JP6071420B2 - Screw member for living body - Google Patents

Description

  The present invention relates to a biological screw member having a screw portion that is screwed to a bone.

  2. Description of the Related Art Conventionally, there has been known a biomedical screw member that is screwed and embedded in a bone or tooth that is lost or damaged due to an accident or the like. For example, Patent Document 1 discloses an implant (biological screw member) including a head portion, an intermediate portion containing a porous metal, and a stem portion. These are separate at the initial stage. The implant is formed by sandwiching the intermediate part by the cooperation of the head part and the stem part. Thus, by including a porous metal in the middle, the implant increases resistance to torsion or rotation, allowing immediate or very early loading. In addition, since bone grows and enters into the hole in the intermediate portion, long-term stability is increased.

  Patent Document 2 discloses a bone screw configured as a hollow screw having a porous layer on the surface.

Special table 2011-526809 gazette JP-T-2-500490

  By the way, when an implant is formed by fitting a plurality of members (a head portion, an intermediate portion, a stem portion) to each other as in Patent Document 1, there is a possibility that the boundary surface of the joined portion is loaded and damaged. Occurs. In addition, since there is no screw thread in the middle part, there is a case where a sufficient holding force of the implant cannot be secured in the initial state where the implant is fixed to the jawbone.

  Moreover, since the porous layer formed in the bone screw described in Patent Document 2 is formed by sandblasting or plasma irradiation, the surface has an uneven shape. However, this bone screw has an uneven shape only on the surface as described above, and it is difficult for the grown bone to enter the inside of the surface of the bone screw, so that the bonding force between the bone and the bone screw is sufficient. There is a possibility that it cannot be secured.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a biomedical screw member that has a low risk of breakage and can sufficiently secure a binding force to bone.

In order to achieve the above object, a living body screw member according to an aspect of the present invention relates to a living body screw member having a screw portion screwed into a bone. The tip portion of the screw portion is provided as a tip side screw portion formed of a dense body, and the intermediate portion in the axial direction of the screw portion is at least part of the inside from at least part of the surface of the intermediate portion. Is provided as an intermediate screw portion that is formed of a porous body that is a sparser structure than the dense body of the tip side screw portion, and the tip side screw portion and the intermediate screw portion are integrated with each other. The intermediate screw portion is formed of a dense body and is a central portion that is a central portion in the radial direction of the intermediate screw portion, and a center portion of the intermediate screw portion that is formed of a dense body from the top of the screw thread in the intermediate screw portion. A dense portion that is a portion extending from a portion, and a porous body, the portion extending from the thread hem portion to the center portion in the intermediate screw portion, and the center from the bottom portion of the screw groove of the intermediate screw portion Across It has portions, and the porous section is, the.

  In this configuration, the tip side screw portion formed of a dense body and the intermediate screw portion including the porous body are integrated. If it carries out like this, unlike the case where the front end side screw part and intermediate | middle screw part which were formed separately are assembled and assembled, there will be no coupling | bond part used as a boundary between both. As a result, stress concentration is less likely to occur in the region between the two, and the screw portion is less likely to be damaged. Accordingly, it is possible to form a biological screw member with little risk of breakage.

  Further, the tip side screw part and the intermediate screw part are integrated by melting and solidifying each time the metal powder is laminated. For this reason, it is not necessary to perform complicated cutting etc. with respect to a metal and to form the screw member for living bodies. Further, even a difficult-to-cut material such as a titanium alloy that is widely distributed as a material for medical instruments does not require a complicated-shaped cutting process, and thus a biological screw member can be easily formed. Therefore, the biomedical screw member provided with the front-end | tip side screw part comprised by the precise | minute body and the intermediate | middle screw part which has a porous body can be integrally formed easily.

  In addition, since at least a part of the surface of the intermediate screw portion is made of a porous body, a large frictional force can be secured between the intermediate screw portion and the bone. Therefore, it is possible to improve the fixing performance for obtaining the fixing force with respect to the bone, and to secure sufficient fixing performance. Furthermore, since the thread portion is formed in the intermediate screw portion, the fixing force to the bone can be further increased.

  In addition, by forming a part extending from at least a part of the surface of the intermediate screw part to at least a part of the inside with a porous body, in the long term, the bone can grow so as to enter the pores of the porous body. become. Thereby, it is easy to promote the fusion with the bone, and the long-term fixing performance to the bone can be improved.

  Moreover, in the above-mentioned structure, the porous body is formed by melting and solidifying each time the metal powder is laminated. In this way, the porous body can be easily formed not only on the surface of the intermediate screw part but also on the inside. Therefore, since the bone can penetrate deeply into the porous body and grow, the long-term fixing performance to the bone can be further increased.

  Further, in the above-described configuration, the tip side screw portion, which is relatively easily loaded when the screw portion is screwed into a bone or the like, is formed of a dense body having a relatively high strength. If it carries out like this, when screwing a screw part in a bone etc., the risk that this screw part will be damaged can be reduced.

  Therefore, with the above-described configuration, it is possible to provide a biomedical screw member that has a low risk of breakage and can sufficiently secure a binding force to bone.

  In the screw member for living body, a portion of the intermediate screw portion that is formed of a porous body is formed from the surface of the intermediate screw portion toward the radial center of the cross section perpendicular to the axis of the intermediate screw portion. It is preferable that the body has a low porosity.

  According to this configuration, the porosity of the portion formed of the porous body in the intermediate screw portion is from the surface of the intermediate screw portion to the radial center side of the cross section perpendicular to the axis of the intermediate screw portion, that is, the intermediate screw portion. It becomes small in a stepwise or stepwise manner toward the axial center side. If it carries out like this, since it can suppress that the structure | tissue structure of the part comprised with the porous body among the intermediate | middle screw parts changes rapidly, it can be made the structure which a stress concentration does not occur easily in an intermediate | middle screw part.

  Further, the porosity of the porous body is such that the portion on the surface side of the intermediate screw portion, that is, the bone side portion (the outer peripheral portion of the screw portion) in the intermediate screw portion is more than the portion on the axis side in the intermediate screw portion. Since it is large, it is possible to secure a sufficient space for the bone to enter and grow inside the intermediate screw portion after the screw portion is screwed into the bone.

  In the biomedical screw member, it is preferable that the tip side screw portion has an outer diameter larger than that of the intermediate screw portion.

  When the screw part is screwed to the bone, the screw part advances inside the bone while the screw thread of the tip side screw part forms a screw hole in the bone. That is, the screw thread of the intermediate screw part advances inside the screw hole formed by the tip side screw part. As described above, when the outer diameter of the tip side screw portion is larger than the outer diameter of the intermediate screw portion, a gap is formed between the intermediate screw portion and the screw hole. Therefore, since the load concerning an intermediate | middle screw part can be made small, the risk that an intermediate | middle screw part will be damaged can be reduced.

  In the biomedical screw member, it is preferable that the surface of the intermediate screw portion is formed of a porous body throughout.

  According to this configuration, a sufficient bone growth space in the intermediate screw portion can be ensured, so that a long-term coupling force between the screw portion and the bone can be increased.

  In the biomedical screw member, it is preferable that a top portion of the thread of the intermediate screw portion is formed of a dense body, and a bottom portion of the screw groove of the intermediate screw portion is formed of a porous body.

  In this configuration, since the top of the thread that is relatively easily loaded in the intermediate screw part is formed of a dense body, damage to the thread of the intermediate screw part can be suppressed. Moreover, since the bottom of the screw groove is made of a porous body, a bone growth space can be secured.

  In the screw member for a living body, a portion of the screw portion opposite to the tip-end-side screw portion is provided as a base-end-side screw portion configured by a dense body, and the base-end-side screw portion is provided on the tip-end side. It is preferable that an outer diameter is larger than a thread part and the said intermediate | middle thread part.

  According to this configuration, in a state where the biological screw member is mounted on the bone, the proximal-side screw portion is screwed into the cortical bone having high strength. Thus, by providing the proximal-side screw portion that is screwed into a portion having high strength in the bone, the entire screw portion can be firmly fixed to the bone. Moreover, the proximal-side screw portion has a larger outer diameter than the distal-end side screw portion and the intermediate screw portion. In this way, when screwing the screw portion into the bone, the proximal-side screw portion advances while threading the screw hole formed by the distal-end screw portion and the intermediate screw portion, and is screwed into the cortical bone. Accordingly, the proximal-side screw portion can be more reliably fixed to the bone.

  According to the present invention, it is possible to provide a biomedical screw member that has a low risk of breakage and can sufficiently secure a binding force to bone.

It is sectional drawing which shows the state which the bone screw which concerns on 1st Embodiment has screwed with respect to the bone. It is a figure which shows the structure of the bone screw which concerns on 1st Embodiment, (A) is a front view of a bone screw, (B) is sectional drawing of a bone screw. It is a schematic diagram of the manufacturing system for manufacturing a bone screw. It is a figure for demonstrating the process by the manufacturing system shown in FIG. 3, Comprising: It is a schematic diagram which shows the setting value of the irradiation amount of the laser beam of each part in a part of one layer image. It is a flowchart for demonstrating the manufacturing process of the bone screw shown in FIG. It is a schematic diagram which shows typically the manufacturing process of the bone screw shown in FIG. It is a figure which shows the structure of the bone screw which concerns on 2nd Embodiment, (A) is a front view of a bone screw, (B) is sectional drawing of a bone screw. It is a perspective view which shows the state which the artificial tooth root which concerns on 3rd Embodiment is screwing with respect to a jawbone. It is a figure which shows the structure of the artificial tooth root which concerns on 3rd Embodiment, (A) is a front view of an artificial tooth root, (B) is sectional drawing of an artificial tooth root. It is a figure which shows the structure of the artificial tooth root which concerns on a modification, (A) is a front view of an artificial tooth root, (B) is sectional drawing of an artificial tooth root.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention can be widely applied as a biomedical screw member that is screwed into and embedded in a defect or damaged bone.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a state in which a bone screw 1 as a living body screw member according to the first embodiment is screwed into a bone 50 such as a femur. The bone screw 1 is for joining a fractured portion 51 in the bone 50. As shown in FIG. 1, in the first embodiment, the two bone screws 1, 1 are screwed into the bone 50. Each bone screw 1 is screwed and embedded in the bone 50 so as to straddle the fracture portion 51 which is a damaged portion of the bone, whereby the fracture portion 51 can be fixed.

-Bone screw configuration-
2A and 2B are diagrams showing the configuration of the bone screw 1, where FIG. 2A is a front view of the bone screw 1, and FIG. 2B is a cross-sectional view of the bone screw 1.

  The bone screw 1 according to the present embodiment is a so-called self-tapping screw that advances inside the bone 50 while cutting a screw with respect to the bone 50. In the present embodiment, the bone screw 1 fixes a bone head 53 separated from the bone main body 52 by a fracture to the bone main body 52. Specifically, the bone screw 1 is screwed from the bone main body 52 side toward the bone head 53 side. The bone screw 1 has a proximal end portion in the axial direction screwed into the bone main body 52 and a distal end portion in the axial direction screwed into the bone head 53. Thereby, the bone head 53 is fixed to the bone main body 52. The bone screw 1 is composed of a metal having a biocompatibility, for example, a metal material such as titanium, titanium alloy, cobalt chromium alloy, and stainless steel that has been approved as a medical device for living implants. As shown in FIG. 2, the bone screw 1 includes a head portion 2 and a screw portion 10 that are integrally formed.

  The head 2 is formed in a slightly flat columnar shape in the vertical direction, and a concave portion 3 into which a bit of a tool (driver or the like) for tightening a screw is fitted is formed in the top of the head. The head 2 is composed of a dense body having a relatively high density. In the present embodiment, the dense body refers to a structure having substantially no pores therein, for example, a structure having a porosity of less than several percent (including zero percent). Here, the porosity is defined as a value obtained by multiplying the value obtained by dividing the volume B of the pore (space) in the unit volume A by the unit volume A by 100. That is, it can be expressed as porosity = (B / A) × 100.

  The screw portion 10 is formed in a rod shape that extends downward from the bottom surface of the head 2, and a helical thread is formed on the outer peripheral surface thereof. The threaded portion 10 includes a distal end side threaded portion 11, an intermediate threaded portion 12, and a proximal end side threaded portion 13.

  The distal end side screw portion 11 is a portion on the distal end side of the screw portion 10, that is, a portion on the opposite side to the head 2 in the bone screw 1. The front end side screw portion 11 is formed of a dense body like the head portion 2. The density of the front end side screw portion 11 is substantially uniform over the entire front end side screw portion 11 and is substantially the same as that of the head portion 2.

  The intermediate screw portion 12 is an intermediate portion in the axial direction of the screw portion 10, that is, a portion between the distal end side screw portion 11 and the proximal end side screw portion 13 in the screw portion 10. The intermediate screw portion 12 includes a dense portion 15 and a porous portion 16. The dense portion 15 is a portion near the axial center of the intermediate screw portion 12. Specifically, the dense portion 15 is a cylindrical portion whose axis is concentric with the axis of the intermediate screw portion 12 and is elongated in the axial direction. The porous portion 16 is a portion of the intermediate screw portion 12 excluding the dense portion 15, specifically, a portion on the surface side of the intermediate screw portion 12.

  The dense portion 15 is formed of a dense body having a relatively high density, similar to the tip side screw portion 11. The density of the dense portion 15 is substantially the same as the density of the head 2 and the tip side screw portion 11. On the other hand, the porous portion 16 is composed of a porous body that is a structure that is sparser than the dense body constituting the dense portion 15. The porosity of the porous portion 16 decreases gradually or stepwise from the surface of the intermediate screw portion 12 toward the axis.

  Further, the outer diameter of the intermediate screw portion 12 is the same as the outer diameter of the tip side screw portion 11. Further, the pitch of the intermediate screw portion 12 is the same as the pitch of the tip side screw portion 11.

  The proximal side screw part 13 is a part of the screw part 10 closest to the head 2 side. In other words, the proximal end screw portion 13 is a portion of the screw portion 10 on the side opposite to the distal end screw portion 11. The proximal end screw portion 13 is formed of a dense body having substantially the same density as the head portion 2 and the distal end side screw portion 11. The base end side screw part 13 has a uniform density throughout.

  In addition, the proximal end screw portion 13 has the same outer diameter as the distal end screw portion 11 and the intermediate screw portion 12. Further, the pitch of the proximal-side screw portion 13 is the same as the pitch of the distal-side screw portion 11 and the intermediate screw portion 12.

  In the state where the bone screw 1 is screwed to the bone 50, the proximal screw portion 13 is screwed to the cortical bone 50a, and the intermediate screw portion 12 and the distal screw portion 11 are screwed to the cancellous bone 50b.

-Bone screw manufacturing system-
The bone screw 1 manufacturing system according to the present embodiment is configured to form an integrated bone screw 1 by melting and solidifying each time metal powder having biocompatibility is laminated. That is, the bone screw 1 is integrally formed by a metal powder additive manufacturing method such as a selective laser melting method.

  As described above, the bone screw 1 according to this embodiment includes a dense body and a porous body. In the bone screw 1 manufacturing system according to the present embodiment, the metal powder is melted by the laser beam applied to the metal powder supplied onto the movable table 26 and then solidified. The porosity of the metal thus solidified is adjusted by adjusting the irradiation amount of the laser beam.

  FIG. 3 is a schematic diagram of a manufacturing system 20 for manufacturing the bone screw 1. As shown in FIG. 3, the manufacturing system 20 includes a CAD (Computer Aided Design) device 21, a data conversion device 22, and a manufacturing device 23.

  The CAD device 21 is, for example, a 3D-CAD device that can display an image three-dimensionally on a screen. In the present embodiment, the CAD device 21 includes a computer and software installed in the computer. The designer of the bone screw 1 creates CAD data (image data) for creating the bone screw 1 by operating the CAD device 21. The CAD data created by the CAD device 21 is output to the data conversion device 22.

  The data conversion device 22 is provided as a device that converts CAD data into data for operating the manufacturing device 23. In the present embodiment, the data conversion device 22 includes a computer and software installed on the computer. The data converter 22 divides, for example, a three-dimensional image of the bone screw 1 specified by the CAD data into a plurality of layer images (two-dimensional images) obtained by slicing at predetermined intervals along a predetermined direction. Then, the data of the plurality of layer images is held. Said predetermined direction is set as a direction perpendicular | vertical with respect to the axial center of the bone screw 1, for example. Further, the predetermined interval corresponds to the thickness of one layer of metal powder to be laminated in the manufacturing apparatus 23, and is, for example, about 30 μm. The data of the plurality of layer images is given to the manufacturing apparatus 23.

  The manufacturing apparatus 23 includes a laser light source 24, a control unit 25, a movable base 26, and a powder supply unit 27.

  The laser light source 24 is provided to give thermal energy to the metal powder. In the present embodiment, the laser light source 24 is a Yb (ytterbium) fiber laser light source. The laser beam from the laser light source 24 may be irradiated to a desired position of the metal powder by the laser light source 24 itself being displaced using a driving device (not shown), or the laser light source 24 is fixed. In a state, a desired position may be irradiated using a galvanometer mirror. The laser light source 24 is controlled by the control unit 25.

  The control unit 25 includes a CPU, a RAM, a ROM, and the like, and receives data from the data conversion device 22. The control unit 25 controls the laser light source 24, the movable table 26 and the powder supply unit 27. More specifically, the control unit 25 determines the irradiation amount of the laser beam to the predetermined portion of the metal powder based on the image data given from the data conversion device 22, and based on the determined irradiation amount, the metal A laser beam is irradiated to a predetermined portion of the powder. Note that the irradiation amount of the laser beam may be set by the data converter 22.

  FIG. 4 is a diagram for explaining processing by the control unit 25 for setting the irradiation amount of the laser beam to a predetermined portion of the metal powder, and shows the irradiation amount of the laser beam of each part in a part of one layer image. It is a schematic diagram which shows a setting value. FIG. 4 shows a part of a layer image showing a cross section of the intermediate screw portion 12 of the bone screw 1. More specifically, FIG. 4 is an enlarged view of a portion near the boundary between the dense portion 15 and the porous portion 16 in the layer image of the cross section taken along the line AA in FIG. It shows.

  As shown in FIG. 4, the layer image is composed of a plurality of pixels. Each pixel is set to a size corresponding to the minimum unit area that can be irradiated with a laser beam at one time, for example. In FIG. 4, the relationship between the size of the pixel and the size of the bone screw 1 is schematically shown. As described above, the bone screw 1 is formed by varying the melting amount of the metal powder depending on the location. For this reason, in the layer image data, the laser beam irradiation amount is set for each pixel.

  In the present embodiment, the head 2 of the bone screw 1, the distal end side screw portion 11, the portion near the axial center (the dense portion 15), and the proximal end side screw portion 13 of the intermediate screw portion 12 are substantially formed with pores. It is composed of a dense body that is not made. In order to form such a dense body, it is necessary to sufficiently melt the metal powder to such an extent that no pores are formed. For this reason, in the layer image shown in FIG. 4, the irradiation amount (irradiation energy per unit time) of the region 31 corresponding to the dense portion 15 of the intermediate screw portion 12 is set to the largest value in the layer image. Has been. In the layer image shown in FIG. 4, the hatched hatching is applied to the pixels irradiated with the laser beam, and the setting value of the laser beam irradiation amount is larger as the hatched hatching interval is shorter. Show.

  The porous portion 16 is set so that the porosity increases from the portion adjacent to the dense portion 15 to the outer peripheral side of the intermediate screw portion 12. For this reason, in FIG. 4, the form by which the porous part 16 is comprised by the part of three area | regions (32, 33, 34) from which a porosity differs is illustrated. A portion of the region 32 in the porous portion 16 adjacent to the portion of the region 31 that is the dense portion 15 is configured as a portion having the smallest porosity in the porous portion 16. For this reason, the melting amount of the metal powder when forming the portion of the region 32 is set larger next to the melting amount of the metal powder when forming the portion of the region 31. Therefore, in the layer image shown in FIG. 4, the set value of the laser beam irradiation amount to the region 32 is set to be the second largest after the region 31.

  And the part of the area | region 33 adjacent to the part of the area | region 32 in the porous part 16 is comprised as a part with a larger porosity than the part of the area | region 32 in the porous part 16. FIG. For this reason, the melting amount of the metal powder when forming the portion of the region 33 is set smaller than the melting amount of the metal powder when forming the portion of the region 32. Therefore, in the layer image shown in FIG. 4, the set value of the laser beam irradiation amount to the region 33 is set smaller than that of the region 32.

  Furthermore, the portion of the region 34 adjacent to the portion of the region 33 in the porous portion 16 is the outermost portion of the intermediate screw portion 12 and is configured as the portion having the highest porosity in the porous portion 16. . For this reason, the melting amount of the metal powder when forming the region 34 is set to be the smallest in the porous portion 16. Therefore, in the layer image shown in FIG. 4, the setting value of the irradiation amount of the laser beam to the region 34 is set to the smallest.

  In the layer image shown in FIG. 4, pixels that are not hatched indicate regions that are not irradiated with the laser beam. Although one layer has been described with reference to FIG. 4, in each layer image as well, the laser beam irradiation amount is appropriately set for each pixel, as described above.

  In the above description, the porous portion 16 is configured by three regions (32, 33, 34) having different porosities. However, this need not be the case. The form by which the porous part 16 is comprised by the part of the 2 or less area | region from which a porosity differs, or the part of 4 or more area | region may be implemented. Moreover, in the porous part 16, the form by which the magnitude | size and arrangement | positioning of the part of the area | region from which a porosity differs are variously changed may be implemented.

  The metal powder irradiated with the laser beam is placed on the movable table 26 (see FIG. 3). The movable table 26 is provided to hold the metal powder. The movable base 26 has, for example, a substantially horizontal upper surface, and metal powder is placed on the upper surface. The movable base 26 has a drive mechanism (not shown) and can be displaced along the vertical direction perpendicular to the upper surface. Metal powder is supplied from the powder supply unit 27 to the movable table 26.

  The powder supply unit 27 includes a storage unit that stores the metal powder and a supply unit that supplies the metal powder onto the movable base 26. The powder supply unit 27 forms a metal powder layer having a thickness (in this embodiment, 30 μm) corresponding to the above-described predetermined interval on the movable table 26.

-Bone screw manufacturing process-
Next, the process of manufacturing the bone screw 1 will be described with reference to FIG. FIG. 5 is a flowchart for explaining the manufacturing process of the bone screw 1. When manufacturing the bone screw 1, first, the designer creates CAD data of the bone screw using the CAD device 21 (step S1).

  The CAD data of the bone screw 1 is output to the data conversion device 22 in response to, for example, the designer operating the CAD device 21 (step S2). The data conversion device 22 divides the image of the bone screw 1 specified by the CAD data into a plurality of layers for each predetermined thickness, and outputs the image data of each layer to the control unit 25 of the manufacturing device 23 (step). S3). The control unit 25 reads the image data of each layer, and sets the irradiation amount of the laser beam to each pixel of each layer (step S4).

  Next, the control unit 25 drives the powder supply unit 27. Thereby, the powder supply part 27 forms the metal powder layer 41 of the predetermined thickness (30 micrometers in this embodiment) mentioned above on the upper surface of the movable stand 26, as shown to Fig.6 (a) (step S5). . That is, a metal powder is prepared. Next, the control unit 25 drives the laser light source 24. Accordingly, the laser light source 24 irradiates a predetermined portion of the metal powder layer 41 with a predetermined amount of laser light according to the irradiation amount of the laser light set by the control unit 25 (step S6). Thereby, as shown in FIG. 6B, a part of the metal powder layer 41 is once melted, and the melted part is solidified and integrated.

  Next, the control unit 25 determines whether or not the work of once melting and integrating the metal powder is performed for all layers as described above (step S7). When this operation is not completed (No in step S7), the control unit 25 drives the movable table 26 and displaces the movable table 26 downward by the same value as the thickness of the metal powder layer 41 (step S8). .

  The control unit 25 drives the powder supply unit 27 again. Thereby, the powder supply part 27 forms a metal powder layer again (step S5). Next, the control unit 25 drives the laser light source 24. Thereby, the laser light source 24 irradiates a predetermined amount of the laser beam to a predetermined portion of the metal powder layer according to the irradiation amount of the laser beam set by the control unit 25 (step S6). Thereby, a part of the metal powder layer is once melted, and the melted part is solidified and integrated. Thus, the bone screw 1 is formed by varying the melting amount of the metal powder depending on the location.

  In the manufacturing apparatus 23, step S5 to step S8 are repeated until the operation of once melting and integrating the metal powder is performed for all layers. Accordingly, as shown in FIG. 6C, the metal powder layers n, n + 1, n + 2,... (N is a positive integer) are laminated, and the bone screw 1 is formed. And the dense part 15 corresponding to the area | region 31 in the layer image of FIG. 4 among the bone screws 1 is formed. Moreover, the porous part 16 corresponding to the area | region (32, 33, 34) in the layer image of FIG. 4 among the bone screws 1 is formed. In addition, in FIG.6 (c), the code | symbol of the area | region (31-34) is also shown typically.

  When it is determined by the control unit 25 that the work of once melting and integrating the metal powder has been performed for all layers (Yes in step S7), the work is completed and post-processing is performed (step S9). In the present embodiment, the post-processing includes a process of removing the bone screw 1 formed on the movable table 26 from the movable table 26 and removing unnecessary metal powder attached to the bone screw 1 from the bone screw 1. This removal process includes, for example, a process of ultrasonically cleaning the bone screw 1 using 2-propanol, pure water, or the like. Moreover, in this embodiment, a post-processing process includes the machining process performed after said removal process. In this machining process, the surface portion of the bone screw 1 is appropriately ground or polished. The bone screw 1 is completed through these post-processing steps.

[effect]
As described above, in the bone screw 1 according to the present embodiment, the distal end side screw portion 11 formed of a dense body and the intermediate screw portion 12 including a porous body are integrated. If it carries out like this, unlike the case where the front end side screw part and intermediate | middle screw part which were formed separately are assembled and assembled, there will be no coupling | bond part used as a boundary between both. As a result, stress concentration is less likely to occur in the region between the two, so that the screw portion 10 is less likely to be damaged. Therefore, the bone screw 1 with less risk of breakage can be formed.

  Further, the bone screw 1 according to the present embodiment is integrated by melting and solidifying the distal-side screw portion 11 and the intermediate screw portion 12 each time the metal powder is laminated. For this reason, it is not necessary to perform a complicated cutting process etc. with respect to a metal and to form a bone screw. Moreover, even if it is a difficult-to-cut material such as a titanium alloy that is widely distributed as a material for medical instruments, it is possible to easily form the bone screw 1 because a complicated shape cutting process is unnecessary. Therefore, the bone screw 1 provided with the front end side screw portion 11 formed of a dense body and the intermediate screw portion 12 having a porous body can be easily formed integrally.

  Moreover, since the surface of the intermediate | middle screw part 12 is comprised by the porous body over the whole, the bone screw 1 which concerns on this embodiment can ensure a big friction force between the bones 50. FIG. Therefore, the fixing performance for obtaining the fixing force with respect to the bone 50 can be improved, and sufficient fixing performance can be ensured. Furthermore, since the screw thread is formed in the intermediate | middle screw part 12, the fixing force with respect to the bone 50 can further be raised.

  Moreover, by forming the surface of the intermediate screw portion 12 entirely with a porous body, in the long term, it grows so that bones enter the pores of the porous body. Thereby, it is easy to promote the fusion with the bone 50, and the long-term fixing performance to the bone can be improved.

  Further, in the bone screw 1 according to the present embodiment, the porous body is formed by melting and solidifying each time the metal powder is laminated. In this way, the porous body can be formed not only on the surface of the intermediate screw portion 12 but also on the inside. Therefore, since the bone 50 can penetrate deeply into the porous body and grow, the long-term fixing performance to the bone can be further increased.

  In the bone screw 1 according to the present embodiment, the distal-side screw portion 11 that is relatively easily loaded when the screw portion 10 is screwed to the bone 50 is formed of a dense body having a relatively high strength. If it carries out like this, when screwing the screw part 10 in the bone | frame 50 etc., the risk that this screw part 10 will be damaged can be reduced.

  Therefore, according to the present embodiment, it is possible to provide the bone screw 1 that has a low risk of breakage and can sufficiently secure a binding force to the bone.

  Further, in the bone screw 1 according to the present embodiment, the porosity of the porous portion 16 decreases in an inclined or stepwise manner from the surface toward the axis. In this case, since the structure of the porous portion 16 can be prevented from rapidly changing, the intermediate screw portion 12 can be configured to be less likely to cause stress concentration.

  In addition, the porosity of the porous portion 16 of the bone screw 1 according to the present embodiment is such that the portion on the surface side (portion on the bone side) is larger than the portion on the axial center side. Sufficient space for bone growth after screwing can be secured.

[Second Embodiment]
The bone screw 1 according to the second embodiment is different from the bone screw 1 according to the first embodiment in the configuration of the screw portion 10. Hereinafter, the differences from the first embodiment will be mainly described, and the description of the same configuration as the first embodiment will be made by attaching the same reference numerals in the drawings or by quoting the same reference numerals. Omitted.

-Bone screw configuration-
FIG. 7 is a diagram illustrating a configuration of the bone screw 1 according to the second embodiment, in which (A) is a front view of the bone screw 1 and (B) is a cross-sectional view of the bone screw 1.

  As in the case of the first embodiment, the bone screw 1 according to the second embodiment is integrally formed by a metal powder additive manufacturing method such as a selective laser melting method. The threaded portion 10 of the bone screw 1 according to the second embodiment is formed in a rod shape extending downward from the head 2 in the same manner as the threaded portion of the first embodiment, and a helical thread is formed on the outer peripheral surface thereof. Is formed. The outer diameter of the screw portion 10 is generally uniform throughout.

  The screw portion 10 of the second embodiment includes a tip side screw portion 11 and a screw main body portion 14. The front end side screw part 11 is comprised with the dense body like the front end side screw part in 1st Embodiment.

  The screw main body portion 14 is a portion corresponding to the proximal end side screw portion 13 and the intermediate screw portion 12 in the screw portion 10 of the first embodiment shown in FIG. The screw main body portion 14 is formed so as to extend from the bottom surface of the head 2 to the upper surface of the tip side screw portion 11, and a helical thread is formed on the outer peripheral surface thereof. The screw main body 14 includes a central portion 17 and an outer peripheral portion 18.

  The central portion 17 is a portion in the vicinity of the axial center of the screw main body portion 14. Specifically, the central portion 17 is a cylindrical portion that has an axial center concentric with the axial center of the screw main body portion 14 and is elongated in the axial direction. The center portion 17 is formed of a dense body having a density substantially the same as that of the head portion 2 and the distal end side screw portion 11.

  The outer peripheral portion 18 is a portion of the screw main body portion 14 excluding the central portion 17, that is, a portion on the outer peripheral side of the screw main body portion 14. The outer peripheral part 18 is comprised by the dense part 18a comprised by the dense body, and the porous part 18b comprised by the porous body. The dense portion 18 a is a portion of the outer peripheral portion 18 that extends from the top of the screw thread to the outer peripheral surface of the central portion 17. The porous portion 18b is a portion of the outer peripheral portion 18 excluding the dense portion 18a, that is, a portion of the outer peripheral portion 18 that extends from the bottom of the screw thread and the bottom of the screw groove to the outer peripheral surface of the central portion 17. . The dense portion 18a has a substantially uniform density and is approximately the same as the density of the head portion 2 and the tip side screw portion 11. The porosity of the porous portion 18 b decreases in a stepwise or stepwise manner from the top of the screw thread in the screw main body portion 14 toward the center portion 17.

[effect]
According to the bone screw 1 according to the present embodiment, as in the case of the bone screw 1 according to the first embodiment, a structure that does not easily cause damage can be realized, the risk of breakage can be reduced, and a fixing force to the bone 50 can be obtained. Therefore, it is possible to provide the bone screw 1 that can improve the fixing performance.

  Moreover, the bone screw 1 which concerns on this embodiment is comprised by the dense part 18a in the top part of the screw thread in the screw main-body part 14. FIG. If it carries out like this, when screwing the bone screw 1 with respect to the bone 50, or after screwing, the risk of damaging the part of the thread which is relatively easily loaded can be reduced.

  Further, in the bone screw 1 according to the present embodiment, the thread hem portion of the screw main body portion 14 and the bottom portion of the screw groove are constituted by the porous portion 18b. In this way, since a growth space can be secured in the bone portion in contact with the porous portion 18b of the bone 50 into which the screw main body portion 14 is screwed, the long-term coupling force between the screw portion and the bone can be increased. it can.

  That is, according to the bone screw 1 according to the present embodiment, it is possible to reduce the risk of thread breakage while securing a long-term coupling force between the screw portion 10 and the bone 50.

[Third Embodiment]
In the above-described embodiment, the bone screw 1 has been described as an example of the living body screw member. However, the present invention is not limited to this, and an artificial tooth (not shown) for prosthesis of the missing tooth is not limited thereto. It can also be set as the artificial tooth root 5 to be attached. Hereinafter, differences from the above embodiment will be mainly described, and description of the same configuration as the above embodiment will be omitted by giving the same reference numerals in the drawings or by quoting the same reference numerals. .

  FIG. 8 is a cross-sectional view showing a state in which the artificial tooth root 5 as the biological screw member according to the third embodiment is screwed to the jawbone 55. The artificial tooth root 5 is attached to a portion of the jawbone 55 where a tooth is missing and missing.

−Configuration of artificial tooth root−
Similarly to the case of the bone screw 1 according to the embodiment, the artificial tooth root 5 according to the present embodiment is also integrally formed by a metal powder additive manufacturing method such as a selective laser melting method. The artificial tooth root 5 according to the third embodiment includes a head 6 and a screw portion 10. The head 6 is an abutment to which artificial teeth are attached. The screw portion 10 is formed in a rod shape extending downward from the head portion 6, and a helical screw thread is formed on the outer peripheral surface thereof. The threaded portion 10 includes a distal end side threaded portion 11, an intermediate threaded portion 12, and a proximal end side threaded portion 13.

  The front end side screw part 11 is comprised with the dense body like the front end side screw part in 1st Embodiment.

  The intermediate screw portion 12 is an intermediate portion in the axial direction of the screw portion 10, that is, a portion between the distal end side screw portion 11 and the proximal end side screw portion 13 in the screw portion 10. The intermediate screw portion 12 includes a dense portion 15 and a porous portion 16 as in the case of the first embodiment. The dense portion 15 is a portion near the axial center of the intermediate screw portion 12, and the porous portion 16 is a portion on the surface side of the intermediate screw portion 12. The porosity of the porous portion 16 decreases gradually or stepwise from the surface of the intermediate screw portion 12 toward the axis.

  Further, the outer diameter of the intermediate screw portion 12 is the same as the outer diameter of the tip side screw portion 11. The pitch of the intermediate screw portion 12 is the same as the pitch of the tip side screw portion 11.

  In the third embodiment, the proximal end screw portion 13 is formed so as to have an outer diameter larger than that of the distal end side screw portion 11 and the intermediate screw portion 12. Further, the pitch of the base end side screw portion 13 is twice the pitch of the tip end side screw portion 11 and the intermediate screw portion 12.

[effect]
According to the artificial tooth root 5 according to the present embodiment, an artificial tooth root that can reduce the risk of breakage by realizing a structure in which damage is difficult to occur, and can improve the fixing performance for obtaining the fixing force to the jawbone 55 is provided. it can.

  In the artificial tooth root 5 according to the present embodiment, the outer diameter of the proximal-side screw portion 13 is larger than the outer diameters of the distal-side screw portion 11 and the intermediate screw portion 12. Thus, the proximal-side screw portion 13 advances while threading the screw hole formed by the distal-side screw portion 11 and the intermediate screw portion 12, and is screwed into the cortical bone constituting the surface portion of the jawbone 55. Therefore, since the proximal-side screw portion 13 can be reliably fixed to the jaw bone 55, the entire artificial tooth root 5 can be more firmly fixed to the jaw bone 55.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible as long as they are described in the claims. For example, the following modifications may be made.

[Modification]
(1) In the above-described embodiment, the porosity of the porous portions 16 and 18b decreases in an inclined or stepwise manner from the outer peripheral side to the inner side of the screw portion 10, but is not limited to this. For example, the porous portion The porosity of 16, 18b may be spatially uniform.

(2) In the above-described embodiment, the outer diameter of the tip side screw portion 11 and the outer diameter of the intermediate screw portion 12 or the screw main body portion 14 are the same, but not limited thereto, for example, as shown in FIG. In addition, the outer diameter of the tip side screw portion 11 may be larger than the outer diameter of the intermediate screw portion 12.

  When the artificial tooth root 5 is screwed into the jawbone 55, the intermediate screw portion 12 advances through the inside of the screw hole cut by the tip side screw portion 11. By setting it as the above structures, the intermediate | middle screw part 12 advances the inside of a screw hole, maintaining a clearance gap between the inner walls of the said screw hole. That is, the load applied to the intermediate screw portion 12 is reduced. Therefore, it is possible to reduce the risk that the thread of the intermediate screw portion 12 made of a porous body having a lower strength than the dense body is damaged.

(3) In Embodiment 3 described above, the outer diameter of the proximal-side screw portion 13 is larger than the outer diameters of the distal-side screw portion 11 and the intermediate screw portion 12, but this is not restrictive. The outer diameter of the side screw portion 13 may be the same as the outer diameters of the tip screw portion 11 and the intermediate screw portion 12.

  INDUSTRIAL APPLICABILITY The present invention can be widely applied as a biological screw member such as a bone screw for joining fractured portions in bone or an artificial tooth root screwed into a portion of a jaw bone where a tooth is missing.

1 Bone screw (screw member for living body)
5 Artificial dental root (screw member for living body)
10 Screw part 11 Tip side screw part 12 Intermediate screw part 50 Bone 55 Jaw bone (bone)

Claims (4)

A biomedical screw member having a screw portion screwed to a bone,
The tip portion of the screw portion is provided as a tip side screw portion formed of a dense body,
The intermediate portion in the axial direction of the screw portion is a porous body in which a portion extending from at least a part of the surface of the intermediate portion to at least a portion of the inside is a sparse structure than the dense body of the tip side screw portion. Configured as an intermediate screw part,
The tip side screw portion and the intermediate screw portion are solidified bodies integrated with each other,
The intermediate screw portion is
A center portion that is formed of a dense body and is a central portion in the radial direction of the intermediate screw portion;
A dense part, which is a dense part, and is a part extending from the top of the thread in the intermediate screw part to the central part;
A porous portion made of a porous body, which is a portion extending from the thread hem portion to the center portion of the intermediate screw portion, and a portion extending from the bottom of the screw groove of the intermediate screw portion to the center portion. When,
A biomedical screw member characterized by comprising: The biological screw member according to claim 1,
The portion of the intermediate screw portion that is formed of a porous body has a porosity that decreases from the surface of the intermediate screw portion toward the radial center of the cross section perpendicular to the axis of the intermediate screw portion. It is comprised as follows, The screw member for biological bodies characterized by the above-mentioned. The biomedical screw member according to claim 1 or 2,
The biomedical screw member, wherein the distal end side screw portion has an outer diameter larger than that of the intermediate screw portion. The biological screw member according to any one of claims 1 to 3 ,
The portion of the screw portion opposite to the tip screw portion is provided as a base screw portion made of a dense body,
The biological screw member, wherein the proximal-side screw portion has an outer diameter larger than that of the distal-end side screw portion and the intermediate screw portion.

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