JPS62164451A - Artificial dental root - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to the form of an artificial tooth root.

[Prior Art] Teeth are normally supported by a part of the bone called the alveolar bone, and perform mastication through the periodontal ligament and part of the gingiva.

When a tooth falls out or is extracted for some reason, the hole created by the extraction will fill with new bone over time.
At the same time, the margin progresses to regress, and in elderly patients, the floor of the jaw becomes flattened. Dental implants are the idea of implanting a non-biotoxic substance into the jawbone in the area where the tooth is missing, and making it easier to masticate and function in place of the natural tooth. It is also expected to play a role in mitigating bone degeneration.

Conventionally, artificial tooth roots implanted in the jawbone have undergone various changes in materials and forms, mainly metal materials, but due to the biotoxicity of metals, many ceramic materials such as polycrystalline alumina have been developed. . However, from the viewpoint of strength and biocompatibility, artificial tooth roots made of alumina and artificial tooth roots made of apatite sintered glass are currently mainstream. Next, these two types of artificial tooth roots will be explained.

As shown in FIG.
2 is formed and physically fixed by screwing into a hole drilled in the jawbone 13. Because the material has high mechanical strength, the outer diameter of the artificial tooth root can be made thinner, and the range of applications is wide. It is a characteristic of Furthermore, when implanted in a living body, it is chemically stable and has excellent biocompatibility. However, since this material does not adhere to the bone, a method of fixing it within the bone using a screw structure as shown in FIG. 5A is used. Also,
Because no bonding occurs with the bone, stress may be concentrated on a portion of the bone depending on the shape of the artificial tooth root, potentially causing bone regression. On the other hand, an artificial tooth root made of abatite has a form as shown in FIG. That is, several protrusions 19 are provided above and below the periphery of the columnar main body 18, and chamfers 20 for preventing rotation are formed at several locations in the generatrix direction. Such an artificial tooth root made of apatite has the characteristic that it directly adheres to the bone when implanted into the body, and therefore does not require a particular screw structure.

[Problems to be Solved by the Invention] In the case of an artificial tooth root made of alumina, a screw structure is required as already mentioned. These screws, as shown in FIG. 5A, have a similar design to general industrial screws. However, it is not easy to insert screws with such a fine pitch into the jawbone.

The hardness of a human jawbone varies significantly depending on the person's constitution, age, medical history, etc., but in general it has the same hardness as soft wood. Therefore, it is fine if it enters the bone tightly as shown in Figure 5 △, but if the artificial tooth root rotates further after reaching the bottom of the hole 14 as shown in Figure 5 B, the screw thread on the bone side will collapse and become fixed. It becomes impossible. Conversely, if a gap 15 remains at the bottom as shown in Figure 5C, a large force is applied to the bone during mastication, resulting in the artificial tooth root falling out. Such failures are particularly likely to occur when the bone is soft, but another major cause is that the threads of the artificial tooth root are small and the pitch is small, so the surgery requires great skill. Furthermore, since this artificial tooth root does not adhere to the bone and does not have a special rotation prevention mechanism, the crown (upper structure 16) fixed on the artificial tooth root is connected to the adjacent tooth 17 as shown in Fig. 6. There is a need. On this occasion,! Since healthy teeth need to be removed, the lifespan of the teeth may be shortened.

On the other hand, in the case of an artificial tooth root made of apatite, the diameter of the artificial tooth root becomes large because the mechanical strength of the material is not sufficient. Therefore, a major drawback is that it can only be applied clinically to patients with a sufficiently wide alveolar bone. In the case of an artificial tooth root made by Avatile 1, it has a shape as shown in Fig. 7. The surgery is performed by drilling a hole 21 in the alveolar bone and implanting the artificial tooth root as shown in Figure 8. However, in the early stages of implantation, it is difficult to securely fix the artificial tooth root within the bone because it does not have a screw structure. , it is necessary to accurately drill a hole with a diameter slightly smaller than the diameter of the artificial tooth root.

In actual surgery, the machine's shaft shakes and the surgeon's hands shake, which can occur, and requires a great deal of skill. This initial fixation after surgery is particularly important as it has a significant impact on the success rate of surgery. In addition, the upper structure (crown) cannot be created until the alveolar bone and artificial tooth root are bonded and completely fixed after surgery.
Another major drawback is that it requires several months. This invention was made in order to eliminate the above-mentioned drawbacks of artificial tooth roots currently on the market, and mainly to improve the shape of artificial tooth roots that are easy to operate on and that function quickly after surgery. is intended to provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention is characterized in that threads with a pitch of 2 mm or more are formed on the circumferential surface of the tooth root body. In addition, a screw is formed in which the height and width of the screw thread gradually decrease toward the tip of the main body. Furthermore, the tooth root body is not limited to having an equal diameter, but may be a conical shape whose diameter is slightly reduced toward the tip of the body.

[Function] The threads on the main body of the artificial tooth root have a relatively coarse pitch of 2 mm or more, rather than the conventional fine pitch, so when the artificial tooth root is inserted, the screws on the bone side Mountains are prevented from collapsing. In addition, the threads of the screw become thinner and lower toward the tip, so the deeper the screw goes into the alveolar bone, the more firmly it is fixed to the bone.

[Example] Fig. 1 is a front view of the artificial tooth root of the present invention, Fig. 2 is a left side view, and Fig. 3 is a right side view.

A thread 2 is formed on the circumferential surface of the tooth root body 1 at the tip of the main body (the height and width of the thread gradually decrease toward the left in FIG. 1. The pitch of the thread is 2 mm or more, preferably 3 mm). ~
It should be about 4mm. The shape of the screw thread is not limited to a semicircular cross section as shown in FIG. 1, but may be trapezoidal as shown in FIG. 4, or triangular or quadrangular (not shown). The tip of the main body 1 has a groove or unevenness 3 for preventing rotation, and a chamfer near the other end surface to make it easier to grip and rotate the artificial tooth root when the artificial tooth root is inserted into the bone. It has 4. The grooves and irregularities have a depth of about 7 mm, and their cross-sectional shapes are semicircular, triangular, trapezoidal, etc., and can be formed as a single line or as a review book. In addition, the main body 1 is not only shaped like a column with the same diameter, but also has a diameter that decreases toward the tip as shown in Figure 4.
It may also have a conical shape with an angle θ.

Note that the shape of the artificial tooth root according to the present invention is not limited to the shape described in the above embodiments. For example, a screw may be attached not only one turn but also several turns. In addition, it is generally desirable that the cross-section of the thread is not square, but if it is triangular or square, it is sufficient to round the corners of the thread.

The above-mentioned artificial tooth root can be obtained by a general method employed for molding ceramics using glass powder, such as pressure molding with a mold, slurry casting, extrusion molding, and isostatic pressing. Various methods can also be applied to sintering and crystallizing the glass powder compact. The crystallized glass obtained here contains a large amount of apatite crystals, which are necessary for chemically bonding with bone, and has high strength. As an example, its composition, sintering treatment, precipitated crystals, etc. are shown below.

Composition (wt% lt'lo 19.9, C, a O28
, 0, Si 02 32.0, P2O5 15,6, ZrQ24.0, Others F2 0.5 Heating rate: 3°C/min Holding temperature, time: 1020°C, 2 hours Precipitated crystals: apatite, diopside, foliar Stellite bending strength: 2100km Cll12Next, the features of the present invention will be explained in detail.

As mentioned above, it is important to completely fix the artificial tooth root so that it does not move during the period after the artificial tooth root is implanted until the new bone is covered around the tooth root.
This is an important factor in determining failure. In order to facilitate such initial fixation, it is desirable that the root body of the artificial tooth has a screw structure. In the present invention, in order to prevent the front thread from collapsing during implantation of the artificial tooth root, the pitch of the thread is made very large as shown in FIGS. 1 and 4.

This is also effective in reducing the number of rotations of the tooth root required for implantation and in making it easier to determine whether the bottom of the artificial tooth root has accurately entered the alveolar bone formation.

In addition, the screw thread of screw 2 becomes thinner and lower as it goes to the bottom of the artificial tooth root.This is aimed at the effect that the deeper the artificial tooth root goes into the alveolar bone, the more firmly it will be fixed in the bone. This makes good use of the elasticity of the bone.With this type of screw structure, even if the accuracy of drilling into the bone is poor, the tapered screw part can firmly fix the artificial tooth root within the bone. is possible, making surgery easier.Also, by making the screw thread larger,
It is possible to disperse stress that is concentrated at the bottom of the artificial tooth root to the sides of the artificial tooth root. This can prevent bone regression caused by stress concentration at the bottom.

Note that a groove 3 is provided on the distal end surface of the main body 1, and this groove is for preventing the implanted artificial tooth root from loosening due to rotation. When an artificial tooth root with such a groove is implanted, the groove is filled with new bone over time, which has the effect of preventing rotation of the artificial tooth root.

[Effects of the Invention] As described above, according to the present invention, by providing a special screw structure, reliable fixation is possible even if the accuracy of drilling during surgery is considerably poor, and the operator's skill is not required. do not. It also prevents the front screw thread from collapsing, which tends to occur during implantation.

Furthermore, since the initial fixation after surgery can be performed reliably, it is possible to increase the success rate of surgery. As a result, a superstructure such as a dental crown can be prepared at an early stage, thereby reducing the burden on the patient. As mentioned above, surgery to reconstruct masticatory function using artificial tooth roots is currently extremely difficult and has many failures, and is only performed in a limited number of hospitals. The artificial tooth root according to the present invention can make surgery easier and can be useful for widely popularizing surgery using artificial tooth roots.

[Brief explanation of drawings]

Figure 1 is a front view of the artificial tooth root of the present invention, Figure 2 is a left side view,
Figure 3 is a right side view, Figure 4 is a front view of another embodiment of the present invention, and Figures 5, △, B, and C are cross-sectional views of conventional alumina artificial tooth roots embedded in alveolar bone. , Fig. 6 is a side view of the tooth crown fixed to the artificial tooth root shown in Fig. 5, Fig. 7 is a front view of the conventional artificial tooth root made of apatite, and Fig. 8 is the implanted state of the artificial tooth root shown in Fig. 7. FIG. 1... Main body of the artificial tooth root, 2... Screw, 3... Groove. Applicant: Hoya Co., Ltd. Representative: Tadashi Asakura Notes to the drawings (no changes to the contents) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Procedural amendments (Self-restraint March 4, 1986

Claims (1)

[Claims] 1. An artificial tooth root characterized by having screws with a pitch of 2 mm or more formed on the circumferential surface of the tooth root body. 2. The artificial tooth root according to claim 1, wherein the screw thread gradually decreases in height and/or width toward the tip of the tooth root body. 3. The artificial tooth root according to claim 1, wherein the tooth root body has a conical shape whose diameter is reduced toward the tip of the main body.