Multiple engagers for orthodontic tooth movement

Abstract

The present disclosure discusses systems and methods for altering the position of teeth in a subject with an aligner. In an embodiment, a method of rotating a tooth includes attaching two engagers to the tooth and creating a force against the tooth, from contact of the aligner with the engagers, to cause rotation of the tooth. Additionally method can also be used for extrusion of a tooth. In an embodiment, a method of extrusion of a tooth includes attaching two engagers to the tooth, on opposing sides of the tooth, and creating a force against the tooth, from contact of the aligner with the engagers, to cause extrusion of the tooth.

Description

MULTIPLE ENGAGERS FOR ORTHODONTIC TOOTH MOVEMENTCross-Reference to Related Application

[0001] This application claims benefit and priority to U.S. Provisional Application No. 63 / 725,013, filed November 26, 2024, entitled “Multiple Engagers for Orthodontic Tooth Movement.” The content of which is incorporated herein by reference in its entiretyField of the Technology

[0002] The present technology relates to dental appliance systems for altering the position of teeth in a subject. More specifically, this technology relates to the use of aligners having multiple engager elements that can be used for enhanced tooth movement.Background

[0003] Orthodontic aligners are appliances intended to make a series of discrete tooth position corrections aimed at aligning the teeth correctly. Aligners are equivalent to having bracket / wire braces for orthodontic treatment, but they have many advantages. For example, aligners are transparent or semi-transparent, comfortable, and removable for cleaning and while eating.

[0004] Some teeth are shaped in a way that can be difficult for an aligner to "grab" onto the tooth and move the tooth into the desired position. Engagers can be used to provide an additional targeted contact point to such teeth. An engager is a small shape of composite material that is commonly placed on the tooth as part of an aligner treatment to assist with certain tooth movements. The engager provides an additional small surface for the aligner to interact with teeth during treatment.

[0005] Engagers are disposed on the outer surface of a tooth. When force is applied to the engager, the force vector applied to the tooth is not always in an optimal direction and thus can cause undesired movement (translation or rotation). Undesired movement of a tooth leads to longer treatment time due, in part, to revisions to the treatment plan to correct the undesired movements.Summary

[0006] The present technology can, in some embodiments, mitigate the problems associated with undesired movement of teeth during treatment by using two engagers positioned on thecrown of a tooth. The use of two engagers on a tooth reduces and / or eliminates undesired movement of the tooth during treatment.

[0007] In one embodiment, a method of rotating a tooth in a subject comprises: attaching a first engager to a buccal surface of a tooth; attaching a second engager to a lingual surface of the same tooth; and placing an aligner on teeth of the subject with the aligner covering the first engager and the second engager. The aligner includes indentations that are shifted in position, with respect to the current position of the tooth, such that pressure areas are created between the aligner and each of the engagers. A first force is applied to the first engager at a first pressure area and a second force is applied to the second engager at a second pressure area to create mesiolingual or distolingual rotation of the tooth. The first engager and / or the second engager can have a cylindrical or truncated conic shape.

[0008] In one embodiment, the first and second engagers, with the aligner, apply a mesiolingual moment (Mml) or a distolingual moment (Mdl) to the tooth that is greater than a mesiodistal moment (Mmd) applied to the tooth. In an embodiment, a ratio of the mesiodistal moment (Mmd) applied to the tooth to the mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth is less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm. In an embodiment, a ratio of the mesiodistal force (Fmd) applied to the tooth to mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth is less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm.

[0009] A method of extruding a tooth of a subject, comprises: attaching a first engager to a buccal surface of a tooth; attaching a second engager to a lingual surface of the same tooth; and placing an aligner on teeth of the subject with the aligner covering the first engager and the second engager. The aligner includes indentations that are shifted in position, with respect to the current position of the tooth, such that pressure areas are created between the aligner and each of the engagers. A first force is applied to the first engager at a first pressure area and a second force is applied to the second engager at a second pressure area to create occlusal movement of the tooth. The first engager and / or the second engager can have a cylindrical or truncated conic shape.

[0010] In an embodiment, the first and second engagers, with the aligner, apply an apical- occlusal force (Fao) to the tooth that such that a ratio of the buccolingual force (Fbl) applied to the tooth to the apical-occlusal force (Fao) applied to the tooth is less than 0.1 N / N, or less than 0.05 N / N, or less than 0.01 N / N. In some embodiments, the buccolingual force (Fbl) appliedto the tooth is less than 1 N. In some embodiments, a ratio of the buccolingual moment (Mbl) applied to the tooth to the apical-occlusal force (Fao) applied to the tooth is less than 0.1 N / N, or less than 0.05 N / N, or less than 0.01 N / N.

[0011] In any of the embodiments described herein, the aligner comprises a first engager void and a second engager void formed in a body of the aligner. During use, the aligner is positioned over the teeth such that the first engager void is positioned over the first engager such that the first engager is contained within the first engager void and the second engager void is positioned over the second engager such that the second engager is contained within the second engager void. The first and / or second engager voids is shifted in position, in relation to the engager contained in the engager void, to create a pressure area between the engager and the aligner.Brief Description of the Drawings

[0012] The technology will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0013] FIG. 1 depicts a schematic diagram of a process of mesiolingual rotation of a lateral incisor.

[0014] FIG. 2 depicts a cross sectional view of the mesiolingual rotation with an aligner and engagers of FIG. 1 viewed from the occlusal surface.

[0015] FIG. 3 depicts a schematic diagram of a process of distolingual rotation of a lateral incisor.

[0016] FIG. 4 depicts a schematic diagram of a process of extrusion of a lateral incisor.

[0017] FIG. 5 depicts a cross sectional view of the extrusion process with an aligner and engagers of FIG. 4 viewed from the occlusal surface.

[0018] FIG. 6 depicts a projection view of a truncated conic engager.

[0019] FIG. 7 depicts a cross-sectional view of an aligner that includes a body having engager voids covering engagers positioned on opposing sides of a tooth.Detailed Description

[0020] The present technology provides a method of moving one or more teeth in a controlled and directed manner to a desired position. The tooth is moved in a way that minimizesunwanted movements. In some instances, two engagers are fastened to a tooth and engage an aligner such that undesired tooth movements are minimized.

[0021] Aligners, generally, can be used to alter the position of one or more teeth within a subject’s mouth. Aligners include a plurality of indentions and are configured to fit tightly on the subject’s teeth. Aligners are maintained on the teeth through an interference fit between the aligner and the teeth. Aligners also include some indentations that do not perfectly match the current shape or position of the patient’s teeth. The mismatch between the aligner and the teeth is predetermined so that the aligner applies pressure to specific teeth. In areas where the shape and position of the aligner does not match the current shape or position of the teeth, pressure areas between the aligner and the teeth are created. The aligner creates forces at the pressure areas that will trigger bone remodeling in the maxilla or mandibula, and, over time, teeth will shift position towards the shape and position dictated by the aligner. The specific force needed trigger bone remodeling results from a combination of specific pressure areas between that tooth and the aligner. The forces at the pressure areas are substantially greater than the pressure applied to the teeth through the interference fit.

[0022] The aligner covers the teeth and, optionally, a portion of the gums when inserted into the mouth. The aligners used in the present technology, are designed to provide forces to the teeth, at pressure areas created by contact of the aligner with the teeth, to direct the teeth to a more desirable configuration. After the subject’s teeth adjust to the new positions dictated by the aligner, the aligner may be replaced with a new aligner having a slightly different configuration which creates pressure areas that maintain forces on the teeth to continue movement of the teeth until the configuration dictated by the new aligner is achieved.

[0023] The aligners described herein cover either the maxillary teeth (top teeth) or the mandibular teeth (bottom teeth). Aligners can be made of any material suitable for dental applications. Preferably, aligners are composed of a clear material, particularly a polymeric clear material. The aligner material can be a unitary material (made, e.g., by a 3D printing process). Alternatively, the aligner material can be composed of multiple layers of one or more polymeric materials. Aligners can cover one or more of the teeth.

[0024] In some instances, an orthodontist or treatment planner may recommend using engagers that are bonded to a subject’s teeth in order to provide specific contact points between the aligner and a particular tooth. Engagers are often formed from a composite material that is bonded to a subject’s tooth in a particular location. Engagers can have different sizes, shapes,and orientations in order to achieve desired forces on a particular tooth. Different types of engagers can be helpful to achieve different kinds of tooth movements. For example, some engager geometries can be used to better translate, rotate or tip particular teeth, while other geometries can be used for extrusion or intrusion of teeth, or to assist in anchoring the aligner more firmly onto the subject’s teeth. Engagers provide targeted contact areas on the teeth which interact with the aligner to create enhanced pressure areas on the teeth to improve movement.

[0025] As used herein the term “midline” refers to imaginary line dividing the left and right sides of the dentition.

[0026] As used herein the term “distal” refers to the direction away from the midline along the arch curvature in each quadrant of a dentition. Each tooth can be described as having a distal surface and, for posterior teeth, a distobuccal (DB) and a distolingual (DL) corner or cusp tip.

[0027] As used herein the term “mesial” refers to the direction toward the midline in a dental arch. Each tooth can be described as having a mesial surface and, for posterior teeth, a mesiobuccal (MB) and a mesiolingual (ML) comer or cusp tip.

[0028] As used herein the term “anterior” refers to the direction toward the front of the head or the lips. The term anterior teeth refers to incisors and canines.

[0029] As used herein the term “posterior” refers to the direction toward the back of an individual's head. The term posterior teeth refers to premolars and molars.

[0030] As used herein the term “buccal” refers to the side of a tooth that is adjacent to (or the direction toward) the inside of the cheek.

[0031] As used herein the term “lingual” refers to the side of a tooth adj acent to (or the direction toward) the tongue (lingua). While formally, the term “lingual” is generally used when referring to teeth in the mandible (lower jaw), it is commonly used as a reference for teeth in either the mandible or the maxilla.

[0032] As used herein the term “apical” refers to the direction toward the root tip(s) or apex(es) of a tooth (the apices). It may also refer to something relating to the roots, such as apical support.

[0033] As used herein the term “occlusal” refers to the direction toward the biting surface of teeth or something relating to this surface, such as the terms occlusal interference or occlusal surface. The term “coronal” is used similarly to refer to the direction toward the crown of atooth (molars), as opposed to apical, which refers to the direction toward the tip(s) of the root(s) or apex(es). It may also refer to something relating to the crown, such as coronal forces.

[0034] As used herein the term “translation” refers to moving the tooth mesiodistal or buccolingual (out-in) so that the position of the tooth within the mouth is changed without rotation of the tooth.

[0035] As used herein the term “extrusion” refers to moving the tooth away from the gums of the mouth (occlusal direction). As used herein the term “intrusion” refers to moving the tooth toward the gums (apical direction).

[0036] As used herein, the phrase “movement of a tooth” refers to any change to the position, exposed height, or orientation of the tooth that is caused by the aligner. The term “movement” therefore encompasses translation, extrusion, intrusion and rotation of the tooth.

[0037] The movement of a tooth by an aligner is determined by the forces acting on the tooth for sufficient time to allow the movement to happen. Tooth movement also requires a free path for the tooth to move into. Avoiding collisions with other teeth‘s roots or crowns play a crucial role as well for a successful single tooth movement. Bone health, height and density are also key variables influencing deeply tooth movement. Finally age and other cofactors such as the patient is a smoker or not, or other pathologies can affect deeply the quality of the expressed movement.

[0038] The forces acting on a tooth by an aligner can be characterized by force vectors and moments with respect to the center of resistance (CRes) of the tooth. The CRes is considered the fundamental reference point for controlled tooth movement. Typically, the CRes is situated at a point located 1 / 3 to ’A of the distance from the alveolar crest to the root apex of the tooth. Force vectors include but are not limited to: mesiodistal force (Fmd); buccolingual force (Fbl); and apical-occlusal force (Fao). Moments include but are not limited to: buccolingual moment (Mbl); mesiodistal moment (Mmd); and mesiolingual / distolingual moment (Mmldl).

[0039] Mesiodistal forces (Fmd) applied to a tooth can translate the tooth toward the midline of the teeth (anteriorly), which is known as the mesial direction, or away from the midline, which is known as the distal direction. Mesiodistal forces can be used to translate a tooth along the gumline such that the tooth is evenly spaced between the adjacent teeth. As used herein, a positive mesiodistal force is used to designate movement in the distal direction. As used herein a negative mesiodistal force is used to designate movement in the mesial direction.

[0040] Buccolingual forces (Fbl) applied to a tooth can move the tooth toward the lips or cheeks (buccal direction) or toward the tongue / palate (lingual direction). Buccolingual forces are used to move a tooth in or out to align the tooth with the position of the adjacent teeth. As used herein a positive buccolingual force moves the tooth in the lingual direction. As used herein a negative buccolingual force moves the tooth in the buccal direction.

[0041] Apical-occlusal forces (Fao) applied to a tooth can move the tooth away from the gums of the mouth (occlusal direction, extrusion) or toward the root or gums of mouth (apical direction). Apical-occlusal forces are used to move a tooth into the gums of the patient or away from the gums As used herein, a positive apical-occlusal force is used to designate movement in the occlusal direction. As used herein a negative apical-occlusal force is used to designate movement in the apical direction.

[0042] Rotational moment can also be applied to alter the position of a tooth. Buccolingual moment (Mbl) refers to a rotational moment applied to a tooth that causes the tooth to rotate around the mesiodistal axis. This type of rotation appears as a forward or backward rotation of the crown, also known as tipping of the crown. Forward rotation of the crown translates the occlusal surface of the tooth toward the lips (buccal crown tipping). Backward rotation of the tooth translates the occlusal surface of the tooth toward the tongue (lingual crown tipping). Buccolingual rotation can be used to align a long axis of the tooth running (i.e., an axis running from the apical end to the occlusal end) with the long axis of the adjacent teeth. As used herein, a positive buccolingual moment is used to designate buccal crown tipping. As used herein a negative buccolingual moment is used to designate lingual crown tipping.

[0043] Mesiodistal moment (Mmd) refers to a rotational moment that causes the tooth to rotate around the buccolingual axis (i.e., an axis extending from the buccal surface to the lingual surface of the tooth) which appears as a sidewise tipping of the tooth. Rotation of the tooth such that the occlusal surface of the tooth moves in the mesial direction is known herein as mesial rotation or mesial crown tipping. Rotation of the tooth such that the occlusal surface of the tooth moves in the distal direction is known as distal rotation or distal crown tipping. Mesiodistal rotation can be used to rotate the tooth such that a long axis of the tooth is substantially perpendicular to the horizontal plane. As used herein, a positive mesiodistal moment is used to designate distal rotation. As used herein a negative mesiodistal moment is used to designate mesial rotation.

[0044] Mesiolingual / distolingual moment (Mmldl) refers to a rotational moment that causes the tooth to rotate around the long axis extending vertically through the tooth. This type of rotation appears as a rotation of the occlusal surface of the tooth. Rotation of the tooth such that the mesial surface rotates towards lingual is known herein as mesiolingual rotation. Rotation of the tooth such that the distal surface of the tooth rotates in lingual direction is known as distolingual rotation. As used herein, a positive mesiolingual / distolingual moment (Mmldl) is used to designate mesiolingual rotation. As used herein a negative mesiolingual / distolingual moment (Mmldl) is used for a distolingual rotation.

[0045] It should be understood that all forces and moments described herein have, as a reference point, the center of resistance (CRes) of the tooth, which is located in the root. Translation and rotation of the tooth is described herein with respect to the CRes.

[0046] Controlling each of the forces and rotations applied to a tooth during treatment is an important factor for an efficient orthodontic correction of the teeth. When engagers are used to reposition teeth during an orthodontic procedure, many of the above-described forces and moments are applied to the teeth simultaneously, leading to some undesired movement of the teeth. Subsequent corrective steps, taken to correct the undesired movements or to continue an underachieved movement towards the target position, prolongs the treatment and can require revision of the treatment plan.

[0047] Tooth rotation is needed when a tooth is derotated around its long axis (apical-occlusal axis) by at least 20 degrees, or at least 10 degrees, or at least 5 degrees. When a subject has a tooth that is in an incorrect rotational position, it is desirable to rotate the tooth back to the proper orientation in the mouth to achieve alignment with the arch curve. Derotation of teeth can occur naturally due to occlusal mismatches or tooth collisions. Improperly oriented teeth can be difficult to correct using an aligner without the use of engagers. To provide the necessary force to rotate the tooth toward an aligned position, engagers can be attached to the teeth to provide a better force application in the desired direction.

[0048] FIG. 1 depicts a schematic diagram of a process of mesiolingual rotation of a right maxillary lateral incisor. Mesiolingual rotation of this incisor appears as a clockwise rotation of the tooth when looking at the tooth from the occlusal surface of the tooth. The mesiolingual rotation of the tooth using an aligner was modeled with: (1) no engager (No Eng); (2) vertical rectangular engager (Vert Rect); (3) horizontal rectangular engager (Hor Rect); (4) beveledextrusion engager (Bev Extr); and (5) double engager (Double). In this example, rotation of the tooth by about three degrees was modeled.

[0049] FIG. 2 depicts a cross sectional view of the mesiolingual rotation with an aligner and engagers depicted in FIG. 1 viewed from the occlusal surface. FIG. 2 shows that the main forces and moments generated by the aligner on the tooth during the mesiolingual rotation with one or two engagers are mesiolingual moment (Mmldl), mesial force (Fmd), and mesial tipping moment (Mmd). Dotted straight and curved arrows in FIG. 2 represent mesial force and mesiolingual rotation. They are referenced to the center of resistance of the tooth, a point placed in the root of the tooth, where the straight dotted arrows stem from. All of these forces and moments have as reference the center of resistance located in the root. Using the double engager design shows substantially lower mesial force and mesial tipping at a larger mesiolingual moment. The forces applied to the engagers and the tooth by the aligner are shown as arrows in the visual representations.

[0050] In the control experiment, distolingual rotation of the tooth was simulated without using an engager (No Eng). As can be seen in FIG. 1, relatively low mesiolingual / distolingual moment (Mmldl) (about 1 Ncm) can be applied to the tooth without use of an engager. Forces and moments that would create unwanted movements of the teeth are also minimized when no engager is used. However, the low rotational force applied to the tooth without an engager makes rotation of the tooth to the desired orientation difficult, if not impossible.

[0051] When a single engager is used, coupled to the buccal surface of the tooth, the mesiolingual / distolingual moment is significantly increased, ranging from 7.59 to 8.78 Ncm. However, use of a single engager creates significant mesial force (lateral movement of the tooth) and mesial moment (sidewise tipping of the tooth), as shown in FIG. 2. Mesial force (depicted as an arrow from right to left) was determined to be 15.6 N for a horizontal rectangular engager. Mesial force was determined to be 20.1 N for a vertical rectangular engager. Furthermore, significant mesiodistal moment (Mmd) is exerted on the tooth when a single engager is used. Mesiodistal moment was determined to be 20.8 Ncm for a vertical rectangular engager. Mesiodistal moment was determined to be 14.9 Ncm for a horizontal rectangular engager. These mesial loadings combine to produce unwanted mesial movement and mesial rotation (tipping) of the crown as the tooth is rotated. The magnitude of the mesial force and mesial movement that is being applied to the tooth will create a need for substantial corrections and / or modifications to the treatment plan.

[0052] The problem of unwanted movements associated with the use of a single engager can be addressed by using two engagers on opposing sides of the tooth. Referring to FIG. 1, the use of two engagers (Double) produces a relatively large mesiolingual / distolingual moment of 12.9 Ncm. Notably, unwanted forces and moments are substantially reduced. This is particularly apparent when looking at the mesial movement and mesial distal moment for a tooth with two engagers. The absolute mesial force and mesiodistal moment, when using two opposed engagers, are less than 1.0 N and 1.0 Ncm, respectively. Distal force was determined to be 0.3 N and mesiodistal moment was determined to be 0.1 Ncm for two opposed engagers. The substantial reduction in mesial force and mesiodistal moment allows the tooth to be rotated into the desired orientation with significantly reduced unwanted movements. The reduction in unwanted movement improves the efficiency of the orthodontic procedure by minimizing the number of steps needed to achieve the desired rotation of the tooth.

[0053] Similar results were seen when distolingual rotation is performed, as shown in FIG. 3. FIG. 3 depicts a schematic diagram of a process of distolingual rotation of a lateral incisor. Distolingual rotation of the right maxillary lateral incisor appears as a rotation of distal surface towards lingual. The distolingual rotation of the tooth using an aligner was modeled with: (1) no engager (No Eng); (2) vertical rectangular engager (Vert Rect); (3) horizontal rectangular engager (Hor Rect); (4) beveled extrusion engager (Bev Extr); (5) distal beveled engager (Bev dl) and (6) double engager (Double). In this example, rotation of the tooth by about three degrees was attempted with no engager, various single engagers, or a double engager.

[0054] As can be seen in FIG. 3, relatively low mesiolingual / distolingual moment (Mmldl) (about 1.4 Ncm) can be applied to the tooth without use of an engager. Using a single engager, coupled to the buccal surface of the tooth increased the mesiolingual / distolingual moment significantly, ranging from 8.0 to 9.0 Ncm. However, as seen during mesiolingual rotation, the use of a single engager creates significant mesial force and mesial moment (tipping). Mesial force was determined to range from 8.8 to 13.2 N, when a single engager is used. Additionally, significant mesiodistal moment (Mmd) is exerted on the tooth when a single engager is used. Mesiodistal moment was determined to range from 7.8 to 13.5 Ncm.

[0055] The problem of unwanted movements associated with the use of a single engager for distolingual rotations can also be addressed by using two engagers on the tooth. Referring to FIG. 3, the use of two engagers (Double) produces a relatively large mesiolingual / distolingual moment of 11.8 Ncm, while unwanted forces and moments are substantially reduced. Forexample, the mesial force and mesiodistal moment are substantially reduced when using two engagers coupled to the buccal and lingual faces of the tooth. Distal force was determined to be 3.7 N while mesiodistal moment was determined to be 3.4 Ncm when using two engagers. This represents a substantial reduction in mesial force and mesiodistal moment allowing the tooth to be rotated into the desired orientation with significantly reduced unwanted movements.

[0056] The use of two engagers on a tooth significantly increased the mesiolingual moment (Mml) or the distolingual moment (Mdl) applied to the tooth while minimizing the mesiodistal moment (Mmd) applied to the tooth. In an aspect of the present technology, the aligner is configured to create pressure on the first engager and create pressure on the second engager to induce mesiolingual rotation of the tooth. The aligner can be designed in a configuration that contacts the tooth and engagers such that lateral forces (a) and (b) are created on the engagers to create mesiolingual rotation of the tooth, as shown in FIG. 2. The aligner can also be designed in a configuration that reverses the lateral forces on the engager, creating distolingual rotation of the tooth. The aligner is further configured to create forces (c) and (d) on the tooth at the side opposite to the lateral forces being applied to the engager by aligner mismatch with the tooth. The combination of lateral forces (a) (b) and side forces (c) and (d) from the aligner provide rotation to the tooth with minimal unwanted movements or rotations.

[0057] The use of two engagers on the surface of the tooth, along with the configuration of the aligner, allow the forces applied to the tooth to be focused on the desired movement of the tooth while minimizing undesired movements. For mesiolingual / distolingual rotations, the engagers and aligner are configured to maximize the mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth, while minimizing other forces and moments applied to the tooth. For example, use of two engagers allows the mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth to be greater than a mesiodistal moment (Mmd) applied to the tooth. The use of two engagers allows a ratio of the mesiodistal moment (Mmd) applied to the tooth to the mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth to be less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm. The use of engagers can also reduce the mesiodistal force (Fmd) applied to the tooth such that the ratio of the mesiodistal force (Fmd) applied to the tooth to mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth is less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm.

[0058] Extrusion of a tooth is another common orthodontic procedure. When using an aligner to perform an extrusion, an engager is typically used. FIG. 4 depicts a schematic diagram of a process of extrusion of a lateral incisor. The extrusion of the tooth using an aligner was modeled with: (1) no engager (No Eng); (2) vertical rectangular engager (Vert Rect); (3) horizontal rectangular engager (Hor Rect); (4) beveled extrusion engager (Bev Extr); (5) distal beveled engager (Bev dl) and (6) double engager (Double). In this experiment, extrusion of the tooth by about 0.2 mm was attempted with no engager, a single engager, or a double engager.

[0059] As shown in FIG. 4, when an engager is not present the apical occlusal force (Fao), the force need to extrude the tooth, is less than 0.1 N.

[0060] Adding an engager to the buccal surface of the tooth allows the aligner to apply a significant apical occlusal force (extrusion force) to the tooth, to pull the tooth into alignment with the adjacent teeth. Adding an engager allows an apical occlusal force to be applied to the tooth from 20.9 N to 32.4 N, depending on the design of the engager. However, as was seen when performing rotations, there are substantial unwanted movements associated with the use of a single engager. The most significant unwanted movements during extrusion with a single engager are buccolingual movement and buccolingual rotation (tipping).

[0061] FIG. 5 depicts a cross sectional view of the extrusion process with an aligner and engagers discussed in FIG. 4 viewed from the occlusal surface. FIG. 5 shows that the main forces applied by the aligner on the tooth during the extrusion process is apical occlusal force (a), buccolingual force (b), and buccolingual moment (c). When a single engager is used, substantial buccolingual force (b) and buccolingual moment (c) is present. The forces applied to the engagers and the tooth by the aligner is shown as arrows in the visual representations. As shown in FIGS. 4 and 5, buccolingual force ranges from 10. O N to 12.0 N. Buccolingual moment ranges from 14.0 Ncm to 18.0 Ncm.

[0062] The problem of unwanted movements associated with the use of a single engager for extrusions can be addressed by using two engagers on opposing sides of the tooth. Referring to FIGS. 4 and 5, the use of two engagers (Double) produces a relatively large apical occlusal force of 37.6 N, while unwanted forces and moments are substantially reduced. For example, the buccolingual force and the buccolingual moment are substantially reduced when using two opposed engagers. Buccolingual force was determined to be 0.77 N while buccolingual moment was determined to be 1.7 Ncm when using two opposed engagers. This represents asubstantial reduction in buccolingual force and buccolingual moment allowing the tooth to be extruded with significantly reduced unwanted movements.

[0063] The use of two engagers on the surface of the tooth, along with the configuration of the aligner, allow the forces applied to the tooth to be focused on the desired extrusive movement of the tooth while minimizing undesired movements. For extrusion, the engagers and aligner are configured to maximize the apical-occlusal force (Fao), while minimizing other forces and moments applied to the tooth. For example, use of two engagers allows the apical-occlusal force applied to the tooth to be greater than a buccolingual force applied to the tooth. The use of two engagers allows a ratio of the buccolingual force (Fbl) applied to the tooth to the apical- occlusal force (Fao) applied to the tooth to be less than 0.1 N / N, or less than 0.05 N / N, or less than 0.01 N / N. Furthermore, the use of two engagers allows the buccolingual force (Fbl) applied to the tooth to be less than 1 N. The use of two engagers can also reduce the buccolingual moment applied to the tooth such that the ratio of the buccolingual moment (Mbl) applied to the tooth to the apical-occlusal force (Fao) applied to the tooth is less than 0.1 N, or less than 0.05 N, or less than N.

[0064] As can be seen in the above discussions, the shape of the engager can have a significant effect on the forces applied to the tooth by the aligner. Referring to FIG. 3, four different shapes of engagers were modeled. Vertically oriented engagers produced large mesiodistal forces and moments (>12.0 N and >13.0 Ncm, respectively). Horizontal engagers exhibit significantly lower mesiodistal forces and moments during rotation (8.0-10.0 N and 7.0-8.0 Ncm, respectively), however these forces are still sufficient to create unwanted movements. In the double engager model, cylindrical and truncated conic engagers appear to be effective at reducing unwanted forces and moments applied to the tooth. FIG. 6 depicts a projection view of a truncated conical engager.

[0065] Cylindrical and truncated conic engagers offer a number of advantages over traditional square and rectangular engagers. One advantage is that the cylindrical or truncated conic surface of the engager allows the engager to be used in any direction. In contrast, typical rectangular and square engagers are limited to specific directions that are oriented with the flat surfaces. Additionally, the conic surface enables gliding of the aligner along the side walls of the engager. This allows a slight unintentional misalignment (depending on the angulation) of the aligner with the engager without significant loss of contact or pressure on the engager.

[0066] FIG. 7 depicts a cross-sectional view of an aligner 100 that includes a body 110 having engager voids 130a, 130b covering engagers 150a, 150b positioned on buccal and lingual sides of a tooth, respectively. The engager voids are positioned to align with the engagers formed on the same surface of a tooth but are also shifted in position, in relation to the engagers 150a, 150b, to create a pressure area between the engager and the aligner. The aligner further includes a plurality of indentions 120 that are configured to receive one or more teeth of the subject (only one tooth indentation is depicted). The thickness of the body 110 of the aligner is increased in regions 145a, proximate to the portion of the body that defines the first engager void 130a. The thickness of the body 110 of the aligner is also increased in regions 145b, proximate to the portion of the body that defines the second engager void 130b. The combination of increased thickness proximate to the sides of the engager voids creates an arcuate surface that extends over both engager voids 130a, 130b. The thickness of the body is increased in regions 145a and 145b such that the exterior labial surfaces of the body 110 are smooth and arcuate over the engager voids. The increased thickness of the body can also increase desired forces on the engagers, increase stability and retention of the aligner, and help resist deformation of the aligner in these critical areas.

[0067] To further control movement of a tooth, the thickness of the aligner material can be varied at contact points with the engager and tooth. In some embodiments, an aligner can be configured to include increased thickness on one side of an engager in order to provide a desired force in a desired direction, and decreased thickness on an opposite side of the same engager in order to decrease resistance to the desired force. For example, if a treatment plan calls for the rotation of a particular tooth, a portion of the aligner located on the side of an engager can have an increased thickness to increase the force pushing against the engager, while a portion of the aligner located on the opposite side of the engager may have a decreased thickness to decrease any forces resisting the desired force against the engager. For example, in FIG. 2, the thickness of the aligner can be increased proximate (a) and (b) to increase the force promoting mesiolingual rotation of the tooth.

[0068] In an illustrative embodiment, the aligners described herein can be formed from biocompatible aligner materials. Examples of aligner materials include polyurethanes (e.g., Isoplast), epoxies, and metals. In an example, the aligner material can be clear or colored to allow for aligners with designs in them instead of a uniformly clear. The formation and use of aligners is generally described in U.S. Pat. Pub. US20120270173A1 by Pumphrey et. al., titled"Aligners for incrementally moving teeth, and methods and apparatus of making and using such aligners”, which is incorporated herein by reference.

[0069] The aligners described herein can be made using 3D printing technology. In an exemplary embodiment, a 3D printing system can be used to make one or more aligners having engager voids with arcuate outer surfaces. A series of aligners can be made which allow incremental movement of the subject’s teeth to the desired positions.

[0070] To create an aligner using a 3D printer, a digital representation of the aligner is obtained. A digital representation of an aligner can be produced by initially scanning the user’ s teeth to create a 3D model of the teeth. Alternatively, a model of the users’ teeth can be made by preparing a polymeric resin impression of the teeth. A 3D digital model can be generated from the polymeric impression directly or by creating a model of the subject’s teeth and scanning the model.

[0071] Once a 3D digital model of the subject’s teeth is obtained, a treatment plan is developed. A treatment plan is a series of steps that are predetermined by the provider to reposition the teeth of the subject into a desired configuration. Each step of the treatment plan corresponds to a specific movement of one or more teeth of the subject by a series of aligners. The series of aligners can be created from the initial 3D digital model of the subject’s teeth. Each aligner in the system is created to have one or more mismatches between the current or projected configurations of the teeth, so that pressure areas are created between the aligner and the teeth to induce movement of the teeth toward the final tooth position as defined by the aligner.

[0072] In an exemplary embodiment, the desired movement of the teeth is broken down into a series of incremental steps designed to gradually move the subject’s teeth from the original position of the teeth, as defined by the 3D image of the subject’s teeth, to a final position of the teeth. The digital representation of the subject’s teeth can be used to generate a series of aligners that can incrementally reposition the teeth of the subject from the original position to the final position. The series of digital models of aligners is determined using a machine / software that runs a program that includes rules that provide the machine / software with a manner of evaluation and decision making. Some rules will define which teeth are best to be moved first, in a certain manner, and if multiple teeth can be moved at the same time with any given aligner in a sequence of aligners. The machine / software will perform assessments of the original teeth positions versus final teeth positions and perform calculations of whatmovement(s) are logically next in the sequence of aligners based on governing rules and parameters that serve as guidance for achieving optimally arranged teeth. In some implementations, identifying an arrangement of the second teeth alignment based on the first teeth alignment can be provided as an input performed manually by a provider. In this case, the number of iterative forces or movements required to cause the arrangement of the second teeth alignment can be determined based on the manually determined arrangement of the second teeth alignment.

[0073] Digital models of aligners can be created by using design software to create offsets (mismatches) between the teeth and the aligner for each of aligners in the series. The digital models can be designed, trimmed, smoothed, and modified using the design software.

[0074] In a 3D printing method, printing instructions for printing each aligner are determined from the digital models of the aligner created using the design software. In an exemplary embodiment, the printing instructions can include an ordering or sequence and timing of each additive manufacturing layer using a particular material within the alignment structure. In an exemplary embodiment, the printing instructions can be configured for a respective printer's capabilities to print with multiple materials, to resolve 3D objects into discrete volumetric pixels (“voxels”). Additionally, the printing instructions can provide for the method of additively manufacturing different materials (resins) at the correct location in such a way that the intended shape can be constructed with the designed features that are calculated for the aligner to accomplish predetermined movements of one or more teeth. In an example, the printing instructions can be configured to print on an additive manufacturing printer such as a Polyjet printer from Stratasys, Ltd. (Billerica, MA) Polymeric 3D printers that can be used to form aligners include, but are not limited to, fused deposition modeling (FDM) printers, stereolithography (SLA) printers, and selective laser sintering (SLS) printers.

[0075] Further details for using 3D printing technology to form aligners can be found in U.S. Patent Application Publication No. 2020 / 0383754, which is incorporated herein by reference.

[0076] Specific embodiments and methods of aligners and engagers to perform specific movements of teeth have been described herein. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the disclosure. Moreover, in interpreting thedisclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

Claims

CLAIMSWhat is claimed is:

1. A method of rotating one or more teeth of a subject, comprising: attaching a first engager to a buccal surface of a tooth; attaching a second engager to a lingual surface of the tooth; and placing an aligner on the teeth of the subject with the aligner covering the first engager and the second engager, wherein the aligner includes indentations that are shifted in position, with respect to the current position of the tooth, such that a first pressure area is created between the aligner and the first engager, and a second pressure area is created between the aligner and the second engager; wherein a first force created by the aligner contacting the first engager at the first pressure area and, a second force created by the aligner contacting the first engager at the second pressure area create mesiolingual or distolingual rotation of the tooth.

2. The method of claim 1, wherein the first engager and / or the second engager have a cylindrical and / or truncated conic surface.

3. The method of claim 1 or 2, wherein the first force and the second force create mesiolingual rotation of the tooth.

4. The method of claim 1 or 2, wherein the first force and the second force create distolingual rotation of the tooth.

5. The method of any one of claims 1-4, wherein a mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth by the aligner is greater than a mesiodistal moment (Mmd) applied to the tooth.

6. The method of any one of claims 1-5, wherein a ratio of a mesiodistal moment (Mmd) applied to the tooth by the aligner to a mesiolingual moment (Mml) or a distolingual moment (Mdl) applied to the tooth by the aligner is less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm.

7. The method of any one of claims 1-6, wherein a ratio of a mesiodistal force (Fmd) applied to the tooth by the aligner to a mesiolingual moment (Mml) or a distolingual moment(Mdl) applied to the tooth by the aligner is less than 0.1 Ncm, or less than 0.05 Ncm, or less than 0.01 Ncm.

8. The method of any one of claims 1-7, wherein the aligner comprises a first engager void and a second engager void formed in a body of the aligner, wherein the method further comprises: positioning the aligner over the teeth such that the first engager void is positioned over the first engager such that the first engager is contained within the first engager void and the second engager void is positioned over the second engager such that the second engager is contained within the second engager void; wherein at least one of the first and / or second engager voids are shifted in position, in relation to the first and / or second engager, to create a pressure area between the engager(s) and the aligner.

9. The method of any one of claims 1-8, wherein the aligner creates a force to the first engager that is opposite to a force applied to the second engager to cause rotation of the tooth.

10. The method of claim 9, wherein the aligner creates a force against the tooth in a location adjacent to the first engager and creates a force against the tooth in a location adjacent to the second engager.

11. A method of extruding one or more teeth of a subject, comprising: attaching a first engager to a buccal surface of a tooth; attaching a second engager to a lingual surface of the tooth; and placing an aligner on the teeth of the subject with the aligner covering the first engager and the second engager, wherein the aligner includes indentations that are shifted in position, with respect to the current position of the tooth, such that a first pressure area is created between the aligner and the first engager, and a second pressure area is created between the aligner and the second engager; wherein a first force created by the aligner contacting the first engager at the first pressure area and, a second force created by the aligner contacting the first engager at the second pressure area create occlusal movement of the tooth.

12. The method of claim 11, wherein the first engager and / or the second engager have a cylindrical and / or truncated conic surface.

13. The method of claim 11 or 12, wherein a ratio of a buccolingual force (Fbl) applied to the tooth by the aligner to an apical-occlusal force (Fao) applied to the tooth by the aligner is less than 0.1 N / N, or less than 0.05 N / N, or less than 0.01 N / N.

14. The method of any one of claims 11-13, wherein a buccolingual force (Fbl) applied to the tooth by the aligner is less than 1 N.

15. The method of any one of claims 11-13, wherein a ratio of the buccolingual moment (Mbl) applied to the tooth by the aligner to an apical-occlusal force (Fao) applied to the tooth by the aligner is less than 0. IN, or less than 0.05 N, or less than 0.01 N.

16. The method of any one of claims 11-15, wherein the aligner comprises a first engager void and a second engager void formed in a body of the aligner, wherein the method further comprises: positioning the aligner over the teeth such that the first engager void is positioned over the first engager such that the first engager is contained within the first engager void and the second engager void is positioned over the second engager such that the second engager is contained within the second engager void; wherein at least one of the first and / or second engager voids are shifted in position, in relation to the first and / or second engager, to create a pressure area between the engager(s) and the aligner.

Images