KIM, Byung Kook (1 Sinwon Apt, Daeyeon 3-dong Nam-gu, Busan-city 608-778, 02-1706, KR)
PARK, Mu Young (205-101 Samik Apt, Namcheon-dong Suyeong-gu, Busan-city 613-010, KR)
EOM, Tae Gwan (1 Hyundai Apt, Jwa-dong Haeundae-gu, Busan-city 612-030, 05-1101, KR)
PARK, Sang Oh (1 Centum e-Pyeonhansesang Apt, Jaesong-dong Haeundae-gu, Busan-city 612-864, 04-1603, KR)
KIM, Byung Kook (1 Sinwon Apt, Daeyeon 3-dong Nam-gu, Busan-city 608-778, 02-1706, KR)
PARK, Mu Young (205-101 Samik Apt, Namcheon-dong Suyeong-gu, Busan-city 613-010, KR)
EOM, Tae Gwan (1 Hyundai Apt, Jwa-dong Haeundae-gu, Busan-city 612-030, 05-1101, KR)
| Claims [Claim 1] An implant fixture that is inserted into a bone tissue formed of a cortical bone and a cancellous bone by rotating on a central axis to thereby form an artificial tooth root, comprising: a first portion that is inserted into the cortical bone and comprises a first screw thread having first peak and first valley alternating with one another on an outer surface of the first portion; and a second portion that is disposed below the first portion and inserted into the cancellous bone, wherein a second screw thread having second peak and second valley alternating with one another is formed on an outer surface of the second portion, wherein distances between adjacent second peak of the second screw thread are greater than distances between adjacent first peak of the first screw thread, and a first screw thread of the first portion is rotated three times or less. [Claim 2] The implant fixture of claim 1, wherein a first screw thread of the first portion is rotated two times or less. [Claim 3] The implant fixture of claim 1, wherein five or less first peak are formed in the first portion along the central axis. [Claim 4] The implant fixture of claim 1, wherein a cross-section of a first screw thread, which taken along a plane that passes through the central axis in the first portion, is smaller than a surface area of an empty space between the first screw thread and another first screw thread adjacent to the first screw thread. [Claim 5] The implant fixture of claim 1, wherein a diameter of the second portion decreases downward. [Claim 6] The implant fixture of claim 1, further comprising: a coupling portion to which a tool for applying rotational torque is engaged and coupled; and a joining portion for joining a prosthesis. [Claim 7] The implant fixture of claim 6, wherein a protrusion that extends upwardly from an upper end of the first portion is formed as a single body with the first portion, wherein a diameter of the protrusion increases upward, and the coupling portion is a hole that extends downward and formed through the protrusion, and an inner surface of the hole has a form which can be coupled to the tool. [Claim 8] The implant fixture of claim 6, wherein a protrusion that extends and protrudes from an upper portion of the first portion is formed as a single body with the first portion, and an outer surface of the protrusion has a form which can be coupled to the tool. [Claim 9] The implant fixture of claim 6, wherein the coupling portion is a hole that extends downward from an upper end of the first portion, and an inner surface of the hole has a form which can be coupled to the tool. [Claim 10] The implant fixture of claim 7 or 9, wherein the joining portion is a groove that extends downward from the coupling portion and a female screw thread is formed on an inner surface of the joining portion. [Claim 11] The implant fixture of claim 8, wherein the joining portion is a groove that extends downward from an upper end of the protrusion, and a female screw thread is formed on an inner surface of the joining portion. [Claim 12] The implant fixture of claim 1, wherein a cutting edge is formed in a starting portion of the first screw thread of the first portion. [Claim 13] The implant fixture of claim 1, wherein a first height from a first peak to a first valley adjacent to the first peak of the first screw thread is 80% smaller than a second height from a second peak to a second valley adjacent to the second peak of the second screw thread. [Claim 14] The implant fixture of claim 1, wherein a diameter of the first portion is smaller than a diameter of the second portion. [Claim 15] The implant fixture of claim 1, wherein a cutting edge is formed in the second screw thread of the second portion, and the cutting edge comprises a first cutting edge that vertically extends along the central axis and a second cutting edge that is connected to the first cutting edge and spirally extended in an upward direction. |
Technical Field
[1] The present invention relates to an implant fixture, and more particularly, to a dental implant fixture that achieves initial fixing force even when inserted into a soft bone tissue like cancellous bone and reduces a time for osseointegration with peripheral bones.
[2] The present invention claims the benefit of Korean Utility Model Application No.
20-2009-0005326, filed on May 1, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Background Art
[3] FIG. 1 illustrates an implant fixture 100 according to the conventional art. The implant fixture 100 includes a second portion 120 having a large screw thread including peak 121 and valley 122 alternating with one another on a central axis of the implant fixture 100, and a first portion 110 that is disposed above the second portion 120 and includes a smaller screw thread than the screw thread of the second portion 120, which includes peak 111 and valley 112 alternating on the central axis of the implant fixture 100. Also, a cutting edge 130 that extends and caved in a rectangular form along the central axis of the implant fixture 100 is formed in the second portion 120, and outer diameters of the first portions 110 and the second portion 120 are the same along the central axis.
[4] The implant fixture 100 is inserted into a human body as follows. First, an implant hole is formed in a bone tissue of a human body by using, for example, a drill, and the implant fixture 100 is inserted into the implant hole. When the implant fixture 100 is inserted into the bone tissue, portions of the second portion 120 and the first portion 110 are implanted into a cancellous bone, and the other portion of the first portion 110 is implanted into a cortical bone. After the implantation is completed, bone tissues near the implant fixture 100 are grown to integrate with a surface of the implant fixture 100 to thereby fix the implant fixture 100. Disclosure of Invention
Technical Problem
[5] However, the implant fixture 100 according to the conventional art has the following drawbacks.
[6] First, usually, the cortical bone is thin and the cancellous bone is thick. Accordingly, if the first portion 110 is long and the second portion 120 is relatively short as in the conventional art, a portion of the first portion 110 must be implanted into the cancellous bone. However, if the first portion 110 is implanted into the cancellous bone, a large amount of bone tissues cannot be captured in the implant fixture 100, and thus cannot be sufficiently supported by the bone tissue. That is, although the number of screw threads of the first portion 110 is greater than that of the second portion 120 regarding the same distance, distances between the screw threads of the first portion 110 are small and depths of the screw threads are shallow and thus only a small amount of bone tissues can be captured between the screw threads, thereby weakening the whole supporting force of the implant fixture 100.
[7] Secondly, when inserting the implant fixture 100 and the second portion 120 is inserted after the first portion 110, the number of screw threads is abruptly increased and thus a rotational torque generated to insert the implant fixture 100 is rapidly increased. Accordingly, a portion of the bone tissue, particularly, a portion corresponding to the cortical bone, receives excessive load and bone damage may be generated. Such bone damage causes later bone absorption, which is a phenomenon that necrosis of bone tissues is generated. Solution to Problem
[8] The present invention provides an implant fixture capable of easily providing initial fixing force in a cancellous bone and preventing bone necrosis or bone absorption after implantation.
Advantageous Effects of Invention
[9] According to the implant fixture of the present invention described above, the second portion having large a screw thread is implanted into the cancellous bone, and a large amount of bone tissues can be captured between the screw threads. Accordingly, sufficient supporting force for the implant fixture may be provided when the bone tissues are integrally grown.
[10] Also, according to the implant fixture of the present invention, a cutting edge is formed in a starting portion of the first portion, and thus rotational torque is not abruptly increased when the second portion is implanted after the first portion, thereby reducing the possibility of bone damage and bone absorption. Brief Description of Drawings
[11] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
[12] FIG. 1 illustrates an implant fixture according to the conventional art;
[13] FIG. 2 is a perspective view illustrating an implant fixture according to an embodiment of the present invention;
[14] FIG. 3 is a front view of the implant fixture of FIG. 2; [15] FIG. 4 is a cross-sectional view of the implant fixture of FIG. 2;
[16] FIG. 5 is a schematic view illustrating the implant fixture of FIG. 2, being implanted into a bone tissue;
[17] FIG. 6 is a perspective view illustrating an implant fixture according to another embodiment of the present invention;
[18] FIG. 7 is a cross-sectional view of the implant fixture of FIG. 6;
[19] FIG. 8 is a schematic view illustrating the implant fixture of FIG. 6, being implanted into a bone tissue;
[20] FIG. 9 is a perspective view illustrating an implant fixture according to another embodiment of the present invention;
[21] FIG. 10 is a cross-sectional view of the implant fixture of FIG. 9; and
[22] FIG. 11 is a schematic view illustrating the implant fixture of FIG. 9, being implanted into a bone tissue. Best Mode for Carrying out the Invention
[23] Exemplary embodiments of the present invention will now be described in detail with reference to the attached drawings.
[24] FIG. 2 is a perspective view illustrating an implant fixture 10 according to an embodiment of the present invention. FIG. 3 is a front view of the implant fixture 10 of FIG. 2. FIG. 4 is a cross-sectional view of the implant fixture 10 of FIG. 2.
[25] The implant fixture 10 according to the present embodiment is inserted into a bone tissue consisting of a cortical bone 1 and a cancellous bone 2 so as to form an artificial tooth root.
[26] The implant fixture 10 has a cylindrical shape and an outer surface on which a screw thread is formed. When the implant fixture 10 rotates about a central axis, the implant fixture 10 is inserted into the cortical bone 1 and the cancellous bone 2 to form screw root at an inner surface of an implant hole 3 formed in a bone tissue using a drill in advance. The implant fixture 1 may be formed of titanium or any other type of a metal material that is not rejected by the human body.
[27] The implant fixture 10 includes a protrusion 50, a first portion 20, and a second portion 30.
[28] The protrusion 50 extends from an upper end of the first portion 20 to protrude upward. In detail, the protrusion 50 has an outer diameter that increases upward and a smooth and curved side portion. A coupling portion 51 that extends downward from the upper end of the protrusion 50 is formed in the protrusion 50. The coupling portion 51 is a hole having an inner surface with a cross-section to which a tool for rotating the implant fixture 10 may be coupled. In detail, the coupling portion 51 may preferably have a polygonal cross-section or other various cross-sections form. As a tool such as a driver is inserted into the coupling portion 51 and engaged with the inner surface of the coupling portion 51, the implant fixture 10 can be completely rotated.
[29] The first portion 20 refers to a portion of the implant fixture 10 that is mostly inserted into the cortical bone 1 when the implant fixture 10 is inserted (the portion of the first portion 20 may also be implanted into the cancellous bone 2). A first screw thread 22 is formed on an outer surface of the first portion 20. The first screw thread 22 has a spiral form, and includes first peak 22a and first valley 22b alternating with one another.
[30] The height of the first portion 120 is sufficiently high to be inserted only into the cortical bone 1. In detail, the first screw head 22 may preferably be disposed by being wound three times or less, more preferably, two times or less, or five or less, more preferably three or less first peak 22a may be disposed along the central axis. Accordingly, the deterioration of a fixing force as the first portion 20 is inserted into the cancellous bone 2 may be prevented. Also, a first height hi of the first screw thread 22 in the first portion 20 from a first peak 22a to an adjacent first valley 22b may preferably be smaller than 80% of a second height h2 of the second portion 30 from a second peak 32a of a second screw thread 32 to an adjacent second valley 32b. Accordingly, sufficient pressure is applied to adjacent valley (22b or 32b) when the second portion 30 is implanted after the first portion 20, thereby fixedly implanting the implant fixture 10.
[31] A joining portion 60 for joining with a prosthesis is further formed in the first portion
20. In detail, the prosthesis (not shown) refers to an abutment that is coupled to the protrusion 50, which is coupled to the implant fixture 10 with a bolt (not shown), and the joining portion 60 is formed to fix the bolt. The joining portion 60 is a groove that extends from the coupling portion 51 in a downward direction and includes a female screw thread having a corresponding shape to an outer surface of the bolt.
[32] A cross-section A of the first screw thread 22 of the first portion 20, which is taken along a plane passing across the central axis, is smaller than a surface area B of an empty space between the first screw thread 22 and a screw thread adjacent to the first screw thread 22. That is, the first screw thread 22 is not blunt but sharp and thus the implant fixture 10 may be easily inserted into a bone tissue during implantation.
[33] Also, a cutting edge 21 that is parallel to the plane including the central axis is formed in a starting portion of the first screw thread 22 of the first portion 20 where the first screw thread 22 starts. The cutting edge 21 increases initial cutting force of the cortical bone 1 when the second portion 30 is inserted after the first portion 20 so that a female screw thread is formed in the cortical bone 1 more effectively. Also, damage of the bone tissue due to an abrupt increase of torque is prevented using the cutting edge
21, thereby reducing the possibility of bone absorption. [34] The second portion 30 is disposed below the first portion 20. In detail, the second portion 30 is coupled to the first portion 20 as a single body. The most second portion 30 is inserted into the cancellous bone 2, thereby forming a lower portion of the implant fixture 10. The second screw thread 32 including the second peak 32a and the second valley 32b alternating with one another is formed on an outer surface of the second portion 30. The second screw thread 32 has a spiral form. Distances (pitch) between the adjacent second peak 32a of the second screw thread 32 are greater than distances between the adjacent first peak 22a of the first screw thread 22. That is, the size of the second screw thread 32 is greater than that of the first screw thread 22, and thus the second screw thread 32 is referred to as a 'macro-screw thread'. On the other hand, the first screw thread 22 is smaller than the second screw thread 32 and thus is referred to as a 'micro-screw thread'. Diameters Dl and D2 of the first portion 20 and the second portion 30 are the same.
[35] As described above, the sizes of the first screw thread 22 and the second screw thread
32 vary due to the quality of bones into which they are respectively implanted. For example, the first portion 20 that is implanted into the cortical bone 1 that is hard includes dense screw threads for concentration of stress in a contacting portion between the first portion 20 and the cortical bone 1, thereby uniformly distributing the entire stress to a peripheral bone tissue 40. On the other hand, the second portion 30 inserted into the cancellous bone 2, which is relatively soft, is formed with a size that increases an amount of bone tissue being captured to thus obtain sufficient fixing force. In particular, as describe above, the second portion 30 with which a sufficient amount of bone tissues can be provided is formed to be longer than the first portion 20 so that the first portion 20 is mostly implanted only into the cortical bone 1 and the second portion 30 is mostly implanted only into the cancellous bone 2.
[36] The distances the first screw thread 22 and the second screw thread 32 move per one rotation along the central axis are set to be the same. If the distances they move along the central axis are different, a greater rotational torque is required during implantation, and this may apply a strong pressure to the peripheral bone tissue 40 and cause cracks therein.
[37] Also, a cutting edge 31 that is caved toward the central axis is formed in the second portion 30. The cutting edge 31 extends upward from a lower end of the second portion 30.
[38] The cutting edge 31 comprises a first cutting edge 31a and a second cutting edge 31b.
The first cutting edge 31a is a portion of the cutting edge 31 that extends from the lower end of the second portion 30 to a center portion of the second portion 30 in an upward direction vertically along the central axis. The greatest depth of the first cutting edge 31a may preferably be greater than a vertical distance between a peak point of the second screw thread 32 and a valley adjacent to the peak point thereof, that is, the height of the second screw thread 32, more preferably, 1.2-1.5 times greater than the height of the second screw thread 32. The first cutting edge 31a is caved in deeper than the first screw thread 22 so that the cutting edge 31 easily cuts a peripheral bone tissue of the implant hole 3 positioned at a lower end of the implant fixture 10. When the greatest depth of the first cutting edge 31a is 1.2 times smaller than the height of the screw thread 32, it is difficult to obtain a sufficient cutting effect. When the greatest depth of first cutting edge 31a is greater than 1.5 times the height of the second screw thread 32, a cutting effect increases but the intensity of the entire implant fixture 10 may be weakened.
[39] The second cutting edge 31b extends upwardly but not parallel to the central axis, which is different from the first cutting edge 31a. In detail, the second cutting edge 31b has an inclined shape, being wound in a spiral form and extended in an upward direction.
[40] As described above, the forms of the first cutting edge 31a and the second cutting edge 31b vary in order to improve surface roughness of the cancellous bone 2 by minutely cutting the peripheral bone tissue 40, which has been roughly cut using the first cutting edge 31a, with the second cutting edge 31b. That is, as the second cutting edge 31b rotates, the peripheral bone tissue 40 that has been cut roughly using the first cutting edge 31a may be smoothed.
[41] The smallest depth of the second cutting edge 31b may preferably be smaller than a vertical distance between a peak point of the second screw thread 32 and a valley adjacent to the peak point thereof, that is, the height of the second screw thread 32, more preferably, 0.5-0.8 times the height of the second screw thread 32. When the smallest depth of the second cutting edge 31b is smaller than 0.5 times the height of the second screw thread 32, a cutting effect is reduced, and when the smallest depth of the second cutting edge 31b is greater than 0.8 times the height of the second screw thread 32, the second cutting edge 31b may not sufficiently smooth the peripheral bone tissue 40.
[42] The dental implant fixture 10 according to the current embodiment of the present invention has the following effects. First, as illustrated in a left portion of FIG. 5, an implant hole having a diameter hi is formed in a bone tissue with a drill and an implant fixture is inserted into the implant hole. In detail, a predetermined driver is inserted into a coupling portion of a protrusion so that an outer surface of the driver is engaged with an inner surface of the coupling portion to rotate with the coupling portion at the same time, and then the driver is rotated so as to rotate the implant fixture. Also, pressure is applied to the driver along the central axis and the implant fixture is inserted into the implant hole, thereby forming a female screw thread on an outer surface of a bone tissue.
[43] In detail, as a first cutting edge positioned at a lowermost end of the implant fixture forms a female screw thread in a peripheral bone tissue, a second portion is inserted into the implant hole at the same time. After the first cutting edge is inserted, the second cutting edge is inserted, thereby cutting and smoothing the bone tissue and smoothing the peripheral bone tissue and forming a predetermined female screw thread in a cancellous bone at the same time. After the second portion is completely inserted, the first portion is inserted, and here, a cutting edge formed in a starting portion of the first portion cuts the peripheral bone tissue such that the first portion is easily inserted into the implant hole. The implant fixture 10 that is completely inserted into the bone tissue is shown in a right side of FIG. 5.
[44] As described above, after the implant fixture is inserted completely, a prosthesis is disposed on the protrusion of the implant fixture so as to be coupled thereto, and a predetermined bolt is screw-coupled to a joining portion.
[45] The implant fixture 10 according to the current embodiment of the present invention may also be modified as follows.
[46] While the coupling portion 51 with which a tool for applying rotational torque is engaged is formed on the inner surface of the protrusion 50, the coupling portion 51 may also be formed above the protrusion 50 on an outer surface thereof. In detail, as illustrated in FIGS. 6 through 8, the protrusion 50 extends from the first portion 20 in an upward direction, and may have a polygonal outer cross-section so that a tool (not shown) such as a driver is engaged with the outer surface of the protrusion 50. Also, the joining portion 60 is a groove extending from an upper end to a lower end of the protrusion 50, and a female screw thread having a shape corresponding to a predetermined bolt is formed on the inner surface of the joining portion 60.
[47] Second, while the coupling portion 51 for applying rotational torque is protruded from the upper end of the first portion 20 in an upward direction, the coupling portion 51 may also be formed as a hole that extends from the upper end to a lower end of the first portion 20, as illustrated in FIGS. 9 through 11, and a polygonal surface which may be coupled to the tool may be formed on an inner surface of the hole.
[48] Also, the joining portion 60 is a groove extending from the coupling portion 51 in a downward direction, and a female screw thread for screw-coupling with a bolt may be formed on an inner surface of the joining portion 60.
[49] Third, the diameter D2 of the second portion 30 is vertically uniform in the above embodiments but the diameter D2 may also gradually decrease downward. When the diameter D2 of the second portion 30 varies, pressure is gradually applied to a peripheral cancellous bone tissue during implantation, thereby further increasing the total supporting force. [50] Also, while the diameter Dl of the first portion 20 and the diameter D2 of the second portion 30 are the same in the above embodiments, the diameter Dl of the first portion 20 may be smaller than the diameter D2 of the second portion 30. In this case, implantation torque does not abruptly increase when the first portion 20 is implanted after the second portion 30 is implanted, and thus the possibility of damage to the peripheral bone tissue or bone absorption is reduced.
[51] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
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