JP3450944B2 - Artificial root - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an artificial tooth root for implanting a jaw bone for mounting a denture. 2. Description of the Related Art Conventionally, it has been already possible to implant an artificial root at a site where a small number of teeth or a large number of teeth are missing, and attach an artificial tooth (denture) to an upper portion thereof to substitute for a natural tooth. It has many clinical applications. Metals such as titanium, cobalt-chromium, and molybdenum alloys and ceramics such as alumina ceramics are used as this type of implant material. [0003] As a method of contacting an artificial tooth root, first, a mucosa of a tooth defect part or an extraction socket is peeled off, a groove or a screw hole corresponding to the shape of the artificial tooth root is formed in a jaw bone, and a fixture is implanted. A healing cap is placed on the screw hole to keep the screw hole closed, the mucous membrane is covered, and the fixture is held in this state. After a certain period of time,
After peeling off the mucous membrane, removing the healing cap, performing work such as impression to make a denture, fix the abutment on the upper part of the fixture via the abutment screw, and the gingiva stabilizes on the abutment surface In general, a method of implanting a post on the upper portion of an abutment and placing a denture on the post after the post is brought into close contact with the abutment has been generalized. Japanese Patent Application Laid-Open No. Hei 7-23983 describes an invention relating to an artificial tooth root of this type. According to the artificial tooth root, the artificial tooth root is formed at a lower end of a holder as an abutment with respect to a base as a fixture. The screw is fitted. At this time, the sleeve inserted between the screw and the base and tapered to the wall surface of the hole of the base is pulled downward, so that the upper end of the base located around the hole is outward. Push open. It is described that this increases the adhesive force at the link surface between the base and the holder to be tapered. [0005] However, the above prior art has the following problems. That is, in the above-mentioned conventional artificial tooth root, the taper connection between the sleeve and the hole wall surface of the base and the upper end portion of the base are plastically deformed, so that a relatively strong connection is possible. The looseness occurs between the base and the base, and a minute gap also occurs at the link surface between the holder and the base, and there is a possibility that bacteria may propagate in the gap or cause a problem such as loose teeth. . SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and therefore, the fixing force between the fixture and the abutment hardly decreases even after long-term use, and therefore, the two members can be used. An object of the present invention is to provide a safe artificial tooth root that does not generate a minute gap at a joint surface. [0007] In order to solve the above-mentioned problems of the prior art, the artificial dental implant of the present invention is provided on a substantially cylindrical fixture to be implanted in the jawbone and coaxially with the fixture. An artificial dental root for installing an abutment, projecting the abutment from the gingiva into the oral cavity, and implanting a denture post therein, wherein the fixture includes the fixture, the abutment, An internal screw is drilled below the hollow bottomed hole extending in the axial direction from the upper end surface to screw the abutment screw that secures the abutment screw, and the abutment has a head of the abutment screw and An inner screw for passing the screw portion of the abutment screw into the lower end portion of the hollow through hole extending axially from the upper end surface to be engaged with the inside of the fixture. The abutment screw is further provided with a tapered surface having an inclination of 10 ° to 45 ° on the lower surface of the head. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an artificial tooth root according to the present invention, which is connected on a fixture 3 having a self-tapping external screw 2 formed on the lower outer peripheral surface so as to be embedded and fixed in the jaw bone. The abutment 6 is fixed via an abutment screw 5 having a large-diameter head portion 4 for use in implanting a denture above the abutment 6. As shown in the sectional view of FIG. 2, the substantially cylindrical fixture 3 constituting the artificial tooth root 1 has an upper end surface 7.
A hollow bottomed hole 8 extending in a stepwise manner in the axial direction is formed at the lower portion 9 of the small diameter of the hollow bottomed hole 8 and an internal screw 10 is formed to screw the abutment screw 5. Can be combined. Further, the intermediate portion 11 of the hollow bottomed hole 8 has a flat regular hexagonal shape as shown in FIG. 3, and has a shape in which the lower end of the abutment 6 can be fitted non-rotatably. Further, the large-diameter upper portion of the hollow bottomed hole 8 is adapted to fit with the lower portion of the abutment 6. The abutment 6 has a substantially cylindrical shape, as shown in FIG. A hollow through-hole 15 is formed in the axial direction from the upper end surface 14, and the small-diameter lower end of the abutment 6 is fitted into the fixture 3.
This hollow through-hole 15 is the hollow bottomed hole 8 of the fixture 3.
Is configured to be continuous. At the same time, an inner screw 16 is formed at the lower end of the hollow through hole 15 as shown in FIG. 4. In the case of a blind hole, the diameter of the hole is slightly larger than the outer diameter of the thread of the abutment screw 5. In contrast to this, the diameter of the hole can be made slightly larger than the outer shape of the thread root, and the thickness of this portion is ensured. Further, the avatarment screw 5
4, the outer periphery of the lower end is formed with a taper angle α = 10 ° to 45 ° as shown in FIG. 4, and the tapered surface is formed in the hollow through hole of the avatar in a taper angle β = 52. Engage with a 0.5 degree internal thread 16. The material of each member is titanium alloy, pure titanium, cobalt chromium alloy,
Although it is preferable to be composed of a metal alloy such as molybdenum, the surface is partially composed of a ceramic material having excellent biocompatibility such as hydroxyapatite or alumina ceramic, or is partially or wholly substituted for metal. It may be made of a biocompatible polymer material. [0012] The artificial tooth root 1 thus configured is
By forming the inner screw 16 at the lower end of the hollow through hole 15 formed in the abutment 6, the thickness of the lower end of the abutment 6 can be secured, so that the strength is great. Lower surface is taper angle α
= 10 ° to 45 °, and the inner screw 16 is configured to engage with the inner screw 16, so that the inner screw 16 undergoes large plastic deformation and engages with a very strong fastening force. The sticking force between the char 3 and the abutment 6 is also very large, and a serious problem of loosening between them can be avoided. When the taper angle α of the lower surface of the head 4 of the abutment screw 5 is less than 10 °, the fixing force between the fixture 3 and the abutment 6 may be considerably reduced with long-term use. There is. On the other hand,
Even when the taper angle α is larger than 45 °, there is a possibility that the fixing force between the fixture 3 and the abutment 6 becomes considerably small with long-term use. Experimental Example The following experiment was conducted using the artificial dental implant made of the titanium alloy shown in FIG. In the experiment, a set of five arbitrary fixtures was used, and connection was made with a heavy-duty resin at intervals of about 1 cm. The rotation angle of the fixture was kept unchanged from the start to the end of the experiment (FIG. 5). [Materials used] Fixture: 25 abutments: 25 abutment screws, 15 ° half-angle taper class 2 screws: 5, 30 ° half-angle taper class 1 screws: 5, 30 ° half-angle taper class 2 screws : Five 45 ° half-angle tapered class 2 screws: Five 90 ° half-angle class 2 screws: Five abutment screws were incorporated into the abutment, and the fixture was temporarily fixed. Using a commercially available torque meter, 750 gf · cm for the first to fifth times,
The screw was tightened at 1,000 gf · cm from the sixth to the tenth time. At this time, tightening was performed at a constant speed until reaching each torque value, and the predetermined torque value was maintained for 5 seconds. When the mounting of the abutment was completed on all the fixtures in the set of five, the loosening torque (T) was measured using the same torque meter. As the loosening torque, the maximum torque value at the time when the screw was clearly loosened was adopted, and when a slippage or the like was observed during the course, this was recorded. At the same time, a pointer was attached to the torque meter, and the rotation position at which the first to tenth predetermined tightening torque values could be maintained was recorded on paper set perpendicular to the long axis of the fixture. The angle between the corner markings entangled from the center position of the fixture was actually measured and defined as a tightening angle (θ) (FIG. 6). A) Loosening torque FIG. 7 and Table 1 show the average of the loosening torque experimental results for each number of experiments. [Table 1] In the graph of FIG. 7, the horizontal axis indicates the number of tightenings, and the vertical axis indicates the loosening torque (gf · cm). 7 for the 1st to 5th
Tighten at 50gf · cm and 1,000 for the 6th to 10th time
The loosening torque is increased from the fifth to sixth times because of tightening with gf · cm. No remarkable rise is seen within the same tightening torque range, but 1 to 15 in the 15 ° taper group.
At the fifth time (750 gf · cm), a slightly slow rise is observed. When tightening at 750 gf.cm for the fifth time, the loosening torque was increased every time when the taper angle was 15 °. In addition, 1,000gfcm
When tightened at 90 °, those with a 30 ° taper angle showed the same tendency as the previous experimental value for both Class 1 and Class 2 equivalent screws.
The value of the taper angle (flat screw) also fluctuated in the same manner as the previous time, and the average torque value (〜700 gf · cm) was changed. The overall trend seen in FIG. 7 and Table 1 is 15 °, 3 °
In the case of a 0 ° screw, the variation in data gradually decreases with each increase in the number of experiments, while in the case of a 90 ° screw, even with a tightening of 1,000 gf · cm, ± 100 gf · cm
There are two points where the above variation is observed and that the torque other than the 15 ° screw shows a decrease in the loosening torque after the second (sixth) tightening at 750 gf · cm. B) Additional tightening angle FIGS. 8 and 9 show the relationship between the loosening torque of the abutment screw having a taper angle and the additional tightening angle. FIG. 8 shows the number of tightening on the horizontal axis and the actually measured additional tightening angle (θ) on the vertical axis, and FIG. 7 shows the number of tightening on the horizontal axis and the cumulative (Θ) of the actually measured additional tightening angle on the vertical axis. Show. Tighten at 750 gf · cm by the first to fifth times, 6-1
Until the 0th time, it was tightened with 1,000gfcm,
The change in the rotation angle from the fifth to the sixth rotation is large. A slight saturation tendency is seen within the same tightening torque range.
The tightening up to the 0th time did not result in a completely parallel state. As shown in FIG. 9, from the first time to the second time,
The tightening angle has been maximized with the tightening from the sixth to the sixth time. Further, as shown in FIG. 9, it can be seen that the rotation of the screw in the 90 ° group is gradually stopped by the tenth tightening. C) Regarding the relationship between the additional tightening angle and the loosening torque Here, the correlation between the additional tightening angle and the generated loosening torque will be examined. If there is a strong correlation, it means that the tightened amount is converted into the fastening force by applying the taper. FIG. 10 shows the relationship between each additional tightening angle and the increment from the previous loosening torque, that is, the n-th additional tightening angle (θn) and the n-th torque (Tn) − [n
−1] shows the relationship of the first loosening torque (Tn−1) = τn. From these observations, the following regression equation was obtained. Τ = 9.76 (± 0.99) θ−27.00 (± 8,26); (n = 200) The t value is 9.85, which indicates a considerably high correlation. According to the formula, 9.76 ± 0.99gf ・ c every time the 1 ° screw is tightened
It is shown that the fastening force increases by m. For reference, FIGS. 11 to 14 show distribution charts divided for each taper angle group. As described above, in the artificial dental implant of the present invention, an abutment is provided on a substantially cylindrical fixture to be embedded in the jawbone and coaxially with the fixture. An artificial root for projecting a dental implant from the gingiva into the oral cavity and implanting a post for a denture into the dental implant. An internal screw is drilled below the hollow bottomed hole extending in the axial direction from the upper end surface so as to fit therewith, and the abutment has a shaft from the upper end surface to engage with the head of the abutment screw. In the lower end portion of the hollow through hole extending in the direction, an internal screw for passing the screw portion of the abutment screw is bored separately from the internal screw of the fixture, and The abutment screw has a lower surface of 10
Because it was a tapered surface with a slope of ° ~ 45 °,
The thickness of the lower end of the abutment can be ensured, so the strength is large, the inner screw is plastically deformed greatly, and the two are engaged with a very strong fastening force, so the fixing force between the fixture and the abutment is also very high This is an excellent effect that a serious problem of looseness between the two can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an artificial root according to an embodiment of the present invention. FIG. 2 is a sectional view of a fixture constituting the artificial tooth root of FIG. FIG. 3 is a top view of a fixture constituting the artificial tooth root of FIG. 1; FIG. 4 is an enlarged view of a portion A in FIG. FIG. 5 is a schematic diagram showing a method for fixing a sample in an experimental example. FIG. 6 is a schematic diagram for explaining an experimental procedure. FIG. 7 is a graph showing the results of averaging the experimental results of the loosening torque for each number of experiments. FIG. 8 is a graph showing the relationship between the number of experiments and the tightening angle θ. FIG. 9 is a graph showing the relationship between the number of experiments and the tightening angle Θ. FIG. 10 is a graph showing a relationship between a loosening torque and a tightening angle. FIG. 11 is a graph showing the relationship between additional tightening angles in the case of a 15 ° taper. FIG. 12 is a graph showing the relationship between additional tightening angles in the case of a 30 ° taper. FIG. 13 is a graph showing the relationship between additional tightening angles in the case of a 45 ° taper. FIG. 14 is a graph showing the relationship between additional tightening angles in the case of a 90 ° taper. [Explanation of Signs] α, β Taper angle C Denture 1 Artificial tooth 2 External screw 3 Fixture 4 Head 5 Abutment screw 6 Abutment 7, 14 Upper end face 8 Hollow bottomed hole 9 Lower parts 10, 16 Internal screw 11 Intermediate part 12 Upper part 15 Hollow through hole 17 Lower part

────────────────────────────────────────────────── ─── of the front page continued (56) references US Patent 5435723 (US, a) (58 ) investigated the field (Int.Cl. ^7, DB name) A61C 8/00

Claims (1)

(57) [Claims 1] An abutment is installed coaxially with the fixture on a substantially cylindrical fixture to be implanted in the jawbone, and the abutment is moved from the gingiva to the oral cavity. An artificial tooth root for projecting a post for a denture into this is protruded from the upper end surface to screw an abutment screw for fixing the fixture and the abutment to the fixture. An internal screw is drilled below the hollow bottomed hole extending in the axial direction, and the abutment has a hollow extending in the axial direction from the upper end surface to engage with the head of the abutment screw. Pass the screw part of the abutment screw through the lower end of the through hole
Separate the internal screw for fixing from the internal screw of the fixture
And then the abutment screw is
An artificial tooth root, wherein the lower surface of the head is a tapered surface having an inclination of 10 ° to 45 °.