Orthodontic brackets with customized pad and manufacturing method

Abstract

The disclosed bracket comprises a customized pad with an offset-defined envelope surface and a plurality of retentive features. These retentive features may include protrusions, depressions, or discrete discontinuous structures, while fracture features and removal features are incorporated to facilitate controlled debonding. Such structural designs enhance adhesive contact, improve bonding strength, and enable easier, safer bracket removal at the end of orthodontic treatment.

Description

Attorney Docket No.: 47327.0005.PCTORTHODONTIC BRACKETS WITH CUSTOMIZED PAD AND MANUFACTURING METHODCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C §119(e) to U.S. Provisional Application, U.S.S.N. 63 / 703,955, filed October 05, 2024, which is incorporated herein by reference.FIELD

[0002] The exemplary embodiment(s) of the present invention relates to the field of medical instruments. More specifically, the exemplary embodiment(s) of the present invention relates to processing and fabricating orthodontic apparatus.BACKGROUND

[0003] Many three-dimensional (“3D”) printing technologies can be used to print orthodontic brackets and tubes (orthodontic brackets and tubes are collectively referred to as “orthodontic brackets” hereafter), either non-customized or customized. For noncustomized and customized orthodontic brackets, the pad (or called the base by ISO 27020-2019) to bond the orthodontic bracket to the tooth surface is an important component of the bracket design and function. In general, there arc two types of pads. One is the non-customized pad that is designed by using generalized tooth anatomy over a sample of the population. The other is the customized pad that is designed based on the contour of the patient’s tooth surface. Both non-customized and customized pads can be manufactured by casting, polymer injection molding, metal injection molding, ceramic injection molding, polymer 3D printing,Attorney Docket No.: 47327.0005.PCT metal 3D printing, ceramic 3D printing, etc., with or without the bracket body. If it is without the bracket body, then it will be welded to the bracket body in the process. In general, the non-customized bracket has a non-customized pad unless expressly described differently.

[0004] Because the pad of the non-customized bracket doesn’t fit the tooth anatomy well, the pad will not have good and stable contact with the tooth surface where it is bonded. When the non-customized bracket is directly bonded by doctors, the location and orientation of the bracket and its slot can be off, and the bonding accuracy can be compromised.

[0005] Some doctors try to use lab techniques to make non-customized pads have a function similar to customized pads, which are referred to as “customized-by-dentist pads,” by using dental adhesive to match the pad of the non-customized bracket to the tooth anatomy better. The customizcd-by-dcntist pad is essentially a layer of light-cured resin filled in the gap between the non- customizcd bracket pad and the tooth surface, such that the slot prescription parameters can be expressed more accurately after bonding the bracket to the tooth. In this situation, the slot, bracket body, and the pad are designed and manufactured without customization. The slot abides by the common prescriptions of orthodontic brackets, i.e., MBT, Roth, Damon, etc. This hybrid of a non-customized bracket body and customized pad can be done manually, but cannot be performed consistently with high quality.

[0006] Orthodontic treatment often involves the use of brackets that are bonded to the patient's teeth for an extended period. At the end of the treatment, these brackets need to be removed without damaging the tooth surface. Traditional brackets can be challenging to remove, especially when they are tightly bonded.Attorney Docket No.: 47327.0005.PCTSUMMARY

[0007] To address these issues, the present invention discloses the processes of providing orthodontic brackets with customized pads and / or retentive features, and a manufacturing method thereof. The customized pads may provide a stronger bond between a pad and a patient’s tooth surface. The fracture features are designed to simplify the removal process, reducing the effort required and minimizing the risk of damage to the tooth.

[0008] In a first embodiment, the orthodontic bracket of the present invention comprises a customized pad having a substrate, a plurality of retentive features, and at least one pair of fracture features. The plurality of retentive features may be formed as protrusions or recesses relative to an envelope surface defined by an offset from the patient’s tooth surface. Al least one pair of fracture features is provided on the pad, such as on mesial-distal or occlusal-gingival sides, and is configured to concentrate stress under external force, thereby facilitating controlled cracking and removal of the bracket.

[0009] In a second embodiment, the orthodontic bracket of the present invention further comprises at least one pair of removal features formed on the customized pad. At least one pair of removal features, which may include chamfered recess, is disposed on the mesial-distal sides or the occlusal-gingival sides of the pad. The chamfered recess may have various shapes, including triangular, rectangular, and curved shapes. For example, the chamfered recess may be a triangular recess. These removal features provide localized engagement sites for dental pliers, allowing the practitioner to apply force selectively to initiate debonding while reducing the risk of bracket fragments remaining on lhe tooth.Attorney Docket No.: 47327.0005.PCT

[0010] In a third embodiment, the plurality of retentive features is configured as discrete, discontinuous structures distributed across the substrate surface. Such structures may include island-shaped depressions recessed below the envelope surface or post-like projections extending above the substrate surface, wherein both the recesses and projections are disposed on the bracket side of the envelope surface relative to the tooth side. When the retentive features arc recessed below the envelope surface, the envelope surface is overlapped with the (outer) substrate surface. When the retentive features are post-like projections extending above the substrate surface, the envelope surface is formed by connecting the outer surface of the protruding retentive features and is different from the substrate surface. In certain forms, the projections may further have a T-shaped cross-section. These distributed retentive features create multiple localized adhesive retention sites, thereby enlarging the adhesive-bracket interfacial area and providing multidirectional mechanical interlocking to enhance bonding stability.

[0011] In summary, the disclosed orthodontic bracket of the present invention integrates a customized pad with offset-defined envelope surfaces, retentive features, fracture features, and removal features to address both bonding and debonding challenges. By tailoring the pad to individual tooth anatomy and incorporating retentive structures of varied geometries, the bracket achieves stronger and more reliable adhesive bonding. The addition of fracture and removal features provides predictable stress concentration and controlled debonding paths, reducing enamel damage and improving clinical efficiency. Collectively, these designs enhance bracket stability during treatment while ensuring safe and convenient removal thereafter.

[0012] Additional features and benefits of the exemplary embodimenl(s) of the present invention will become apparent from the detailed description, figures, and claims set forth below.BRIEF DESCRIPTION OF THE DRAWINGSAttorney Docket No.: 47327.0005.PCT

[0013] The exemplary embodiment(s) of the present invention will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only.

[0014] FIG. 1 is a schematic diagram illustrating an envelope surface of the retentive features of the pad in relation to the tooth surface and the corresponding offset in accordance with one embodiment of the present invention.

[0015] FIG. 2 is a schematic diagram illustrating a customized pad with fracture features on mesial and distal sides in accordance with one embodiment of the present invention.

[0016] FIG. 3 is a partial enlarged side view of FIG. 1. illustrating the shape of the retentive features relative to the envelope surface and the substrate in accordance with one embodiment of the present invention.

[0017] FIG. 4 is a schematic diagram illustrating a customized pad with two pairs of fracture features on mesial and distal sides in accordance with one embodiment of the present invention.

[0018] FIG. 5 is a schematic diagram illustrating a customized pad with serrated fracture features on mesial and distal sides in accordance with one embodiment of the present invention.

[0019] FIG. 6 is a diagram illustrating a customized pad with a pair of removal features on the mesial and distal sides in accordance with another embodiment of the present invention.

[0020] FIG. 7 is a schematic diagram illustrating a customized pad with a pair of removal features on the occlusal and gingival sides in accordance with another embodiment of the present invention.Attorney Docket No.: 47327.0005.PCT

[0021] FIG. 8 is a schematic diagram illustrating a customized pad with a pair of removal features on the mesial and distal sides and a pair of fracture features on the occlusal and gingival sides in accordance with another embodiment of the present invention, wherein the retentive features are discrete and comprise island-shaped depressions recessed below the envelope surface.

[0022] FIG. 9 is a schematic diagram illustrating a customized pad with a pair of removal features on the occlusal and gingival sides and a pair of fracture features on the mesial and distal sides in accordance with another embodiment of the present invention, wherein the retentive features arc discrete and comprise post-like projections extending outwardly above the substrate surface.

[0023] FIG. 10 is a partial enlarged side view of FIG. 9, illustrating details of the protruded retentive features configured as discrete post-like or T-shaped projections extending outwardly from the substrate surface.Attorney Docket No.: 47327.0005.PCTDETAILED DESCRIPTION

[0024] Embodiments of the present invention are described herein in the context of a method and / or apparatus for processing and fabricating orthodontic devices.

[0025] The purpose of the following detailed description is to provide an understanding of one or more embodiments of the present invention. Those of ordinary skills in the art will realize that the following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure and / or description.

[0026] hr the interest of clarity, not all of the routine features of the implementations described herein arc shown and described. It will, of course, be understood that in the development of any such actual implementation, numerous implementation-specific decisions may be made in order to achieve the developer’s specific goals, such as compliance with application- and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be understood that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skills in the art having the benefit of embodiment(s) of this disclosure.

[0027] Various embodiments of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all the components of a given apparatus (c.g., device) or method. The same reference indicators will be used throughout the drawings, and the following detailed description will refer to the same or like parts.Attorney Docket No.: 47327.0005.PCT

[0028] The term "envelope surface" is used herein to describe a surface that encompasses the bottom of one or more retentive features (for protruded features) or the bottom surface of the pad (for sunken features). The envelope surface may be generated based on the tooth surface, and the offset after the offset of the tooth surface is determined.

[0029] The term "offset" is used herein to refer to a translation or distance adjustment from the original tooth surface, usually a change to a given physical space. This space may be used to accommodate adhesives, to design specially shaped braces, or to adjust for the correct positioning of braces. In the present invention, when designing a non-customizcd or customized dental bracket, the technician / doclor, via software / design tool, such as a treatment planning software, may determine an offset to generate an envelope surface based on the patient's tooth surface shape. In fact, the surface curvature of the envelope surface that includes the offset is distinguished from that of the original tooth surface contour. As a result, this envelope surface can be used to manufacture a betterfitting orthodontic bracket pad, because the offset providing space for adhesive is taken into consideration to ensure that after adhesive is applied, the brackets adhere securely to the tooth surface and are not affected by stress or positional asymmetry.

[0030] The term “retentive feature” is used herein to refer to a feature or structure designed on an orthodontic appliance to enhance the adhesion or fixation between the appliance and the tooth surface. The retentive features arc formed relative to the envelope surface, such that they may be configured as protrusions extending outwardly from the substrate surface to the envelope surface or as depressions recessed below the envelope surface which is overlapped with the substrate surface in this situation. In the present invention, there are one or more retentive features on the pad; the shapes of one or more retentive features include but not limited to differently shaped protrusions or intrusions, grooves, dimples, sunken, or other tiny structures that provide an extra surfaceAttorney Docket No.: 47327.0005.PCT area, bonding strength, or increased interlock between the pad and tooth surface after bonding, thereby improving the stability and durability of brackets, spacers, or other orthodontic appliances.

[0031] The term “substrate” refers to the bottom portion of the customized pad that excludes the retentive features but is bonded to the tooth surface with retentive features. For the recessed retentive feature, the substrate surface of the pad overlaps with the envelope surface; for the protruded retentive feature, the substrate surface of the pad is the surface where the retentive feature joins the pad. In the embodiment of the protruded retentive feature, the envelope surface is formed by connecting the outer surface of protruded retentive features and is different from the substrate surface.

[0032] The present invention discloses methods and apparatuses relating to three-dimensional (“3D”) printing technologies that can be used to manufacture orthodontic brackets, either non-cuslomized or customized. Common materials used for orthodontic brackets are polymer materials, composite materials, metals, and ceramic materials. Specialized 3D printing materials can be used with different 3D printing technologies to manufacture the orthodontic brackets in specific materials that are designed to provide strength, aesthetics, and biocompatibility for clinical use.

[0033] For the design and function of non-customized and customized orthodontic brackets, the pad (or called the base by ISO 27020-2019) used to bond the orthodontic bracket to the tooth surface is an important component of the bracket. In general, there are two types of pads. One is the non-customizcd pad that is designed by using generalized tooth anatomy over a sample of the population. The other is the customized pad that is designed based on the contour of the patient’ s tooth surface. Both non-customized and customized pads can be manufactured by casting, polymer injection molding, metal injection molding, ceramic injectionAttorney Docket No.: 47327.0005.PCT molding, polymer 3D printing, metal 3D printing, ceramic 3D printing, etc., with or without the bracket body. If it is without the bracket body, then it will be welded to the bracket body.

[0034] In non-customized brackets, the bracket slot design follows a number of prescriptions, such as MBT, Roth, and Damon, etc. each of which defines a set or subset of the parameters listed as follows. Non-customized bracket slot is defined by a series of parameters, a.k.a. in-out, angle of torque, angulation, rotation offset, slot depth, slot height, slot length, which arc designed and built in for all patients’ teeth (the parameters arc defined as in ISO 27020-2019 hereafter). The dimension and structure of the noncustomized bracket body are designed to accommodate the generic anatomy and size of different loolh types, i.e., upper central incisors, upper lateral incisors, upper canines, upper premolars, and upper molars, lower central incisors, lower lateral incisors, lower canines, lower premolars, and lower molars. The pad of the non-customized bracket is not customized to the individual patient’s tooth anatomy. Nevertheless, the pad of the non-customized bracket is designed in generic shapes and sizes for different tooth types, i.e., upper central incisors, upper lateral incisors, upper canines, upper premolars, and upper molars, lower central incisors, lower lateral incisors, lower canines, lower premolars, and lower molars.

[0035] For customized brackets, both the bracket body, including the slot, and the pad arc customized to the treatment plan and the patient's tooth anatomy. The process of designing and manufacturing customized orthodontic brackets starts with the intraoral scanning of a patient's teeth. After the patient's teeth are scanned, the digital file of the scan is imported into a treatment planning software that segments the scanned digital file into individual teeth that can be programmed to move from the initial position to the final position. At the final position, teeth are lined up according to clinical standards accepted by the doctor or dental professional.Attorney Docket No.: 47327.0005.PCT

[0036] The first stage is to customize the bracket body. To begin customizing the bracket body, the treatment planning software will automatically place a set of bracket templates on the teeth. The bracket template is defined by the preset parameters of the bracket body, including the slot, a.k.a. in-out, angle of torque, angulation, rotational offset, slot depth, slot height, slot length, dimensions, and structures of the bracket body. The preset parameters of the bracket body, including the slot for each type of tooth, are different based on the generic size and anatomy of that type of tooth, a.k.a. upper central incisors, upper lateral incisors, upper canines, upper premolars, and upper molars, lower central incisors, lower lateral incisors, lower canines, lower premolars, and lower molars. Then, the treatment planning software will customize the preset parameters of the bracket body including the slot listed above based on the placement of the brackets on the teeth controlled by the doctor and constrained by the archwire shape chosen by the doctor at the final positions of the teeth, which results in all the slots in brackets are lined up along the preformed archwire shape with the archwirc going through the mesial-distal center line of all the slots at the final position of teeth.

[0037] The second stage is to customize the pad. In customizing the pad for both hybrid and customized brackets, not only the anatomy of the patient’s tooth will be taken into account, a.k.a. the contour of the tooth surface patch where the bracket will be bonded, either buccal or lingual, depending on if the bracket is for buccal bonding or lingual bonding, but also the thickness of the dental adhesive that is used to bond the bracket to the tooth. As different denial adhesives have different optimal thicknesses lo achieve the highest bonding strength and different doctors have preferences for applying the dental adhesive, the thickness of the applied dental adhesive will be variable. This variable can be input to the treatment planning software based on the user’s preference or choice of the adhesive. This thickness is important because when it is considered in determining the offset for the envelope surface, the customized pad would have the surface more precisely fit the contour of the patient’s tooth after the dental adhesive isAttorney Docket No.: 47327.0005.PCT applied to produce stronger bonding. The reason includes that the surface curvature of the envelope surface, considering the offset, is distinguished from that of the original tooth surface contour.

[0038] To design a hybrid of a common prescription-based bracket and customized pad, the process starts with the intraoral scanning of a patient's teeth. After the patient's teeth are scanned, the digital file of the scan is imported into a treatment planning software that segments the digital file of the scan into individual teeth that can be programmed to move from the initial position to the final position. At the final position, teeth arc lined up, and the placement of brackets is controlled according to clinical standards accepted by the doctor or dental professional. The bracket slot will follow the prescriptions mentioned above. The pad of the bracket will be customized according to the second stage to customize the bracket.

[0039] In one embodiment of the present invention, as shown in Figs. 1 and 2, the orthodontic bracket 10 of the present invention has a slot 13 oriented along the medial-distal direction. The slot 13 of the bracket 10 in accordance with the present invention is used to guide the archwire; therefore, the shape, depth, diameter, material, and size of the slot 13 described herein can be adjusted according to the cross-sectional shape and diameter of the archwire accommodated in the slot 13. In the practical application of orthodontic treatment, the use of archwircs is usually gradual. In the initial phase, light, flexible nickcl-titanium wires arc used to apply a gentle, continuous force to align teeth and relieve crowding. In the later stages, stiffer archwires, such as rectangular stainless steel archwires, are used to define the shape of the dental arch and guide precise tooth movement. It should be understood that the slot 13 is fixed once the bracket is manufactured. The slot 13 cannot be altered during orthodontic treatment, and any change in slot parameters requires rebonding with a different bracket.Attorney Docket No.: 47327.0005.PCT

[0040] The orthodontic bracket 10 of the present invention has a customized pad 1 1 comprising a substrate 111 , a plurality of retentive features 12, and at least one pair of fracture features 15. Specifically, the retentive features 12 can be generated as shown in Figs. 1 to 3 of protruded features and Figs. 4 and 5 of sunken features. After the placement of the bracket 10 and the offset of the tooth surface arc determined, an envelope surface 14 will be generated based on the tooth surface and the offset. The offset provides a controlled space for the dental adhesive, ensuring reliable bonding between the pad 11 and the tooth surface.

[0041] When customized or hybrid brackets with customized pads arc bonded with an indirect bonding tray, they need to be preloaded into the receiving wells in the indirect bonding tray. The structural design and function of the receiving wells and the indirect bonding tray are to locate the brackets with customized pads accurately on the tooth surface according to the treatment plan. If the customized pad or the bottom of the retentive features 12 has the same surface matching the patient’s tooth surface with the same surface curvature, the fit will be tight and generate pressure that will deflect the indirect bonding tray, which is usually 3D printed in a flexible resin. After the adhesive is applied, the deflection and the pressure will be even greater. This deflection could throw off the slot 13 parameters in the prescription or the customized slot 13. When the customized pad 11 or the bottom of the retentive features 12 is designed and manufactured with the envelope surface 14 that is a function of the tooth surface and the offset, the deflection and pressure can be controlled and tuned to improve bonding accuracy, as shown in Figs. 1 to 10.1. For protruded retentive features 12 shown in Fig. 2 and Fig. 3, the bottom of the retentive features 12 is encompassed by the envelope surface 14. The thickness of the protruded retentive features 12 ranges between 0.01 mm and 1 .0 mm. The cross-sectional shapes of the retentive feature 12 include, but are not limited to, cylinders, bars, or columns. Each retentive feature 12 can have an undercut angle along its thickness or depth. In an exemplary example, shown in Figs. 2 and 3, specifically, the retentive features 12Attorney Docket No.: 47327.0005.PCT are multiple convex strips extending from the mesial-distal direction. Alternatively, the retentive features 12 can also extend from the gingival-occlusal direction. Preferably, in this embodiment, the cross-section of the retention structure 12 is trapezoidal, particularly with the long side facing the patient's tooth surface and the short side facing the substrate 111. In other words, the trapezoidal shaped retention structure has a long side positioned away from the substrate of the customized pad and a short side positioned toward the substrate of the customized pad.

[0042] When the long side of the trapezoid is bonded to the patient's tooth surface via adhesive, the adhesive fills out the undercuts of the retentive features and increases the interlocking between the bracket and tooth surface. Thus, the trapezoidal shape of the retention structure 12 in this embodiment can enhance bonding strength.

[0043] In an exemplary example, shown in Figs. 4 and 5, the retentive features 12 are multiple concave strips extending from the mesial-distal direction. More specifically, retentive features 12 are concave toward the pad 11 side, and remain below the envelope surface 14, thereby increasing the adhesive contact area while maintaining a relatively continuous bonding interface. For sunken retentive features 12. the bottom surface of the pad 11 is encompassed by the envelope surface 14. The depth of the sunken retentive features 12 ranges between 0.01 mm and 1.0 mm. The elongated groove-type retentive features 12 provide linear anchoring of the adhesive, which enhances shear resistance in a preferred orientation.

[0044] The pad 11 further comprises at least one pair of fracture features 15 disposed on the substrate 111 each being formed as a recess or groove that does not penetrate through the thickness of the pad 1 1 . Each fracture feature 15 has sharp corner regions for stress concentration and is configured with a shape including but not limited to a triangular, trapezoidal, or other polygonal crosssection. In this embodiment, the fracture feature has a triangular shape. In an exemplary example, as shown in Fig. 2, the number ofAttorney Docket No.: 47327.0005.PCT fracture features 15 is two. Specifically, there is a pair of fracture features 15 disposed on the mesial and distal sides of the pad 11 . Alternatively, the pair of fracture features 15 is disposed on the gingival and occlusal sides of the pad 11. When the adhesive is applied to the pad 11 before bonding, the operator (the technician / doctor) will avoid smearing adhesive into at least one pair of fracture features 15. At least one pair of fracture features 15 is intentionally left free of adhesive during bonding. After the treatment is finished, the operator will use a dental plier to pinch the fracture features to start cracking the pad and the adhesive. The forces applied to the pair of fracture features 15 are equal and opposite in direction; therefore, there is little impact on the loolh. Il is said that, upon completion of treatment, force applied by a dental plier onto the fracture features introduces stress concentration within the pad and pad-adhesive interface, thereby initiating controlled cracking and facilitating debonding without damaging the tooth enamel. The concentrated stress can exceed the fracture strength of the pad 11 and the pad-adhesive interface. Thereby, the pad 11 will start cracking at the location of the fracture feature, which further delivers stress concentration to propagate the crack through the pad and pad-adhesive interface. Therefore, the pad 11 and adhesive will break apart, and the bracket 10 will debond from the tooth surface. Thus, at least one pair of fracture features 15 can facilitate the removal of the bracket 10 after treatment is finished.

[0045] In an exemplary example, as shown in Fig. 4, the number of fracture features 15 is four, and they are arranged in two pairs on the mesial and distal sides of pad 11, respectively. By distributing more than one pair of fraclure features 15 across the pad 1 1 , stress concentration can be initiated at multiple locations under external force, enabling more predictable and easier bracket removal. This configuration provides two pairs of locations to introduce stress concentration, by which the operator can choose to apply force on one or both pairs to ensure controlled fracture propagation across the pad 11 and pad-adhesive interface while maintaining the integrity of the bracket 10.Attorney Docket No.: 47327.0005.PCT

[0046] In an exemplary example, as shown in Fig. 5, the shape of at least one pair of fracture features 15 is serrated. Specifically, at least one pair of fracture features 15 is multiple and interconnected on the mesial and distal sides. Alternatively, at least one pair of fracture features 15 is multiple and interconnected on the gingival and occlusal sides. The serrated shape formed by the interconnected at least one pair of fracture features 15 provides a number of locations to introduce stress concentration, on which it is easier for the operator to engage the dental tool. Thus, at least one pair of fracture features 15 provides a localized area where dental forceps or small dental tools can apply force to generate cracks at the pad 11 and pad-adhesive interface, thereby reducing the risk of bracket body fragments detaching from the bracket pad 1 1 and ensuring cleaner debonding. The advantages of at least one pair of fracture features 15 in the pad 11 are that the reduction in bonding surface is small, and the integrity of the bracket 10 is not compromised. The stress concentration is only induced at the pad 11 and pad-adhesive interface, where the debonding should occur, rather than the bracket 10.

[0047] In another embodiment, as shown in Figs. 6 and 7, the customized pad 11 further comprises at least one pair of removal features 16. In this embodiment, the shape of each removal feature 16 is a triangular recess that docs not penetrate through the thickness of the pad 11. Again, the triangular recess is only one embodiment of the chamfered recess. Specifically, the number of at least one pair of removal features 16 is even, and they are arranged in pairs. For example, in Fig. 6, the number of removal features 16 is two, and they are arranged on the mesial side and the distal side, respectively. Alternatively, as shown in Fig. 7, the number of removal features 16 is also two, and they are arranged on the gingival side and the occlusal side, respectively. After the treatment is completed, the operator will use a dental plier to apply force to initiate cracks in the pad 11 and the pad-adhesive interface. Since the applied force does not damage the bracket 10, the cracking in the pad-adhesive interface will debond the bracket 10 from the tooth.Attorney Docket No.: 47327.0005.PCT preventing fragments of the bracket 10 from remaining on the tooth. By positioning removal features along different orientations, the practitioner is provided with multiple options for plier engagement depending on the clinical situation, thereby improving flexibility in bracket debonding procedures.

[0048] In another exemplary example, as shown in Figs. 8 and 9, a pair of fracture features 15 and a pair of removal features 16 arc positioned opposite each other. Specifically, as shown in Fig. 8. when the pair of fracture features 15 is positioned on the gingival and occlusal sides, the pair of removal features 16 is positioned on the mesial and distal sides. As shown in Fig. 9, when the paired fracture features 15 are positioned on the mesial and distal sides, the paired removal features 16 are positioned on the gingival and occlusal sides. Regardless of whether the paired removal features 16 are arranged in the mesial-distal direction or the gingival- occlusal direction, the paired removal features 16 provide a localized area where dental forceps or small dental tools can apply force to generate cracks at the pad-adhesive interface. Thus, at least one pair of removal features 16 reduces the risk of fragments of the bracket 10 remaining on the tooth and ensures cleaner debonding. By alternating the positions of at least one pair of fracture features 15 and at least one pair of removal features 16, different fracture initiation sites arc created. This design allows orthodontists to selectively apply debonding forces in multiple directions, further enhancing clinical convenience and reducing the likelihood of enamel damage.

[0049] In the other embodiment, as shown in Figs. 8 to 10, the plurality of retentive features 12 may be provided as a plurality of discrete, discontinuous structures distributed across the substrate 1 1 1. Such structures may take the form of depressions recessed below the envelope 14 (as shown in Fig. 8) or projections extending outwardly above the substrate surface 1 1 1 (as shown in Figs. 9 and 10). In either case, the discrete distribution of these retentive features 12 is multiple point-shaped depressions or multiple point-Attorney Docket No.: 47327.0005.PCT shaped protrusions, creating a plurality of localized adhesive retention sites, thereby increasing the effective interfacial area and providing multi-directional mechanical interlocking between the adhesive and the bracket 10.

[0050] Specifically, in an exemplary example, as shown in Fig. 8, the bracket 10 is provided with a plurality of sunken retentive features 12 configured as discrete, island-shaped depressions formed below the envelope surface 14. These depressions are discontinuous recesses distributed across the surface of the substrate 111, thereby forming a plurality of localized adhesive retention pockets. When adhesive is applied, the adhesive fills into each depression to generate multiple anchoring sites, thereby providing multi-direclional mechanical interlocking and enhancing overall bonding strength. The sunken retentive features 12 increase lhe adhesive contact area relative to a smooth pad surface, thereby improving retention of the bonded bracket.

[0051] In another exemplary example, as shown in Figs. 9 and 10, lhe bracket 10 comprises a plurality of protruded retentive features 12 extending outwardly from the substrate surface 1 11. These retentive features 12 may be configured as post-like or columnar projections distributed across the substrate 111. Specifically, the protruded retentive features 12 may have specialized cross-sectional geometries, such as a T-shaped profile, wherein the transverse portion of the T faces the tooth surface and conforms to the envelope 14. In other words, the transverse portion is positioned away from the substrate. In addition, the vertical portion extends outwardly from the substrate 111. In one embodiment, the vertical portion extends perpendicular from the substrate. This configuration further increases adhesive engagement by allowing lhe adhesive lo first contact the transverse portion and subsequently How downward along both sides of the vertical portion, thereby maximizing the adhesive-bracket interfacial area and interlocking. This shape provides more and multiple interfacial contacts between the adhesive and the plurality of protruded retentive features 12, significantly enhancing the bond strength and stability of the bracket 10 to the tooth surface.Attorney Docket No.: 47327.0005.PCT

[0052] While particular embodiments of the present invention have been shown and described, it will be obvious to those of ordinary skill in the art that, based upon the teachings herein, changes and modifications may be made without departing from this exemplary embodiment(s) of the present invention and its broader aspects. Therefore, the appended claims are intended to encompass within their scope all such changes and modifications as arc within the true spirit and scope of this exemplary embodiment(s) of the present invention.

Claims

Attorney Docket No.: 47327.0005.PCTCLAIMSWhat is claimed is:

1. An orthodontic bracket, comprising: a customized pad comprising a substrate and configured to be bonded to a tooth surface; and a plurality of retentive features is disposed on the substrate, wherein the plurality of retentive features form an envelope surface defined by an offset from the corresponding tooth surface,2. The orthodontic bracket of claim 1 , wherein each retentive feature has a thickness or depth in the range of 0.01 mm to 1.0 mm.

3. The orthodontic bracket of claim 2, wherein the plurality of retentive features comprises protruded structures extending from the substrate surface.

4. The orthodontic bracket of claim 3, wherein the plurality of retentive features comprises elongated convex strips extending in the mesial-distal or the gingival-occlusal direction.

5. The orthodontic bracket of claim 4, wherein each retentive feature comprises a trapezoidal cross-sectional profile, which has a long side positioned away from the substrate of the customized pad and a short side positioned toward the substrate of the customized pad.

6. The orthodontic bracket of claim 2, wherein the plurality of retentive features comprises sunken structures recessed below the envelope surface.Attorney Docket No.: 47327.0005.PCT7. The orthodontic bracket of claim 6, wherein the retentive features comprise elongated concave grooves extending in the mesial-distal or the gingival-occlusal direction.

8. The orthodontic bracket of claim 1, further comprising at least one pair of fracture features formed on the customized pad.

9. The orthodontic bracket of claim 8, wherein at least one pair of fracture features is disposed on the mesial and distal sides or lhe gingival and occlusal sides of the customized pad.

10. The orthodontic bracket of claim 8, wherein at least one pair of fracture features has a sharp comer shape, comprising a triangular, trapezoidal, or other polygonal cross-section.1 1 . The orthodontic bracket of claim 8, wherein at least one pair of fracture features is in a serrated shape.

12. The orthodontic bracket of claim 1, further comprising at least one pair of removal features formed on the customized pad.

13. The orthodontic bracket of claim 12, wherein each removal feature comprises a chamfered recess that docs not penetrate the entire thickness of the customized pad.

14. The orthodontic bracket of claim 13, wherein the chamfered recess is a triangular recess.

15. The orthodontic bracket of claim 13, wherein at least one pair of removal features is arranged on the mesial and distal sides or the occlusal and gingival sides of the customized pad.

16. The orthodontic bracket of claim 1, wherein the retentive features are provided as a plurality of discrete, discontinuous structures distributed across the substrate surface.

17. The orthodontic bracket of claim 16, wherein the retentive features arc arranged in a non-linear, distributed pattern across the substrate.Attorney Docket No.: 47327.0005.PCT18. The orthodontic bracket of claim 17, wherein the retentive features comprise island-shaped depressions recession recessed below the envelope surface to form localized adhesive retention pockets.

19. The orthodontic bracket of claim 16, wherein the retentive features comprise post-like projections extending above the substrate surface.

20. The orthodontic bracket of claim 19, wherein the post-like projections have a T-shaped cross-section, with a transverse portion positioned away from the substrate and a vertical portion extending outwardly from the substrate surface.

21. A method of providing an orthodontic bracket of claim 1 , having a customized pad with retentive features comprising: obtaining intraoral image data of a patient’s teeth by scanning the patient’s teeth, importing scanned data into a treatment planning software, and segmenting the scanned data into individual tooth models; programming tooth movement from an initial position to a final position; and; determining an offset of the patient's tooth surface to generate an envelope surface of retentive features on the customized pad based on the tooth surface and the offset.

22. The method of claim 21, further comprises a step of generating the remainder of the customized pad by offsetting the tooth surface by an additional distance corresponding to the thickness or depth of the retentive features relative to the envelope surface.

23. The method of claim 22, further comprises a step of forming an undercut angle along the thickness or depth of each retentive feature to enhance bonding strength between the orthodontic bracket and the patient’s tooth surface.Attorney Docket No.: 47327.0005.PCT24. The method of claim 22, further comprising positioning at least one pair of fracture features or removal features on mesial-distal or occlusal-gingival sides of the customized pad.

25. The method of claim 22, further comprising inputting an adhesive thickness parameter into the treatment planning software to determine the offset.

26. The method of claim 20, further comprising generating the retentive features as a plurality of discrete, discontinuous structures comprising depressions recessed below or projections extending above the substrate surface.

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