JPH036815B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to the fixation status of a dental implant implanted in the jawbone when an artificial tooth is attached in place of the natural tooth when the natural tooth falls out. The present invention relates to a dental diagnostic device for non-destructively measuring (particularly bonding conditions).

(Background of the Invention) When tooth decay progresses too far, it may be necessary to extract the tooth, but in this case, a method such as a bridge is used to treat the tooth because there is no tooth root to support the crown. However, these treatments place an excessive load on the supporting natural teeth, eventually leading to a situation in which they also have to be extracted.

For this reason, research is being conducted on a treatment method in which an implant, also known as an artificial tooth root, is implanted and fixed in the jawbone, and an artificial tooth crown is attached on top of the implant. Recently, an implant made of alumina single crystal formed into a screw shape has been put into practical use.

However, in this case, the implant and the jawbone are simply connected by mechanical connection, and a clear interface exists between them. Therefore, the interface is susceptible to bacterial infection, and once infected, the implant must be removed.

In contrast to macro-mechanical bonding methods such as screw-shaped implants, implants are made of microporous materials such as sintered alumina, and bone naturally grows into the pores, resulting in the implant being micro-mechanical. Types of implants that attach to bone through a set of mechanical connections have also been investigated. After all, this type of implant also has a clear interface between the implant and the bone.

In response, bioactive glasses have been developed that chemically bond to bone, eliminating the existence of a clear interface. However, since glass alone has poor mechanical strength, research has been carried out on implants in which a metal core is coated with bioactive glass (Japanese Patent Application Laid-Open No. 118746-1982).
(see issue).

In addition, treatment methods using artificially synthesized hydroxyapatite, the main component of bone, as implants are being researched. The implant in this case is made of, for example, porous sintered apatite, and the new bone is directly bonded to this hydroxyapatite, so it is said to have high bonding strength and high biocompatibility.

In any case, when placing an implant, the jawbone is drilled with a drill, which causes damage to the bone. The bone then resorbs the surface bone in order to repair itself, and as a result, the implant becomes slightly loosened. After that, fibrous tissue is formed, bone cells work, hydroxyapatite is deposited, and new bone formation progresses. In this case, due to individual differences among patients, a rejection reaction may occur on the living body's side. In that case, the fibrous tissue develops into poor granulation, and once this occurs, new bone formation is no longer expected. As a result, complete fixation of the implant may not be achieved.

Therefore, we decided to diagnose whether the implant was fixed to the bone after a certain period of time after implantation, and if it was completely fixed, we would install a crown, and if bad granulation occurred, we would decide to undergo another surgery. Must.

However, it seemed difficult to diagnose at an early stage whether the implant was completely fixed. This is because it is important not to destroy the fixed state that has been completed by diagnosing with rough means, and it is impossible to confirm whether or not it is completely fixed by touching it with your hands. Furthermore, the commonly performed X-ray photography has not been able to diagnose cases except in cases of poor fixation where the defective granulation is extremely thick and developed.

(Object of the Invention) Therefore, the object of the present invention is to provide a method for fixing an implant implanted in the jawbone (in this specification, the term "fixing" is used as a result of chemically bonding with the bone like bioactive glass). It is an object of the present invention to provide a dental diagnostic device that non-destructively diagnoses the fixation status (meaning both the case where the tooth is attached and the case where it is fixed by mechanical coupling).

(Summary of the Invention) Ultrasonic diagnostic methods are available as a means of non-destructive measurement, but conventional ultrasonic diagnostic methods utilize the fact that the propagation speed of ultrasonic waves differs depending on the material.
We attempted to detect defective granulation using this ultrasonic diagnostic method, but
Ultrasound diagnosis through the bone was impossible because the attenuation of the ultrasound waves was too large.

Even though the attenuation is large, it is not desirable for the living body to input ultrasonic waves with large energy (amplitude) into the living body.

Therefore, the present inventors have conducted extensive research into a method that allows diagnosis even when inputting small-amplitude ultrasonic waves that do not affect the living body.

The present inventors assumed the state in which an implant is implanted in the jawbone as a model as shown in Fig. 1 (In Fig. 1, A is an implant, B is a spring,
Ha is the jawbone). In other words, when defective granulation occurred, the springero was considered to be quite soft, and when it was completely fixed, the springero was considered to be quite hard. In fact, defective granulation is rubber-like and can be considered a kind of spring.

If so, when ultrasonic vibration is applied to the implant toy, when the applied frequency matches the natural frequency of the vibration system consisting of the implant toy and springero, the vibration system resonates and the implant toy changes in amplitude. It should make a large vibration, and if the resonance phenomenon is used, even if a small amplitude vibration that does not affect the living body is applied, the amplitude of the resonance frequency will increase, so detection will be easy. Theoretically, the harder the springer is, the higher the resonance frequency will be, so we thought that the fixation situation could be diagnosed from the resonance frequency.

Therefore, the present inventors decided to prototype a test device and conduct animal experiments.However, when changing the frequency of the ultrasonic vibrations applied to the implant over time to observe the resonance phenomenon, the resonance frequency was detected. Since this process takes too much time, we decided to apply ultrasonic vibrations containing a wide range of frequency components from low to high frequencies to the implant. This is because even if a wide range of frequency components are input simultaneously, only the frequency component that matches the natural frequency will cause a resonance phenomenon and its amplitude will become large, while the other components have relatively small amplitudes, so the resonance vibration This is because only the number should be measured.

As a result of experiments, it was discovered that there is a correlation between the vibration frequency measured from the implant and the fixation state of the implant, and the inventors were convinced that the initial hypothesis was correct, leading to the creation of the present invention.

That is, the present invention provides an ultrasonic vibration source 1 that generates ultrasonic vibrations containing a wide range of frequency components from low frequencies to high frequencies, and an ultrasonic vibration transmission means that transmits the ultrasonic vibrations from the vibration source 1 to an implant. Provided is a dental diagnostic device for diagnosing the fixation status of an implant based on the resonant frequency, the device comprising: 2 and an ultrasonic vibration frequency measuring means 3 that measures the resonant frequency by contacting the implant. do.

Here, the ultrasonic vibration generation source 1 includes a pulsed electric signal generation means 1a and an ultrasonic vibration oscillator 1b.
The oscillator 1b consists of a piezoelectric element and a pair of electrodes sandwiching the piezoelectric element. When a pulsed electrical signal is input to the oscillator 1b, ultrasonic vibrations containing a wide range of frequency components from low frequencies to high frequencies are intermittently generated. The frequency spectrum of the ultrasonic vibration can be changed depending on the waveform of the pulsed electric signal, the characteristics of the piezoelectric element, etc.

If ultrasonic vibration is applied continuously for a long period of time, heat will be generated between the vibration transmission means 2 and the implant, which may have an unfavorable effect on the living body, and the vibration amplitude of the implant will gradually increase. Since there is a risk that the chemical bond between the implant and the jawbone may be destroyed, it is preferable to stop the implant within a relatively short period of time.

However, since the resonant vibrations caused by the applied ultrasonic vibrations attenuate in a relatively short time, in order to facilitate the measurement of the resonant frequency, relatively short-term ultrasonic vibrations are continuously repeated and applied to the implant. It is preferable. However, if the measured vibration waveform can be memorized by some means, the frequency can be determined from that waveform, so there is no need to repeatedly apply ultrasonic vibration to the implant.

Ultrasonic vibrations generated by the ultrasonic vibration source 1 are transmitted to the implant by the vibration transmission means 2. The transmission means 2 may be any rigid body that does not damp vibrations, and is usually made of metal. The shape is not particularly important, but since the implant is small, it is naturally limited. Particularly in the case of a buried type implant, the implant is covered with the gums and cannot be touched with a straight implant, so a needle shape that can penetrate the gums is preferable. On the other hand, in the case of an implant whose head protrudes from the gums, it can be touched in a straight line, so there is no need to force it into a needle shape, and it may be semispherical.

On the other hand, the ultrasonic frequency measuring means 3 receives ultrasonic vibrations from the implant and measures its frequency, and includes, for example, an ultrasonic probe 3a that receives the vibrations of the implant and converts them into electrical signals; an amplifier 3b that amplifies the electrical signal from the probe 3a;
and an oscilloscope 3c that displays the electrical signal amplified by the amplifier.

As is already well known, the ultrasonic probe 3a is sandwiched between a vibration transmitting part _3a1 and a pair of electrodes, which receives ultrasonic vibrations by contacting an implant, and transmits the ultrasonic vibrations to a piezoelectric element. It consists of a piezoelectric element _3a2 . In this case, the probe 3a is extremely small in order to faithfully pick up the vibrations received by the implant.
Need to be lighter. Like the vibration transmitting means 2, the vibration transmitting part _3a1 is preferably needle-shaped for an implant.

Ultrasonic vibrations received from the implant are converted into electrical signals by a probe 3a, and since this electrical signal is very weak, it is amplified by an amplifier 3b and then displayed on an oscilloscope 3c. Then, the period is read from the displayed waveform, and the resonant frequency f is calculated as the reciprocal of the period. Resonant frequency f from the waveform
Since it is troublesome to calculate f, a device that digitally displays the resonance frequency f may be assembled and used in place of the oscilloscope 3c.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

(Example) Figure 2 is a perspective view of the implant used in this example, with an upper diameter of 4.2 mm, a length of 9.0 mm, and a weight of 0.8 mm.
The thickness of the iron-based cobalt nickel alloy core body is
It is coated with 0.5mm bioactive glass foam.
This implant has a ``indentation'' for erecting a post core to which an artificial tooth crown will be attached. This implant is called Implant A.

On the other hand, for comparison, an implant B was prepared in which a core body of the same kind as the implant A was coated with bioinactive glass, which is known to easily cause defective granulation, to the same thickness as the implant A.

Implants A and B were then implanted into the jawbone of an animal (dog). FIG. 3 is a schematic diagram showing the state immediately after implantation, where the symbol G indicates the gingiva and the symbol C indicates the jawbone.

FIG. 4 is a block diagram showing the overall configuration of the diagnostic apparatus of this embodiment, and 1a is a pulsed electric signal generating means. As a result, a frequency spectrum as shown in Fig. 5, a pulse width (t) of 7 to 42 μsec., and a pulse width of 1 to 42 μsec.
A pulsed electrical signal is generated with an amplitude a of 30 volts and a pulse interval of 0.6 msec.

When such a pulsed electrical signal is transmitted to the oscillator 1b, the oscillator 1b intermittently (pulses) ultrasonic vibrations containing a wide range of frequency components from low frequencies to high frequencies, as shown in FIG. occurs in

The generated ultrasonic vibrations are transmitted to the implant by the vibration transmission means 2 adjacent to the oscillator 1b. The vibration transmitting means 2 here uses a stainless steel needle with a diameter of about 1 mm and a length of about 30 mm.

On the other hand, the frequency measuring means 3 consists of an ultrasonic probe 3a, an amplifier 3b, and an oscilloscope 3c, as shown in FIG. convert it into an electrical signal. Since this electrical signal is very weak, it is guided to the amplifier 3b and amplified 100 to 1000 times. Then, the amplified electric signal is displayed on the oscilloscope 3c, the period is read from the waveform, and the resonant frequency f is calculated from the reciprocal of the period.

When the implants A and B were measured immediately after implantation using the above-mentioned diagnostic device, f=about 120 kHz for both, and no difference was observed.

Then, 26 days after implantation, implants A and B were both covered with gums, so the vibration transmission means 2 and the probe 3a were penetrated from above the gums and brought into contact with the implants, and then the resonance vibration was applied. The number f was measured.

As a result, f = 100 kHz for implant A and f = 25 kHz for implant B, and a clear difference was observed between the two.

After that, when we made an incision in the gums to expose the implant and touched it with our hands, we found that implant A was firmly fixed and did not come out even when we pulled it with dental pliers, whereas implant B did not come out. It was easily pulled out by hand, and bad granulation had occurred between the implant B and the jawbone.

Further experiments showed that when the implant was completely fixed, f = 100 to 150 kHz, and when the implant was not fixed and bad granulation occurred, f = 20 to 50 kHz. If there is a clear difference in f and it is still in the process of being determined, the frequency f between 50 kHz and 100 kHz is measured, and in this case, it will eventually become completely fixed (f
= 100~150kHz) or formation of defective granulation (f = 20~
50kHz). Moreover, it was found that even if the diagnosis was made before complete fixation, there was no obvious negative effect on bone formation (that is, complete fixation).

Therefore, for implant A, f=100~
If a frequency of 150kHz is measured, it can be diagnosed that the implant is completely fixed in the jawbone.

(Effects of the Invention) As described above, the present invention has made it possible for the first time to non-destructively diagnose the state of fixation of an implant to the jawbone.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing, as a model, how an implant is implanted in a jawbone. FIG. 2 is a perspective view showing an example of an implant. FIG. 3 is a conceptual diagram illustrating the state immediately after the implant shown in FIG. 2 is implanted in the jawbone. Figure 4 shows
1 is a block diagram showing the overall configuration of a diagnostic device according to an embodiment of the present invention. FIG. 5 is a frequency spectrum diagram of a pulsed electrical signal. FIG. 6 is a frequency spectrum diagram of ultrasonic vibrations applied to the implant. Explanation of symbols of main parts, 1... Ultrasonic vibration generation source, 2... Ultrasonic vibration transmission means, 3... Frequency measuring means, A... Implant, B... Spring, C,
C...jawbone, D...core body, H...bioactive glass, H...indentation, T...gingiva.

Claims (1)

[Claims] 1. An ultrasonic vibration source 1 that generates ultrasonic vibrations containing a wide range of frequency components from low frequencies to high frequencies, and ultrasonic vibration transmission that transmits the ultrasonic vibrations from the vibration source 1 to an implant. 1. A dental diagnostic device for diagnosing the fixation status of an implant based on the resonance frequency, the device comprising: means 2; and ultrasonic vibration frequency measuring means 3 which measures the resonance frequency by contacting the implant. 2 The measuring means 3 is an ultrasonic probe 3 that receives ultrasonic vibration from the implant and converts it into an electrical signal.
a, an amplifier 3b for amplifying the electrical signal from the probe 3a, and an oscilloscope 3c for displaying the electrical signal amplified by the amplifier 3b. Diagnostic equipment.