JPH041628B2 - - 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, the tooth may have to be extracted. In this case, a method such as britching 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).

Research is also underway into a treatment method that uses artificially synthesized hydroxyapatite, the main component of bone, as an implant. 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 between patients, a rejection reaction may occur on the living body's side, and in that case, the fibrous tissue develops into poor granulation, and if this is not possible, new bone formation is no longer possible. This is not expected and, as a result, complete fixation of the implant is not achieved.

Therefore, after a certain period of time has elapsed after implantation, we diagnose whether or not the implant is fixed to the bone, and if it is completely fixed (success), a crown is attached, and if poor granulation occurs (failure), we had to decide to have another surgery.

However, it seemed difficult to nondestructively diagnose whether implant fixation was successful or unsuccessful. 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, 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). The object of the present invention is to provide a dental diagnostic device that non-destructively diagnoses whether or not the tooth is attached (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 the 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 the experiment, they found that there is a correlation between the vibration frequency measured from the implant and the fixation status of the implant, as originally hypothesized. Based on this knowledge, the present inventors first developed an ultrasonic vibration source 1 that intermittently generates ultrasonic vibrations containing a wide range of frequency components from low frequencies to high frequencies; An ultrasonic vibration transmitting means 2 that transmits an ultrasonic vibration to the implant, and an ultrasonic vibration frequency measuring means 3 that measures the resonant frequency by contacting the implant. He invented a dental diagnostic device for diagnosing cancer and filed a patent application (Japanese Patent Application No. 58-232534).

According to the previous invention (Japanese Patent Application No. 58-232534), it is possible to non-destructively diagnose whether the implant has been successfully fixed by measuring the resonance frequency, but the present invention They improved the previous invention to make the diagnosis easier and created the present invention.

In other words, it has been empirically determined that the resonant frequency (f _p ) when successful is different from the resonant frequency ( _f It is easy to check the presence or absence of a resonance phenomenon at the resonance frequency (f _p or _f I was able to accomplish this.

Therefore, the present invention provides at least a predetermined resonance frequency (f)
an ultrasonic vibration source 1 that generates ultrasonic vibrations containing a component; an ultrasonic transmission means 2 that transmits the ultrasonic vibrations from the vibration source to the implant; The present invention provides a dental diagnostic device for diagnosing the fixation status of an implant based on the presence or absence of a resonance phenomenon at a predetermined frequency (f), which is characterized by comprising a detection means 3 for detecting the presence or absence of a resonance phenomenon.

In the present invention, the predetermined resonant frequency (f) means the resonant frequency (f _p ) when the implant fixation is successful or the resonant frequency (f _x ) when the implant fixation fails,
In the former case, it is determined whether the fixing is successful or not, and in the latter case, it is diagnosed whether the fixing is unsuccessful.

These predetermined resonance frequencies (f _p and _f Also check the resonant frequency (f _p ) when fixing is successful and the resonant frequency (f _x ) when fixing is unsuccessful.

As is well known per se, the vibration source 1 of the present invention is composed of various electric signal generating means 1a and an ultrasonic vibration oscillator 1b, and the oscillator 1b is composed of a piezoelectric element and a pair of electrodes sandwiching it. Become. When an electric signal is input to the oscillator 1b, ultrasonic vibrations consisting of various frequency (vibration frequency) components are generated depending on the waveform and input time.

In order to generate ultrasonic vibrations consisting of only a pure single frequency (f _p or f _x ), a sinusoidal electric signal of the same frequency (f _p or f _x ) is obtained from the generating means 1a and then transmitted to the oscillator 1b. You need to enter an infinite amount of time.

However, in reality, there are biological and temporal differences among patients, and f _p and f _x are distributed within a certain range, so it is difficult to specify f _p and f _x to a single value for a new patient. In many cases, it is not possible to do so, and after all, it can only be estimated that f _p and f _x are within a certain range.

Therefore, it is practical to use ultrasonic vibrations input to the implant that include frequency components in the band f _p ±Δf or f _x ±Δf'. In this case, a sine wave electric signal having a frequency of f _p or f _x is outputted from the generating means 1a for a period of Δt,
input to the oscillator 1b. The width of the band is the time △t
It can be changed by adjusting . In other words, increasing △t narrows the band; conversely, increasing △t
If you make it smaller, the band will be wider.

For example, here 100KHz to 150KHz (△t=50KHz)
If you want to obtain ultrasonic vibrations in the frequency band of 125K
Find the time Δt for providing a Hz sine wave electrical signal.
However, Δt is the half width.

From the Fourier transform formula, G(ω)=∫ ^∞ _-∞ g(t)・e ^j 〓 ^t・dt Here, when t<-△t/2, g(t)=0 −△t/2≦t≦ When Δt/2, g(t)=cosωot; When t>Δt/2, g(t)=0. Therefore, it is only necessary to integrate for −Δt/2≦t≦△t/2. Here, if ω=2πf and ω ₀ =2πfo, then G(f)=∫〓 ^t/2 〓 _t/2 cos2πfo t・e ^j2 〓 ^ft・dt G(f)=△t/2・sinπ△t (f−f _p )/π△t(f
-f _p )...(1) When f=f _p , G(f)=-Δt/2, so the half value is Δt/4.

Therefore, from equation (1), △t/2・sinπ△t(f−f _p )/π△t(f−f _p )
=△t/4...(2) Here, equation (2) is a transcendental equation, so when solved by numerical calculation, f≒f _p ±1.90/π△t...(3) From equation (3), half The price range △f is △f=f _p +1.90/π△t-(f _p -1.90/π△t) =2×1.90/π・△t ∴△=3.80/π・△f Here, △f= Since it is 50KHz, △t=3.80/3.14×50×10 ³ ≒24.2×10 ^-6 sec Therefore, if you want to obtain ultrasonic vibration in the frequency band of 100KHz to 150KHz with half width, use a 125KHz sine wave electrical signal. It is sufficient to input the signal to the oscillator 1b for 24.2 μsec.

In some cases, ultrasonic vibrations having frequency components f _p ±△f and f _x ±△f′ may be generated simultaneously or preferably at intervals of time and input into the implant; To obtain such vibrations,
Obtain the sinusoidal electrical signal of f _p and that of f _x from the generating means 1a at predetermined times, simultaneously or preferably at intervals of time, and transmit them to the oscillator 1b.
Just enter it in .

Furthermore, ultrasonic vibrations consisting of broadband frequency components may be used, and in order to obtain this vibration, the generation means 1
A pulsed electric signal having a rectangular wave or a waveform close to it is generated at step a, and only one pulse is input to the oscillator 1b.

In any case, in reality, the electrical signal input from the generating means 1a to the oscillator 1b is extremely short. Therefore, the ultrasonic vibrations generated by the oscillator 1b are also extremely short-lived, and even if a short-time ultrasonic vibration is input to the implant, the resonance phenomenon will eventually attenuate and disappear in a short time. There is no problem if the detection means 3 can still detect the resonance phenomenon, but such a detection means 3 requires more expensive equipment, and the detection means 3
In order to realize this at a low cost and to increase reliability, it is preferable to repeatedly generate the resonance phenomenon.

To do this, the electrical signal generated by the generating means 1a is repeatedly input to the oscillator 1b at certain intervals.

It is preferable to generate ultrasonic vibrations at certain intervals and input them to the implant than to continuously input ultrasonic vibrations to the implant for a long time. This is because, if the input is applied continuously for a long 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 b) the amplitude of the resonant vibration will gradually increase and eventually This is because the fixed state may be destroyed.

The ultrasonic vibrations thus 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 buried implants, the implant is covered with the gums and cannot be brought into direct contact with the 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 is not necessary to make it needle-shaped without implantation, since it can be directly touched, and it may be semi-spherical.

On the other hand, the detection means 3 that detects the presence or absence of a resonance phenomenon at a predetermined resonance frequency (f _p or f _x ) generally includes an ultrasonic probe 3 a that receives resonance vibration and converts it into a high-frequency electric signal; An amplifier 3b amplifies the converted high frequency electric signal as necessary, and a narrow band (f _p or f _x
A bandpass filter 3c that only passes the high-frequency electrical signal (corresponding to the above), a rectifier circuit 3d that converts the high-frequency electrical signal that has passed therethrough into a DC signal, and a rectifier circuit 3d that compares the intensity level of the DC electrical signal with a predetermined comparison level,
It consists of a comparator 3e that outputs an electrical signal when the level is higher than the comparison level, and a display means 3f that displays ON-OFF based on the output of the comparator. In this example, when the display means displays ON, it indicates that a resonance phenomenon has occurred at a predetermined frequency (f _p or f _x ), and when it does not display ON (i.e.
(when off) indicates that there was no resonance phenomenon. The processing of the electrical signals after 3b is not limited to this example, and various methods known in the field of electrical technology are possible.

In reality, simply checking for the presence or absence of a resonance phenomenon in either f _p or _f It is preferable to use a device that can oscillate vibrations in time series and detect the presence or absence of a resonance phenomenon. Furthermore, using an ultrasonic vibration source 1 containing both f _p and f _x components, the output from the amplifier 3b is
One bandpass filter 3C _p → rectifier circuit 3d _p → comparator 3e _p → display means 3f _p , and _the other bandpass filter 3C _x → rectifier _circuit 3d _x → comparator 3e _x → display means 3f _x , thereby leading to f _p
The presence or absence of a resonance phenomenon at f x and f _x may be simultaneously detected and displayed. In either case, when the resonance phenomenon is displayed as "absent", it indicates that the implant fixation is still at a premature stage where it cannot be determined whether it is successful (with f _p ) or failed (with f _x ). The display means 3f _p and 3f _x may be integrated to simply display one of "success", "failure", and "undetermined" by lighting. Further, instead of displaying "success", "failure", and "undetermined", a green, red, or yellow lamp may be lit.

In the previous explanation, the narrowband bandpass filter 3c was used on the receiving side, but the frequency of the ultrasonic vibration given to the implant was originally f _p ±△
If the frequency is limited to a narrow band of f or f _x ±△f' or f _p or f _x , resonance phenomena can only occur at those frequencies, so it is necessary to use the bandpass filter 3c on the receiving side. There isn't.

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

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.

The implant was then placed in the jawbone of an animal (dog). FIG. 3 is a conceptual diagram showing the state immediately after implantation, where the symbol G indicates the gingiva and the symbol C indicates the jawbone.

As a result of repeated animal experiments, we have found that when the implant is successfully fixed, resonant vibrations of 100 to 150 KHz are observed.
In case of failure, resonant vibrations between 20 and 50KHz are observed, and in cases where neither is determined yet, resonant vibrations between 50KHz and 100KHz are observed, and in this case, success (100 to 150KHz)
or failure (20-50KHz).

Therefore, when this implant is implanted in a laboratory animal, f _p = 100 to 150KHz or f _x = 20 to 50K
It should be Hz.

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, as shown in FIG.
A pulsed electrical signal is repeatedly generated having a pulse width T _p of 42 μsec., an amplitude A _p of 1 to 30 volts, and a pulse interval R _p of 0.6 msec. This electrical signal has a frequency spectrum as shown in FIG. 6, and includes various frequency components.

When such a pulsed electrical signal is transmitted to the oscillator 1b, the oscillator 1b contains a wide range of frequency components from low frequencies to high frequencies, as shown in FIG. Ultrasonic vibrations occur repeatedly every 0.6 msec.

The generated ultrasonic vibrations are transmitted to the implant by the vibration transmission means 2 adjacent to the oscillator 1b, causing the implant to resonate. The vibration transmission means 2 is
Here, a stainless steel needle with a diameter of about 1 mm and a length of about 30 mm is used.

On the other hand, as shown in FIG. 4, the resonance vibration of the implant is received by bringing the ultrasonic probe 3a into contact with the implant, and is converted into a high frequency electric signal. Since this electrical signal is very weak, the amplifier 3b
and amplify it 100 to 1000 times. Then, a band pass filter 3c passes only the frequency components of 100 to 150 KHz from the amplified high frequency electric signal.
The output is led to a rectifier circuit 3d and converted into a DC signal.

The converted DC signal is led to a comparator 3e, where the voltage level is compared with a comparison level. The comparison level is determined in advance based on a clinical investigation of the level when a resonance phenomenon occurs and the level when it does not occur.

This comparator 3e outputs an electrical signal when the input signal is higher than the noise level.
The output of 3e is guided to display means 3f. This display means 3f indicates "success" only when receiving the output of 3e.
Or a "blue" indicator lamp lights up.

When using the above device and the indicator lamp lights up, when we made an incision in the gums to expose the implant and touched it with our hands, we found that the implant was firmly fixed, and we pulled it out using dental pliers. I couldn't get over it. On the other hand, when the light did not light up and the implant was exposed and examined, it was found that either the implant was easily pulled out by hand and bad granulation was occurring, or the implant could not be pulled out by hand but could be pulled out with dental pliers. Ivy.

After repeating the experiment, it was found that there is a definite correspondence between the lighting of the indicator lamp and the success of implant fixation. Moreover, it was found that even if the diagnosis was made before complete fixation, no bone formation (that is, an obvious negative effect on complete fixation) was observed.

In the above explanation, the "probe 3a" was explained as a separate example from the "oscillator 1b and the vibration transmission means 2," but if the electric signal is processed appropriately, both can be combined. It is also possible to combine the functions into a single unit and have them function alternately in chronological order (a) or at the same time (b).

Further, although the display means 3f has been described as a visual display means, it is not limited to this, and may be an auditory or tactile display means, for example.

(Effects of the Invention) As described above, the present invention has made it possible for the first time to non-destructively and easily 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 the implant is implanted in the 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
FIG. 1 is a block diagram showing the overall configuration of a diagnostic device according to an embodiment of the present invention. FIG. 5 is an explanatory diagram of a pulsed electric signal. FIG. 6 is a frequency spectrum diagram of a pulsed electrical signal. FIG. 7 is a frequency spectrum diagram of ultrasonic vibrations applied to the implant. [Description of symbols of main parts], 1... Ultrasonic vibration generation source, 2... Ultrasonic vibration transmission means, 3... Resonant vibration detection means, 3a... Ultrasonic probe, 3b...
Amplifier, 3c... Bandpass filter, 3d...
... Rectifier circuit, 3e... Comparator, 3f...
Display means, a...implant, b...spring,
Ha, chi...jawbone, d...core body, ho...bioactive glass, he...indentation, g...gingiva.

Claims (1)

[Scope of Claims] 1. An ultrasonic vibration source 1 that generates ultrasonic vibration containing at least a predetermined resonance frequency (f) component, an ultrasonic transmission means 2 that transmits the ultrasonic vibration from the vibration source to an implant, and a detection means 3 for detecting the presence or absence of a resonance phenomenon at the predetermined resonance frequency (f) by contacting the implant; A dental diagnostic device that diagnoses the fixation status of 2. The dental diagnostic apparatus according to claim 1, wherein the predetermined resonance frequency (f) is a resonance vibration source (f _p ) when the implant is successfully fixed. 3. The dental diagnostic device according to claim 1, wherein the predetermined resonance frequency (f) is a resonance frequency (f _x ) when implant fixation fails.