Technical Field The present invention relates to an implant, and more particularly, to a fixture and dental implant which may more securely fix an abutment or a transmucosal abutment and be compatible with other abutments.

Background Art A dental implant indicates an artificial tooth structure formed by a .process in which a fixture, an artificial dental root, is implanted in a part where a tooth is partially or entirely lost to be adhered to an alveolar bone, and a tooth prosthesis is fixed to the artificial dental root. Also, a word of "implant" may be used as an inclusive concept including a method of performing a dental procedure, in wide sense, or may be used as the same meaning of a fixture, in narrow sense. An implant in the present specification may be used as a general artificial tooth structure. Generally, an implant is usually composed of a fixture of titanium, an abutment fixed on the fixture, an abutment screw fixing the abutment on to the fixture, and a crown which is an artificial tooth fixed on the abutment. An implant may be performed only at a lost portion with no injury of other portions or teeth adjacent to a lost tooth, may support osseous tissue to delay absorption speed of the osseous tissue, may provide masticatory force the same as a natural tooth, and aesthetically formed approximately as the same as a natural tooth in appearance. Accordingly, implants are currently widely used as a method of performing dental procedure for repairing injured or lost teeth. Implants described above may be classified into external connection-type implants (hereinafter, referred to as external implants) and internal connection-type implants (hereinafter, referred to as internal implants).

External implants An external implant includes a fixture, an abutment, and a crown. A connection projection is formed on the top surface of the fixture, and a connection

RFfvmn efvatv > TDAMCI A-ΠΠM recess is formed around the bottom of the abutment in order to fit the connection projection. Generally, the connection projection and the connection recess are formed in a circular or non-circular shape, and a screw hole for an abutment screw is formed in the center. Particularly, when connection projections and connection recesss formed in the non-circular shape such as a hexagonal or octagonal shape are used, the connection projections may prevent relative rotation between a fixture and an abutment and assist to easily fit direction when positioning the abutment on to the fixture. The use of implants began with external implants. Since various designs of implants and a lot of clinical results according to the designs of the implants are available, external implants are most generally used. FIG. 1 is a cross-sectional view illustrating a conventional external implant. Referring to FIG. 1, an implant 10 using an UCLA abutment is made by a screw-retained prosthesis. The implant 10 includes a fixture 12, an abutment 14, and a crown 18. The fixture 12 is implanted in an alveolar bone, and the abutment 14 is formed in a single body with the crown 18 and fixed on the fixture 12. An external connection projection 13 is formed on the fixture 12. The external connection projection 13 is formed in a shape of a hexagonal prism, and a screw hole is provided in the center of the external connection projection 13. Also, an external connection recess 15 is provided around the bottom of the abutment in response to the external connection projection 13. Since the external connection recess 15 is formed in a hexagonal prism shape according to the external connection projection 13, the external connection recess 15 snuggly fits the external connection projection 13. Before the abutment 14 is fixed on the fixture 12, the abutment 14 and the crown 18 are adhered in a single body, and a screw 16 is engaged with the fixture 12 through a hole penetrating the center of the abutment 14 and the crown 18. The screw 16 is engaged with the fixture 12, thereby fixing the crown 18 and the abutment 14 on the fixture 12. FIG. 2 is a cross-sectional view illustrating another conventional external implant. Referring to FIG. 2, an implant 20 is one of external implants, which uses a transmucosal abutment 24. The implant 20 of FIG. 2 includes a fixture 22, a transmucosal abutment 24, an upper abutment 26, and a crown 28. The upper abutment 26 is formed in a single shape with the crown 28 and disposed on the transmucosal abutment 24. The transmucosal abutment 24 includes a hole in response to a first screw 24-1, and the first screw 24-1 is engaged with the fixture 22 via the transmucosal abutment 24, thereby fixing the transmucosal abutment 24 on the fixture 22. A second screw 26-1 is inserted through a hole penetrating the crown 28 and the upper abutment 26 and bonded to a screw hole formed above the first screw 24-1, thereby fixing the crown 28 and the upper abutment 26 on the transmucosal abutment 24. A connection recess 27 in response to the head of the first screw 24-1 is formed around the bottom of the upper abutment 26. Referring to FIGS. 1 and 2, in external implants, an external connection projection formed on a fixture and an external connection recess formed around the bottom of an abutment are mutually adhered to mutually bond the abutment to the fixture. Generally, external implants are manufactured according to Branemark method, 3i method, etc., and connection projections and connection holes are in a shape of straight hexagonal prism and have a height of approximately 0.7mm and a width of approximately 2.7mm. Since the height of a connection projection is small, an external connection projection may be quickly worn or the connection between the external connection projection and an external connection recess is loosened, which may cause an abutment to be easily extracted. To solve this problem, a connection projection has been manufactured to have a height of lmm or more, and a connection projection has been manufactured in a shape of an octagonal prism or spline, but the problem still is not overcome. Particularly, since the methods described above are incompatible with each other, a lot of dentists shun these methods. In addition, loosening or breaking of a screw frequently occurs.

Internal implants An internal implant includes a fixture, an abutment, and a crown. A connection recess. is formed on the fixture instead of a connection projection, and a connection projection is formed around the bottom of the abutment in response to the connection recess. The described above is an exact opposite construction as compared to external implants. Since a long space if formed above the fixture, an area for contacting the fixture and abutment may be widely formed. Generally, the connection projection and the connection recess are formed in a circular or non-circular shape, and a hole for an abutment screw is formed in the center. The internal implant is for overcoming the shortcomings of the external implant and has an advantage of stably supporting the abutment using a relatively wide area. FIG. 3 is a cross-sectional view illustrating a conventional internal implant. Two types of internal implants are indicated respectively as (a) and (b) in FIG. 3. Referring to (a) of FIG. 3, an internal implant includes a fixture 42, an internal abutment 44, a screw 46, and a crown 48. The fixture 42 includes a connection recess 43 formed on the upper end portion, and the abutment 44 includes a connection projection 45 in response to the connection recess 43. The connection projection 45 is formed around the bottom of the abutment 44, and a top supporting surface is formed on the top in order to contact and support the crown 48. The connection recess 43 of the fixture 42 includes a recess located in the entry and formed in a conical shape and a recess formed in a shape of a hexagonal or octagonal prism. The connection projection 45 of the abutment 44 includes a fitted portion 45 a formed in a shape of a cone and an anti-rotation portion 45b formed in a shape of a hexagonal or octagonal prism in response to the shapes of the connection recess 43. When the connection projection 45 of the abutment 44 is inserted into the fixture 42, the fitted portion 45a supports the body of the abutment 44 and the anti- rotation portion 45b is connected to the bottom of the connection recess 43 and prevents relative rotation of the abutment 44 to the fixture 42. Referring to (b) of FIG. 3, an internal implant includes a fixture 52, an internal abutment 54, a screw 56, and a crown 58. The fixture 52 includes a connection recess 53 on the top, and a connection projection 55 is provided around the bottom of the abutment 54 in response to the connection recess 53. The connection recess 53 of the conventional fixture 52 is formed in a shape of a prism having a cross section of a round or a polygon, and the connection projection 44 of the abutment 54 is formed in a shape of a cylinder or a prism. Particularly, when a connection projection formed in a shape of a cylinder is used, a projection or a groove may be formed in order to restrict rotation between the connection projection and the connection recess. As shown in (a) and (b) of FIG. 3, since a connection projection and connection recess are formed in a shape of a cylinder or a prism in structures of internal implants, they may make a wide contact area to be supported, loosening of a screw does not occur, and an implant is complete by performing almost one operation. However, in order to separate an abutment from a fixture, the abutment is certainly retreated in a direction of an axis and a distance to move in the direction of the axis is very long. Accordingly, internal implants are mainly used for repairing one tooth and there are many difficulties and limitations by applying a splint-type implant, in order to repair three or more adjacently injured teeth, thereby being scarcely used. Also, though ITI method is generally used for manufacturing internal implants, there is no wide assortment of methods to choose from compared with external implants. Since each manufacturer adopts a unique shape, compatibility is poor. A dental implant system is disclosed in U.S. Patent No. 6,419,492. The dental implant system also includes a fixture and an abutment. The fixture of the dental implant system includes a head portion and a body portion, and the head portion includes a space including a tapered sidewall. An anchoring post is projected from the bottom of the space of the head portion, and an indexing means is formed as an end portion of the anchoring post. The abutment also includes first and second spaces provided on the top and bottom, and the abutment has a tapered shape in response to the tapered sidewall of the space formed in the head portion of the fixture. Accordingly, the first space located at the bottom containing the anchoring post, and the bottom of the abutment is adhered and fixed to the head portion of the fixture. The anchoring post and indexing means of the fixture are formed in the center of the space of the head portion in order to prevent relative rotation of the abutment. However, the fixture has a structure in which an anti -rotation portion is projected inside based on an internal connection method, which inverses the anti-rotation portion 45b of (a) of FIG. 3 to make the process difficult. Also, since the shape and size are different from conventional abutment and fixture, it is impossible to be compatible with other products. As described above, external implants are used world-wide as an elementary form. There are advantages in that manufacturing is relatively simple compared with other methods and the shape and size of the fixture and abutment are almost standardized, thereby having good compatibility. However, since the height of an external connection projection is low, approximately 0.7 to 1.0mm, a possibility that an abutment is separated from a fixture is higher than other methods and loosening of a screw relatively frequently occurs. On the other hand, in case of internal implants, since a connection recess is formed, within a fixture, the height of connected area is increased and loosing of screw is repressed. However, unlike external implants, there is not a great variety to choose from and each manufacturer adopts a unique shape, therefore compatibility is not good. Also, internal implants have many limitation and difficulties to repair teeth when using a splint or overdenture method.

Disclosure of Invention The present invention provides a fixture of a dental implant, which may solve problems of external connection methods by adopting merits of internal implants based on external connection methods. The present invention also provides a fixture of a dental implant, which has a structure for using other conventional external abutments. Therefore, dentists may get optimum effects by using an abutment according to the present invention and use an abutment according to a 3i or Branemark method when repair teeth by splinting several artificial teeth. Also, when an abutment that fits neatly to a fixture is not obtainable, but an abutment according to the 3i or Branemark method may be obtained, a conventional abutment according to the 3i or Branemark method may be used, thereby improving compatibility. The present invention also provides a dental implant having an abutment and fixture including merits of external implants and internal implants and overcoming demerits of external implants and internal implants. According to an aspect of the present invention, there is provided a fixture including an external joining projection, a flange, an internal joining recess, and a fixture body. The fixture body is implanted in an alveolar bone or mandible, adsorbed into osseous tissue, and fixed to the osseous tissue to support an implant. Generally, the fixture is formed of a titanium alloy, and a tissue bonding portion is provided on the outer surface of the fixture body. The tissue bonding portion is directly adsorbed into the osseous tissue, in which a screw thread may be formed or a surface on which a porosity process is performed may be formed to be readily absorbed into the tissue. The flange is provided above the fixture body, and the external joining projection formed in a polygonal prism shape is provided above the flange. The external joining projection is for joining the abutment and formed in a hexagonal or octagonal prism shape, in which a first screw hole is formed to a predetermined depth in the center. In this case, a polygonal prism indicates a prism having a polygonal section and getting down to specifics, straight and tapered truncated pyramids may be included. The internal joining recess is formed sequentially or nonsequentially around the external joining projection on the top surface of the flange. In response to the internal joining recess, an internal joining projection may be formed around the bottom of the abutment. The abutment is joined with the fixture according to external connection method and internal connection method by inserting the internal joining projection in the internal joining recess. Of course, the external joining projection may respond to conventional external abutment, an abutment without an internal joining projection may be fitted to the fixture. Particularly, in the case of the fixture having the configuration described above, instruments or kits used in conventional external connection methods may be used in impression copings or other implant processes, thereby not requiring additional instruments. According to another aspect of the present invention, there is provided a dental implant including an abutment assembly joined to the top of the fixture. The abutment assembly may be formed in a single body and formed in two bodies composed of an upper abutment and transmucosal abutment. The abutment assembly includes an external joining recess in response to the external joining projection of the fixture and an internal joining projection in response to the internal joining recess of the fixture. The external joining recess and the internal joining projection are formed around the bottom of the abutment assembly. Also, a second screw hole in response to the first screw hole is provided in the center of the abutment assembly. The second screw hole is for passing a screw, in which a female screw may be formed inside. Since the fixture includes the external joining projection and the abutment includes the external joining recess in response to the external joining projection, a conventional external connection method may be used. Also, since the fixture includes the internal joining recess formed around the external joining recess and the abutment includes the internal joining projection, the fixture of the present invention may be joined with the abutment of the present invention according to the internal connection method. Accordingly, the abutment may be stably fixed on the fixture by using both connection methods.

Brief Description of Drawings FIG. 1 is a cross-sectional view illustrating a conventional external implant; FIG. 2 is a cross-sectional view illustrating another conventional external implant; FIG. 3 is a cross-sectional view illustrating a conventional internal implant; FIG. 4 is a perspective view illustrating a fixture for a dental implant according to a first embodiment of the present invention; FIG. 5 is a top view of the fixture for the dental implant according to the first embodiment; FIG. 6 is an exploded front view illustrating the fixture and an implant according to the first embodiment; FIG. 7 is a cross-sectional view illustrating a state in which the fixture and the abutment are coupled according to the first embodiment; FIGS. 8 and 9 are top views respectively illustrating fixtures according to other embodiments of the present invention; FIG. 10 are top and cross-sectional views illustrating a fixture according to another embodiment of the present invention; FIG. 11 is an exploded front view illustrating a dental implant according to a second embodiment of the present invention; FIG. 12 is a perspective view of an impression coping according to a third embodiment of the present invention; FIG. 13 is a perspective view of a lab analog according to the third embodiment; FIG. 14 is a partial cross-sectional view illustrating a state in which the impression coping according to the third embodiment is joined with the lab analog according to the third embodiment of the present invention; FIG. 15 is a perspective view illustrating a fixture for a dental implant according to a fourth embodiment of the present invention; FIG. 16 is a top view of the fixture for the dental implant according to the fourth embodiment; FIG. 17 is an exploded front view illustrating the fixture and an implant according to the fourth embodiment; FIG. 18 is a cross-sectional view illustrating a state in which the implant according to the fourth embodiment is engaged; FIG. 19 is a cross-sectional view illustrating a process of adhering and separating a splinted prosthesis from a conventional fixture; FIG. 20 is a cross-sectional view illustrating a process of adhering and separating a splinted prosthesis from the fixture according to the fourth embodiment; FIGS. 21 and 22 are top views respectively illustrating fixtures according to other embodiments of the present invention; FIG. 23 is an exploded front view illustrating a dental implant according to a fifth embodiment of the present invention; FIG. 24 is a perspective view of an impression coping according to a sixth embodiment of the present invention; FIG. 25 is a perspective view of a lab analog according to the sixth embodiment; and FIG. 26 is a partial cross-sectional view illustrating a state in which the impression coping and lab analog according to the sixth embodiment are "mutually bonded.

Best Mode for Carrying Out the Invention Hereinafter, the present invention will be described in detail by explaining embodiments of the invention with reference to the attached drawings. However the present invention is not defined and restricted by the following embodiments. Embodiment 1 FIG. 4 is a perspective view illustrating a fixture for a dental implant according to a first embodiment of the present invention, and FIG. 5 is a top view of the fixture for the dental implant according to the first embodiment. Referring to FIGS. 4 and 5, a fixture 110 includes a fixture body 120, a flange 140, an internal joining recess 142, and an external joining projection 130. The fixture body 120 is composed of a titanium alloy, and a screw thread is formed on the outer surface of the fixture body. The fixture body 120 may dig into the osseous tissue using the screw thread and adhered to the osseous tissue for a long time after entering the osseous tissue. When being adhered to the osseous tissue, the fixture body 120 is formed in a single body with the mandible and stably supports the implant, as an artificial dental root. In this case, in addition to make the fixture body 120 easily entered, the screw thread functions as a tissue bonding portion to form a wide area adhered to the osseous tissue. A plurality of recesses may be formed at the end portion of the fixture body 120. Also, a surface on which a porosity process is performed may be formed on the fixture body to increase the area adhered to the osseous tissue to the maximum. For example, in case of an Endopore implant, an implant has a unique surface structure such as a sintered surface instead of a surface corroded by acid or coated by apatite hydroxide used in other implants, thereby widening the surface of the fixture to obtain strong osseous connection in case that the quantity of bone material is not sufficient. The flange 140 is provided above the fixture body 120, and the external joining projection 130 formed in a shape of a straight polygonal prism is provided above the flange 140. In this case, the flange and the external joining projection 130 are formed as a single body with the fixture body 120 and composed of a titanium alloy. The external joining projection 130 is for joining an abutment and formed in a shape of a polygonal prism such as a hexagonal or octagonal prism, in which a first screw hole 138 is formed to a predetermined depth in the center. The external joining projection 130 is fo.r attaching the abutment connected by an external connection method and has a width of approximately 0.7mm, similar to Branemark implants. The first screw hole 138 may be extended to the fixture body 120 along the axis of the fixture 110 and engaged with a screw 160 penetrating an abutment 150 to fix a crown C and the abutment 150 to the fixture, as shown in FIGS. 6 and 7. The internal joining recess 142 formed in a circular shape is formed around the external joining projection 130 on the flange 140. The internal joining recess 142 is formed to a width of approximately 0.2 to 0.5mm and a depth of approximately 0.6 to 1.0mm and in a circular shape connected into one. Also, a supporting surface 144 having a predetermined width is formed between the top end portion of the flange 140 and the internal joining recess 142. The supporting surface 144 is for supporting the internal joining recess 142 with the bottom of the abutment 150 and may support the bottom of an abutment in the case that the abutment mounted above does not include an inter joining projection. A margin portion 146 is provided around the flange 140. Since the margin portion 146 is formed around the flange, the osseous tissue around the fixture 110 can support the flange 140 and the margin portion 146 prevented the fixture from sinking down and the margin portion 146 can provide a sidewall having a sufficient thickness to form the internal joining recess 142. Namely, the fixture 110 according to the present embodiment, as follows, may stably support not only abutments having an internal joining projection but also other conventional abutments by using standards used in Branemark system, 3i system, etc. When a conventional abutment is fixed, the supporting surface 144 at the top of the flange 140 supports the bottom of the abutment. FIG. 6 is an exploded front view illustrating the fixture and an implant according to the first embodiment, and FIG. 7 is a cross-sectional view illustrating a state in which the implant according to the first embodiment is engaged. Referring to FIGS. 6 and 7, an implant 100 includes the fixture 110 and the abutment 150. The abutment 150 is an abutment for Screw-Cement Retained Prothesis (SCRP) and includes an external joining recess 154 in response to the external joining projection 130 of the fixture 110. In the present embodiments, since the external joining projection 130 is formed in a shape of a hexagonal prism, the external joining recess 154 provides a recess in the shape of the hexagonal prism. Also, an internal joining projection 152 is formed around the entry of the external joining recess 154 at the bottom of the abutment 150. The internal joining projection 152 is formed in a shape of a ring in response to the internal joining recess 142 and projected from the bottom of the abutment 150. A second screw hole 158 connected to the external joining recess 154 is formed in the center of the abutment 150. A screw 160 is engaged with the first screw hole 138 of the fixture 110. In this case, the abutment 150 bonded to the crown C may be provided to be fixed to the fixture 110 by the screw 160. However, only the abutment 150 is fixed to the fixture 110 by the screw 160, and the crown C is fixed to the abutment using cement. In the case the height of the external joining projection 130 is approximately 0.7mm and the depth of the internal joining recess 142 is approximately 0.8mm as the present embodiment, connection length between the fixture 110 and the abutment 150 may be increased to be double for a conventional length. Also, the sidewall of the internal joining recess 142 is formed vertically to the top of the flange 140. However, according to other embodiments of the present invention, at least one of the sidewalls is formed as tapered to be inclined looking upward, and the incline may make it easy to adhere or separate. FIGS. 8 and 9 are top views illustrating fixtures according to other embodiments of the present invention. Referring to FIG. 8, an internal joining recess 143 is formed on the flange 140 nonsequentially. Different from the previous embodiment, the internal joining recess 143 has a shape nonsequentially formed as regularly or irregularly carved out. As shown in FIG. 8, since the internal joining recess 143 is formed nonsequentially, a direction in which an abutment is mounted may be easily defined and the supporting surface 144 may be widely secured. Referring to FIG. 9, an internal joining recess 143-2 is formed on the flange 140 nonsequentially. The internal joining recess 143-2 is formed adjacent to the side bottom of the external joining projection 130 formed in a shape of a hexagonal prism. In the present embodiment, the three internal joining recesss 143-2 are formed at an interval of 120° respectively. However, six internal joining recesss may be formed at an interval of 60°. Since the internal joining recess 143-2 is formed nonsequentially, a direction in which an abutment is mounted may be easily defined. Also, as shown in FIG. 9, since the internal joining recess 143-2 is closely adjacent to the external joining projection 130 to stick an inner side of the internal joining recess 143-2 to the outer surface of the external joining projection 130, the supporting surface 144 for supporting an abutment may be widely secured. Particularly, it is difficult in a fixture in a small size to secure a space to provide the internal joining recess 143-2. However, in the present embodiment, the internal joining recess 143-2 is formed nonsequentially and adjacent to the external joining projection 130, thereby securing a wide space. FIG. 10 is a top and cross-sectional view illustrating a fixture according to another embodiment of the present invention. Referring to FIG. 10, the internal joining recess 142 is formed on the flange sequentially, and the outer surface of the external joining projection 130 is formed on the same plane with the inner sidewall of the internal joining recess 142. Therefore, the space in which the internal joining recess 142 is formed around the external joining projection 130 may be increased, thereby keeping the outer diameter of a joining recess smaller than other internal joining recesss and the supporting surface 144 of the top of the flange 140 wider.

Embodiment 2 FIG. 11 is an exploded front view illustrating a dental implant according to a second embodiment of the present invention. Referring to FIG. 11, an implant 200 according to the second embodiment includes a fixture 210 and an abutment assembly, and the abutment assembly includes a transmucosal abutment 250 and an upper abutment 270. The fixture 210 includes a fixture body 220, a flange 240, an internal joining recess 242, and an external joining projection 230. The fixture body 220 is composed of a titanium alloy, and a tissue bonding portion is formed on the outer surface of the fixture body. The tissue bonding portion may include a screw thread or a surface on which a porosity process is performed, and a plurality of recesses may be formed on the end portion of the fixture body 220. The flange 240 is provided above the fixture body 220, and the external joining projection 230 formed in a polygonal prism shape is provided above the flange 240. In this case, the flange 240 and the external joining projection 230 are formed in a single body with the fixture body 220 and composed of a titanium alloy. The external joining projection 230 is for bonding an abutment and formed in a shape of polygonal such as a hexagonal or octagonal prism, in which a screw hole is formed to a predetermined depth in the center. The external joining projection 230 attaches the transmucosal abutment 250 connected by an external connection method and follows a Branemark system. The internal joining recess 242 formed in a circular shape is formed around the external joining projection 230 above the flange 240. The internal joining recess 242 is formed of a circle connected to one, and a supporting surface 244 having a predetermined width is formed between the end portion of the top of the flange 240 and the internal joining recess 242. A micro unevenness is formed around the side of the flange 240. The micro unevenness 249 forms a plurality of unevennesses along the circumference of the flange 240, so that the flange may be easily adsorbed into the surrounding gingival tissue, and may prevent the surrounding gingival tissue from drooping down by the passage of time. Like the first embodiment, a margin portion 246 is provided around the flange 240. Since the margin portion 246 is formed on the flange having a predetermined size, the drooping down of osseous tissue around the fixture 210 over time may be prevented and a sidewall sufficient to form the internal joining recess may be provided. The transmucosal abutment 250 is a SCRP abutment, an internal joining recess 254 is formed around the bottom of the transmucosal abutment 250 in response to the external joining projection 230 of the fixture 210, and an internal joining projection 252 is formed around the external joining recess 254 in response to the internal joining recess 242. The internal joining projection 252 is formed in a shape of a ring in response to the internal joining recess 242 and projected from the bottom of the transmucosal abutment 250. A second screw hole 258 is formed in the center of the transmucosal abutment 250 in order to pass a first screw 260. The upper abutment 270 is disposed above the transmucosal abutment 250, a crown is fixed on the upper abutment 270, and the upper abutment 270 is fixed on the transmucosal abutment 250, thereby forming an implant structure. A third screw hole. 278 is formed in the center of the upper abutment 270, and a second screw 265 passes the third screw hole 278 to be engaged with the head of the first screw 260. Of course, an external joining structure and an internal joining structure may be applied between the transmucosal abutment 250 and the upper abutment 270. Also, since the sidewall of the internal joining recess 242 is formed to provide an incline toward the top of the flange, the internal joining projection 252 may be snuggly fitted and separated from the internal joining recess 242.

Embodiment 3 FIG. 12 is a perspective view of an impression coping according to a third embodiment of the present invention, and FIG. 13 is a perspective view of a lab analog according to the third embodiment. An impression coping and lab analog shown in FIGS. 12 and 13 are for the fixture 1 10 and abutment 150 described in the previous embodiment and used in a process of manufacturing a prosthesis after implanting the fixture 110 in an alveolar bone. Generally, an impression coping defines position and direction of an implanted fixture in a process of obtaining an impression and is a material fixed to the fixture before obtaining the impression of a tooth using an impression material. Referring to FIG. 12, an impression coping 300 according to the third embodiment includes a coping body 310 and a coping bonding part 320. The coping body 310 is fixed on a fixture as an abutment and includes an external joining recess 314 and an internal joining projection 312 as the same as the abutment of the previous embodiment. The external joining recess 314 in response to an external joining projection of a fixture or lab analog is formed in a shape of a polygonal such as a hexagonal prism and contains the external joining projection to prevent rotation of the impression coping. Also, the internal joining projection 312 is formed around the external joining recess 314. The internal joining projection 312 in response to an internal joining recess assists a stable bonding between a fixture and the impression coping 300. Also, a second screw hole 326 is formed in the impression coping 300 in response to a screw hole of a fixture in order to keep a strong bonding between a fixture and the impression coping 300, and a coping screw 330 may be fixed to the fixture or a lab analog via the second screw hole 326. A coping bonding part includes an undercut 322, and an anti-rotation portion 324 is provided around the undercut 322. The undercut 322 is formed lower than its surroundings. Accordingly, an axial movement of the impression coping 300 is limited by the undercut 322 after an impression of a tooth is obtained using an impression material. Also, the anti-rotation portion 324 formed in a shape of a plane with a partially cut portion is formed around the undercut 322 and prevents rotation of the impression coping 300 in the impression material. Referring to FIG. 13, a lab analog 400 according to the third embodiment is in response to the fixture 110 of the previous embodiment and includes an external joining projection 420, a flange 430, an internal joining recess 432. and a stone bonding part 410. The external joining projection 420 is formed in a shape of a hexagonal prism and includes a first screw hole 422 for bonding the impression coping 300. A coping screw 330 is bonded to the first screw hole 422 via the second screw hole 324 the impression coping 320. The flange 430 is provided below the external joining projection 420. The flange 430 includes the internal joining recess 432 formed around the external joining projection 420, and the internal joining projection 312 of the impression coping 300 is inserted into the internal joining recess 432. A supporting portion 434 having a predetermined width is formed between the end portion of the top of the flange 430 and the internal joining recess 432 in order to support the bottom of the impression coping 300. The stone bonding part 410 is provided below the flange 430. The stone bonding part 410 fixes the lab analog to a stone forming a tooth structure and includes an undercut 412 and anti-rotation portion 414. As described in the description on the impression coping 300, the undercut 412 is formed lower than the flange 430. Accordingly, the lab analog 400 is bonded to the impression coping after an impression is obtained, and the lab analog is filled with a stone and hardened to reproduce a tooth structure of a patient. The lab analog 400 is fixed on a stone model by the undercut 412. Also, the anti-rotation portion 414 formed in a shape of a plane with a partially cut portion is formed around the undercut 412 and prevents rotation of the lab analog 400 in the stone model. FIG. 14 is a partial cross-sectional view illustrating a state in which the impression coping and lab analog according to the third embodiment are bonded together. Referring to FIG. 14, the lab analog 400 is bonded to the impression coping 300 before a stone model is formed, and the impression coping and the lab analog 400 are mutually fixed by the coping screw 330. The external joining recess 314 of the impression coping 300 contains the external joining projection 422 of the lab analog 400, and the internal joining projection 312 of the impression coping 300 is inserted into the internal joining recess 432 of the lab analog 400 to be stably fixed. Also, according to another embodiment of the present invention, a sticking projection formed around an internal joining projection of an impression coping may be provided, and a sticking hole may be formed around the inner side bottom of an internal joining recess of a lab analog in response to the sticking projection. Accordingly, when an impression coping is frequently connected or separated from a lab analog, the sticking projection and sticking hole may assist the connection between the impression coping and lab analog, a position in which the impression coping and lab analog are connected together/to each other may be acquainted, and the impression coping and lab analog may be easily connected or separated. In order to easily bond or separate an internal joining projection of an impression, the internal joining projection with partial section may be formed nonsequentially and partially deformed in the process of inserting or separating from an internal joining recess to easily pass the internal joining recess.

Embodiment 4 FIG. 15 is a perspective view illustrating a fixture for dental implant according to a fourth embodiment of the present invention, and FIG. 16 is a top view of the fixture for dental implant according to the fourth embodiment. Referring to FIGS. 15 and 16, a fixture 510 includes a fixture body 520, a flange 540, an internal joining recess 542, and an external joining projection 530. The fixture body 520 is composed of a titanium alloy, and a screw thread is formed on the outer surface of the body. The fixture body 520 may dig into the osseous tissue using the screw thread and adsorbed to the osseous tissue for long time after enter the osseous tissue. After adhering) to the osseous tissue, the fixture body 520 is formed in a single body with mandible and securely supports the implant, as an artificial dental root. In this case, in addition to make the fixture body 520 implanted, the screw thread functions as a tissue bonding portion to form a wide area adhered to the osseous tissue. A plurality of recesses may be formed at the end portion of the fixture body 520. Also, a surface on which a porosity process is performed may be formed on the fixture body to increase the area adhered to the osseous tissue to the greatest extent possible. For example, in the case of an Endopore implant, an implant has a unique surface structure such as a sintered surface instead of a surface corroded by acid or coated by apatite hydroxide used in other implants, thereby widening the surface of the fixture to obtain strong osseous connection in case that quantity of bone material is not sufficient. The flange 540 is provided above the fixture body 520, and the external joining projection 530 formed in a shape of a straight polygonal prism is provided above the flange 540. In this case, the flange and the external joining recess 530 are formed in a single body with the fixture body 520 and composed of a titanium alloy. The external joining projection 530 is for joining an abutment and formed in a shape of a polygonal prism such as a hexagonal or octagonal prism, in which a first screw hole 538 is formed to a predetermined depth in the center. The external joining projection 530 is for securing the abutment connected by an external connection method and has a width of approximately 0,7mm similar to Branemark implants. The first screw hole 538 may be extended to the fixture body 520 along the axis of the fixture 510 and engaged with a screw 560 penetrating an abutment 550 to fix a crown C and the abutment 550 to the fixture, as shown in FIGS. 17 and 18. The internal joining recess 542 formed in a circular shape is formed around the external joining projection 530 on the flange 540. The internal joining recess 542 is formed to a width of approximately 0.2 to 0.5mm and a depth of approximately 0.6 to 1.0mm and in a circular shape connected into one. Also, a supporting surface 544 having a predetermined width is formed between the top end portion of the flange 540 and the internal joining recess 542. The supporting surface 544 is for supporting the internal joining recess 542 with the bottom of the abutment 550 and may support the bottom of an abutment in the case the abutment mounted above does not include an inter joining projection. A margin portion 546 is provided around the flange 540. Since the margin portion 546 is formed above the flange, its size is determined so that the osseous tissue around the fixture 510 is prevented from sinking down, and a sidewall is sufficient to form the internal joining recess 542. Namely, the fixture 510 according to the present embodiment, as follows, may stably support not only abutments having an internal joining projection but also other conventional abutments by using standards used in Branemark system, 3i system, etc. When a conventional abutment is fixed, the supporting surface 544 at the top of the flange 540 supports the bottom of the abutment. FIG. 17 is an exploded front view illustrating the fixture and an implant according to the first embodiment, and FIG. 18 is a cross-sectional view illustrating a state in which the implant according to the first embodiment is engaged. Referring to FIGS. 17 and 18, an implant 500 includes the fixture 510 and the abutment 550. The abutment 554 is SCRP abutment and includes an external joining recess 554 in response to the external joining projection 530 of the fixture 510. In the present embodiments, since the external joining projection 530 is formed in a shape of a hexagonal prism, the external joining recess 554 provides a groove in the shape of the hexagonal prism. Also, an internal joining projection 552 is formed around the entry of the external joining recess 554 at the bottom of the abutment 550. The internal joining projection 552 is formed in a shape of a ring in response to the internal joining recess 542 and projected from the bottom of the abutment 550. A second screw hole 558 connected to the external joining recess 554 is formed in the center of the abutment 550. A screw 560 is engaged with the first screw hole 538 of the fixture 510. In this case, the abutment 550 bonded to the crown C may be provided to be fixed to the fixture 510 by the screw 560. However, only the abutment 550 is fixed to the fixture 510 by the screw 560, and the crown C is fixed to the abutment using cement. As the present embodiment, in the case the height of the external joining projection 530 is approximately 0.7mm and the depth of the internal joining recess 542 is approximately 0.8mm, connection length between the fixture 510 and the abutment 550 may be increased to double the conventional length. Also, the sidewall of the internal joining recess 542 is formed vertically to the top of the flange 540. However, according to other embodiments of the present invention, at least one of the sidewalls is formed as tapered to be inclined to look upward, and the incline may make it easy to adhere or separate. FIG. 19 is a cross-sectional view illustrating a process of adhering and separating a splinted prosthesis from a conventional fixture, and FIG. 20 is a cross- sectional view illustrating a process of adhering and separating a splinted prosthesis from the fixture according to the fourth embodiment. Referring to FIG. 19, two fixtures 62 are implanted at slight angles, and an external joining projection 63 formed in a shape of a hexagonal prism is formed above the fixture 62. The prosthesis P has a configuration in which a crown 68 is covered above a conventional external abutment 64. The prosthesis P externally processed includes two abutments 64, and the central axis of the abutments 64 is manufactured at angles to match the fixture 62. Since the end of an entry of an external joining recess 65 is located further inward than the end portion of the external joining projection 63 in the abutment 64 in which the central axes are slanted, referring to a double dotted line of (a), the end portion of the external joining recess 65 is fitted into the external joining projection 63. Namely, the prosthesis P including two or more abutments 64 may not be adhered and fixed to the fixture 62 implanted at an angle. Of course, although a fixture is forcibly pulled such that the prosthesis P may pass, there is a risk that bonding between the fixture and surrounding tissue may be destroyed. Also, as follows, in order to manufacture a precise prosthesis P, a prosthesis should be severally connected or separated from a lab analog fixed to a stone. According to a conventional configuration, engagement and separation are mutually limited to make a process difficult. Then, a screw-retained prosthesis is used to fix a prosthesis to one fixture and is not used to form a splinted prosthesis. Of course, a prosthesis splinted using a cement retained prosthesis may be fixed on the fixture, but a prosthesis P once fixed may not be easily separated for that reason (refer to (b) of FIG. 20). FIGS. 21 and 22 are top views illustrating fixtures according to other embodiments of the present invention. Referring to FIG. 21, an internal joining recess 543 is formed on the flange 540 nonsequentially. Different from the previous embodiment, the internal joining recess 543 has a shape nonsequentially formed as regularly or irregularly fored. As shown in FIG. 21, since the internal joining recess 543 is formed nonsequentially, a direction in which an abutment is mounted may be easily defined and the supporting surface 544 may be widely secured. Referring to FIG. 22, an internal joining recess 543-2 is formed on the flange 540 nonsequentially. The internal joining recess 543-2 is formed adjacent to the side bottom of the external joining projection 530 formed in a shape of a hexagonal prism. In the present embodiment, the three internal joining recesss 543-2 are formed at an interval of 120° respectively. However, six internal joining recesss may be formed at an interval of 60°. Since the internal joining recess 543-2 is formed nonsequentially, a direction in which an abutment is mounted may be easily defined. Also, as shown in FIG. 22, since the internal joining recess 543-2 is closely adjacent to the external joining projection 530 to stick an inner side of the internal joining recess 543-2 to the outer surface of the external joining projection 530, the supporting surface 544 for supporting an abutment may be widely provided. Particularly, it is difficult for a fixture of a small size to be secured to a space to provide the internal joining recess 543-2. However, in the present embodiment, the internal joining recess 543-2 is formed nonsequentially and adjacent to the external joining projection 530, thereby being secured to a wide space.

Embodiment 5 FIG. 23 is an exploded front view illustrating a dental implant according to a fifth embodiment of the present invention. Referring to FIG. 23, an implant 600 according to the fifth embodiment includes a fixture 610 and an abutment assembly, and the abutment assembly includes a transmucosal abutment 650 and an upper abutment 670. The fixture 610 includes a fixture body 620, a flange 640, an internal joining recess 642, and an external joining projection 630. The fixture body 620 is composed of a titanium alloy, and a tissue bonding portion is formed on the outer surface of the fixture body. The tissue bonding portion may include a screw thread or a surface on which a porosity process is performed, and a plurality of recesses may be formed on the end portion of the fixture body 620. The flange 640 is provided above the fixture body 620, and the external joining projection 630 formed in a polygonal prism shape is provided above the flange 640. In this case, the flange 640 and the external joining projection 630 are formed in a single body with the fixture body 620 and composed of a titanium alloy. The external joining projection 630 is for bonding an abutment and formed in a polygonal shape such as a hexagonal or octagonal prism, in which a screw hole is formed to a predetermined depth in the center. The external joining projection 630 fixes the transmucosal abutment 650 connected by an external connection method and follows a Branemark system. The internal joining recess 642 formed in a circular shape is formed around the external joining projection 630 above the flange 640. The internal joining recess 642 is formed of a circle connected to one, and a supporting surface 644 having a predetermined width is formed between the end portion of the top of the flange 640 and the internal joining recess 642. A micro unevenness is formed around the side of the flange 640. The micro unevenness 649 forms a plurality of unevennesses along the circumference of the flange 640, may be easily adsorbed into the surrounding gingival tissue, and may prevent the surrounding gingival tissue from drooping down by the passage of time. Like the fourth embodiment, a margin portion 646 is provided around the flange 640. Since the margin portion 646 is formed on the flange having a determined size, the drooping down of osseous tissue around the fixture 610 over time may be prevented and a sidewall sufficient to form the internal joining recess may be provided. The transmucosal abutment 650 is a SCRP abutment, an internal joining recess 654 is formed around the bottom of the transmucosal abutment 650 in response to the external joining projection 630 of the fixture 610, and an internal joining projection 652 is formed around the external joining recess 654 in response to the internal joining recess 642. The internal joining projection 652 is formed in a shape of a ring in response to the internal joining recess 642 and projected from the bottom of the transmucosal abutment 650. A second screw hole 658 is formed in the center of the transmucosal abutment 650 in order to pass a first screw 660. The upper abutment 670 is disposed above the transmucosal abutment 650, a crown is fixed on the upper abutment 670, and the upper abutment 670 is fixed on the transmucosal abutment 650, thereby forming an implant structure. A third screw hole 678 is formed in the center of the upper abutment 670, and a second screw 665 passes the third screw hole 678 to be engaged with the head of the first screw 660. Of course, an external joining structure and an internal joining structure may be applied between the transmucosal abutment 650 and the upper abutment 670. Also, since the sidewall of the internal joining recess 642 is formed to provide an incline toward the top of the flange, the internal joining projection 652 may be snuggly fitted and separated from the internal joining recess 642.

Embodiment 6 FIG. 24 is a perspective view of an impression coping according to a sixth embodiment of the present invention, and FIG. 25 is a perspective view of a lab analog according to the sixth embodiment. An impression coping and lab analog shown in FIGS. 24 and 25 are for the fixture 510 and abutment 550 described in the previous embodiment and used in a process of manufacturing a prosthesis after implanting the fixture 510 in an alveolar bone. Generally, an impression coping defines position and direction of an implanted fixture in a process of obtaining an impression and is a material fixed on the fixture before obtaining the impression of a tooth using an impression material. Referring to FIG. 24, an impression coping 700 according to the third embodiment includes a coping body 710 and a coping bonding part 720. The coping body 710 is fixed on the fixture as an abutment and includes an external joining recess 724 and an internal joining projection 722, the same as the abutment of the previous embodiment. The external joining recess 724 in response to an external joining projection of a "fixture or lab analog is formed in a shape of a polygon such as a hexagonal prism and contains the external joining projection to prevent rotation of the impression coping. Also, the internal joining projection 722 is formed around the external joining recess 724. The internal joining projection 722 in response to an internal joining recess assists a stable bonding between a fixture and the impression coping 700. Also, a second screw hole 726 is formed in the impression coping 700 in response to a screw hole of a fixture in order to keep a strong bond between a fixture δ and the impression coping 700, and a coping screw 730 may be fixed on the fixture or a lab analog via the second screw hole 726. A coping bonding part includes an undercut 722, and an anti-rotation portion 724 is provided around the undercut 722. The undercut 722 is formed lower than its surroundings. Accordingly, an axial movement of the impression coping 700 is 0 limited by the undercut 722 after an impression of a tooth is obtained using an impression material. Also, the anti-rotation portion 724 formed in a shape of a plane with a partially cut portion is formed around the undercut 722 and prevents rotation of the impression coping 700 in the impression material. Referring to FIG. 25, a lab analog 800 according to the third embodiment is in 5 response to the fixture 510 of the previous embodiment and includes an external joining projection 820, a flange 830, an internal joining recess 872, and a stone bonding part 810. The external joining projection 820 is formed in a shape of a hexagonal prism and includes a first screw hole 822 for bonding the impression coping 700. A coping screw 730 is bonded to the first screw hole 822 via the second screw hole 724 the impression coping 720. The flange 830 is provided below the external joining projection 820. The flange 830 includes the internal joining recess 872 formed around the external joining projection 820, and the internal joining projection 722 of the impression coping 700 is inserted into the internal joining recess 872. A supporting portion 874 having a predetermined width is formed between the end portion of the top of the flange 830 and the internal joining recess 872 in order to support the bottom of the impression coping 700. The stone bonding part 810 is provided below the flange 830. The stone bonding part 810 fixes the lab analog to a stone forming a tooth structure and includes an undercut 822 and anti-rotation portion 824. As described in the description on the impression coping 700, the undercut 822 is formed lower than the flange 830. Accordingly, the lab analog 800 is bonded to the impression coping after an impression is obtained, and the lab analog is filled with a dental stone and hardened to reproduce a tooth structure of a patient. The lab analog 800 is fixed on a stone model by the undercut 822. Also, the anti-rotation portion 824 formed in a shape of a plane with a partially cut portion is formed around the undercut 822 and prevents rotation of the lab analog 800 in the stone model. FIG. 26 is a partial cross-sectional view illustrating a state in which the impression coping and lab analog according to the third embodiment are bonded together. Referring to FIG. 26, the lab analog 800 is bonded to the impression coping 700 before a stone model is formed, and the impression coping and the lab analog 800 are fixed to each other by the coping screw 730. The external joining recess 724 of the impression coping 700 contains the external joining projection 822 of the lab analog 800, and the internal joining projection 722 of the impression coping 700 is inserted into the internal joining recess 872 of the lab analog 800 to be securely fixed. Also, according to another embodiment of the present invention, a sticking projection formed around an internal joining projection of an impression coping may be provided, and a sticking hole may be formed around the inner side bottom of an internal joining recess of a lab analog in response to the sticking projection. Accordingly, when an impression coping is frequently connected or separated from a lab analog, the sticking projection and sticking hole may assist connection between the impression coping and lab analog, a position in which the impression coping and lab analog are mutually connected may be acquainted, and the impression coping and lab analog may be easily connected or separated. In order to easily bond or separate an internal joining projection of an impression, the internal joining projection with partial section may be formed , nonsequentially and partially deformed in a process of inserting or separating from an internal joining recess to easily pass the internal joining recess. According to the present invention, a fixture of a dental implant may solve problems of external connection methods by adopting merits of internal implants based on external connection methods. Namely, an area in which a fixture contacts an abutment may be increased and a joined length may be increased by using the join between an internal joining recess and internal joining projection. Accordingly, a fixture and abutment may be stably joined with each other. Also, since a structure of other external fixture such as a conventional Branemark system, 3i system, etc., may be used in an external joining projection of a fixture, a conventional abutment without an internal joining recess may be fixed with no problem. Particularly, when several artificial teeth are splinted to be repaired, a conventional abutment using a Branemark or 3i method may be used. Of course, a fixture and abutment manufactured according to the present invention are used, thereby respectively manufacturing a single crown when two or more teeth are repaired and obtaining optimum effects. Particularly, since an abutment which is most widely used at the present time may be applied in the case an abutment with an internal joining projection does not exist, a conventional abutment may be safely used in the case optimum components fitting a fixture are difficult to find, such as when traveling abroad. For example, since most fixtures and abutments are manufactured according to mutually unique methods, there were a lot of cases in which the procedure itself is impossible when purchasing components is difficult as described above. Also, the structure described above has an economic advantage because that conventional instruments or kits may be used in procedure of impression coping or other implanting process. Dentists apply all merits of external joining method and internal joining method and obtain optimum effects by using an abutment manufactured in response to a fixture. 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.