Retention structure of fine particles

Abstract

This invention provides a novel bone graft retention structure that can securely fix the bone graft material during the healing period, and during or after the healing period, the bone graft fixing component is safely absorbed into the body through a bioabsorption reaction without the need to remove it from the body through additional surgery, and is then safely excreted from the body. [Solution] A holding structure for granular material, wherein the granular material is a bone graft material in the shape of fine particles that fill the gap between the root of an implant embedded in the living body and the bone of the living person opposite the root, and a mesh-like material having a mesh structure holds and fixes the bone graft material in all directions.

Description

Technical Field

[0001] The present invention relates to a mesh structure of a thin-diameter object and a method of using the same, which are devised for the purpose of safely and surely holding and fixing a bone filler filled in a gap existing between a main root part among implants implanted in a body bone part in dentistry and orthopedics, particularly, and living bone adjacent to the main root part in a diseased part during its healing period. Moreover, after new bone has grown and the healing period has elapsed, the mesh structure is made of a material that is absorbed and disappears in the living body, and in order to surely hold and fix a fine-grained bone filler filled in a healing site in advance, according to the particle size of the fine-grained bone filler to be filled, the present invention also relates to a clinical method of a mesh structure capable of more accurately holding and fixing the bone filler by freely adjusting the void density of the mesh structure.

Background Art

[0002] When implanting a dental implant and an orthopedic implant (for example, a hip joint implant, a knee joint implant or a shoulder joint implant) at a site in the body, if there is sufficient bone volume at the implantation site, there is no problem and postoperative healing can be expected. However, as is clear in many cases, there may be insufficient bone quality (bone density) and bone volume (bone thickness and height) for implanting an implant. In such cases, preparation before an implant implantation surgery for forming new bone so as to surround the main root part of the implant is essential.

[0003] For example, taking the case of a dental implant, if bone tissue is not created, the volume and shape of soft tissues such as the gingiva cannot be maintained, so aesthetic problems may occur early, the cleaning property may deteriorate, an infection may occur, and as a result, peri-implant inflammation may be caused.

[0004] Therefore, artificial bone formation (GBR: Guided Bone Regeneration) is classified according to the following functions. Firstly, this is an osteogenic surgical method in which bone fragments harvested from the patient's own bone (referring to the patient's own bone) are appropriately cut and processed and placed in the relevant area. While this autologous bone also possesses the bone induction and bone conduction functions described later, it requires a double surgical procedure on the patient and is not a common surgical method.

[0005] Secondly, there is a bone-inducing surgical method that uses bone from another person (decalcified freeze-dried allogeneic bone) and induces bone-forming cells (mesenchymal stem cells, etc.) to form new bone. However, there is strong resistance in Japan to having bone derived from another person placed in the body, and it is often difficult to obtain patient consent, so the number of cases is small.

[0006] Thirdly, regarding osteoconduction-type surgical methods, synthetic calcium phosphate-based materials are commonly used in Japan, and in particular, hydroxyapatite, the main inorganic component of bone, is generally used clinically. Alternatively, calcium phosphate-based artificial bone materials are also known to enhance the bone-forming ability of osteoblasts (see Non-Patent Documents 1, 2, and 3).

[0007] As mentioned above, the artificial bone graft material typically has a shape ranging from millimeter-order size (see Non-Patent Document 3) to coarse grains on the micron order, which is the typical particle size of hydroxyapatite (see Non-Patent Documents 4, 5, and 6), and fine grains on the nano order (see Non-Patent Document 7), depending on the firing temperature and time, resulting in a wide range of final particle sizes. Therefore, as mentioned above, methods for securely fixing bone graft material containing appropriately selected hydroxyapatite to the implant site, based on bone density, bone width, thickness, and other bone volume, and for promoting bone regeneration have been developed and clinically applied in a wide variety of ways.

[0008] To explain this method with reference to Figure 1 (quoted from Non-Patent Literature 3, Figure 8.1), first, an implanted implant like the one shown in (a) on the far left (an example of a dental implant) is ideal because it satisfies both the bone quality and bone volume in the affected area of ​​the patient's body, which serves as the receiving vessel, and therefore guided bone regeneration (GBR) is unnecessary. However, in the remaining three examples shown in Figures 1(b) to (d), the bone quality and bone volume are not sufficient in the lateral, longitudinal, and both directions, respectively. Therefore, it is necessary to insert bone graft material into the affected area and cover it with a mesh or net-like material to ensure that the bone graft material is securely secured and retained in that area. These structures are sometimes called scaffold structures in the technical terminology of cell tissue engineering.

[0009] Since these meshes naturally need to remain in the healing site during the healing period (approximately 6 to 10 months), good biocompatibility is required, and titanium or nickel-free medical-grade stainless steel is usually chosen. However, this leads to the following two problems 1 and 2.

[0010] Problem 1 is that although the GBR method described above is widely used clinically, due to the relationship between the bone graft material and gravity, the bone graft material tends to fall and move vertically downward over time, and in many cases, the initial filling expectations cannot be maintained. Problem 2 is that the scaffolding used to hold the bone graft material becomes unnecessary after new bone grafting is completed, requiring additional surgery to remove it. This places an unnecessary mental and financial burden on the patient.

[0011] Furthermore, while there are more extensive surgical procedures than the standard GBR method described above, such as the "Osteoperiosteal flap technique," "Distraction osteogenesis," "Bone expansion technique," "Sandwich osteotomy," and "Alveolar Ridge Splitting technique," which involve cutting and separating bone (especially alveolar bone), the aforementioned bone grafting methods, which are commonly performed, are still clinically applied to support reliable bone regeneration in the affected area.

[0012] Patent Document 1 raises questions about the biocompatibility and bone formation function of the materials used, and because it is cylindrical, the direction of movement is predetermined and the degree of freedom of movement is limited. Furthermore, Patent Document 2 discloses prototypes of intramedullary nails, screws, or bone plates made of high-purity magnesium, but these are solid objects and can only be applied to orthopedic clinical practice such as fracture treatment. In addition, although biosolubility is indicated, the dissolution rate and methods for controlling it are not disclosed.

[0013] Furthermore, the term "implant" used in Patent Document 3 deviates from the conventional definition of implants in dentistry and medicine. Essentially, it discloses a fracture treatment device that covers the autologous bone fragment of a fracture site and surgically repairs and fixes the treatment site, with a double-layered structure in the axial direction consisting of a cylindrical structure made of biocompatible metal wire braiding and a cylindrical structure made of biocompatible resin wire braiding. However, the spatial density of the mesh structure corresponding to the particle size of the artificial bone graft material cannot be appropriately adjusted during surgery.

[0014] According to the prior art described above, in cases where the bone quality or volume at the site of implantation is so insufficient to adequately support the implanted implant (especially the main root portion), a bone graft material is inserted using a bone augmentation method. During the healing period, in order to improve bone density and bone quality at the healing site along with the development and growth of osteoblasts, a method is disclosed in which particles of artificial bone graft material, such as hydroxyapatite, are covered with an appropriate retaining device (e.g., a metal mesh or net) at the healing site to ensure that the artificial bone graft material is securely held in place. However, the conventional methods that have been used in clinical practice, as described above, have the following two problems that require improvement.

[0015] The first problem is that, as is unavoidable in a gravitational environment, bone graft material is affected by gravity when it fills a space. In other words, the graft material tends to fall and move vertically downwards over time, and in many cases, it is impossible to maintain the initial state of the filling. Therefore, even if a mesh or net with a "sieve opening" that matches the particle size of the artificial bone graft material is selected, it is impossible to reliably hold all of the artificial bone graft material that exhibits a statistically widespread particle size distribution.

[0016] The second problem is that the retaining devices, which consist of mesh or nets used to hold the artificial bone graft material, become unnecessary after new bone formation is observed and the contact surface between the bone structure and the implanted implant has undergone osseointegration, requiring an additional surgical procedure to remove them. This would place an unnecessary mental and financial burden on patients undergoing implant treatment. [Prior art documents] [Patent Documents]

[0017] [Patent Document 1] Special Publication No. 2008-501462 [Patent Document 2] Patent No. 7301490 [Patent Document 3] Patent No. 7478427 [Non-patent literature]

[0018] [Non-Patent Document 1] Yoshiki Oshida and Tadashi Miyazaki“Biomaterials and Engineering For Implantology” De Gruyter Pub.,2012.

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0019] The present invention has been made in view of the above problems, and aims to provide a new bone filler holding structure that can surely fix the bone filler at the healing site during the healing period, and can be safely absorbed and disappear in the body by a bioabsorption reaction without removing the bone filler outside the body during or after the healing period.

Means for Solving the Problems

[0020] The first aspect of the present invention is a holding structure for particulate matter, wherein the particulate matter is a particulate bone filler that fills a gap existing between the root of an implant implanted in a living body and the bone of the living body opposite to the root, and a net-like object having a mesh structure holds and fixes the bone filler in all directions. It is a holding structure for particulate matter.

[0021] The second aspect of the present invention is a holding structure for particulate matter, characterized in that the net-like object in the first aspect is composed of wires of a single diameter and has a single-layer mesh structure made of a single material.

[0022] The third aspect of the present invention is a holding structure for particulate matter, characterized in that the net-like object in the first aspect is a single-layer net-like object composed of wires of a plurality of diameters and having a single-layer mesh structure made of a single material.

[0023] The fourth aspect of the present invention is a holding structure for particulate matter, characterized in that the net-like object in the first aspect is composed of wires of a single diameter and has a single-layer mesh structure made of a plurality of materials.

[0024] The fifth aspect of the present invention is a holding structure for particulate matter, characterized in that the net-like object in the first aspect is composed of wires of a plurality of diameters and has a single-layer mesh structure made of a plurality of materials.

[0025] A sixth aspect of the present invention is a fine-grained substance holding structure characterized in that the single material in the second and third aspects is a bioabsorbable magnesium material.

[0026] A seventh aspect of the present invention is a fine-grained substance holding structure characterized in that the plurality of materials in the fourth and fifth aspects include a bioabsorbable magnesium material, and the remainder is composed of a bioabsorbable polymer.

[0027] The eighth aspect of the present invention is a fine-grained material holding structure characterized in that the mesh material in the first aspect has a multilayered hybrid mesh structure having different mesh sizes.

[0028] The ninth aspect of the present invention is a fine-grained material holding structure characterized in that each layer forming the multilayer hybrid network structure in the eighth aspect consists of lines of one or more diameters.

[0029] A tenth aspect of the present invention is a fine-grained material holding structure characterized in that each layer forming the multilayer hybrid network structure in the eighth aspect is a layer of a single material.

[0030] An eleventh aspect of the present invention is a fine-grained material holding structure characterized in that each layer forming the multilayer hybrid network structure in the eighth aspect is made of a different material from the adjacent layer.

[0031] A twelfth aspect of the present invention is a fine-grained substance holding structure characterized in that the single material in the tenth aspect is a bioabsorbable magnesium material.

[0032] A thirteenth aspect of the present invention is a fine-grained substance holding structure characterized in that the different material in the eleventh aspect is a bioabsorbable magnesium material and a bioabsorbable polymer.

[0033] A fourteenth aspect of the present invention is a fine-grained material holding structure characterized in that the mesh in the first aspect is composed of plate materials of the same cross-sectional shape and has a single-layer mesh structure made of a single material. [Effects of the Invention]

[0034] According to the present invention, a novel bone graft retention structure is provided that can reliably fix the bone graft material during the healing period, and during or after the healing period, the bone graft fixing member can be safely absorbed and eliminated from the body through a bioabsorption reaction without having to remove it from the body by additional surgery or other means. [Brief explanation of the drawing]

[0035] [Figure 1] These are four examples (a) to (d) showing the relationship between the bone shape of the implanted implant principal root portion 10 and the tooth root portion 20. [Figure 2] This is an external view showing one embodiment of a mesh structure made of a mesh material according to the present invention, where (a) shows a mesh with a square shape and a mesh size of 3-4 mm, (b) shows a state in which the mesh is contracted to a square shape of 2-3 mm, and (c) shows a state in which the mesh is stretched to a square shape of 4-5 mm. [Figure 3] This is an external view showing another embodiment of the mesh structure of the mesh material according to the present invention, a hybrid mesh structure 1h constructed in a double cylindrical shape using the mesh material 1b of Figure 2(b) and the mesh material 1c of Figure 2(c), with the mesh being square in shape and measuring 2 to 5 mm. [Figure 4] Figure 2(b) shows the external view of mesh material 1L in a state where the mesh structure has been drastically contracted. [Modes for carrying out the invention]

[0036] To solve the first problem mentioned above, this method targets a mesh structure made of biocompatible and absorbable metal wires with one or more diameters, or biocompatible and absorbable polymer wires with one or more diameters. By freely controlling the void size (or "sieve opening") of the mesh structure through stretching or crushing operations, it becomes possible to control and prevent the movement and detachment of the inserted bone graft material from its initial position, which is a problem in conventional methods, in accordance with the average particle size of the selected bone graft material. The mesh structure (net-like material) used in the present invention is manufactured by a conventional method, such as the one described in Patent Document 3. Furthermore, in this invention, "fine wire of a single diameter" refers to a fine wire whose diameter falls within the range of general tolerances defined in JIS B 0405-1991 (ISO2768-1;1989).

[0037] To solve the second problem mentioned above, the selection of materials used is crucial. Both biocompatible metal meshes and biocompatible polymer meshes are bioabsorbable, and during the healing period, once new bone formation is observed and the bone structure and the surface of the implanted implant fuse, they are completely absorbed and disappear within the body. This eliminates the need for additional surgical removal of bone graft retention devices such as meshes or nets used in conventional methods.

[0038] Furthermore, to solve the two problems mentioned above, it is important to use a three-dimensional mesh structure instead of the conventional two-dimensional sheet-like mesh structure, and to be able to freely and easily expand or contract the spatial spacing of the mesh structure. As a result, it becomes possible to stably maintain bone graft material with a wide particle size distribution throughout the healing period.

[0039] Examples of embodiments according to the present invention are shown in Figures 2 to 4. Figure 2 shows a mesh structure made of a single material and a single diameter wire, where (a) is an external view of mesh structure 1a having a standard mesh size 2, (b) is an external view of mesh structure 1b having a mesh structure when the mesh size 2 of Figure 2(a) is contracted to make the mesh smaller, and (c) is an external view of mesh structure 1c having a mesh structure when the mesh size 2 is stretched, the opposite of (b). As can be seen in Figure 2, in the embodiment of the present invention, the size of the mesh 2 can be adjusted by contracting or stretching the mesh, and it is possible to provide a mesh with an adapted mesh structure that can respond immediately to fluctuations in the average particle size of the bone graft material used. Although the embodiment shown in Figure 2 illustrates an example using a single material and a single diameter wire, the mesh 2 can be easily adjusted in the same way when using a single material with wires of different diameters, or when using multiple materials with wires of a single diameter or multiple diameters. In this invention, the mesh structure is defined by the rectangular shape used in the description, but it is not limited to this; rhombuses, hexagons, and other shapes can also be used.

[0040] The embodiment shown in Figure 3 is an external view of a mesh material 1h having a hybrid mesh structure due to its configuration, and shows a double-tube type mesh material 1h, which is an example of a multi-tube type in which a mesh material 1b is arranged on the inside and a mesh material 1c is arranged on the outside. In this way, by using two or more mesh-like materials with different mesh sizes layered together, it is possible to accommodate the average particle size of bone graft material over a wide area. Furthermore, by considering the attributes (diameter and material) of the wires that make up the mesh, it is possible to accommodate an even wider range of average particle sizes.

[0041] Figure 4 shows an external view of the state after further contraction of the shrinkage operation in Figure 2(b), until the mesh 2 is almost completely collapsed. Even in this state, it appears that the bone graft material can still be held in place by the gaps formed by the collapsed mesh, thus further reducing the range of average particle size that can be accommodated.

[0042] As described above, by appropriately adjusting the mesh (spatial spacing) 2 of the mesh structure in the mesh material shown in Figures 2 to 4, the particle size range of the bone graft material described in Non-Patent Documents 4 to 7 (from nano-order to millimeter-order) can be freely and appropriately adjusted in three dimensions, leading to a safe and reliable reduction in the healing period. As a result, treatment according to the practitioner's treatment plan can be achieved.

[0043] By the way, we have explained in detail the structure for safely and securely holding fine-grained bone graft material in the healing site. This structure is achieved by using a three-dimensional mesh structure that allows for free control of the spatial spacing, which is appropriately matched to the particle size of the bone graft material. Furthermore, in clinical applications in orthopedic surgery, such as total knee replacement surgery or total lumbar replacement surgery, the healing area to which bone graft material is applied is generally wider than in dental implants. In these cases, it should be noted that the use of conventional two-dimensional mesh in combination with the aforementioned mesh structure as an intermediate layer or outermost layer is also a viable option.

[0044] Here, we will refer to the evaluation method of the present invention. First, to give a general overview of the dental implant treatment process, the treatment is performed in the following order from (1) to (7). (1) Determination of implant placement position, (2) Extraction of the tooth in the area (3) Bone grafting treatment, (4) Implant root insertion + suturing (4-1), or placement of the entire implant body (4-2) (5) Healing period, (6) Abutment is attached in the secondary surgery (6-1). However, if the route described in (4-2) is followed, the process in (6-1) is omitted (6-2). (7) If the load transitions to occlusion or mastication (7-1), or if the process follows (4-2) and (6-2), it is considered a transition to early load (7-2). Furthermore, in treatments that follow routes (4-1) and (6-1), the healing period between them is estimated to be approximately 6 to 8 months.

[0045] If the effectiveness of the present invention can be confirmed during this healing stage, the patient can transition to loading (generally, everyday chewing function) without waiting for a long healing period, drastically reducing the burden on the patient. In other words, in many cases, a specialist can determine that an early loading stage is possible based on good bone grafting / bone formation during the healing stage and the resulting implant stability index (ISQ) measurement. This ISQ value represents the stability of the implant body within the bone structure, expressed as a number from 1 to 99 using, for example, a resonant frequency analyzer. A higher ISQ value indicates greater stability. Since the resonance frequency analysis device is a non-contact measurement device, stable measurements can be performed without causing any unnecessary impact to the implant body (see Non-Patent Document 8).

[0046] Furthermore, the three-dimensional network structure made of bioabsorbable and disappearing magnesium can, of course, be investigated (or its degree of disappearance due to absorption over time) using X-ray imaging equipment routinely used in dental clinics. [Explanation of symbols]

[0047] 1a Mesh-like material (square-shaped mesh structure with 3-4 mm mesh) 1b. Mesh-like material (a rectangular mesh structure with 2-3 mm meshes) 1c. Mesh-like material (square-shaped with a mesh structure of 4-5 mm) 1h Mesh-like material (square-shaped hybrid mesh structure with 2-5 mm mesh) 1L Net-like material (extremely contracted state) 2 mesh 10 Taproot 20 Root portion

Claims

1. A structure for holding fine particles, The aforementioned fine-grained material is a bone graft material in the form of fine particles that fill the gap between the root of an implant embedded in the body and the bone of the living person opposite the root. A fine-grained material holding structure characterized in that a mesh-like material having a mesh structure holds and fixes the bone graft material in all directions.

2. The fine-grained material holding structure according to claim 1, characterized in that the mesh-like material is composed of lines of a single diameter and has a single-layer mesh structure made of a single material.

3. The fine-grained substance holding structure according to claim 1, characterized in that the mesh is a single-layer mesh having a single-layer mesh structure composed of multiple lines of different diameters and made of a single material.

4. The fine-grained material holding structure according to claim 1, characterized in that the mesh-like material is composed of lines of a single diameter and has a single-layer mesh structure made of multiple materials.

5. The fine-grained substance holding structure according to claim 1, characterized in that the mesh-like material is composed of lines of multiple diameters and has a single-layer mesh structure made of multiple materials.

6. The fine-grained substance holding structure according to claim 2 or 3, characterized in that the single material is a bioabsorbable magnesium material.

7. The fine-grained substance holding structure according to claim 4 or 5, characterized in that the plurality of materials include a bioabsorbable magnesium material and the remainder is composed of a bioabsorbable polymer.

8. The fine-grained material holding structure according to claim 1, characterized in that the mesh-like material has a multilayered hybrid mesh structure having mesh sizes of different sizes.

9. The fine-grained material holding structure according to claim 8, characterized in that each layer forming the multilayer hybrid network structure consists of lines of one or more diameters.

10. The fine-grained substance holding structure according to claim 8, characterized in that each layer forming the multilayer hybrid network structure is a layer of a single material.

11. The fine-grained material holding structure according to claim 8, characterized in that each layer forming the multilayer hybrid network structure is made of a different material from the adjacent layer.

12. The fine-grained substance holding structure according to claim 10, characterized in that the single material is a bioabsorbable magnesium material.

13. The fine-grained substance holding structure according to claim 11, characterized in that the different materials are a bioabsorbable magnesium material and a bioabsorbable polymer.

14. The fine-grained substance holding structure according to claim 1, characterized in that the mesh-like material is composed of plate materials having the same cross-sectional shape and has a single-layer mesh structure made of a single material.

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