JPH053885A - Dental implant - Google Patents

Abstract

PURPOSE:To absorb excessive occlusion force with a stress buffer member and to prevent the damage of the jaw bone by interposing the stress buffer member consisting of a superelastic member between an artificial tooth root part to be embedded into the jaw bone and a post part to be mounted with an artificial tooth. CONSTITUTION:The artificial tooth root part consisting of an artificial tooth root body 3a made of titanium and a gingival tissue penetrating member 4 is implanted into the jaw bone (alveolar bone) 1. The gingiva 2 is clad to the upper part of the tooth root body 3a. The post 6 mounted with the artificial tooth 8 made of a resin is fixed to the upper part of the superelastic member made of an Ni-Ti alloy by using a screw 11 for fixing the artificial tooth and thereafter, the gap in the upper part of the screw 11 for fixing the artificial tooth is filled with a sealing member 12 made of a resin. Namely, the superelastic member 7 is interposed between the artificial tooth root parts 3a, 4 and the post 6. The damage of the jaw bone 1 is prevented in this way even if the excessive occlusion force is loaded thereon. Namely, the occlusion force is absorbed by deforming the superelastic member 7 as against the excessive occlusion force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of artificial dental roots (dental implants) used in dentistry.

[0002]

2. Description of the Related Art In recent years, as a prosthetic means for treating detachment and damage of teeth, the technique of implanting artificial roots has been actively researched. This technique is to implant an artificial root having a function similar to that of the original natural tooth at the detached position of the tooth or the extracted position of the damaged tooth.

As conventional artificial tooth roots, those made of titanium or titanium alloy and those made of alumina single crystal are widely used. Also, in order to increase the affinity with bones,
An artificial dental root made of titanium or a titanium alloy, in which the contact surface with bone is coated with hydroxyapatite (HAP) or calcium phosphate (TCP), has also been proposed. But,
Most of these conventional artificial tooth roots do not have a function equivalent to the periodontal ligament of a natural tooth, particularly, a shock absorbing function.

FIG. 12 shows an example of such a conventional artificial tooth root. In the figure, 3 is an artificial dental root main body made of titanium, which is embedded in the jawbone 1 as shown. A gingival tissue penetrating member 4 made of titanium is fitted to the upper end of the artificial tooth root body 3. Reference numeral 10 denotes a titanium post core, which penetrates the gingival tissue penetrating member 4 and is screwed into a post core fixing hole formed in the artificial tooth root body 3. The artificial tooth 8 is fixed on the post core 10 via the artificial tooth fixing pin 11. In addition, artificial pin 11
The upper void is filled with the encapsulating member 12. In a dental implant having no stress buffering mechanism as described above, the impact during occlusion may directly act on the jawbone 1 and damage the jawbone 1.

Therefore, in order to obtain the stress buffering effect, Japanese Patent Laid-Open No. 58-116353 discloses a shock buffering member provided between the crown and the outer crown. In addition, JP-A-62-38148
In No. 3, a polymer member such as silicone rubber or polyoxymethylene is provided between the tooth root receiver (artificial tooth root body) and the tooth root body (post core), so that the impact force applied to the crown can be reduced by the polymer member. A shock absorbing dental implant is disclosed.

FIG. 13 shows an example thereof. As shown,
In this example, a titanium-made artificial tooth root main body 3 implanted in the jawbone 1 has a cylindrical gingival tissue penetrating member 4 made of titanium.
Are fitted together. The gingival tissue penetrating member 4 is fixed by screwing a polymer member 5b such as polyoxymethylene from above. An artificial fixing pin 1 for fixing the artificial tooth 8 is provided in the upper center of the gingival tissue penetrating member 4.
A screw hole for screwing 1 is provided. Artificial teeth 8
Is fixed to the gingival tissue penetrating member 4 via the artificial tooth fixing pin 11. The space of the artificial tooth 8 located above the artificial tooth fixing pin 11 is filled with the encapsulating member 12. However, the structure using the impact absorbing member made of the above polymer material has the following problems. The first problem is
Since the deformation of the polymer material is large, the movement of the crown is larger than necessary and sufficient occlusal force cannot be obtained. The second problem is to avoid deterioration and breakage of polymeric materials.
That is, the shock absorbing member must be replaced regularly.

In order to solve these problems, as shown in FIG. 14, a dental implant in which the polymer member 5c is prevented from deterioration by making the polymer member a disk-shaped member 5c has been proposed. . In this conventional example,
The disk-shaped polymer member 5c made of polyoxymethylene is
It is placed on the titanium gingival tissue penetrating member 4 screwed and fixed to the titanium artificial tooth root body 3. The artificial tooth 8 is fixed by screwing the artificial tooth fixing pin 11 onto the gingival tissue penetrating member 4. As a result, the disk 5c is fixed in a state of being sandwiched between the gingival tissue penetrating member 4 and the artificial tooth 8.

In the dental implant of FIG. 14, the occlusal force applied to the artificial tooth 8 is borne by the artificial tooth fixing pin 11, so that the stress generated in the disk-shaped polymer member 5c can be reduced. However, in the dental implant having the disk-shaped polymer member 5c, the polymer member 5
Since stress concentrates on the neck of the artificial tooth fixing pin 11 that fixes c, permanent strain remains on the artificial tooth fixing pin 11 and the occlusal position is misaligned.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. An object of the present invention is to improve the impact absorbing member while avoiding applying excessive stress to the jawbone and It is an object of the present invention to provide an artificial dental root that can obtain a sufficient occlusal force and does not require replacement of the shock absorbing member.

[0010]

In order to solve the above problems, in the present invention, as a stress buffering mechanism, at least a part between the artificial tooth root body and the artificial tooth, or between the artificial tooth root body and the post portion is provided. At least a part is provided with a stress buffering device made of a super elastic member or a stress buffering device made of a polymer member and a super elastic member.

When a stress buffering device composed of a polymer member and a superelastic member is used, the superelastic member should directly connect the artificial tooth root main body and the artificial tooth, or the artificial tooth root main body and the post portion without interposing the polymer member. Is located in. The polymer member is designed to be arranged, for example, in a region sandwiched between the superelastic member, the gum tissue penetrating member, and the post portion.

As the superelastic material in the present invention, a shape memory alloy whose reverse transformation temperature is slightly lower than the oral temperature can be used. Here, a temperature slightly lower than the oral temperature is more specifically 35 ° C or less, preferably 20 to 25 ° C.
Of temperature. Examples of such shape memory alloys include:
For example, the following may be mentioned.・ Ni-Ti alloy (eg 48-52 at% Ni, balance T
i) ・ Ni-Ti- Cu alloy (for example, 49.5 at% Ti, 40.5 at
at% Ni, 10 at% Cu) ・ Ni-Al alloy (for example, 36-38 at% Al, balance N)
i) ・ Ni-Ti-Co alloy (for example, 31-33 at% Ni, 5-
15 at% Co, 3.5-5 at% Ti, balance Fe) -Cu-Zn alloy (for example, 38.5-41.5 wt% Zn, balance Cu) -Ti-Mo-Al alloy (for example, 80-87 at% Ti, 13
-15 at% Mo, 0-5 at% Al) Of these, the Ni-Ti alloy is particularly preferable.

The stress-elongation curve of an alloy having a shape memory effect is as shown in FIG. 1 at a temperature slightly higher than its reverse transformation temperature. This stress-elongation curve shows superelasticity, which is one of the characteristics of shape memory alloys. That is,
When the stress is released and the elastic region is exceeded, the strain returns to almost zero when the stress is released. On the other hand, in ordinary metals, as is clear from the stress-elongation curve in FIG. 2, after the stress exceeds the elastic deformation region, the strain does not return to zero even if the stress is released, and a permanent strain remains.

As the polymer member in the present invention, a material which is not harmful to the living body and has a large vibration damping rate, for example, polyoxymethylene, nylon 6, nylon 66, nylon 46, teflon, silicone or the like is used.

[0015]

In the present invention, the shock absorbing member made of a super elastic material provided on at least a part between the artificial tooth root main body and the artificial tooth or at least a part between the artificial tooth root main body and the post portion is as follows. Acts like.

First, when the stress applied during occlusion is within the elastic deformation region of the superelastic member, the stress applied to the upper structure (artificial tooth) is firmly received by the root portion via the superelastic member. Therefore, sufficient occlusal force can be obtained.

On the other hand, when the stress applied during occlusion exceeds the elastic deformation region of the superelastic member, the superelastic member is largely deformed by plastic deformation and absorbs the occlusal force to avoid an increase in stress. Therefore, by designing the yield stress of the superelastic member so that the stress acting on the jawbone around the artificial tooth root body does not exceed the breaking strength of the jawbone, it is possible to prevent the jawbone from being damaged by an excessive occlusal force.

Even after the strain exceeding the elastic region is given, if the large occlusal force applied at that time is unloaded, the deformation of the superelastic member is restored. Therefore, the permanent set does not remain and the occlusal position does not change as in the case of ordinary metal. Further, since the shape memory alloy used as the superelastic material has an excellent vibration damping effect due to the presence of the martensite twin, it has a great effect of damping the impact. Further, by using the shape memory alloy designed such that the reverse transformation temperature is lower than the temperature in the oral cavity, the durability is improved as compared with the stress buffering member made of a polymer material. In addition, when the stress buffering device including the polymer member and the super elastic member is provided, the following action is obtained.

First, when an impact force is applied, the polymer member functions to damp the vibration, so that the impact force that damages the jaw bone can be absorbed and the jaw bone can be protected.

Since the superelastic member and the polymer member are combined, the normal occlusal stress is borne by the superelastic member.
Therefore, the polymer member does not generate a large stress that causes a fire and breakage of the polymer member, as compared with the conventional stress buffering mechanism using only the polymer member such as polyoxymethylene. Therefore, it is not necessary to replace the polymer member for a long period of time.

[0021]

EXAMPLES The present invention will be described below based on examples.

FIG. 3 is a cheek-lingual cross-sectional view showing the artificial dental root according to the first embodiment of the present invention in a state of being implanted in an affected area. In the figure, 1 is a jaw bone (alveolar bone), and 2 is a gingiva. In the jawbone 1, artificial dental root parts 3a and 4 made of titanium are implanted. The artificial tooth root portion of this embodiment includes an artificial tooth root body 3a and a gingival tissue penetrating member 4. At a portion deeper than 2 mm below the bone surface of the artificial tooth root body 3a, a coating film containing β-TCP as a main component is provided on the surface in contact with the jawbone 1. The coating film promotes early osseointegration of the artificial dental root main body 3a implanted in the jawbone 1, so that the artificial dental root main body 3a is firmly fixed to the jawbone 1 without intervening fibrous tissue. In the actual operation, the tooth root body 3a
After being planted in the jawbone 1, the screw hole provided on the upper part of the tooth root main body 3a is closed with a Teflon lid, and the gingiva 2 is completely covered on the screw hole while taking care not to damage the periosteum.

After the artificial tooth root body 3a is fixed by osseointegration with the alveolar bone 1, the gingiva is opened and the Teflon lid is removed. Subsequently, an artificial tooth root part is formed by fitting or adhering the titanium-made gingival tissue penetrating member 4 having a cylindrical shape to the artificial tooth root body 3a. And
48-52 at% Ni / 52 whose reverse transformation temperature is designed to be 20 ℃ to 25 ℃
The superelastic member 7 made of -48 at% Ti alloy is fixed by screwing it onto the artificial tooth root parts 3 and 4 from above.

Further, the post 6 to which the artificial tooth 8 made of resin is adhered is fixed to the upper portion of the Ni-Ti alloy superelastic member 7 using the artificial tooth fixing screw 11, and then the upper void of the artificial tooth fixing screw is made. Fill with the resin encapsulation member 12.

As in the above embodiment, the artificial tooth roots 3a, 4
With the structure in which the super elastic member 7 is disposed between the post 6 and the post 6, the alveolar bone 1 can be prevented from being damaged even when an excessive occlusal force is applied. That is, the super-elastic member 7 is largely deformed beyond the elastic region by the excessive occlusal force and absorbs the occlusal force. Therefore, no stress that damages the alveolar bone 1 is applied to the alveolar bone 1. Therefore, stable bone fixation of the artificial root can be obtained for a long period of time. Further, since the Ni-Ti alloy superelastic member 7 is less deteriorated and damaged than the conventional shock absorbing member made of a polymer material such as POM,
No need to replace for a long time.

The shape and fixing method of the artificial tooth root body 3a, the gingival tissue penetrating member 4, the superelastic member 7, and the post 6 are not necessarily limited to the above. For example, in FIG.
As shown in, the artificial tooth root main body 3a, the gingival tissue penetrating member 4, the superelastic member 7, and the post 6 may be fixed by screwing. Further, as shown in FIG. 5, a disc-shaped superelastic member 7 having a through hole in the center may be screwed and fixed to the gingival tissue penetrating member 4 with a screw provided on the post 6. .

Further, although the artificial tooth roots 3a and 4 made of titanium are used in the above embodiment, it is also possible to use a titanium alloy or a ceramic such as zirconia.

FIG. 6 is a cheek-lingual cross-sectional view showing an artificial tooth root according to a second embodiment of the present invention in a state of being implanted in an affected area. In this embodiment, a blade type artificial tooth root body 3 is used. The artificial tooth root body 3 that can be placed in this embodiment has a structure that also serves as the gingival tissue penetrating member 4 of FIG. In the figure, the same members as those in the embodiment of FIG. 1 are shown with the same reference numerals.

Blade-type titanium artificial tooth root body 3
Is embedded in the alveolar bone 1 so that the portion having screw holes for constructing the upper structure is located above the gingiva 2.
Then, after the blade type artificial tooth root body 3 is firmly fixed in the alveolar bone 1, an upper structure is constructed. That is, the superelastic member 7 made of Ti-Ni is screwed into the artificial tooth root body 3, and the post 6 is screwed and fixed thereon. continue,
The dental cement 9 is used to bond the bridge artificial tooth 8 to the post 6 and the adjacent tooth.

Also in the embodiment of the blade type implant as described above, the same effect as that of the embodiment of FIG. 3 is obtained by adopting the structure in which the superelastic member 7 is arranged between the tooth root body 3 and the post 6. be able to. That is, when an excessive occlusal force is applied, the artificial tooth root is largely deformed beyond the elastic region of the superelastic member 7 and absorbs the occlusal force, so that the artificial dental root is extended for a long period of time without damaging the alveolar bone. Can be operated. Furthermore, since the Ti-Ni superelastic member is less deteriorated and damaged, there is an advantage that it does not need to be replaced for a long period of time.

FIG. 7 is a sectional view showing a main part of an artificial tooth root according to the third embodiment of the present invention. In this example, Ni
A part of the surface of the Ti superelastic member 7 exposed in the oral cavity and a part of the surface covered with the posts 6 are covered with a pure titanium thin film 13. The superelastic member 7 made of Ni-Ti is designed so that its reverse transformation temperature is slightly lower than the oral temperature. In addition, the pure titanium thin film 13
Are designed so thin that they do not impair the stress-strain characteristics of the superelastic member 7. Other configurations are the same as those of the embodiment shown in FIG.

Also in the third embodiment, the action of the superelastic member 7 prevents the alveolar bone from being damaged even when an excessive occlusal force acts. In addition, since the surface of the superelastic member 7 exposed in the oral cavity is covered with the pure titanium thin film 13, the elution of metal ions from the Ni-Ti alloy can be suppressed to a low level and the safety can be improved. You can Further, since the upper end portion and the lower end portion of the pure titanium thin film 13 are fixed by the post 6 and the gingival tissue penetrating member 4, the pure titanium thin film 13 is prevented from falling off.

FIG. 8 is a sectional view showing the main part of an artificial tooth root according to the fourth embodiment of the present invention. In this example, Ni
A portion of the surface of the Ti superelastic member 7 exposed in the oral cavity is coated with Teflon coating 14. Other configurations are the same as those of the embodiment shown in FIG.

According to this embodiment, it is possible to further suppress the elution of metal from the superelastic member 7 while maintaining the characteristics of the superelastic member 7, and to further improve the safety. Instead of Teflon coating 14,
A coating made of a polymer material that is not harmful to the body such as polyethylene and nylon may be used, and the same effect can be obtained in this case as well.

In the third and fourth embodiments, FIG.
The artificial titanium root is provided with the pure titanium thin film 13 or the coating 14 such as Teflon, but the same effect can be obtained when the same means is applied to the artificial root of FIGS.

FIG. 9 is a cheek-lingual cross-sectional view showing a fifth embodiment of the present invention. The jawbone 1 has a titanium artificial tooth root body 3a.
Has been planted. Jaw bone 1 of titanium artificial tooth root body 3a
A coating film containing β-TCP as a main component is provided below 2 mm below the bone surface in contact with the jawbone 1.
Promotes early osseointegration of the artificial tooth root body 3a implanted in the. Therefore, the titanium artificial dental root main body 3a is firmly fixed to the jawbone 1 without intervening fibrous tissue. In the actual surgical method, after implanting the titanium artificial tooth root body 3a in the jawbone 1,
The screw hole for constructing the superstructure provided on the upper part of the artificial tooth root body 3a is closed by using a Teflon lid, and while being careful not to damage the periosteum, the upper part is completely covered with the gingiva 2 and the osseointegration is performed. Then, the artificial dental root main body 3a made of titanium is rested until it is fixed to the jawbone 1.

After the titanium artificial tooth root body 3a is fixed by osseointegration with the jawbone 1, the gingiva is opened to remove the Teflon lid, and the titanium-made gingival tissue penetrating member 4 having a cylindrical shape is attached to the titanium artificial tooth root. It is fitted or adhered to the main body 3a. The superelastic member 7 made of Ni-Ti alloy, which is designed to have a reverse transformation temperature slightly lower than the temperature in the oral cavity, for example, 20 ° C., via the polymer member 5 made of nylon 66 and the titanium post portion 6, The nylon 66 polymer member 5 and the titanium post portion 6 are fixed by screwing the titanium artificial tooth root body 3a from above.

In this embodiment, the outer diameter of the nylon 66 polymer member 5 is composed of at least two portions which are equal to the outer diameter and the inner diameter of the gingival tissue penetrating member 4, respectively. A portion equal to the inner diameter of the gingival tissue penetrating member 4 penetrates along the inner surface of the gingival tissue penetrating member 4, and the bottom surface thereof reaches the artificial tooth root body 3a. Further, a hole through which the super elastic member 7 penetrates is provided on the central axis of the nylon 66 polymer member 5. Further, the artificial tooth 8 is bonded to the post portion 6 constructed on the titanium artificial dental root main body 3a as described above with the dental cement (adhesive layer 9).

As in the above embodiment, a stress buffer consisting of the super elastic member 7 and the polymer member 5 is arranged between the titanium artificial tooth root body 3a and the post portion 6 to which the artificial tooth 8 is bonded. With this structure, when an excessive occlusal force is applied, the superelastic member 7 is largely deformed beyond the elastic region and absorbs the occlusal force. Therefore, the jawbone 1 is not subjected to an excessive stress that damages the jawbone. Therefore, stable bone fixation of the dental implant can be obtained over a long period of time. In addition, the super elastic member 7 made of Ni-Ti alloy
The strain causes a strain of several% due to the stress load, and even after the strain exceeds the elastic region, the strain returns to almost zero when the stress is released.Therefore, it is different from those using ordinary metals such as titanium and titanium alloys. Differently, the occlusal position does not change.

Further, as a result of combining the superelastic member 7 made of Ni-Ti alloy and the polymer member 5 made of nylon 66, the normal occlusal stress is borne by the superelastic member 5 made of Ni-Ti alloy. Therefore, the polymer member 5 made of nylon 66 does not generate a large stress that causes a fire or breakage of the polymer member, as compared with the conventional stress buffering mechanism of only the polymer member 5b such as polyoxymethylene. . Therefore, it is not necessary to replace the polymer member 5 for a long period of time.

The shape and fixing method of the stress buffering device composed of the super elastic member 7 and the polymer member 5 are not necessarily limited to the above. For example, as shown in FIG. 10, the post portion 6 is screwed and fixed to the super elastic member 7, and the gingival tissue penetrating member is provided from above the polymer member 5 along the through hole provided in the polymer member 5. It may be screwed and fixed to the artificial dental root main body 3b integrated with.

Further, as shown in FIG. 11, a gingival tissue penetrating member 4b having a screw hole for screwing and fixing the artificial tooth fixing pin 11 on the upper portion is screwed and fixed to the artificial tooth root body 3a. May be In this example, a hole for the superelastic member 7 to pass through on the central axis and a trapezoidal post portion 6 are formed.
The polymer member 5a provided with is used. The polymer member 5a and the artificial tooth 8 having a lower shape that is in contact with the shape of the post portion 6 without a gap are placed on the gingival tissue penetrating member 4b, and the artificial tooth 8 and the polymer member 5a are sandwiched from above. As described above, the artificial tooth fixing pin 11 is screwed and fixed to the gingival tissue penetrating member 4b. After that, the space of the artificial tooth 8 existing above the artificial tooth fixing pin 11 is filled with the enclosing member 12.

[0043]

As described above in detail, according to the artificial tooth root of the present invention, necessary and sufficient occlusal force can be obtained, and damage to the alveolar bone can be prevented even when an excessive occlusal force is applied. In addition, it is possible to obtain remarkable effects such as no need to replace the shock absorbing member.

[Brief description of drawings]

FIG. 1 is a stress-strain curve showing superelasticity of a shape memory alloy.

FIG. 2 is a stress-strain curve of an ordinary metallic material.

FIG. 3 is a cheek-lingual cross-sectional view showing the artificial dental root according to the first embodiment of the present invention in a state of being implanted in an affected area.

FIG. 4 is a sectional view showing a modification of the embodiment shown in FIG.

5 is a sectional view showing another modification of the embodiment shown in FIG.

FIG. 6 is a cheek-lingual cross-sectional view showing an artificial tooth root according to a second embodiment of the present invention in a state of being implanted in an affected area.

FIG. 7 is a cross-sectional view showing a main part of an artificial tooth root according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a main part of an artificial tooth root according to a fourth embodiment of the present invention.

FIG. 9 is a sectional view showing an artificial dental root according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view showing a modification of the fifth embodiment of the present invention.

FIG. 11 is a sectional view showing another modification of the fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view showing an example of a conventional artificial tooth root.

FIG. 13 is a cross-sectional view showing another example of a conventional artificial tooth root.

FIG. 14 is a sectional view showing still another example of a conventional artificial tooth root.

[Explanation of symbols]

1 ... Alveolar bone, 2 ... Gum, 3a, 3b, 3 ... Artificial tooth root body, 4, 4b ... Gingival tissue penetrating member, 5a, 5b, 5c ...
Polymer member, 6 ... Post, 7 ... Super elastic member, 8 ... Artificial tooth, 9 ... Dental cement, 11 ... Artificial tooth fixing screw, 12
… Resin encapsulation member, 13… Pure titanium thin film, 14… Teflon coating

Claims (10)

[Claims] 1. A dental implant having an artificial tooth root part to be embedded in a jawbone and a post part to which an artificial tooth is attached, wherein a stress made of a superelastic material is present in at least a part between the artificial tooth root part and the post part. A dental implant provided with a cushioning member. 2. The artificial tooth root part is an artificial tooth root main body part,
The dental implant according to claim 1, comprising a gingival tissue penetrating portion. 3. The dental implant according to claim 1, wherein the stress buffering member is made of a superelastic material and a polymer material provided at least partially in contact with the superelastic material. 4. A stress buffering member composed of a superelastic member and a polymer material, wherein the superelastic member is in direct contact with at least a part of the artificial tooth root body portion and the post portion, and the polymer material is the superelastic member. The dental implant according to claim 2, which is provided so as to contact at least a part of a side surface portion of the member. 5. The dental implant according to claim 2, wherein the polymer material forms a trapezoidal post portion. 6. The superelastic material is a shape memory alloy whose reverse transformation temperature is lower than the temperature in the oral cavity.
The dental implant according to item 1. 7. The dental implant according to claim 6, wherein the shape memory alloy has a reverse transformation temperature of 35 ° C. or lower, preferably 20 to 25 ° C. 8. The dental implant according to claim 6, wherein the shape memory alloy is a Ni—Ti alloy. 9. The dental implant according to claim 8, wherein at least a portion of the stress buffering member made of the Ni—Ti alloy that is exposed in the oral cavity is covered with a material having low biotoxicity. 10. The bio-hazard-free material comprises a thin film of a metal with a low bio-hazard such as pure titanium, or a polymer material with a low bio-hazard such as Teflon, polyethylene or nylon. Dental implant.