Improved Crown Structure

Abstract

To provide an improved crown structure which has high discharge efficiency, allows visual confirmation of the adhesive filling state, ensures the structural strength of the crown, prevents the accumulation of food residues and suppresses intraoral infection, does not require the re-removal of a sealing member after surgery, is adaptable to various tooth positions such as anterior teeth, premolars and molars, and can improve the effectiveness and safety of dental prostheses. [Solution] This invention relates to an improved crown structure in the field of dental prosthetics, and includes a crown body 1 that conforms to the shape of an abutment tooth. The crown body is formed with drain holes that penetrate from the bonding surface 3 to the outer surface 4, and the drain holes have a gradually changing diameter structure. The drain holes have a guide groove on their inner periphery, a conical flared opening on the bonding surface side, and an annular reinforcing rib on the outer surface side. The crown also includes a biodegradable sealing member.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to the field of dental prosthetics, and more particularly to an improved crown structure. [Background technology]

[0002] In clinical dental prosthetics, crown bonding is an important process for ensuring the stability and long-term effectiveness of the restoration. With the spread of digital technology, crown fabrication is shifting from traditional casting and porcelain-fused-together techniques to high-precision technologies such as CAD / CAM milling and 3D printing. However, significant shortcomings still exist in core design (especially the structure that allows cement and air to escape) to ensure the evacuation of cement and air. Specifically, the following problems have been identified: (1) Malocclusion due to lack of evacuation foramen Conventional crowns often do not have dedicated drainage holes, which means that excess cement cannot be expelled during bonding, resulting in problems such as the crown not fully seating and high occlusion. Furthermore, if trapped air remains between the crown and the abutment tooth, it hinders adhesion and requires the surgeon to repeatedly adjust (polish) the restoration, which can extend the consultation time and damage the crown surface, reducing its strength. (2) Difficulty in determining the state of cement filling Because there are no visible signs of cement being expelled, the surgeon cannot accurately determine whether the cement has filled the gap between the crown and the abutment tooth. If there is insufficient cement, an internal cavity will form, leading to loosening or loss of the crown. On the other hand, if there is too much cement, it will cause the malocclusion mentioned above. Clinical procedures depend on experience, and there is a small margin of error. (3) Marginal microleakage and periodontal risks High occlusion and air retention can lead to poor dental contact at the crown margin, allowing bacteria to grow in tiny gaps and causing secondary caries. In addition, if excess cement spills over from the crown margin and remains below the neck, it can be difficult to remove and can irritate the gums over the long term, potentially causing gingivitis or periodontitis. (4) Limitations of existing improvement plans There have been attempts to create drainage holes in the crown, but there are still some roughness in the design, such as the fact that the position is arbitrary and prone to fracture, the hole diameter is uniform and there is high drainage resistance, which causes air and cement to remain inside the hole, the strength around the hole is insufficient, and there is no sealing structure, so food residue can get into the hole after surgery, which can easily cause an unpleasant odor or infection in the mouth. In view of the above, there is a need for a drainage hole design that combines efficient drainage performance, structural strength, clinical practicality, and postoperative safety. Summary of the Invention

[0003] The present invention aims to provide an improved crown structure to solve the above problems. To achieve the above objective, the present invention adopts the following technical solutions.

[0004] The improved crown structure of the present invention includes a crown body that conforms to the shape of the abutment tooth, and the crown body has at least one drain hole extending therethrough, the drain hole extending through the bonding surface and the outer surface of the crown body. The discharge holes have a structure in which the hole diameter gradually changes from the adhesive surface side to the outer surface side, with the adhesive surface side hole diameter being D1 and the outer surface side hole diameter being D2, where D1>D2. The discharge hole is aligned with the insertion path direction of the crown, with a tolerance of 10° or less.

[0005] Preferably, in the case of a crown for an anterior tooth, the discharge hole is provided in the middle part of the lingual surface recess of the crown body near the incisal edge, and is positioned to avoid the force-receiving line of the incisal edge. The outer surface side hole diameter D2 of the front teeth is 0.5 mm, and the adhesive surface side hole diameter D1 is 0.6 to 0.7 mm. The axis of the discharge hole of the anterior tooth is parallel to the longitudinal direction of the crown body, with a tolerance of 5° or less. Preferably, in the case of a crown for a premolar, the discharge hole is provided in the lingual occlusal cavity of the buccal cusp, and is at a horizontal distance of 1.5 mm or more from the apex of the buccal cusp. The D2 of the premolar is set to 0.5 mm, and the D1 is set to 0.6 to 0.7 mm. The axis of the discharge hole forms an angle of 40 to 50° with respect to the longitudinal direction of the tooth body, and is positioned facing upward on the tongue side, avoiding the occlusal force receiving region. Preferably, in the case of a crown for a molar, the discharge hole is provided in the central fossa or in the area near the central fossa on the occlusal surface, and is spaced 2.0 mm or more away from both the buccal and lingual functional cusps. D2 in the molars is set to 1.0 mm, and D1 is set to 1.1 to 1.2 mm. The axis of the discharge hole of the molar coincides with the direction of the insertion path. The outlet end of the discharge hole is located in the non-functioning cusp region of the occlusal surface, and is formed so as to face the buccal non-functioning cusp in the maxillary molar and the lingual non-functioning cusp in the mandibular molar. Preferably, the inner peripheral wall of the discharge hole is provided with three to four flow guide grooves at equal intervals along the axial direction, each with a width of 0.10 to 0.15 mm and a depth of 0.08 to 0.12 mm, and both ends of the flow guide groove extend to the connecting surface end and outer surface end of the discharge hole. Preferably, a conical flared opening is formed at the entrance of the discharge hole on the adhesive surface side, with the conical flared opening having a cone apex angle of 60 to 90°, a maximum diameter of the flared opening being 0.2 to 0.3 mm larger than D1, and a depth of 0.3 to 0.5 mm. Preferably, an annular reinforcing rib is provided at the outlet of the discharge hole on the outer surface side of the crown body, and the reinforcing rib is made of the same material as the crown body. The width of the reinforcing rib is 0.3 to 0.5 mm, the amount of protrusion from the outer surface is 0.1 to 0.2 mm, and the inner diameter is equal to D2 and is 0.6 to 1.0 mm larger than the inner diameter. Preferably, the crown body is provided with a biodegradable sealing member, which is made of a sealing plug that fits over the drainage hole and is made of polycaprolactone (PCL) or polylactic acid (PLA). The sealing plug is composed of a head, a middle section, and a tail section, and the head section has a locking structure and a maximum diameter that conforms to D1. The middle section has a columnar step that conforms to D2, and the tail section has a disk-shaped positioning section that abuts against the annular reinforcing rib, and the diameter of the disk-shaped positioning section matches the outer diameter of the reinforcing rib. The overall length of the sealing plug is equal to the axial depth of the discharge hole, and the tail section is configured to be flush with the outer surface of the crown. Preferably, one or two fine ventilation grooves are provided on the outer peripheral surface of the sealing plug along the axial direction, with a width of 0.05 to 0.08 mm and a depth of 0.03 to 0.05 mm, and are used to exhaust trace gas remaining in the exhaust hole at the initial stage of adhesion. Preferably, the crown body is made of zirconia, glass ceramics, or a resin-based composite material, and the drain holes are integrally formed with the crown body by digital cutting or three-dimensional printing.

[0006] The advantages of this invention are as follows: 1.Improved discharge efficiency The combination of a gradually changing hole diameter structure, an inner peripheral guide groove, and a conical flared opening effectively reduces the resistance to the discharge of air and excess cement, preventing discharge interruptions. The steady overflow of cement from the discharge hole allows visual confirmation of the completion of filling, reducing the reliance on the surgeon's experience. 2. Improved strength of crown structure The annular reinforcing rib on the outer surface improves the pressure resistance around the discharge hole, preventing hole edge damage during occlusal load. In addition, by moving the discharge hole away from the functional cusp force-receiving area, the effect on the mechanical behavior of the entire crown can be reduced. 3. Postoperative safety and convenience The biodegradable sealing element automatically decomposes after the cement hardens, eliminating the need for a second visit for removal. Before decomposition, it prevents food residue from entering the oral cavity, suppressing unpleasant odors and infections. The sealing plug tail is flush with the outer surface of the crown, so it does not affect occlusion or wearing comfort. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of an improved crown structure according to a first embodiment. [Figure 2] FIG. 2 is a schematic structural diagram of an improved crown structure according to the first embodiment. [Figure 3] FIG. 3 is an enlarged view of part A in FIG. 1 in the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of the improved crown structure according to the first embodiment, in a state where a sealing plug is not attached. [Figure 5] FIG. 5 is an enlarged view of part B in FIG. [Figure 6] FIG. 6 is a structural diagram of the sealing plug in the first embodiment. [Figure 7] FIG. 7 is a schematic structural diagram of the crown body in the first embodiment. [Figure 8] FIG. 8 is a schematic structural diagram of the crown body in the second embodiment. [Figure 9] FIG. 9 is a schematic structural diagram of the crown body in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The technical means in the embodiments of the present invention will be described clearly and completely below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the accompanying drawings can be arranged and designed in various different configurations. In describing the embodiments of the present invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and other positional relationships are based on the orientations or positional relationships shown in the drawings or on the customary placement of the product of the present invention when in use. This is intended to facilitate and simplify the description of the present invention, and does not imply that devices or components must have a specific orientation, and therefore should not be understood as a limitation on the present invention. Furthermore, the terms "first," "second," "third," and the like are used for distinction purposes only, and do not imply relative importance. Additionally, the terms "horizontal," "vertical," "pendant," etc. do not require that a part be absolutely horizontal, vertical, or pendant, but may be slightly tilted. For example, "horizontal" simply refers to a more horizontal direction than "vertical," and does not necessarily have to be perfectly horizontal, but may be slightly tilted. In describing embodiments of the present invention, "plurality" refers to at least two. In describing the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "installation," "mounting," "connection," and "coupling" should be understood in a broad sense. For example, they may refer to a fixed connection, a detachable connection, or an integral connection. They may also refer to a mechanical connection or an electrical connection. They may also refer to a direct connection, an indirect connection via an intermediate medium, or an internal connection between two components. Those of ordinary skill in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances. The following provides a detailed introduction to the present invention based on specific examples for a better understanding, but the following examples do not limit the scope of protection of the present invention.

[0009] Embodiment As shown in FIGS. 1 to 7, the improved crown structure includes a crown body 1 that matches the shape of an abutment tooth 6 . (1) Basic structure of the crown body 1 and the discharge hole 2 The crown body 1 is a prosthetic body that fits the shape of the abutment tooth 6, and is made of known materials for dental prosthetics, such as zirconia porcelain or glass ceramics. It is manufactured using precision molding using CAD / CAM cutting or three-dimensional printing technology, ensuring a high degree of compatibility (fit) with the abutment tooth 6. The discharge holes 2 are formed through the bonding surface 3 (inner surface, i.e., the surface that bonds to the abutment tooth 6) and the outer surface 4 (occlusal surface or lingual / palatal surface) of the crown body 1. These discharge holes 2 function as dedicated passages for the discharge of air and excess cement. The position, diameter, and direction of the discharge holes are precisely designed according to the type of tooth, and the design principles are "avoiding force-receiving areas," "aligning with the insertion path," and "easy discharge."

[0010] (2) Structural improvement of the discharge hole The discharge hole 2 is subjected to the following structural optimization in order to reduce discharge resistance, improve the hole periphery strength, and eliminate discharge blind spots. (a) Gradually changing pore size structure The discharge hole 2 has a gradually changing hole diameter structure with a larger diameter at the entrance and a smaller diameter at the exit, and the hole diameter D1 on the adhesive surface 3 side is set larger than the hole diameter D2 on the outer surface 4 side. Here, D1-D2 = 0.1 to 0.2 mm. With this structure, 1) The large pore size on the adhesive surface 3 expands the collection area, allowing air and cement inside the crown to be collected quickly. 2) The small diameter of the holes on the outer surface 4 reduces the effect on the shape of the outer surface (especially the occlusal surface), prevents food from getting caught, and reduces the decrease in strength of the entire crown due to the holes. (b) Inner circumference guide groove 21 The inner peripheral wall of the discharge hole 2 has three to four guide grooves 21 (width 0.10 to 0.15 mm, depth 0.08 to 0.12 mm) evenly spaced along the axial direction. The inner walls of conventional holes with a fixed diameter are smooth, and cement (especially high-viscosity cement) can form a liquid film on the inner wall, hindering the discharge of gas. However, the structure of this guide groove 21 creates a gas passage, allowing air to be discharged preferentially. Furthermore, because the cement is guided along the grooves, discharge resistance is significantly reduced and discharge interruptions can be prevented. (c) Conical flared opening 22 on the adhesive surface 3 side A conical flared opening 22 is formed at the entrance of the discharge hole 2 on the adhesive surface 3 side. The cone apex angle is 60-90°, the maximum diameter is 0.2-0.3 mm larger than D1, and the depth is 0.3-0.5 mm. This flared opening forms a collection chamber and covers the minute recesses on the inner surface of the crown, preventing the formation of blind spots for air and cement discharge near the hole opening and ensuring complete discharge. At the same time, the flared opening reduces the risk of blockage due to cement accumulation at the hole opening. (d) Annular reinforcing rib on outer surface 4 An annular reinforcing rib 23 is provided integrally with the crown body 1 at the outlet of the discharge hole 2 on the outer surface 4 side. The rib width is 0.3 to 0.5 mm and its height is 0.1 to 0.2 mm. The formation of the discharge hole 2 causes loss of material in the area around the hole, which makes stress concentration more likely to occur when a load is applied, particularly on the occlusal surface, and the hole edge is more likely to break (crack). Therefore, the annular reinforcing rib 23 increases the load-bearing area and disperses stress, improving the structural strength of the area around the hole and preventing damage to the crown under normal occlusal loads.

[0011] (3) Biodegradable sealing material To prevent food residue from entering the drainage hole 2 after surgery, a biodegradable sealing member (sealing plug 5) is provided. The sealing plug 5 is made of polycaprolactone (PCL) or polylactic acid (PLA), both of which gradually decompose in the moist environment of the oral cavity. The decomposition products are carbon dioxide and water, which do not irritate the oral mucosa. The decomposition period is set to approximately one to three months. The reason for this period is that the cement completely hardens about one month after the crown is bonded, and the "excretion function" of the discharge hole 2 is already complete. Even if the decomposition of the sealing plug 5 progresses from this point on, it will not affect the initial discharge function. The sealing plug 5 is composed of a head (locking structure 51), a middle section (columnar step 52), and a tail section (disk-shaped positioning portion 53). The head locking structure is locked into the conical flared opening 22 to prevent it from falling off. The middle columnar step 52 adapts to the gradually changing hole diameter to ensure a tight seal. The tail section's disk-shaped positioning portion 53 abuts against the annular reinforcing rib 23 and is flush with the crown outer surface 4, preventing any impact on occlusion or abrasion of the oral mucosa. Furthermore, the columnar step 52 has one or two fine ventilation grooves 54, which release any traces of gas remaining in the discharge hole 2 during the initial stage of adhesion, preventing the sealing plug from loosening due to gas expansion.

[0012] Example 1 (in the case of a molar (mandibular first molar as an example), shown in Figures 1 to 7) The material of the crown body 1 is zirconia porcelain. The occlusal surface is formed with a mesial buccal cusp, a distal buccal cusp, a mesial lingual cusp, and a distal lingual cusp, with the lingual cusp being the functional cusp. The specifications of the discharge hole 2 are as follows: Location: Lingual side of the central fossa on the occlusal surface, 1.5 mm from the mesial cusp and 1.8 mm from the distal cusp. Hole diameter: D1 = 1.2 mm (adhesive surface 3), D2 = 1.0 mm (outer surface 4). Gradual change length = 4.0 mm. Direction: The axis is aligned with the insertion path (tolerance is 8° or less) and is set to face the lingual non-functional cusp area. Auxiliary structure: Four guide grooves 21 (width 0.15 mm, depth 0.12 mm) are provided on the inner circumference, a conical flared opening 22 (cone apex angle 90°, maximum diameter 1.4 mm, depth 0.5 mm) is formed on the adhesive surface 3 side, and a ring-shaped reinforcing rib 23 (width 0.5 mm, height 0.2 mm) is provided on the outer surface 4 side. The structure of the biodegradable sealing member is as follows. The sealing plug 5 is made of PCL (degradation period: 3 months), with a head locking structure having a diameter of 1.2 mm, a central columnar section 52 having a diameter of 1.0 mm, a tail disk having a diameter of 1.5 mm, and a total length of 4.0 mm. The columnar section 52 has two ventilation microgrooves 54 (width: 0.08 mm, depth: 0.05 mm).

[0013] Example 2 (in the case of anterior teeth (upper central incisors as an example), as shown in Figure 8) The crown body 1 is made of zirconia and is fitted to the abutment tooth 6 by CAD design, and the shape of the lingual surface cavity conforms to anatomical features. The specifications of the discharge hole 2 are as follows: Location: The middle of the proximal third of the lingual fossa, 2.0 mm from the incisal edge and 1.5 mm from the lingual border. Hole diameter: D1 = 0.6 mm (adhesion surface 3 side), D2 = 0.5 mm (outer surface 4 side). Gradual change length (axial depth of discharge hole 2) = 2.5 mm. Direction: The axis is parallel to the longitudinal direction of the crown body (tolerance is 5° or less). Auxiliary structure: Three guide grooves 21 (width 0.10 mm, depth 0.08 mm) are provided on the inner circumference, a conical flared opening 22 (cone apex angle 80°, maximum diameter 0.8 mm, depth 0.3 mm) is formed on the adhesive surface 3 side, and a ring-shaped reinforcing rib 23 (width 0.3 mm, height 0.1 mm) is provided on the outer surface 4 side. The structure of the biodegradable sealing member is as follows. The sealing plug 5 is made of PCL (degradation period: 2 months), with a head locking structure diameter of 0.6 mm, a central columnar section 52 diameter of 0.5 mm, a tail disc diameter of 0.9 mm (matching the outer diameter of the reinforcing rib), and a total length of 2.5 mm. The columnar section 52 has one ventilation microgroove 54 (width: 0.05 mm, depth: 0.03 mm).

[0014] Example 3 (In the case of a premolar (using the maxillary first premolar as an example), as shown in Figure 9) The crown body 1 is made of glass ceramics, and a buccal cusp and a lingual cusp are formed on the occlusal surface, with the buccal cusp being the functional cusp. The specifications of the discharge hole 2 are as follows: Location: Lingual occlusal fossa of the buccal cusp, 1.8 mm from the apex of the buccal cusp, 2.0 mm from the apex of the lingual cusp. Hole diameter: D1=0.7mm (adhesive surface 3 side), D2=0.5mm (outer surface 4 side). Gradual change length = 3.0mm. Direction: The axis forms a 45° angle with the longitudinal direction of the tooth body and is directed toward the non-functional cusp area on the upper lingual side, avoiding the buccal force-receiving area. Auxiliary structure: Four guide grooves 21 (width 0.12 mm, depth 0.10 mm) are provided on the inner circumference, a conical flared opening 22 (cone apex angle 70°, maximum diameter 0.9 mm, depth 0.4 mm) is formed on the adhesive surface 3 side, and a ring-shaped reinforcing rib 23 (width 0.4 mm, height 0.15 mm) is provided on the outer surface 4 side. The structure of the biodegradable sealing member is as follows. The sealing plug 5 is made of PLA (decomposition period: 1.5 months), with a head diameter of 0.7 mm, a central columnar section 52 diameter of 0.5 mm, a tail disk diameter of 1.1 mm, and a total length of 3.0 mm. The columnar section 52 has two ventilation microgrooves 54 (width 0.06 mm, depth 0.04 mm).

[0015] Although the specific embodiments of the present invention have been described in detail above, they are merely examples, and the present invention is not equivalent to the above specific embodiments. For those skilled in the art, any equivalent modifications or replacements of the present invention are within the scope of the present invention. Therefore, all equivalent modifications and changes made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. [Explanation of symbols]

[0016] 1 Crown body 2 drain hole 21 Guide groove 22 Conical widening 23 Annular reinforcing rib 3 Adhesive surface 4 Outer surface 5 Sealing plug 51 Locking structure 52 columnar steps 53 Disc-shaped positioning part 54 Micro-ventilation grooves 6 Abutment teeth

Claims

1. An improved crown structure including a crown body (1) adapted to the shape of an abutment tooth (6), At least one discharge hole (2) is provided through the crown body (1), and the discharge hole (2) is formed through the bonding surface (3) and the outer surface of the crown body (1); The discharge hole (2) has a structure in which the hole diameter gradually changes from the adhesive surface (3) side to the outer surface (4) side, the adhesive surface (3) side hole diameter is D1, the outer surface (4) side hole diameter is D2, and D1 > D2; The discharge hole (2) is aligned with the insertion path direction of the crown, with a tolerance of 10° or less. An improved crown structure featuring:

2. In the case of a crown for an anterior tooth, the discharge hole (2) is provided in the middle part of the lingual surface recess of the crown body (1) near the incisal edge, and is positioned to avoid the force-receiving line of the incisal edge; The diameter D2 of the outer surface (4) of the front tooth is 0.5 mm, and the diameter D1 of the adhesive surface (3) of the front tooth is 0.6 to 0.7 mm. The axis of the discharge hole (2) of the front tooth is parallel to the longitudinal direction of the crown body (1), and the tolerance is 5° or less.

2. The improved crown structure of claim 1, wherein:

3. In the case of a crown for a premolar, the discharge hole (2) is provided in the lingual occlusal cavity of the buccal cusp, and the horizontal distance from the apex of the buccal cusp is 1.5 mm or more; The D2 of the premolar is 0.5 mm, and the D1 is 0.6 to 0.7 mm, The axis of the discharge hole (2) forms an angle of 40 to 50 degrees with respect to the longitudinal direction of the tooth body, and is positioned toward the upper tongue side, avoiding the occlusion force-receiving area.

2. The improved crown structure of claim 1, wherein:

4. In the case of a crown for a molar, the discharge hole (2) is provided in the central fossa or in the area near the central fossa on the occlusal surface, and is spaced at least 2.0 mm from both the buccal functional cusp and the lingual functional cusp; D2 in the molar is 1.0 mm, and D1 is 1.1 to 1.2 mm, The axis of the discharge hole (2) of the molar coincides with the insertion path direction, and the outlet end of the discharge hole (2) is located in the non-functioning cusp region of the occlusal surface, and is formed so as to face the buccal non-functioning cusp in the maxillary molar and the lingual non-functioning cusp in the mandibular molar.

2. The improved crown structure of claim 1, wherein:

5. The inner peripheral wall of the discharge hole (2) is provided with three to four guide grooves (21) at equal intervals along the axial direction, each guide groove (21) having a width of 0.10 to 0.15 mm and a depth of 0.08 to 0.12 mm, and both ends of the guide groove (21) are extended to the end of the connecting surface (3) and the end of the outer surface (4) of the discharge hole (2).

5. The improved crown structure according to claim 2, 3 or 4, characterized in that:

6. A conical flared opening (22) is formed at the inlet of the discharge hole (2) on the adhesive surface (3) side, and the conical flared opening (22) has a cone apex angle of 60 to 90°, a maximum diameter of the flared opening that is 0.2 to 0.3 mm larger than D1, and a depth of 0.3 to 0.5 mm.

6. The improved crown structure of claim 5, wherein:

7. The discharge hole (2) is provided at its outlet on the outer surface (4) of the crown body (1) with an annular reinforcing rib (23) integrally molded with the crown body (1), and the material of the reinforcing rib (23) is the same as that of the crown body (1); The width of the reinforcing rib (23) is 0.3 to 0.5 mm, the amount of protrusion from the outer surface (4) is 0.1 to 0.2 mm, the inner diameter is equal to D2, and the outer diameter is 0.6 to 1.0 mm larger than the inner diameter.

7. The improved crown structure of claim 6, wherein:

8. The crown body (1) is provided with a biodegradable sealing member, the sealing member being composed of a sealing plug (5) that fits into the discharge hole (2), and made of polycaprolactone (PCL) or polylactic acid (PLA); The sealing plug (5) is composed of a head, a middle, and a tail, the head is provided with a locking structure (51) and the maximum diameter is adapted to D1, the middle is a columnar step (52) adapted to D2, the tail is provided with a disk-shaped positioning portion (53) that abuts against the annular reinforcing rib (23), the diameter of the disk-shaped positioning portion (53) is the same as the outer diameter of the reinforcing rib, the overall length of the sealing plug (5) is equal to the axial depth of the discharge hole (2), and the tail is configured to be flush with the crown outer surface (4).

8. The improved crown structure of claim 7, wherein:

9. The sealing plug (5) has one or two fine ventilation grooves (54) on its outer periphery along its axial direction, each having a width of 0.05 to 0.08 mm, which are used to exhaust traces of gas remaining in the exhaust hole (2) at the initial stage of adhesion.

9. The improved crown structure of claim 8, wherein:

10. The material of the crown body (1) is zirconia, glass ceramics, or a resin-based composite material, and the drain hole (2) is integrally formed with the crown body (1) by digital cutting or three-dimensional printing process.

10. The improved crown structure of claim 9, wherein:

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