8. The dental instrument according to claim 7, characterized in that, The lowest point of the traction part in the gingival-maxillary direction does not exceed the occlusal plane.

9. The dental instrument according to claim 1, characterized in that, The shell-shaped body also includes an extension portion connected to the tooth receiving cavity. When worn, the extension portion corresponds to the gingival region, wherein the traction portion is located on the extension portion.

10. The dental instrument according to claim 9, characterized in that, The side surface where the opening structure is located is the first surface, and the surface on the traction part that is opposite to the first surface is the second surface. The projection of the end of the first surface near the extension part in the traction direction is the first projection, and the projection of the end of the first surface away from the extension part in the traction direction is the second projection. The first projection is closer to the second surface than the second projection.

11. The dental instrument according to claim 10, characterized in that, The direction in which the first surface extends from the end near the extension to the end away from the extension is the first direction, and the angle between the first direction and the traction direction is greater than 90° and less than or equal to 150°.

12. The dental instrument according to claim 10, characterized in that, The first surface and the second surface are arranged parallel to each other.

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