JPH07112000A - Intraosseous implant - Google Patents

Abstract

PURPOSE:To provide a screw-type implant by using which good implantation can be performed by means of direct implantation even when a bone is hard. CONSTITUTION:In a cylinder-type intraosseous implant consisting of a collar part 1 and a main body part 2 provided with a screw below it, the intraosseous implant has the height h of a thread of 0.2-0.4mm, the pitch P of the thread of 0.8-1.7mm and the angle theta formed by a straight line connecting the top of the thread or the lowermost point of the top side with the lowermost point of the bottom side of the thread and the bottom side of the thread of at least 50 and smaller than 90 deg..

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in endosseous implants used for dentistry and maxillofacial prostheses.

[0002]

2. Description of the Related Art At present, there are two types of intraosseous implants (hereinafter abbreviated as implants) in the field of dentistry: blade type and cylinder type. The blade-type implant has a plate-like shape in appearance and is used for repairing a free end defect in all parts of the jawbone, particularly from a premolar to a molar. A wide blade type is often used in this part because the lower alveolar canal is below the bone surface and a too long implant cannot be implanted. The perforation hole (prepared hole for implantation) is formed by moving in the mesio-distal direction while perforating with a drill having the same diameter as the width of the blade, and thus the shape is likely to collapse.

The cylinder type implant has a cylindrical shape and can be implanted in all parts of the jawbone. The shape of the fovea is circular, which allows more accurate holes to be formed for the implant diameter than the blade type. The diameter of the cylinder type (the diameter based on the screw thread) is about 3 to 5 mm due to the limitation of the width of the jaw bone. There are two types of operation methods, the blade type is a push-in method, and the cylinder type is a push-in method and a screw-in method.

Generally, the state of the interface between the implant and the bone several months after the implant is implanted is one in which fibrous tissue is present between the implant and the bone,
There is a type in which the bone and the implant material are directly contacted or bonded. At present, the latter is the mainstream because it can be used stably for a longer period of time. The upper part of the implant is provided with a part with a smooth surface, generally called “collar”, and the main part, which is the part below it, keeps the implant in the bone and resists various stresses generated in the oral cavity. It has the function of protecting the implant from shaking and falling. Smoothing the surface of the brim has an effect of preventing invasion of various bacteria from the oral cavity, but the brim does not contribute to the intraosseous maintenance of the implant unlike the main body.

Common methods of implanting an implant in bone are the "single-step method" and the "double-step method". In the one-time method, since the upper end of the implant penetrates the gingiva and is exposed in the oral cavity at the time of implantation, it is not necessary to incise the gingiva when attaching the superstructure to the upper end of the implant. In the double implant method, the implant is completely embedded in the bone at the time of implantation, and after several months, the gingiva is incised and a superstructure is attached to the upper end of the implant. Therefore, the length of the brim of the one-time implant is 5 to 10 m.
While it is as long as m, it is about 0.5 to 2 mm in the double method, and there is a difference in the length of the brim.

[0006] The main body portion is generally in a form of being maintained in the bone by mechanical anchoring such as a screw or surface unevenness. Furthermore, recently, attempts have been made to coat the surface of the main body with a bioactive material to improve the sustainability by chemical bonding with bone. In a cylinder type intraosseous implant consisting of a collar part and a body part below it, in a screw type implant with a screw on the body part, the diameter of the collar part is larger than the diameter of the screw thread, and this collar part is It plays the role of a screw head.

In implanting a screw-type implant, first, a straight hole having a diameter equal to the root diameter of the screw is formed, then the hole corresponding to the collar is enlarged in a mortar shape, and then tapped on the main body. The corresponding holes are screw holes. Finally, the implant is implanted along the screw hole (the above operation is hereinafter referred to as tap implantation). In conventional screw-type implants, this tap implantation technique has been mainly adopted.

On the other hand, a screw type implant is inserted into a straight hole without first forming a screw hole, and the implant is implanted while directly shaving bone with the implant (hereinafter referred to as direct implantation). It may be operative, but only if the bones are soft.

[0009]

[Problems to be Solved by the Invention] Immediately after implanting an implant, if the bone and the implant surface are in contact with each other without a gap and the motion of the implant itself is small, the contact between the bone and the implant occurs quickly and surely. , The chance of implant loss is reduced. Direct implants are more prone to this condition than tap implants, so implants are less likely to fall off. Therefore, it is more advantageous to use a lot of direct implants instead of tap implants which have been mainly used in the past.

However, in the case of direct implantation, there is a problem that the implantation may not be possible or the implantation may not be successful when the bone is hard. An object of the present invention is to provide a screw-type implant capable of performing a good implant by using a direct implanting technique even when the bone is hard.

[0011]

Therefore, in the first aspect of the present invention, in a cylinder type intraosseous implant consisting of a collar portion and a main body portion provided with a screw under the collar portion, the height of the thread of the screw is 0.2-0.4 mm, thread pitch
0.8 to 1.7 mm, characterized in that the straight line connecting the lowest point of the top or the top of the screw thread and the lowest point of the bottom of the screw thread forms an angle with the base of the screw thread of 50 degrees or more and less than 90 degrees. An endosseous implant (claim 1) "is provided.

A second aspect of the present invention is a "cylinder type intraosseous implant comprising a collar portion and a main body portion provided with a screw below the collar portion, in which the height of the thread of the screw is
0.2 to 0.4 mm, screw thread pitch 0.8 to 1.7 m
m, an intraosseous implant characterized in that an angle formed by the straight line connecting the lowest point of the apex or the top of the screw thread and the lowest point of the bottom of the screw thread is 60 degrees or more and 75 degrees or less with the bottom of the screw thread (Claim 2) "is provided.

Further, the present invention thirdly provides the "intraosseous implant (claim 3) according to claim 1 or 2, wherein the maximum surface roughness of the main body is 20 to 50 µm". .

[0014]

As a result of earnest research, the present inventor has increased the initial fixing force when directly implanting an implant with a screw according to the present invention into a bone, and promptly and reliably after implant implantation. The important parameters for achieving bone contact are the thread height h, the thread pitch P, the apex of the thread or the lowest point 5 of the top side 4 and the lowest point 6 of the bottom side 3 of the thread. Finding that the straight line is the angle θ formed by the base 3 of the screw thread,
The present invention has been completed (see FIG. 2). In addition, "bottom point"
The lower direction 7 is the direction in which the screw thread advances.

If the height h of the screw thread is too high, the implant cannot be implanted in a bone portion having a narrow bone width, and the resistance at the time of implantation is too large to successfully implant. On the other hand, when the height h of the screw thread is too low, the fixing force by the screw is too weak, the initial fixation of the implant becomes insufficient, and the implant holding force at the time of occlusion becomes small. And, at the end of implantation of the implant, idle rotation may occur. Therefore, in the present invention, the height h of the screw thread is set to 0.2 to 0.4 mm.

If the thread pitch P is too large, the distance (lead) that the thread tries to advance when the implant is rotated once becomes too large. Therefore, the resistance from the bone at the time of implanting the implant is too large, and the vibration when screwing in is too large, so that the implant cannot be successfully implanted. on the other hand,
If the pitch P of the screw thread is too small, it takes a long time to implant the implant because the lead is small. Also, threaded bones are easily destroyed. Therefore, in the present invention, the thread pitch P is set to 0.8 to 1.7 mm.

The angle θ formed by the straight line connecting the lowest point 5 of the apex or the top side 4 of the screw thread and the lowest point 6 of the bottom side 3 of the screw thread with the bottom side 3 of the screw thread is 50 from the implant embedding experiment.
It was found that an appropriate range is not less than 90 degrees and not more than 90 degrees. And particularly preferably, it is 60 degrees or more and 75 degrees or less. The cross-sectional shape of the screw thread is not particularly limited, but basically, a shape having a small cross-sectional area requires less bone to be shaved at the time of implant implantation. In terms of sharpness, the triangular shape is superior to the trapezoidal, rectangular, and saw blade shapes. Further, since both tensile stress and compressive stress are applied to the implant by the occlusal stress during the function of the implant, it is preferable that the cross-sectional shape of the screw thread is a balanced symmetrical shape. This is because loads on the implant due to both tensile and compressive stresses can be reduced.

Each side of the screw thread is not limited to a straight line, but may be a curved line. Further, the top portion of the screw thread is not limited to a point and may be a side. It should be noted that the top portion of the screw thread is often a straight side or a curve having a curvature for the convenience of actual machining. The surface roughness of the main body portion 2 of the implant is also important for increasing the initial fixing force at the time of implanting the implant and achieving quick and reliable bone contact after the implant. That is, if the surface roughness is too small, the initial fixing force is reduced, and thus mechanical uncalaging of the bone and the implant is not sufficiently performed. On the other hand, if the surface roughness is too large, it becomes easy for bacteria to become a hotbed when the main body 2 is exposed, so that bone resorption is likely to occur from infection. Therefore, the maximum surface roughness of the main body 2 of the implant is preferably 20 to 50 μm.

The material of the collar portion 1 and the main body portion 2 is, for example,
Ti, a Ti alloy, a metal such as a Co—Cr system, a bioinert ceramic such as aluminum oxide or zirconium oxide, a bioactive material (ceramics, glass, crystallized glass, etc.) and the like are preferable. For crystallized glass, for example, A
There are BC and AW. Further, it is preferable to provide a bioactive layer made of a bioactive material on the surface of the main body 2 made of metal or bioinert ceramics. Due to the osteoconductive effect of the bioactive material, the initial fixation with the bone can be made faster than when it is not provided. That is, the bone is entangled with the material components of the main body 2 and the bond with the bone is accelerated.

As a pretreatment for providing the bioactive layer, the main body 2 is cleaned and roughened by, for example, a blasting treatment, and after the blasting treatment, a chemical treatment such as acid etching or anodic oxidation is further performed to further improve the surface. It is preferable to roughen the surface. This is because the contact area with the bioactive layer increases and the adhesion strength increases. The bioactive layer is preferably provided on the surface of the main body 2 as thin as possible, and for example, it is preferable that the bioactive layer is scattered on the surface of the main body 2. That is, it is preferable that the exposed portion of the main body 2 be larger than the portion where the bioactive layer is provided. With this configuration, the exposed portion of the main body 2 is easily entangled with the bone and is easily coupled.

As the bioactive material forming the bioactive layer, for example, hydroxyapatite, tricalcium phosphate,
Bioactive glass or glass-ceramics (see, eg, J. Biomed. Mater. Res. Symp.
No. 2 (Part1) pp. 111-141 (197)
1), JP-A-50-21015, JP-A-51-106
114, JP-A-53-145394, JP-A-54-
17, JP-A-54-135496, JP-A-57-3
No. 739, JP-A-58-118746 and the like), and apatite-based sintered bodies described in JP-A-62-052163 are preferable.

As a method for providing the bioactive layer, for example, vapor phase methods such as vapor deposition, CVD, sputtering and ion plating, solid phase methods such as thermal spraying and sintering, and liquid phase methods such as anodic oxidation are preferable. Further, in order to improve the adhesive strength between the surface of the main body 2 and the bioactive layer, an intermediate layer is provided between the surface of the main body 2 and the bioactive layer, or between the surface of the main body 2 and the bioactive layer. It is also possible to provide a layer in which the composition of the bioactive material and the intermediate layer material is continuously changed.

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[0024]

[Examples] In a cylinder type implant for two-step method with a length of 10 mm and a collar 1 of 2 mm in which a screw having a root diameter of 2.7 mm is provided in the main body 2, the height h of the thread and the thread Each parameter was changed with the pitch P, the apex of the thread or the angle θ formed by the straight line connecting the lowest point 5 of the top side 4 and the lowest point 6 of the bottom side 3 of the thread with the bottom side 3 of the thread. Multiple implants were made. These implants are shown in Table 1.

Implant each implant directly into the jawbone of a pig,
The state at that time was evaluated. Table 2 shows the evaluation results. In addition, the diameter of the root of the screw (2.7 m
After forming a straight hole with a diameter equal to m), the hole corresponding to the brim was enlarged in a mortar shape with a counter sink. Evaluation is whether the screw easily enters the bone at the start of implantation (easiness of biting), the implant enters straight without shaking during screwing (straightness), or whether the bone cuts smoothly without any resistance during screwing ( Resistance), when the collar of the implant comes into contact with the mortar-shaped hole at the countersink, the screwing resistance suddenly increases and the surgeon recognizes that the implant has been implanted to an appropriate depth (end). In addition to the four items of (feeling), a comprehensive evaluation was performed by comprehensively evaluating these four items.

By the way, the biggest difficulty of the screw type implant is that it is difficult to obtain a feeling of termination, so that the implant is rotated too much (screwed too much) to destroy the bone (implant idles), or conversely, the bone is destroyed. The fear is that the screwing will be insufficient and the initial fixation of the implant will be poor, and the implant will likely fall out. Therefore, in the comprehensive evaluation, among the evaluation items, the evaluation of the feeling of ending is weighted.

As a result of comprehensive evaluation, usable implants are numbered 4, 5, 7, 8, 13, 14, 16,
It was 17. The implants that can be used are: thread height h: 0.2-0.4 mm, thread pitch P: 0.8-1.7 mm, screw thread apex or lowest point 5 of top side 4 and thread base 3 The straight line connecting the lowest point 6 of the above with the base 3 of the screw thread satisfies the following conditions: angle θ: 50 degrees or more and less than 90 degrees.

Among the implants that can be used, plasma was applied to each of the main bodies of the implants of Nos. 4, 7 and 14 which had particularly good evaluation results and the implants of Nos. 9, 18 and 26 which had poor evaluation results. The same evaluation was performed for each implant in which Ti was coated by thermal spraying so that the maximum surface roughness of the main body was 20 to 50 μm. As a result, the implants of Nos. 4, 7, and 14 showed even better results than the above results, but the implants of Nos. 9, 18, and 26 showed no particular change in the evaluation results.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, according to the present invention, even when the bone is hard, good implantation can be performed by using the direct implantation technique. As a result, the implant is unlikely to fall off, and it is possible to use the implant in the body for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic side view of an implant according to an embodiment.

FIG. 2 is an explanatory diagram (schematic diagram) showing each parameter of the screw provided on the main body of the implant.

[Explanation of symbols]

1 ... Collar part of intraosseous implant 2 ... Body part of intraosseous implant 3 ... Bottom of screw thread 4 ... Top of screw thread 5 ... Lowest point of top of screw thread 6 ... The lowest point of the bottom of the screw thread 7 ... Downward direction (direction of travel of the screw thread) h ... Height of the screw thread P ... Pitch of the screw thread .theta. The angle between the straight line connecting the lowest point of the apex or the top and the lowest point of the bottom of the screw thread and the bottom of the screw thread is less than

Claims (3)

[Claims] 1. A cylinder type intraosseous implant consisting of a collar portion and a threaded body portion below the collar portion, wherein the thread height of the screw is 0.2 to 0.4 mm and the thread pitch is 0.8 to 1.7. mm, an intraosseous implant characterized in that an angle formed by the straight line connecting the lowest point of the apex or top of the screw thread and the lowest point of the bottom of the screw thread is 50 degrees or more and less than 90 degrees with the bottom of the screw thread . 2. A cylinder type intraosseous implant consisting of a collar portion and a threaded body portion below the collar portion, wherein the thread height of the screw is 0.2 to 0.4 mm and the thread pitch is 0.8 to 1.7. mm, an intraosseous implant characterized in that an angle formed by the straight line connecting the lowest point of the apex or the top side of the screw thread and the lowest point of the bottom side of the screw thread is 60 degrees or more and 75 degrees or less with the bottom side of the screw thread. . 3. The maximum surface roughness of the main body is 20 to 50.
3. The intraosseous implant according to claim 1 or 2, wherein the intraosseous implant has a thickness of μm.